Resistivity Stability of Ga Doped ZnO Thin Films with Heat Treatment in Air and Oxygen Atmospheres

T. Prasada Rao, M. C. Santhosh Kumar

Advanced Materials Laboratory, Department of Physics, National Institute of Technology, Tiruchirappalli, India.
Advanced Materials Laboratory, Department of Physics, National Institute of Technology, Tiruchirappalli, India..

DOI: 10.4236/jcpt.2012.22010                

Abstract

The effect of annealing in air and oxygen on structural, electrical and optical properties of gallium doped ZnO thin films was investigated. The X-ray diffraction patterns showed that the films were highly preferentially oriented along (002) plane. After the heat treatment in air and oxygen environments, the intensity of (002) peak was apparently improved. It was found that heat treatment in air atmospheres lead to increase in surface roughness of the film. The GZO films annealed in oxygen at 673 K exhibited low resistivity of 4.21 × 10^–3 Ω.cm, while the resistivity of film annealed in air showed a slightly higher value of 7.14 × 10^–3 Ω.cm. In addition to this, all films have good optical transmittance about 80% in the visible region. It is found from the photoluminescence studies that the broad visible emissions in GZO films originated from the intrinsic shallow traps (V_Zn) and deep level vacancies (Z_Zi, O_Zn and V_o)

Keywords

GZO Thin Films; Spray Pyrolysis; XPS; Optical Properties; Electrical Properties

Conflicts of Interest

The authors declare no conflicts of interest.

References

[1]	R. F. Service, “Will UV Lasers Beat the Blues?” Science, Vol. 276, No. 5314, 1997, p. 895. doi:10.1126/science.276.5314.895
[2]	D. P. Norton, Y. W. Heo, M. P. Ivill, K. Ip, S. J. Pearton, M. F. Chisholm and T. Steiner, “ZnO: Growth, Doping & Processing,” Materials Today, Vol. 7, No. 6, 2004, pp. 34-40. doi:10.1016/S1369-7021(04)00287-1
[3]	S. J. Pearton, D. P. Norton, K. Ip, Y. W. Heo and T. Steiner, “Recent Progress in Processing and Properties of ZnO,” Progress in Materials Science, Vol. 50, No. 3, 2005, pp. 293-340. doi:10.1016/j.pmatsci.2004.04.001
[4]	B. Lin, Z. Fu and Y. Jia, “Green Luminescent Center in Undoped Zinc Oxide Films Deposited on Silicon Sub-strates,” Applied Physics Letters, Vol. 79, No. 7, 2001, pp. 943-945. doi:10.1063/1.1394173
[5]	J. Zhong, S. Muthukumar, Y. Chen, Y. Lu, H. M. Ng, W. Jiang and E. L. Garfunkel, “Ga-Doped ZnO Single-Crystal Nanotips Grown on Fused Silica by Metalorganic Chemical Vapor Deposition,” Applied Physics Letters, Vol. 83, No. 16, 2003, pp. 3401-3403. doi:10.1063/1.1621729
[6]	B. E. Sernelius, K. F. Berggren, Z. C. Jin, I. Hamberg and C. G. Granqvist, “Band-Gap Tailoring of ZnO by Means of Heavy Al Doping,” Physical Review B, Vol. 37, No. 17, 1988, pp. 10244-10248. doi:10.1103/PhysRevB.37.10244
[7]	H. Fujiwara and M. Kondo, “Effects of Carrier Concen- tration on the Dielectric Function of ZnO:Ga and In2O3: Sn Studied by Spectroscopic Ellipsometry: Analysis of Free-Carrier and Band-Edge Absorption,” Physical Review B, Vol. 71, No. 7, 2005, pp. 1-10. doi:10.1103/PhysRevB.71.075109
[8]	V. Bhosle, A. Tiwari and J. Narayan, “Metallic Conductivity and Metal-Semiconductor Transition in Ga-Doped ZnO,” Applied Physics Letters, Vol. 88, No. 3, 2006, Article No. 032106. doi:10.1063/1.2165281
[9]	J. De Merchant and M. Cocivera, “Preparation and Doping of Zinc Oxide Using Spray Pyrolysis,” Chemistry of Materials, Vol. 7, No. 9, 1995, pp. 1742-1749. doi:10.1021/cm00057a026
[10]	P. Nunes, E. Fortunato, P. Tonello, F. B. Fernandes, P. Vilarinho and R. Martins, “Effect of Different Dopant Elements on the Properties of ZnO Thin Films,” Vacuum, Vol. 64, No. 3-4, 2002, pp. 281-285. doi:10.1016/S0042-207X(01)00322-0
[11]	S. B. Majumder, M. Jain, P. S. Dobal and R. S. Katiyar, “Investigations on Solution Derived Aluminium Doped Zinc Oxide Thin Films,” Materials Science and Engineering: B, Vol. 103, No. 1, 2003, pp. 16-25. doi:10.1016/S0921-5107(03)00128-4
[12]	H. Kim, C. M. Gilmore, J. S. Horwitz, A. Piqué, H. Murata, G. P. Kushto, R. Schlaf, Z. H. Kafafi and D. B. Chrisey, “Transparent Conducting Aluminum-Doped Zinc Oxide Thin Films for Organic Light-Emitting Devices,” Applied Physics Letters, Vol. 76, No. 3, 2000, pp. 259- 261. doi:10.1063/1.125740
[13]	K. Yim, H. W. Kim and C. Lee, “Effects of Annealing on Structure, Resistivity and Transmittance of Ga Doped ZnO Films,” Materials Science and Technology, Vol. 23, No. 1, 2007, pp. 108-112. doi:10.1179/174328407X158514
[14]	O. Nakagawara, Y. Kishimoto, H. Seto, Y. Koshido, Y. Yoshino and T. Makino, “Moisture-Resistant ZnO Transparent Conductive Films with Ga Heavy Doping,” Applied Physics Letters, Vol. 89, No. 9, 2006, Article No. 091904. doi:10.1063/1.2337542
[15]	H. J. Bolink, E. Coronado, D. Repetto and M. Sessolo, “Air Stable Hybrid Organic-Inorganic Light Emitting Diodes Using ZnO as the Cathode,” Applied Physics Letters, Vol. 91, No. 22, 2007, pp. 223501-223503. doi:10.1063/1.2809387
[16]	D. H. Zhang, T. L. Yang, J. Ma, Q. P. Wang, R. W. Gao and H. L. Ma, “Preparation of Transparent Conducting ZnO:Al Films on Polymer Substrates by r. f. Magnetron Sputtering,” Applied Surface Science, Vol. 158, No. 1-2, 2000, pp. 43-48. doi:10.1016/S0169-4332(99)00591-7
[17]	Z. B. Fang, Z. J. Yana, Y. S. Tan, X. Q. Liu and Y. Y. Wang, “Influence of Post-Annealing Treatment on the Struc- ture Properties of ZnO Films,” Applied Surface Science, Vol. 241, No. 3-4, 2005, pp. 303-308. doi:10.1016/j.apsusc.2004.07.056
[18]	P. Sagar, P. K. Shishodia, R. M. Mehra, H. Okada, A. Wakahara and A. Yoshida, “Photoluminescence and Absorption in Sol-Gel-Derived Zno Films,” Journal of Luminescence, Vol. 126, No. 2, 2007, pp. 800-806.
[19]	S. Y. Chu, W. Water and J. T. Liaw, “Influence of Post-deposition Annealing on the Properties of ZnO Films Prepared by RF Magnetron Sputtering,” Journal of the European Ceramic Society, Vol. 23, No. 10, 2003, pp. 1593- 1598. doi:10.1016/S0955-2219(02)00404-1
[20]	V. Gupta and A. Mansingh, “Influence of Postdeposition Annealing on the Structural and Optical Properties of Sputtered Zinc Oxide Film,” Journal of Applied Physics, Vol. 80, No. 2, 1996, pp. 1063-1072. doi:10.1063/1.362842
[21]	J. F. Chang, W. C. Lin and M. H. Hon, “Effects of Post- Annealing on the Structure and Properties of Al-Doped Zinc Oxide Films,” Applied Surface Science, Vol. 183, No. 1-2, 2001, pp. 18-25. doi:10.1016/S0169-4332(01)00541-4
[22]	M. N. Islam, T. B. Ghosh, K. L. Chopra and H. N. Acharya, “XPS and X-Ray Diffraction Studies of Aluminum-Doped Zinc Oxide Transparent Conducting Films,” Thin Solid Films, Vol. 280, No. 1-2, 1996, pp. 20-25. doi:10.1016/0040-6090(95)08239-5
[23]	G. E. Hammer and R. M. Shermenski, “The Oxidation of Zinc in Air Studied by XPS and AES,” Journal of Vac- uum Science & Technology A, Vol. 1, No. 2, 1983, pp. 1026-1028. doi:10.1116/1.572331
[24]	J. F. Moulder, W. F. Stickel, P. E. Sobol and K. D. Bomben, “Handbook of X-Ray Photoelectron Spectroscopy: A Reference Book of Standard Spectra for Identification and Interpretation of XPS Data,” Physical Electronics, Eden Prairie, 1995.
[25]	X. Q. Wei, B. Y. Man, M. Liu, C. S. Xue, H. Z. Zhuang and C. Yang, “Blue Luminescent Centers and Micro-structural Evaluation by XPS and Raman in ZnO Thin Films Annealed in Vacuum, N2 and O2,” Physica B: Condensed Matter, Vol. 388, No. 1-2, 2007, pp. 145-152. doi:10.1016/j.physb.2006.05.346
[26]	Y. Takahashi, M. Ka-namori, A. Kondoh, H. Minoura and Y. Ohya, “Photoconductivity of Ultrathin Zinc Oxide Films,” Japanese Journal of Applied Physics, Vol. 33, No. 12, 1994, pp. 6611-6615. doi:10.1143/JJAP.33.6611
[27]	G.-J. Fang, D.-J., Li and B.-L. Yao, “Influence of Post-Deposition Annealing on the Properties of Transparent Conductive Nanocrystalline ZAO Thin Films Prepared by RF Magnetron Sputtering with Highly Conductive Ceramic Target,” Thin Solid Films, Vol. 418, No. 2, 2002, pp. 156-162. doi:10.1016/S0040-6090(02)00733-2
[28]	B. D. Ahn, S. H. Oh, C. H. Lee, G. H. Kim, H. J. Kim and S. Y. Lee, “Influence of Thermal Annealing Ambient on Ga-Doped ZnO Thin Films,” Journal of Crystal Growth, Vol. 309, No. 2, 2007, pp. 128-133. doi:10.1016/j.jcrysgro.2007.09.014
[29]	Y. Takahashi, M. Ka-nanmori, A. Kondoh, H. Minoura and Y. Ohya, “Photoconductivity of Ultrathin Zinc Oxide Films,” Japanese Journal of Applied Physics, Vol. 33, No. 12, 1994, pp. 6611-6615. doi:10.1143/JJAP.33.6611
[30]	Q. B. Ma, Z. Z. Ye, H. P. He, L. P. Zhu, J. Y. Huang, Y. Z. Zhang and B. H. Zhao, “Influence of Annealing Temperature on the Properties of Transparent Conductive and Near-Infrared Reflective ZnO:Ga Films,” Scripta Materialia, Vol. 58, No. 1, 2008, pp. 21-24. doi:10.1016/j.scriptamat.2007.09.009
[31]	K. L. Chopra, “Thin Film Phenomena,” McGraw-Hill, New York, 1969.
[32]	D. Jiles, “Introduction to the Electronic Properties of Materials,” Chapman and Hall, New York, 1994. doi:10.1007/978-1-4615-2582-0
[33]	T. Minami, H. Nanto and S. Takata, “Optical Properties of Aluminum Doped Zinc Oxide Thin Films Prepared by RF Magnetron Sputtering,” Japanese Journal of Applied Physics, Vol. 24, Part 2, 1985, pp. L605-L607. doi:10.1143/JJAP.24.L605
[34]	E. Burstein, “Anomalous Opti-cal Absorption Limit in InSb,” Physical Review, Vol. 93, No. 3, 1954, pp. 632-633. doi:10.1103/PhysRev.93.632
[35]	T. S. Moss, “The Interpre-tation of the Properties of Indium Antimonide,” Proceedings of the Physical Society. Section B, Vol. 67, No. 10, 1954, pp. 775-782. doi:10.1088/0370-1301/67/10/306
[36]	K. Bouzid, A. Djelloul, N. Bouzid and J. Bougdira, “Elec- trical Resistivity and Photo-luminescence of Zinc Oxide Films Prepared by Ultrasonic Spray Pyrolysis,” Physica Status Solidi (A), Vol. 206, No. 1, 2009, pp. 106-115. doi:10.1002/pssa.200824403
[37]	D. C. Reynolds, D. C. Look, B. Jogai, J. E. Van Nostrand, R. Jones and J. Jenny, “Source of the Yellow Lumines-cence Band in GaN Grown by Gas-Source Molecular Beam Epitaxy and the Green Luminescence Band in Sin- gle Crystal ZnO,” Solid State Communications, Vol. 106, No. 10, 1998, pp. 701-704. doi:10.1016/S0038-1098(98)00048-9
[38]	P. K. Nayak, J. Yang, J. Kim, S. Chung, J. Jeong, C. Lee and Y. Hong, Journal of Physics D: Applied Physics, Vol. 42, No. 3, 2008, Article No. 035102.
[39]	J. A. Sans, A. Segura, J. F. Sanchez-Royo, V. Barber, M. A. Hernandez-Fenollosa and B. Marib, “Correlation be- tween Optical and Transport Properties of Ga-Doped ZnO Thin Films Prepared by Pulsed Laser Deposition,” Su- perlattices and Microstructures, Vol. 39, No. 1-4, 2006, pp. 282-290. doi:10.1016/j.spmi.2005.08.050
[40]	L.-P. Zhu, J.-S. Li, Z.-Z. Ye, H.-P. He, X.-J. Chen and B.-H. Zhao, “Photoluminescence of Ga-Doped ZnO Na- norods Prepared by Chemical Vapor Deposition,” Optical Materials, Vol. 31, No. 2, 2008, pp. 237-240. doi:10.1016/j.optmat.2008.03.015
[41]	B. J. Jin, S. Im and S.Y. Lee, “Violet and UV Lumines-cence Emitted from ZnO Thin Films Grown on Sapphire by Pulsed Laser Deposition,” Thin Solid Films, Vol. 366, No. 1-2, 2000, pp. 107-110. doi:10.1016/S0040-6090(00)00746-X
[42]	K. Vanheusden, W. L. Warren, C. H. Seager, D. R. Tallant, J. A. Voigt and B. E. Gnade, “Mechanisms Behind Green Photoluminescence in ZnO Phosphor Powders,” Journal of Applied Physics, Vol. 79, No. 10, 1996, pp. 7983-7970. doi:10.1063/1.362349
[43]	D. C. Look and B. Claflin, “P-Type Doping and Devices Based on ZnO,” Physica Status Solidi (B), Vol. 241, No. 3, 2004, pp. 624-630. doi:10.1002/pssb.200304271
[44]	H. J. Egelhaaf and D. Oelkrug, “Luminescence and Non- radiative Deactivation of Excited States Involving Oxygen Defect Centers in Polycrys-talline ZnO,” Journal of Crystal Growth, Vol. 161, No. 1-4, 1996, pp. 190-194. doi:10.1016/0022-0248(95)00634-6
[45]	P. M. R. Kumar, C. S. Kartha, K. P. Vijayakumar, F. Singh, D. K. Avasthi, T. Abe, Y. Kashiwaba, G. S. Ok- ram, M. Kumar and S. Kumar, “Modifi-cations of ZnO Thin Films under Dense Electronic Excitation,” Journal of Applied Physics, Vol. 97, No. 1, 2005, Article No. 013509. doi:10.1063/1.1823574
[46]	Y. H. Tong, Y. C. Liu, S. X. Lu, L. Dong, S. J. Chen and Z. Y. Xiao, “The Optical Properties of ZnO Nanoparticles Capped with Polyvinyl Butyral,” Journal of Sol-Gel Science and Technology, Vol. 30, No. 3, 2004, pp. 157-161. doi:10.1023/B:JSST.0000039500.48283.5a
[47]	X. Q. Wei, B. Y. Man, M. Liu, C. S. Xue, H. Z. Zhuang and C. Yang, “Blue Luminescent Centers and Micro-structural Evaluation by XPS and Raman in ZnO Thin Films Annealed in Vacuum, N2 and O2,” Physica B: Condensed Matter, Vol. 388, No. 1-2, 2007, pp. 145-152. doi:10.1016/j.physb.2006.05.346
[48]	K. Prabakar, C. Kim and C. Lee, “UV, Violet and Blue-Green Luminescence from RF Sputter Deposited ZnO:Al Thin Films,” Crystal Research and Technology, Vol. 40, No. 12, 2005, pp. 1150-1154. doi:10.1002/crat.200410508
[49]	D. Wang. H. W. Seo, C. C. Tin, M. J. Bozack, J. R. Williams, M. Park, N. Sathitsuksanoh, A.-J. Cheng and Y. H. Tzeng, “Effects of Postgrowth Annealing Treatment on the Photoluminescence of Zinc Oxide Nanorods,” Journal of Applied Physics, Vol. 99, No. 11, 2006, pp. 113509- 113513. doi:10.1063/1.2200593
[50]	S. A. Studenikin and M. Cocivera, “Time-Resolved Lu-minescence and Photo-conductivity of Polycrystalline ZnO Films,” Journal of Applied Physics, Vol. 91, No. 8, 2002, pp. 5060-5065. doi:10.1063/1.1461890