Rutherford Backscattering Spectroscopy

Rutherford Backscattering Spectroscopy (RBS) In RBS an energetic (1-3 MeV) beam of He ions is incident on the surface and the energy spectrum of the backscattered ions is recorded. The energy loss of the He ions is predominantly inelastic but there are occasional elastic collisions (~ one in 4000) resulting in a backscattering event. The energy of these back-scattered particles (governed by the kinematic factor) provides information regarding the mass of the host atom from which the scattering event has occurred which provides a mass scale. At the same time the rate of energy loss of the ions, combined with knowledge of the stopping power cross sections of He in the matrix, provides a depth scale. One can then derive concentration vs. depth form the resulting spectra. RBS is the only surface analyses technique, which does not rely upon use of standards for quantification. The sensitivity in RBS is a function ~ Z2 and hence it is best suited for analysis of heavier elements or layer on lighter substrates. The applications areas are depth profiling of thin film structures, In channelling mode the beam is aligned in a low index crystallographic plane of the host material will allow quantitative measure of damage e.g. dislocations, stacking faults, interstitials and point defects. It can also be used for atom location in the lattice. The main application areas are damage and damage recovery studies in solids.

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