Manipulation of film quality and magnetic properties of CrO2 (100) films on TiO2 substrates with carrier gas and growth temperature

High-quality CrO2 films were synthesized on TiO2 (100) substrates at different temperatures using the chemical vapor deposition method in argon or nitrogen atmosphere. It was found that the lower limit for the growth temperature of CrO2 films can be reduced to 310 or 300 degrees C when using Ar or N-2 as the carrier gas, respectively. The quality of CrO2 film on TiO2 substrate can thus be improved by optimizing growth temperature in a much larger range (310-400 degrees C in Ar and 300-430 degrees C in N-2, in contrast with 390-410 degrees C in O-2), which is significant for the practical application of CrO2 films. The best film quality was achieved at 320 degrees C in either Ar or N-2 atmosphere, at which CrO2 film has its narrowest orientation distribution and lowest roughness. Compared to films grown in O-2, films grown in Ar were found to have larger saturation magnetizations (M-s) and magnetic anisotropies, possibly due to numerous O vacancies. Films grown in N-2 are actually N-doped films, and have lower M-s than those grown in O-2. The Curie temperature (T-c) was also tuned by the carrier gas and growth temperature. Films grown in Ar or N-2 generally have a higher T-c value than those grown in O-2. Furthermore, the thermal stability of the films was found to be remarkably improved when using N-2 as the carrier gas.