The X-ray Photoelectron Spectroscopy (XPS) Core provides equipment, expertise and support for researchers studying materials. XPS is an essential analysis technique for many areas of materials research including chemical, mechanical and electrical engineering, chemistry, physics, public health and biotechnology among others.

Visit the XPS Core iLabs page for details on equipment, pricing schedules and information on working with the core.

 

What Is XPS?

X-ray photoelectron spectroscopy, which is also known as Electron Spectroscopy for Chemical Analysis (ESCA), provides quantitative compositional information from the top atomic layers of a sample surface for the elements lithium to uranium. The center can also obtain information regarding the chemical states of any elements present.

XPS is used to analyze the change in surface chemistry of a material after certain chemical or physical treatments such as: 

• Leaching
• Reduction
• Fracture
• Cutting or scraping in air or ultra-high vacuum to expose the bulk chemistry
• Ion beam etching to clean off some of the surface contamination
• Exposure to heat to study the changes it causes
• Exposure to reactive gases or solutions
• Exposure to ion beam implant
• Exposure to UV light

 

How Measurements are Obtained

A sample is irradiated with a beam of monochromatic soft X-rays. Photoelectron emission results from the atoms in the specimen. The kinetic energies of these electrons relates to the atom and orbital from which they originated. The distribution of kinetic energies from a sample is then measured directly by the electron spectrometer.

Atomic orbitals from atoms of the same element in different chemical environments are found to possess slightly different (but measurable) binding energies. These "chemical shifts" arise because of the variations in electrostatic screening experienced by core electrons as the valence and conduction electrons are drawn towards or away from the specific atom. Differences in oxidation state, molecular environment and co-ordination number all provide different chemical shifts.

Photoelectron binding energy shifts are, therefore, the principal source of chemical information. It should be noted that these shifts can be very small and can only be detected using a high performance instrument with suitable software such as our Kratos Axis Ultra DLD instrument equipped with a monochromated Al Ka x-ray source and hemispherical analyzer.

 

Secondary Ion Mass Spectrometry (SIMS) Capability

SIMS stands for secondary ion mass spectrometry. A high energy primary ion beam is focused to bombard the surface of materials. The impact ruptures surface structures , producing neutral species, electrons, and ions (secondary ions) ejected from the surface. Analyzing the secondary ion provides surface chemical composition information. SIMS is the most sensitive material characterization technique, with a detection limit from parts per million to parts per billion. The most important application for SIMS is to perform a depth profiling (also called dynamic SIMS) of materials. At USC, our SIMS capability is directly attached to XPS system.

 

Our Pricing and Procedures

XPS pricing was developed for University of South Carolina users, for non-USC academic investigators and for industrial users. Please download the appropriate spreadsheet, compile the cost estimate calculator, and return with the Sample Information Sheet.

User Type	XPS Usage with Staff Assistance	Independent XPS Usage	Gas Cell Usage*	Staff Time (Data Analysis & Gas Cell Operations)
Internal	$80/hr	$20/hr	$15/day	$60/hr
External Academia	$130/hr	$60/hr	$150/day	$70/hr
Industry	$325/hr	$150/hr	$200/day	$125/hr

*Gas cell/catalytic cell usage price is per day;  only 1 sample can be reduced in the gas cell in a day; staff time is not included in the gas cell usage price.

• USC user cost worksheet (XLSX)
• Non-USC academic cost worksheet (XLSX)
• Industrial user cost worksheet (XLSX)

 

General Information

All samples must be accompanied by a Sample Information Sheet (DOCX) with account number for charges. Experiments requiring multiple days must be scheduled in advance and may require longer turn-around time.