We have investigated the effect of ambient gases on the characteristics of Mo-doped ZnO (MZO) thin films. The MZO thinfilms are deposited by radio frequency (RF) magnetron sputtering under different ambient gases (Ar, Ar+O2, and Ar+H2) at100 oC. To investigate the influences of the ambient gases, the flow rate of oxygen and hydrogen in argon was varied from 0.1sccm to 0.5 sccm. The MZO thin films were preferentially oriented to the (002) direction, regardless of the ambient gases used. The electrical resistivity of the MZO thin films increased with increasing O2 flow rates, whereas the electrical resistivitydecreased sharply under an Ar+H2 atmosphere and was nearly the same, regardless of the H2 flow rate used. The change ofelectrical resistivity with changes in the ambient gas composition was mainly interpreted in terms of the charge carrierconcentration rather than the charge carrier mobility. All the films showed an average transmittance of over 80% in the visiblerange. The optical band gap of the MZO films increased with increasing H2 flow rates, whereas the optical band gap of theMZO films deposited under an O2 atmosphere slightly decreased with increasing O2 flow rates.

Keywords: MZO thin film, ambient gas, RF sputtering, Optical band gap