Grain Size Effect on the Electrical Conduction Behavior of Nanocrystalline ZnO Films
Yi-Ting Pan (潘逸庭)1*, Yan-Bo Lin (林燕柏)1, San-Lin Young (楊尚霖)1, Hone-Zern Chen (陳宏仁)1, Ming-Cheng Kao (高銘政)1, Po-Yen Chen (陳柏諺)2, Wun-Hong Jhang (張文鴻)1, Daisuke Yoshikawa (吉川大佑)1
1Department of Electronic Engineering, Hsiuping University of Science and Technology, Taichung, Taiwan
2Department of Electrical Engineering, Hsiuping University of Science and Technology, Taichung, Taiwan
* presenting author:潘逸庭,
Nanocrystalline ZnO films were deposited on glass substrates and annealed at various temperatures for the investigation of electrical conduction behavior. The field emission scanning electron microscopy measurements show the grain size of the films increases with increasing annealing temperature. Structural characterization by X-ray diffraction patterns of all films shows the same wurtzite hexagonal structure with preferential orientation along c-axis. In the photoluminescence spectra, decrease of visible light emission and increase of UV light emission with increasing annealing temperature reveal the enhancement of crystallization. For all nanocrystalline ZnO films, semiconductor transport characteristic with negative temperature coefficient of resistivity is observed from the temperature-dependent resistivity. As temperature increases, the dominate carrier transport behavior below 300 K is gradually transferred from the thermal activation conduction to the Mott variable-range hopping conduction with decreasing temperature. Decrease of resistivity of the films with increasing annealing temperature is consistent with the increase of grain size and the enhancement of crystallization. The results reveal that the microstructure and the corresponding carrier transport behavior of the nanocrystalline ZnO films are affected by the annealing treatment.

Keywords: Nanocrystalline, ZnO, Grain, Photoluminescence, Carrier transport