Direct Transformation of Amorphous to Preferentially Oriented Rutile Phase in DC Sputtered TiO₂ Thin Film

Formation of preferentially (101) oriented rutile phase directly, without the conventionally observed intermediate anatase phase of TiO₂ is reported in thin films prepared by direct current (dc) magnetron sputtering of titanium metal target. The films were annealed at different temperatures between 400 and 1000 °C in air for 1 hour. The structural and micro structural properties of TiO₂ thin film, investigated by glancing angle X-ray diffraction and atomic force microscopy (AFM) indicated that the rutile grains are single crystalline and these grow preferentially along (111) plane with increasing annealing temperature. The as-deposited titanium thin film was amorphous, whereas the titanium thin film annealed in the range of 400–1000 °C showed phase pure rutile structure. The root mean square roughness estimated from AFM study is found to increase with annealing temperature and rate of increase was identical to that of the grain size. The present study thus addresses the question of the phase transformation mechanism in TiO₂ on annealing at high temperatures leading to the formation of preferentially oriented rutile phase without the formation of the intermediate anatase phase.