Synthetic control of electron-phonon coupling in semiconductor quantum dots

半导体量子点电子声子耦合的综合控制

• 批准号: 1506803
• 负责人: Anne Kelley
• 金额: $ 52万
• 依托单位: University of California - Merced
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-07-15 至 2021-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1506803&HistoricalAwards=false
• 关键词: Synthetic; control; electron; phonon; coupling

With this award, the Macromolecular, Supramolecular, and Nanochemistry (MSN) Program is funding Professors Anne Myers Kelley and David Kelley at the University of California at Merced to apply laser-based spectroscopic techniques and computational modeling to study mechanisms whereby light energy is converted to heat in quantum dots (QDs) which are small semiconductor structures containing hundreds to thousands of atoms. The quantitative understanding that will be gained regarding these processes will enable the controlled chemical synthesis of QDs that are optimized for several types of technological applications. These include efficient solar energy capture and conversion, low power dissipation artificial lighting, and laser-based biological imaging for medical diagnostics. UC Merced is a Hispanic Serving Institution and more than half of its undergraduates are first-generation college students, and this research will actively involve both graduate and undergraduate students from traditionally underrepresented groups.This project aims to accurately measure and quantitatively understand the factors that determine the extent of electron-phonon coupling (EPC) in nanometer sized semiconductor quantum dots (QDs) and to synthetically control the extent of EPC. Preliminary calculations suggest that by judicious choice of materials and morphology it is possible to greatly increase or decrease the magnitude of EPC in core-shell and core-alloy-shell structures compared to single component QDs. Both well-known and novel structures based on II-VI semiconductors are synthesized and characterized and their EPC measured through quantitative resonance Raman spectroscopy, including analysis of absolute excitation profiles, overtone intensities, and depolarization ratios,. This study tests the hypothesis that EPC for optical phonons in polar crystals is determined largely by the amount of charge separation produced by electron-hole pair formation via the Fröhlich mechanism, and that it can be varied by controlling the valence and conduction band energies such that the electron and hole wavefunctions have different amounts of overlap. The novelty of this approach is to not only measure EPC accurately for specific materials but also engineer structures that permit the control of EPC.

凭借该奖项，大分子，超分子和纳米化学（MSN）计划资助默塞德的加州大学的Anne Myers Kelley和大卫Kelley教授应用基于激光的光谱技术和计算建模来研究量子点（QD）中光能转化为热量的机制，量子点是包含数百至数千个原子的小型半导体结构。 关于这些过程将获得的定量理解将使量子点的受控化学合成能够针对几种类型的技术应用进行优化。 这些包括高效的太阳能捕获和转换，低功耗人工照明，以及用于医疗诊断的激光生物成像。 加州大学默塞德是一所西班牙裔服务机构，超过一半的本科生是第一代大学生，本项目旨在精确测量和定量了解纳米半导体量子点中决定电子-声子耦合（EPC）程度的因素，综合控制EPC的程度。 初步计算表明，通过明智地选择材料和形态，与单组分QD相比，可以大大增加或减少核-壳和核-合金-壳结构中的EPC的大小。 合成和表征了基于II-VI族半导体的已知和新颖结构，并通过定量共振拉曼光谱测量了它们的EPC，包括绝对激发曲线、泛音强度和退偏振比的分析。 这项研究测试的假设，即EPC的光学声子在极性晶体中主要是由电子-空穴对形成通过Fröhlich机制产生的电荷分离量，它可以通过控制价带和导带能量，使电子和空穴波函数有不同的重叠量。 这种方法的新奇在于不仅可以精确测量特定材料的EPC，而且还可以设计允许控制EPC的结构。