Preparation and optical absorption of InSb microcrystallites embedded in SiO2 thin films

Semiconductor InSb microcrystallites embedded in SiO2 thin films were prepared by the radio-frequency cosputtering technique. The structures of the thin films were characterized by transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The average size of the microcrystallites, depending on post-annealing temperature and time, is on the order of a nanometer. The absorption spectra of the films were measured and large blue shifts of the absorption edge were observed in a wide range from the ultraviolet to the infrared spectral regime. The blue shifts were attributed to the strong quantum confinement effect and explained qualitatively in terms of the effective-mass approximation. A large discrepancy between the theory and our experimental results was found and discussed, particularly considering the change of the effective mass of exciton in the InSb microcrystallites. (C) 1998 Elsevier Science Ltd. All rights reserved.