飞秒、纳米时/空尺度热输运机理研究

The heat transport process at the femtosecond-nanometer scale, having strong non-equilibrium characteristics, is one of the most leading edge problems urgent to solve at present in the fields of thermophysics and even physics. In this program, the heat transport mechanism of the multiple energetic carriers at the femtosecond temporal scale, and the heat transport properties of the material interior and interface at the nanometer spatial scale are to be systematically investigated, through experiment as a dominant method, and theoretical analysis and numerical simulation as supports. Major tasks include: setting up a dual-wavelength femtosecond laser pump-probe system, substantially increasing the measurement precision (by 3 orders of magnitude), solving the problem of too low signal to noise ratio in the conventional single-wavelength system; simultaneously realizing the dynamic measurement of the heat transport characteristics at the femtosecond -nanometer resolutions with the aid of near-field optics, revealing the thermal rectification phenomenon at the solid-solid interface and the influence of the spatial-scale and structure on the thermal resistance of the interface; simulating the respective subsystems of the multi-energetic-carrier system by the method of solving BET, introducing and acquiring the relaxation time of the interaction between individual subsystems by experiment, revealing the physical mechanism of the heat transport process of the multi-energetic-carrier system. This program is to promote the perfection of the frame of heat transport theory at the femtosecond-nanometer scale, to provide scientific basis for solving the thermal design problems in the thermal management of high-frequency high-heat-flux micro-electronic components and in the ultra-short pulse laser micromachining.

飞秒、纳米时/空尺度下热输运过程具有强烈的非平衡特征，是目前热物理界乃至物理界迫切需要解决的最前沿难题之一。本课题以实验为主导，理论分析与数值模拟为支撑，系统研究飞秒时间尺度下多载能粒子热输运机理和纳米空间尺度下材料内部、界面的热输运特性。主要工作包括：建立双波长飞秒激光抽运探测系统，大幅（3个数量级）提高测量精度，解决常规单波长系统中信噪比过低的难题；并结合近场光学系统，同时实现飞秒、纳米时/空分辨的动态热输运特性测量，揭示固-固界面热整流现象以及界面热阻受尺度、结构影响的规律；采用求解BTE的方法分别对多载能粒子系统的各亚系统进行模拟，引入并实验获得亚系统之间相互作用的弛豫时间，揭示多载能粒子系统热输运过程的物理本质。本课题可推进飞秒、纳米时/空尺度下热输运理论框架的完善，为解决高频高热流微电子器件热管理及超短脉冲激光微加工等过程中的热设计问题提供科学依据。

飞秒、纳米时/空尺度下热输运过程具有强烈的非平衡特征，是目前热物理界乃至物理界迫切需要解决的最前沿难题之一。本项目以实验为主导，理论分析与数值模拟为支撑，系统研究飞秒时间尺度下多载能粒子热输运机理和纳米空间尺度下材料内部、界面的热输运特性。项目严格按照任务书执行，取得的主要成果包括：完成了现有飞秒激光抽运-探测热反射（TDTR）系统的双波长升级改进，信噪比提高3个数量级；建立了近场光学-TDTR热输运测量系统，实现了百飞秒时间/百纳米空间的超高分辨；拓展了3ω系统的应用范围，实现了各向异性薄膜3D热输运测试。实验上，获得了纳米薄膜、纳米固-固界面、固-液界面、纳米管/线阵列、微纳多孔材料、二维半导体材料等的热输运特性随尺度、结构、温度、应力的变化规律；理论上，建立了基于第一性原理、Boltzmann方程及经典分子动力学的热输运理论框架，实现了低维碳材料、热电转换材料、储能材料、高定向导热材料、非晶结构、纳米复合结构、纳米高分子链结构等的热、电输运特性的计算。实验与理论相结合，揭示了低维纳米材料、固-固和固-液界面热输运机理，提出了材料热导率及界面热导的调控方法；获得了各向异性材料、纳米多孔结构、管/线阵列内部及其与基底材料界面等的热输运特性；提出了改进的载能粒子超快动力学模型，准确描述了掺氮多晶碲化锌薄膜在超快激光作用下的非平衡热输运过程。本项目所取得的成果，可推进飞秒、纳米时/空尺度下热输运理论框架的完善，为解决高频高热流微电子器件热管理及超短脉冲激光微加工等过程中的热设计问题提供科学依据。.共发表学术期刊论文46篇，SCI检索40篇，其中影响因子7以上11篇，包括影响因子20以上2篇。出版著作章节3章。授权专利16项。培养博士生8名、硕士生9名。