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Lithuania-Poland Workshop on
Physics and Technology
Book of Abstracts
September 26-27, 2019
Vilnius, Lithuania
2
Center for Physical Sciences and Technology
Savanorių ave. 231, LT-02300 Vilnius, Lithuania
www.ftmc.lt
ISBN 978-609-95511-6-6
http://lithpol2019.ftmc.lt/
© Center for Physical Sciences and Technology, 2019
3
Contents
Contents ...................................................................................................................................... 3
Committees .................................................................................................................................. 4
Welcome Address ........................................................................................................................ 5
Programme .................................................................................................................................. 6
List of oral presentations .............................................................................................................. 7
List of poster presentations .......................................................................................................... 9
Oral presentations ...................................................................................................................... 11
Poster presentations .................................................................................................................. 38
Organizer and Partner ............................................................................................................... 65
Sponsors .................................................................................................................................... 65
Supporters ................................................................................................................................. 65
4
Committees SCIENTIFIC COMMITTEE
Gintaras Valušis (Chair from Lithuania)
Arūnas Krotkus
Vidmantas Gulbinas
Leonas Valkūnas
Jerzy Łusakowski (Chair from Poland)
Marek Samoć
Jacek Ulański
Stanisław Krukowski
Łukasz Kłopotowski
ORGANIZING COMMITTEE
Renata Karpicz (Chair)
Renata Butkutė
Domas Jokubauskis
Simona Pūkienė
Mažena Mackoit Sinkevičienė
5
Welcome Address
Dear Guests,
Dear Colleagues,
Dear Friends!
On a behalf of the Organizing Committee and the Center for Physical Sciences and Technology
we would like to welcome you here at the Lithuania-Poland workshop LithPol 2019 in Vilnius,
Lithuania.
The year of 2019, involving an important date – the 450th Anniversary of the Union of Lublin –
encouraged us to organize a scientific workshop of our neighbouring countries. The event intends
not only to broaden frontiers of the scientific cooperation, but it is also intends to enrich topics of
project applications and open new dimensions in confluence of expertise. The event aims to find
more items which will unite and stimulate us solving problems as well as enrich and complement
us uplifting our neighbourhood.
We are deeply grateful to all of our partners, sponsors and supporters for making this workshop
possible. We highly express highest possible appreciations for all the participants for their
contributions and sharing of scientific experience.
We wish you interesting scientific discussions and profitable exchange of knowledge as well as
pleasant stay in beautiful city of Vilnius.
Gintaras Valušis, Workshop Chair
6
Programme
9:00 – 10:15 9:00 – 10:50
9:00-9:15 Opening Ceremony 9:00 - 9:30 Darius Abramavičius (Lithuania)
9:15 – 9:45 Rimvydas Petrauskas (historical; Lithuania) 9:30 - 10:00 Bozena Sikora (Poland)
10:00 - 10:30 Voitech Stankevic (Lithuania)
9:45 – 10:15 Concert 10:30 – 10:50 Janusz Sadowski (Poland)
10:15 - 11:30 10:50 – 11:15
10:15-11:30 Photo and Short Excursion Valdovų rūmai 10:50 – 11:15 Coffee break
11:30 - 12:00 11:15 – 13:05
11:30-12:00 Coffee break 11:15 – 11:45 Tomasz Kazimierczuk (Poland)
12:00 - 13:00 11:45 – 12:15 Evaldas Naujalis (Lithuania)
12:00 - 12:30 Vidmantas Gulbinas (Lithuania) 12:15 – 12:45 Jacek Szczytko (Poland)
12:30 - 13:00 Adam Babiński (Poland) 12:45 – 13:05 Mantas Marčinskas (Lithuania)
13:00 - 14:00 13:05 – 14:00
13:00 - 14:00 Lunch 13:05 - 14:00 Lunch
14:00 – 15:50 14:00 – 15:30
14:00 - 14:30 Beata Luszczynska (Poland)
14:30 - 15:00 Irmantas Kašalynas (Lithuania)
15:00 - 15:30 Wlodzimierz Lewandowski (Poland) 15:30 – 16:00
15:30 – 15:50 Genrik Mordas (Lithuania) 15:30 – 16:00 Coffee break15:50 - 16:15 16:00 – 17:30
15:50 - 16:15 Coffee break 16:00 – 16:20 Agnieszka Siemion (Poland)
16:15 – 18:05 16:20 – 16:40 Ernestas Kasparavičius (Lithuania)
16:15 - 16:45 Linas Vilčiauskas (Lithuania) 16:40 – 17:00 Maksim Dub (Poland)
16:45 - 17:15 Marcin Szalkowski (Poland) 17:00 – 17:20 Mažena Mackoit-Sinkevičienė (Lithuania)
17:15 - 17:45 Ramūnas Aleksiejūnas (Lithuania) 17:20 – 17:30 Closing remarks
17:45 - 18:05 Justyna Grzelak (Poland)
18:15 – 21:00
18:15 - 21:00 Conference dinner
Lithuania-Poland Workshop on Physics and Technology TimetableSeptember 26, Thursday September 27, Friday
National Museum – Palace of the Grand Dukes of Lithuania,
Katedros a. 4, Vilnius
Center for Physical Sciences and Technology,
Saulėtekio av. 3, Vilnius
14:00 – 15:30 Poster Session
VENUE VENUE
The 450th Anniversary of the Union of Lublin
7
List of oral presentations O01 Charge carrier generation and motion in methylamonium lead iodide
perovskite films
Vidmantas Gulbinas
12
O02 Resonant Raman Scattering in the few-layer Transition Metal Dichalcogenides
Adam Babinski
13
O03 Organic bulk heterojunction photovoltaics and photodetectors
Beata Luszczynska, Marek Zdzislaw Szymanski, Tomasz Klab
14
O04 New methods of in-situ patterning of OLED emission area.
Amruth C, Wassima Rekab, Beata Luszczynska and Jacek Ulanski
15
O05 AlGaN/GaN heterostructures for plasma wave instabilities in THz regime
Irmantas Kašalynas and Maciej Sakowicz
16
O06 Polish Metrology - 100 years of progress
Włodzimierz Lewandowski
17
O07 High-Definition Laser Metal Deposition
Genrik Mordas, Ada Steponavičiūtė, Karolis Stravinskas, Sergejus Borodinas
18
O08 Molecular Modeling of Electrochemical Interfaces for Energy Conversion
S. K. Stauffer, L. Vilčiauskas
19
O09 Plasmon enhancement of performance of photosystem I based biomimetic graphene solar cells
Marcin Szalkowski, Dorota Kowalska, Ersan Harputlu, Małgorzata Kiliszek, C. Gokhan Unlu, Kamil Wiwatowski, Kasim Ocakoglu, Joanna Kargul, and Sebastian Maćkowski
20
O10 Mobility of charge carriers in organic-inorganic perovskites
Ramūnas Aleksiejūnas, Patric Ščajev, and Saulius Juršėnas
21
O11 Enhancement of infrared optical response of organic polymers in hybrid nanostructures
Justyna Grzelak, Aneta Prymaczek, Marcin Nyk, Maciej Ćwierzona, Dawid Piątkowski and Sebastian Maćkowski
22
O12 Quantum theory of multiscale relaxation dynamics in molecular aggregates
Darius Abramavicius
23
O13 Biofunctionalized multifunctional nanoconstructs based upconverting NaYF4 doped rare earth and magnetic Fe3O4 nanoparticles for theranostic applications.
Bożena Sikora, Przemysław Kowalik, Anna Borodziuk, Izabela Kamińska, Jakub Mikulski, Karolina Zajdel, Magdalena Duda, Krzysztof Fronc, Paulina Grzączkowska, Malwina Szczęsna, Jarosław Rybusinski, Jacek Szczytko, Roman Minikayev, Tomasz Wojciechowski, Kamil Sobczak, Magdalena Kulpa-Greszta, Robert Pązik, Małgorzata Frontczak-Baniewicz, Łukasz Kłopotowski
24
8
O14 Magnetic field sensors for high-pulsed magnetic field measurements.
V. Stankevič, N. Žurauskienė, S. Balevičius, S. Keršulis, V. Plausinaitienė
26
O15 MoTe2 thin films and nanostructures grown by molecular beam epitaxy
Janusz Sadowski, Bartłomiej Seredyński, Zuzanna Ogorzałek, Marta Gryglas-Borysiewicz, Sławomir Kret and Wojciech Pacuski
27
O16 Optical spectroscopy of CdSe/ZnSe quantum dots with single Fe2+ ions
T. Kazimierczuk, T. Smoleński, A. Rodek, J. Kobak, M. Goryca, W. Pacuski, A. Golnik, P. Kossacki
28
O17 Development of National Metrology System and the Ways for International Cooperation
Evaldas Naujalis
29
O18 Towards Bose-Einstein condensation of exciton polaritons at room temperature: tunable liquid crystal microcavities
J. Szczytko, K. Lekenta, M. Król, R. Mirek, R. Mazur, P. Morawiak, P. Kula, W. Piecek, M. Matuszewski, W. Bardyszewski, P. G. Lagoudakis, B. Piętka
31
O19 Synthesis and investigation of new organometallic semiconductors containing dimethoxydiphenylamine-substituted carbazole fragments
Mantas Marčinskas, Tadas Malinauskas
33
O20 Optimized terahertz diffractive optical element for skin cancer diagnosis
Mateusz Surma, Paweł Komorowski, Izabela Ducin, Piotr Sobotka, Elżbieta Czerwińska, Michał Walczakowski and Agnieszka Siemion
34
O21 Oxidized SPIRO-MEOTAD stability investigation
E. Kasparavičius, T. Malinauskas, V. Getautis
35
O22 Optimization of AlGaN/GaN EdgeFETs for terahertz detection by optimization of ohmic contacts.
M. Dub, M. Sakowicz, P. Sai, D. B. But, P. Prystawko, G. Cywiński, S. Rumyantsev, W. Knap
36
O23 Carbon dimer defect as the origin of the 4.1 eV luminescence in hexagonal boron nitride
Mažena Mackoit-Sinkevičienė, Marek Maciaszek, Chris G. Van de Walle, Audrius Alkauskas
37
9
List of poster presentations
P01 Bismide technology for temperature independent IR range semiconductor laser diodes
Simona Pūkienė, Jan Devenson, Vladimir Agafonov, Algirdas Jasinskas, Bronislovas Čechavičius, Karolis Stašys, Renata Butkutė
39
P02 Reactive magnetron sputtering of scandium oxide films for various applications.
Alexandr Belosludtsev, Robert Mroczyński, Naglis Kyžas, Lukas Ceizaris, Yuri Yakimov, Sandra Stanionytė, Martynas Skapas, Kęstutis Juškevičius
40
P03 Reflectivity of the n-type GaN with shallow surface gratings
Vytautas Janonis, Pawel Prystawko, Krzysztof Gibasiewicz, Jacek Kacperski, Irmantas Kašalynas
41
P04 Modeling of pump-probe spectra at high excitation intensity
Vytautas Bubilaitis, Darius Abramavičius
42
P05 Terahertz pulse emission from GaInAsBi
R. Norkus, V. Pačebutas, S. Stanionytė, A. Bičiūnas, A. Urbanowicz and A. Krotkus
43
P06 Photophysical properties of dimethildihydropyrene derivatives
Ignas Čiplys, Irena Kulszewicz-Bajer, Renata Karpicz
44
P07 Performance of the Planar AlGaN/GaN Bow-Tie Diodes Developed for Terahertz Detection
Justinas Jorudas, Liudvikas Subačius, Gintaras Valušis, and Irmantas Kašalynas
45
P08 Mechanical Properties of 17-4PH Stainless Steel Parts Produced by DMLS
Ada Steponavičiūtė, Aušra Selskienė, Jurijus Tretjakovas, Genrik Mordas
46
P09 Modeling of Molecular Excitation Relaxation in Thermal Environment by Time-dependent Variational Approach with Superposition of Davydov D2 Ansätze
Mantas Jakučionis, Darius Abramavičius
47
P10 New Fluorene-Based Hole Transporting Organic Semiconductors for Efficient Hybrid Solar Cells
Aistė Ilčiukaitė, Marytė Daškevičienė, Egidijus Kamarauskas, Vygintas Jankauskas, Vytautas Getautis
48
P11 Peculiarities of laser-processed photonic crystal-based waveguides for terahertz and sub-terahertz frequencies
Vincas Tamošiūnas, Simonas Indrišiūnas, Linas Minkevičius, Gediminas Račiukaitis, Irmantas Kašalynas and Gintaras Valušis
49
P12 p-Type Fluorene-Based Organic Semiconductors for Efficient Perovskite Solar Cells
Šarūnė Daškevičiūtė, Nobuya Sakai, Marius Franckevičius, Marytė Daškevičienė, Artiom Magomedov, Egidijus Kamarauskas, Vygintas Jankauskas, Henry Snaith, Vytautas Getautis
50
10
P13 Development of AlGaN cladding layer for GaN second harmonic generation structure
Marek Kolenda, Darius Kezys, Arūnas Kadys, Tadas Malinauskas, Raimondas Petruškevičius and Roland Tomašiūnas
51
P14 Synthesis and investigation of new organic semiconductors containing 1,4,5,8-naphthalenetetracarboxylic diimide central fragment
Lauryna Monika Svirskaitė, Ernestas Kasparavičius, Tadas Malinauskas
52
P15 AlGaN/GaN/SiC high-electron-mobility transistors and Schottky diodes
Vytautas Jakštas, Justina Malakauskaitė, Justinas Jorudas, Vytautas Janonis, Linas Minkevičius and Irmantas Kašalynas
53
P16 Comparison of AlGaN/GaN HEMT and silicon nMOS terahertz detectors with the same length of the gate
Juozas Vyšniauskas and Alvydas Lisauskas
54
P17 In vitro studies for the assessment of bio-nano interactions
Karolina Zajdel, Bożena Sikora, Przemysław Kowalik, Izabela Kamińska, Małgorzata Frontczak-Baniewicz
55
P18 AIII-BV Quantum Structures for NIR Emitters
Algirdas Jasinskas, Simona Pūkienė, Sandra Stanionytė, Martynas Skapas, Bronislovas Čechavičius, and Renata Butkutė
57
P19 Photoelectrochemical generation of active chlorine species at sol-gel derived nanostructured WO3 electrode
Maliha Parvin, Milda Petrulevičienė, Irena Savickaja, Benjaminas Šebeka, Arnas Naujokaitis, Vidas Pakštas and Jurga Juodkazytė
58
P20 Magnetoplasma Excitation in Double CdTe/CdMgTe Quantum Wells
D. Yavorskiy, M. Szoła, K. Karpierz, I. Własny, D. Śnieżek, P. Nowicki, J. Wróbel, S. Chusnutdinow, G. Karczewski, T. Wojtowicz, and J. Łusakowski
59
P21 Changes of Boron Nitride Luminescence as a Result of X-Ray Irradiation
M. Szoła, M. Tokarczyk, G. Kowalski, J. Binder, K. Pakuła, A. Dąbrowska, A. Wysmołek, and J. Łusakowski
60
P22 Interaction between magnetohydrodynamic and temperature instabilities during S-N switching of thin II-type superconductor films.
Linas Ardaravičius, Oleg Kiprijanovič
61
P23 Design and fabrication of THz torch device containing Ga(As,Bi)/AlGaAs parabolic quantum well in active region for THz emission
Mindaugas Karaliūnas, Justas Pagalys, Vytautas Jakštas, Jan Devenson, Simona Pūkienė, Renata Butkutė, Andres Udal, and Gintaras Valušis
62
P24 Thick objects imaging using compact phase shifting elements designed for 0.6 THz
L. Minkevičius, D. Jokubauskis, V. L. Paukštė, S. Indrišiūnas, I. Kašalynas, S. Orlovas, A. Urbas, and G. Valušis
63
P25 Effect of Molecular Beam Epitaxy Growth Conditions for Terahertz Sensing InGaAs Diodes
Domas Jokubauskis, Renata Butkutė, Linas Minkevičius
64
11
Oral presentations
12
O01
Charge carrier generation and motion in methylamonium
lead iodide perovskite films
Vidmantas Gulbinas
Center for Physical Sciences and Technology, Saulėtekio av. 3 Vilnius Lithuania
Email: [email protected]
Perovskite materials mostly based on CH3NH3PbI3 are recognized as an excellent low-
disorder material for efficient photovoltaic devices and currently are one of the most popular
research objects in the field of photovoltaics. Perovskite-based solar cells (PSC) are an emerging,
cheap photovoltaic technology, which in the last several years showed a record improvement in
efficiency reaching 22%. Specially designed and fabricated perovskites also demonstrate high
luminescence quantum efficiencies, therefore are also promising for light emitting devices and
lasers. These materials may be fabricated by different techniques typical for organic
semiconductors: processing from solutions, vacuum evaporation, crystal growth. Their electronic
properties are closer to classical semiconductors: monocrystals show high carrier mobilities
reaching thousands of cm2/vs, high dielectric permittivity causes low exciton binding energies
causing dispute if charge carriers are generated by direct band-to-band transitions or via exciton
state like in organic materials. Mobility and exciton binding energy values are widely distributed
in different reports, particularly for thin films. Thus, carrier generation and the motion character
and properties in perovskite still are far from clear understood.
We analyzed charge carrier generation and motion dynamics in organo-lead iodide
perovskites by employing time-resolved photoluminescence (PL) spectroscopy, transient
photoconductivity and time-delayed collection field techniques. We demonstrate that
photoluminescence kinetics of MAPbI3 perovskites strongly changes with excitation intensity, that
was varied over five orders of magnitude. It enabled separation of geminate and nongemintate
carrier recombination processes. Geminate recombination dominates at low excitation fluence
and determines the initial photoluminescence decay. This decay component is remarkably
independent of the material structure and experimental conditions. On a basis of quantum
mechanical numerical calculation results, we argue that the fast photoluminescence decay
originates form gradual spatial separation of photo-generated weakly bound geminate charge
pairs.
Combining transient photocurrent, time-delayed collection field and transient fluorescence
techniques along with numerical simulations, we addressed charge carrier trapping processes in
prototypical methylammonium lead iodide perovskite films. We demonstrate that carrier mobility
decreases with time after their generation, particularly rapidly at low temperatures. We separate
influence of energy traps and barriers and demonstrate the energy barriers, most likely formed at
crystallite boundaries, rather than traps are mainly responsible for the mobility decay. Being
surmountable at room temperature, these barriers still play a key role in determining carrier
mobility and its decay. The suggested concept of the energy barriers moves beyond the
conventional understanding of carrier mobility, diffusion, and recombination processes in hybrid
perovskites.
13
O02
Resonant Raman Scattering in the few-layer Transition
Metal Dichalcogenides
Adam Babinski
Faculty of Physics, University of Warsaw, Poland
Transition Metal Dichalcogenides emerged as promising materials for optoelectronic
applications. Their properties strongly depend on their thickness and their layered structure
makes the fabrication of a few layer structures relatively simple.
Raman scattering spectroscopy a technique of choice to study properties of those materials.
The effect of layer thickness on the Raman scattering will be reviewed.
Results of studies of Raman scattering on few layer molybdenum ditelluride (MoTe2) will be
presented with special focus on resonant effects. It will be shown how the scattering is
modified by bringing illumination in resonance with maxima of electronic joint density of states
in MoTe2.
14
O03
Organic bulk heterojunction photovoltaics and
photodetectors
Beata Luszczynska1, Marek Zdzislaw Szymanski2, 3, Tomasz Klab1
1Department of Molecular Physics, Lodz University of Technology, 90-924 Lodz, Poland
2Karlstad University, Department of Engineering and Chemical Sciences, SE-65188 Karlstad,
Sweden 3Örebro University, School of Science and Technology, SE-70182 Örebro, Sweden
e-mail address: [email protected]
Organic photodiodes are the class of light detectors which are now intensively investigated
with an aim for applications in existing imaging technology, optical communication, wearable
electronics (e.g. medical sensors) and environmental monitoring. Organic semiconductors are an
interesting group of electronic materials because they combine some of the features of classical
semiconductors with advantageous chemical and physical properties typical of organic materials,
in particular polymers.
We investigated organic, bulk heterojunction, characterized with unbalanced charge carrier
mobilities, for application in photovoltaics and photodetectors
The presented drift-diffusion simulation of bulk heterojunction photodiodes with Langevin
recombination indicates that the bandwidth of photodiode is approximately independent of the
mobility of slower charge carriers in the blend. The negative effect of low mobility on the
responsivity can be compensated by increasing the reverse bias. Our study shows that well
performing organic photodetectors can be fabricated using organic semiconductors having too
low mobility for photovoltaic applications. Moreover the simple device structure allows to fabricate
the devices with fast time response.
In the case of the photodetectors designed for NIR spectral range the reversed device
structure might significantly reduce the level of the dark current what results in high responsivity
and detectivity of such devices.
15
O04
New methods of in-situ patterning of OLED emission
area.
Amruth C, Wassima Rekab, Beata Luszczynska and Jacek Ulanski Department of Molecular Physics, Lodz University of Technology, 90-924, Lodz, Poland.
Email: [email protected].
In spite of tremendous progress in synthesis of new,
solution processable materials suitable for printed organic
electronics [1], this technique still remains as an unfulfilled
promise and cannot overcome laboratory scale. Among
different not solved yet problems, there are technological
challanges related to printing techniques, such as difficulties
with controlling morphology and geometry of printed active
layers in a reproducible way; lack of efficient, industrial scale
technology of assembling organic and inorganic components
into working, functional electronic devices; difficulties in
fabrication by printing multilayer structures.
In this work we demonstrate new approach to the inkjet
printing technique, which is perhaps the most promising
method among solution processable techniques for
manufacturing of low-cost and high resolution Organic Light
Emitting Diodes based displays [2, 3]. The film formation
process is analysed and we present the comprehensive study of OLEDs with the inkjet printed
TADF-based emissive layers [4] and the electron injection layers [5]. We have elaborated
stable ink formulations suitable for industrial grade printing. The possibility of inkjet printing of
efficient emissive layers or electron injection interlayers enables patterning of the emission
area of OLEDs; an example is shown in Fig. 1. Such simple technique for patterning emission
area can be applied to a wide range of printed displays such as signage, advertisings or smart
packaging and, in our opinion, it is an important step towards printed electronics on industrial
scale.
ACKNOWLEDGMENTS: This work was supported by the grants: 674990 EXCILIGHT - H2020-MSCA-ITN-
2015; 33 0355/PnH/2016 – MNiSW, Poland; TANGO2/340019/NCBR/2017 – NCBR, Poland.
REFERNCES
[1] B. Luszczynska, K. Matyjaszewski and J. Ulanski (Eds); Mobile Robots 8 (2001) pp. 520-531.
[2] A. C, B. Luszczynska, B. G. R. Dupont and Z. Sieradzki, Display and Imaging, 2 (2017) pp. 339–358.
[3] A. C, M. Z. Szymanski, B. Luszczynska, J. Ulanski, Sci. Reports, 9 (2019), 8493
[4] A. C, B. Luszczynska, M. Z. Szymanski, J. Ulanski, K.Albrecht, K. Yamamoto, Org. Electron,
74 (2019) 218-227 [5] J. Ulanski, B. Luszczynska, A. C, J. Ulanski, Method of OLED fabrication, Polish Patent application nr: 430487
(2019)
10 cm
15
cm
Fig. 1 Printed OLED with portrait of
Marie Sklodowska-Curie.
16
O05
AlGaN/GaN heterostructures for plasma wave instabilities
in THz regime
Irmantas Kašalynas1 and Maciej Sakowicz2 1Center for physical sciences and technology, CPST, Vilnius, Lithuania
2Institute of High Pressure Physics Polish Academy of Sciences, UNIPRESS, Warsaw, Poland
irmantas.kaš[email protected]
At the beginning of 90’s Dyakonov and Shur proposed plasma excitations in nanometer
field effect transistors for THz detection and emission [1, 2]. They have shown that the channel
of a field effect transistor (FET) can act as a resonator for plasma waves with a typical wave
velocity s 108 cm/s. The fundamental frequency f of this resonator depends on its
dimensions and for gate length L of a micron or less, can reach the terahertz (THz) range,
since f ~ s/L. Dyakonov and Shur [1, 2] predicted also that a steady current flow in an
asymmetric FET channel can lead to instability against the spontaneous generation of plasma
waves. This can in turn produce the emission of electromagnetic waves in THz regime.
Nanometer semiconductor structures may serve as resonators for plasma excitations
(plasma waves) and can reach the THz range. Group of prof. W. Knap confirmed
experimentally theoretical predictions on THz emission and detection [3]. However all
observed resonant phenomena were much broader than theoretically predicted. Also in many
cases the observed emission was not resonant and not voltage tunable [4].
Polish-Lithuanian Funding Initiative DAINA based project „Terahertz Plasma Wave
Instabilities in GaN/AlGaN Nanowires“ aims to solve three problems which limit plasma wave
instabilities generation in AlGaN/GaN high-electron-mobility transistor (HEMT) structures: (i)
Coexistence of concurrent oblique modes; (ii) Shallow impurities emission; (iii) Blackbody
radiation caused by Joule heating of biased HEMT channels. In this work we proposed the
solutions based on new designs of narrow channel (nanowire) HEMT, an original control of
the residual impurities via THz electroluminescence spectroscopy, and a specific cooling of
the plasmonic channels and reduction of the BB radiation of GaN/AlGaN HEMT structures
grown on SiC substrate [5-8].
REFERNCES
[1] M. I. Dyakonov, M. S. Shur, Phys. Rev. Lett. 71, p.2465 (1993).
[2] M. I. Dyakonov, M. S. Shur, IEEE Trans. Electron Devices 43, p.380 (1996).
[3] W. Knap, et al., J. Infrared, Millimeter, Terahertz Waves 32, p.618 (2011).
[4] V. Jakstas, et al., Appl. Phys. Lett. 110, p.202101 (2017).
[5] G. Cywiński, Appl. Phys. Lett. 112, 133502 (2018);
[6] V. Janonis, et al., physica status solidi (b) 255, art. no. 1700498 (2018).
[7] I Grigelionis, et al., Materials Science in Semiconductor Processing 93, p.280 (2019).
[8] P. Sai, et al., submitted to Appl. Phys. Lett. (2019).
17
O06
Polish Metrology - 100 years of progress
Dr. Włodzimierz Lewandowski
Former Principal Physicist at the International Bureau of Weights and Measures in Sèvres
Former President of the Central Office of Measures
Email: [email protected]
Modern state metrology in Poland begins on 8 February 1919, date of a decree creating
the Central Office of Measures (GUM). The first two decades of the GUM activity was
dedicated mainly to the organization of appropriate structure and unification of various
systems of units, a heritage of the period of partition of our country. Less attention was payed
to the technological support of the home industry. After the World War II some relation with
industry and science was maintained, but in fact a slow and deepening bureaucracy was
progressing, even after recovering full sovereignty in 1989.
However, after a period of about ten years of national debate led by Ministry of Economy
and Sejm, in 2016 was initiated an important reform of state metrology. A new direction was
appointed, a law on measures was revised and a Metrological Council supervising GUM was
set up. The main goal was a return to scientific research supporting home industry of advanced
technology, and ultimately transforming the Central Office of Measures into a Polish Institute
of Metrology.
Since then a number of important tasks were accomplished, among them was setting up
eight permanent Working Groups with industry, ten Technical Committees composed of best
home and foreign experts for supervising GUM laboratories, four strategic sectors
coordinating key industrial, scientific and social challenges. But above all else started creation
of external laboratory campus in Kielce, where most advanced metrological research will be
carried out.
Concerning research advances, most important were achieved in time metrology, also
in cooperation with Lithuanian state time laboratory [1], [2]. Poland contributes already to the
time infrastructure of the European Satellite Navigation System GALILEO [3]. Also Poland has
developed most advanced network of fiber optic time transfer, and is successfully cooperating
in this field with Lithuania. For the „mise en pratique” of the new definition of the kilogram
Polish industry developed in cooperation with GUM, a vacuum mass comparator.
This presentation will detail above issues, with emphasis put on advanced metrological
research for the needs of industry of high technology, and on regional European cooperation
especially with Lithuania.
REFERENCES
[1] J. Azoubib, J. Nawrocki, W. Lewandowski, Metrologia (2003), 40, issue 3, pp. S245-S248.
[2] J. Nawrocki, P. Dunst, P. Nogaś, B. Nagórny, D. Lemański, R. Miškinis, E. Urba, D.
Smirnov, E. Baniuliene, A. Czubla, P. Szterk, R. Osmyk, Ł. Czerski, A. Urban, presented at
ION PTTI (2017), Monterey, California.
[3] W. Lewandowski, F. Arias, Metrologia, 48, (2011) S219–S224, Special Issue «Modern
applications of timescales».
18
O07
High-Definition Laser Metal Deposition
Genrik Mordas1, Ada Steponavičiūtė1, Karolis Stravinskas1, Sergejus Borodinas2
1Department of Laser Technologies, Center for Physical Sciences and Technology,
Savanoriu ave. 231, Vilnius, Lithuania 2Faculty of Civil Engineering, Vilnius Gediminas Technical University,
Sauletekio ave. 11, Vilnius, Lithuania
Email: [email protected]
Laser Metal Deposition (LMD) is an advanced AM technology relevant to the
metalworking industry and composite material research. Improved accuracy of particle
positioning in experimental facility is enhanced by applying numerically obtained theoretical
solution of coupled laser technology, ultrasonic vibrations, aerodynamic flow and particle flow
problem. Unique solutions allow to perform high-definition multi-material 3D printing at once.
The main technological principle of our developed LMD system is illustrated in Fig. 1 and
consists of 5 parts: (I) ultrasonic metal powder positoning jet, (II) laser system, (III) sucton
system, (IV) building platorm with a controller and (V) monitoring system. Jet is used to
separate metal partcles and point the powder flow towards the building platorm. Laser beam
is focused and pointed to the metal powder on the building platorm. Suction system helps to
avoid defects by collectng unmolten powder partcles and agglomerates from the building
platorm. Building platorm, where the 3D object is being produced, has three moving axes (X,
Y, Z). The whole proccess is being monitored by a monitoring system, which can determine
building platorm temperature, stability of metal partcle flow, stabiliy of partcle flow, size
(diameter) of the partcle flow, pressure and oxygen concentraton inside the building chamber.
Fig. 1 Technological principle of new LMD system
19
O08
Molecular Modeling of Electrochemical Interfaces for
Energy Conversion
S. K. Stauffer1, L. Vilčiauskas1
1Center for Physical Sciences and Technology, Saulėtekio al. 3, LT-10257 Vilnius, Lithuania.
E-mail: [email protected]
The absolute majority of electrochemical processes are
defined as taking place at the electrochemical interfaces
comprising an electronic or a mixed conductor (electrode) and
ionic one (electrolyte). These processes also form the
functional basis of electrochemical energy conversion
devices: batteries, fuel cells, supercapacitors etc. that are
recently receiving increasing attention due to the
developments in renewable energy.
Modern molecular modeling techniques such as density
functional theory and molecular dynamics provide
unprecedented detail and insight into these processes with an
atomic spatial and temporary resolution unattainable to any
experimental method.
We will present our recent results in modelling various Li/Na-ion battery interfaces using
different methodologies and scales as well as what are the critical issues and limitations of
these approaches. In addition, we will discuss how these results help to elucidate the
fundamental questions regarding the function and problems of electrochemical energy
conversion systems.
REFERNCES
[1] M. J. Boyer, L. Vilčiauskas, G. S. Hwang; Phys. Chem. Chem. Phys., 18 (2016) pp. 27868-27876.
[2] S. K. Stauffer, L. Vilčiauskas; J. Phys. Chem. B, 122 (2018) pp. 7779-7789.
Fig. 1 Thermodynamic Born-Haber
cycle for the electrochemical
delithiation of LixTi2O4 spinel at the
interface with ethylene carbonate
based electrolyte.
20
O09
Plasmon enhancement of performance of photosystem I
based biomimetic graphene solar cells
Marcin Szalkowski1, Dorota Kowalska1, Ersan Harputlu2, Małgorzata Kiliszek3,
C. Gokhan Unlu4, Kamil Wiwatowski1, Kasim Ocakoglu2,5, Joanna Kargul3,
and Sebastian Maćkowski1
1Instytute of Physics, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus
University, Grudziądzka 5, 87-100 Toruń, Poland 2 Advanced Technology Research & Application Center, Mersin University, Cilikkoy Campus,
TR33343, Yenisehir, Mersin, Turkey 3 Center of New Technologies, University of Warsaw, Banacha 2C, 02-097 Warsaw, Poland
4 Department of Biomedical Engineering, Pamukkale University, TR-20070 Denizli, Turkey 5 Department of Energy Systems Engineering, Faculty of Technology, Tarsus University, 33400
Tarsus, Turkey
Email: [email protected]
We present plasmonic enhancement of optical and electrochemical performance of bio-
inspired electrodes for solar cells. In our construction robust photosystem I (PSI) complexes
isolated from red algae Cyanidioschyzon merolae, characterized by quantum efficiency of
photoinduced charge separation close to 100%, are interfaced with graphene. This atomically
thin hexagonal lattice of carbon is an efficient energy and electron acceptor [1]. We have
previously shown that by chemical modification of graphene with nitrilotriacetic acid (NTA)
followed by binding of cytochrome (cyt) c553, it is possible to obtain uniform assembly of PSI,
which facilitates directional charge flow leading to its improved electrochemical performance
[2].
In the present work we demonstrate that coupling of PSI-based electrodes with a metallic
nanostructure – silver island film (SIF) prepared both on conductive FTO substrates and on
glass coverslips – leads to strong modification of their optical properties. In particular, it results
in significantly enhanced PSI absorption efficiency, as evidenced by the results of
fluorescence microscopy. This strong improvement (characterized by enhancement factor of
15) is found especially in absorption of green light, which is rather poorly absorbed by native
PSI complexes. Electrochemical analysis proved that incorporation of the plasmonically active
nanostructure results also in enhanced photocurrents generated in such electrodes. For SIF-
containing samples we measured photocurrents exceeding 1000 nA cm-2 (with overpotential
of -300 mV), while for analogous reference sample photocurrents lower than 300 nA cm-2 were
observed.
Research was supported by project DZP/POLTUR-1/50/2016 funded by the National
Centre for Research and Development.
REFERNCES
[1] R. Nair et al., Science 320 (2008) 1308.
[2] M. Kiliszek, MSz et al., Journal of Materials Chemistry A 6 (2018) pp.18615-18626.
21
O10
Mobility of charge carriers in organic-inorganic
perovskites
Ramūnas Aleksiejūnas, Patric Ščajev, and Saulius Juršėnas
Institute of Photonics and Nanotechnology, Vilnius University, Saulėtekis Ave. 3, LT-10257
Vilnius, Lithuania
Email: [email protected]
Metal-halide perovskites became very attractive for
cheap and scalable production of not only the solar cells, but
also the thin film transistors, light emitting diodes, and lasers.
Mobility and lifetime of charge carriers play a crucial role in
determining the efficiency of photonic devices; however,
some processes governing these parameters remain
understudied. In particular, little is still known about the
diffusivity and mobility dependencies on carrier density at
higher excitations, mostly due to the difficulties in measuring
it.
In this presentation, we discuss the results of carrier
diffusion, mobility, and lifetime measurements using the time-
resolved optical techniques in CH3NH3Pb(Sn)X3 perovskite layers. In particular, we show the
advantages of light-induced transient gratings method that enables direct determination of
carrier diffusivity at high carrier densities. We demonstrate two different regimes of carrier
transport in the perovskites, namely band-like or localization-limited carrier diffusion. Band-
like diffusion with typical ambipolar coefficient of ~1 cm2/s takes place in high quality crystals
and layers. It is determined by fundamental material properties and is controlled by polar-
optical electron-phonon scattering. It increases weakly with carrier density due to degeneracy
of carriers and is limited by screened electron-hole scattering at high carrier densities. The
trap-limited diffusion, on the other hand, varies in a wide range from 10-4 to 1 cm2/s due to
strong dependence on trap and carrier densities.
Finally, we show that diffusivity strongly depends on layer growth technology. It can be
enhanced, e.g., by using chemical additives during MAPbX3 layer formation. On the other
hand, wet cast MASnI3 layers show intrinsically high diffusivity of carriers comparable to that
of vapor deposited layers or crystalline MAPbX3 samples, despite very high background p-
type doping.
Two regimes of carrier diffusion in
MAPbX3 perovskite layers
22
O11
Enhancement of infrared optical response of organic
polymers in hybrid nanostructures
Justyna Grzelak1,3, Aneta Prymaczek1, Marcin Nyk2, Maciej Ćwierzona1,
Dawid Piątkowski1 and Sebastian Maćkowski1
1 Institute of Physics, Nicolaus Copernicus University, Torun, Poland 2 Institute of Physical and Theoretical Chemistry, Wroclaw University of Technology,
Wroclaw, Poland
Email: [email protected]
Up-converting nanomaterials are promising candidates for sensitizing organic solar cells
to infrared radiation [1,2]. This however requires developing conditions for efficient energy
transfer between the nanocrystals and polymers.
In this work, we describe several strategies to enhance the optical response of
conductive polymers to the infrared radiation, for possible application in organic solar cells [3].
Our hybrid nanostructures were composed three types of nanomaterials: conductive polymers
with different optical characteristics (absorption/emission), which were energy acceptors; up-
converting NaYF4 nanocrystals doped with Er3+ and Yb3+ ions, which were energy donors; and
plasmonically active gold nanoparticles or single silver nanowires. The plasmonic
nanomaterials were applied to modify the optical properties of fluorophores placed in their
vicinity.
In experiments we used confocal fluorescence microscopy to investigate the energy
transfer efficiency from single up-converting nanocrystals to polymers exhibiting different
optical properties. The efficient and spectrally – dependent energy transfer from single up-
converting nanocrystals to P3HT polymer was observed [4]. For F8BT and PFO polymers we
found that reabsorption plays the dominant role in determining the spectral properties of such
hybrid nanostructures. It was also observed that the efficiency of the energy transfer depends
on the distance between single up-converting nanocrystals and P3HT polymer. Including the
plasmonic excitations associated with metallic nanoparticles resulted in further improvement
of the energy transfer from the up-converting nanocrystals to the polymers.
Overall, the results prove that it is possible to sensitize conductive polymers to infrared
radiation, and thus to allow for more efficient utilization of this part of solar radiation in organic
solar cells.
This work was supported by projects 2017/26/E/ST3/00209, 2017/27/B/ST3/02457 and
2016/21/B/ST3/02276 from the National Science Center.
REFERNCES
[1] N. Hartman, ACS Nano 7, 11 (2013) pp. 10257–10262
[2] D. Piątkowski, Nanoscale, 7, 4 (2015), pp. 1479–1484
[3] J. Chappel, Nature Materials 2 (2003), pp. 616-621
[4] J. Grzelak, Appl. Phys. Lett. 105 (2015), pp. 163114
23
O12
Quantum theory of multiscale relaxation dynamics in
molecular aggregates
Darius Abramavicius
1Institute of Chemical Physics, vilnius University, Sauletekio al. 9-III, Vilnius, Lithuania
Email: [email protected]
Photoinduced excitation transport and charge separation in in molecular systems has
recently gained special attention due to high energy conversion efficiency in molecular solar
cells. It has been observed that electrons and holes are very effectively generated on the
inteface between two phases of the material even in very low externally applied electric fields.
Early subpicosecond dynamics requires complete quantum description of such processes in
order to reveal the underlying mechanisms of these processes. Stochastic Schroedinger
Equation (SSE) approach has been applied to simulate charge coherent dynamics during
primary charge separation events after photoexcitation process. The approach combines
environment mediated statistical mixture of quantum propagation trajectories in the spirit of
path-integral approach and allows to obtain distribution functions of physical variables.
Dynamical processes of local heating and environment reorganization are revealed. Weak
system-environment coupling regime demonstrates the classical results of charge hopping.
We obtain two-fold charge separation kinetics: initial coherent charge separation is driven by
quantum delocalization, what later evolves into diffusive hopping motion.
24
O13
Biofunctionalized multifunctional nanoconstructs based
upconverting NaYF4 doped rare earth and magnetic
Fe3O4 nanoparticles for theranostic applications.
Bożena Sikora1, Przemysław Kowalik1, Anna Borodziuk1, Izabela Kamińska1,
Jakub Mikulski1, Karolina Zajdel2, Magdalena Duda1, Krzysztof Fronc1, Paulina
Grzączkowska1,3, Malwina Szczęsna4 Jarosław Rybusinski3, Jacek Szczytko3,
Roman Minikayev1, Tomasz Wojciechowski1, Kamil Sobczak5, Magdalena Kulpa-
Greszta6, Robert Pązik7, Małgorzata Frontczak-Baniewicz2, Łukasz Kłopotowski1
1Institute of Physics, Polish Academy of Sciences, Warsaw, Poland 2Mossakowski Medical Research Centre, Polish Academy of Sciences, Warsaw, Poland
3Institute of Experimental Physics, Faculty of Physics, University of Warsaw, Warsaw, Poland 4Faculty of Physics Warsaw University of Technology, Warsaw, Poland
5Faculty of Chemistry, Biological and Chemical Research Centre, University of Warsaw,
Warsaw, Poland 6Faculty of Chemistry, Rzeszow University of Technology, Rzeszow, Poland
7Faculty of Biotechnology, University of Rzeszow, Rzeszow, Poland
Email: [email protected]
The main goal of our research was to create
multifunctional nanoconstructs based on two kinds of
nanomaterials. We synthetized up-converting nanoparticles
(UCNPs) of yttrium sodium fluorides and superparamagnetic
iron oxide nanoparticles coated by silica.
The UCNPs based on β-NaYF4 with a hexagonal structure
doped with Yb3+ and Er3+ ions exhibit visible luminescence
(green and red) after near infrared (980 nm) laser excitation.
The nanoparticles were functionalized by photosensitizer
(Rose Bengal), and the energy transfer from nanoparticles to
the dye was observed. The Rose Bengal produced the
reactive oxygen species (ROS), which resulted in the 4T1
breast cancer cells death. This construct can be used to
photodynamic therapy (PDT) for cancer treatment.
The other kind of UCNPs– NaYF4 doped with Tm3+ and
Yb3+ ions– irradiated by 980 nm light convert this radiation to
visible and ultra violet light. At the same time thanks to high energy generated light (UV) in
aqueous environment UCNPs generate ROS which are toxic for cancer cells. This kind of
nanoparticles do not need photosensitizer for PDT cancer treatment.
This kind UCNPs were biofunctionalized by antihuman-IgG antibody (UCNPs@SiO2-
PEG-AntiH:IgG) which can be attached to the human-IgG on the cells surface. This type of
nanoparticles can be used in molecular targeting therapy, and after ROS generation for
targeting PDT.
Fig. 1 UCNPs-RB nanoconstruct
inside 4T1 breast cancer cells after
980 nm of excitation. Blue – nuclei;
green – lysosomes, red –
nanoparticles.
25
Another group of nanoparticles prepared by us was superparamagnetic Fe3O4 doped by
Y3+ ions. The hyperthermia effects were measured as a function of Y3+ amounts inside Fe3O4.
The intrinsic loss power factor was determined. The Fe3O4 nanoparticles were introduced into
4T1 breast cancer cells which were destroyed in magnetic hyperthermia. The Fe3O4
nanoparticles can be used in targeted therapy by using an external magnetic field. They can
also cause an contrast increase in magnetic resonance imaging (MRI).
Combining PDT with hyperthermia treatment in one nanoconstruct will allow for a more
efficient cure of patients than offered by the currently used modalities.
The research was partially supported by the projects NCN DEC-2014/15/D/ST5/02604,
2017/01/X/ST3/01380 and by the Foundation for Polish Science through the IRA Programme cofinanced by EU
within SG OP. This work has been done in the NanoFun laboratories co-financed by the European Regional
Development Fund within the Innovation Economy Operational Program, the Project No. POIG.02.02.00-00-
025/09/.
26
O14
Magnetic field sensors for high-pulsed magnetic field
measurements.
V. Stankevič, N. Žurauskienė, S. Balevičius, S. Keršulis, V. Plausinaitienė
State research institute Center for Physical Sciences and Technology, Savanorių ave. 231, LT-
02300 Vilnius, Lithuania
Email: [email protected]
The demand for new magnetic field sensing technologies is increasing rapidly due to the
development of advanced scientific and industrial devices and techniques such as non-
destructive pulsed-field magnets, flux compression generators, mass acceleration, high power
electrical motors, electromagnetic welding systems and other applications. Each application
has specific requirements for the sensor fabrication, its characteristics, range of operation,
accuracy, etc.
The response signal from commercially available magnetic field sensors based on Hall
or anisotropic magnetoresistance effects depends on the magnitude and the direction of
magnetic field. Therefore, such sensors cannot be applied in cases if both the magnitude and
the direction of the field changes simultaneously during measurement. For this reason the
sensors, which could measure magnitude of the magnetic field independently on its direction,
are of great interest. Recently, it was demonstrated that the colossal magnetoresistance
(CMR) phenomenon in thin nanostructured manganite films can be successfully used for the
development of CMR-B-scalar sensors, which are able to measure the magnitude of high
pulsed magnetic fields up to the megagauss limit in a very small volume of ≈10-2 mm3. A high
pulsed magnetic field measurement system based on these sensors was developed by the
group of scientists in the Center for Physical Sciences and Technology. The system is
protected against strong electromagnetic interference and is able to measure the magnitude
of pulsed magnetic fields from 20 mT to 40 T in the range from DC up to 100 kHz independently
of the magnetic field direction. The created meter was successfully used for investigations of
electrodynamic processes in electromagnetic launchers (railguns), for investigation of
magnetic field dynamics during electromagnetic metal forming and welding, and for measuring
of strong pulsed magnetic field in non-destructed magnets.
Recent investigations on manganite thin films used for magnetic field sensors fabrication
will be presented and discussed. The change of technological conditions allows to tune the
magnetoresistive properties of the films what enables to develop the magnetic field sensors
operating in different magnetic field and temperature ranges.
27
O15
MoTe2 thin films and nanostructures grown by molecular
beam epitaxy
Janusz Sadowski1,2,3, Bartłomiej Seredyński1, Zuzanna Ogorzałek1, Marta
Gryglas-Borysiewicz1, Sławomir Kret3 and Wojciech Pacuski1
1 Department of Physics, University of Warsaw, Pasteura 5, 02-093 Warsaw, Poland. 2 Department of Physics and Electrical Engineering, Linnaeus University, 391 82 Kalmar,
Sweden 3 Institute of Physics Polish Academy of Sciences, al. Lotników 32/46, 02-668 Warsaw, Poland
Email: [email protected]
MoTe2 belongs to layered transition metal
dichalcogenides (TMD) with interesting optoelectronic
properties, e.g. direct energy gap of 1 monolayer thick films,
and very high exciton binding energies. As many other TMDs,
MoTe2 occurs in several polytypes - semiconducting
hexagonal 2H phase, metallic monoclinic 1T’ and
orthorhombic Td ones. The latter existing at low temperature
(below 240 K) exhibits topological Weyl semimetal properties
with very peculiar magnetotransport characteristics due to
topological protection of Weyl quasiparticles involved in the
charge transport [1].
So far 2D films of MoTe2, similar to other TMDs have
been obtained mainly by exfoliation from bulk crystals yielding flakes with micrometer size
lateral dimensions and uncontrolled shapes.
Here we report on the successful molecular beam epitaxy (MBE) growth of MoTe2 on
large substrates (2-3 inch in diameter) of commercially available wafers of sapphire, GaAs or
Si. The MBE growth is well controlled by reflection high energy electron diffraction (RHEED).
Both the crystalline perfection and thickness of the deposited layers can be accurately
controlled with this method. During the MBE growth of MoTe2 films on different substrates
distinct RHEED intensity oscillation are recorded (see Fig.1) enabling the control of the
thickness up to 1 ML precision. Even though MoTe2 on above mentioned (and other)
substrates grows in the Van der Waals mode with weak interaction at the layer-substrate
interface, the choice of a suitable substrate is of essential importance to obtain films with the
best crystalline perfection and lateral uniformity. At some peculiar growth conditions the
transition from 2-dimensional layer-by layer to 3-dimensional growth mode and formation of
MoTe-based nanowires has been observed.
This work has been supported by the National Science Centre (Poland) through project
No. 2017/27/B/ST5/02284.
REFERENCES
[1] A. N. Berger, et. al., B. A. Bernewig and A. N. Pasupathy; npj Quantum Materials 3 (2018) pp. 2-1 – 2-8.
70
0 1000 2000 3000
4 min
time (s)
RHEED oscillations of 2H-MoTe2 UW1176
Fig. 1 RHEED intensity oscillations
of 2H MoTe2 grown on sapphire
28
O16
Optical spectroscopy of CdSe/ZnSe quantum dots with
single Fe2+ ions
T. Kazimierczuk, T. Smoleński, A. Rodek, J. Kobak, M. Goryca, W. Pacuski,
A. Golnik, P. Kossacki
Institute of Experimental Physics, Faculty of Physics, University of Warsaw,
ul. Pasteura 5, 02-093 Warsaw, Poland
Reaching limits of miniaturization related to atomic structure of matter poses an important
challenge of our times. A question arises whether further development of technologies such
as nanometer scale electronics and material science is going to be limited by a finite size and
discrete structure of electronic states of single atoms. Or, conversely, if we are able to take
advantage of properties of individual ions or defects, as it is proposed in solotronics [1], a
rapidly developing area of research and technology of optoelectronics exploiting solitary
dopants.
Our approach to solotronics is based on introducing individual dopants of transition metal
(TM) ions such as Mn, Co, and Fe to quantum dots (QDs). Since single TM ion modifies
properties of a QD [2], we can study spin configuration of TM ion using optical transitions of a
QD.
We find that comparing to bulk, nanostructures such a QDs strongly modify magnetic
and optical properties of TM ions [3]. Most striking example is the case of Fe2+ ion. In bulk zinc
blende crystals Fe2+ ion exhibits a non-degenerate ground state, which leads to rather weak
response to the magnetic field. In contrast, high strain of the QD changes the character of the
energy spectrum of the Fe2+ ion leading to formation of doubly degenerate state with spin Sz
= ±2 [4,5].following.
REFERNCES
[1] P. M. Koenraad, M. E. Flatte, Nat. Mater. 10, 91 (2011).
[2] L. Besombes et al., Phys. Rev. Lett. 93 207403 (2004).
[3] J. Kobak et al., Nat. Commun. 5, 3191 (2014).
[4] T. Smoleński, et al., Nat. Commun. 7, 10484 (2016).
[5] T. Smoleński et al., Phys. Rev. B 96, 155411 (2017).
29
O17
Development of National Metrology System and the
Ways for International Cooperation
Evaldas Naujalis
Metrology Department, State Research Institute Center for Physical Sciences and Technology,
Savanorių Ave. 231, LT-02300 Vilnius, Lithuania
Email: [email protected].
Center for Physical Sciences and Technology (FTMC)
Metrology Department (MD) was authorized to perform and
implement functions of the National Metrology Institute (NMI)
since 1 July 2014. The CIPM MRA agreement on behalf of
FTMC was resigned on 17 November 2014 by Director Dr.
Gintaras Valušis. Year 2018 was historical for metrologists all
over the world. BIPM's Member States voted on 16 November
2018 to revise the International System of Units (SI),
changing the world's definition of the kilogram, the ampere,
the kelvin and the mole. The decision, made at the 26th
General Conference on Weights and Measures (CGPM),
means that all SI units will now be defined in terms of
constants that describe the natural world. This will assure the
future stability of the SI and open the opportunity for the use of new technologies, including
quantum technologies, to implement the definitions. Two researchers dr. Rimantas Vaitkus
and dr. Evaldas Naujalis from FTMC MD were authorized by the Decree of Prime Minister of
Lithuania to represent Republic of Lithuania in the 26th CGPM in Versailles, France [1]. The
new definitions came into force on 20 May 2019.
FTMC Metrology Department maintains national standards in seven different
measurement fields: time and frequency, temperature, electrical standards, mass, length,
ionizing radiation and chemical measurements. Time and Frequency Standard Laboratory
(TFSL) is reproducing values of the unit of time, the second (s) and the unit of frequency- hertz
(Hz). Its mission is representation of Lithuanian Coordinated Universal Time UTC(LT),
ensuring the traceability of the magnitudes reproduced to the International System of Units
(SI), disseminating them to Lithuanian scientific establishments, personal and legal bodies by
calibrating their working standards and measurement devices, disseminating Lithuanian time
scale and other relevant means. TFSL, in cooperation with the JSC "BaltStamp", provides time
stamping services, which meet the eIDAS regulations. In collaboration with the Swiss
company “GVR Trade” and the Lithuanian JSC “MitSoft” Time and Frequency Standard
Laboratory pursue the EUROSTARS–2 project entitled „System of passive SAW sensors
exploiting UWB hyperbolically frequency modulated Signals“ (UWB_SENS).
The mission of the Electrical Standards Laboratory (ESL) is maintaining and developing
the standards of unit of voltage, the volt (V), and unit of resistance, the ohm (Ω), ensuring their
traceability to the SI, calibrating working standards and measurement devices, pursuing
research in the field of measurement of voltage, resistance and electrical current.
The Temperature Unit Standard Laboratory (TUSL) is realizing the international
temperature scale ITS-90 and the value of the unit of temperature the kelvin (K) ensuring its
Fig. 1. New logo of SI
30
traceability to SI. Lithuanian National Standard of temperature unit in the range from -195°C
to +961,78 °C is primary level standard and +1084,62 °C reference point of freezing point of
copper (Cu) - secondary level.
The Ionizing Radiation Metrology Laboratory (IRML) was piloting the EURAMET Project
No.1437 “The follow-up interlaboratory comparison of the radionuclide calibrators”. The
secondary standard equipment for radionuclide measurement in a high activity range (above
1 MBq) used in Lithuania was compared with the similar equipment used in national metrology
institutes of Czech Republic and Slovakia. The radionuclides applied in a nuclear medicine
such as 18F, 67Ga, 99mTc, 111In, 123I, 125I, 131I, 137Cs (as a check source), 201Tl and 223Ra have
been standardized with the well-type ionizing chambers Fidelis and Capintec 15R and the
uncertainty budget have been evaluated. The results confirmed that consistent, safe and
effective radionuclide activity measurement services to the medicine community are provided
in Lithuania.
Metrology is not restricted only to standards of physical units but also reliable and
accurate chemical measurements in sectors of health care, food safety and environment
protection which could be provided by the Laboratory for Metrology in Chemistry (LMiC). The
laboratory successfully participating in ALCOREF Project 16RPT02 „Certified forensic alcohol
reference materials“ [2] in the frame of
European Metrology Programme for
Innovation and Research (EMPIR) since
September 2017. It is a great example of
international collaboration between 10
partner's NMIs from 10 different European
countries. Federal Institute for Materials
Research and Testing (BAM, Germany) is
coordinating this project The main objectives
of the project are research on accurate
measurements, homogeneity, short and long
term stability estimation for production of
ethanol/water certified reference materials
(CRMs) and building of a new regional
metrological capacity for certification of CRMs
for breath alcohol analyzers control.
The vision of EURAMET and its members is to ensure Europe has a world-leading
metrology capability, based on high-quality scientific research and an effective and inclusive
infrastructure, that meets the rapidly advancing needs of end users. New possibilities of
realising this aim is EURAMET's European Metrology Networks (EMNs). FTMC MD together
with partners from Nordic and Baltic countries started the action of establishing of such a
network.
REFERNCES:
[1] https://www.bipm.org/en/cgpm-2018/
[2] https://www.bam.de/Content/EN/Projects/Alcoref/alcoref.html
[3] https://www.euramet.org/european-metrology-networks/
Fig. 2. EMPIR project consortium partners.
31
O18
Towards Bose-Einstein condensation of exciton
polaritons at room temperature: tunable liquid crystal
microcavities
J. Szczytko1, K. Lekenta1, M. Król1, R. Mirek1, R. Mazur2, P. Morawiak2, P. Kula2,
W. Piecek2, M. Matuszewski3, W. Bardyszewski4, P. G. Lagoudakis5, B. Piętka1
1Department, Institution, Address – all in 12pt Arial, Italic, centered. 2Author names in 14pt Arial, centered. Presenting author should be underlined.
Email: the email of presenting author – 12pt Arial, centered.
The possibility to observe the exciton polaritons - quasiparticles arising from a strong
coupling of cavity photons and excitons in local emitters (e.g. dye molecules, transition metal
dichalcogenides (TMDs) monolayers) - relies heavily on the tuning of energy difference
between excitonic and photonic mode. Exciton polaritons are bosons with a small effective
mass, for which nonlinear phenomena such as superfluidity, polariton lasing or Bose-Einstein
condensation can be observed at room temperature.
In this communication we present a novel kind of a tunable microcavity consisting of a
nematic liquid crystalline (LC) birefringent optical medium enclosed in a typical Fabry-Perot
resonator [1] and filled with an emitter: organic dye or TMDs. The long-range order of
elongated liquid crystals molecules results in a strong anisotropy in particular in optical
properties. The liquid nature of these materials, and most of all the large freedom of molecular
reorientation, allow for convenient control of these properties by relatively weak external
electric fields. Significant changes in the optical properties of LC can be obtained after applying
merely several volts. With the ability to manipulate the permittivity tensor and, therefore,
effective refractive indices for different polarizations of light it is possible to tune the energy
splitting between cavity modes which strongly influences the luminescence and lasing coming
out from the microcavity (Fig. 1). Our novel device allows for the integration of Bose-Einstein
condensates into the room-temperature operating devices.
Fig. 1. a) Scheme of the tunable LC microcavity filled with MoSe2 and b) experimental results of luminescence
from a single monolayer MoSe2 flake under applied voltage and c) luminescence form a LC filled with a dye.
32
ACKNOWLEDGEMENTS
This work was supported by the Ministry of Higher Education, Poland under project "Diamentowy Grant":
0005/DIA/2016/45 and 0109/DIA/2015/44 and the National Science Centre grant 2016/23/B/ST3/03926 and by
the Ministry of National Defence Republic of Poland Program – Research Grant MUT Project 13-995.
REFERNCES
[1] K. Lekenta et al., Tunable optical spin Hall effect in a liquid crystal microcavity. Light Sci. Appl. 7, 74 (2018).
33
O19
Synthesis and investigation of new organometallic
semiconductors containing dimethoxydiphenylamine-
substituted carbazole fragments
Mantas Marčinskas, Tadas Malinauskas
Faculty of Chemical Technology, Kaunas University of Technology, Radvilėnų pl. 19, Kaunas
Email: [email protected]
Perovskite solar cells (PSCs) have attracted a lot of scientists attention, since their power
conversion efficiency (PCE) has increased from 3.9% to 23.9% over the last decade. The main
material in these photovoltaic devices is perovskite, which benefits from simple synthesis, from
inexpensive precursors and such beneficial properties as sufficiently high conductivity and
wide light absorption [1].
The energy conversion efficiency mostly depends on the hole transporting materials
(HTMs), which also can influence the stability of whole photovoltaic device. The most
commonly used organic HTMs, such as well-known spiro-OMeTAD, often require complex
and expensive synthesis; furthermore, majority of the best efficiency results were achieved
using additives (dopants), such as tert-butylpyridine, lithium
bis(trifluormethanesulfonyl)imide and as a consequence these
devices usually suffer from long-term stability issues [2].
Organometallic HTMs benefit from simple one or two-step
synthesis procedures and usually can be purified by quick and
inexpensive methods avoiding column chromatography.
Moreover, organometallic nature of the semiconductors can
provide additional advantageous properties, consequently these
compounds may be used as dopants-free HTMs [3].
In this work, AgTFSI, CuTFSI and Cu(TFSI)2
organometallic semiconductors were synthesized
using N3,N3,N6,N6-tetrakis(4-methoxyphenyl)-9-
(pyridin-4-yl)-9H-carbazole-3,6-diamine (P1) as a
precursor (Fig. 1).
The best results with dopants were achieved
using Cu(TFSI)2-based organometallic compound
(Fig. 2) – the maximum power conversion efficiency
reached 18.14%. The dopant-free PSC based on
CuTFSI organometallic complex reached respectable
PCE of 13.13%.
REFERENCES
[1] Wang R, Mujahid M, Duan Y, Wang ZK, Xue J, Yang Y. A review of perovskites solar cell stability. Adv. Funct.
Mater. 2019, 1808843.
[2] Chen J, Park NG. Inorganic Hole Transporting Materials for Stable and High Efficiency Perovskite Solar Cells.
J. Phys. Chem. C. 2018, 122 (25), 14039−14063.
[3] Sun L, Hua Y, Xu B, Liu P, Cheng M, et al. High Conductivity Ag-Based Metal-Organic Complexes as Dopant-
Free Hole-Transport Materials for Perovskite Solar Cells with High Fill Factor. Chem. Sci., 2016, 7, 2633.
Fig. 1. Structure of precursor P1
Fig. 2. Structure of Cu(TFSI)2-based
organometallic complex
34
O20
Optimized terahertz diffractive optical element for skin
cancer diagnosis
Mateusz Surma1, Paweł Komorowski2, Izabela Ducin1, Piotr Sobotka1, Elżbieta
Czerwińska3, Michał Walczakowski3 and Agnieszka Siemion1
1Faculty of Physics, Warsaw University of Technology, Koszykowa 75, Warsaw, 00662 Poland 2Institute of Microelectronics and Optoelectronics, Warsaw University of Technology,
Koszykowa 75, Warsaw, 00662 Poland 3Institute of Optoelectronics, Military University of Technology, Urbanowicza 2, Warsaw, 00908
Poland Email: [email protected]
Every year in Europe thousands of people die from diagnosed melanoma and therefore quick and early detection becomes crucial [1]. The aim of the T-SKIN project (Project financed by the National Center for Research and Development under the Lider programme) is to create diffraction based optical structures for examination of reflection from healthy skin and cancer tissues for effective detection of skin cancer. We assume using narrowband illumination having 0.48 mm wavelength corresponding to 0.52 THz.
This work describes combined THz diffractive optical structures designed for scanning systems detecting cancer tissues on human skin. The first part of the project concerns focusing the radiation into focal spot and further analysis of possible penetration depth of THz wave into skin layer. Thus, a diffractive optical element consisting of two parts – half focusing on and half collecting the radiation reflected from the sample – as shown in Fig. 1. The configuration assures small angle between incident and reflected waves along the normal to the sample. The structure (Fig. 1) was designed and optimized assuming plane wave illumination, thus, an optical setup with additional parabolic mirror is used. Optimization was performed using iterative algorithm to suppress the influence of asymmetrical phase distribution.
Optimized diffractive structure having two functions and consisting of two halves combined into one element were designed and experimentally verified. Our next goal is to create imaging setup using diffractive elements to make it compact and assure fast determination of registered image.
REFERNCES
[1]. The Melanoma, a white paper: Reshaping EU Healthcare for Melanoma Patients (Brussels, 2012) [2]. A. J. Fitzgerald, E. Pickwell-MacPherson and V. P. Wallace, “Use of finite difference time domain simulations and Debye theory for modelling the terahertz reflection response of normal and tumour breast tissue”, PLoS One, 9(7), e99291, 2014. [3]. I. Kašalynas, R. Venckevičius, L. Minkevičius, A. Sešek, F. Wahaia, V. Tamošiūnas, B. Voisiat, D. Seliuta, G. Valušis, A. Švigelj and J. Trontelj, “Spectroscopic terahertz imaging at room temperature employing microbolometer terahertz sensors and its application to the study of carcinoma tissues”, Sensors, 16(4), 432, 2016.
Fig. 1 The schematic representation of described setup (S
– source, D – detector, OT-DOE – Optimized THz DOE)
(left). Phase maps corresponding to structure focusing
incident radiation on the sample (middle) and structure
gathering reflection from the sample on the detector (right).
White color corresponds to 2π phase shift and black to 0.
35
O21
Oxidized SPIRO-MEOTAD stability investigation
E. Kasparavičius1, T. Malinauskas1, V. Getautis1
1 Faculty of Chemical Technology, Kaunas University of Technology, Radvilėnų pl. 19, Kaunas
Email: [email protected]
Population growth and ever-increasing energy consumption prompts new search for
cleaner and safer alternatives to fossil fuels and nuclear energy. One of the most attractive
alternatives is photovoltaic systems. Because of simple manufacturing and good performance
prospects perovskite solar cells received growing interest from research community. As a
result of rapid development in this field, perovskite photovoltaic systems have reached 23.7%
[1] efficiency.
Despite relatively high performance of perovskite solar cell (PSC), the current conditions
still do not meet the requirement for commercialization. There are three main stability issues
with PSCs: environmental (moisture and oxygen), photo and thermal stability. In addition,
selective contacts and additives in HTM can also have influence on stability [2,3] .
In this work the hole-transporting materials, like spiro-OMeTAD, have been investigated under
various conditions, such as thermal stress, in order to estimate overall lifetime and influence of
different additives and on perovskite surface. Overall morphological stability of the amorphous
state of spiro-OMeTAD has deteriorated rapidly under elevated temperature at 100 °C, and a
material’s change from amorphous to crystalline aggregate state. This is one of the main factors
leading to a rapid decline of device performance.
REFERNCES
[1] H.-S. Kim, A. Hagfeldt and N-G. Park, Morphological and compositional progress in halide perovskite solar
cells, Chem. Commun., 2019,55, 1192-1200
[2] X. Zhao and N.-G. Park. Stability Issues on Perovskite Solar Cells. Photonics 2015, 2, 1139-1151 p.
[3] T. Malinauskas., D. Tomkutė-Lukšienė, R. Sens, M. Daskeviciene, R. Send, H. Wonneberger, V. Jankauskas,
I. Bruder, and V. Getautis. Enhancing Thermal Stability and Lifetime of Solid-State Dye-Sensitized Solar Cells
via Molecular Engineering of the Hole-Transporting Material Spiro-OMeTAD. ACS Appl. Mater. Interfaces . 2015,
vol. 7( 21), 11107-11116 p.
36
O22
Optimization of AlGaN/GaN EdgeFETs for terahertz detection by optimization of ohmic contacts.
M. Dub1, M. Sakowicz1, P. Sai2,3,4, D. B. But2,3,4, P. Prystawko1, G. Cywiński2,3,
S. Rumyantsev2,3, W. Knap2,3,5
1 Institute of High Pressure Physics PAS, ul. Sokołowska 29/37, 01-142, Warsaw, Poland 2 Center for Terahertz Research and Applications (CENTERA), Institute of High Pressure
Physics PAS, ul. Sokołowska 29/37, 01-142, Warsaw, Poland 3 CEZAMAT, Warsaw University of Technology, 02-822, Warsaw, Poland
4 V.Ye. Lashkaryov Institute of Semiconductor Physics NAS of Ukraine, ISP NASU Kyiv, Ukraine
5 Laboratoire Charles Coulomb, University of Montpellier and CNRS UMR 5221, 34950 Montpellier, France
Email: [email protected]
Field-effect transistors (FETs) can act as terahertz (THz) detectors or emitters [1]. Signal
and cut-off frequency of THz FET detection depend on the RC product (C is the gate capacitance
and R represent the Ohmic losses).
In order to reduce the capacitance we fabricated AlGaN/GaN FET with two gates that are
located along the edges of the channel and that are contacted directly to the two-dimensional
electron gas (2DEG) [2], thus forming Schottky contact between the gate metal and the 2DEG.
The area of each Schottky gate in this kind of the transistor (EdgeFETs) is extremely small and
is within the range of (1-4)x10-13cm2 depending on the gate width. With help of two lateral gates
we are able to narrow the channel and allow propagation of plasma waves only in one direction.
This should lead to resonant THz detection [2]. In order to reduce the Ohmic losses we used
regrown ohmic drain and source contacts (Fig.1b).
-25 -20 -15 -10 -5 01n
10n
100n
1µ
10µ
Gate Voltage (V)
Cu
rre
nt
(A) Ids_Regrowth
Igs_Regrowth
Ids_no Regrowth
Igs_no Regrowth
Vds=50mV
c)
Fig. 1. EdgeFETs without regrowth a) and with regrowth b). c) Transport characteristics of EdgeFETs and gate
leakage current.
The EdgeFETs contact resistance was significantly improved by regrowth as shown in
Fig. 1c. At the same time both samples show similar threshold slope. Accordingly to Ref. [3] this
will result in much higier detection signal registered in the case of sample with regrown contacts.
As a result we show great improvement in the EdgeFETs quality, which approach us towards
resonant THz detection.
[1] M. Dyakonov and M. Shur, IEEE Trans. Electron Devices 43, 380 (1996)
[2] P.Sai, et al., Semicond. Sci. Technol. 34 (2019) 024002
[3] M. Sakowicz, et al., JOURNAL OF APPLIED PHYSICS 110, 054512 (2011)
37
O23
Carbon dimer defect as the origin of the 4.1 eV
luminescence in hexagonal boron nitride Mažena Mackoit-Sinkevičienė1, Marek Maciaszek2, Chris G. Van de Walle3,
Audrius Alkauskas1
1Center for Physical Sciences and Technology (FTMC), Vilnius LT-10257, Lithuania
2Faculty of Physics, Warsaw University of Technology, Koszykowa 75, 00-662 Warszawa,
Poland
3Materials Department, University of California, Santa Barbara, California 93106-5050, USA
Hexagonal boron nitride (hBN) has attracted
considerable interest over the past decade as a versatile
material that can be used in a number of applications due
to its unique combination of physical and chemical
properties. In as-grown samples bright luminescence with
a clear zero-phonon line (ZPL) at 4.1 eV is often observed
[1]. The emission is believed to be due to defects. The line
can act as a source of single photons [2]. Despite a
ubiquitous nature of the 4.1 eV emission, the chemical
nature of the defect, which responsible for luminescence,
has not been established, even though the involvement of
carbon is often assumed [3].
Based on hybrid functional first-principles calculations
we propose that the neutral carbon dimer defect, CBCN, is responsible for the observed
emission. We find that neutral CBCN is the most stable for Fermi levels throughout most of the
band gap, with a formation energy of 2.2 eV. We find that there is a range of atomic chemical
potentials and Fermi levels where the dimer is the most stable defect, indicating that it will
form whenever carbon is present.
Carbon dimer accounts for all known experimental facts about the 4.1 eV luminescence:
the involvement of carbon, the energy of the transition, the very short radiative lifetime, and
moderate electron-phonon coupling. All these results allow us to propose the CBCN as a
defect responsible for the 4.1 eV emission in hBN. In fact, carbon dimer defects have been
indeed observed in transmission electron microscopy experiments on hBN [4].
REFERENCES
[1] L. Museur, E. Feldbach, and A. Kanaev, Phys. Rev. B 78, 155204 (2008). [2] R. Bourrellier et al., Nano Lett. 16, 4317 (2016). [3] T. Taniguchi, and K. Watanabe, J. Cryst. Growth 303, 525 (2007).
[4] O. L. Krivanek et al., Nature 464, 571 (2010).
Fig. 1. Formation energy vs. Fermi level for CB, CN, and CBCN defects in various charge states under (a) N-poor and (b)
N-rich conditions.
38
Poster presentations
39
P01
Bismide technology for temperature independent IR
range semiconductor laser diodes
Simona Pūkienė1, Jan Devenson1, Vladimir Agafonov1, Algirdas Jasinskas1,
Bronislovas Čechavičius1, Karolis Stašys1, Renata Butkutė1
1Center for Physical Sciences and Technology, Sauletekio av. 3, LT-10257, Vilnius, Lithuania.
Email: [email protected]
In recent years, promising results have been achieved in the development of GaAsBi
quantum structure growth technology for optoelectronic systems, especially for lasers.
Electrically pumped laser diode containing by molecular beam epitaxy (MBE) grown multiple
quantum well (QW) structure of GaAsBi with 6% 4Bi in active area and operating at room
temperature, was demonstrated by Butkutė et al. in 2014 [1]. Adding even a small amount of
Bi to AIII - BV semiconductor lattice, such as GaAs, reduces Auger recombination in the IR
wavelength range [2]. In addition, Eg has been shown to
have weak temperature dependency in bismide
compounds.
In this work, GaAsBi QW structures were grown
using the MBE method on semiconducting GaAs (100)
substrates. First, the MBE growth conditions of GaAsBi
QW with AlGaAs barriers were optimized by varying the
flux ratio As2 / Ga in the range of 1 - 1.1. Low
temperature growth (425 C) was used to introduce Bi to
GaAs lattice and prevent surface segregation. The
optical measurements showed that the intensity of the
photoluminescence (PL) gradually decreases with
increase of Bi concentration. PL temperature dependent
measurements demonstrated the weak energy peak
shift over the whole temperature range of 3 to 300 K (Fig.
1).
Finally, laser diode structures were grown under optimal growing conditions onto n-GaAs
(100) substrate. The n-type and p-type AlGaAs waveguide layers were 1.5 µm thick and doped
up to 1x1018 cm-3 by silicon and beryllium, respectively. GaAsBi / AlGaAs laser diode geometry
was formed using UV photolithography. The diodes were characterized by current-voltage (I-
V) and current-power (I-P) dependencies. Laser diodes with active GaAsBi / AlGaAs region
showed electroluminescence at 1.09 μm.
REFERNCES
[1] R Butkute, A Geižutis, V Pačebutas. B Čechavičius, V Bukauskas, V Kondrotas, P Ludewig, K Volz, A Krotkus;
Electronics Letters. 50. 1155–1157. 10.1049/el.2014.1741, 2014
[2] K. Alberi, J. Wu, W. Walukiewicz, K. M. Yu, O. D. Dubon, S. P. Watkins, C. X. Wang, X. Liu, Y.- J. Cho, and
J. Furdyna.;. Phys. Rev. B, 75:045203, 2007
0,9 1,0 1,1 1,2 1,3 1,4 1,510
0
101
102
103
3 K
20 K
40 K
60 K
100 K
120 K
140 K
160 K
180 K
200 K
220 K
240 K
260 K
280 K
300 K
Inte
nsity A
.U.
Photon energy, eV
Fig. 1 Photoluminesce vs temperature
dependence of GaAsBi quantum well
based diode structure.
40
P02
Reactive magnetron sputtering of scandium oxide films
for various applications.
Alexandr Belosludtsev1, Robert Mroczyński2, Naglis Kyžas1, Lukas Ceizaris1, Yuri
Yakimov3, Sandra Stanionytė1, Martynas Skapas1, Kęstutis Juškevičius1
1Center for Physical Sciences and Technology, Savanorių ave. 231, 02300 Vilnius, Lithuania. 2 Institute of Microelectronics and Optoelectronics, Warsaw University of Technology,
Koszykowa 75, 00662 Warsaw, Poland. 3 National University of Science and Technology “MISIS”, Leninsky prospect 4, 119049
Moscow, Russia.
Email: [email protected]
Firstly [1], the correlation between stoichiometry and
properties of scandium oxide films prepared by reactive
magnetron sputtering was investigated. The optimized
deposition conditions were found. It was shown that the
higher refractive index, the higher optical bandgap, and the
lower extinction coefficient as stoichiometric films are
concerned. It was found that films were with the cubic
phase structure.
Secondly [2], the effect of annealing on structure,
optical, mechanical and electrical properties of
stoichiometric scandium oxide films (Sc2O3) was studied. It
was found that annealing results in the decrease of extinction coefficient, and slightly decrease
of the refractive index. It was shown, that by reactive magnetron sputtering it is possible to
manufacture scandium oxide films with advanced mechanical properties. Both, as-deposited
and annealed scandium oxide films can be characterized by the cubic phase, high hardness
(up to 19 GPa) and resistance to high-load indentation (up to 1000 mN). Moreover, the
electrical characterization of fabricated MIS structures with Sc2O3 as the gate-dielectric
material revealed better electrical properties, such as lower frequency dispersion of C-V
characteristics and lower effective charge values, as well as slightly higher electric field
intensity that results in the dielectric layer’s breakdown. The investigated dielectric films might
be used as chemically stable, hard, resistive to cracking, highly transparent insulating films.
The findings make the investigated scandium oxide films a promising material for various
applications in optics, optoelectronic, and electronic semiconductor structures.
REFERNCES
[1] A. Belosludtsev, K. Juškevičius, L. Ceizaris, R. Samuilovas, S. Stanionytė, V. Jasulaitienė, S. Kičas; Appl.
Surf. Sci. 427 (2018) pp. 312-318.
[2] A. Belosludtsev, Y. Yakimov, R. Mroczyński, S. Stanionytė, M. Skapas, D. Buinovskis, N. Kyžas; Phys.
Status Solidi A accepted (2019), doi.org/10.1002/pssa.201900122
41
P03
Reflectivity of the n-type GaN with shallow surface
gratings
Vytautas Janonis1, Pawel Prystawko2, Krzysztof Gibasiewicz2, Jacek Kacperski2,
Irmantas Kašalynas1 1Center for physical sciences and technology, CPST, Vilnius, Lithuania
2Institute of High Pressure Physics Polish Academy of Sciences, UNIPRESS, Warsaw, Poland
Periodic metal and dielectric gratings and micro/nano structures on the materials surface
have been widely considered for sub-wavelength light manipulation and confinement of
electromagnetic fields to achieve a large enhancement of linear and nonlinear optical
properties[1]. Periodic irregularities on the surface of a polar semiconductor are used to
provide coupling between the incoming light and Surface Phonon Polariton (SPhP)
resonances. The SPP modes demonstrate higher quality factor as compared to the surface
plasmon-polariton modes provided by the metal gratings and are promissing in the
development of novel optical components.[2].
In this work periodic structures on the surface of n-type GaN semiconductor were
investigated. The surface relief gratings with properly selected the grove depth, periodicity,
and filling factor were used for the excitation of Surface Phonon Plasmon Polariton (PhPP)
modes in n-GaN. Measured reflectivity spectra revealed the strong field confinement and
coherent PhPP mode excitations.
The different periodicity gratings were
produced on n-type GaN at UNIPRESS and the
samples were investigated at CPST. The
reflectivity spectra were calculated using the
Rigorous Coupled Wave Analysis (RCWA)
program. Results for the sample with shalow
relief grating are shown in the Fig.1. Good
agreement between the experimental and the
theoretical data was found. And the field
localization was observed only on the sample
surface. Moreover, the resonance position in
the reflectance spectrum was found to be
dependent on the depth, width, and periodicity
of the grooves [3].
REFERNCES
[1] J. B. Khurgin, Relative merits of phononics vs. plasmonics: the energy balance approach, Nanophotonics
7(1), pp. 305–316 (2018).
[2] J. D. Caldwell, et. al., LowLoss, Extreme Subdiffraction Photon Confinement via Silicon Carbide Localized
Surface Phonon Polariton Resonators, Nano Lett., vol. 13, pp. 3690–3697 (2013).
[3] V. Janonis, P. Prystawko, K. Gibasiewicz, J. Kacperski, I. Kašalynas, Investigation of the reflectivity spectra
of n-type GaN semiconductor with surface relief gratings, Proc. of 44nd International Conference on Infrared,
Millimeter, and Terahertz Waves (IRMMW-THz), Paris, France (2019).
400 600 800 1000 1200 14000.0
0.2
0.4
0.6
0.8
1.0
R
(cm-1)
FTIR measurement
RCWA theory
Fig. 1 Measured and calculated reflectivity spectra of
n-GaN with the grating of 11 m periodicity, 50 % filling
factor, and 1 m grove depth. Inset shows the magnetic
field plot at the resonant frequency.
42
P03
Modeling of pump-probe spectra at high excitation
intensity
Vytautas Bubilaitis, Darius Abramavičius
Chemical physics institute, Vilnius university, Saulėtekio av. 3, Vilnius
Email: [email protected]
Polarization of an arbitrary order can be calculated by expanding density operator in powers
of interaction with the excitation field [1]. The lowest order nonlinear optical signal that is
generated in isotropic media is third order. At this order, the one exciton states and excited
state energy transfer can be observed.
When excitation dynamics are followed at the lowest (third) power of interaction to excitation
field, dependence on excitation intensity is often ignored. This dependence can be important
as laser pulse intensity is one of parameters that is tuned for better signal-noise ratio. At high
excitation intensity exciton-exciton annihilation (EEA) takes place [2].
Nonlinear exciton equations (NEE) [3] were used for calculations in this work. We expanded this
equation system with terms that are higher than third order and added secular Redfield
relaxation and phenomenological EEA terms. Then Pump-probe spectra were calculated at
various excitation intensities and delay times with these equations (Fig. 1).
Fig. 1 Calculated pump-probe spectra of molecular dimer at low (left) and high (right) excitation intensities.
Legend shows delay times between pulses.
Calculations show that at low excitation intensity the pump-probe spectra shows relaxation
and at high excitation intensity nonexponential decay is observed which can be associated
with EEA. Thus our expanded equation behave as should be expected.
REFERENCES
[1] L. Valkunas, D. Abramavicius, and T. Mančal, Molecular Excitation Dynamics and Relaxation (Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA, 2013) [2] J. Chmeliov, J. Narkeliunas, M. W. Graham, G. R. Fleming, and L. Valkunas, Nanoscale, 2016, 8, 1618–
1626. [3] V. Chernyak, W. M. Zhang, and S. Mukamel, J. Chem. Phys., 1998, 109, 9587–9601.
Modeling of pump probe spectra at high excitation intensity
Vytautas Bubilaitis, Darius Abramavičius
Chemical physics institute, Vilnius university, Saulėtekio av. 3, Vilnius
Email Vytautasbubilaitis gmai.com
Polarization of an arbitrary order can be calculated by expanding density operator in
powers of interaction with the excitation field [1]. The lowest order nonlinear optical signal that
is generated in isotropic media is third order. At this order, the one exciton states and excited
state energy transfer can be observed.
When excitation dynamics are followed at the lowest (third) power of interaction to
excitation field, dependence on excitation intensity is often ignored. This dependence can be
important as laser pulse intensity is one of parameters that is tuned for better signal noise ratio.
At high excitation intensity exciton exciton annihilation (EEA) takes place [2].
Nonlinear exciton equations (NEE) [3] were used for calculations in this work. We
expanded this equation system with terms that are higher than third order and added secular
Redfield relaxation and phenomenological EEA terms. Then Pump probe spectra were
calculated at various excitation intensities and delay times with these equations (Fig. 1).
Calculations show that at low excitation intensity the pump probe spectra shows
relaxation and at high excitation intensity nonexponential decay is observed which can be
associated with EEA. Thus our expanded equation behave as should be expected.
REFERENCES
[1] L. Valkunas, D. Abramavicius, and T. Mančal, Molecular Excitation Dynamics and Relaxation (Weinheim,
Germany Wiley VCH Verlag GmbH Co. KGaA, 2013)
[2] J. Chmeliov, J. Narkeliunas, M. W. Graham, G. R. Fleming, and L. Valkunas, Nanoscale, 2016, 8, 1618 1626.
[3] V. Chernyak, W. M. Zhang, and S. Mukamel, J. Chem. Phys., 1998, 109, 9587 9601.
600 400 200 0 200 400 600
, cm 1
1.0
0.5
0.0
0.5
OD,a.u.
10 10
0.0 ps
0.2 ps
0.5 ps
2.0 ps
5.0 ps
20.0 ps
600 400 200 0 200 400 600
, cm 1
40
30
20
10
0
OD,a.u.
0.0 ps
0.2 ps
0.5 ps
2.0 ps
5.0 ps
20.0 ps
Fig. 1 Calculated pump probe spectra of molecular dimer at low (left) and high (right) excitation intensities.
Legend shows delay times between pulses.
43
P05
Terahertz pulse emission from GaInAsBi
R. Norkus1, V. Pačebutas1, S. Stanionytė1, A. Bičiūnas1, A. Urbanowicz1 and
A. Krotkus1
1 Center for Physical Sciences and Technology, Saulėtekio av. 3, LT-10257, Vilnius, Lithuania
Email: [email protected]
Generation of Terahertz pulses by photoconductive antennas (PCA) is a commonly used
technique. Main PCA advantages are compactness and versatility. THz radiation pulses are
presently widely applied to study physical properties of materials, identification of chemicals,
and for nondestructive testing using time-domain spectroscopy (TDS) techniques. These
applications could benefit if inexpensive and maintenance-free fibre laser systems could be
used in THz TDS systems. These lasers operate at 1 μm and longer wavelengths. Recently
PCA with bismuth (Bi) on GaAs substrate for 1 μm and 1550 μm were demonstrated [1,2]. The
latter was quaternary with 20% In and 10 % Bi with large (3%) lattice mismatch on GaAs
substrate. In this work quaternary In0,53Ga0,47As0,94Bi0,06 layer was grown on InP substrate and
lower lattice mismatch (0,3 %) and bandgap (up to 0,4 eV) were achieved.
6 % (I401) and 1,8 % (I405)
Bi content samples were
characterized by optical pump
THz probe and X-ray diffraction
techniques. Samples had carrier
lifetime of few picoseconds and
were fully strained. THz excitation
spectra of I401 unbiased layer and
fabricated as PCA were measured
(Fig. 1). PCA showed sensitivity to
optical pulses with more than 2 μm
wavelength, which could be used
in THz - TDS systems for novel
thulium or holmium fibre lasers.
THz pulses obtained when
using Er-doped fibre laser for the
photoexcitation were comparable
with those observed in other
emitters used for THz-TDS
systems.
REFERNCES
[1]. V. Pačebutas, A. Bičiūnas, S. Balakauskas, A. Krotkus, G. Andriukaitis, D. Lorenc, A. Pugžlys, and A.
Baltuška, Appl. Phys. Lett., 97, 031111 (2010).
[2]A. Urbanowicz, V. Pačebutas, A. Geižutis, S. Stanionytė, and A. Krotkus, AIP Advances 6, 025218 (2016).
0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.20
1
2
3
4
5
6
7
8 I405 PCA
p-InAs
I401 PCA
I401
TH
z si
gn
al a
mp
litu
de,
a.u
.
Photon energy, eV
Fig. 1 . THz excitation spectra of the GaInAsBi epitaxial layer with 6%
Bi (layer i401, empty points) and PCA fabricated from that layer (full
points) biased cw at 50 V voltage. THz pulse amplitudes emitted from
InAs layer (square) and PCA fabricated from GaInAsBi with 1.8% Bi
(layer i405, red diamonds) excited by 2 μm and 1.5 μm optical pulses
are shown for comparison.
44
P06
Photophysical properties of dimethildihydropyrene
derivatives
Ignas Čiplys1, Irena Kulszewicz-Bajer2, Renata Karpicz1
1Center for Physical Sciences and Technology, Sauletekio ave. 3, LT-10257 Vilnius, Lithuania 2Warsaw University of Technology, ul. Noakowskiego 3, 00-664 Warszaw, Poland
Email: [email protected]
Dimethildihydropyrenes (DHP,
closed ring form) are one of the most
popular photochromic compounds
class that could be reversibly
converted into cyclophanediene (CPD,
opened ring form) when exposed to
visible light (above 480nm). This kind
of photochemical reactions leads to
changes in physical properties such as
absorption and fluorescence spectra.
DHP substances could be applied in wide range of areas such as organic electronics, for
example single molecule memory elements, and biology – diagnostics, control of metabolic
reactions. To achieve even more suitable physical properties for different applications, DHP
molecules could be modified by adding substitutes. However, the most common problems of
DHP compounds are stability, conversion efficiency and thermal back reaction. To solve this
problem, there is a need of deeper understanding of processes appearing during DHP↔CPD
photochemical reactions.
New derivatives of DHP were synthesized and its optical properties of both CPD and
DHP forms as well as excited state dynamic were investigated in the solutions. We focus on
the emissive properties of DHP derivatives with the possibility to switch them between
fluorescent and non-fluorescent states. It was found out, that only antisymmetric DHP shows
good photochromic properties. During the first 100-300 ps after excitation under visible light
the closed-ring DHP isomer were opened. Reverse transformation took place through
intermediate stage during several nanoseconds.
VIS
Closed ring form Opened ring form
UV, °C
45
P07
Performance of the Planar AlGaN/GaN Bow-Tie Diodes
Developed for Terahertz Detection
Justinas Jorudas1, Liudvikas Subačius1, Gintaras Valušis1, and Irmantas
Kašalynas1
1THz photonics laboratory, Optoelectronics department, Center for Physical Sciences and
Technology (FTMC), Saulėtekio av. 3, LT-10257, Vilnius, Lithuania
Email: [email protected]
A compact and sensitive terahertz (THz) detector with a fast response time is highly
desired for the THz imaging systems operating at the room temperature. Unique physical
properties of gallium nitride (GaN) have triggered a breakthrough for the next generation of
the THz electronic components [1–3].
In this work, performance of the AlGaN/GaN bow-tie (BT) diodes developed for THz
detection is reported. The BT diodes were developed on two Al0.25Ga0.75N/GaN high electron
mobility transistor (HEMT) structures grown on semi-insulating SiC substrates. HEMT
structures slightly differed in the 2DEG sheet resistance values: about 430 Ω/sq. and 330
Ω/sq. for the samples S1 and S2, respectively. The sub-THz performance was studied
considering the variation of the apex width of the BT diode. Response was studied at
discrete microwave (9-11 GHz) and sub-THz frequencies (150-600 GHz). The current
voltage characteristics measured in dc- and pulsed regimes were also investigated. The
results demonstrated a new potential of AlGaN/GaN HEMT structures for applications in sub-
THz frequencies.
(a) (b)
Fig. 1 (a) Setup of sub-THz detection experiment; (b) Responsivity R of the AlGaN/GaN BT diodes as a
function of apex width at a frequency of 150 GHz.
ACKNOWLEDGEMENT
This research was supported by the Research Council of Lithuania (Lietuvos mokslo taryba)
under the “TERAGANWIRE” project (Grant no. S-LL-19-1).
REFERENCES
[1] P. Sai et al., Semicond. Sci. Technol. 34, (2019) pp. 024002. DOI: 10.1088/1361-6641/aaf4a7 [2] M. Bauer et al., IEEE Trans. Terahertz Sci. Technol. 9, (2019) pp. 430-444. DOI:
10.1109/TTHZ.2019.2917782 [3] J. Jorudas et al., 44nd Int. Conf. Infrared, Millimeter, Terahertz Waves (Paris, 2019).
46
P08
Mechanical Properties of 17-4PH Stainless Steel Parts
Produced by DMLS
Ada Steponavičiūtė, Aušra Selskienė, Jurijus Tretjakovas, Genrik Mordas
Department of Laser Technologies, Center for Physical Sciences and Technology,
Savanoriu ave. 231, Vilnius, Lithuania
Email: [email protected]
Additive manufacturing (AM) is a type of
manufacturing technologies where material is
added layer upon layer in order to produce an
object. This quality lets additive manufacturing
stand out from traditional subtractive
manufacturing technologies and opens up
possibilities to create geometrically complex
objects.
The most widely applied additive
manufacturing technology for metal part
production is a powder-based AM technology
called Direct Metal Laser Sintering (DMLS)
where metal powder particles are fused
together by a laser beam. Microstructure and
mechanical property characterization with
consequent DMLS process optimization helps
to overcome the weaknesses and extend its
area of use [1].
Our study concentrated on the investigation of the mechanical properties of produced
17-4PH (stainless steel) parts using DMLS. The effect of the DMLS process parameters (laser
power, scanning speed and energy density) on the ultimate strength, yield strength and
Young’s modulus was determined (Fig. 1). We showed an evolution of the microstructure. The
detected defects were classified. This study allowed to determine the optimal regimes of
DMLS for SS 17-4H and describe mechanical properties of the produced parts as well as
helped to show future possibilities of DMLS development.
REFERNCES
[1] M.D.Viramgama, M.C.Karia. Study and investigation of influence of process parameters for selective laser
melting. IJEDR4(1),pp. 578-585 (2016).
Fig. 1 Mechanical properties of specimens produced
with a constant scanning speed.
47
P09
Modeling of Molecular Excitation Relaxation in Thermal
Environment by Time-dependent Variational Approach
with Superposition of Davydov D2 Ansätze
Mantas Jakučionis, Darius Abramavičius
Institute of Chemical Physics, Vilnius University, Saulėtekio av. 9, III bld., Vilnius
Email: [email protected]
Theoretical description of molecular excitation dynamics is a complex quantum mechanical
problem, because interactions between all constituent parts of a molecule have to be
considered at an ab-initio level. Therefore, complex quantum chemistry methods exist, which
are capable of computing molecular excited state energy levels, transition dipole moments,
vibrational mode frequencies, oscillation strengths and other microscopic molecule
properties.
A problem of excitation energy relaxation involves degrees of freedom (DOF) beyond an
isolated molecule, thermal fluctuations of molecule environment must be also treated. These
are essential for thermodynamically correct excitation energy relaxation modeling. Due to
e.g. internal-conversion (IC), a big portion of excitation energy is quickly transformed into
molecular vibrational energy (heat), which ought to redistribute among all vibrational degrees
of freedom, including those of environment, and, eventually, thermodynamic equilibrium
should be restored. Thermal energy redistribution (TER) processes are important in both
natural complexes and artificial structures, but due to a large number of interacting DOFs,
modeling becomes a challenge. It has been recently demonstrated that this approximation is
not accurate for carotenoids and TER processes have to be considered simultaneously [1].
We have created a general purpose molecular IC model where molecular DOFs are treated
exactly, while states of environment vibrational DOFs are represented by a superposition of
Davydov D2 Ansätze (sD2). A set of equations was derived to calculate the model time
evolution. Also, algorithms for considering environment DOFs at a finite temperature and
their thermalization, when using sD2 wavefunction, were proposed. To validate algorithms,
we have considered a model system and have shown that they are capable of representing
environment DOFs at a finite temperature and are able to maintain their temperature, even
when environment is under the influence of a molecule.
We have also performed simulations of β-carotene S2→S1 IC with simultaneous TER
processes, using the constructed IC model, and have found that β-carotene IC occurs faster,
when β-carotene nearest environment temperature increases.
REFERNCES
[1] V. Balevičius Jr, T. Wei, D. Di Tommaso, D. Abramavicius, J. Hauer, T. Polívka, C.D.P. Duffy, The full
dynamics of energy relaxation in large organic molecules: from photo-excitation to solvent heating, Chem. Sci.
10 (18), 4792–4804 (2019).
48
P10
New Fluorene-Based Hole Transporting Organic
Semiconductors for Efficient Hybrid Solar Cells
Aistė Ilčiukaitė1, Marytė Daškevičienė1, Egidijus Kamarauskas2, Vygintas
Jankauskas2, Vytautas Getautis1
1Department of Organic chemistry, Kaunas university of technology, Radvilėnų pl. 19,
Kaunas. 2 Institute of Chemical Physics Vilnius University, Lithuania
Solar energy is the most powerful source of renewable energy. Properly refined Solar
cells can fully meet society's energy needs. Currently, silicon Solar elements (SEs) is mainly
used, but it is expensive and complicated to produce. However, the use of organic and
hybrid SEs is growing rapidly. The efficiency of perovskite Solar cells (PSCs) have already
exceeded
22% [1]. These elements are characterized by simple construction and cheap raw materials.
While PSCs have achieved record efficiencies (3.8% to 22.7%) over the last five years [2],
there are still several obstacles to their commercialization. In particular the rather expensive
ptype organic semiconductor (spiro-OMeTAD) used for hole transport is synthesized by a
five step reaction, and also the unresolved stability problem of these devices. Currently,
there is an intense search for more simple synthesis methods to produce cheaper and
efficient semiconductors. The aim of this work was to synthesize fluorene-based
semiconductors, that could be used as a hole transporting material in PSCs, and estimate
the influence of the length of alkylchains on the properties of new compounds.
1. Fig. New fluorene-based compounds.
During this work new fluorene class compounds were obtained. From investigated
optical properties, it is evident that all compounds have two maximum absorption peaks
between 303 and 377 nm. All target substances are amorphous and have thermal stability
greater than 400 °C. It has been observed that ionization potential and hole drift mobility of
compounds is favorable for the use in Solar cells as positive charge carriers.
REFERENCES
[1] M. Saliba, S. Orlandi, et al.; A molecularly engineered hole-transporting material for efficient
perovskite solar cells 1 (2016) pp. 1-7. [2] M. Saliba, J.P.C. Baena, et. al.; Perovskite Solar Cells: Form the Atomic Level to Film Quality and
Device Performance, 2018 pp. 2554–2569.
49
P11
Peculiarities of laser-processed photonic crystal-based
waveguides for terahertz and sub-terahertz frequencies
Vincas Tamošiūnas1,2, Simonas Indrišiūnas3, Linas Minkevičius1,
Gediminas Račiukaitis3, Irmantas Kašalynas1 and Gintaras Valušis1
1Department of Optoelectronics, Center for Physical Sciences and Technology,
Saulėtekio Ave. 3, LT-10257 Vilnius, Lithuania. 2Institute of Photonics and Nanotechnology, Vilnius University,
Saulėtekio Ave. 3, LT-10257 Vilnius, Lithuania. 3Department of Laser Technologies, Center for Physical Sciences and Technology,
Savanorių Ave. 231, LT-02300 Vilnius, Lithuania.
Email: [email protected]
Terahertz integrated electronic and hybrid
electronic - photonic systems have undergone significant
development during the past decade, thus opening new
sensing, imaging and communication application
possibilities, enabled by new architectures rather than the
development of single devices [1]. Photonic crystal-based
waveguides and resonant cavities can be efficiently
employed for beam steering and sensing applications in
such systems [2].
In this paper, we report on properties and
peculiarities of photonic crystal (PC) based waveguides
manufactured using laser ablation techniques. These
fabrication techniques possess remarkable flexibility to
produce complex three-dimensional shapes, such as
multi-level Fresnel lenses [3]. However, beam delivery peculiarities require special attention
when designing deep and narrow structures, such as anti-reflective and phase-correcting
metamaterial layers [4].
Comprehensive series of numerical simulations were applied to optimise PC structures
for laser processing of highly resistive silicon (HR-Si) wafer for target frequencies of 0.15 THz
and 0.3 THz. Test structures were ablated to confirm the validity of the proposed design.
Image of one such structure is presented in Fig. 1. Results of our investigations revealed the
broader beam confinement control possibilities of laser – processed waveguides in
comparison with ones obtained by reactive ion etching techniques.
REFERENCES
[1] K. Sengupta, T. Nagatsuma, and D. M. Mittleman; Nature Electronics 1 (2018) pp. 622–635. [2] O. Kazuma, K. Tsuruda, S. Diebold, S. Hisatake, M. Fujita, and T. Nagatsuma; J. Infrared Milli. Terahz.
Waves 38 (2017) pp. 1085–1097. [3] S. Indrišiūnas, H. Richter, I. Grigelionis, V. Janonis, L. Minkevičius, G. Valušis, G. Račiukaitis,
T. Hagelschuer, H.-W. Hübers, and I. Kašalynas; Opt. Lett. 44 (2019), pp. 1210–1213. [4] M. Tamošiūnaitė, S. Indrišiūnas, V. Tamošiūnas, L. Minkevičius, A. Urbanowicz, G. Račiukaitis,
I. Kašalynas, G. Valušis; IEEE Trans. Terahertz Sci. Technol. 8 (2018), pp. 541–548.
Fig. 1 SEM (scanning electron
microscope) image of laser-processed
PC-based waveguide.
50
P12
p-Type Fluorene-Based Organic Semiconductors for
Efficient Perovskite Solar Cells
Šarūnė Daškevičiūtė1, Nobuya Sakai2, Marius Franckevičius3, Marytė
Daškevičienė1, Artiom Magomedov1, Egidijus Kamarauskas4, Vygintas
Jankauskas4, Henry Snaith2, Vytautas Getautis1
1Department of Organic Chemistry, Kaunas University of Technology, Lithuania. 2Clarendon Laboratory, Department of Physics, Oxford University, United Kingdom.
3Center for Physical Sciences and Technology, Lithuania. 4 Institute of Chemical Physics Vilnius University, Lithuania
Solid-state organic hole transporting materials (HTMs) are one of the important
components of the perovskite solar cells (PSCs). Spiro-OMeTAD is the most popular choice
for the HTM layer, and is used for the majority of the state-of-the-art PSC devices. However,
it is not only quite expensive but also shows unsatisfactory longterm stability due to oxidative
doping process and slow morphological degradation [1].
In this work, novel small-molecule HTMs were synthesized in three-step synthetic route,
starting from simple fluorene derivatives (Fig.1).
Figure 1. Structures of fluorene-based HTMs V1050 and V1061.
PSCs of planar configuration, employing V1050 HTM showed a high power conversion
efficiency of 18.3%, which is comparable to the 18.9% efficiency, obtained in the same
device configuration, only using Spiro-OMeTAD as a HTM. In addition, devices with V1050
and V1061 showed better stability in comparison to Spiro-OMeTAD based devices. Aging
test was performed on a non-encapsulated devices under uncontrolled humidity conditions
(relative humidity around 60%) in the dark and under continuous full sun illumination.
Overall, we believe that the V1050 can be a usefull alternative HTM to Spiro-OMeTAD for
perovskite solar cells, thus bringing PSCs closer to commercial production.
REFERENCES
[1] Z. Li, Z. Zhu, C. C. Chueh et al., Facile Thiol‐Ene Thermal Crosslinking Reaction Facilitated Hole‐Transporting
Layer for Highly Efficient and Stable Perovskite Solar Cells, Adv. Energy Mater. 1601165 (2016).
51
P13
Development of AlGaN cladding layer for GaN second
harmonic generation structure
Marek Kolenda1, Darius Kezys2, Arūnas Kadys1, Tadas Malinauskas1, Raimondas
Petruškevičius2 and Roland Tomašiūnas1
1 Institute of Photonics and Nanotechnology, Vilnius University, Saulėtekio ave. 3, LT-10257,
Vilnius, Lithuania 2 Department of Laser Technology, Center for Physical Sciences and Technology, Savanorių pr.
231, LT-02300, Vilnius, Lithuania
Email: [email protected]
In recent years, quite considerable amount of research has been focused on GaN as a
novel material for nonlinear optics and photonics. A unique combination of i direct band gap,
large transparency window and high second order nonlinearity makes GaN an interesting
candidate for nonlinear optics [1]. In addition, GaN films can further be structured to fabricate
waveguides, microrings, microdiscs and photonic crystal nanocavities for light conversion
applications [2,3].
Efficient frequency conversion requires a phase-matching condition to compensate for
material dispersion. Phase matching can be achieved by exploiting the birefringence exhibited
in anisotropic crystals or artificial structures. Quasi-phase-matching (QPM) utilizes spatially
periodic modulation of nonlinear coefficients and has achieved great success due to its
versatility in material choice and pump frequency range [4]. Other phase-matching methods,
such as modal-dispersion phase matching (MDPM) have been achieved in single-waveguide
structures [reiketu citavimo]. Looking forward extending methods like coupling compensation-
quasi-phase-matching (C-QPM) [reiketu citavimo] are foreseen, also for GaN.
In this work, we present modeling, growth results and ideas how to achieve structures
for second harmonic generation by using QPM and MDPM phase matching methods.
Modeling results present that IInd harmonic conversion efficiency is much greater using two
polarity GaN layers than only one. Growth parameter optimization of AlGaN layers on AlN was
performed using Aixtron Close-Coupled-Showerhead 3x2 MOCVD reactor. Substantial work
was performed to align the overgrown AlGaN layer quality with the underneath grown and
annealed AlN layer. Al concentration in AlGaN layers was 65% ÷ 67%, estimated using X-ray
diffraction (XRD). AlGaN layer serves as a cladding layer for GaN waveguiding layer, because
of smaller refractive index for AlGaN than GaN. Surface morphology and roughness
investigations of AlGaN layer performed by Atomic Force Microscopy, resulted the smoothest
surface when grown at high temperatures (about 1130oC) on the optimized AlN layer.
Discussion on structure preparation for second harmonic generation will follow the
presentation.
Acknowledgements: This work was funded by SMART 01.2.2-LMT-K-718 project.
REFERNCES
[1] N. A. Sanford, et al. J. Appl. Phys.97(5), 053512 (2005)
[2] M. Gromovyi, et al. Opt. Exp. 25, 19 (2017)
[3] I. Roland et al. Sci. Rep. 6, 34191 (2016)
[4] Po Dong, et al. Opt. Exp. 14, 6 (2006)
52
P14
Synthesis and investigation of new organic
semiconductors containing 1,4,5,8-
naphthalenetetracarboxylic diimide central fragment
Lauryna Monika Svirskaitė, Ernestas Kasparavičius, Tadas Malinauskas
Faculty of Chemical Technology, Kaunas University of Technology, Radvilėnų pl. 19, Kaunas
Email: [email protected]
Nowadays energy consumption is growing at a substantial rate. The conversion of
sunlight into electricity is one of the most promising studies to meet the increasing energy
demands for future generations without the negative impact on the global climate. One of the
most attractive alternatives are photovoltaic systems, which uses sunlight as free and endless
energy source [1].
The organic electron transporting materials (ETM) are very important components in
perovskite solar cells (PSCs) and play a significant role in extracting and transporting
photogenerated electrons while simultaneously serving as a hole blocking layer [2]. Fullerenes
and their derivatives are considered as one of the best n-type organic semiconductors and are
often used in PSCs. Unfortunately, these compounds show some disadvantages (e. g. they
are expensive), which limit their application [3].
The aim of this work – to synthesize new electron transporting materials with 1,4,5,8-
naphthalenetetracarboxylic diimide central fragment containing pentafluorophenyl and
pyridine groups. Pentafluorophenyl fragment was used as a protecting group to increase
perovskite moisture resistance, while pyridine moiety reduces surface defects of the
perovskite layer.
From the obtained results it was confirmed that functional pentafluorophenyl group
improved the stability of perovskite. There are some preliminary results of these electron
transporting materials and further investigation is being done.
REFERENCES
[1] Juan-Pablo Correa-Baena, Michael Saliba, Tonio Buonassisi, Michael Grätzel, Antonio Abate, Wolfgang
Tress, Anders Hagfeldt. Promises and challenges of perovskite solar cells. Science 2017, 358, 6364, pp.739-
744
[2] Guang Yang, Hong Tao, Pingli Qin, Weijun Ke and Guojia Fang. Recent progress in electron transport layers
for efficient perovskite solar cells. J. Mater. Chem. A 2016, 4, pp.3970-3990.
[3] Rui Wang, Muhammad Mujahid, Yu Duan, Zhao‐Kui Wang, Jingjing Xue, Yang Yang. A Review of Perovskites
Solar Cell Stability. Advanced Functional Materials 2019, 1808843.
1 2
DMF, 120 °C DMF, 140 °C
Fig. 1. Synthesis of the compound 2
53
P15
AlGaN/GaN/SiC high-electron-mobility transistors and
Schottky diodes
Vytautas Jakštas, Justina Malakauskaitė, Justinas Jorudas, Vytautas Janonis,
Linas Minkevičius and Irmantas Kašalynas
Department of Optoelectronics, Center for Physical Sciences and Technology, Saulėtekio av. 3,
LT-10257 Vilnius, Lithuania
Email: [email protected]
For many years, IIIA-nitrides have been researched and used to manufacture electronic
components due to the unique properties of these materials [1]. GaN-based components
containing two-dimensional electron gas (2DEG) are also applicable for the development of
plasmonic emitters and sensors in terahertz (THz) frequency [2, 3]. The top quality electronic
components are obtained by growing nitride layers on a native substrate [4], however bulk
GaN substrates are still expensive and small in size. As a result, lower-quality components
are usually grown on Si or Al2O3 substrates, while SiC is irreplaceable at high quality
requirements.
Here we present a research on Schottky diodes (SDs) and high-electron-mobility
transistors (HEMTs) made of heterostructures with different substrates. Heterostructures were
grown at the Institute of High Pressure Physics (UNIPRESS), Poland, on a sapphire or semi-
insulating 6H-SiC substrate by the metalorganic chemical vapor deposition (MOCVD) method.
2DEG density and electron mobility of the latter heterostructure were 8.3×1012 cm-2 and 1900
cm2/(Vs) at room temperature and 6.9×1012 cm-2 and 17000 cm2/(Vs) at 77 K, respectively.
The ohmic (Ti/Al/Ni/Au) and Schottky (Ni/Au) contacts were manufactured at the Center
for Physical Sciences and Technology (FTMC) using UV photolithography, electron beam
evaporation and rapid thermal annealing technology [3]. The ohmic contacts were optimized
by selecting different metal thicknesses and annealing temperatures.
SDs and HEMTs made of AlGaN/GaN/SiC heterostructure demonstrated better electrical
performance than that of analogous components made of sapphire-based heterostructures.
For both SD and HEMT, lower leakage currents and higher current-switching ratios ION/IOFF
were observed. In addition, higher values of direct HEMT current were measured, resulting in
a higher transconductance. Better electrical properties of the SiC-based components are due
to a higher quality of epitaxial layers obtained by growing the nitrides on a SiC substrate.
A possibility to use such a HEMT without a special THz antenna as a sensor for imaging
a commercially 0.3 THz source beam was demonstrated at room temperature. The
parameters of the sensor could be improved by designing an appropriate THz antenna and by
optimizing the dimensions of the sensor.
REFERNCES
[1] R. Quay, Gallium Nitride Electronics (Springer Berlin Heidelberg, Berlin, Heidelberg, 2008).
[2] V. Jakštas et al, Appl. Phys. Lett. 110(20), 202101 (2017).
[3] V. Jakštas et al, Lith. J. Phys. 58(2), 188–193 (2018).
[4] A. B. Piotrowska et al, ECS Trans. 75(12), 77–84 (2016).
54
P16
Comparison of AlGaN/GaN HEMT and silicon nMOS
terahertz detectors with the same length of the gate.
Juozas Vyšniauskas and Alvydas Lisauskas
Institute of Applied Electrodynamics and Telecommunications, Vilnius University, Saulėtekio av.
3, LT-10257 Vilnius, Lithuania.
Email: [email protected].
A comparison of AlGaN/GaN HEMT and
silicon nMOS terahertz detectors was made
using two-dimensional Hydrodynamic (HD)
and Drift-Diffusion (DD) models implemented
in the Synopsys TCAD Sentaurus program
package. The HEMT structure described in [1]
with the exception of the Gate (LG) and the
Ungated (LUG) regions length. We used LG =
LUG = 100 nm and AlGaN thickness equal to 15
nm. The structure of nMOS coincides with the
standard 130 nm CMOS technology with LG =
100 nm and SiO2 thickness of 2.5 nm. HD and
DD models were compared as well. A simpler
DD model requires less computer time and can
be used for the calculation of current
responsivity and Noise Equivalent Power
(NEP) at the frequencies lower than 0.2–0.3
THz. At higher frequencies, such as 1.0 THz
(Fig. 1 and Fig. 2), the energy balance
equation must be included in the model (HD).
The maximum current responsivity is
about 3.5 times higher in HEMT than in nMOS,
despite the existence of two passive ungated
regions in HEMT. The electron mobility in the
2D channel in undoped HEMT is much higher
than in highly doped (2.5·1018 cm-3) nMOS.
The minimum NEP is about 3 times lower in
HEMT than in nMOS. Thus, HEMT is more
appropriate for the detection of weak terahertz
signals.
REFERENCES
[1] J.Vyšniauskas, A.Lisauskas, M.Bauer, D.Čibiraitė, J.Matukas and H.G.Roskos; IOP Conf. Series: Journal of
Physics: Conf. Series 906 (2017) 012023 pp.1-4.
Fig. 1 The dependence of current responsivity on
gate voltage UG of HEMT and nMOS terahertz
detectors with gate length LG = 100 nm at 1.0 THz.
Fig. 2 The dependence of Noise Equivalent Power
on gate voltage UG of HEMT and nMOS terahertz
detectors with gate length LG = 100 nm at 1.0 THz.
55
P17
In vitro studies for the assessment of bio-nano
interactions
Karolina Zajdel1, Bożena Sikora2, Przemysław Kowalik2, Izabela Kamińska2,
Małgorzata Frontczak-Baniewicz1
1Mossakowski Medical Research Centre, Polish Academy of Sciences, Warsaw, Poland 2Institute of Physics, Polish Academy of Sciences, Warsaw, Poland
Email: [email protected]
Over the past two decades, the rapid application
development of nanotechnology reports a massive amounts
of information about dangers and benefits of using new
nanomaterials. In adaptive nanomaterials science, especially
for nanomaterials used in nanomedicine still have been
observed some limitations. In order to ensure biosafety of
newly developed nanoparticles, their unique features and
advanced properties cannot be overtaken by their intrinsic
toxicity [1].
Up-converting nanoparticles (UCNPs) are an emerging
class of inorganic optical nanoprobes doped with lanthanide
ions. This type of nanoparticles under 980 nm infrared
excitation have ability to up-convert long wavelength
excitation radiation to short wavelength emission. The
UCNPs are also widely characterized by low toxicity, low
photobleaching, no visible autofluorescence in biological
samples, deep tissue penetration, large anti-Stokes shifts and excellent photostability. These
unique features make the nanoparticles have great potential in biomedical application such as
bio-detection, drug delivery, cancer therapy or as powerful and non-invasive tool for bio-
imaging [2].
The biological and functional interaction of nanoparticles with living cells are often poorly
understood. The deep lack of this knowledge is caused mainly by focusing on design new
nanoparticles and develop their new potential application in bio-medical field [3].
For this purpose, the all particle-cell interactions including bioavailability, cellular uptake
mechanisms, in vitro fate, colocalisation and cytotoxicity of β-NaYF4:Yb3+,Er3+ up-converting
nanoparticles with an average diameter of 20 nm have been investigated. Understanding the
interaction of nanoparticles with the cellular membrane is essential in nano-toxicology area.
However, internalization of nanoparticles still remains an open question. In our in vitro studies
we have analysed short and long term incubation of nanoparticles in human cells by
transmission electron microscopy (TEM). The TEM images are provided for observation of a
nanoscale materials much more detailed in particular at the subcellular level than conventional
light microscopes.
We have observed a rapid nanopraticles’ internalisation by active transport and
intracellular vesicles containing nanoparticles suggest that UCNPs uptake is correlated with
Fig. 1 TEM image of 1µg/ml
β-NaYF4:Yb3+,Er3+ UCNPs inside
HeLa cells after 2 hours.
Fig. 1 Short and clear caption,
revealing the message of the
figure.
56
endocytic pathways. The UCNPs colocalize with the selected cell organelles as early
endosomes, late endosomes and lysosomes. The HeLa cells have not shown any cytotoxicity
and morphological or ultrastructural changes after treatment with wide range of different
UCNPs concentrations. The nanoparticles were never observed in nucleus and mitochondria
or free in cytoplasm. In order to verify participation endocytosis in the internalization of
nanoparticles into the cells, a number of experiments were carried out when endocytosis is
inhibited by various inhibitors. Cells viability studies were also evaluated by a standard
colorimetric assays which showed no relevant cytotoxicity.
In vitro studies for the assessment of bio-nano interactions to monitor cells support
current and improve future therapeutic strategies with special attention to the use this type of
nanoparticles. Their particular potential manifests in modern trend of theranostic which
combine both diagnostic and therapeutic capabilities at the same moment.
REFERNCES
[1] H. Su, Y. Wang, Y. Gu, L. Bowman, J. Zhao, & M. Ding, Journal of Applied Toxicology, 38 (2018) pp. 3-24.
[2] M. K. Mahata, and K. T. Lee; Nanoscale Adv., 1 (2019) pp. 2372- 2381
[3] E. Wysokińska, J. Cichos, A. Kowalczyk, M. Karbowiak, L. Strządała, A. Bednarkiewicz and W.
Kałas; Biomolecules 9 (2019), pp. 14.
57
P18
AIII-BV Quantum Structures for NIR Emitters
Algirdas Jasinskas, Simona Pūkienė, Sandra Stanionytė, Martynas Skapas,
Bronislovas Čechavičius, and Renata Butkutė
Center for Physical Sciences and Technology, Saulėtekio ave. 3, LT-10257, Vilnius, Lithuania
With the rapid development in modern sensing technologies, there is an increasing need
for efficient near infrared (NIR) sources. Group AIII-BV semiconductor platform, namely GaAs,
AlGaAs, GaAsBi, etc. is widely used in this wavelength region for various optoelectronics
applications, such as solar cells, photodetectors, as well as lasers [1]. The ability to alloy
different AIII-BV elements allows tuning various mechanical, electrical and optical properties
and provides a great control of bandgap, therefore emission wavelength. Moreover, the use
of quantum structures, such us quantum wells and quantum dots, results in improved device
performance or even new devices (e.g.
quantum cascade lasers) [2]. For these
reasons, well-known AIII-BV
compounds are widely studied with
continuing alloying and engineering of
new ternary, quaternary even quinary
systems exhibiting the synergy of
properties.
The samples for this research
were grown by AIII-BV Molecular Beam
Epitaxy (MBE) and Migration-Enhanced
Epitaxy (MEE). Complex
characterization study including
Transmission Electron Microscopy
(TEM), High Resolution X-Ray
Diffraction (HR-XRD), Atomic Force
Microscopy (AFM), and
Photoluminescence measurements
(PL), was used to determine the
influence of growth conditions and
design parameters on structural and
optical properties of the quantum structures. Fig. 1 and Fig. 2 present the cross-sections of
AIII-BV quantum wells and quantum dots containing samples, respectively, investigated in this
work.
Acknowledgement: This work was supported by Research Council of Lithuania (09.3.3.-LMT-
K-712-15-0281)
REFERENCES
[1] S. Mokkapati and C. Jagadish, Materials today 12 (2009) pp. 22-32
[2] S. Kasap and P. Capper, Springer Handbook of Electronic and Photonic Materials, 2nd ed., Springer (2017)
pp.1037-1057.
Fig. 1. STEM image of a sample with 5 7 nm GaAsBi quantum wells (bright areas) within GaAs barriers.
Fig. 2. STEM image of a sample with bismuth quantum dots (bright dots) within AlAs barrier layers.
58
P19 Photoelectrochemical generation of active chlorine
species at sol-gel derived nanostructured WO3 electrode
Maliha Parvin, Milda Petrulevičienė, Irena Savickaja, Benjaminas Šebeka, Arnas Naujokaitis, Vidas Pakštas and Jurga Juodkazytė
Center for Physical Sciences and Technology, Saulėtekio av. 3, Vilnius 10257, Lithuania [email protected]
Due to strong oxidative power of
hypochlorous acid (HClO), it is worldwide
used for the disinfection of water [1, 2].
Solar-driven generation of HClO in
chloride solutions (e.g. seawater) can offer
a sustainable way to produce this
chemical, which is currently produced by
highly energy-intensive chlor-alkali
process.
In this study the suitability of tungsten
(VI) oxide anode for the
photoelectrochemical formation of active
chlorine species (Cl2, HClO, ClO-) was
investigated.
Nanostructured layers of WO3 on
fluorine doped tin oxide (FTO) substrate
were formed by sol gel method.
Peroxytungsten acid (PTA) was
synthesized using sodium tungstate (Na2WO4 x 2H2O), HCl (37%) and H2O2 as precursors and
(NH4)2C2O4 as capping agent. Subsequently, propanol was added as a reductant, which slowly
and controllably reduced peroxotungstates to form uniform and ordered WO3.H2O films on FTO
covered glass substrates under soft water bath conditions at 85oC. After coating procedure
samples were annealed at 500°C for 2 h with heating rate of 1°C/min to obtain a crystalline
nanostructured WO3 films and to remove residual carbon [3]. The coatings were characterized
using X ray diffraction (XRD) analysis and scanning electron microscopy (SEM).
Photoelectrochemical experiments in chloride containing solutions revealed the activity of
WO3 films in active chlorine species formation. Increasing photocurrent was observed in the
potential, E, range above 0.2 V (vs. Ag/AgCl) (Fig. 1). When photoanode was polarized at E = 1.4
V for different periods of time, increasing cathodic current was recorded during subsequent
negative going scan at E < 0.3 V. This current should be attributed to reduction of ClO . The
stability of the photoelectrodes along with applicability of nanostructured WO3 films for water
disinfection was studied.
REFERENCES
[1] S. Iguchi, Y. Miseki, and K. Sayama;Sustainable Energy & Fuels photoelectrochemical solar energy
conversion 2 (2018) pp. 155–162.
[2] J. Jeong, C. Kim, and J. Yoon; Water Res., vol. 43, no. 4, (2009) pp. 895–901.
[3] Q. Zeng, J. Li, J. Bai, X. Li, L. Xia, and B. Zhou; Appl. Catal. B Environ., vol. 202,(2017) pp. 388–396.
-0.4 0.0 0.4 0.8 1.2 1.6
-0.10
-0.05
0.00
0.05
Cu
rre
nt,
mA
Potential, V (Ag/AgCl)
in dark
in light, 0 min
in light, 1 min
in light, 2 min
in light, 10 min
Estop
Fig. 1 Cyclic voltammograms of sol-gel prepared WO3
photoelectrode in 0.5 M NaCl solution: potential scan was
stopped at 1.4 V for periods of time specified in the inset;
potential scan rate 50 mV s-1
59
P20
Magnetoplasma Excitation in Double CdTe/CdMgTe Quantum Wells
D. Yavorskiy1,4, M. Szoła1, K. Karpierz1, I. Własny1, D. Śnieżek2, P.
Nowicki2, J. Wróbel2, S. Chusnutdinow2, G. Karczewski2, T. Wojtowicz3,
and J. Łusakowski1 1Faculty of Physics, University of Warsaw, ul. L. Pasteura 5, 02-093 Warsaw, Poland
2Institute of Physics, PAS, al. Lotnik w 32/46, 02-668 Warsaw, Poland 3International Research Centre MagTop, Institute of Physics, PAS, al. Lotnik w 32/46, 02-668
Warsaw, Poland 4 Center for Terahertz Research and Applications, Institute of High Pressure Physics PAS, 01-
142, Warsaw, Poland
Cadmium telluride heterostructures with a two-dimensional electron gas (2DEG) have been
studied in magnetotransmission. The main reason that motivated this research was an interest
in basic studies of low-energy excitations of a 2DEG. In general this direction of research is
related to the cyclotron resonance and magnetoplasma excitations observed at low
temperatures and high magnetic elds. Up to this moment, most of such research has been
concentrated on GaAs/AlGaAs systems and much less data exists for CdTebased devices.
Recently, we have presented results of THz magnetospectroscopy studies on single modulation
doped CdTe/CdMgTe quantum wells [1].
In this work we concentrate on modulation doped double CdTe/CdMgTe quantum wells. The
idea of the present research was to compare THz excitations in three types of samples: A - as
grown, B - with a gold grid and C - with the surface etched in such a way that a grid was formed
with trenches cutting one quantum well only. The period of grids for samples B and C and their
aspect ratio was equal to 8 µm and 50%, respectively. Magnetotransmission of THz radiation
through the samples was measured at 2 K. The source of THz radiation was a molecular laser.
To register a transmitted signal we have used a carbon bolometer.
In both samples A and B we have observed a cyclotron resonance only with an e ective mass
equal to 0.101m0 and no evidence of magnetoplasma excitation was found in sample B.
However, in sample C we have observed only magnetoplasmon excitations with a high
amplitude, comparable to the cyclotron resonance in sample A.
To summarise, we propose that samples with double quantum wells with etched grid are good
adapted for observation of magnetoplasmon excitations.
This research was supported in part by the National Science Centre (Poland) through grants
UMO-2014/13/B/ST3/04393, UMO-2017/27/N/ST7/01771 and UMO-2015/17/B/ ST7/03630, by
the Foundation for Polish Science through the IRA Programme co- nanced by EU within SG
OP, and by the Foundation for Polish Science Grant Nos. TEAM/20163/25
[1] I. Grigelionis et al., Phys. Rev. B 91, 075424 (2015).
60
P21
Changes of Boron Nitride Luminescence as a Result of X-Ray Irradiation
M. Szoła1,2, M. Tokarczyk1, G. Kowalski1, J. Binder1, K. Pakuła1,
A. Dąbrowska1, A. Wysmołek1, and J. Łusakowski1
1Faculty of Physics, University of Warsaw, ul. L. Pasteura 5, 02-093 Warsaw, Poland 2Center for Terahertz Research and Applications, Institute of High Pressure Physics PAS, 01-
142, Warsaw, Poland
There were different motives for the studies presented in this paper. Firstly, the broadband
photoluminescence (PL) of BN can be tentatively attributed to defects and it is interesting to
verify whether X-rays can influence the PL; and if they do, what is the nature of such defects -
are the changes temporary or permanent. Secondly, it was found that after the irradiation of BN
layers with electrons changes in Raman or PL spectra can be observed. Our aim was to
corroborate whether comparable changes can be produced with X-rays. Thirdly, we wanted to
determine whether boron nitride could be potentially used as a dosimetric material. Once
devices based on boron nitride will be used in the future, dosimetric properties of this material
could be addressed to estimate doses of ionizing radiation absorbed by people in nuclear or
radiation accidents.
Measurements were performed at room temperature on a few samples of BN in various forms -
powder, exfoliated and epitaxial layer. In order to observe influence of X radiation on the
photoluminescence, we irradiated samples with a collimated beam of X-rays that was generated
by a CuKα X-ray tube, for a few different periods of time tR. After each irradiation time, the X-ray
beam was turned off and a laser beam exciting the PL (wavelength of 488 nm, power of about
100 mW) was simultaneously set on. A luminescence integration time was set to 1 min for every
spectrum, to determine a time evolution of the luminescence with a step of 1 min.
No structural changes of BN were found after irradiation with X-rays. We observed that X-rays
influenced intensity of the PL in the whole registered spectral range between 550 nm and 900
nm.
To conclude, it was shown that the PL of boron nitride is sensitive to X-ray irradiation produced
with a standard X-ray tube that is generating photons with the energy of 8 keV. Which also
shows possible potential of used material in dosimetrical applications.
61
P22
Interaction between magnetohydrodynamic and
temperature instabilities during S-N switching of thin II-
type superconductor films.
Linas Ardaravičius, Oleg Kiprijanovič
Center for Physical Sciences and Technology, Saulėtekio al.3, LT-10257, Vilnius, Lithuania.
Email: [email protected].
Recently attention was drawn to complex calculations between the interaction of
mechanic and hydrodynamic instabilities [1]. There is no doubt that soon there will appear
calculations of the interaction between temperature and magnetohydrodynamic or plasma
instabilities. However, the creation of mathematical models in these complex cases requires
a clear understanding of the occurring physical processes. Here it will be described interaction
between magneto-hydrodynamic and temperature instabilities induced by ns overcritical
current pulses during switching between superconducting (S) and normal (N) states of the thin
films.
Earlier It was described the S-N switching of the high quality films with hallmark as the
cumulative effect [2]. The cumulative effect appears due to bending of the S-N border. The
border width is characterized by Pearl length eff of about 1 m wide. Its specific longitudinal
properties are more obvious the
better are the superconducting
properties of the films, i.e. both
current I and expelled magnetic
field B are better concentrated at
the film edge.
In mechanics, it is known
Euler instability, half wave bending
of a rod under applying force, and
Ishlinsky-Lavrent’ev instability,
bending of the rod by vibration
modes of different frequencies
under the pulsed applying force. In our magnetohydrodynamic case the S-N border near film
edge is bent under the current pulse as the superposition of half wave with one of the modes
(see Fig.1). Current concentration at the marked points (a,b,c) induces temperature instability
followed by local S-N switching and inside penetration of the N state.
Scanning electron microscope images of damaged samples show that the interaction
depending on the film quality and the current amplitude suggests different scenarios for the
movement of N zone. It can be the soft one, without damage of the film and up to the explosive
one, when strong cumulative effect breaks the S-N border, and a melting of the film occurs.
REFERENCES
[1] M. A. Ilgamov, Doclady Physics 60 (2015) pp. 296-298.
[2] O. Kiprijanovič, S. Ašmontas, Theses of LNP conference (2015) p. 315.
Fig.1 Interaction of unstable S-N border of width eff with areas of temperature growth (a,b,c). View from above.
62
P23
Design and fabrication of THz torch device containing
Ga(As,Bi)/AlGaAs parabolic quantum well in active region
for THz emission
Mindaugas Karaliūnas1, Justas Pagalys1, Vytautas Jakštas1, Jan Devenson1,
Simona Pūkienė1, Renata Butkutė1, Andres Udal2, and Gintaras Valušis1
1Optoelectronics department, Center for Physical Sciences and Technology,
Sauletekio Av. 3, 10257 Vilnius, Lithuania 2Department of Software Science, Tallinn University of Technology,
Ehitajate tee 5, 19086 Tallinn, Estonia
Email: [email protected]
Terahertz (THz) waves are unique for its properties to
penetrate through most of opaque dielectric materials and
read out chemical composition of covered substances without
affecting the content [1]. For many applications, such as
security, defense, telecommunication, non-destructive quality
inspection, etc., fast, reliable, compact and easy-to-operate
THz spectroscopy and imaging systems are required. While
there are some achievements in compact highly-sensitive
detectors [2] and compact functional optic elements [3] the
efficient room-temperature emitters remains main obstacle for
introduction of cost-effective, robust and application-ready
system. The aim of this work is to demonstrate the newly
designed incoherent THz source – THz torch – with parabolic
quantum well (PQW) in the active region which serves as an
artificial transition pathway for carriers that meet THz
frequency to enhance the radiation at the spectral range of
interest.
The new device concept is proposed to increase the power of THz radiation by
depopulating the lowest subband of PQW with LO phonon scattering as it is shown in Fig. 1.
The analog graded Ga(As,Bi)/AlGaAs PQW samples were grown using molecular beam
epitaxy technique [4]. The two terminal pin diode THz torch device is designed and fabricated.
ACKNOWLEDGMENT
This research has received funding from European Social Fund (project No 09.3.3-LMT-K-
712-02-0172) under grant agreement with the Research Council of Lithuania (LMTLT).
REFERENCES
[1] M. Karaliūnas, K. E. Nasser, A. Urbanowicz, I. Kašalynas, D. Bražinskienė, S. Asadauskas and G. Valušis;
Scientific Reports 8 18025 (2018). [2] V. Jakštas, J. Jorudas, V. Janonis, L. Minkevičius, I. Kašalynas, P. Prystawko and M. Leszczynski; Lithuanian
Journal of Physics 58(2), (2018) pp 188-193. [3] D. Jokubauskis, L. Minkevičius, M. Karaliūnas, S. Indrašiūnas, I. Kašalynas, G. Račiukaitis and G. Valušis;
Optics Letters 43(12), 2795 (2018). [4] S. Pūkienė, M. Karaliūnas, A. Jasinskas, E. Dudutienė, B. Čechavičius, J. Devenson, R. Butkutė, A. Udal and
G. Valušis; Nanotechnology 30 455001 (2019).
Fig. 1. Arrangement of PQW
subbands in active region of THz
torch device with LO phonon
scattering depopulation.
63
P24
Thick objects imaging using compact phase shifting
elements designed for 0.6 THz
L. Minkevičius, D. Jokubauskis, V. L. Paukštė, S. Indrišiūnas, I. Kašalynas, S.
Orlovas, A. Urbas, and G. Valušis
1Center for Physical Sciences and Technology, Saulėtekio Ave. 3, LT-10257 Vilnius, Lithuania,
Email: [email protected]
Reducing the dimensions of terahertz (THz) imaging
systems is a key-factor for increasing applicability in mobile
unattended package inspection systems used at airports or
public places [1]. From practical view of point, it is of particular
importance to design THz imaging system so that it would be
compact, reliable and provides the ability to scan thick
objects, mostly independent by the distance to the focusing
element.
In this work, we demonstrate design, operation and
high-resolution imaging of silicon-based Fibonacci [2] and
Bessel zone plates [3] for 0.6 THz frequency. These focusing
elements can improve THz imaging system by simultaneous
two plane imaging or by long focal depth for thick object
inspection. Focusing elements were fabricated on silicon
wafer of 0.5 mm thickness with resistance 0.01–1 MΩcm and
refractive index of 3.46 using laser direct writing technology
[4], which was also employed to produce multilevel phase Fresnel lens described in [5]. The
focusing performance was investigated theoretically and experimentally by measuring spatial
profiles, distance between the foci and focal depth at sub-THz range. The ability to perform
simultaneous imaging with the wavelength resolution of two planes separated by 7 mm
distance was experimentally revealed. The multifocal imaging results were compared with the
performance of the multilevel phase Fresnel lens [5]. A novel approach of THz imaging using
Bessel zone plate providing a 2×λ resolution at =0.5 mm and weak result dependence on
object position will be demonstrated as well.
Acknowledgment
European Regional Development Fund (01.2.2-LMT-K-718-01-0047), Research Council of Lithuania (DOTSUT-
247)
REFERNCES
[1] R. Li, C. Li, H. Li, S. Wu, and G. Fang;IEEE Trans. Terahertz Sci. Technol., 9(2) (2019) pp. 165–176. [2] D. Jokubauskis, L. Minkevičius, M. Karaliūnas, S. Indrišiūnas, I. Kašalynas, G. Račiukaitis, and G. Valušis;
Opt. Lett., 43(12) (2018) pp. 2795–2798. [3] L. Minkevičius, D. Jokubauskis, I. Kašalynas, S. Orlovas, A. Urbas, and G. Valušis in International Conference
on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz, (2019) pp. 2. [4] B. Voisiat, S. Indrišiūnas, R. Šniaukas, L. Minkevičius, I. Kašalynas, and G. Račiukaitis, Proc. SPIE 10091(10)
(2017) pp. 100910F. [5] L. Minkevičius, S. Indrišiūnas, R. Šniaukas, B. Voisiat, V. Janonis, V. Tamošiūnas, I. Kašalynas, G.
Račiukaitis, and G. Valušis, Opt. Lett. 42(10) (2017) pp. 1875–1878.
Fig. 1 The photo of thin silicon-
based phase shifting element for
the 0.6 THz
64
P25
Effect of Molecular Beam Epitaxy Growth Conditions for
Terahertz Sensing InGaAs Diodes
Domas Jokubauskis, Renata Butkutė, Linas Minkevičius Department of Optoelectronics, Center for Physical Sciences and Technology, Saulėtekio av. 3,
LT-10257 Vilnius, Lithuania
Email: [email protected]
InGaAs-based bow-tie diodes for terahertz
(THz) range are found to be well-suited for
development of compact THz imaging systems
[1]. To further optimize design for sensitive and
broadband THz detection, one of the major
challenges remains to understand influence of
growth conditions and role of defects for device
operation. We present detailed study of
photoreflectance and THz sensitivity of InGaAs
bow-tie diodes.
Figure 1 depicts the sensitivity as a function
of current for all types of the studied samples
at frequencies of 0.3 THz and 0.6 THz. As it is
seen, sensitivity of InGaAs bow-tie diodes
fabricated from the wafers B203 and B204
increases while raising the current and reaches
17.5 V/W and 10 V/W at 0.3 THz and 12.5 V/W
and 7 V/W at 0.6 THz, respectively, at the bias current of 0.2 mA.
To conclude, the THz detectors layers grown with beam equivalent pressure In/Ga ratio equal
to 2.06 are found to be well suited for fabrication of room temperature bow-tie THz detectors
enabling sensitivity of 13 V/W at 0.6 THz due to strong built-in electric field effects [2].
REFERENCES
[1] G. Valušis et al., “Compact solutions for spectroscopic solid-state-based terahertz imaging systems,” in
Terahertz Emitters, Receivers, and Applications VIII, 2017, p. 27.
[2] V. Palenskis et al., “InGaAs Diodes for Terahertz Sensing—Effect of Molecular Beam Epitaxy Growth
Conditions,” Sensors, vol. 18, no. 11, p. 3760, Nov. 2018.
-200 0 200
0
5
10
15
20
-300 -200 -100 0 100 200 300
0
2.5
5.0
7.5
10.0
Us
at
0.3
TH
z,
V/
W
I, A
B197
B203
B204
fmod
= kHz
Us a
t 0
.6 T
Hz,
V/
W
Fig. 1 Voltage sensitivity of the InGaAs diode detector
with different In/Ga ratios at 0.3 THz and 0.6 THz
frequency with modulation frequency of 1 kHz (adapted
from [2]).
65
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