多孔硅PL谱的影响因素分析

通过阳极氧化电化学方法制备了多孔硅,并在室温下对不同条件下制得的多孔硅光致发光谱(PL谱)进行系统的分析.结果表明,随着阳极电流密度、阳极化溶液浓度和时间的增大,多孔硅的PL谱峰将发生"蓝移",并且PL峰强也显著增加,但过大的电流密度、阳极化溶液浓度和时间将导致PL峰强下降.另外,还发现PL谱存在多峰结构,而多孔硅在空气中放置时间的延长将引起其PL的短波峰"蓝移"和强度下降,但对长波峰只引起强度减弱,并不影响其峰位.PL谱的多峰结构可以认为是由于样品中同时存在"树枝"状和"海绵"状两种微观结构所产生的,在这个假设下,用多孔硅氧化后发光中心从硅表面移到二氧化硅层及量子限制模型能够解释上述现象.

Effect of Fabrication Conditions and Aging Time on Photoluminescence of Porous Silicon

Samples of porous silicon are fabricated by an electrochemical approach and photoluminescent properties of PS are studied systematically.It is found that,with the incresing of the current density,anodizing time and HF concentration in etching solution,the peaks of PL occures the blue shift,as well as intensity for peaks is enhanced.But excessive current density,anodizing time or HF concentration would bring the decrease of PL intensity.The results also shows that PL spectra have a multi peak structure.When PS are exposed to the air,the oxidation of PS would cause both blue shift of position and degradation of intensity for the peaks with short photoluminescent wavelength,and only cause a great deal decrease of the intensity of the long wavelength peaks.The multi peak structure of PL spectra might be interpreted by PS samples comprising two different microstructures,branched and spongy structures.The branched PS is related to the peaks at short wavelength and spongy PS is corresponded to peaks at long wavelength.And branched PS is oxidized more easily than spongy one when they are exposed to the air.All the above phenomena could be understood in the quantum confinement and luminescence center model.