对比研究了经20%的硝酸、浓硫酸,以及半导体工业中用于氧化清洗单晶硅表面的SC-1(1:1:5,体积比,NH4OH/H2O2/H2O,也称RCA-1)和SC-2(1:1:6的HCI/H2O2/H2O,也称RCA-2)氧化液氧化的多孔硅表面组成以及光致发光性质的差异。发现SC-1氧化液能在几十秒的时间内将多孔硅表面的Si—H,(x=1—3)氧化掉,形成稳定的氧化层,得到具有较强的光致发光性能的氧化多孔硅。而硝酸、浓硫酸和SC-2液在相同温度下处理10min的多孔硅表面的(O)4Si—Hy振动峰仍很明显,前两者处理后的多孔硅发光强度很弱,SC—1处理后的样品虽然发光较强,但不稳定。结合SC-1的组成和多孔硅表面Si—Hx的性质,对反应结果进行了解释。将SC-1和SC-2结合使用,所得的氧化多孔硅具有强的且稳定的光致发光特性。
This discovery of the light emission of porous silicon (PS) has led to much excitement at the prospect of dev the freshly eloping Si based optoelectronic devices. However, the Si-H species, which are the passivation of 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 ahemative 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, oxidation has a detrimental effect on the photoluminescence (PL) efficiency. SC-1 (NH3H2O/HEOE/H2O,1: 1: 5, V/V) and SC-2 (HCl/H2OE/H2O, 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 HNO3 and H2SO4. 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.