The photoluminescence(PL)of nanocrystal present in porous silicon shilts from the near infrared to the ultraviolet depending on the size when the surface is passivated with Si-H bonds.After oxidation,the center wavelength of PL band is pinned in the region of 700nm～750nm and its intensity increases obviously.Calculation shows that trap electronic states appear in the band gap of the smaller nanocrystal when Si=O bonds or Si-O-Si bonds are fomed.The changes in PL Intensity and wavelength can be explained by both quantum confinement and trap states in oxidation layer of nanocrystal.In the theoretical model,the most important factor in the enhancement and pinning effect of PL emission is the relative Dosition between the level of the trap states and the level of the photoexcitation in the silicon nanocrystal.%由Si-H键钝化的多孔硅的光致荧光(PL)发光频移遵循量子受限效应,随着纳米结构尺寸的变小PL发光频率从红外蓝移到紫外.多孔硅被氧化后,PL发光带的中心波长被钉扎在700nm～750nm范围,且强度明显增加.计算表明,氧化后的Si=O键或Si-O-Si键能在展宽的导带下方形成电子陷阱态.由此提出量子受限与氧化陷阱态模型可以很好地解释PL发光的钉扎和增强效应.该模型中的电子陷阱态扮演了重要的角色.
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