金属纳米薄膜的非傅立叶导热机制及其对界面传热的影响

As the feature size of the electronic device continues to decrease and approach the mean free path, the non-Fourier heat transport will play an important role in nanomaterials and the related interfaces, which is one of the hot topics nowadays. The project tends to investigate the mechanism of the non-Fourier heat transport in metallic nanofilms and its impact on the interfacial heat transport. The main research is described as follows: A scanning probe microscope is designed and fabricated to quantitatively measure the temperature profile with nanometer spatial resolution; The whole system is comprised of the mechanical and optical-mechanical feedback control components, and the microfabricated cantilever embedded with a temperature and heat-flux sensor; By measuring the electrical and thermal properties, the effect of the surface scattering on the ballistic transport in metallic nanofilms under different restrict dimensions is investigated, and the relationship between the restrict dimension, mean free path and the physical properties is clarified; Combined with the temperature distribution, thermal and electrical properties of nanofilms and substrate, the temperature difference between two sides of the interface is calculated, and the influence of the key factors such as the heating power and the restrict dimension on the interfacial heat transport is systematically studied; With the framework of first principle method, molecular dynamics and Green function, the effect of heat flux, interfacial morphology and dimension on the phonon transmission coefficient and the thermal resistance is analyzed to gain a deep insight into the heat transport at the interfaces, thus providing a theoretical and technical support for manipulating the interfacial heat transport.

随着特征尺寸进一步减小，非傅立叶导热过程对纳米材料本身和界面传热都具有重要影响，是国内外研究热点。项目拟结合实验和理论计算，研究金属纳米薄膜的非傅立叶导热机制及其对界面传热的影响规律。主要研究涉及：设计加工扫描探针显微镜的镜体结构和光电控制反馈系统，制备集成了温度和热流测量的悬架热探针，实现异质材料表面的纳米分辨率温度测量；测量不同维度受限的金属纳米薄膜的热电性质，研究表面散射对弹道输运过程的影响，给出薄膜热电性质与不同维度受限尺寸和载流子平均自由程间的内在联系；结合纳米器件表面温度分布以及金属纳米薄膜和基底的热电性质，得到界面两侧温度，进而研究功率密度、受限尺寸等关键因素对界面传热的影响规律；结合第一性原理、分子动力学和格林函数法，分析热流密度、表面粗糙度、界面尺寸等因素对声子投射系数及界面热阻的影响，获得界面能量传递过程的清晰图像，为有效调控界面传热提供依据。

随着微纳米电子器件的特征尺度进一步减小，集成度不断提高，功率密度增大，非傅立叶导热对于理解微纳米尺度热输运现象显得尤为重要，因此受到国内外研究者的广泛关注。在实验研究方面，项目克服了单侧支撑的悬架结构刚度不足的问题，在悬臂边沿设计了加强肋，刚度提高一个数量级，成功设计并加工了悬架微结构；采用化学蚀刻法加工了纳米分辨率的T形热探针，搭建了扫描探针显微镜实验系统，并实现了异质结构表面的形貌测量；测量了包括Ag，Pt等单晶和多晶金属纳米线的热电输运性质的尺度效应，获得了预测金属纳米线、金属纳米薄膜热导率随结构特征尺寸和温度变化的理论预测模型；开发了交叉微米线结构，在安培力下实现了真空环境下两根交叉微米线接触电阻和接触热阻的原位调控与同时测量，成功区分了接触电阻中麦克斯韦电阻和Sharvin电阻的不同贡献，并证明了Wiedemann-Franz定律对金属接触处于弹道/扩散输运过程仍然适用；在准确测量接触热阻的基础上，采用交叉微米线结构测量了不同合金微米线的热电性质，提高了测量准确性；设计加工了金属钨/石墨烯多层薄膜结构，采用飞秒激光热反射试验系统，研究了石墨烯界面对超快热输运过程以及离子辐照多层薄膜结构、热力性质的影响。在理论研究方面，结合第一性原理计算，采用原子格林函数方法研究了界面尺寸对铜/单层石墨烯界面透射系数和界面热导的影响；结合麦克斯韦电磁场理论，更新了热输运方程，用于描述飞秒激光热加工中的非傅立叶导热过程；结合运动界面的粘滑理论，采用有限差分和分子动力学模拟，研究了运动界面中非平衡态声子对能量耗散过程的影响。研发用于微纳米尺度材料热输运性质的实验系统，掌握纳米材料本身的非傅立叶热输运性质，以及纳米接触界面的能量传递规律，对微纳米电子器件设计、热管理等都具有重要意义。