Depth profiling light nuclei in single crystals: A combined nuclear reaction and RBS technique to minimize unwanted channeling effects

Abstract

The difficulties of depth profiling in single crystals, using MeV light ion beams, are discussed with particular emphasis on planar channeling effects. Depth profiling of 18O self-diffused crystals (corundum, Al 2O 3; forsterite, Mg 2SiO 4) via the 18 O(p, α) 15N nuclear reaction is used as an illustration. The effects on the alpha spectrum of channeling the proton beam along major axes and planes are described. There is a high probability that planar channeling effects distort the spectra strongly when the proton beam is incident on the crystals off axis but with any azimuthal orientation. A simple routine procedure is presented to minimize such unwanted effects, based on a combined use of nuclear reaction depth profiling and RBS techniques.