Influence of substrate orientation and pre-annealing treatment on the metal–insulator transition in V2O3 films: Insights from Al2O3<i>r</i>, <i>a</i>, <i>c</i>, and <i>m</i>-plane substrates

We investigate the structural and metal–insulator transition (MIT) behavior of epitaxial V2O3 films fabricated by reactive direct current magnetron sputtering on r, a, c, and m-plane Al2O3 substrates, in both as-received and annealed states. Characterization of MIT of the V2O3 films grown on annealed substrates demonstrated significant changes in observed MIT properties, i.e., r-plane films showed ≈2 order increase in transition magnitude, m-plane ≈6 orders, and c-plane films exhibited a reduction of ≈3 orders, compared to un-annealed substrates, whereas for V2O3 on annealed a-plane, it revealed a shift in the transition to higher values, with reduction in hysteresis width. Structural characterization conducted via x-ray diffraction and atomic force microscopy revealed a reduction in out-of-plane compressive strain for annealed substrates, along with decreased lateral grain size. Additionally, the correlation between the V2O3 MIT and its underlying structural phase transition was verified by temperature-dependent x-ray diffraction analysis. These findings highlight the role of substrate orientation and pre-annealing in tuning the MIT behavior of V2O3 films grown on the Al2O3 substrate.