ABSTRACT Highly oriented and transparent ZnO thin films have been fabricated on ultrasonically cleaned quartz substrates by the sol-gel technique. X-ray diffraction, UV-VIS, FTIR, photoluminescence and SEM are used to characterize ZnO thin films. X-ray diffraction study show that all the films prepared in this work have hexagonal wurtzite structure, with lattice constants a = b = 3.260 Å, c = 5.214 Å. The optical band gap energy of the thin films is found to be direct allowed transition ~3.24 eV. The FTIR spectrum of the film has the characteristics ZnO absorption band at 482 cm?1. The photoluminescence spectrum of the samples has an UV emission peak centred at 383 nm with broad band visible emission centred in the range of 500 - 600 nm.
Cite this paper
nullZ. Khan, M. Khan, M. Zulfequar and M. Shahid Khan, "Optical and Structural Properties of ZnO Thin Films Fabricated by Sol-Gel Method," Materials Sciences and Applications, Vol. 2 No. 5, 2011, pp. 340-345. doi: 10.4236/msa.2011.25044.
 Z. K. Tang, G. K. L. Wong, P. Yu, M. Kawasaki, A. Ohtomo, H. Koinuma and Y. Segawa, “Room-Temperature Ultraviolet Laser Emission from Self-Assembled ZnO Microcrystallite Thin Films,” Applied Physics Letters, Vol. 72, No. 25, June 1998, pp. 3270-3272.
 Y. B. Li, Y. Bando and D. Golberg, “ZnO Nanoneedles with Tip Surface Perturbations: Excellent Field Emitters,” Applied Physics Letters, Vol. 84, No. 18, May 2004, pp. 3603-3605. doi:10.1063/1.1738174
 A. Tsuka-zaki, A. Ohtomo, T. Onuma, M. Ohtani, T. Mankino, M. Su-miya, K. Ohtani, S. F. Chichibu, S. Fuke, Y. Segawa, H. Koinuma and M. Kawasaki, “Repeated Temperature Modula-tion Epitaxy for p-Type Doping and Light-Emitting Diode Based on ZnO,” Nature Materials, Vol. 4, No. 1, January 2005, pp. 42-46.
 S. H. Lee, S. S. Lee, J. J. Choi, J. U. Jeon and K. Ro, “Fabrication of a ZnO Piezoelectric Micro Cantilever with a High-Aspect-Ratio Nano Tip,” Microsystem Technologies, Vol. 11, No. 6, June 2005, pp. 416-423.
 I. Salaoru, P. A. Buffat, D. Laub, A. Amariei, N. Apetroaei and M. Rusu, “Preparation and Structural Characterization of Thin-Film CdTe/CdS Hetero-junctions,” Journal of Optoelectronics and Advanced Materials, Vol. 8, No. 3, June 2006, pp. 936-940.
 J. Q. Xu, Q. Y. Pan, Y. A. Shun and Z. Z. Tian, “Grain Size Control and Gas Sensing Properties of ZnO Gas Sensor,” Sensors and Actuators B: Chemical, Vol. 66, No. 1-3, July 2007, pp. 277-279.
 K. J. Chen, F. Y. Hung, S. J. Chang and S. J. Young, “Optoelc-tronic Characteristics of UV Photodetector Based on ZnO Nanowire Thin Films,” Journal of Alloys and Compounds, Vol. 479, No. 1-2, June 2009, pp. 674- 677. doi:10.1016/j.jallcom.2009.01.026
 S. Majumdar and P. Bnerji, “Hopping Conduction in Nitrogen Doped ZnO in the Temperature Range 10 - 300 K,” Journal of Applied Physics, Vol. 107, No. 6, May 2010, pp. 063702-063702-4. doi:10.1063/1.3353862
 P. Pushpharajah, S. Radhakrishna and A. K. Arof, “Transparent Conducting Lithium-Doped Nickel Oxide Thin Films by Spray Pyrolysis Technique,” Journal of Materials Science, Vol. 32, No. 11, June 1997, pp. 3001- 3006. doi:10.1023/A:1018657424566
 J. D. Ye, S. L. Gu, S. M. Zhu, T. Chen, L. Q. Hu, F. Qin, R. Zhang, Y. Shi and Y. D. Zheng, “The Growth and Annealing of Single Crystalline ZnO Films by Low-Pressure MOCVD,” Journal of Crystal Growth, Vol. 243, No. 1, May 2002, pp. 151-160.
 J. B. Lee, S. H. Kwak and H. J. Kim, “Effects of Surface Roughness of Sub-strates on the c-Axis Preferred Orientation of ZnO Films De-posited by r.f. Magnetron Sputtering,” Thin Solid Films, Vol. 423, No. 2, January 2003, pp. 262-266. doi:10.1016/S0040-6090(02)00977-X
 L. Znaidi, G. J. A. A. S. Illia, S. Benyahia, C. Sanchez and A. V. Kanaev, “Ori-ented ZnO Thin Films Synthesis by Sol-Gel Process for Laser Application,” Thin Solid Films, Vol. 428, No. 1-2, March 2003, pp. 257-262.
 H. Bahadur, A. K. Srivastava, D. Haranath, H. Chander, A. Basu, S. B. Samanta, K. N. Sood, R. Kishore, R. K. Sharma, Rashmi, V. Bhatt, P. Pal and S. Chandra, “Nano- Structured ZnO Films by Sol-Gel Process,” Indian Journal of Pure & Applied Physics, Vol. 45, April 2007, pp. 395-399.
 H. X. Li, J. Y. Wang, H. Liu, H. J. Zhang and X. Li, “Zinc Oxide Films Prepared by Sol-Gel Method,” Journal of Crystal Growth, Vol. 275, No. 1-2, Febru-ary 2005, pp. e943-e946. doi:10.1016/j.jcrysgro.2004.11.098
 Z. R. Khan, M. Zulfequar and M. S. Khan, “Optical and Structural Properties of Thermally Evaporated Cadmium Sulphide Thin Films on Sili-con (100) Wafers,” Materials Science and Engineering: B, Vol. 174, No. 1-3, October 2010, pp. 145-149. doi:10.1016/j.mseb.2010.03.006
 M. Caglar, S. Ilican and Y. Caglar, “Influence of Dopant Concentration on the Optical Properties of ZnO: In films by Sol-Gel Method,” Thin Solid Films, Vol. 517, No. 17, July 2009, pp. 5023-5028. doi:10.1016/j.tsf.2009.03.037
 Z. Yang, Z. Z. Ye, Z. Xu and B. H. Zhao, “Effect of the Morphology on the Optical Properties of ZnO Nanostructured,” Physica E: Low-Dimensional Systems and Nanostructures, Vol. 42, No. 2, December 2009, pp. 116- 119. doi:10.1016/j.physe.2009.09.010
 T. Ivanova, A. Hari-zanova, T. Koutzarova and B. Vertruyen, “Study of ZnO Sol-Gel Films: Effect of Annealing,” Materials Letters, Vol. 64, No. 10, October 2010, pp. 1147-1149. doi:10.1016/j.matlet.2010.02.033
 Y. J. Kwon, K. H. Kim, C. S. Lim and K. B. Shim, “Chara- terization of ZnO Nanopow-ders Synthesized by the Polymerized Complex Method via an Organochemical Route,” Journal of Ceramic Processing Re-search, Vol. 3, June 2002, pp. 146-149.
 M. Vafaee and M. S. Ghamsari, “Preparation and Characterization of ZnO Nanoparticles by a Novel Sol-Gel Route,” Materials Letters, Vol. 61, No. 14-15, June 2007, pp. 3265-3268. doi:10.1016/j.matlet.2006.11.089
 Y.-S. Kim, W.-P. Tai, S.-J. Shu, “Effect of Preheating Temperature on Structural and Optical Properties of ZnO Thin Films by Sol-Gel Process,” Thin Solid Films, Vol. 491, No. 1-2, November 2005, pp. 153-160.