Thin single crystal Sc2O3 Films on Si (111) with very sharp interface

We report the MBE growth and single-crystal synchrotron x-ray characterization of very high quality Sc$_{2}$O$_{3}$ films grown on Si (111). The Sc$_{2}$O$_{3 }$films of 3.5 and 18 nm thickness were deposited by e-beam evaporation on Si in a multi-chamber MBE/UHV system. Streaky RHEED patterns with a 4x4 reconstruction along the in-plane axes of Si were observed after an oxide growth $\sim $1 nm in thickness. X-ray diffraction results find that Sc$_{2}$O$_{3}$ films grow epitaxially in Bixbyite structure with the axis orientations aligned with those of Si. The 3.5 nm film yields a mosaic scan width of 0.044$^{\circ}$ (158 arc-sec.) for the Sc$_{2}$O$_{3}$ (444) peak, which is remarkably sharp, and suggests a defect free structure for the epi-layer. Since the bulk lattice constants of Si and Sc$_{2}$O$_{3}$ are mismatched by 9.2{\%}, the observed perfection in the film structure is very unusual. Electrical measurements of the Sc$_{2}$O$_{3}$ film exhibit low-leakage currents and cross-section TEM studies on Sc$_{2}$O$_{3}$/Si show an extremely sharp interface.