石墨烯高能态处光激发载流子数目和能量的弛豫过程研究

项目名称： 石墨烯高能态处光激发载流子数目和能量的弛豫过程研究

项目编号： No.11504265

项目类型： 青年科学基金项目

立项/批准年度： 2016

项目学科： 数理科学和化学

项目作者： 赵欣

作者单位： 天津工业大学

项目金额： 20万元

中文摘要： 优异的光电性质使石墨烯在光电子器件上有着重要的应用前景。研究石墨烯光激发载流子数目和能量的弛豫过程对发展石墨烯光电子器件是非常必要的。目前，石墨烯载流子弛豫过程的研究主要集中在线性色散关系的低能态区(<0.8 eV,近红外-THz)。然而，在包含三角翘曲和非线性色散关系的高能态区(>0.8 eV,紫外-可见)的研究还很缺乏，这种能带结构将会影响载流子的散射，因而有必要研究高能态区光激发载流子的弛豫过程。本项目将围绕石墨烯光电子器件在紫外-可见光谱区应用相关的基础问题，对高能态处光激发载流子数目和能量的弛豫过程展开研究。内容包括：1.光激发载流子在动量空间数目分布的演化和机制；2.能量空间热载流子数目分布的弛豫和载流子倍增；3.基于能量空间热载流子的分布，研究可见光负差分透射信号的机制。期望通过该研究，为石墨烯光电子器件在紫外-可见光谱区的应用提供指导，并揭示激发态石墨烯瞬态吸收增强的机制。

中文关键词： 石墨烯；载流子；动力学过程；电子能带结构

英文摘要： The unique electronic band structure gives rise to remarkable electrical and optical properties for graphene, resulting in its important application in novel optoelectronic and photonic devices. For the development of graphene-based optoelectronic and photonic devices, a thorough understanding of the processes that govern number and energy relaxation of photoexcited carriers is essential. At present, the studies on ultrafast carrier dynamics of graphene mainly concentrate on the energetically low state with linear dispersion (<0.8 eV, nIR-THz). However, the study at the energetically high state with trigonal warping and nonlinear dispersion (>0.8 eV, UV-visible) is scarce. This anisotropic electronic band curvature at the energetically high state will change the scatterings of carriers, it is necessary to study the carrier relaxation at the energetically high state. In this project, we will focus on the fundamental issues of carrier relaxation processes, which should be met when the graphene photoelectronic devices are used in UV-Visible Spectroscopy. We will study on the number and energy relaxation processes of photoexcited carriers at energetically high state of graphene. Including: 1.Tracking the evolution of carrier distribution in momentum space during photoexcited carriers relaxing from excitation state to energetically lower and higher states and the physical mechanism; 2. Relaxation of carrier number distribution in energy space and carrier multiplication; 3. Studying the explanation on negative differential transmittance of graphene based on the carrier number distribution in energy space. From this research, we will pay the path for application of graphene photoelectronic devices at UV-Visible Spectroscopy, and reveal the physical mechanism of transient absorption enhancement of photoexcited graphene.

英文关键词： graphene;carrier;dynamics;electronic band structure