添加Fe(C5H5)2合成氢掺杂金刚石大单晶及其表征

Crystal growth and characterization of hydrogen-doped single diamond with Fe(C_5H_5)_2 additive

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°C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.

In this paper, a series of high-quality hydrogen-doped diamonds is successfully synthesized in NiToMn25Co5-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 sp^3-CH2-symmetric （2850 cm^-1） and sp^3 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（CsHs）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.