16:15 〜 16:30
▲ [6p-S44-12] Photo-Assisted Dissolution of Porous Silicon Nanostructures in HF Solutions Monitored by Photoconduction
キーワード：porous silicon, optical absorption, nanostructure
Porous silicon (PSi) formed by electrochemical etching of lightly-doped silicon substrates in hydrofluoric acid (HF) exhibits a sponge-like nanostructure. It has potential applications in optoelectronics and photovoltaics because of new properties emerging from quantum confinement (QE), such as light emission and tunable optical absorption. After PSi formation, further chemical dissolution in HF can be used to increase the porosity. In an earlier work, we have used photoconduction to monitor the chemical dissolution of PSi in solutions containing HF [1,2]. The study also allowed the derivation of the PSi absorption coefficient for a very wide range of porosities, as well as the Si dissolution rate for various HF concentrations [2]. For high HF concentrations the chemical dissolution is very slow. In such case, dissolution can still be obtained at a rather high rate under illumination by photo-generation of holes in the PSi structure. We have studied the photo-assisted dissolution of PSi using the monitoring technique previously shown [1,2]. The effects of PSi thickness, illumination power and wavelengths were investigated. The photo-dissolution rate as a function of illumination power was found to reach a saturation state. A model of the photo-dissolution was also developed.