Characterization of trace nickel in synthetic diamond and its relationship to the abundance of substitutional nitrogen

Abstract

Atomic abundances of nickel and nitrogen in artificial diamond crystals grown from metallic solvents under high pressure were studied by X‐ray fluorescence (XRF) analysis and electron paramagnetic resonance (EPR) spectra, respectively. For dissolved nickel, electronic configurations were investigated with EPR spectra and the amount of substitutional Ni− center (Nis−) was determined. For diamond crystals grown from nickel‐based solvents, the addition of 2% Ti (nitrogen getter) into the nickel solvent gave rise to the substantial decrease of Nis− and N contents in the grown diamonds from 50 to 0.15 atom. ppm and 270 to 0.29 atom. ppm, respectively. On the contrary, total amount of nickel exhibited small decrease from 317 to 227 atom. ppm. This result implies the close relationship between the abundances of Nis− and those of N. Furthermore, nitrogen‐reduced diamond crystal was grown from degassed carbon source without using nitrogen getter. The nitrogen‐reduced diamond showed the decrease of N from 64.7 to 14.9 atom. ppm in addition to the decrease of Nis− from 14.9 to 4.9 atom. ppm which means that Nis− abundance correlated to N abundance. Electron transfer from N to Nis− in the diamond crystal was speculated from our experimental results for a possible physical mechanism of the abundance correlation.