An abrupt switch between the two photoluminescence bands within alkylated silicon nanocrystals
An abrupt switch between the two photoluminescence bands within alkylated silicon nanocrystals
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DOI：
10.1088/0022-3727/44/49/495301
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发表时间：
2011-12
期刊：
影响因子：
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通讯作者：
P. Coxon;Qi Wang;Y. Chao
中科院分区：
文献类型：
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作者：
P. Coxon;Qi Wang;Y. Chao
研究了一系列烷基化硅纳米晶体 (SiNC) 的光致发光 (PL) 光谱，这些烷基化硅纳米晶体 (SiNC) 源自通过不同电流密度蚀刻形成的多孔硅晶片。在高电流密度 (382 mA cm−2) 下蚀刻的晶圆上的 SiNC 在 609 nm 处发出橙色光，而在 13 mA cm−2 的电流密度下蚀刻的晶圆上形成的较小的 SiNC 发出蓝色光 (395 nm)，但与当前对量子限制及其在带隙工程中的作用的理解相反，在中等电流密度下蚀刻的晶圆上的 SiNC 发出的光没有显示出两个波段之间的过渡，而是观察到了它们之间的突然切换。 SEM 图像显示，当硅表面在高电流密度下经历电化学蚀刻时，许多较小的纳米结构被破坏，只留下较大、更有弹性的纳米结构可进行硅氢化。 X射线光电子能谱测量表明，“蓝色”和“橙色”SiNC均包含大量Si-C和Si-O，因此橙色发射的性质可能与Si/SiO2界面附近形成的二氧化硅或低氧化物中的缺陷态有关，这些缺陷态填充了带隙并改变了发射特性。这是文献中第一篇揭示蚀刻电流密度与烷基化 SiNC 的 PL 发射带之间关系的论文。
Photoluminescence (PL) spectra from a series of alkylated silicon nanocrystals (SiNCs) derived from porous silicon wafers formed through etching at different current densities have been investigated. SiNCs from wafers etched at high current density (382 mA cm−2) emit orange at 609 nm while smaller SiNCs formed from wafers etched at current density of 13 mA cm−2 emit blue (395 nm), yet counter to current understanding of quantum confinement and its role within bandgap engineering, luminescence from SiNCs from wafers etched at intermediate current densities show no transition between the two bands, rather an abrupt switch between them is observed. SEM images show that as the silicon surface undergoes electrochemical etching under high current density many of the smaller nanostructures are destroyed leaving only the larger, more resilient nanostructures available to undergo hydrosilation. X-ray photoelectron spectroscopy measurements identify that both ‘blue’ and ‘orange’ SiNCs comprise a large degree of Si–C and Si–O thus the nature of the orange emission is likely related to defect states in silica or suboxide formed near the Si/SiO2 interface which populate the bandgap and modify the emission character. This is the first paper in the literature to unveil the relationship between etching current density and PL emission bands of alkylated SiNCs.