Molecular beam mass spectrometry studies of the gas-phase chemistry occurring during microwave plasma assisted chemical vapour deposition of diamond

摘要

A molecular beam mass spectrometer has been used for in-situ studies of the gas-phase composition during microwave plasma chemical vapour deposition of diamond, in a way that decouples the gas-phase reactions from those occurring near thesubstrate surface.The system has been used to examine the plasma composition for a variety of hydrocarbon precursor-in-H{sub}2 feedstock gas mixtures. Stable hydrocarbon species, and the methyl radical signal, were recorded and calibrated to give mole fractions of all thecarbon-containing species present at detectable levels. The plasma composition has been studied with varying chemical vapour deposition process parameters such as applied microwave power, and concentration of hydrocarbon in the feed gas. Molecular beammass spectrometry has also been used to determine the plasma gas temperature, yielding results in good agreement with non-invasive methods.