Growth of Nano Scale and Optical Properties of Indium Oxide Thin Films
Research Scholar, Physics Department1 , Om Sterling Global University, Hisar, Haryana (India)2 Associate professor, ECE Department, Om Sterling Global University, Hisar, Haryana (India) ***
Abstract - In the present paper it has been identified that indium oxide nanoparticles (InO-NPs) have different key of interest because of their unique shape and size dependent properties. Various methods have been developed by researchers for synthesis of indium oxide nanoparticles on basis of structural and optical properties. In this present paper deposition of Indium oxide (In2O3) thin films was done on glass substrate by variation of temperature in the range of 4000C to 6000C. Then study of optical properties of indium oxide thin films were done and then at different temperatures nanocrystalline sizes of indium oxide nanoparticles were studied. Characterization of all films was done at room temperature by using X-ray diffraction To obtain high crystallographic quality of films, observed suitable substrate temperature was noticed which was 5750C.
Keywords: Indium oxide, nanoparticles, synthesis, optical properties.
1. INTRODUCTION
Thin films of Indium oxide (In2O3) are technologically important transparent conducting oxide (TCO) material. Theseareusedindifferentfields like:photovoltaicdevices [1], transparent windows in LCD [2], gas sensors [3], antireflectioncoatings[4],electro-chromicdevices[5],and solarcells[6].PreparationofthinfilmsofIn2O3 canbedone byavarioustechniqueslikechemicalvaporsdeposition[7], chemicaldecompositionofasubstancebyheat[8],vacuum evaporation[9],andmagnetronsputtering[10].Among all the techniques the most commonly used technique for deposition of TCO is chemical decomposition of substance by heat technique is most suitable due to its clearness and non-vacuum deposition system which is not so expansive. This can be modified for large production of quality oxide thin films over large scale. Indium oxide (In2O3) thin films are transparent conducting n-type semiconductors having energy band gap of 3.6eV. The structure of Indium oxide (In2O3) is body centered cubic (BCC) in crystalline form havinglatticeconstanta=10:118Å[11].
1.1 EXPERIMENT
In this present work preparation of In2O3 thin films were done on glass substrates of soda lime by using chemical decomposition of a substance by heat technique. The
apparatususedinthisprocesscontainofasubstrateholder with heater, a homemade spraying unit, and an enclosure. Theglasssubstratewasplaced onaplateofstainlesssteel. The heater can heat the substrate up to 7000°C temperature.Preparationofindiumoxide(In2O3)thinfilms was done by dissolution of InCl3 (0.2 g) with 5 droplets of HClacidandrefluxheatingat9000Cfor5min.Thesolution was sprayed normally on the glass substrate which was heatedatdifferentsubstratetemperatures.Aircompressor wasusedforsupplyingthecarriergas(air) Filtrationofair produced by compressor was done then passed through spraygunusinganownmeterforcontrolledflowofair.
Deposition Parameters includes: separation between the substratesandspraynozzlewas25cm,filteredcompressed air used as the carrier gas, and the spray rate was 19lper min, and solution taken was 40 ml. All parameters except temperature were kept constant. And temperature variation was (4000°C–6000°C) UV-visible spectrophotometer was used for measurement of Optical transmission of the samples. Optical transmission to near (infrared region) was performed the PL (photoluminescence) measurements were done at room temperature. The source of excitation was 320nm lines of He-Cdlaser,anda320nmfilter.
2. RESULT AND DISCUSSIONS
The XRD patterns as a function of substrate temperature for indium oxide thin films were shown in figure 1 (af).From results it can be observed that the nature of film deposited was amorphous at 4000C and polycrystalline nature of films can be observed by increasing the temperature ofthesubstrateandpreferred orientationsof (400), (222) overcome The cubic box byte structure [12] wasconfirmedbythepeaksofinXRDpattern.
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0 25 50 75 100 125 150 175 200 225 250 275 20 24 28 32 36 40 44 48 52 56 60 64 68 72
Luminous Intensity 2Ɵ
Chart - 1 (a): Graphbetween2Ɵandluminousintensityat 6000C
Luminous Intensity 2Ɵ
T = 600°C (22 2) 0 25 50 75 100 125 150 175 200 225 250 275 20 23 26 29 32 35 38 41 44 47 50 53 56 59 62 65 68 71 74
Luminous Intensity 2Ɵ
0 25 50 75 100 125 150 175 200 225 250 275 20 22.8 25.6 28.4 31.2 34 36.8 39.6 42.4 45.2 48 50.8 53.6 56.4 59.2 62 64.8 67.6 70.4 73.2
T = 575°C (222)
T = 500°C (222)
Chart - 1 (b): Graphbetween2Ɵandluminousintensityat 5750C
(400)
Luminous Intensity 2Ɵ
T=550°C (222)
(400) 0 25 50 75 100 125 150 175 200 225 250 275 20 23 26 29 32 35 38 41 44 47 50 53 56 59 62 65 68 71 74
Chart - 1 (c): Graphbetween2Ɵandluminousintensityat 5500C
Chart - 1 (d): Graphbetween2Ɵandluminousintensityat 5000C
Luminous Intensity 2Ɵ
(400) (211) (440) (622) 0 25 50 75 100 125 150 175 200 225 250 275 20 23 26 29 32 35 38 41 44 47 50 53 56 59 62 65 68 71 74
T=450°C (211)
Chart - 1(e): Graphbetween2Ɵandluminousintensityat 4500C
Luminous Intensity 2Ɵ
(222) (400) (411) (341) (440) (622) 0 25 50 75 100 125 150 175 200 225 250 275 20 22.6 25.2 27.8 30.4 33 35.6 38.2 40.8 43.4 46 48.6 51.2 53.8 56.4 59 61.6 64.2 66.8 69.4 72 74.6
T = 400°C
Chart - 1 (f): Graphbetween2Ɵandluminousintensityat 4000C
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temperature in range of 5750C to 6000C, the size of grain decreases from 36.02 nm to 33.55nm, decrement in the grain size is accompanied with increment of sheet resistance and results in decrement of mobility. The scanning electron microscope (SEM) images of indium oxide (In2O3) thin films pre-pared at different substrate temperatures. As indicated by scanning electron microscope (SEM) photographs, films deposited at 400 0C have amorphous and non-uniform surface. It is evident from the results that the surface morphology (especially grains dimension) of films were highly affected by increasing the substrate temperature. At lower temperatures the deposited films was not having appropriate surface morphology, while structure improvementandincrementinuniformityoffilmscouldbe observed by increasing substrate temperature. Evident from to the XRD spectra, increment in substrate temperature from4000C to 5500C all films results in the polycrystalline structure with (400) and (222) being the leadingorientations.
Chart – 3: OpticaltransmissionofIn2O3filmspreparedat differentsubstratetemperature
Fromfigure1 itcan be observed that,the XRDintensityof favored growth orientation was mainly determined by the substrate temperature. The ratio of intensity for the peaks (400) and (222) was comparable at Ts= 4500C. The degree of (400) orientation increases by increasing substrate temperature up to Ts= 5750C, after that there was a measurable decrease in extent of (400) orientation and increase in (222) orientation on increasing substrate temperature up to 6000C. Scherer’s formula [13] was used for calculation of mean crystallite size D for the diffraction peaks:
Where k is constant value, is angle of scattering and is FWHM (full width at half maximum). On raising substrate
The grains start to grow on increasing the substrate temperature and the surface roofed fully with fine and large grains. There is decrement in the density of grain boundary with increment in the grain size, as a result crystallinestructurewasproved(specificsharppeaks)and resulted better optical property (high transmittance) (Chart 1 and Chart 3). Distinctive AFM images of indium oxide (In2O3) films deposited at different substrate temperature were shown in Chart 3. As it is evident from the figure that the substrate temperature measurably affects the surface morphology of the deposited films, lower temperature deposited films not have appropriate surface quality. While on increasing the substrate temperature (5750C to 6000C) results in better surface quality and crystallographic structure This was in conformity with XRD and SEM examination. Photoluminescence measurements were performed for investigatingtheopticalproperties ofindiumoxide(In2O3) thin films. Chart 3 results the Photoluminescence (PL) emission spectra, the carrier concentration and the conductivityenhancement(Table1)[14].
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On further increment in substrate temperature (5500C to 6000C) the XRD spectrum showed improvement in films deposited at different substrate temperature with incident beam of about 320 nm. As observed, 320 nm incident wavelengths were in UV range but obtained peaks were in the visible solar spectrum. A well-built near band edge ultraviolet emission peak could be noticed for all samples. It could be understood that photoluminescence (PL) spectra depend on the structure and the stoichiometry of the deposited films [15-16]. So, the photoluminescence (PL) results confirmed that the deposited optimums In2O3 are thin films are very close to stoichiometry and have optically high quality. This was remarkable for prepared sample at substrate temperature of 5750C. Photoluminescence peak of prepared sample at deposition temperature 450◦C also has good width but intensity was smaller than the film deposited at 5750C. The captivated peak in 425 nm wavelength for deposited sample at deposition temperature 4500C was companionable with sharppeaksofXRDspectrum.
Fromphotoluminescence(PL)diagramitcanbeconcluded that with increase in the deposition temperature, the crystalline improvement take place and the indium oxide filmsgetsbetterstructure,butforfilmsdepositedat6000C, the intensity of photoluminescence peak reduced significantlywhichwasingoodaccordwiththeXRDresults (Chart 1). The optical transmittance curves verses wavelength for the indium oxide (In2O3) thin films deposited at different substrate temperatures were shown in figure 2. It could be noticed that the optical transmittance of the films were affected by the deposition temperature.Theopticaltransmittancenoticedinthefilms alteredfrom13%to77%withtheincrementofdeposition temperature. The high transmittance noticed in the films was recognized to less scattering effects, better crystalline and structural homogeneity. A shift in the absorption edge was noticed to shorter wavelength for the optimal film, whichwasinagreementwiththeBursteinMossshift[17].
3. CONCLUSION
Thin films of indium oxide (In2O3) were deposited by chemical decomposition of a substance by heat vertically onto glass (soda lime) substrates using unheated (room temperature)0.023MInCl3solution.Substratetemperature was ranging from 4000C to 6000C Results showed that the substrate temperatures were remarkable parameters and have a remarkable effect on physical properties of the deposited films. Structural, morphological, optical and electrical properties of the films were observed and optimized conditions were achieved. The X-ray diffraction study showed that the films deposited at substrate temperature of 400 0C were amorphous while those deposited at temperatures 4500C were polycrystalline. By using Scherer’s formula for two temperatures grain size wascalculatedandfoundinconnectionwithSEM.TheSEM
andAFManalysisshowedthat atsubstrate temperatureof 5750C, the deposited films exhibit more smoothness and better crystallographic structure. In photoluminence (PL)analyses, the results confirmed that the deposited optimum indium oxide (In2O3) thin films are very close to stoichiometry and are of optically high quality particularly at substrate temperature of 5750C.The electrical resistivity of deposited films was variable but the best result was regarded to career mobility is at 5750C in agreement with otheranalysisforhigherconductivity.
REFERENCES
[1] M.K.Fung,Y.C.Sun,A.Ng,A.M.C.Ng,A.B.Djuristic,H.T. Chan and W.K. Chan, “Indium tin oxide nanorod electrodes for polymer photovoltaics,”ACS Applied Materials&Interfaces,vol.3,no.2,pp.522-527,2011.
[2] X. Yan, F.W. Mont, D.J. Poxson, M.F. Schubert, J.K. Kim, J. Cho and E.F. Schubert, “Refractive-index-matched indium–tin-oxide electrodes for liquid crystal displays”Jpn.J.Appl.Phys.vol.48,pp.120203,2009.
[3] L. Guo, X. Shen, G. Zhu and K. Chen, “Preparation and gas-sensing performance of In2O3 porous nanoplatelets”Sens. Actuators B: Chem., vol. 155 no. 2, pp. 752-758,2011 [doi:10.1016/j.snb.2011.01.042].
[4] J. Zhang, X. Chen and Z. Wang, “High-damagethreshold broadband chirped mirror,”Chin. Opt. Lett,vol.8,pp.156-158,2010.
[5] C.M.White,D.T.Gillaspie,E.Whitney,S.H.LeeandA.C. Dillon, “Flexible electrochromic devices based on crystalline WO3 nanostructures produced with hotwirechemical vapordeposition,” ThinSolidfilms,vol. 517,pp.3596-3599,2009.
[6] J.A.AnnaSelvan,A.E.Delahoy,S.GuoandY.Li,“Anew light trapping TCO for nc-Si: H solar cells,”Solar Energy Materials and Solar Cells,vol. 90, no. 18, pp. 3371-3376,2006.
[7] G.Cheng,E.Stern,S.Guthrie,M.A.Reed,R.Klie,Y.Hao, G. Meng and L. Zhang, “Indium oxide nanostructures,”Applied Physics A,vol. 85, no. 3, pp. 233-240,2006.
[8] N.Memarian,S.M.Rozati,E.Elamurugu,E.Fortu-nato, Structural and Electrical Properties of SnO₂: F Thin Films Prepared by Chemical Vapor Deposition Method.Acta Physica Polonica A,vol. 131, no. 2, pp. 222-225,2010.
[9] S. Golshahi, S.M. Rozati, R. Martins and E. Fortunato, “P-type ZnO thin film deposited by spray pyrolysis technique: The effect of solution concentration,”Thin SolidFilms,vol.518,no.4,pp.1149-1152,2009.
International Research Journal of Engineering and Technology (IRJET)
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[10] S. Boycheva, A.K. Sytchkova, M.L. Grilli and A. Piegari, “Structural, optical and electrical peculiarities of rf plasma sputtered indium tin oxide films,”Thin Solid Films,vol.515,no.24,pp.8469-8473,2007.
[11] J. Zhou, J.A. Lu, and J. Lu, “Pinning adaptive synchronization of a general complex dynamical network,Automatica,vol. 44, no. 4, pp. 996-1003, 2008.
[12] S. M. Rozati and T. Ganj, “Preparation of In2O3: F thin filmsgrownbyspraypyrolysistechnique,”Renewable Energy,vol.29,no.10,pp.1665-1669,2004.
[13] G. Korotcenkov, M. Nazarov, M.V. Zamoryanskaya and M. Ivanov, “Cathodoluminescence emission study of nanocrystallineindiumoxidefilmsdepositedbyspray pyrolysis,”ThinSolidFilms,vol.515,no.20,pp.80658071,2007.
[14] S. Parthibab, V. Gokulakrishnan, K. Ramamurthi, E. Elangovan, R. Martins, E. Fortunato and R. Ganenan, “High near-infrared transparent molybdenum-doped indium oxide thin films for nanocrystalline silicon solar cell applications,”Solar Energy Materials and SolarCells,vol.93,no.1,pp.92-97,2009.
[15] El Hichou, A. Kachouance, J.L.Bubendor, M. Addou, J. Ebothe, M. Troyon and A. Bougrine, “Effect of substratetemperatureonelectrical,structural,optical and cathodoluminescent properties of In2O3-Sn thin films prepared by spray pyrolysis,”Thin Solid Films,vol.458,no.1,pp.263-268,2004.
[16] M.S. Lee, W.C. Choi, E. Kim, C.K. Kim, S.K. Min, “Characterization of the oxidized indium thin films withthermaloxidation,”ThinSolidFilms,vol.279,no. 1,pp.1-3,1996.
[17] E. Burstein, “Anomalous optical absorption limit in InSb,”PhysicalReview,vol.93,no.3,pp.632,1954.