Optical and Electrical Properties of Spray Pyrolysis Deposited Nano-crystalline BFO Films

8/3/2019 Optical and Electrical Properties of Spray Pyrolysis Deposited Nano-crystalline BFO Films

1/12

Optical and electrical properties of spray pyrolysis deposited nano-crystalline BiFeO3 filmsAnnapu Reddy Venkateswarlu, G. D. Varma, and R. Nath

Citation: AIP Advances 1, 042140 (2011); doi: 10.1063/1.3662093

View online: http://dx.doi.org/10.1063/1.3662093

View Table of Contents: http://aipadvances.aip.org/resource/1/AAIDBI/v1/i4

Published by the American Institute of Physics.

Related Articles

X-ray nanotomography of SiO2-coated Pt90Ir10 tips with sub-micron conducting apexAppl. Phys. Lett. 99, 173102 (2011)

Ultrathin ultrananocrystalline diamond film synthesis by direct current plasma-assisted chemical vapor deposition

J. Appl. Phys. 110, 084305 (2011)S-passivation of the Ge gate stack: Tuning the gate stack properties by changing the atomic layer depositionoxidant precursorJ. Appl. Phys. 110, 084907 (2011)

Anisotropic response of nanosized bismuth films upon femtosecond laser excitation monitored by ultrafastelectron diffractionAppl. Phys. Lett. 99, 161905 (2011)

Two-dimensional solid solution alloy of Bi-Pb binary films on Rh(111)J. Appl. Phys. 110, 074314 (2011)

Additional information on AIP Advances

Journal Homepage: http://aipadvances.aip.org

Journal Information: http://aipadvances.aip.org/about/journal

Top downloads: http://aipadvances.aip.org/most_downloaded

Information for Authors: http://aipadvances.aip.org/authors

Downloaded 08 Nov 2011 to 187.6.124.65. All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported license.See: http://creativecommons.org/licenses/by/3.0/
http://aipadvances.aip.org/search?sortby=newestdate&q=&searchzone=2&searchtype=searchin&faceted=faceted&key=AIP_ALL&possible1=Annapu%20Reddy%20Venkateswarlu&possible1zone=author&alias=&displayid=AIP&ver=pdfcovhttp://aipadvances.aip.org/search?sortby=newestdate&q=&searchzone=2&searchtype=searchin&faceted=faceted&key=AIP_ALL&possible1=G.%20D.%20Varma&possible1zone=author&alias=&displayid=AIP&ver=pdfcovhttp://aipadvances.aip.org/search?sortby=newestdate&q=&searchzone=2&searchtype=searchin&faceted=faceted&key=AIP_ALL&possible1=R.%20Nath&possible1zone=author&alias=&displayid=AIP&ver=pdfcovhttp://aipadvances.aip.org/?ver=pdfcovhttp://link.aip.org/link/doi/10.1063/1.3662093?ver=pdfcovhttp://aipadvances.aip.org/resource/1/AAIDBI/v1/i4?ver=pdfcovhttp://www.aip.org/?ver=pdfcovhttp://link.aip.org/link/doi/10.1063/1.3655907?ver=pdfcovhttp://link.aip.org/link/doi/10.1063/1.3652752?ver=pdfcovhttp://link.aip.org/link/doi/10.1063/1.3622514?ver=pdfcovhttp://link.aip.org/link/doi/10.1063/1.3652919?ver=pdfcovhttp://link.aip.org/link/doi/10.1063/1.3650883?ver=pdfcovhttp://aipadvances.aip.org/?ver=pdfcovhttp://aipadvances.aip.org/about/journal?ver=pdfcovhttp://aipadvances.aip.org/most_downloaded?ver=pdfcovhttp://aipadvances.aip.org/authors?ver=pdfcovhttp://aipadvances.aip.org/authors?ver=pdfcovhttp://aipadvances.aip.org/most_downloaded?ver=pdfcovhttp://aipadvances.aip.org/about/journal?ver=pdfcovhttp://aipadvances.aip.org/?ver=pdfcovhttp://link.aip.org/link/doi/10.1063/1.3650883?ver=pdfcovhttp://link.aip.org/link/doi/10.1063/1.3652919?ver=pdfcovhttp://link.aip.org/link/doi/10.1063/1.3622514?ver=pdfcovhttp://link.aip.org/link/doi/10.1063/1.3652752?ver=pdfcovhttp://link.aip.org/link/doi/10.1063/1.3655907?ver=pdfcovhttp://www.aip.org/?ver=pdfcovhttp://aipadvances.aip.org/resource/1/AAIDBI/v1/i4?ver=pdfcovhttp://link.aip.org/link/doi/10.1063/1.3662093?ver=pdfcovhttp://aipadvances.aip.org/?ver=pdfcovhttp://aipadvances.aip.org/search?sortby=newestdate&q=&searchzone=2&searchtype=searchin&faceted=faceted&key=AIP_ALL&possible1=R.%20Nath&possible1zone=author&alias=&displayid=AIP&ver=pdfcovhttp://aipadvances.aip.org/search?sortby=newestdate&q=&searchzone=2&searchtype=searchin&faceted=faceted&key=AIP_ALL&possible1=G.%20D.%20Varma&possible1zone=author&alias=&displayid=AIP&ver=pdfcovhttp://aipadvances.aip.org/search?sortby=newestdate&q=&searchzone=2&searchtype=searchin&faceted=faceted&key=AIP_ALL&possible1=Annapu%20Reddy%20Venkateswarlu&possible1zone=author&alias=&displayid=AIP&ver=pdfcovhttp://labs.aip.org/ipeerreview-1.219?ver=pdfcovhttp://aipadvances.aip.org/?ver=pdfcov


2/12

AIP ADVANCES 1, 042140 (2011)

Optical and electrical properties of spray pyrolysisdeposited nano-crystalline BiFeO3 films

Annapu Reddy Venkateswarlu,1, a G. D. Varma,2 and R. Nath1,b1Ferroelectric Materials and Devices Research Laboratory, Department of Physics, Indian

Institute of Technology Roorkee, Roorkee, Uttarakhand 247667, India2High Temperature Superconductivity Laboratory, Department of Physics, Indian Institute ofTechnology Roorkee, Roorkee, Uttarakhand 247667, India

(Received 20 July 2011; accepted 18 October 2011; published online 4 November 2011)

The nano-crystalline BiFeO3 werepreparedundercontrolledsubstratetemperaturebyspray pyrolysis method. Their structural,optical andelectrical properties were studiedand correlated. A blueshift ( 8.17 nm) in the absorbance peaks was observed inthe films with decrease in grain size. The absorption coefficient spectra show defecttransitions at 1.9 and 2.3 eV in large grain size films due to oxygen vacancies. Thelowest leakage was observed in smaller grain size (< 20 nm) films due to negligibleoxygen vacancies, smooth surface roughness and large energy bang gap. The Poole-Frankel conduction mechanism has been found to be the predominant mechanismfor the leakage current. Copyright 2011 Author(s). This article is distributed under aCreative Commons Attribution 3.0 Unported License. [doi:10.1063/1.3662093]

I. INTRODUCTION

Recently, nano-crystalline multiferroics, semiconductors, and metallic nano-particles have at-tracted a great attention because of their extensive applications in electrical, magnetical and opticaldevices.1, 2 Materials in the nano-crystalline phase become more interesting as the electrical, mag-netic and optical properties change drastically due to reduction of grain size. There has been largenumber of studies on electrical and optical properties of the nano-crystalline compound semicon-ductors but very few on multiferroics.37 A new class of materials, nano-clusters of the conventional

multiferroic semiconductors, is now very interesting because the physical as well as the electricalproperties of these systems are completely different from the bulk of the materials.

Bulk BiFeO3 (BFO) is ferroelectric (Tc 1100K) and anti-ferromagnetic (TN 640 K) atroom temperature.8 The structure is that of a rhombohedral distorted perovskite belonging to theR3C space group. Resent reports of a large spontaneous polarization (100 C/cm2) in thin films,bulk ceramics, and single crystals of BFO have led to deep interest in its growth and properties. 911

The multiferroic BFO can be utilized in a variety of devices that need the knowledge of its opticalproperties like band gap and refractive index. As the band gap of BFO is high in the range 2.3 to2.8 eV,1215 theleakage current at room temperature is expectedto be low. However nonstoichiometriccomposition in the BFO, impurity energy levels in band gap and oxygen vacancies may give riseto large leakage current.16 Recently it has been reported that BiFeO3-BiCrO3 nano-composite filmsshow lower leakage current due to grain size modifications accompanied by decrease in oxygenvacancies. However, there are only few studies on the optical and electrical properties of nano-crystalline films of BFO.1719 BFO is a multiferroic material and has potential applications inmagnetoelectric memory devices.

In this paper, we present the effect of grain size on the simultaneous study of the opticaland electrical properties in BFO films. The BFO films with varied grain sizes were obtained by

[email protected]@iitr.ernet.in

2158-3226/2011/1(4)/042140/11 C Author(s) 20111, 042140-1

http://dx.doi.org/10.1063/1.3662093http://dx.doi.org/10.1063/1.3662093http://dx.doi.org/10.1063/1.3662093http://dx.doi.org/10.1063/1.3662093http://dx.doi.org/10.1063/1.3662093mailto:%[email protected]:%[email protected]:%[email protected]:%[email protected]://dx.doi.org/10.1063/1.3662093http://dx.doi.org/10.1063/1.3662093http://dx.doi.org/10.1063/1.3662093


3/12

042140-2 Venkateswarlu, Varma, and Nath AIP Advances 1, 042140 (2011)

FIG. 1. Spray-pyrolysis experimental set-up.

preparing at different substrate temperatures. An attempt has been made to correlate the optical andthe electrical properties with the structural properties of nano-crystalline BFO films.

II. EXPERIMENTAL PROCEDURE

Figure 1 shows the schematic diagram of spray- pyrolysis setup fabricated and developed forthe deposition of BFO films. The deposition system consists of encapsulated nozzle with diameterof 0.8 mm and length of 7 cm in a teflon cylinder with a provision for carrier gas and the solution

to meet at the bottom of the cylinder. The compressed air was used as a carrier gas and the airflow line fitted with air filter was controlled with pressure gauges. The hot plate was attached to theprogrammable temperature controller to keep the substrate at a desired elevated temperature.

The films were deposited onto the ultra cleaned glass substrate 1x1.5 cm2 size. The bismuth ni-trate (5 mol. % excess) was dissolved in acetic acid and 2-methoxy ethanol (2:3) at room temperaturefor 5 h using a stirring mixer and iron nitrate was further dissolved into the stock solution. A solutionof 1 ml was sprayed in cone shape onto the hot substrate kept at a distance of 12 cm from the bottomof teflon cylinder. A solution flow rate of 0.1 ml/min and a carrier gas pressure of 2 kgcm-2 were usedfor the deposition of the films. The BFO films were deposited at the different substrate temperaturessuch as, 200, 250, 300, 350 and 400 C and were post annealed at the deposition temperatures for1h. The BFO films were annealed at temperature of 550 C in steps of 5 C/min for 2h in a closed



4/12


FIG. 2. Typical XRD patterns of BFO films deposited at 350 C and 400 C.

furnace to study the affect the optical and electrical properties. The thickness in the range 1.8 - 2.2m of the BFO films was measured using thickness profilometer.

The x-ray powder diffraction (XRD) data were obtained using an advanced Bruker D8 diffrac-tometer with CuK radiation. The crystalline size of the BFO films has been calculated by using theScherrer Formula:20

t =K

cos (1)

where t is the crystalline size, K is the shape factor, is the x-ray wavelength, is the line width atthe half maximum intensity and is the Bragg angle.

The atomic force microscopy was used to study the surface morphology and to obtain quan-titative information of the average particle size and root mean square (RMS) roughness of theBFO films. The optical studies were performed by measuring the transmittance, absorbance andreflectance of the BFO films on glass substrate in the wavelength region of 200 1200 nm using aspectrophotometer (Cary 5000, Varian).

III. RESULTS AND DISCUSSIONS

The x-ray diffraction (XRD) measurements were performed on BFO films deposited at differentsubstrate temperatures. Figure 2 shows the typical XRD patterns of the BFO films prepared at

substrate temperature (Ts) of 350 and 400

C. The intensity of peaks progressively increases up toTs = 350 C and falls off subsequently. Also the full width at half maxima (FWHM) of (110) planedecreases with Ts which indicates the improvement in the structural order in the films. This can beattributed to the increase in the film density.21 As seen from the spectra, the films have distortedrhombohedral structure with R space group without any impurities according to the JCPDS standards(PDF#20-0169). The average crystallite size was obtained using Eq. (1) and it varied from 15 to95 nm with increase in Ts from 200 C to 400 C. Table I shows the estimated structural parametersfrom the XRD measurements as a function of substrate temperature.

The surface morphology of the films was examined and the AFM images are shown in Fig. 3.The images show square shaped grains up to Ts = 350 C (Figs. 3(a) and 3(b)), and spherical shapedgrainsatTs = 400 C (Fig. 3(c)). The films deposited at Ts = 350 C are well oriented and crystalline



5/12


TABLE I. Various calculated parameters of the BFO films

BFO samples Grain size (nm) a() c() c/a V (3)

TS = 200 C 12.2 5.538 6.772 1.222 179.86TS = 250 C 13.8 5.540 6.786 1.224 180.36

TS = 300 C 21.4 5.542 6.799 1.227 180.84TS = 350 C 42.2 5.543 6.808 1.228 181.18TS = 400 C 92.4 5.550 6.819 1.229 181.89JCPDS (PDF#200169) 5.573 6.915 1.241 185.98

FIG. 3. AFM surface micrographs of the BFO films deposited at (a) 300 C, (b) 350 C, (c) 400 C and (d) the mean grainsize, D and RMS roughness as a function of substrate temperature.

in nature. The surface morphology of the deposited films is smooth and homogenous for the observedwhole area of the specimen. The clustering of the BFO particles was observed in the films grownat Ts=400 C. The formation of clustering is considered to result from high-speed migration of

deposited species in the case of the high temperature growth and relatively large internal free energybetween the substrate and the film.22 The observed mean grain size and root mean square surfaceroughness have been found to vary from 12.2 nm to 92.2 nm and 2.5 nm to 18 nm, respectively forthe BFO films when Ts was changed from 200 C to 400 C as seen in Fig. 3(d). This indicates thatthe surface of the spray deposited BFO thin films are very smooth. The average grain sizes in thefilms estimated from the AFM image were almost same as the crystallite sizes obtained from XRDanalysis. Therefore grains are composed of single crystallite of BFO.

The optical response such as transmittance, reflectance (not shown) and absorbance of the BFOfilms were observed in the wavelength range 300 1200 nm as shown in Fig. 4. The transmittancehas been expected to depend on several factors such as oxygen vacancies, grain boundaries, impuritycenters, crystalline nature and surface roughness. The percent transmittance in the visible region is



6/12


FIG. 4. (a) Transmittance and (b) absorbance spectra for BFO films with different grain size, D. Inset: close up view ofabsorbance below 450 nm.

high in the films with large grain size, which may be due to the decrease of light scattering fromgrain boundaries.23 The absorbance decreases with wavelength and is a maximum in the film withgrain size of 42 nm. A clear blueshift ( 8.17 nm) in the absorbance peaks is observed withdecreasing grain size as shown in inset Fig. 4(b). This indicates that the strain in the BFO filmsincreases with decreasing grain size24, 25 and it was also confirmed from the XRD analysis.

To reveal the origin of the blueshift in absorbance, the value of absorption coefficient () isneeded and was calculated using Eq. (2). Assuming the interference and multiple reflections withinthe films as well as at the film-substrate interface to be negligible and a near normal incidence of



7/12


FIG. 5. Absorption coefficient () as a function of wavelength of the BFO films with different grain size. Inset: the plots ofd/dE vs. h.

radiation, is given by,26, 27

=1

dln

1 R

T

(2)

where d is the thickness, R is the reflectance and T is the transmittance of the film. The absorptioncoefficient spectra of the BFO films are shown in fig. 5 and the is about an order of magnitude

greater than that of other ferroelectric thin films such as PbTiO3,28 Pb(Zr,Ti)O3,29 (Pb,La)(Zr,Ti)O330in the wavelength region 400 1200 nm. It indicates that the BFO films are excellent candidate forinfrared detectors. The absorption coefficient values can be used to determine the optical energygap.31 However, the calculated valence band in the rhombohedral state is almost flat so that BFO canbe taken as a direct-band gap semiconductor at room temperature.13 The energy band gap thereforecan be estimated using the following expression for direct band gap materials,31

h = K

h Eg 1

2 (3)

where K is a constant, Eg is the band gap and h is the photon energy. The band gap was determinedby extrapolating the straight line portion of the spectrum to h = 0 [Fig. 6)]. The values of Eg, soobtained are plotted as a function of grain size in inset Fig. 6. The band gap energy Eg show large

increase in the films with grain size below 20 nm. The grain size dependence of band gap indicatesthat the FeO6 local structure distortion is reduced in films with large grain size.32 Considering theinverse dependence of the band gap on the lattice parameters, which means one can say that smallerin-plane latticeparametersfor the BFO films can result in small grain size films. The band gapenergy,Eg 3.2 eV for the 12 nm grain size BFO film is good agreement with the theoretically calculatedband gap of Eg = 3.3 eV from the Quasi-particle Self-consistent GW (QPGW) approximationmodel33 and the experimental obtained Eg values for tetragonal BFO thin films.34 The large valueof Eg may be due to change in crystal structure parameters, local structure distortion of FeO 6 andthe strain variation with grain size. The increasing trend in Eg with the decrease in grain size may bedue to the modification of the band structure that is narrowing of both the valence and conductionbands, as in the case of low dimensional semiconducting systems.35



8/12


FIG. 6. Plots of (h)2 vs. h of the BFO films with different grain size. Inset: the variation in band gap with the averagegrain size of BFO.

The refractive index (nr) and extinction coefficients (k) for the BFO films were calculated usingthe reflectance and absorbance spectra from the following expressions: 36, 37

k=

4(4)

nr =1+ R

1 R+ 4R

(1 R)2 k2 (5)

The refractive index and extinction coefficient (k) as a function of wavelength in the range 300 nm-1200 nm are plotted as shown in Fig. 7(a) and 7(b). The values of nr and k increase with wavelength,and nr at 1200 nm decreases from 4.3 to 2.4 with the grain size. The extinction coefficient valuesshow similar trend with grain size as the absorption coefficient. The data agrees well with otherpublished data for BFO films deposited on STO substrates in the measured wavelength range.25 Ablueshift of 8.17 nm for the extinction coefficient peaks is also observed in the BFO films withdecreasing grain size. The refractive index of 3.51 is estimated at a wavelength of 1200 nm for theBFO films containing grain size 42 nm which suggests their potential for optical communicationsapplication.

The polarizability in solids is proportional to its dielectric constant. The real and imaginaryparts of the complex dielectric constants are given as,38

1 = 2n2r k2 and 2 = 2nr k (6)

where 1 is the real part and 2 is the imaginary part of the dielectric constant. The imaginary and realparts of the dielectric constants are directly related to the density of the states within the forbiddengap of the compounds. The 1 and 2 values are calculated by using the values of nr and k asshown in Fig. 7(c) and 7(d). The physical mechanism responsible for the grain size on the dielectricconstant can be explained as the change of the crystalline field caused by surface bond contraction.The nano-crystalline films have an enhanced crystalline field due to its surface bond contraction andthe rise in the surface area to volume ratio. The 1 increase with grain size can be attributed to thedecrease in crystal field.39 The dielectric loss 2 exhibits maximum at 400 nm (E 3.1 eV), andsimilar energy position was calculated using density functional theory for the imaginary part of the



9/12


FIG. 7. (a) Extinction coefficient, (b) refractive index, (c) real and (d) imaginary parts of dielectric constant as a function ofwavelength of the BFO films with different grain size.

dielectric constant of BFO.40 The peak at 3.1 eV can be attributed to transitions from the occupiedO 2p to unoccupied Fe 3d states or to d-d transitions between the Fe 3d valence and conductionbands.40 The dielectric loss 2 of the BFO films is about an order of magnitude smaller than reportedearlier.25 This shows good quality of films produced by spray pyrolysis method and

2is least for

the smallest grain size films.The leakage current in the BFO films was measured as a function of applied voltage as shown

in Fig. 8(a). The leakage current was found to vary from 1.0 x 10-3 to 1.8x10-3 A/cm2 at 8 Vwith increase grain size in the films. The observed leakage current of the BFO films is about twoorder magnitudes lower than recently reported by others.16, 41, 42 It could be due to suppression ofimpurity phases, oxygen vacancies, smooth surface morphology and large energy band gap in thenano-crystalline BFO films. The leakage current is low in smaller grain size films. It could be due toincrease grain boundaries and which impede the flow of charge carriers. If the grain size is smallerthan the electron mean free path, grain boundary scattering dominates and hence the leakage currentdecreases.43, 44 The leakage current is also very sensitive to lattice imperfections in solids, such asvacancies and dislocations which are reported to be present in nano-crystalline materials.4547 Inaddition to that, lattice strain and the distortions can affect the motion of charge causing decrease in

the leakage current.In the inset of Fig. 5, d/dE is plotted as a function of energy and different peaks were locatedat 1.9 and 2.3 eV in large grain size (21 92 nm) BFO films. Such peaks were also detected forepitaxial BFO films deposited on STOand were confirmed by cathodoluminescencemeasurements.48

These peaks are considered to be defect states most likely due to oxygen vacancies in the BFO films.Therefore low leakage current in the smaller grain size (< 20 nm) films can be attributed to thenegligible oxygen vacancies in these films. The variation of leakage current can also be correlatedto the optical energy band gap of the BFO films and is expected to be small for a large energy gap(smaller grain size) films.

The leakage current was found to be sensitive to grain size hence bulk limited mechanism maybe responsible. The space-charge-limited conduction (SCLC) is one of the bulk limited mechanism.



10/12


FIG. 8. (a) Typical leakage current data and (b) plots of ln() vs. V0.5 of the BFO films. Inset in (a): schematic drawing of

device structure.

Here the limitation arises from a current impeding space charge formation as charges are injectedinto the film from the electrode at a rate faster than they can travel through the film. The currentdensity for SCLC is given by,49

JSCLC =90kV2

8d2(7)

where is carrier mobility. The leakage current as a function of V2 was plotted to know the presencebulk limited SCLC mechanism (curve not shown). It was found that J vs. V 2 plots do not fit into a



11/12


straight line. Therefore the SCLC mechanism can be ruled out as the origin of leakage current in theBFO films.

Another bulk-limited mechanism is known as Poole-Frenkel emission from the ionization of thetrap charges can both be thermally and field activated. The expression for Poole-Frenkel conductivityis given by,50

= C exp

EI

kB Tk

1

kB Tk

q3V

0kd

12

(8)

where C is a constant, EI is the trap ionization energy, is the conductivity, is the dielectricconstant, Tk is the temperature and d is thickness of the film. Figure.8(b) shows plots of ln vs. V0.5,which exhibit good theoretical fit to Eq. (8). The dielectric constant of the BFO films was extractedfrom the slopes of these plots and was found to vary from 5.05 to 3.68 with increasing grain size inthe films. The dielectric constant of the films is better in agreement with optical data of 1 5.0 at420 nm for 12 nm grain size film. The Poole-Frankel emission can be the dominant leakage currentmechanism in the BFO films. The Poole-Frankel was observed in BFO51 and other ferroelectricperovskites such as PZT52 under high applied fields. In the case of BFO, the likely trap center is theFe ions and it is widely accepted that oxygen vacancies formed during growth cause a portion of

the Fe3+

ions to become Fe2+

. These Fe ions are often considered to be responsible for the leakagecurrent of the BFO and show Poole-Frankel conduction mechanism.

IV. CONCLUSIONS

The optical, electrical and structural properties of spray deposited BFO films were studied. Theabsorption spectra of the films show large band gap for small grain size films. The d/dE plotsshow that oxygen vacancies substantially reduce in case of small grain size films. The small grainsize films of BFO can have potential applications in communication and magnetoelectric memorydevices.

ACKNOWLEDGMENT

The authors acknowledge the financial support provided by Indian Institute of TechnologyRoorkee, and Ministry of Human Resources and Development (MHRD), India. The author is pleasedto thank to Dr.Vipul Rastogi for the technical assistance.

1 Henglin A, Chem. Rev. 89 1861 (1989).2 Agfeldt A and Gratzel M, Chem.Rev. 95, 49 (1995).3 Banerjee R, Jayakrishnan R and Ayyub P, J. Phys.: Condens. Matter 12, 10647 (2000).4 Ganeev R A, Baba M, Morita M, Rau D, Fujii H, Ryasnyansky A I, Ishizawa N, Suzuki M and Kuroda H, J.Opt. A:

Pure Appl. Opt. 6, 447 (2004).5 Beecroft L L and Ober C K, Chem. Mater. 9, 1302 (1997).6 Liu Y C, Xu H Y, Mu R, Henderson D O, Lu Y M, Zhang J Y, Shen D Z, Fan X W and White C W, Appl. Phys.

Lett. 83, 1210 (2003).7 S. J. Clark and J. Robertson, Appl. Phys. Lett. 90, 132903 (2007).8 P. Fischer, M. Polomska, I. Sosnowska, and M. Szymanskig, J.Phys.C 13, 1931 (1980).9 Seung-Hyub Baek,Chad M. Folkman,Jae-Wan Park, Sanghan Lee, Chung-WungBark, Thomas Tybell, Chang-BeomEom,

Adv.Mater.xx, 1-5 (2011).10 V. V. Shvartsman, W. Kleemann, R. Haumont, and J. Kreisel, Appl. Phys. Lett. 90, 172115 (2007).11 D. Lebeugle, D. Colson, A. Forget, M. Viret, P. Bonville, J. F. Marucco, and S. Fusil, Phys. Rev. B 76, 024116 (2007).12 J. B. Neaton, C. Ederer, U. V. Waghmare, N. A. Spaldin, and K. M. Rabe, Phys.Rev.B 71, 014113 (2005).13 S. J. Clark and J. Robertson, Appl.Phys.Lett. 90, 132903 (2007).14 R. Palai, R. S. Katiyar, H. Schmid, P. Tissot, S. J. Clark, J. Robertson, S. A. T. Redfern, G. Catalan, J. F. Scott, Phys, Rev.B,77, 014110 (2008).

15 Y. Xu, M. Shen, Mat.Lett. 62, 3600 (2008).16 Takeshi Kawae, Hisashi Tsuda, and Akiharu Morimoto, Appl.Phys.Express 1, 051601 (2008).17 V. Fruth, E. Tenea, M. Gartner, A. Anastasescu, D. Berger, R. Ramer, and M. Zaharescu, J. Eur. Ceram. Soc. 27, 937

(2007).18 T. Kanai, S. Ohkoshi, and K. Hashimoto, J. Phys. Chem. Solids 64, 391 (2003).19 F. Gao, Y. Yuan, K. F. Wang, X. Y. Chen, F. Chen, and J. M. Liu, Appl. Phys. Lett. 89, 102506 (2006).

http://dx.doi.org/10.1021/cr00098a010http://dx.doi.org/10.1021/cr00033a003http://dx.doi.org/10.1088/0953-8984/12/50/325http://dx.doi.org/10.1088/1464-4258/6/4/024http://dx.doi.org/10.1088/1464-4258/6/4/024http://dx.doi.org/10.1021/cm960441ahttp://dx.doi.org/10.1063/1.1591248http://dx.doi.org/10.1063/1.1591248http://dx.doi.org/10.1063/1.2716868http://dx.doi.org/10.1088/0022-3719/13/10/012http://dx.doi.org/10.1063/1.2731312http://dx.doi.org/10.1103/PhysRevB.76.024116http://dx.doi.org/10.1103/PhysRevB.71.014113http://dx.doi.org/10.1063/1.2716868http://dx.doi.org/10.1103/PhysRevB.77.014110http://dx.doi.org/10.1103/PhysRevB.77.014110http://dx.doi.org/10.1016/j.matlet.2008.04.006http://dx.doi.org/10.1143/APEX.1.051601http://dx.doi.org/10.1016/j.jeurceramsoc.2006.04.135http://dx.doi.org/10.1016/S0022-3697(02)00284-6http://dx.doi.org/10.1063/1.2345825http://dx.doi.org/10.1063/1.2345825http://dx.doi.org/10.1016/S0022-3697(02)00284-6http://dx.doi.org/10.1016/j.jeurceramsoc.2006.04.135http://dx.doi.org/10.1143/APEX.1.051601http://dx.doi.org/10.1016/j.matlet.2008.04.006http://dx.doi.org/10.1103/PhysRevB.77.014110http://dx.doi.org/10.1063/1.2716868http://dx.doi.org/10.1103/PhysRevB.71.014113http://dx.doi.org/10.1103/PhysRevB.76.024116http://dx.doi.org/10.1063/1.2731312http://dx.doi.org/10.1088/0022-3719/13/10/012http://dx.doi.org/10.1063/1.2716868http://dx.doi.org/10.1063/1.1591248http://dx.doi.org/10.1063/1.1591248http://dx.doi.org/10.1021/cm960441ahttp://dx.doi.org/10.1088/1464-4258/6/4/024http://dx.doi.org/10.1088/1464-4258/6/4/024http://dx.doi.org/10.1088/0953-8984/12/50/325http://dx.doi.org/10.1021/cr00033a003http://dx.doi.org/10.1021/cr00098a010


12/12


20 Waren B E, X-ray diffraction (Reading, MA: Addison-Wesely) p-26419.21 B. Elidrissi, M. Addo, M. Regragui, C. Monty, A. Bougrine, and A. Kachouane, Thin Solid Films 379, 23 (2000).22 Moses A. E. R, Nehru L. C, Jayachandra M, and Sanjeeviraja C, Cryst.Res.Technol.42, 867 (2007).23 S. Logothetidis, J. Appl. Phys. 65, 2416 (1983).24 A. Kumar, R. C. Rai, N. J. Podraza, S. Denev, M. Ramirez, Y.-H. Chu, L. W. Martin, J. Ihlefeld, T. Heeg, J. Schubert,

D. G. Schlom, J. Orenstein, R. Ramesh, R. W. Collins, J. L. Musfeldt, and V. Gopalan, Appl. Phys. Lett. 92, 121915 (2008).25

CameliuHimcinschi, Ionela Vrejoiu, Marion Friedrich,Li Ding, ChristophCobet, NorbertEsser,Marin Alexe, and DietrichR. T. Zahn, Phys. Status Solidi C 7, 296 (2010).26 K. L. Chopra, Thin Film Phenomena (Mc Graw-Hill, New York, 1969).27 J. C. Manifacier, M. D. Murcia, J. P. Fillard, E. Vicario, Thin Solid Films 41 127 (1997).28 Z. G. Hu, F. W. Shi, T. Lin, Z. M. Huang, G. S. Wang, Y. N. Wu, J. H. Chu, Phys. Lett. A 320, 478 (2004).29 F. W. Shi, Z. G. Hu, G. S. Wang, T. Lin, J. H. Ma, X. J. Meng, J. L. Sun, J. H. Chu, Thin Solid Films 458, 223 (2004).30 Z. Huang, X. Meng, Z. Zhang, J. Chu, J. Phys. D Appl. Phys. 35, 246 (2002).31 Pancov J, Optical Processes in Semiconductors (Englewood Cliffs, NJ: Prentice-Hall, 1979).32 Peng Chen, Xiaoshan Xu, Christopher Koenigsmann, Alexander C. Santulli, Stanislaus S. Wong, and Janice L. Musfeldt,

Nano Lett. 10, 4526 (2010).33 Vilas Shelke, Dipanjan Mazumdar, Sergey Faleev, Oleg Mryasov, Stephen jesse, Sergei Kalinin, Arthur Baddorf and

Arunava Gupta, Materials Science, arXiv:1010.0604v2.34 P. Chen, N. J. Podraza, X. S. Xu, A. Melville, E. Vlahos, V. Gopalan, R. Ramesh, D. G. Schlom, and J. L. Musfeldt, Appl.

Phys. Lett. 96, 131907 (2010).35 A. D. Yoffe, Adv.phys. 42, 173 (1993).36 N. Benramdane, W. A. Murad, R. H. Misho, M. Ziane, Z. Kebbab, Mater. Chem. Phys. 48, 119 (1997).37

Swanepoel R, J. Phys., E J. Sci. Instrum, 16, 1214 (1983).38 T. Wiktorezyk, Thin Solid Films 405, 238 (2002).39 Chang Q. Sun, Progress in Solid State Chemistry, 35, 1 (2007).40 H. Wang, Y. Zheng, M.-Q. Cai, H. Huang, and H. L. W. Chan, Solid State Commun. 149, 641 (2009).41 H. Yang, Y. Q. Wang, 2 H. Wang, and Q. X. Jia, Appl. Phys. Lett. 96, 012909 (2010).42 T. Choi, S. Lee, Y. J. Choi, V. Kiryukhin, W. W. Chong, Science, 324, 3 (2009).43 J. E. Brus, J. Chem. Phys. 80, 4403 (1984).44 A. D. Yoffe, Adv. Phys. 42, 173 (1993).45 Y. Z. Wang, G. W. Qiao, X. D. Liu, B. Z. Ding, and Z. Q. Hu, Mater. Lett. 17, 152 (1993).46 I. Bakonyi, E. Toth-Kadar, T. Tarnoczi, L. Varga, A. Cziraki, I. Gerocs, and B. Fogarassy, Nanostruct. Mater. 3, 155 (1993).47 L. Wu, W. Tien-Shou, and W. Chung-Chuang, J. Phys. D: Appl. Phys. 13, 259 (1980).48 A. J. Hauser, J. Zhang, L. Miee, R. A. Ricciardo, P. M. Woodward, T. L. Gustafson, L. J. Brillson, and F. Y. Yang, Appl.

Phys. Lett. 92, 222901 (2008).49 M. A. Lampert and P. Mark, Current Injection in Solids (Academic, New York, 1970).50 J. Frenkel, Tech. Phys. USSR 5, 685 (1938).51 G. W. Pabst, L. W. Martin, Y. H. Chu, and R. Ramesh, Appl. Phys. Lett. 90, 072902 (2007).52

B. Nagaraj, S. Aggarwal, T. K. Song, T. Sawhney, and R. Ramesh, Phys. Rev. B59

, 16022 (1999).
http://dx.doi.org/10.1016/S0040-6090(00)01404-8http://dx.doi.org/10.1002/crat.200710918http://dx.doi.org/10.1063/1.343401http://dx.doi.org/10.1063/1.2901168http://dx.doi.org/10.1002/pssc.200982414http://dx.doi.org/10.1016/0040-6090(77)90395-9http://dx.doi.org/10.1016/j.physleta.2003.12.003http://dx.doi.org/10.1016/j.tsf.2003.09.059http://dx.doi.org/10.1088/0022-3727/35/3/313http://dx.doi.org/10.1021/nl102470fhttp://dx.doi.org/10.1063/1.3364133http://dx.doi.org/10.1063/1.3364133http://dx.doi.org/10.1080/00018739300101484http://dx.doi.org/10.1016/S0254-0584(97)80104-6http://dx.doi.org/10.1088/0022-3735/16/12/023http://dx.doi.org/10.1088/0022-3735/16/12/023http://dx.doi.org/10.1016/S0040-6090(01)01760-6http://dx.doi.org/10.1016/j.progsolidstchem.2006.03.001http://dx.doi.org/10.1016/j.progsolidstchem.2006.03.001http://dx.doi.org/10.1016/j.ssc.2009.01.023http://dx.doi.org/10.1063/1.3291044http://dx.doi.org/10.1063/1.447218http://dx.doi.org/10.1080/00018739300101484http://dx.doi.org/10.1016/0167-577X(93)90075-9http://dx.doi.org/10.1016/0965-9773(93)90073-Khttp://dx.doi.org/10.1088/0022-3727/13/2/023http://dx.doi.org/10.1063/1.2939101http://dx.doi.org/10.1063/1.2939101http://dx.doi.org/10.1063/1.2535663http://dx.doi.org/10.1103/PhysRevB.59.16022http://dx.doi.org/10.1103/PhysRevB.59.16022http://dx.doi.org/10.1063/1.2535663http://dx.doi.org/10.1063/1.2939101http://dx.doi.org/10.1063/1.2939101http://dx.doi.org/10.1088/0022-3727/13/2/023http://dx.doi.org/10.1016/0965-9773(93)90073-Khttp://dx.doi.org/10.1016/0167-577X(93)90075-9http://dx.doi.org/10.1080/00018739300101484http://dx.doi.org/10.1063/1.447218http://dx.doi.org/10.1063/1.3291044http://dx.doi.org/10.1016/j.ssc.2009.01.023http://dx.doi.org/10.1016/j.progsolidstchem.2006.03.001http://dx.doi.org/10.1016/S0040-6090(01)01760-6http://dx.doi.org/10.1088/0022-3735/16/12/023http://dx.doi.org/10.1016/S0254-0584(97)80104-6http://dx.doi.org/10.1080/00018739300101484http://dx.doi.org/10.1063/1.3364133http://dx.doi.org/10.1063/1.3364133http://dx.doi.org/10.1021/nl102470fhttp://dx.doi.org/10.1088/0022-3727/35/3/313http://dx.doi.org/10.1016/j.tsf.2003.09.059http://dx.doi.org/10.1016/j.physleta.2003.12.003http://dx.doi.org/10.1016/0040-6090(77)90395-9http://dx.doi.org/10.1002/pssc.200982414http://dx.doi.org/10.1063/1.2901168http://dx.doi.org/10.1063/1.343401http://dx.doi.org/10.1002/crat.200710918http://dx.doi.org/10.1016/S0040-6090(00)01404-8

Documents

Optical and Electrical Properties of Spray Pyrolysis Deposited Nano-crystalline BFO Films