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 SrTiO₃ via molecular beam epitaxy has enabled commercially available SrTiO₃/Si substrates, which can serve as a growth template for silicon-integrated complex oxides deposited using other techniques. Here, we deposit conductive Nb-doped SrTiO₃ (NSTO) thin films with pulsed laser deposition on commercial SrTiO₃/Si substrates and compare the structural and electronic characteristics with NSTO deposited on perovskite single crystal (LaAlO₃)_0.3(Sr₂TaAlO₆)_0.7 (LSAT) as well as crystalline silicon terminated with SiO₂ or amorphous Si₃N₄. We find that NSTO thin films deposited on LSAT and SrTiO₃/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 SrTiO₃/Si induces a biaxial tensile strain of +0.4%. In contrast, NSTO deposited on Si₃N₄/Si or SiO₂/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 SrTiO₃/Si substrates compared to other silicon platforms, as well as advancing the successful integration of multifunctional oxides on silicon.