不同功率激光激发下多孔硅拉曼光谱研究

Study on Raman Spectra of Porous Silicon with Different Excitationpower

利用阳极氧化化学腐蚀法得到多孔硅样品,在632.8 nm激光激发下,对多孔硅的拉曼光谱随激光功率的变化进行了研究,分别得到了520 cm-1和300 cm-1附近的拉曼光谱图.发现在520 cm-1附近,激光功率较低时,多孔硅的拉曼光谱主要表现为略低于520 cm-1的尖锐单峰,随激光功率的增大,拉曼峰出现红移和不对称展宽,并且当激光功率增加到一定阈值时,单峰劈裂成双峰.而300 cm-1附近,随功率增大,峰位向低波数移动,但始终是单峰.我们对实验现象进行了分析和讨论,表明520 cm-1附近拉曼峰的红移和展宽是光学声子的量子限制效应引起的,激光功率达到一定阈值时,LO和TO声子模发生劈裂,所以单峰变为双峰.根据520 cm-1附近斯托克斯和反斯托克斯拉曼振动谱峰的强度比,我们计算了多孔硅样品表面在激光辐照下的局域的温度.

Porous Silicon（PS） sample is prepared by anodization.Raman spectra of porous silicon with different laser power have been studied.Only a sharp single band near 520 cm-1 appears when the exciting laser power is low,while it shifts to the red side and shows dissymmetrical broadening with the increase of the laser power.When the laser power gets strong enough,the Raman peak near 520 cm-1 is splitted into two bands The band near 300 cm-1 also shifts to lower wavenumbers with increasing the laser power.However,no peak splitting was observed near 300 cm-1.The red-shift and dissymmetrical broadening of Raman bands can be attributed to quantum confinement effect.Double bands near 520 cm-1 at high powers are thought to be the cleavage of longitudinal optical（LO） and transverse optical（TO） modes.The local temperature of PS under the laser radiation is also calculated in the article.