Change in surface roughness with the thickness of TiO2 film grown on MgO(001) by Ar-ion beam sputtering

Abstract

The surface roughness, Ra, and the crystallinity are studied for the rutile-type TiO2 films at their thickness, d, above 10 nm deposited on the air-cleaved MgO(001) held at 630 °C at 3.1×10−3 Pa in the partial pressure of O2 by sputtering the Ti target by Ar-ion beam accelerated with 1.2 kV. The amount of Ra estimated by observing the surface morphology with an AFM is the order of nanometers and changes with d according to d1/2. The linear relationship between the intensity ratio of the (110) peak for the TiO2 to the (004) peak for the MgO in x-ray diffraction pattern and d2 is also confirmed which is evidence of little change in the film crystallinity during growth. These mean that the surface morphology of the TiO2 films at d>10 nm keeping their crystallinity is determined from the statistical fluctuation in the impinging vapor flux.