Absorption in a-Si/SiO2 superlattices

a-Si/SiO2 superlattices were grown on quartz by MBD (Molecular Beam Deposit ion) using in situ oxidation by an RF-plasma source. The a-Si layer thickne sses were varied from 0.5-2.5 nm while the SiO2 layer thicknesses (1.0 nm) were kept constant. Optical transmission and reflection measurements were p erformed on these samples at room temperature. The recorded spectra were th en analyzed with a commercial optical thin film analysis program. The band gaps were derived from constant-n and non-constant-n forms of Tauc and Cody laws. The observed blueshift of the band gap, with decreasing a-Si layer t hickness, is attributed to quantum confinement in the a-Si sublayers.