铜/碳化物/金刚石纳米多层结构的微尺度传热机制

Diamond particles dispersed metal matrix composites are ideal thermal conducting materials for heat dissipation of powered devices like semiconductor lasers and large-scale integrated circuits. The key to enhancing thermal conductivity of the composites is the formation of interfacial carbide layer between metal matrix and diamond reinforcement. The effects of carbide interfacial layer thickness and acoustic impedance mismatch among metal matrix, carbide and diamond on the interfacial thermal conductance are critical issues in the field. In this proposal, magnetron sputtering is utilized to deposit copper/modifying metal bi-layer films onto a single-crystalline diamond substrate, and the modifying metal and diamond reacts to form carbides after subsequent heat treatment. Femtosecond laser thermoreflectance technique is applied to directly measure the interfacial thermal conductance in the multilayers of copper/carbide/diamond obtained. Through a series of nanometer films deposition, the size effect of interfacial layer thickness on interfacial thermal conductance is clarified. With the selection of various types of carbides, the role of acoustic impedance mismatch in phonon transport along the multilayers is verified. The finding will provide scientific basis for interfacial design and processing of metal/diamond composites with enhanced thermal conductivity, and will offer guideline for investigation of interfacial thermal conductance in micron/nano-sized structures such as thermal interface materials and nanoparticle-assisted hyperthermia therapy.

金刚石颗粒分散金属基复合材料是解决半导体激光器、大规模集成电路等高功率器件散热问题的理想导热材料，在金属与金刚石之间构筑碳化物界面层是有效提高复合材料热导率的关键。碳化物界面层厚度以及金属基体、碳化物、金刚石之间声阻抗匹配对界面热导的影响规律是本领域的重要科学问题。本项目利用磁控溅射方法在单晶金刚石基片上沉积铜/改性金属双层膜，通过热处理使改性金属与金刚石反应形成碳化物，利用飞秒激光热反射法直接测量铜/碳化物/金刚石多层结构的界面热导。通过沉积一系列不同厚度的纳米尺寸膜，阐明界面层厚度的尺寸效应；选择不同种类碳化物，揭示界面层声阻抗匹配对声子传输的作用机制。研究结果为高导热金属/金刚石复合材料界面设计与制备提供科学依据，并为热界面材料、纳米粒子辅助热疗等微纳结构界面热导研究提供理论参考。

高导热Cu/diamond复合材料是实现半导体激光器、有源相控阵雷达、大规模集成电路等高功率器件高效散热的理想材料，Cu/diamond界面传热机理是所涉及的关键科学问题。目前通过物理模型计算或解析模型倒推获得Cu/diamond界面热导，研究结果存在较大偏差和不确定性。本项目利用磁控溅射在diamond基板上沉积Cu膜，通过俄歇电子能谱和透射电镜表征界面结构，利用飞秒激光热反射法直接测量Cu/diamond界面热导，解决Cu/diamond复合材料中界面热导无法测量的难题。通过构筑Cu/interlayer/diamond “三明治”结构，阐明中间层种类、结晶度、晶粒尺寸、厚度对Cu/diamond界面热导的影响规律，提出中间层声学性能判定参数，建立Cu/diamond中间层设计准则，分别在第IV和VI副族选取代表性元素Ti和Mo、Cr进行实验验证，揭示两类不同金属中间层碳化过程对Cu/diamond界面热导的作用机制。研究表明，Cu/Ti/diamond界面热导在Ti中间层完全碳化时达到最高值，TiC中间层厚度为10 nm时界面热导值为93 MW/mK2；而Cu/Mo/diamond和Cu/Cr/diamond界面热导在Mo和Cr中间层少量碳化时分别达到最高值132 MW/mK2和168 MW/mK2，上述差异与中间层声学性能及金属碳化前后热导率变化密切相关。本项目阐明了Cu/diamond界面热导的影响规律及其调控机制，研究结果有助于理解两侧材料声学性能差异悬殊界面传热机理，为高导热Cu/diamond复合材料的界面设计提供了理论依据。本项目发表论文13篇，申请专利5项，培养研究生7名。