RBS - Rutherford Backscattering Spectrometry

Rutherford backscattering spectrometry allows to examine the chemical composition of sample materials. RBS is a widely-used method in various fields.

Usually a beam of 2 MeV Helium ions provided by a particle accelerator is used to irradiate the samples while the energy distribution of backscattered ions is measured. The RBS spectrum allows to obtain quantitative results combined with a depth information. For example, the spectra of thin film deposited on a substrate are analyzed to determine the stoichiometry and thickness. RBS is particularly suitable for elements of high atomic number, whereas the other sample elements (matrix, substrate) are of low atomic number.

Typical parameters, pros and cons of RBS:

  • gives the chemical composition (stoichiometry)
  • gives the absolute number of atoms
  • absolute: no standard is necessary
  • usually nondestructive
  • probed depth in the range of about 2 µm
  • depth profiles, film systems - lateral resolution ≥ 500 µm
  • measuring time per sample: 5-20 min 
  • elements with similar masses cannot be separated
  • lower sensitivity to light elements - H and He cannot be detected
  • no information on crystal morphology, chemical bonding

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