Sample Chamber of an XPS Instrument

X-Ray Photoelectron Spectroscopy (XPS)

XPS enables the surface sensitive elemental and chemical state analysis of samples


XPS at a glance

X-ray photoelectron spectroscopy (XPS) is a very surface sensitive (top ~10nm) analysis technique that measures the elemental composition and chemical state of a material using the feedback from an induced photoelectron effect. It is sometimes known by the alternative name Electron Spectroscopy for Chemical Analysis (ESCA).


  • Quantitative elemental composition
  • Empirical formula derivation
  • Depth profiling
  • Chemical state identification
  • Electronic state binding energies and densities
  • Elemental mapping (XPS imaging) 

 ISAC's LiPPS XPS system - Advanced X-ray source and sample tolerance

Images Courtesy of Vladimir Korolkov Photography

How does XPS work?

Samples are exposed to incident X-rays. Photons are absorbed by elements in the top few nanometres of the sample surface, leading to ionization and the emission of core (inner shell) electrons. The kinetic energy distribution of the emitted photoelectrons is measured in the spectrometer and the electron binding energies are determined.

For every element, there will be a characteristic binding energy associated with each core atomic orbital and therefore any given element produces a characteristic peak 'fingerprint' in the photoelectron spectrum.
Peak intensities can be related to the concentration of the given element allowing XPS to provide a quantitative analysis of surface composition.

Changes in oxidation state or chemical environment give rise to small variations in binding energy which in turn leads to small changes in peak position. These shifts are known as chemical shifts. The ability to discriminate between different oxidation states and chemical environments is a big advantage of the XPS technique.
XPS is not sensitive to hydrogen or helium, but can detect all other elements.



Our XPS Facilities

Hosted by the Nanoscale and Microscale Research Centre (nmRC)

Kratos Liquid Phase Photoelectron Spectroscopy Machine (LiPPS)


Thermo Fisher K-Alpha Photoelectron Spectrometer 

Thermofisher XPS


Kratos Liquid Phase Photoelectron Spectroscopy Machine (LiPPS)

  • Kratos Axis Ultra DLD machine with novel and unique, bespoke additional functionality for liquids and specialist samples:
  • High energy monochromated Ag source
  • Argon gas cluster source for high resolution depth profiling of organic materials (polymers and biological samples) to allow 3D chemical characterisation.
  • Bespoke electrochemistry stage for ‘in-situ’ work in ionic liquids.


Thermo Fisher K-Alpha Photoelectron Spectrometer 

  • X-ray source is Al Kα emission at 1486.8 eV.
  • Ion gun with energy range of 200 - 4000 eV. 
  • 180o double focussing hemisphercial analyser with 128-channel detector. 
  • Dual beam source charge compensation.
  • 4-axis sample stage, 60 x 60 mm sample area, 20 mm maximum sample thickness. 


Publications of Interest

Nanoscale and Microscale Research Centre

Cripps South building
University of Nottingham
University Park
Nottingham, NG7 2RD

telephone: +44 (0) 115 95 15046
email: nmcs@nottingham.ac.uk