Structural and physical characterisation of transparent conducting pulsed laser deposited In2O3–ZnO thin films

Abstract

Indium–zinc oxide thin films, with compositions ranging from In₂O₃ to ZnO, were prepared by pulsed laser deposition using a substrate temperature of 500°C and an oxygen pressure of 10⁻³ mbar. X-Ray diffraction studies coupled with transmission electron microscopy revealed that the texture and the structure of the films are composition dependent with however a preferred orientation for all compositions, excluding In₂O₃ for consideration. As the Zn/(Zn + In) atomic ratio increased, the film structure evolved from cubic In₂O₃ to hexagonal ZnO via a hexagonal layered Zn_kIn₂O_k + 3 structure. An average transmittance of 85–90% in the visible region was obtained for all films independently of the composition. The maximum conductivity (σ = 1500 S cm⁻¹) was reached for a film having an atomic ratio Zn/(Zn + In) = 0.5 (i.e. Zn₂In₂O₅).