Structural Characterization of $Y_{2}O_{3}$ Films Grown on Sapphire by MBE

Yttrium oxide is a hard, thermally stable, transparent oxide, making it an excellent host for rare earth ions used in solid state laser waveguides. The structural quality of the these thin films can be expected to affect the emission cross section of the active ions and losses in the waveguide due to absorption and scatter. $Y_{2}O_{3}$ films were deposited on A, M, R and C plane sapphire substrates by molecular beam epitaxy. X-ray diffraction and transmission electron microscopy measurements were performed in order to determine the structure of the films. The films exhibited a textured mosaic structure (111) oriented with all substrates. The grains were found to be twinned with strong in plane orientations on A,R and C plane substrates but randomly oriented on M-plane. Grain size and tilt were dependent on the orientation of the sapphire substrate. R-plane substrates gave the highest quality films with larger grains and less mosaic tilt. This is likely due to better lattice matching between the substrate and film.