Evaluation of non-resonant background in hydrogen depth profiling via 1H( 15N,αγ) 12C nuclear reaction analysis near 13.35 MeV

Abstract

Background γ-signals arising from interaction of H in surface layers of the target with the off-resonance cross-section of the 1H( 15N,αγ) 12C reaction affect H concentration measurements with resonant nuclear reaction analysis (r-NRA) particularly at 15N energies near the 13.35 MeV resonance. This non-resonant background in relation to the on-resonance intensity is determined in the energy range from 6.4 to 13.7 MeV with a thin hydrogenated silicon nitride film on a H-free Si(1 0 0) substrate. The results independently verify earlier evaluations of the off-resonant cross-section, but point out that the γ-detector position relative to the incident ion beam must be accounted for. Based on an estimation of the near-surface H concentration distribution by simulating the yield curves, furthermore a general procedure is proposed to extract the resonant signal related to surface-H from the total γ-yield near 13.35 MeV.