Preparation and evaluation of alexandrite, forsterite, and topaz substrates for the epitaxial growth of rutile oxides

Metal–insulator transitions and superconductivity in rutile-structured oxides hold promise for advanced electronic applications, yet their thin film synthesis is severely hindered by limited substrate options. Here, we present three single-crystalline substrates, BeAl2O4, Mg2SiO4, and Al2SiO4(F,OH)2, prepared via optimized thermal and chemical treatments to achieve atomically smooth surfaces suitable for epitaxial growth. Atomic force microscopy confirms atomic step-and-terrace surface morphologies, and oxide molecular-beam epitaxy growth on these substrates demonstrates successful heteroepitaxy of rutile TiO2, VO2, NbO2, and RuO2 films. Among these unconventional substrates, BeAl2O4 exhibits exceptional thermal and chemical stability, making it a versatile substrate candidate. These findings introduce new substrate platforms that facilitate strain engineering and exploration of rutile oxide thin films, potentially advancing the study of their strain-dependent physical properties.