种晶类型对微波等离子体CVD法合成单晶体金刚石生长质量的影响

The influence of seed crystals on the quality of single-crystal diamond produced by a microwave plasma CVD method

采用辽宁瓦房店及山东蒙阴产天然金刚石、俄罗斯高温高压(HPHT)金刚石以及美国Element Six公司CVD金刚石作为种晶,进行红外光谱、激光拉曼光谱、光致发光光谱、XRD摇摆曲线以及原子力显微形貌测试,并选取三类样品各一颗,在相同条件下进行生长实验。测试结果表明,天然金刚石种晶均为Ia AB型,定向性好,其内应力及结晶质量差异较大;而HPHT以及CVD金刚石种晶分别为Ib型和IIa型,其生长面与(100)晶向均存在1~2.5度偏差,但晶体结构较天然金刚石好,且内应力及结晶质量差异较小,更加适合作为MPCVD法合成金刚石单晶的种晶。对生长后样品进行了高分辨率激光拉曼光谱测试,并使用光学显微镜及原子力显微镜对样品表面形貌进行了观察。结果表明,在碳氢氮生长体系中,辽宁瓦房店或山东蒙阴产Ia AB型天然金刚石种晶由于晶格匹配性较差,容易沉积多晶金刚石,且伴随有微晶石墨和非晶质碳成分;而使用俄罗斯产Ib型HPHT种晶以及美国Element Six产IIa型CVD种晶均能得到优质的CVD金刚石生长层;与HPHT种晶相比,使用CVD种晶得到金刚石生长层的拉曼位移半高宽更窄,非金刚石碳杂质含量更低,结晶质量更好。

Natural diamonds from Liaoning and Shandong provinces, a HPHT diamond from Russia and a CVD diamond from theElement Six Company in America were selected as seed crystals for the growth of diamonds using the microwave plasma CVD meth-od. The seeds and grown diamonds were characterized by FTIR, Raman spectroscopy, photoluminescence spectroscopy, XRD and AFM. Results indicate that the natural diamonds are type IaAB with a unique orientation and great differences in internal stress and crystalline quality. The HPHT and CVD diamonds are type Ib and type IIa, respectively, with an angular deviation of 1 -2. 5 degrees and better crystal structure, and are more suitable for the CVD growth of single-crystal diamonds with little variation in internal stress and crystalline quality. The diamond layers grown on the natural IaAB seed crystals from Liaoning and Shandong provinces are poly-crystalline with a serious lattice mismatch and impurities of microcrystalline graphite and amorphous carbon while the diamond layers grown on the HPHT type Ib seed crystal from Russia and the CVD type IIa seed crystal from the Element Six Company are both of high quality. Moreover, the diamond layer grown on the CVD seed crystal has a narrower FWHM of the Raman peaks and a lower amount of non-diamond carbon impurity, indicating that it has a better crystalline quality than the diamond layer grown on the HPHT seed crystal.