A study of conduction in the transition zone between homologous and ZnO-rich regions in the In2O3–ZnO system

Abstract

Indium zinc oxide thin films were deposited by radio-frequency cosputtering and characterized by x-ray photoelectron spectroscopy (XPS), x-ray diffraction, energy dispersion x-ray spectrometry, Hall-effect measurement, and spectrophotometry techniques. All the films have $\text{zinc}∕(\text{zinc}+\text{indium})$ atomic ratio (define as $M$ ratio) higher than 0.60 and exhibited $n$ -type degenerate semiconductor behavior irrespective of their composition. The conductive films have been observed to have a very wide transmittance window $(300–2000\mathrm{nm})$ . An XPS analysis revealed a diminishing oxygen vacancy contribution to carrier concentration with an increase in the $M$ ratio. However, we observed a gradual decrease in carrier concentration until $M$ ratio of 0.79 and then, a significant rise in carrier concentration for $M$ ratio of 0.84, and this was attributed to the replacement of zinc from its lattice position by indium. The XPS studies also revealed asymmetry in zinc $2p_{3∕2}$ peak, which might be associated with the structure of this ternary system. The effect of the effective mass on the optical band gap of the films was also observed and discussed further.