Initial vacuum effects on the properties of sputter deposited Ga-doped ZnO thin films

Initial vacuum effects on the structural, electrical, optical properties of Ga-doped ZnO (GZO) films were investigated systematically. GZO thin films were prepared on glass substrates by RF magnetron sputtering at room temperature. With decreasing the initial vacuum, the electrical conductivity is enhanced due to an increase in the carrier concentration and mobility. Low initial vacuum resulted in the improvement in crystallinity, the increase of oxygen-vacancy and the decrease of the surface bonding, because of minimization the effect of residual gases in the process chamber, leading to an increase in the carrier concentration and mobility together. Especially, the behavior of oxygen-vacancy and surface bonding evidently are promoted at below 2 × 10−6 Torr. The average transmittance of all the thin films deposited was above 85% in the visible spectrum. The figure of merit for the GZO thin film improved, as initial vacuum decreased. The control of initial vacuum plays an important role in the subsequent properties of sputtered GZO thin films.