多孔硅量子点中的电子局域态

Localized electron state on porous silicon quantum dots

经过激光辐照和高温退火加工能够生成多孔硅样品,在650—780 nm处检测到很强的光致荧光(PL)峰,并且有明显的钉扎和增强效应.实验表明,这种PL发光的强度与样品受辐照和退火的时间长短密切相关.通过第一性原理模拟计算发现,样品表面用Si O双键和Si—O—Si桥键钝化,能隙中会出现电子局域态.激光辐照和高温退火的时间长短决定了样品表面Si O双键和Si—O—Si桥键的密度,而该密度正是影响多孔硅量子点中电子局域态生成的关键.

Porous silicon can be fabricated by laser irradiation and annealing. The center wavelength of photoluminescence （PL） band is pinned in the region of 700-780 nm and its intensity increases obviously after oxidation of the sample. It was found that the PL intensity changes with time of laser irradiation and annealing. Calculation shows that some localized states appear in the band gap of the smaller nanocrystal when Si=0 bends or Si--O--Si bonds are passivated on the surface. It was discovered that the number of SilO bonds or Si--O--Si bonds, which are related to irradiation and annealing time, obviously affects the generation of localized gap states.