RBS (Rutherford BackScattering) Y (a,a) Y


This method of analysis is based on the detection of the charged particles elasticaly scattered by the nuclei of the analyzed sample. It allows to separate the atomic masses of the elements and to determine the profile distribution in function ot the detected energy.

The cinematic is relatively simple and the energy is given by:

where:

E = energy of the particle scattered under the angle i
E0 = incident particle energy
M0 = incident particle mass
M1 = target atom mass


So, for a given angle and a given incident particle, the energy of the scattered particle mostly depends on the nucleus mass, at the condition that the reaction takes place near the surface where the energy lost of the incident beam is negligible in regard of E0.

When M0 << M1, K increases with M2 to attain 1, which allows the mass separation of target nuclei. The mass resolution also depends on E0, and alpha particles with energy near 2 MeV are generally used.

The characteristics of the method are the following:

where

Z0 = atomic number of the incident particle
Z1 = atomic number of target nucleus
E = energy of the incident particle

The following figure shows the different cases that can arise in function of atomic masses present in the successive layers.

This picture shows a spectrum obtained when bombarding a double layer of Hafnium and Yttrium on a thick Silicium substrate.



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Last Update: August 97
Henri-Pierre GARNIR <hpgarnir@ulg.ac.be>
David STRIVAY<dstrivay@ulg.ac.be>