Visible luminescence from silicon quantum dots and wells

We discuss the mechanism of efficient photoluminescence (PL) from Si quantum dots and wells. Luminescence properties of SiO2-capped Si nanocrystals are different from those of H-terminated Si nanocrystals, but are similar to those of two-dimensional Si quantum wells sandwiched by SiO2 layers. The size dependence of PL properties and resonantly excited PL spectra of SiO2-capped Si nanocrystals indicate that excitons are localized near the nanocrystal surface and the strong coupling of localized excitons to surface oxide vibrations causes broad PL spectra in the visible spectral region. The localization of excitons near the interface between crystalline Si (c-Si) and surface oxide layer is attributed to efficient luminescence in nanoscale c-Si/SiO2 systems such as zero-dimensional nanocrystals and two-dimensional quantum wells