Gas phase energetics of CN radicals in radio frequency discharges: influence on surface reaction probability during deposition of carbon nitride films.

The CN radical has been implicated as an important contributor to the plasma deposition of amorphous carbon nitride. Here, laser-induced fluorescence and optical emission spectroscopy were used to explore in greater detail the gas phase energetics of CN in CH(3)CN, BrCN, and CH(4)/N(2) plasmas. Measurements of CN internal temperatures from these systems yield rotational temperatures well above 300 K, with notably higher ones for CN formed in BrCN plasmas, and vibrational temperatures of 4500-6000 K in all three systems. The data agree with the results of literature photodissociation experiments, and extension of those results to the plasma systems studied here provides insight into both the mechanisms for CN formation as well as the disposal of energy during fragmentation of the parent molecules. The internal energies of these species may influence their surface behavior; this issue is discussed in the context of previous work from our lab as well as others. The apparent trends not only offer a valuable perspective on the chemical dynamics of CN during the plasma deposition of a-CN(x) films but are also suggestive of a more general relationship between the energetics of plasma species and their behavior at surfaces.