RBS Theory: Layer Thickness Measurements

By measuring the energy width of the Ta peak or the Si step and dividing by the energy loss of He per unit depth in a TaSi matrix, the thickness of the TaSi layer can be calculated.

For example, the low energy edge of the Ta peak corresponds to scattering from Ta at the TaSi/Si interface. The illustration shows that particles scattered from tantalum at the TaSi/Si interface of the 230 nm film have a final energy of about 1.9 MeV, while particles scattered from the same interface of the 590 nm film have less final energy (about 1.7 MeV) because they have passed through more TaSi. The entire Ta peak spans a greater energy range, because of the increased thickness of the layer it represents.

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