Effects of surface roughness on results in elastic recoil detection measurements

In order to study surface roughness effects on the elastic recoil detection analysis series of stainless steel samples were prepared to four different roughness by wet grinding and polishing. A multilayer film of B + C (20 nm thick)/Ti (220 nm)/B + C (20 nm) was electron beam evaporated on stainless steel samples and a flat silicon wafer. The time-of-flight elastic recoil detection analysis method utilizing a 53 MeV ¹²⁷I¹⁰⁺ beam was used to measure energy spectra of the recoiling sample elements. The topography of the samples was determined by atomic force microscopy and the film thickness by Rutherford backscattering spectrometry. A Monte Carlo simulation program which uses a measured surface structure and takes fully account of multiple scattering was written to simulate the elastic recoil measurements. Effects observed in the experimental energy spectra, like broadening of the peaks of deep lying layers, were reproduced in the simulations. Multiple scattering is the dominant factor behind the broadening for flat surfaces. It enhances strongly also the broadening due to the surface roughness.