OPTICAL-PROPERTIES OF SILICON AND ITS OXIDES

We have measured the inelastic electron scattering spectra of a variet y of Si and SiO2 thin films from the fundamental absorption threshold to well above the L-shell thresholds. We have used Kramers-Kronig anal yses and sum rules to obtain the dielectric and optical response funct ions. 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 a bsorption regions. The interband structure in crystalline Si shows thr ee sharp peaks that are blended into a single broad peak in the amorph ous samples. At the L threshold crystalline Si also shows more structu re than amorphous Si, however, the overall shape in the region well ab ove the threshold is quite similar in the three samples. Above the SiO 2 band gap the three oxide samples show strikingly similar behavior.