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

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(k)In₂O(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).