Microstructures, optical and electrical properties of In-doped ZnO thin films prepared by sol-gel method

ZnO and indium-doped ZnO (I _x ZO) thin films were prepared on silica-glass substrates by the sol-gel method. The thin films were crystallized at 600 °C and 700 °C for 1 h in 6.9 × 10 ^-1 Torr under pure O ₂ atmosphere. The analyzed results were compared to investigate the structural characteristics and optical properties. The surface morphology of the I _x ZO films was different from that of the ZnO films, and showed a thin overlay structure. In addition, the crystallization of I _x ZO film was depleted at higher crystallized temperatures. From XRD analysis, the ZnO and I _x ZO thin films possessed hexagonal structures. Notably, micro-In ₂ O ₃ phases were observed in the I _x ZO thin films using EDS. Both of In ₂ O ₃ phases and the crystallization mechanism not only improved the peeling of structure, but also improved the electrical conductivity of I _x ZO thin films. For the PL spectrum, the optical property of the I _x ZO film was raised at a higher crystallization temperature. Although the In ₂ O ₃ phases reduced the structural defects of I _x ZO thin film, the optical effect of the residual In ³⁺ was not enhanced completely at higher crystallized temperatures.