添加Fe(C5H5)2合成氢掺杂金刚石大单晶及其表征

在Ni₇₀Mn₂₅Co₅-C体系中添加含氢化合物Fe(C₅H₅)₂作为新型氢源, 利用温度梯度法, 在压力为5.5-6.0 GPa、温度为1280-1400 ℃的条件下, 成功合成出氢掺杂的宝石级金刚石大单晶. 通过傅里叶显微红外光谱发现, 随着Fe(C₅H₅)₂添加量的增加, 合成晶体中与氢相关的对应于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2850和2920 cm^-1逐渐增强, 而晶体中氮含量却逐渐减少. 通过合成晶体的拉曼光谱分析发现, 金刚石的拉曼峰伴随Fe(C₅H₅)₂的添加向高频偏移, 这表明氢的进入在金刚石内部产生了压应力. 观察扫描电子显微镜图像发现, 在低含量Fe(C₅H₅)₂添加时晶体表面平滑, 而高含量添加时晶体表面缺陷增多, 且呈现出气孔状. 使用新的添加剂Fe(C₅H₅)₂作为氢源, 合成出含氢宝石级金刚石单晶, 丰富了金刚石单晶中对氢的研究内容, 也可为理解天然金刚石的形成机理提供帮助.

Crystal growth and characterization of hydrogen-doped single diamond with Fe(C5H5)2 additive

In this paper, a series of high-quality hydrogen-doped diamonds is successfully synthesized in Ni₇₀Mn₂₅Co₅-C system by using Fe(C₅H₅)₂ as hydrogen source at pressures ranging from 5.5 GPa to 6.0 GPa and temperatures of 1280-1400 ℃. We find that both pressure and temperature conditions strengthen with adding the Fe(C₅H₅)₂. Scanning electron microscope micrographs show that the obtained diamonds at low levels of Fe(C₅H₅)₂ additive have smooth surfaces. However, many defects are found and some pores appear on the diamond surface with increasing the Fe(C₅H₅)₂ additive in the system. From the obtained Fourier transform infrared (IR) spectrum, we notice that there is no significant change of nitrogen concentration in the synthesized diamond with the Fe(C₅H₅)₂ additive lower than 0.3 wt%, while the nitrogen concentration gradually decreases with the further increase of Fe(C₅H₅)₂ additive. In the system with 0.5 wt% Fe(C₅H₅)₂ additive, the nitrogen concentration in synthesized diamond is only half that of system without Fe(C₅H₅)₂ additive. Meanwhile, the hydrogen associated IR peaks of 2850 cm^-1 and 2920 cm^-1 are gradually enhanced with the increase of Fe(C₅H₅)₂ additive in the system, indicating that most of the hydrogen atoms in the synthesized diamond are incorporated into the crystal structure as sp³-CH₂-symmetric (2850 cm^-1) and sp³ CH₂-antisymmetric (2920 cm^-1) vibrations. From the obtained Raman spectrum, we find the incorporation of hydrogen impurity leads to a significant shift of the Raman peak towards higher frequencies from 1333.90 cm^-1 to 1334.42 cm^-1 with increasing the concentration of Fe(C₅H₅)₂ additive from 0.1 wt% to 0.5 wt%, thereby giving rise to some compressive stress in the diamond crystal lattice. This is the first time that the gem-grade hydrogen-doped diamond single crystal, with size up to 3.5 mm has been successfully synthesized by using new hydrogen source Fe(C₅H₅)₂ additive. We believe that our work can provide a new method to study the influence of hydrogen impurity on diamond synthesis and it will help us to further understand the genesis of natural diamond in the future.