RutherfordBackscatteringSpektrometrie

Rutherford backscattering spectroscopy (RBS) is an ion beam analysis technique used to determine the composition and thickness of thin films and surface layers on solids. In a typical experiment, a beam of high-energy ions, most commonly helium-4 ions in the MeV range, is directed at a sample in vacuum. Detectors measure the energies of ions scattered backward at a fixed angle. The resulting energy spectrum reflects the masses of the target atoms and their depth distribution, because ions lose energy as they pass through material before and after scattering. By comparing the measured spectrum with simulations that incorporate energy loss, stopping powers, and the Rutherford scattering cross section, one can identify elements and estimate areal densities and layer thicknesses.

RBS is especially useful for multilayer structures and for quantifying heavy elements in thin films with good depth resolution. The depth profiling is achieved by the relationship between the scattering kinematics and the target mass, as well as by energy loss through the material. Channeling configurations can be employed on crystalline samples to assess lattice order and crystal quality. While effective for many elements, standard RBS has limited sensitivity for light elements such as hydrogen, and accurately quantifying those elements often requires complementary techniques or specialized variants.

Limitations of the method include reliance on accurate stopping powers and cross sections, potential sample damage from ion bombardment, and spectral overlaps in complex mixtures. Nevertheless, RBS is valued for its non-destructive nature, quantitative capabilities, and relatively fast analysis of a wide range of materials, making it a common tool in semiconductor research, materials science, and cultural heritage studies.

RBS emerged in the mid-20th century as part of the development of ion beam analysis and has since become a standard technique for surface and thin-film characterization. Related methods, such as elastic recoil detection and PIXE, are often used to complement RBS data.