Rutherford backscattering (RBS)

Rutherford backscattering spectrometry (RBS) detects the energies and amount of the backscattered ions from a solid target.  The incident probe is a mono-energetic light ion beam, typically MeV He ions.  The scattered He particles from the target are energy analyzed by a solid state particle detector (Si surface barrier detector) positioned at a backscattered angle with respect to the incident ion beam (typically ranging from 100-170° depending on the specific analysis).  The energy of the backscattered He ions are dictated by conservation of energy and momentum between the incident ion and the scattering atom and can be related to the depth and mass of the target.  The amount of backscattered ions from any given element is proportional to its concentration.  Therefore RBS can be used as a tool to investigate the depth profile of individual elements in a solid quantitatively.