Ti doped Cr2O3 thin films: Atomic layer deposition, mechanical and optical properties

Abstract

Atomic layer deposition (ALD) of titanium doped chromium oxide (CTO) films on Si (100) and SiO2 substrates was studied using deposition formula of n× (CrO2Cl2 - CH3OH) + m × (TiCl4 - H2O). The CTO films contained α-Cr2O3 eskolaite phase when deposited at Ti/(Ti+Cr) atomic ratio values of 0–0.24. During the first ALD super cycle, the growth rate of the Ti-O on chromium oxide was 2.4 times higher compared to that on TiO2 and was explained by the differences of densities of oxygen atoms on the (001) plane of eskolaite compared to their density on (001) plane of anatase. At the same time only minor influence on the growth rate of chromium oxide depending on the Ti amount was detected. The hardness value of 20.5 GPa was obtained for CTO films at Ti/(Ti+Cr) atomic ratio of 0.24, higher than 14.8 and 12.2 GPa obtained for pure chromium and titanium oxide thin films, respectively. The doping of the chromium oxide with titanium increased the absorbance of the films in the wavelength range of 350 – 450 nm and decreased the band gap energy corresponding to the indirect transition from 3.0 eV for pure Cr2O3 to 2.2 eV.