Investigation of metal-ferroelectric interfaces at micro and nanometric level
(Investigarea interfeţelor metal- feroelectric la nivel micro şi nanometric)
IFA-CEA cooperation programPresenting: Dr. Lucian Pintilie
Project responsible from the Romanian part
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IFA-CEA symposium 20 of October 2011, Magurele
The main objective of the project will be to study the construction of the metal-ferroelectric interface and the dynamic of charge compensation in relation to polarization switching. The results will be compared to the results of the macroscopic electric measurements performed on standard metal-ferroelectric-metal (MFM) capacitors. Also, the metal-ferroelectric interface will be compared with the results reported for the free surface.
Scope of the project
Important milestones
End of the 1st year-deposition and characterization of epitaxial PZT films; conclusions regarding the charge compensation on the free surface
End of the 2nd year-formation of metal-PZT interface and characterization through surface/interace investigation techniques; charge compensation at the interface
End of the 3rd year-macroscopic-microscopic correlation
2
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Teams and collaboration
There is a common interest in the proposed topic. The responsible of the Romanian part has collaborated with Dr. Gweneal Le Rhun, member of the CEA team, during their workstages at MPI Halle, Germany. Dr. Pintilie was visiting scientists while dr. Le Rhun was a Humboldt fellow. A few common papers resulted from this collaboration (see the list below). The present project will help to develop the collaboration between the two teams to a new level.
RO team CEA team
Project leader(Name)
Dr. Pintilie Lucian Dr. LE RHUN Gwenaël
LaboratoryInstitutionAddressTel :Fax :e-mail:Head of laboratory
Laboratory Multifunctional Materials and StructuresNational Institute of Materials PhysicsAtomistilor 105bis, Magurele 077125, Romania+40-(0)21-3690185+40-(0)[email protected]. Ionut EnculescuGrown of SRO layer on STO/Si substrates; grown of PZT/SRO on single crystal STO substrates; surface/interface investigation; electrical measurements with temperature; comparison with samples from France
RF Components Laboratory CEA17 rue des Martyrs, 38054 Grenoble Cedex 9, FRANCE+33-(0)4-38784042+40-(0)[email protected] MarcGrown of STO on Si substrate, and of PZT on SRO/STO/Si; preliminary electrical characterization
RO team CEA teamDr. Lucian PintilieDr. Stancu Viorica (young researcher)Dr. Ioana PintilieDr. Cristian Mihail TeodorescuDrd. Cristina Dragoi (young researcher)Drd. Marius Husanu (young researcher)Drd. Lucian Trupina
Dr. Gwenaël Le Rhun (young researcher)Dr. Emmanuel Defaÿ Shi YIN (young researcher)
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Results: Romanian team
AFM pictures of STO substrate (left), SRO film (middle) and PZT film (right)
HR-TEM picture of the PZT-SRO-STO interfaces
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The stability of the polarization on the bare surface
-3 -2 -1 0 1 2 3
-40
-20
0
20
40
d33
(pm
/V)
Vdc
Local piezoelectric hysteresis
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Nivel ASF Pozitie niveluri energetice (eV) in diferiti compusiPb Ti Zr PbO PbO2 TiO2 ZrO2 PbTiO3 PbZrO3 Au
O 1s 0.66 - - - 529.3 529.0 530.0 529.9 529.9 ? -Ti 2p 1.8 - 454 - - - 459.0 - 458.6 - -Zr 3d 2.1 178.9 - - - 183.3 - ? -Pb 4f 6.7 136.9 - - 137.6 137.4 - - 139.0 138.5 -Au 4f 4.95 - - - - - - - - - 83.8
Ipoteza 1: tot OIpoteza 2: fara O
(c4)Ipoteza 3:
fara O (c3 + c4)Componente
comp. at. %
total at. %
comp. at. %
total at. %
comp. at. %
total at. %
O 1s (1) 1.01 66.65 1.18 60.97 1.42 53.11O 1s (2) 36.73 43.02 51.68
O 1s (3) 14.32 16.77fara
[20.15]
O 1s (4) 14.59fara
[17.09]fara
[20.53]Ti 2p (1) 1.88 10.87 2.21 12.73 2.66 15.29Ti 2p (2) 4.04 4.73 5.69Ti 2p (3) 4.9 5.78 6.95Zr 3d (1) 0.66 3.56 0.77 4.17 0.92 5.02Zr 3d (2) 2.63 3.08 3.71Zr 3d (3) 0.274 0.32 0.38Pb 4f (1) 16.22 18.89 18.99 22.12 22.82 26.58Pb 4f (2) 2.18 2.55 3.07Pb 4f (3) 0.48 0.56 0.68Suma 99.914 117.05 140.66
Pb 1.31Ti 0.75Zr 0.25O 4.62
Pb 1.31Ti 0.75Zr 0.25O 3.61
Pb 1.31Ti 0.75Zr 0.25O 2.61
Results of XPS analysis:-surface is depleted in oxygen-some PbCO3 and PbO forms at the surface
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Changes observed after treatment in oxygen plasma
Behavior of short-circuit current for different electrodes
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PFM studies on PZT52/48 films deposited in France, above the SRO film deposited in Romania by PLD
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Results: French team
Figure 1: RHEED images at the end of STO deposition
Figure 2: 2θ/ω scan on PZT deposited on STO/Si
Hysteresis and C-V curves for PZT52/48 films deposited by sol-gel in France, above the SRO layer deposited by PLD
in Romania
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Benefits of the collaboration
Romanian team:- Has learned that STO can be epitaxially grown on Si- Has the opportunity to compare the results obtained on epitaxial PZT films grown by sol-gel with those of the films grown by PLD
French team:-Can grow the PZT films on SRO layers, thus can develop metal-ferroelectric-metal structures- Has the opportunity to compare the results obtained on epitaxial PZT films grown by sol-gel with those of the films grown by PLD
Observation:Due to some organizational problems on the French side, which generated delays in getting the financial support, it was not possible to exchange visits in the first year of the project.
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Perspectives for the next years
Foreseen common activities:- Finalizing the comparison of surface properties and PFM results on sol-gel and PLD deposited PZT52/48 films both on SRO/STO/Si and SRO/STO(sc) substrates
-Testing common metals used in microelectronics (Cu, Au, Al) as electrodes and compare the results on sol-gel and PLD deposited films
- Studying the electrode-PZT interface by various methods, with emphasis on PFM and PLD
Publications:L. Pintilie, C. Dragoi, and I. Pintilie, “Interface controlled photovoltaic effect in epitaxial Pb(Zr,Ti)O3 films with tetragonal structure”, JOURNAL OF APPLIED PHYSICS 110, 044105 (2011)L. Pintilie, C. Dragoi, V. Stancu, G. Ibanescu, I. Pintilie, “Effect of microstructure and electrode interface on the hysteretic behavior of ferroelectric Pb(Zr,Ti)O3 thin films”, sent to JOURNAL OF PHYSICSD: APPLIED PHYSICSN.G. Gheorghe, G.A. Lungu, C.M. Teodorescu, I. Pintilie, L. Trupina, C. Dragoi, “Photoelectron spectroscopy studies of pulsed laser deposited Pb(Zr,Ti)O3-δ single crystal films”, sent to PHYSICA STATUS SOLIDI-RAPID RESEARCH LETTERS