Knowledge Bank

The intracavity laser spectroscopic (ILS) technique provides a very sensitive method that can be used to determine the number density of gas phase intermediate species associated with radiofrequency (RF) plasma discharges, It has been used to obtain the concentration and spatial distribution of excited state (n=2) atomic hydrogen ($H\ast$) observed in RF plasmas of hydrogen and in hydrocarbon RF plasmas used in depositing diamond-like carbon films. The $H\ast$ is observed via the $H\ast$ profiles. Because of the high sensitivity of the ILS method, the $H\ast$ spectra can be obtained at very high spectral resolution. This enables study of the $H\ast$ profiles in considerable detail, Optical emission spectroscopy is used to examine emitting species such as excited state molecular hydrogen ($H2\ast$) and $H\ast$. These in situ provide diagnostic data as sell as information about the deposition mechanism.