单晶金刚石缺陷表面Ta、C元素的互扩散反应机理及结合性能研究

The application of single crystal diamond in the field of high-tech has attracted intense interest of the world. However, the difficulty in welding between single crystal diamond and heterogeneous materials restricts its application. Surface metallization is one of the main method to solve the welding problem. Thus, it is very significant to obtain a well-adhered metallic layer. In this project, surface etching by co-bombardment of Ar+ and Fe particles via the double glow plasma surface alloying technique is proposed to promote diffusion of metallic element and increase surface roughness. Subsequently, well-adhered Ta metallic coatings with gradient-modified interfacial diffusion layer can be deposited on the etching surface. The microstructure in the near-surface of diamond and the diffusion-reaction behavior of the metallic element will be discussed as research objects. The evolutionary processes of the composition, structure, defect and roughness in single crystal diamond surface under Ar+ and Fe particles bombardment will be discussed for revealing the formation mechanism of surface defects. As well, the corresponding key influence factors will be formulated. Then, the interdiffusion and interaction behaviors of Ta and C element in the etched diamond surface will be investigated by combining numerical simulation with experimental research. As a result, the formation mechanism of the interfacial diffusion layer will be revealed. Finally, internal relationship among the gradient structure of diffusion layer, interfacial stress and adhesive strength will be explored synthetically to expose the adhesion enhancement mechanism of the diffusion layer. This work will provide a novel scheme for preparation of well-adhered metallic coating onto single crystal diamond and afford experimental and theoretical reference for the realization of reliable welding between single crystalline diamond and heterogeneous materials.

单晶金刚石在高技术领域的应用前景备受世人瞩目。但是，其与异质材料间存在焊接困难的问题，表面金属化处理是解决该问题的有效手段。为了提高金属层与金刚石之间的结合强度，本项目拟借助双辉等离子表面合金化技术，先通过Ar+和Fe金属粒子协同轰击单晶金刚石，获得具有较高缺陷密度和粗糙度的表面，随后在其上制备含有梯度结构界面扩散层、且与金刚石结合良好的Ta金属层。项目将以单晶金刚石近表面微结构、元素的扩散反应行为作为研究对象，阐明Ar+和Fe金属粒子协同轰击对单晶金刚石表面缺陷形成的作用机制及关键影响因素；澄清Ta和C元素在金刚石缺陷表层的互扩散反应机理；综合分析扩散层梯度结构-界面应力-结合强度之间的相关关系，揭示扩散层对结合强度的增强机制。本项目的研究结果将为单晶金刚石高结合强度金属化层的制备提供新方案，同时为实现其与异质材料高强度焊接提供实验和理论参考。

单晶金刚石拥有优异的物理化学性质，在高性能粒子探测器、金刚石高温半导体器件、微波输能窗口、超精密加工等高技术领域具有极其重要的应用前景。该材料在上述领域应用时，必须和其他材料进行焊接或封装处理。然而，金刚石很难被熔融金属或合金所浸润，可焊性极差，制约了它的应用。表面金属化处理是解决该问题的有效手段。本研究借助双辉等离子表面合金化技术，先通过Ar+轰击单晶金刚石，获得具有较高缺陷密度和粗糙度的表面，随后在其上制备了Ta金属化层和W-Ta复合金属层。结果表明：Ar+轰击在金刚石表面形成了包含空位和位错的缺陷层，促进了金属Ta、W和C在缺陷表面的互扩散反应，形成了扩散层和化学键合，提高了Ta金属化层和W-Ta金属化层与金刚石单晶间的结合强度。其中，Ta金属化钎焊接头的剪切强度最大值为118.7 MPa；W-Ta复合金属化钎焊接头的剪切强度最大值为190.9 MPa，该值比无金属化层的钎焊接头提升了~153%，比Ta金属化钎焊接头最大值提升了~61%。焊接剪切强度较高Ta金属化样品的剪切断裂失效形式主要为焊缝区的韧性断裂，而焊接剪切强度较高的W-Ta复合金属化样品剪切断裂失效形式主要以金刚石自身的脆性破裂为主，证实了这两种金属化层对金刚石-异质材料连接的有效作用。本项目的研究结果将为单晶金刚石表面高结合强度金属层制备提供新方案，同时为实现其与异质材料高强度连接提供必要的理论和实践依据。