Optimal parameter(s) for the synthesis of nitrogen-vacancy (NV) centres in polycrystalline diamonds at low pressure

Abstract

Nitrogen-vacancy (NV) centres in diamonds are emerging quantum materials having applications in quantum computing and magnetic field sensing. The ability to synthesize polycrystalline diamond films from chemical vapour deposition technique offers a possibility to grow cheap diamonds with NV centres over large areas. Till date, extensive studies have not been carried out to understand the influence of nitrogen flow rate on the formation of NV centres in polycrystalline diamonds. In this study, we investigate the effect of nitrogen flow rate on the morphology, optical, and electrical properties of polycrystalline diamonds deposited at low pressure. Several samples were prepared in different nitrogen flow regimes using the microwave plasma chemical vapour deposition (MPCVD) technique. The films were characterized using Raman spectroscopy and scanning electron microscopy (SEM). The I–V characteristics of the samples were measured using a point contact method at room temperature. Results obtained showed the formation of both neutral and negatively charged NV centres at an optimum nitrogen flow rate of 10 sccm. An increase in nitrogen flow rate led to a decrease in the electrical resistivity of the films. Furthermore, nitrogen flow rates greater than 20 sccm results to a decrease in the reflectance spectra of samples and a depreciation in the crystalline quality of films. This study is important in benchmarking an optimal parameter space for the growth of nitrogen doped polycrystalline diamonds suitable for sensing applications.