EFFECTS OF NOBLE-GASES ON DIAMOND DEPOSITION FROM METHANE-HYDROGEN MICROWAVE PLASMAS

The deposition of diamond films by microwave plasmas has been studied in gaseous mixtures of methane, hydrogen, and noble gases. Plasma diagnostic results are compared with growth rates and Raman spectra of the films. The noble gases, which influence the degree of excitation or reactant molecules by energy transfer or charge transfer from their excited and ionic states, are active in the deposition process by inducing additional ion-molecule and excited atom-molecule reactions. As a result, enhanced deposition rates have been observed. Small oxygen additions along with the noble gases can suppress the formation of nondiamond carbon phases, leading to an effective way to rapidly deposit diamond films at high methane concentrations while still retaining minimal nondiamond carbon components in the films.