X-ray Photoelectron Spectroscopy (XPS) is used to identify and quantify surface elements via detection of valence and core electrons with binding energies characteristic of those elements. Wide-range survey spectra are used to detect elemental composition over a depth of around 10 nm, with most of the signal coming from the first few nm. Chemical shifts found in high-resolution narrow region spectra will then provide insight into chemical environment and oxidation states. XPS can be used to characterise organic, inorganic and metallic thin films and semi-conductors, in the form of surfaces and powders. A charge neutraliser allows powders and insulating materials to be measured by compensating for the spectral shift due to surface charging. The Kratos AXIS Supra+ is equipped a variety of excitation sources and experimental capabilities: - Dual source X-ray filament (Ag/Al) to cover a wide range of possible emission energies for XPS. - Angle-resolved XPS and XPS imaging. - Gas cluster ion source (GCIS) that produces monatomic or 1000+ cluster Argon ions for surface etching and depth profiling. - Ultraviolet photoelectron spectroscopy (UPS) accessory to probe low binding energy valence electrons with improved sensitivity and resolution over XPS – this allows the user to determine valence band edge and density of states. - Electron source power supply for reflection electron energy loss spectroscopy (REELS), which can determine electronic band gaps or energy levels of unoccupied molecular orbitals. - N 2 purged glovebox and sample transfer arm to help load air-sensitive samples. - Heating and cooling accessories to bring sample holder up to +800°C and below -100°C using liquid nitrogen. Single piece samples should be at least 3 mm x 3 mm in size, and ideally be no larger than 15 mm x 15 mm. They should also be no thicker than 6 mm. Samples outside this range can be considered on a case-by-case basis. Powder samples can be submitted, but for XPS only, and must be at least 100 mg.
