X-Ray Photoelectron Spectroscopy (XPS/ESCA)
Description
Soft x-rays (<1.5 keV) ionize atoms in a solid producing photoelectrons from core shells (the photoelectric effect). The kinetic energy of the emitted electron is equal to the x-ray energy less the energy that the electron is bound to the atom (K.E. = hν - B.E.). The low kinetic energy (by definition < 1.5 keV) makes the technique inherently surface sensitive with the majority of the photoelectrons in a given sample originating from the outer 5 nm. The number of electrons detected is proportional to the concentration in the sample. Perhaps most importantly, the exact binding energy is a function of the local environment of the atom yielding a chemical (or oxidation) state sensitive tool.
Rates
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Technique Advantages
- surface sensitive (top 1-10 nm)
- quantitative without standards
- chemical state information available for many elements
- in-depth information available by changing sampling geometry or ion beam depth profiling
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
Download application notes: XPS and HR-TEM Analysis of High k Thin Films
Sample Requirements
- any vacuum compatible solid (thin films, powders, fibers, bulk materials)
- size (< 50 mm X 50 mm X 25 mm)
Other Information
- We have an XPS listserv to keep everyone informed of developments in our lab. To become a member send an email to listserv@lists.psu.edu; the body of message should be "sub l-mcl-xps"
- Download a nice tutorial on XPS.
- Download a PDF manual for Kratos Axis Ultra XPS system operation.
- Related PSU coursework
- Materials Science 597E, X-ray Photoelectron Spectroscopy, 1-credit lab course (Spring only)
- Chemistry 448, Surface Chemistry, 3-credits (Fall only)
- Materials Science 430, Materials Characterization, 3-credits (Fall only)
- Surface Science Spectra Online
- NIST database (XPS database of positions and escape depths)