Further improved technique for channeled stopping power measurements

Abstract

A few years ago, an ingenious method was proposed to quickly and accurately measure the difference between random and aligned stopping powers without the need for free-standing mono-crystalline thin films; the main idea was to increase the energy of the incident ion beam so that the channel numbers for a characteristic feature in the backscattering spectrum in random and aligned direction coincide, thus compensating for the difference in stopping power endured by the outgoing ions (Greco et al. 2007) [7]. A small drawback of this method is that the total length of the path that the ion travels through the thin film is slightly different in random and aligned geometries. We have improved this method by changing the measurement geometry such that the aligned and random ions travel the exact same distance through the thin film. Representative results for 0.5–3MeV He ions channeled in <011> Si are presented and show that earlier measurements appear to overestimate slightly the reduction in stopping power for channeled ions.