Effect of the solvent-catalyst composition on diamond crystallization in the Mg-Ge-C system

• Published in: Diamond and related materials 2018-10, Vol.89, p.1-9
• Main Authors: Palyanov, Yuri N., Kupriyanov, Igor N., Borzdov, Yuri M., Nechaev, Denis V.
• Format: Article
• Language: English
• Subjects: Catalysis; Catalysts; Composition effects; Correlation analysis; Crystallization; Crystals; Defect characterization; Diamonds; Germanium; High pressure high temperature (HPHT); Impurities; Lattice vacancies; Luminescence; Nucleation; Optical properties; Photoluminescence; Solvent-catalysts; Solvents; Synthetic diamond; Vacancies
• ISSN: 0925-9635; 1879-0062
• DOI: 10.1016/j.diamond.2018.08.002

Crystallization of diamond in the Mg-Ge-C system has been studied at 7.5 GPa and 1800 °C with the catalyst composition ranging from pure Mg to pure Ge. It is found that with increasing Ge content of the solvent-catalyst, the degree of graphite-to-diamond conversion gradually decreases from 92 to 16%, which is a consequence of the low solubility of carbon in the germanium melt. A decrease in the Mg/Ge ratio leads to a change in the diamond growth form from cube to octahedron and a drastic increase in the number of diamond nucleation centers. The spectral properties of the crystallized diamonds are studied by photoluminescence techniques. The correlations between the Ge content of the Mg-Ge-C system and the luminescence characteristics of the diamond crystals caused by the germanium-vacancy, silicon-vacancy, and nitrogen-vacancy optical centers are established. The results obtained in this study demonstrate that by changing the catalyst composition in the Mg-Ge-C system, it is possible to control the design of the diamond crystals and synthesize isometric, pyramidal, prismatic or needle-like crystals containing Ge-V centers. [Display omitted] •Effect of Mg/Ge ratio on diamond crystallization in the Mg-Ge-C system is established.•Isometric, pyramidal, prismatic and needle-like diamond crystals are synthesized.•Spectral properties of the crystals are determined by Ge-V, Si-V and N-V centers.