Probing the depths: ion beam analysis for material characterization

Ion Beam Analysis (IBA) plays a crucial role in non-destructive depth profiling of elements in the surface regions of materials. Narrow resonance profiling (NRP), a variant of nuclear reaction analysis (NRA), is bestowed with selectivity, sensitivity and high depth resolution. It exploits narrow resonances in the excitation function of a nuclear reaction and invokes the concept of stopping power for non-destructive depth profile measurements. A resonance in a nuclear reaction is characterized by resonance energy ER, cross section σR, and resonance width ΓR. Each of these parameters plays a vital role in depth profiling measurements. Ideally a resonance should be strong, narrow and well isolated to facilitate sensitive and high depth resolution measurements and to probe larger depths in the sample. Further, the off resonance cross sections should be as low as possible and there should be no interferences from competing nuclear reactions. Nuclear resonance reaction analysis is carried out by impinging the target material with projectiles of energy E less than ER and subsequently increasing beyond ER in regular energy intervals. Upon reaching the resonance energy ER in the target material the characteristic charged particles or γ-rays emitted, are detected for depth distribution studies. In the present talk some of the nuclear resonance reaction (NRRA) methodologies that have been standardised / developed in our laboratory will been presented. The NRRA methodologies thus developed have been employed for the characterisation of materials for technological, industrial, strategic and energy applications. (author)