单个半导体纳米结构中相干声学声子的超快动力学研究

The coherent acoustic phonon in semiconductor nanostructures draws wide attentions due to its unique physical properties, which has potential applications in novel optical-acoustic devices. The single nanostructure in-situ measurement can effectively avoid the influence from the inhomogeneity of the size and shapes of nanostructures in ensemble measurements, improving the accuracy of measurement. To develop the time-resolved spectrum technique and improve the measurement sensitivity is the key point for this study. This project plans to systematically study the coherent acoustic phonon in semiconductor nanostructures by time-resolved second-harmonic polarimetric spectrum, and presicely determine its mode, frequency, period and dephasing time under different size, shape, crystal phase and enviromental conditions. The novel semiconductor/noble-metal nanoparticles are fabricated to enhance SHG efficiency, realizing the in-situ measurement of a single nanoparticle (<20 nm). By revealing the new properties and physical mechanism of the coherent acoustic phonon in the nanoscale, it provides important information for novel optical-acoustic devices and high-resolution imaging.

半导体纳米结构中的相干声学声子以其独特的物理特性引起了广泛的关注，在新型纳米声光器件等方面有重要应用前景。而单个纳米结构原位测量的研究方式，有效避免了多个纳米结构中尺寸、形状等因素涨落的影响，确保了测量的准确性，但也导致有效信号较弱的问题。针对性地改进和发展时间分辨光谱技术，提高探测灵敏度是其关键所在。本项目提出了利用时间分辨SHG偏振光谱技术研究单个半导体纳米结构中相干声学声子的新方案并拟开展系统研究，精确测定半导体纳米结构中相干声学声子的振动模式、频率、周期和退相干时间等关键参数，并系统研究其随纳米结构尺寸、形状、晶相、晶轴方向和周围环境等因素的变化规律；采用贵金属/半导体复合纳米结构增强SHG转换效率，实现较小尺寸（<20 nm）单个纳米颗粒的原位超快动力学研究，揭示纳米尺度下相干声学声子的新特性、新机理，为新型纳米声光调制器、高分辨成像等应用提供重要依据。