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 deg. 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 deg. 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 deg. 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 deg. C, the amorphous IZO phase may crystallize either in the cubic bixbyite or in a recently observed rhombohedral phase