Growth behaviors and characteristics of low temperature spin-sprayed ZnO and Al-doped ZnO microstructures

Abstract

The influence of growth parameters of the spin-spray technique upon the microstructure and electrical and optical properties of ZnO and Al-doped ZnO microstructures was investigated. This investigation was carried out by varying the pH and concentration of the solutions utilized. With increasing pH from 9 to 12, the ZnO films changed from membrane-like microstructures at a pH of 9 to single crystal ZnO rods with hexagonal ends at the pH of 10, and to polycrystal ZnO needle-like tips with random crystalline orientation at the pH of 12. Varying the concentration of the solution brought about a dramatic change in the crystal growth behavior and crystalline orientation, with the least concentration producing rods more uniform and oriented in the c-axis direction. The optical absorption dependence of the ZnO microstructures was also studied by ultraviolet visible spectrophotometer. This investigation will enable optimized low temperature (textless100 C) fabrication of ZnO films by the spin-spray technique with controllable microstructure and properties based on their processing conditions. Furthermore, the influence of Al doping on the electric property, optical property microstructures of the Al-doped ZnO thin films was examined. Increase in Al concentration from 0 to 2 % further reduced the resistivity of the ZnO films by 3 orders of magnitudes from 3.4 × 10 4 to 14 $Ømega$ cm; while the Hall mobility increases from 1 to 140 cm2/V s at the same time. The optical photoluminescence measurement of Al-doped ZnO thin films in ultra violet (UV) was also demonstrated. © 2013 Springer Science+Business Media New York.