Fabrication and spectroscopic studies of a-Si/SiO2 superlattices

Amorphous Si/SiO2 superlattices have been deposited on glass substrates usi ng two-target alternation magnetron sputtering technique. The samples are c haracterized using transmission electron microscope and low-angle X-ray ref lectance techniques. The results indicate that most of the regions in Si la yers consist of amorphous phase in the superlattices, while the regular str ucture appears in some local regions rarely. The thicknesses of Si layers a re in a range from 1.8 to 3.2 nm and the thickness of SiO2 layer is 4.0 nm in all cases. The samples are systematically studied using absorption, phot oluminescence (PL) and Raman spectroscopy techniques. The absorption edge p ositions and PL peaks shift towards shorter wavelengths while Raman spectra show broader peaks with decreasing Si layer thickness. The results are mai nly attributed to the quantum confinement effects.