Measurements of density and sticking probability of CN(X2Σ+) radicals by laser-induced fluorescence spectroscopy

CN(X2Σ+) radicals were produced by the decomposition of BrCN with the microwave discharge flow of Ar under the conditions of Ar pressure in the range of 0.40-0.70 Torr. The laser-induced fluorescence (LIF) spectra of the CN(A2Πi-X2Σ+), 4-0, 5-1, and 7-2 bands were observed, and their intensities were calibrated against Rayleigh-scattering intensity by Ar atoms, from which the CN(X2Σ+) radical density (nCN(X)) was determined as (0.67 ± 0.25) × 1018 to (4.42 ± 0.83) × 1018 m−3. Hydrogenated amorphous carbon nitride (a-CNx:H) films were formed by depositing the CN(X2Σ+) radicals on Si substrates in the same reaction system as LIF. The sticking probability (s) of the CN(X2Σ+) radicals onto the a-CNx:H films was determined by using nCN(X), the flow speed, and the weight (w) of a-CNx:H. The s value was determined as (6.4 ± 6.4) × 10−2 to (2.5 ± 1.2) × 10−2, where the errors are predominantly determined by those in nCN(X) and w. The procedure described in the present study will provide a methodology to determine the sticking probability of the precursor radicals of the film formation based on the gas-phase LIF spectroscopy.