Use of reference samples for more accurate RBS analyses

Abstract

While one of the primary assets of RBS analysis is that it is quantitative without use of reference samples, for certain types of analyses the precision of the method can be improved by measuring RBS spectra of unknowns relative to the RBS spectra of a similar known sample. The advantage of such an approach is that one can reduce (or eliminate) the uncertainties that arise from error in the detector solid angle, beam current integration efficiency, scattering cross-section, and stopping powers. We have used this approach extensively to determine the composition ( x) of homogeneous thin films of TaN x using as reference samples films of pure Ta. Our approach is to measure R=( Ta count ) unknown /( Ta count ) standard and use RUMP to determine the function x( R). Once the function x( R) has been determined, this approach makes it easy to analyze many samples quickly. Other analyses for which this approach has proved useful are determination of the composition ( x) of WN x , SiO x H y and SiN x H y , using W, SiO 2 and amorphous Si as reference samples, respectively.