Measurements of density and sticking probability of CN(X 2Σ +) radicals by laser-induced fluorescence spectroscopy

Abstract

CN(X 2Σ +) 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(A 2Π i –X 2Σ +), 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(X 2Σ +) radical density ( n CN(X)) was determined as (0.67 ± 0.25) × 10 18 to (4.42 ± 0.83) × 10 18 m −3. Hydrogenated amorphous carbon nitride (a-CN x :H) films were formed by depositing the CN(X 2Σ +) radicals on Si substrates in the same reaction system as LIF. The sticking probability ( s) of the CN(X 2Σ +) radicals onto the a-CN x :H films was determined by using n CN(X), the flow speed, and the weight ( w ) of a-CN x :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 n CN(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.