硅纳米孔柱阵列的结构和光学特性研究

采用水热腐蚀技术在单晶硅衬底上制备出一种新的硅微米／纳米结构复合体系——硅纳米孔柱阵列(Si-NPA)，并对其表面形貌、结构及光学特性进行研究.Si-NPA的结构复合性体现为 在微米和纳米两个尺度上形成了三个分明的结构层次，即微米尺度的硅柱阵列结构、硅柱上 的纳米多孔结构以及组成孔壁的硅纳米晶粒.积分光反射谱和荧光光谱测试表明，Si-NPA具 有良好的光吸收和光致发光特性.依据Si－NPA积分反射谱的实验数据，采用Kramers-Kronig 变换关系计算得到了Si-NPA的复折射率和复介电函数、吸收系数等光学常数，并由此讨论了 Si-NPA相对于单晶硅的光学特性发生显著变化的原因.最后，通过分析Si-NPA的光吸收系数 与入射光子能量之间的关系，揭示出Si-NPA具有直接带隙半导体的电子结构特征，而且理论 计算得到的Si-NPA的带隙能与其光致发光谱的峰位能很好符合. 关键词： 硅纳米孔柱阵列 光学特性 电子结构 水热腐蚀

Investigations on the structural and optical properties of silicon nanoporous pillar array

A novel silicon-based micron/nanometer structural composite system, silicon nanoporous pillar array(Si-NPA), was prepared on the substrate of single-crystal si licon (sc-Si) wafers by a hydrothermal etching method; and the studies on its mo rphological structural and optical properties were carried out. Structural exper iments disclose that Si-NPA could be well described by triple hierarchical struc tures: the array composed of micron-sized silicon pillars, the nanopores densely distributing on each pillar, and the silicon nanocrystallites constructing the walls of nanopores. Optical measurements prove that Si-NPA has good performances on light absorption and photoluminescence(PL). Based on the experimental data o f the integral reflectance spectrum, the structural and optical parameters such as complex refractive index, complex dielectric constant and absorption coeffici ent of Si-NPA are calculated by adopting Kramers-Kronig transformation; based on which, the origin of the notable difference between the optical properties of S i-NPA and sc-Si is discussed. Through analyzing the function relation between th e absorption coefficient of Si-NPA and the photon energy of incident light, the characteristic of the electronic structure of Si-NPA is proved to be that of a d irect-band-gap semiconductor, and the calculated bandgaps agree well with the PL peak energies given by experiments.