Effect of FeS doping on large diamond synthesis in FeNi–C system**Project supported by the National Natural Science Foundation of China (Grant No. 51772120), the Project for Key Science and Technology Research of Henan Province, China (Grant Nos. 162102210275 and 172102210283), the Key Scientific Research Project in Colleges and Universities of Henan Province, China (Grant Nos. 18A430017 and 17A430020), and the

Abstract

The large single-crystal diamond with FeS doping along the (111) face is synthesized from the FeNi–C system by the temperature gradient method (TGM) under high-pressure and high-temperature (HPHT). The effects of different FeS additive content on the shape, color, and quality of diamond are investigated. It is found that the (111) face of diamond is dominated and the (100) face of diamond disappears gradually with the increase of the FeS content. At the same time, the color of the diamond crystal changes from light yellow to gray-green and even gray-yellow. The stripes and pits corrosion on the diamond surface are observed to turn worse. The effects of FeS doping on the shape and surface morphology of diamond crystal are explained by the number of hang bonds in different surfaces of diamond. It can be shown from the test results of the Fourier transform infrared (FTIR) spectrum that there exists an S element in the obtained diamond. The N element content values in different additive amounts of diamond are calculated. The XPS spectrum results demonstrate that our obtained diamond contains S elements that exist in S–C and S–C–O forms in a diamond lattice. This work contributes to the further understanding and research of FeS-doped large single-crystal diamond characterization.