OPTICAL-PROPERTIES OF SILICON AND ITS OXIDES

We have measured the inelastic electron scattering spectra of a variety of Si and SiO2 thin films from the fundamental absorption threshold to well above the L-shell thresholds. We have used Kramers-Kronig analyses and sum rules to obtain the dielectric and optical response functions. We compare the optical properties of crystalline and evaporated and hydrogenated amorphous Si, amorphous evaporated SiO and SiO2, and chemical-vapor-deposition SiO2 in both the interband and the L-shell absorption regions. The interband structure in crystalline Si shows three sharp peaks that are blended into a single broad peak in the amorphous samples. At the L threshold crystalline Si also shows more structure than amorphous Si, however, the overall shape in the region well above the threshold is quite similar in the three samples. Above the SiO2 band gap the three oxide samples show strikingly similar behavior.