Heat treatment effects on electrical and optical properties of ternary compound $In2O3–ZnO$ films

Heat treatment effects on the electrical and optical properties are investigated for $In2O3–ZnO$ film with a Zn content $[Zn/(In+Zn)]$ of 33 at. %. Thin films deposited in a mixed gas atmosphere $(Ar+20% O2)$ by a magnetron sputtering method show high resistivity of about $1.7×10−1 Ω cm.$ A mixture of $In2O3$ (99.999%) and ZnO (99.999%) powders calcined at 1000 °C in an Ar atmosphere for 2 h was used as the target. On the other hand, the films deposited in a pure Ar gas environment show low resistivity of about $3×10−4 Ω cm,$ comparable to that of indium tin oxide films $(10−4 Ω cm).$ After heat treatment at 650 °C in vacuum, it was found that the films deposited in a mixed gas atmosphere revealed low resistivity similar to that of films deposited in a pure Ar gas. For these annealed films, their electrical properties are very stable when treated at temperatures up to 500 °C in air or 650 °C in vacuum. Also, it is found that the optical band gap of $In2O3–ZnO$ films increase (or decrease) after the heat treatment in vacuum (or $O2$ atmosphere). These effects are mainly due to the change in carrier concentration before and after heat treatment.