高温高压下氮氢协同掺杂对{100}晶面生长宝石级金刚石的影响

在压力为5.5–6.2 GPa, 温度为1280–1450 ℃的条件下, 利用温度梯度法详细考察了氮氢协同掺杂对100晶面生长宝石级金刚石的影响. 实验结果表明伴随合成腔体内氮、氢浓度的升高, 合成条件明显升高, 金刚石生长V形区间上移; 晶体的红外光谱中与氮相关的吸收峰急剧增强, 氮含量可达2000 ppm, 同时位于2850 cm^-1和2920 cm^-1对应于 sp³杂化 C–H 键的对称伸缩振动和反对称伸缩振动的红外特征峰逐渐增强, 表明晶体中既有高的氮含量, 同时又含有氢. 对晶体进行电镜扫描发现, 氮氢协同掺杂对晶体形貌影响明显, 出现拉长的{111}面, 且晶体表面上有三角形生长纹理. 拉曼测试表明, 晶体的峰位向高频偏移、半峰宽变大, 说明氮、氢杂质的进入对晶体内部产生了应力. 本文成功地以{100}晶面为生长面合成出高氮含氢宝石级金刚石单晶, 在探究氮氢共存环境下金刚石生长特性的同时, 也可为理解天然金刚石的形成机理提供帮助.

Effects of nitrogen and hydrogen co-doped on {100}-oriented single diamond under high temperature and high pressure

As is well known, most natural diamonds usually contain not only aggregated nitrogen up to thousands of ppm but also hydrogen. Therefore, the studies of nitrogen and hydrogen impurities in a diamond are of interest for improving the physical properties of a diamond and solving the problems about natural diamond genesis. From this point of view, in this paper, we choose C₃N₆H₆ powders as a nitrogen and hydrogen source and select high-quality seed crystals with {100} facets as the growth facets. The effects of nitrogen and hydrogen co-doped on {100}-oriented single diamond in the NiMnCo-C system at pressures ranging from 5.5 GPa to 6.2 GPa and temperatures of 1280-1450 ℃ are investigated. Experimental results show that both pressure and temperature, which are the synthesis conditions, increase with the increases of nitrogen and hydrogen content in diamond-growth environment, and the V-shape region of diamond-forming moves up. From the obtained Fourier transform infrared spectra, we notice that there is a significant change of the nitrogen concentration in the synthesized diamond with increasing the nitrogen and hydrogen content in the diamond-growth environment. We calculate the nitrogen concentrations in those diamonds and the results indicate that the highest concentration of nitrogen is up to 2000 ppm. Meanwhile, we notice that the hydrogen associated infrared peaks of 2850 and 2920 cm^-1 are gradually enhanced, which shows that both nitrogen and hydrogen are successfully co-doped into the diamond. Scanning electron microscope micrographs show that the {111} face is elongated and has triangulated textures appearing on the surface with nitrogen and hydrogen co-doped into the diamond. This result indicates that the synergistic doping of nitrogen and hydrogen has a great influence on the morphology of {100}-oriented single diamond. From the obtained Raman spectra, we find a shift towards higher frequency of the Raman peak from 1330.23 cm^-1 to 1330.40 cm^-1 and the full width at half maximum increases from 3.12 cm^-1 to 4.66 cm^-1 with increasing the concentrations of nitrogen and hydrogen in diamond-growth environment. This is the first report about nitrogen and hydrogen co-doped on 100-oriented single diamond by far. This work can provide a new method to study the influences of nitrogen and hydrogen impurities on diamond synthesis and it will help us to further understand the genesis of natural diamond in the future.