XPS/UPS Spectroscopic Analysis
X-Ray photoelectron spectroscopy (XPS) and Ultraviolet photoelectron spectroscopy (UPS)
X-ray photoelectron spectroscopy (XPS) and Ultraviolet photoelectron spectroscopy (UPS) are surface chemical analysis techniques that can be used to analyse the surface chemistry of a material in its unprocessed state, or after some treatment such as: fracturing, cutting or scraping in air or UHV to expose the bulk chemistry, ion beam etching to clean off some of the surface contamination, exposure to heat to study the changes due to heating, exposure to reactive gases or solutions, etc.
They are used to measure:
- elemental composition of the surface,
- empirical formula of pure materials,
- elements that contaminate a surface,
- chemical or electronic state of each element in the surface,
- uniformity of elemental composition across the top surface (aka, line profiling or mapping),
- uniformity of elemental composition as a function of ion beam etching (aka, depth profiling).
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Further Information:
This facility provides expertise and equipment to perform surface analysis of different types of solid samples, supplying information on their composition and electronic structure by using photoelectron spectroscopy data obtained with the different modes of operation of the instrument (XPS, UPS, ARPES, AES). XPS measures the elemental composition, empirical formula, chemical state and electronic state of the elements that exist within a material by irradiating the sample with a beam of soft X-rays while simultaneously measuring the kinetic energy and number of electrons that escape from the top 1 to 10 nm of the material being analyzed. On the other hand, UPS uses UV radiation to study adsorbed species, their binding to the surface and their orientation. The angle resolved mode ARPES, which is the most relevant feature of this instrument, allows for studying the electronic structure of the surface of solids. The Auger electron spectroscopy mode (AES) is used for probing chemical and compositional surface environments.
The system is based on a hemispherical energy analyzer PHOIBOS 150 from the German company SPECS which is installed in a ultra high vacuum chamber together with a complete set of monochromatic light sources of X-rays and UV light, fast entry chamber and sample cleaning and manipulation system. The system includes also a low energy electron diffraction (LEED) instrument to determine the surface crystal structure of the substrate and adsorbates.
