Undoped and aluminum-doped zinc oxide (AZO) thin films are prepared by the sol-gel process. Zinc acetate dihydrate, ethanol, and monoethanolamine are used as precursor, solvent, and stabilizer, respectively. In the case of AZO, aluminum nitrate nonahydrate is added to the precursor solution with an atomic percentage equal to 1 and 2 at.% Al. The multi thin layers are deposited by spin-coating onto glass substrates, and are transformed into ZnO upon annealing at 550 °C. Films display a strong preferential orientation, with high values for the Texture Coefficients (TC) of the (002) direction (TC (002) ≈ 3). The structural, morphological, and optical properties of the thin films as a function of aluminum content have been investigated using X-Ray Diffraction (XRD), Atomic Force Microscopy (AFM), and Scanning Electronic Microscopy (SEM). Waveguiding properties of the thin films have been also studied using m-lines spectroscopy. The results indicate that the films are monomodes at 632.8 nm with optical propagation optical losses estimated around 1.6 decibel per cm (dB/cm).
References
[1]
Ellmer, K.; Klein, A. ZnO and Its Applications. In Transparent Conductive Zinc Oxide—Basics and Applications in Thin Film Solar Cells; Ellmer, K., Klein, A., Rech, B., Eds.; Springer Series in Materials Science; Springer-Verlag: Berlin Heidelberg, Germany, 2008; Volume 104, pp. 1–33.
[2]
Bundesmann, C.; Schmidt-Grund, R.; Schubert, M. Optical Properties of ZnO and Related Compounds. In Transparent Conductive Zinc Oxide—Basics and Applications in Thin Film Solar Cells (Springer Series in Materials Science); Ellmer, K., Klein, A., Rech, B., Eds.; Springer-Verlag: Berlin Heidelberg, Germany, 2008; Volume 104, pp. 79–124.
[3]
Chen, J.L.; Chen, D.; Chen, Z.H. Optimization of the process for preparing Al-doped ZnO thin films by sol-gel method. Sci. China Ser. E Tech. Sci. 2009, 52, 88–94, doi:10.1007/s11431-009-0002-y.
[4]
Tseng, Y.K.; Gao, G.J.; Chien, S.C. Synthesis of c-axis preferred orientation ZnO:Al transparent conductive thin films using a novel solvent method. Thin Solid Films 2010, 518, 6259–6263, doi:10.1016/j.tsf.2010.03.143.
[5]
Lupan, O.; Chow, L.; Shishiyanu, S.; Monaico, E.; Shishiyanu, T.; ？ontea, V.; Roldan Cuenya, B.; Naitabdi, A.; Park, S.; Schulte, A. Nanostructured zinc oxide films synthesized by successive chemical solution deposition for gas sensor applications. Mater. Res. Bull. 2009, 44, 63–69, doi:10.1016/j.materresbull.2008.04.006.
[6]
Lupan, O.; Shishiyanu, S.; Ursaki, V.; Khallaf, H.; Chow, L.; Shishiyanu, T.; Sontea, V.; Monaico, E.; Railean, S. Synthesis of nanostructured Al-doped zinc oxide films on Si for solar cells applications. Sol. Energy. Mater. Sol. Cells 2009, 93, 1417–1422, doi:10.1016/j.solmat.2009.03.012.
[7]
Von Wenckstern, H.; Schmidt, H.; Brandt, M.; Lajn, A.; Pickenhain, R.; Lorenz, M.; Grundmann, M.; Hofmann, D.M.; Polity, A.; Meyer, B.K.; et al. Anionic and cationic substitution in ZnO. Prog. Solid State Chem. 2009, 37, 153–172, doi:10.1016/j.progsolidstchem.2009.11.008.
[8]
？zgür, ü.; Alivov Ya, I.; Liu, C.; Teke, A.; Reshchikov, M.A.; Do？an, S.; Avrutin, V.; Cho, S.J.; Morko？, H. A comprehensive review of ZnO materials and devices. J. Appl. Phys. 2005, 98, 041301:1–041301:103.
Leprince-Wang, Y.; Bouchaib, S.; Brouri, T.; Capo-chichi, M.; Laurent, K.; Leopoldes, J.; Tusseau-Nenez, S.; Lei, L.; Chen, Y. Fabrication of ZnO micro- and nano-structures by electrodeposition using nanoporous and lithography defined templates. Mater. Sci. Eng. B 2010, 170, 107–112, doi:10.1016/j.mseb.2010.02.037.
[11]
Vayssieres, L. Growth of arrayed nanorods and nanowires of ZnO from aqueous solutions. Adv. Mater. 2003, 15, 464–466, doi:10.1002/adma.200390108.
[12]
Chandramohan, R.; Vijayan, T.A.; Arumugam, S.; Ramalingam, H.B.; Dhanasekaran, V.; Sundaram, K.; Mahalingam, T. Effect of heat treatment on microstructural and optical properties of CBD grown Al-doped ZnO thin films. Mater. Sci. Eng. B 2011, 176, 152–156, doi:10.1016/j.mseb.2010.10.017.
[13]
Barankin, M.D.; Gonzalez, E., II; Ladwig, A.M.; Hicks, R.F. Plasma-enhanced chemical vapor deposition of zinc oxide at atmospheric pressure and low temperature. Sol. Energy. Mater. Sol. Cells 2007, 91, 924–930.
[14]
Dai, L.P.; Deng, H.; Zang, J.D.; Mao, F.Y.; Chen, J.J.; Wei, M. The effect of annealing temperature on the properties of ZnO films with preferential nonpolar plane orientation by SSCVD. J. Mater. Sci. 2008, 43, 312–315.
[15]
Triboulet, R.; Perrière, J. Epitaxial growth of ZnO films. Prog. Cryst. Growth Charact. Mater. 2003, 47, 65–138.
[16]
Szyszka, B. Magnetron Sputtering of ZnO Films. In Transparent Conductive Zinc Oxide—Basics and Applications in Thin Film Solar Cells; Ellmer, K., Klein, A., Rech, B., Eds.; Springer Series in Materials Science; Springer-Verlag: Berlin Heidelberg, Germany, 2008; Volume 104, pp. 187–233.
[17]
Hüpkes, J.; Müller, J.; Rech, B. Texture Etched ZnO:Al for Silicon Thin Film Solar Cells. In Transparent Conductive Zinc Oxide—Basics and Applications in Thin Film Solar Cells; Ellmer, K., Klein, A., Rech, B., Eds.; Springer Series in Materials Science; Springer-Verlag: Berlin Heidelberg, Germany, 2008; Volume 104, pp. 359–413.
[18]
Sekar, A.; Kim, S.H.; Umar, A.; Hahn, Y.B. Catalyst-free synthesis of ZnO nanowires on Si by oxidation of Zn powders. J. Cryst. Growth 2005, 277, 471–478, doi:10.1016/j.jcrysgro.2005.02.006.
[19]
Ibanga, E.J.; le Luyer, C.; Mugnier, J. Zinc oxide waveguide produced by thermal oxidation of chemical bath deposited zinc sulphide thin films. Mater. Chem. Phys. 2003, 80, 490–495, doi:10.1016/S0254-0584(02)00552-7.
[20]
Caglar, M.; Ilican, S.; Caglar, Y.; Yakuphanoglu, F. The effects of Al doping on the optical constants of ZnO thin films prepared by spray pyrolysis method. J. Mater. Sci. Mater. Electron. 2008, 19, 704–708, doi:10.1007/s10854-007-9386-2.
[21]
Yen, C.Y.; Jian, S.R.; Chen, G.J.; Lin, C.M.; Lee, H.Y.; Ke, W.C.; Liao, Y.Y.; Yang, P.F.; Wang, C.T.; Lai, Y.S.; et al. Influence of annealing temperature on the structural, optical and mechanical properties of ALD-derived ZnO thin films. Appl. Surf. Sci. 2011, 257, 7900–7905, doi:10.1016/j.apsusc.2011.04.088.
[22]
Ghodsi, F.E.; Absalan, H. Comparative study of ZnO thin films prepared by different sol-gel route. Acta. Phys. Pol. A 2010, 118, 659–664.
[23]
Znaidi, L. Sol-gel-deposited ZnO thin films: A review. Mater. Sci. Eng. B 2010, 174, 18–30, doi:10.1016/j.mseb.2010.07.001.
[24]
Ohyama, M.; Kozuka, H.; Yoko, T.; Sakka, S. Preparation of ZnO films with preferential orientation by sol-gel method. J. Ceram. Soc. Jpn. 1996, 104, 296–300, doi:10.2109/jcersj.104.296.
[25]
Ohyama, M.; Kozuka, H.; Yoko, T. Sol-Gel preparation of ZnO films with extremely preferred orientation along (002) plane from zinc acetate solution. Thin Solid Films 1997, 306, 78–85, doi:10.1016/S0040-6090(97)00231-9.
[26]
Znaidi, L.; Soler Illia, G.J.A.A.; Ben Yahia, S.; Sanchez, C.; Kanaev, A. Oriented ZnO thin films synthesis by sol-gel process for laser application. Thin Solid Films 2003, 428, 257–262, doi:10.1016/S0040-6090(02)01219-1.
[27]
Znaidi, L.; Soler Illia, G.J.A.A.; Le Guennic, R.; Sanchez, C.; Kanaev, A. Elaboration of ZnO thin films with preferential orientation by a soft chemistry route. J. Sol-Gel Sci. 2003, 26, 817–821, doi:10.1023/A:1020795515478.
[28]
Ben Yahia, S.; Znaidi, L.; Kanaev, A.; Petitet, J.P. Raman study of oriented ZnO thin films deposited by sol-gel method. Spectrochim. Acta Part. A 2008, 71, 1234–1238, doi:10.1016/j.saa.2008.03.032.
[29]
Xue, S.W.; Zu, X.T.; Zhou, W.L.; Deng, H.X.; Xiang, X.; Zhang, L.; Deng, H. Effects of post-thermal annealing on the optical constants of ZnO thin film. J. Alloys Compd. 2008, 448, 21–26, doi:10.1016/j.jallcom.2006.10.076.
[30]
Serbet？i, Z.; El-Nasser, H.M.; Yakuphanoglu, F. Photoluminescence and refractive index dispersion properties of ZnO nanofibers grown by sol-gel method. Spectrochim. Acta Part. A 2012, 86, 405–409, doi:10.1016/j.saa.2011.10.058.
[31]
Tang, W.; Cameron, D.C. Aluminum-doped zinc oxide transparent conductors deposited by the sol-gel process. Thin Solid Films 1994, 238, 83–87, doi:10.1016/0040-6090(94)90653-X.
[32]
Ohyama, M. Sol-Gel preparation of transparent and conductive aluminum-doped zinc oxide films with highly preferential crystal orientation. J. Am. Ceram. Soc. 1998, 81, 1622–1632, doi:10.1111/j.1151-2916.1998.tb02524.x.
[33]
Schuler, T.; Aegerter, M.A. Optical, electrical and structural properties of sol-gel ZnO:Al coatings. Thin Solid Films 1999, 351, 125–131, doi:10.1016/S0040-6090(99)00211-4.
[34]
Bandyopadhyay, S.; Paul, G.K.; Roy, R.; Sen, S.K.; Sen, S. Study of structural and electrical properties of grain-boundary modified ZnO films prepared by sol-gel technique. Mater. Chem. Phys. 2002, 74, 83–91, doi:10.1016/S0254-0584(01)00402-3.
[35]
Cheong, K.Y.; Norani Muti, M.; Sutapa, R.R. Physical Investigation on ZnO:Al Thin films derived from non-alkoxide zinc acetate via sol-gel dip coating technique. J. Mater. Sci. Technol. 2003, 11, 78–83.
[36]
Lee, J.H.; Park, B.O. Transparent conducting ZnO:Al, In and Sn thin films deposited by the sol-gel method. Thin Solid Films 2003, 426, 94–99, doi:10.1016/S0040-6090(03)00014-2.
[37]
Xue, S.W.; Zu, X.T.; Zheng, W.G.; Deng, H.X.; Xiang, X. Effects of Al doping concentration on optical parameters of ZnO:Al thin films by sol-gel technique. Physica B 2006, 381, 209–213, doi:10.1016/j.physb.2006.01.342.
[38]
Lai, C.M.; Lin, K.M.; Rosmaidah, S. Effect of annealing temperature on the quality of Al-doped ZnO thin films prepared by sol-gel method. J. Sol.-Gel Sci. Technol. 2011, doi:10.1007/s10971–011–2621–6.
[39]
Khan, F.; Singh, V.S.N.; Husain, M.; Singh, P.K. Sol-gel derived hydrogen annealed ZnO:Al films for silicon solar cell application. Sol. Energy. Mater. Sol. Cells 2012, 100, 57–60, doi:10.1016/j.solmat.2011.04.024.
Lv, J.; Huang, K.; Chen, X.; Zhu, J.; Cao, C.; Song, X.; Sun, Z. Optical constants of Na-doped ZnO thin films by sol-gel method. Opt. Commun. 2011, 284, 2905–2908.
[42]
Caglar, M.; Yakuphanoglu, F. Structural and optical properties of copper doped ZnO films derived by sol-gel. Appl. Surf. Sci. 2012, 258, 3039–3044.
[43]
Tsay, C.Y.; Cheng, H.C.; Tung, Y.T.; Tuan, W.H.; Lin, C.K. Effect of Sn-doped on microstructural and optical properties of ZnO thin films deposited by sol-gel method. Thin Solid Films 2008, 517, 1032–1036, doi:10.1016/j.tsf.2008.06.030.
[44]
Shelke, V.; Sonawane, B.K.; Bhole, M.P.; Patil, D.S. Electrical and optical properties of transparent conducting tin doped ZnO thin films. J. Mater. Sci. 2012, 23, 451–456.
[45]
Liu, C.; Yun, F.; Morko？, H. Ferromagnetism of ZnO and GaN: A review. J. Mater. Sci. Mater. Electron. 2005, 16, 555–597.
[46]
Mueller, J.; Mahnke, M.; Schoer, G.; Wiechmann, S. Inorganic Materials Integrated Optics. AIP Conf. Proc. 2004, 709, 268–289, doi:10.1063/1.1764024.
[47]
Tien, P.K.; Ulrich, R. Theory of prism-film coupler and thin-film light guides. J. Opt. Soc. Am. 1970, 60, 1325–1337, doi:10.1364/JOSA.60.001325.
[48]
Chen, J.; Chen, D.; He, J.; Zhang, S.; Chen, Z. The microstructure, optical, and electrical properties of sol-gel-derived Sc-doped and Al-Sc co-doped ZnO thin films. Appl. Surf. Sci. 2009, 255, 9413–9419, doi:10.1016/j.apsusc.2009.07.044.
[49]
Fityk. Available online: http://fityk.nieto.pl/ (accessed on 1 June 2013).
[50]
Barret, C.S.; Massalski, T.B. Structure of Metals: Crystallographic Methods, Principles and Data; Pergamon Press: Oxford, UK, 1980; p. 204.
[51]
Williamson, G.K.; Hall, W.H. X-ray line broadening from filed aluminium and wolfram. Acta Metall. 1953, 1, 22–31, doi:10.1016/0001-6160(53)90006-6.
[52]
Burton, A.W.; Ong, K.; Rea, T.; Chan, I.Y. On the estimation of average crystallite size of zeolites from the Scherrer equation: A critical evaluation of its application to zeolites with one-dimensional pore systems. Microporous. Mesoporous. Mater. 2009, 117, 75–90, doi:10.1016/j.micromeso.2008.06.010.
[53]
Kersten, R.Th. Numerical solution of the mode-equation of planar dielectric waveguides to determine their refractive index and thickness by means of a prism-film coupler. Opt. Commun. 1973, 9, 427–431, doi:10.1016/0030-4018(73)90288-5.
[54]
Strohkendl, F.P.; Fluck, D.; Günter, P.; Irmscher, R.; Buchal, Ch. Nonleaky optical waveguides in KNbO3 by ultralow dose MeV He ion implantation. Appl. Phys. Lett. 1991, 59, 3354–3356.
[55]
Weber, H.P.; Dunn, F.A.; Leibolt, W.N. Loss measurements in thin-film optical waveguides. Appl. Opt. 1973, 12, 755–757, doi:10.1364/AO.12.000755.
[56]
Boudrioua, A.; Loulergue, J.C. New approach for loss measurements in optical planar waveguides. Opt. Commun. 1997, 137, 37–40, doi:10.1016/S0030-4018(96)00764-X.
