Revisiting the gas flow rate effect on diamond films deposition with a new dome-shaped cavity type microwave plasma CVD reactor

Abstract With the newly built dome-shaped cavity type microwave plasma CVD reactor, the gas flow rate effect observed in diamond films deposition was reinvestigated. Experimentally, a maximum in diamond films growth rate was observed when the gas flow rate was set at an intermediate value. To explain the experimental results, a two-folded mechanism was taken into consideration, i.e., the catalytic effect of nitrogen impurity in enhancing diamond films deposition, and depletion of carbon containing species in diamond depositing environment. Experimental evidence has been collected by analyzing the diamond films and measuring optical emission spectra of the microwave plasma. It is shown that with the proposed mechanism, the experimental results could be explained, and at the same time, changes in morphology and quality of diamond films with the gas flow rate are discussed.