The effect of phosphorus and nitrogen co-doped on the synthesis of diamond at high pressure and high temperature

The synthesis of phosphorus and nitrogen co-doped diamond is investigated in the NiMnCo-C system by adding P3N5 or carbonyl iron powders mixed with phosphorus powders under high pressure and high temperature. Experimental results show that the color distribution in diamond crystals with low concentration of P3N5 additive is not uniform. The color becomes deep green with the increase of P3N5 additive. The optical images and FTIR spectra reveal that the nitrogen atoms are more easily incorporated via {111} than {100} in the same conditions. In addition, the result of FTIR spectra of synthesized diamond indicates that the hydrogen atoms in the form of sp3-CH2- are more likely to enter the diamond lattice in the P/N co-doped system, compared with the single N-doped system. The absorption peak at 3107 cm− 1 attributed to vibration of H-related point defects (sp2-CHCH-) is observed in diamonds, which is often found in natural diamonds. The Raman shifting to lower frequency and FWHM value becoming wider are due to the doping of phosphorus atoms.