High Energy XPS

Conventional X-Ray Photoelectron Spectroscopy (XPS) is a surface-sensitive probe of the sample chemistry with an information depth of approximately 1 - 2.5nm or <10 atomic layers. Conventional XPS uses an X-Ray photon energy of ~1.5keV. In HAXPES higher energy X-Rays in the range of 3-15keV are used which allows a much greater information depth up to ~25nm to be probed. This enables measurements of buried interfaces and bulk properties that would be impossible with conventional XPS. When the two energy ranges are combined into a single XPS system like the SPECS Flex Probe, this becomes an extremely powerful tool for combining surface and sub-surface analysis within a single tool. The Flex Probe system uses a newly developed chromium-based X-Ray monochromator with an energy of 5.4keV. As the X-Ray energy increases, the cross section decreases, so less photoelectrons are produced. 5.4keV was chosen an optimum energy which balances the need to probe greater information depths with the lower flux of electrons produced at higher energies. The source is designed to produce the highest possible flux of X-Rays, so when coupled with the latest high transmission analyser and detector from SPECS, we are able to measure the best signal from the available photoelectrons. Since SPECS is the market leader in NAP XPS, this technology is available in a near ambient version for chamber pressures up to 100mbar.