The crystallization process of indium oxide thin films deposited by pulsed laser deposition was studied. X-ray diffraction was performed on amorphous films during real-time in situ annealing in vacuum at temperatures between 100 and 300 degrees C and a heating rate of 0.00847 degrees C/s. A fast crystallization was observed in the temperature range 165-210 degrees C. The crystallization kinetics obtained from the reaction equation shows activation energy of 2.31 eV, reaction order of 0.75 and reaction rate factor of 8.5 x 10(22) Hz. The structures of the in situ annealed films were compared with that of the films grown at different temperatures. The resistivity of the films is related to the structure, oxygen pressure and growth temperature. A low resistivity of 3.5 x 10(-4) Omega cm, which increased with increasing temperature and oxygen pressure, was obtained at 100 degrees C and 2 Pa. The increase in the resistivity was due to a depletion of oxygen vacancies. The optical refractive index of the films decreases with changes in the deposition conditions, with an average value being 2.04. (c) 2005 Elsevier B.V. All rights reserved.