In situ measurements of methane and acetylene concentrations in a CVD reactor by infrared spectroscopy

Measurements of the gas concentrations present during diamond growth can se rve to test the various proposed mechanisms of diamond film deposition. In particular, the relative concentration of acetylene and methane is crucial to understand their role in the deposition process, as they are the most pr obable diamond precursors. We obtained infrared spectra in situ under condi tions typical for diamond growth in a hot-filament chemical vapor depositio n (HFCVD) system. We also took standard absorbance FTIR measurements of met hane (v(3) (f(2)) at 3020 cm(-1) and v(4) (f(2)) at 1306 cm(-1)) and of ace tylene (v(3) (sigma(+)(u)) at 3287 cm(-1) and v(4) (612 cm(-1)) + v(5) at 1 328 cm(-1)) in the 5-50 Torr range in order to calculate their absorption c oefficients. These were then used in conjunction with the in situ infrared spectra to estimate the relative concentrations of acetylene and methane pr esent close to the filament in our HFCVD system. (C) 1999 Elsevier Science S.A. All rights reserved.