Study on high-density excited states and optical processes in semiconductor nanostructures by spatial-and time-resolved spectroscopy

我们利用空间分辨激光光谱和时间分辨激光光谱研究了半导体纳米结构的基本光学性质和高密度激发态。我们探索了独特的半导体纳米结构中的新的光学功能，如纳米粒子量子点、杂质掺杂纳米粒子和碳纳米管。这些半导体纳米结构样品是非均匀体系，因为它们具有广泛的尺寸和形状分布以及表面结构和周围环境的变化。空间和时间分辨光学光谱学使理解纳米结构的固有光学性质和固有光学功能成为可能。首先，我们发展了纳米颗粒和纳米管样品的制备方法以及空间和时间分辨激光光谱技术。利用这些样品制备和光学光谱技术，我们研究了半导体纳米结构中的高密度激发态。我们改进了我们的激光光谱系统，用于宽光谱范围和温度下的光学测量，并通过光学显微镜和飞秒激光的集成开发了一种新的光谱系统。我们进一步研究了半导体纳米结构，包括半导体纳米粒子、杂质掺杂纳米粒子、硅纳米线、碳纳米管和块体混晶样品在高密度激发下的光致发光光谱和动力学。讨论了低维半导体纳米结构中的激子多体效应和高密度激发效应。

We studied fundamental optical properties and high-density excited states in semiconductor nanostructures by means of space- and time-resolved laser spectroscopy. We explored novel optical functionalities in unique semiconductor nanostructures such as nanoparticle quantum dots, impurity-doped nanoparticles, and carbon nanotubes. These semiconductor nanostructure samples are inhomogeneous systems in the sense that they have broad distributions of size and shape and variations of surface structure and surrounding environment. Space- and time-resolved optical spectroscopy makes it possible to understand intrinsic optical properties and inherent optical functionalities of nanostructures. First, we developed the fabrication methods of nanoparticle and nanotube samples and the techniques of space- and time-resolved laser spectroscopy. Using these sample preparation and optical spectroscopic techniques, we studied high-density excited states in semiconductor nanostructures. We improved our laser spectroscopy systems for optical measurements at wide spectral region and temperatures and also developed a new spectroscopic system by the integration of an optical microscope with a femtosecond laser. We further investigated the photoluminescence spectra and dynamics under the high-density excitation in semiconductor nanostructures including semiconductor nanoparticles, impurity-doped' nanoparticles, silicon nanowires, carbon nanotubes, and bulk mixed crystal samples. We discussed the exciton many-body effects and high-density excitation effects in low-dimensional semiconductor nanostructures.