Preparation of the oxidized porous silicon with stable surface composition and intense photoluminescence

This discovery of the light emission of porous silicon (PS) has led to much excitement at the prospect of developing Si based optoelectronic devices. However, the Si-H species, which are the passivation of the freshly prepared PS, are unstable, therefore the peak wavelength and efficiency of the luminescence is extremely sensitive to the preparation conditions and subsequent treatment of the sample, which has disturbing consequences for the suitability of this material for device applications. The growth of a high quality oxide around the surface of the Si crystals has been suggested as an alternative method of the PS surface passivation. Some progresses such as anodic oxidation, rapid thermal oxidation (RTO), hot water treatment and so on have been reported for the preparation of oxidized PS. In general, oxidatiori has a detrimental effect on the photoluminescence (PL) efficiency. SC-1 (NHHO/ HO/HO,1:1:5, V/V) and SC-2 (HCl/HO/HO, 1:1:6) solutions are two standard oxidant and clean reagent and have been utilized in the traditional silicon semiconductor industry for many decades. In this work, we exploited these two novel oxidant solutions to the preparation of oxidized PS. The characteristic of the oxidized PS prepared by oxidizing the freshly prepared PS in the solutions of SC-1 and, SC-2 have been studied by comparing with those prepared by thermal oxidization and those oxidized by other oxidants, such as HNO and HSO. It has been shown that SC-1 is an efficient oxidant for the preparation of oxidized PS with an intense PL and a simple and stable surface composition. The oxidized PS prepared in SC-1 for 30 s and then in SC-2 for 4 min has a more stable PL than that from the sample oxidized in only SC-2. It means a stable surface composition is very important for the stable PL.