Study of visible luminescence features of porous Si

Canham首先报道了多孔硅的室温可见光致发光，此后人们对多孔硅产生可见光致发光的机理及其在光电子器件中的应用进行了大量的研究。到目前为止，PS样品中的可见发光是基于PS层形成的硅纳米结构中的量子限制效应或硅氧烷等宽禁带表面化学物种的形成而解释的。为了更准确地讨论强可见发光机制，还需要进一步的实验和理论工作。已报道的大部分光致发光光谱是在处理后的空气中测量的，而PS在不同处理过程中的光致发光光谱的动态变化尚不清楚。因此，对不同处理条件下的样品进行原位荧光分析将为我们理解PS可见发光的机制提供重要线索。在本研究中，可见…原位记录了多孔硅在几种处理过程中的发光和拉曼光谱的变化。在373K的Ar~+激光(488 Nm)照射下，F_2引起了光致发光(PL)带强度和峰位的变化。在曝光初期，750 nm处的发光带强度减弱，600 nm处出现一个新的发光带。在曝光开始30min后，光谱占主导地位，而750 nm处的谱带几乎消失。当F_2处理后的样品暴露在H_2O蒸气中时，750 nm附近的荧光强度增加。在处理过程中，由拉曼测量得到的F_2暴露期间多孔硅的平均颗粒尺寸保持不变。此外，还记录了样品在电化学处理过程中光致发光强度的变化。这些结果表明，样品物种的表面化学结构对观察到的荧光光谱特征有很大的影响。较少

Canham first reported a room-temperature visible photoluminescence (PL) from the porous silicon (PS) and since then a large number of investigations have been carried out on the mechanisms responsible for the visible PL as well as on its application to optoelectronic devices. The visible PL from PS samples has been explained, to date, on the basis of quantum confinement effects in Si nanostructures formed PS layrs or the formation of wide-gap surface chemical species such as siloxene. Further experimental as well as theoretical work should be needed for more precise discussion of the strong visible PL mechanisms. Most of the PL spectra reported were measured in air after the treatments and dynamic changes in the PL spectra of PS in the process of various treatments are yet to be elucidated. In situ PL analysis of the samples under the various treatments conditions would, thus, provide us an important clue to understand the mechanisms of the visible PL of PS.In the present study, visibl … More e luminescence and Raman spectral changes of porous Si during several treatments were recorded in-situ. An exposure to F_2 under Ar^+ laser light (488 nm) irradiation at 373 K leads to change in photoluminescence (PL) band intensity as well as its peak position. At early stage of the exposure, the PL band at 750 nm peak decreased in intensity and a new band emerged at 600 nm. After 30 min from the beginning of the exposure dominates the spectrum while the band at 750 nm almost disappeared. When the sample after the F_2 treatment was exposed to H_2O vapor, the PL intensity around 750 nm increased. The average particle size of the porous Si during the F_2 exposure evaluated from Raman measurements was remained unchanged during the treatments. Further, PL band intensity change of the sample during electrochemical treatments was recorded. The results showed that the PL intensity depended strongly upon the electrolytes.These results suggest that surface chemical structure of the sample species strongly influence the observed PL spectral features. Less