Highly Efficient and Stable Photoluminescence of Nanocrystalline Porous Silicon by Combination of Chemical Modification and Oxidation under High Pressure

Abstract

A combination of high-pressure water vapor annealing (HWA) and chemical modification (CM) was used in order to fully passivate the nanocrystalline silicon surface of porous Si (PS) and electrochemically oxidized PS. The effects of these treatments on the surface chemistry are characterized by Fourier transform infrared spectroscopy in relation to the respective photoluminescence (PL) properties. The use of both HWA and CM enables a higher PL intensity than that of only HWA. The order in which the treatments are implemented greatly affects the final nanostructure and PL characteristics. The marked enhancement in PL efficiency by HWA was confirmed. PL efficiency is further improved by additionally performing CM, owing to further enhancement of surface passivation. The highest PL intensity was obtained when CM was performed before HWA. This may be explained by the enhanced surface passivation together with a better preservation of Si nanocrystals. For all the modified samples, PL stability was considerably enhanced compared with that of the reference sample.