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 degrees C and 700 degrees C for 1 h in 6.9 x 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-In2O3 phases were observed in the I(x)ZO thin films using EDS. Both of In2O3 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 In2O3 phases reduced the structural defects of I(x)ZO thin film, the optical effect of the residual In3+ was not enhanced completely at higher crystallized temperatures. (C) 2009 Elsevier B.V. All rights reserved.