C60偶联多孔硅系统的蓝光发射

用G60作为表面钝化剂，与多孔硅进行偶联．发现当C60偶联多孔硅系统在空气中存储一年后，能够发射460nm左右的强烈蓝光．经过系统的测量和分析，认为蓝光起源的发光中心与SiO2体材料中的“自捕获激子”模型类似．它是由一个氧空位和一个间隙氧组成的，间隙氧同时和相邻的晶格氧形成过氧连接．光激发载流子来自于Si纳米晶粒的核心，辐射复合过程则在多孔硅表面的发光中心进行．进一步的电子束辐照和臭氧辐照实验证明了这个发光中心的存在．从FTIR谱的分析，推测是样品表面Si=O双键的缓慢变化促使了蓝光中心的自发产生．

Blue Emission from C60-coupled Porous Silicon Systems

Because of the great importance of blue emission in applications in modern full-color all-Si optoelectronics, many studies have focused on the blue-emitting properties of Si-based nanostructures. The complexity of microscopic details and few/limited theoretical research activities make the blue-emitting mechanisms still unclear. Therefore, more experimental and theoretical investigations are needed to further explore the blue-emitting origins in Si nanostructures. In this paper, we use C_(60) molecule as a kind of surface passivant to modify the electronic structure of porous silicon (PS). We reveal that when stored in air for more than one year, this kind of C_(60)-coupled system shows a strong blue emission at ~ 460 nm. After a full characterization of the blue emission properties, we suggest that the blue emission originates from the oxygen-related surface states which are a combination of both oxygen-excess and oxygen-deficient defects. This luminescent center is local at the surface of PS nanocrystal and has a structure similar to that of the "self-trapped exciton" in crystalline SiO_2. It is a pair of oxygen vacancy and interstitial oxygen. The interstitial oxygen also forms a peroxy linkage with neighboring lattice oxygen. The observed blue emission arises from the transition owing to transfer from one of the two trapped electrons occupying oxygen vacancy to the unoccupied O_2 orbit. Photogenerated carriers from Si nanocrystal cores and their radiative recombination in the luminescent center induce the observed blue emission. Electron beam and ultraviolet ozone irradiation experiments provide oxygen interstitials and oxygen vacancies, which forms a basis for the self-trapped excitons. We infer from the FTIR spectra that the change of Si=O bonding states may modify the surface stress of PS, which induces the generation of the blue radiative centers. This work improves the understanding of the blue-emitting origin in silicon/oxygen-related nanomaterials.