Growth chemistry for the fabrication of designer diamonds for high pressure research

Abstract

We report our observations on the catalytic effect of nitrogen in the growth of diamond on top of a diamond anvil substrate by microwave plasma chemical vapor deposition technique. The diamond deposition experiments were carried out by varying the nitrogen content in the range 0–3500 ppm in a standard hydrogen/methane/oxygen plasma. We employ isotopically enriched C-13 methane gas as the source of carbon in the plasma to clearly distinguish the grown diamond layer from the underlying substrate using Raman spectroscopy. The measured diamond growth rate shows a sharp peak at a nitrogen content of 1000 ppm in our growth experiments carried out at 1212°C and atomic force microscopy reveals a dramatic change in surface morphology. Thermodynamic calculations of the plasma show that this growth enhancement could be the result of a competition between the CN and CH3 radicals in the plasma. Finally, we show an application of this ‘unique chemistry’ by synthesizing several designer diamonds with embedded sensors for high-pressure materials research experiments.