Crystalline Si/SiO2 quantum wells

Based on epitaxial layer transfer silicon on insulator wafers, crystalline Si/SiO2 quantum wells have been made. The chemical composition of the quantum wells was studied by Auger electron spectroscopy depth profile. The crystalline structure of the well was confirmed by x-ray photoelectron diffraction. Band-edge shifts in the conduction-band minimum and in the valence-band maximum were measured by using synchrotron x-ray absorption near-edge spectroscopy and by using laboratory x-ray photoelectron spectroscopy, respectively. It is found that the energy gaps of the quantum wells increase as the Si layer is reduced to below 3 nm, as expected for well-defined quantum wells. The experimental data provide direct evidence of a quantum-confined band-gap increase, which has been theoretically predicted for the crystalline Si/SiO2 quantum-well system.