Applications of Nuclear Techniques and Microscopy to Surface Analysis of Materials

Abstract

The importance of surface analysis of materials has been increasing. The available techniques are complementary. Nuclear techniques, which are non-destructive, provide analysis for a few microns near the surface. Using low energy ion beams of a few MeV, applications have been made to several areas. Nuclear reactions and elastic scattering are the more precise nuclear techniques for obtaining absolute values of concentrations in surface analysis. Nuclear reactions provide, not only high sensitivities for detection of light elements in heavy substrates, but also discrimination of isotopes. We consider the “energy analysis method”, where a spectrum is acquired of ions from the target for a single energy of an incident ion beam. The spectrum inherently contains target composition and concentration profile information. A computational procedure has been developed for predicting such energy spectra, where elastic scattering is a particular and important case. The model mainly accounts for: target parameters, such as composition and concentration profiles; energy spread of the incident ion beam; geometric factors and target rotation; stopping power; differential cross section; energy straggling; detector resolution. An option permits inclusion of effects such as: multiple scattering; incident beam size and angular divergence; detector angular aperture. Computer simulated spectra are compared to experimental data. The chi-square is calculated, to evaluate the goodness of fit. Through variation of target parameters, so as to fit experimental data, target composition and concentration profiles are obtained.