金刚石以高导热率、强抗辐射性、高的电子迁移率等优异性能, 成为辐射探测器最合适的材料之一。探测器级的金刚石要求具有极低的杂质含量及位错密度等, 然而实际过程中同时实现杂质和位错的控制十分困难。本研究采用微波等离子体化学气相沉积(MPCVD)法, 通过前期的参数优化, 在最佳生长温度780 ℃、最佳甲烷浓度5%条件下, 在两个高质量高温高压(HPHT)金刚石衬底样品上进行了MPCVD金刚石生长, 并对衬底和生长层的氮杂质含量与缺陷结构进行了综合表征与分析。电子顺磁共振谱结果表明, 相比两个HPHT衬底样品的氮杂质原子百分数分别为7.1×10-6%和4.04×10-6%, MPCVD生长层的氮杂质原子百分数明显减少, 分别为2.1×10-7%和5×10-8%。由X射线摇摆曲线和白光形貌术测试结果发现, 尽管MPCVD生长过程中引入了部分位错, 使生长层应力增加, 畸变区域较多, 但总体位错与高质量衬底为同一数量级。本研究制备的高纯单晶金刚石有望应用于核辐射探测及半导体领域。

With its excellent properties such as high thermal conductivity, strong radiation resistance and high electron mobility, diamond has become one of the most suitable materials for radiation detectors. Detector-grade diamond requires low impurity content, low dislocation density and other defects. However, it is very difficult to keep low impurities and low dislocations simultaneously in the actual crystal growth process. In this study, microwave plasma chemical vapor deposition (MPCVD) method was used to grow diamond layer on two high-quality HPHT diamond substrates with the previously optimized process conditions. The nitrogen impurity content and structure of the HPHT substrate and growth layer were characterized and analyzed. The results show that, the content of nitrogen impurity on two HPHT substrates are 7.1×10-6% and 4.04×10-8%, respectively, whereas in their epitaxial diamond layers, the nitrogen impurity content are 2.1×10-7% and 5×10-8%, respectively. The full width at half-maximum of the rocking curve shows that the dislocation density of the MPCVD growth layer is comparable to the HPHT substrate, though some dislocations were introduced into the MPCVD growth layer, which increases the stress. Overall, the dislocations in the HPHT substrate and epitaxial layer of single crystal diamond are in the same order of magnitude. The high-purity single crystal diamond prepared in this work may be used in nuclear radiation detection and semiconductor fields.