Surface Characterization

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Low Energy Ion Scattering (LEIS)

How it works

Considered the most surface sensitive elemental analysis technique in existence, LEIS uses a low energy beam of He or Ne ions to probe the top atomic layer of a sample.

 

3-10 keV He or Ne ions are focused onto the surface of a sample. A toroidal analyzer determines the energy of the backscattered ion, which can be used to determine the element from which it scattered. Due to the low energy of the technique, only the top monolayer of atoms contributes to the signal. Analysis of rough and non-conductive surfaces is possible.
 

 

 

Applications
  • Surface composition of metal oxide catalysts
  • Pinhole detection in ALD thin films
  • Impurity detection on semiconductor surfaces
  • Oxygen exchange via 18O detection

Sample Preparation
  • O/H plasma cleaning
  • Heating up to 600°C
  • Gas dosing up to 10 mbar
  • Glass fracturing in vacuum
  • Ar sputter depth profiling
     

 

 

 

CONTACT
Dr. Ryan Thorpe

FURTHER READING
T. Grehl et al., Microscopy Today (2011) 34
H.H. Brongersma et al., Surf. Sci. Rep. 62 (2007) 63-109

SYNONYMS AND RELATED TECHNIQUES
Ion Scattering Spectroscopy (ISS), Rutherford Backscattering Spectrometry (RBS)

Near-Ambient Pressure X-Ray Photoemission Spectroscopy (NAP-XPS)

Once only possible at national labs, near-ambient-pressure XPS is now available at Lehigh University using a new SPECS DeviSim NAP reactor cell coupled with a PHOIBOS 150 NAP electron energy analyzer.

How it works

X-rays from an Al Kα source impinge on the sample through a thin Si3N4 membrane in the environmental cell.  A portion of the photoelectrons enter the electron analyzer through a small aperture. Gas particles are removed by a series of pumps before reaching the detector.  Ionized gas atoms or molecules replenish the electronic charge that has left the surface, mitigating sample charging.

 

 

 

Applications
  • In operando measurements of catalysts
  • Characterization of biological materials and other non-vacuum-compatible samples
  • Measurements of surface-gas or surface-liquid interfaces
Sample Preparation
  • In situ gas dosing up to 1 mbar
  • Heating up to 600°C
  • Ar sputter depth profiling

CONTACT
Dr. Ryan Thorpe

FURTHER READING
https://www.specs-group.com/nc/specsgroup/knowledge/methods/detail/nap-xps-and-nap-ups/

SYNONYMS AND RELATED TECHNIQUES
Electron Spectroscopy for Chemical Analysis (ESCA), Photoemission Spectroscopy (PES)