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

摘要

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 °C when using Ar or N₂ 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 °C in Ar and 300–430 °C in N₂, in contrast with 390–410 °C in O₂), which is significant for the practical application of CrO₂ films. The best film quality was achieved at 320 °C in either Ar or N₂ atmosphere, at which CrO₂ film has its narrowest orientation distribution and lowest roughness. Compared to films grown in O₂, 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 N₂ are actually N-doped films, and have lower M_s than those grown in O₂. The Curie temperature (T_c) was also tuned by the carrier gas and growth temperature. Films grown in Ar or N₂ generally have a higher T_c value than those grown in O₂. Furthermore, the thermal stability of the films was found to be remarkably improved when using N₂ as the carrier gas.