The optimization of a rutherford backscattering geometry for enhanced depth resolution

Abstract

A simple geometrical method for improving the depth resolution of the RBS technique is presented. A critical appraisal of the resolution-limiting factors such as beam collimation, detector acceptance angle, multiple scattering, and surface topography effects is given in an attempt to optimize the geometry for maximum attainable depth resolution. An optimized low-angle geometry in which the incident beam impinges onto the target surface at 5° and the detector is positioned for 168° scattering leads to ∼8 times resolution improvement: the expected system depth resolution becomes 20-30 Å for a solid-state detector (15 keV fwhm). The effects of multiple scattering and surface topography on system resolution are examined experimentally: for carefully prepared target surfaces (vibratory polished and etched) system resolutions approaching those expected from the optimum RBS geometry can be attained in practice for near-surface analysis. At large analysis depths and for samples with ill-prepared surfaces the system resolution will be noticeably degraded and the resolution profile may become decidedly asymmetric. Show more