X-Ray Photoelectron Spectroscopy (XPS/ESCA)

This technique is based on the Photoelectric Effect. When a material is irradiated with x-rays, photoelectrons are subsequently ejected from the surface. The kinetic energy of an emitted photoelectron is equal to the difference between the photon energy, and the binding energy of the electron (K.E. = hν - B.E.). The technique is inherently surface sensitive because the majority of the measured photoelectrons originate in the outer 5-10 nm of the sample surface. The spectra contain information about the elemental composition, concentrations and chemical environments (i.e. oxidation states) of surface and near surface atoms. Greater depths (up to a few microns) can be probed by coupling the technique with ion milling. Quantitative chemical state imaging is possible with some samples. The analyses are non-destructive for many, but not all materials.

Capabilities
  • surface sensitive (top 1-10 nm)
  • semi-quantitative without standards
  • elemental analysis
  • chemical state information available for many elements
  • in-depth information available via Ar ion beam depth profiling
  • chemical state imaging with a lateral resolution of 10-20 microns
  • thin-films, powders, fibers, and bulk materials can be analyzed
  • sample cooling and heating from -100℃ to 500℃
Sample Requirements
  • any vacuum compatible solid (thin films, powders, fibers, bulk materials)
  • size (< 50 mm length X 50 mm width X 13 mm height)
Restrictions

Samples must be ultra-high vacuum compatible. Contact Vince to discuss this requirement. Elements of interest must be at a concentration of approximately 0.1-1 atomic percent or greater with the information depth. Sample thickness is limited to about 13 mm or less.

Instrumentation

Physical Electronics VersaProbe II

Kratos Analytical Axis Ultra*

* The Kratos Ultra XPS was purchased with the generous support of the National Science Foundation (DMR #0114104)

Typical Applications

Organic Coatings and Films
  • surface functionality
  • surface modification
  • molecular orientation
  • adhesion studies
  • surface segregation
  • failure analysis
  • metallized layers
Ceramics, Glasses & Minerals
  • composition and thickness of optical coatings
  • fiberglass coatings
  • powder surface chemistry
  • mineral weathering
  • layer thickness and composition
  • organic coatings
  • impurity determination
  • bridging vs. non-bridging oxygen
Semiconductors
  • film stoichiometry
  • layer thickness
  • etch residues
  • low energy ion implant characterization
  • surface contaminants
  • reverse engineering
  • gate dielectrics
Metallurgy
  • diffusion studies
  • surface segregation
  • interface formation
  • corrosion and oxidation studies
  • surface contaminants
Catalysts
  • zeolite composition
  • catalyst poisoning
  • oxidation state determination