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

Abstract

Abstract Measurements of the gas concentrations present during diamond growth can serve 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 probable diamond precursors. We obtained infrared spectra in situ under conditions typical for diamond growth in a hot-filament chemical vapor deposition (HFCVD) system. We also took standard absorbance FTIR measurements of methane ( ν 3 (f 2 ) at 3020 cm −1 and ν 4 (f 2 ) at 1306 cm −1 ) and of acetylene ( ν 3 ( σ u + ) at 3287 cm −1 and ν 4 (612 cm −1 )+ ν 5 at 1328 cm −1 ) in the 5–50 Torr range in order to calculate their absorption coefficients. These were then used in conjunction with the in situ infrared spectra to estimate the relative concentrations of acetylene and methane present close to the filament in our HFCVD system.