Spectroscopic ellipsometric and He backscattering analyses of crystalline Si-SiO2 mixtures grown by molecular beam epitaxy

Single-crystal layers of silicon oxide (SiOz) grown on crystalline Si (c-Si) substrates by molecular beam epitaxy have been analyzed by spectroscopic ellipsometry (SE) and 2.2-MeV He backscattering. The optical properties of SiOz clearly indicate that it is a phase-separated mixture of c-Si and SiO2. Backscattering data combined with the SE results show that SiOz consists of 43 vol. % c-Si, 43 vol. % voids, and 14 vol. % SiO2. The results suggest that registry is preserved by the c-Si inclusions, which also act as nucleation sites for subsequently grown epitaxial c-Si films. The tendency of SiOz to oxidize rapidly at high temperature suggests that it may be useful for dielectrically isolating epitaxial c-Si films.