We have synthesized, by Molecular Beam Epitaxy (MBE), Si/CaF2 multilayers which are optically active at room temperature. The photoluminescence spectra present a blue shift far decreasing Si layer thickness, in analogy to those obtained from porous silicon when the porosity is increased. We find a critical dependence of the photoluminescence efficiency on the thickness of the Si layers. We compare the experimental results to ab initio calculations of the band structure of Si/CaF2 multilayers which predict the band gap opening and the presence of confined and interface states leading to a quasi-direct band gap.

Light emission at room temperature from Si/CaF2 multilayers / Fa, D'Avitaya; L., Vervoort; F., Bassani; Ossicini, Stefano; A., Fasolino; F., Bernardini. - In: EUROPHYSICS LETTERS. - ISSN 0295-5075. - STAMPA. - 31(1995), pp. 25-30.

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