ELECTRONIC SPECTROSCOPY AND PHOTOPHYSICS OF SI NANOCRYSTALS - RELATIONSHIP TO BULK C-SI AND POROUS SI
ELECTRONIC SPECTROSCOPY AND PHOTOPHYSICS OF SI NANOCRYSTALS - RELATIONSHIP TO BULK C-SI AND POROUS SI
复制标题
DOI：
10.1021/ja00115a025
复制
发表时间：
1995-03-15
影响因子：
15
通讯作者：
CITRIN, PH
中科院分区：
文献类型：
--
作者：
BRUS, LE;SZAJOWSKI, PF;CITRIN, PH
研究了在高温气溶胶装置中制备的表面氧化硅纳米晶体的结构表征、电子光谱和激发态动力学，以深入了解这些系统的可见光发射机制。结果与直接带隙 CdSe 纳米晶体、间接带隙 AgBr 纳米晶体、块状晶体硅和多孔硅薄膜进行了比较。随着硅晶粒直径减小到 1-2 nm，带隙和发光能量相应增加到接近 2.0 eV，即比体块 1.1-eV 带隙高 0.9 eV。吸收和发光光谱保持间接带隙状，具有强横向光学电子振动起源。室温下量子产率增加到约5%，但单分子辐射率保持相当长，类似于10(-3)-10(-4) s(-1)。硅纳米晶体和多孔硅的发光性质在大多数方面是一致的，来自尺寸依赖的、体积量子限制的纳米晶体态的简单发射。室温量子产率的增加并不是因为在受限系统中与辐射场的耦合更强，而是因为主导体硅发射的无辐射过程在纳米晶硅中明显较弱。纳米晶 AgBr 中也发生了一系列类似的变化。虽然先前对 CdSe 和 CuCl 纳米晶体的研究揭示了其光谱特性的尺寸范围，但此处显示的 Si 和 AgBr 纳米晶体研究揭示了其动力学特性的其他尺寸范围。
The structural characterization, electronic spectroscopy, and excited-state dynamics of surface-oxidized Si nanocrystals, prepared in a high-temperature aerosol apparatus, are studied to gain insight into the emission mechanism of visible light from these systems. The results are compared with direct-gap CdSe nanocrystals, indirect-gap AgBr nanocrystals, bulk crystalline silicon, and porous silicon thin films. As the size of the Si crystallites decreases to 1-2 nm in diameter, the band gap and luminescence energy correspondingly increase to near 2.0 eV, or 0.9 eV above the bulk 1.1-eV band gap. The absorption and luminescence spectra remain indirect-gap-like with strong transverse optical vibronic origins. The quantum yield increases to about 5% at room temperature, but the unimolecular radiative rate remains quite long, similar to 10(-3)-10(-4) s(-1) The luminescence properties of Si nanocrystals and porous Si are consistent, in most respects, with simple emission from size-dependent, volume-quantum-confined nanocrystal states. Room-temperature quantum yields increase not because coupling to the radiation field is stronger in confined systems, but because radiationless processes, which dominate bulk Si emission, are significantly weaker in nanocrystalline Si. An analogous series of changes occurs in nanocrystalline AgBr. While previous work on CdSe and CuCl nanocrystals has revealed size regimes for their spectroscopic properties, the Si and AgBr nanocrystal studies are shown here to reveal additional size regimes for their kinetic properties.