Structural and Physical Characterisation of Zinc Oxide Thin Films Prepared from Zinc Acetate via the Sol-gel Method
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1035-L05-09
Structural and Physical Characterisation of Zinc Oxide Thin Films Prepared from Zinc Acetate via the Sol-gel Method Shane O'Brien1, Lee H.K. Koh1,2, Mehmet Copuroglu1,2, and Gabriel M. Crean1,2 1 Tyndall National Institute, University College Cork, Lee Maltings, Prospect Row, Cork, Ireland 2 Department of Microelectronic Engineering, University College Cork, Cork, Ireland ABSTRACT The influence of zinc acetate concentration in the range 0.3 – 1.3M and annealing temperature in the range 450 – 550oC on the microstructure of zinc oxide films prepared by the sol-gel method was investigated. Zinc acetate concentration of the sol-gel deposited was found to be the major influence on the microstructure and in particular c-axis or (002) preferred orientation of the resulting film, due to its impact on film thickness, for a single sol-gel deposition employing fixed deposition conditions. Preferentially (002) orientated films were obtained from 0.3M zinc acetate sol-gels. However, an increase in zinc acetate concentration resulted in an increase in film thickness and a loss of preferential (002) orientation. It was found that thick preferentially (002) oriented films could be produced by using multiple depositions of a 0.7M zinc acetate sol-gel using higher drying temperatures. INTRODUCTION ZnO is a wide direct band-gap oxide semiconductor that has significant potential application in electronic, optoelectronic and information technology device platforms due to its electrical and optical properties [1]. Several thin-film deposition techniques have been demonstrated to produce pure ZnO films, including sputtering [2], molecular beam epitaxy [3], metal-organic chemical vapour deposition [4], pulsed laser deposition [5], spray pyrolysis [6] and the sol-gel process [7]. The sol-gel method has several distinct potential advantages over its counterparts, due to its lower crystallization temperature, ability to tune microstructure via solgel chemistry, conformal deposition ability, compositional control and large surface area coating capability. Previous studies have shown that thick ZnO films can be prepared from a single deposition of sol-gel, but that preferential c-axis orientation can only be obtained under certain conditions [8,9]. In this study, a detailed investigation of the influence of the zinc acetate concentration of the deposited sol-gel and process annealing temperature on the microstructural, physical, electronic and optical properties of ZnO sol-gel thin film processes is presented, in order to identify the process conditions which result in c-axis orientated thick films produced from both single and multiple sol-gel depositions. The deposition process and annealing temperature are the two primary factors which influence the microstructure and resultant properties of ZnO films. In general, studies on sol-gel derived ZnO films involve investigation of the influence of annealing temperature on sol-gel films prepared from a single zinc acetate concentration, or else the investigation of the effect of zinc a
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