Carrier band-to-band recombination in Mn-passivated porous silicon

Porous silicon (PS) was in situ passivated by Mn2+ and covered by a layer o f MnO2 using a hydrothermal technique. A 370 nm photoluminescence (PL) band , showing carrier 'band edge' recombination features, was observed, which a grees well with the inter-band transition of 3.4 eV detected by optical abs orption measurements. Silicon nanocrystallites several nanometres in size w ere able to cause conduction band splitting; then an inter-band transition of 3.4 eV was observed due to the carrier transition between the sub-conduc tion band to the valence band (Al). A high potential layer of manganese oxi de on the surface of the silicon nanocrystallites prevents excited carrier diffusion from the core of Si to neighbouring defects from nonradiative dec ay, and as a result enhances carrier band-to-band recombination, resulting in the ultraviolet PL (370 nm).