X-ray Photoelectron Spectroscopy Laboratory
About the Laboratory
X-ray Photoelectron Spectroscopy (XPS), also sometimes referred to as ESCA (electron spectroscopy for chemical analysis), is a non-destruction analysis tool used to examine the surface chemistry of a variety of samples. This is a widely used technique because it can provide both qualitative and quantitative chemical state information from the surface of the material under investigation. XPS can be performed on solid materials in many forms including solid pellets, powders, surfaces, and coated surfaces if the materials are compatible with ultra high vacuum (UHV).
XPS is performed under UHV to prevent surface contamination from building up on the materials under investigation. XPS is usually accomplished by using mono-chromated X-rays to excite the surface of a material and using a hemispherical analyzer to detect the energy of the emitted surface electrons. In general, the top 5 nm of the material surface will be investigated. The chemical elements present at the surface can be identified by examining the binding energies for the photoelectron peaks detected. Additionally, utilizing the binding energies, peak shapes and intensities together provides information regarding the chemical state and electronic structure of the elements present at the surface.
The information provided by XPS can play major roles in many research fields with applications in corrosion, failure analysis, surface treatment, thin films/coatings, catalysis, photovoltaics, display technology, electronic device development, magnetic media, nanomaterials and many others.
Instruments in Lab
The AXIS Supra, by Kratos Analytical, is equipped with a 500 mm Rowland circle monochromated Al Kα (1486.6 eV) X-ray source to provide excellent energy resolution. It has a 165 mm mean radius hemispherical analyzer to ensure excellent sensitivity and resolution. Additionally, the system is equipped with a unique spherical mirror analyzer and 2D delay-line detector to allow fast parallel imaging to provide images with high spatial resolution.
The system at the SSSC is equipped with a monatomic Ar+ source that is fully integrated to provide ease for both sample cleaning/sputtering and depth profiling.
Additionally, the XPS at the SSSC is equipped with a UV discharge source (He filled) for ultraviolet photoelectron spectroscopy (UPS) allowing for either valence band acquisition or electronic work function measurements.
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Training for the XPS at the SSSC is limited to individuals in groups that will utilize the system for a large part of their research. This instrument is very delicate and high maintenance due to the UHV component. For information regarding usage and training, contact Dr. Ramaswami Sammynaiken to discuss needs and to arrange a training session.