The use of thin-film semiconducters deposited on a low cost substrate has been regarded as a promising approach toward the mass production of low-cost photovoltaic devices. Zinc oxide (ZnO) is wide band gap semiconductor (-3.37 eV at room temperature) with various applications. Recently, it was considered to be a new photo-electric material in shortwave length as GaN. In1996, stimulated UV emission of ZnO at room temperature was reported, and ZnO as a UV laser material attracted people's attention immediate...