Mechanisms of diamond films deposition from MPACVD in methane-hydrogen and nitrogen mixtures

Abstract

The addition of nitrogen to the CH 4-H 2 gas mixture used for diamond growth by microwave plasma assisted chemical vapour deposition (MPACVD) strongly modifies the plasma reactivity and thus the deposition rate, the structure, and the physical properties of the films. It has been pointed out that nitrogen reduces the relative concentration of carbon deposition precursors such as CH and strongly enhances the etching process. When a diamond film is present in the centre of the plasma, a relatively high CN concentration could be detected in the discharge even after closing the gas line introducing methane in the gas flow. This can be considered as evidence of the etching of the diamond film by the plasma, resulting in the formation of CN radicals. The effect of nitrogen on the structure and quality of diamond films is discussed from the results of scanning electron microscopy and Raman spectroscopy.