The behaviors of the carrier concentrations and mobilities in indium–tin-oxide thin films by DC and RF-superimposed DC reactive magnetron sputtering at the various process temperatures

Indium–tin-oxide (ITO) thin films were deposited by DC and RF-superimposed DC (RF-DC) reactive magnetron sputtering at the various process temperatures from 70 to 380 8C. And the behaviors of the carrier concentrations and mobilities in ITO thin films by different plasma excitation modes were investigated by means of the Hall technique. The relationship between the carrier concentrations and mobilities in ITO thin films by both DC and RF-DC sputtering had two distinct regions: (i) region I at low process temperatures, where both the carrier concentrations and mobilities increased together; (ii) region II at high process temperatures, where the carrier concentrations further increased but the carrier mobilities decreased. At low process temperatures of region I, the crystallinities were low and the grain boundary scattering was dominant. However, at high process temperatures of region II, ITO thin films were highly crystallized and the ionized impurity scattering from high carrier concentrations was dominant. The overall characterizations, related to the carrier concentrations and mobilities, were also performed using X-ray diffractometer, scanning electron microscopy, UV/vis/NIR spectrometer and atomic force microscope.