28Si(p,p′γ)28Si nuclear reaction in the detection and depth profiling of Si in materials.

A proton induced γ-ray emission method for depth profiling Si in the surface regions of materials is described. The method utilizes the resonance at 3098 keV in 28Si(p,p′γ)28Si nuclear reaction and involves the measurement of the characteristic 1778 keV γ-rays. The yield curves of the γ-rays are constructed in 3.0–3.8 MeV proton energy region using different Si targets to determine the analytical capabilities of the resonance. The resonance has a width of ∼12 keV (depth resolution: ∼600 nm in Si), a large probing depth (∼11 μm in Si) and a detection sensitivity of ∼0.7 at.%. A procedure for quantification based on Breit-Wigner formula that encompasses corrections for off-resonance cross-sections is also outlined. Depth profiling of Si in silicon carbide crystals and also in a silicon nitride film with <10% combined uncertainty shows that this method is well suited for probing Si in silicon bearing materials. [ABSTRACT FROM AUTHOR]