LINEAR STOPPING POWER APPROXIMATION METHOD FOR COMPUTING WITH A POCKET CALCULATOR THE NUMBER OF ATOMS IN A THIN-FILM FROM THE RBS YIELD

A simple method is described for the determination of the number of atoms in a thin film from the integral of the elastic backscattering yield, using a pocket calculator. The energy dependence, E-2, of the Rutherford scattering cross section, and the screening of the nucleus charge by the electron cloud is taken into account. The method is based on the common assumption that the stopping power is a linear decreasing function of the energy, in the energy range of interest in RBS, that is from 1.4 MeV to 2.0 MeV. The total yield can then be integrated analytically, and the number of atoms in the film can be determined by an iteration procedure that can be performed with a scientific pocket calculator. The results obtained with this method are compared with the values obtained using the computer simulation code for RBS spectra RUMP.