The influence of magnesium and hydrogen introduction in sputtered zinc oxide thin films

Polycrystalline ZnO thin films doped with magnesium or hydrogen were prepared on Corning 7059 glass substrates by RF magnetron co-sputtering or reactive sputtering. The chemistry, morphology, phase evolution and optical properties of the resulting thin films with various deposition parameters were investigated. X-ray photoemission spectroscopy results show that a linear composition variation for Zn1−xMgxO with amorphous phase can be obtained by varying sputtering power, which results in increasing optical bandgap linearly with x for better light transmission. However, conductivity drops dramatically as soon as magnesium is introduced. On the other hand, hydrogen doping is demonstrated to enhance both crystallinity and conductivity, which was then degraded upon annealing. However, only being exposed to atmosphere would not change conductivity, implying the characteristics of chemical adsorption of hydrogen in the films. The larger grained morphology of the thin films doped with hydrogen was ascribed to both surface fast diffusion and etching. Both dopants can be applied to improve the properties of zinc oxide films.