| Abstract | Six-period superlattices of Si/SiO2 have been grown at room temperature using molecular beam epitaxy. With this mature technology, the ultra-thin (1-3 nm) Si layers were grown to atomic layer precision. These layers were separated by ~1 nm thick SiO2 layers whose thickness was also well controlled by using a rate-limited oxidation process. The chemical and physical structures of the multilayers were characterized by cross-sectional TEM, X-ray diffraction, Raman spectroscopy, Auger sputter-profile, and X-ray photoelectron spectroscopy. The analysis showed that the Si layer is free of impurities and is amorphous, and that the SiO2/Si interface is sharp (~0.5 nm). Photoluminescence (PL) measurements were made at room temperature using 457.9 nm excitation. The PL peak occurred at wavelengths across the visible range for these multilayers. The peak energy position E was found to be related to the Si layer thickness d by E (eV) = 1.60+0.72d-2 in accordance with a quantum confinement mechanism and the bulk amorphous-Si band gap. |
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