单晶金刚石生长过程中的应力研究

使用实验室自制的10 kW微波等离子体设备，研究单晶金刚石不同生长阶段的应力表现形式。通过等离子状态参数模拟和发射光谱诊断，研究不同生长阶段几种主要基团的分布和含量；通过扫描电子显微镜和拉曼光谱仪对金刚石的表面形貌和结晶质量进行表征。在整个生长阶段，单晶金刚石边缘区域的电场密度和等离子密度逐渐增强，在功率一定的情况下，中间区域的等离子密度会削弱，并且随着时间延长厚度增加，等离子体状态参数差别越明显，导致单晶金刚石生长模式发生改变，表面的层状生长改为梯度生长，边缘的多取向竞争生长失衡，取向杂乱的多晶在边缘处产生，在这种生长模式影响下，单晶金刚石的生长应力和热应力交替影响其生长状态。结果导致在生长初期，单晶金刚石应力较小且分布均匀，随着时间延长厚度增加，单晶金刚石受缺陷导致的生长应力和温差导致的热应力影响递增，产生裂纹。

Study on Stress of Single Crystal Diamond at Different Growth Stages

The stress of single crystal diamond at different growth stages was studied using a laboratory-made 10 kW microwave plasma device. The distribution and contents of several major groups at different growth stages were analyzed through plasma state parameter simulation and emission spectrum diagnosis. The surface morphology and crystal quality of diamond were characterized by scanning electron microscopy and Raman spectroscopy. The electric field density and plasma density in the edge region of the single crystal diamond gradually increase throughout the entire growth stage. At a certain power，the plasma density in the central region weakens. In addition，as the thickness increases，the difference between the plasma state parameters becomes more significant，resulting in the change of single crystal diamond growth pattern. The layered growth on the surface of the crystal diamond changes to gradient growth. The multi-directional competitive growth at the edges becomes imbalanced，and the polycrystalline with disordered orientation is produced at the edges. Under the influence of this growth pattern，the growth stress and thermal stress of single crystal diamond alternately affect its growth state. As a result，at the initial growth stage，the stress of single crystal diamond is small and evenly distributed. With the increase of growth time and thickness，the growth stress caused by defects and the thermal stress induced by temperature difference have significant influences on the single crystal diamond，resulting in the generation of cracks in the diamond.