Influence of annealing on structural and Micro- Hardness of nanocrystalline TiO2 Thin Films

Abstract

In the present study, TiO2 powder was used as the starting material to prepare thin films by conventional thermal evaporation using high vacuum coating unit type (Edwards E 306A). The surface topography and nanoparticles shape of TiO2 thin films as deposited and annealed at the temperatures 473, 673 and 873K were studied using the scanning electron microscope. The films showed good uniformity, crack free surface and nanoparticles with small ellipsoidal shape dispersing with high separations. The indentation experiments were carried out by using micro hardness tester showed the absence of monotonic behaviour and irregular thermally induced oscillations in the curves of the film hardness, HVf versus the annealing temperature. This behavior may be due to the combined effects of the applied factors; the temperature, the load and the dwell time, on the obtained HVf. Also the indentation size effect index (ISE), m, was calculated as 1.6 for the TiO2 films indicating that the hardnesss depends on indentation size.