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Rutherford Backscattering Spectrometry (RBS)
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Energy spectrometry using MeV He+ ions. The incident He+ ions are elastically scattered by nuclei of the analytical sample, providing a quantitative elemental depth profile. Multi-component, multi-layered samples can be analyzed to a depth of 1mm or more.
RBS has the following characteristics:
- Multi-element depth concentration profiles
- Fast, non-destructive analysis (no sample preparation or sputtering required)
- Matrix independent (unaffected by chemical bonding states)
- Quantitative without standards
- High precision (typically ±3%)
- High sensitivity (e.g. 1011 Au/cm2 on Si, depends on Z and sample composition)
- Depth range typ. 0 - 1mm
- Depth resolution ~20Å typ. near surface
- Spatial definition :
- - beam spot size 0.5-2.0 mm
- - map or raster option to 7cm x 7cm
Typical Applications
- Absolute thickness of films, coatings and surface layers (in atoms/cm2)
- Surface/interface contaminant detection (oxide layers, adsorbates, etc)
- Interdiffusion kinetics of thin films (metals, silicides, etc)
- Elemental composition of complex materials (phase identification, alloy films, oxides, ceramics, glassy carbon, etc)
- Quantitative dopant profiles in semiconductors
- Process control monitoring - composition, contaminant control
Typical example of RBS analysis: A 1000Å thick film of TiN on a Si substrate. The figure shows a background subtraction of the Si substrate to reveal the N peak. The ratio of the Ti and N peak areas gives the atomic concentration and the sum of the peak areas is the film thickness.
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