Interface of epitaxialSrTiO3on silicon characterized by transmission electron microscopy, electron energy loss spectroscopy, and electron holography

Abstract

The interfacial oxygen diffusion during film growth often results in the appearance of a thin ${\mathrm{SiO}}_{x}$ layer in ${\mathrm{SrTiO}}_{3}∕\mathrm{Si}$ films and related heterojunctions. High-resolution TEM investigations on the ${\mathrm{La}}_{0.9}{\mathrm{Sr}}_{0.1}{\mathrm{MnO}}_{3}∕{\mathrm{SrTiO}}_{3}∕\mathrm{Si}(\mathrm{LSMO}∕\mathrm{STO}∕\mathrm{Si})$ heterojunctions suggested that the thickness and microstructure of the ${\mathrm{SiO}}_{x}$ interfacial layer change visibly from one sample to another grown under slightly different conditions. Electron diffraction observations demonstrated the epitaxial relationships in the $\mathrm{LSMO}∕\mathrm{STO}∕\mathrm{Si}$ heterojunction as ${[001]}_{\mathrm{LSMO}}\ensuremath{\Vert}{[\ensuremath{-}110]}_{\mathrm{Si}}$, ${[110]}_{\mathrm{LSMO}}\ensuremath{\Vert}{[001]}_{\mathrm{Si}}$ and ${[001]}_{\mathrm{STO}}\ensuremath{\Vert}{[001]}_{\mathrm{Si}}$, ${[010]}_{\mathrm{STO}}\ensuremath{\Vert}{[\ensuremath{-}110]}_{\mathrm{Si}}$. The electron energy loss spectroscopy analyses on the $\mathrm{LSMO}∕\mathrm{STO}∕\mathrm{Si}$ interfacial region indicated that the Si ions are in intermediate oxidation states in the amorphous layer and the interfacial Ti bonding changes slightly. Electron holography measurements indicated that the energy barrier between the Si substrate and the LSMO film is about $0.95\ifmmode\pm\else\textpm\fi{}0.16\phantom{\rule{0.3em}{0ex}}\mathrm{V}$, where notable negative charges accumulate in the amorphous ${\mathrm{SiO}}_{x}$ layer.