A study of amorphous and crystalline phases in In2O3–10 wt.% ZnO thin films deposited by DC magnetron sputtering

We report on the processing, phase stability, and electronic transport properties of indium oxide (In2O3) doped with 10 wt.% zinc oxide (ZnO) deposited to a thickness of 100 nm using DC magnetron sputter deposition at room temperature and 350 °C. We compare the optimum oxygen content in the sputter gas for pure In2O3 and doped with (i) 10 wt.% ZnO and (ii) 9.8 wt.% SnO2. Amorphous IZO films were annealed at 200 °C in air and N2/H2 and resistivity, Hall mobility, and carrier density along with molar volume change were monitored simultaneously as a function of time at temperature. We report that annealing the amorphous oxide in air at 200 °C does not lead to crystallization but does result in a 0.5% decrease in the amorphous phase molar volume and an associated drop in carrier density. Annealing in forming gas leads to an increase in carrier density and a small decrease in molar volume. We also report that when annealed in air at 500 °C, the amorphous IZO phase may crystallize either in the cubic bixbyite or in a recently observed rhombohedral phase.