Behaviors of carrier concentrations and mobilities in indium–tin oxide thin films by DC magnetron sputtering at various oxygen flow rates

The behaviors of the carrier concentrations and mobilities of indium–tin oxide (ITO) thin films, prepared by DC magnetron sputtering at the various oxygen flow rates, were investigated by means of the Hall technique. The relationship between the carrier concentrations and mobilities along the oxygen flow rates had two distinct features: (i) in the optimum oxygen region to 1.25 O2/Ar vol%, the carrier mobilities increased as the carrier concentrations decreased with the oxygen flow rates and (ii) in the excess oxygen region roughly above 1.25 O2/Ar vol%, both the carrier concentrations and mobilities decreased with the increases in the oxygen flow rates. The continuous decreases in the carrier concentrations with the oxygen flow rates were due to filling the oxygen vacancies and deactivating the Sn donor by the overflowing oxygens. The behaviors of the carrier mobilities were affected by two different scattering mechanisms of (i) the ionized impurity scattering in the optimum oxygen region and (ii) the neutral defect scattering and the negatively charged oxygen scattering in the excess oxygen region.