A Growth Study of Conductive SrTiO₃ Thin Films on Silicon Platforms

The challenge of interfacing complex oxides with silicon has restricted their practical use in scalable oxide-based electronic devices. The growth of prototypical perovskite SrTiO 3 via molecular beam epitaxy has enabled commercially available SrTiO 3 /Si substrates, which can serve as a growth template for silicon-integrated complex oxides deposited using other techniques. Here, we deposit conductive Nb-doped SrTiO 3 (NSTO) thin films with pulsed laser deposition on commercial SrTiO 3 /Si substrates and compare the structural and electronic characteristics with NSTO deposited on perovskite single crystal (LaAlO 3 ) 0.3 (Sr 2 TaAlO 6 ) 0.7 (LSAT) as well as crystalline silicon terminated with SiO 2 or amorphous Si 3 N 4 . We find that NSTO thin films deposited on LSAT and SrTiO 3 /Si both result in epitaxial films with similar conductivity but with the lattice mismatch resulting in a biaxial compressive strain of −1.6% on LSAT, whereas the difference in thermal expansion coefficients between NSTO and SrTiO 3 /Si induces a biaxial tensile strain of +0.4%. In contrast, NSTO deposited on Si 3 N 4 /Si or SiO 2 /Si exhibit a mosaic-granular structure, where the conductive performance deteriorates drastically as the film thickness falls below the average grain size of the film (<30–50 nm). Our findings underscore the achievement of both superior epitaxial and transport characteristics in films grown on commercial SrTiO 3 /Si substrates compared to other silicon platforms, as well as advancing the successful integration of multifunctional oxides on silicon.