Flexible Electronics

Ultra High Vacuum System

Resources Thursday, 14 February 2019 16:28

Surface characterization techniques: XPS/ UPS/ EELS

X-ray photoelectron spectroscopy (XPS) is a surface analysis technique capable of providing elemental and chemical state information from the outer 5 to 12 nanometres of a solid surface. All elements can be detected with detection limits in the 0.1 to 0.5 atomic percent.


Similar with XPS, Ultra violet photoelectron spectroscopy (UPS), using UV radiation (with photon energy of 10-45 eV) examines valence levels. The Work function of the materials and the Ionization Potential of an organic material can be determined. The information depth is ~3nm.

By stepwise deposition of a material onto a substrate the determination of the energy level alignment at the interface can be determined by XPS/UPS techniques. Combination of the methods can reveal the appearance of an interface dipole or band bending effects.

Electron energy-loss spectroscopy (EELS) is a surface analytical technique that measures the change in kinetic energy of electrons after they have interacted with a specimen. The low-loss or valence region of an EEL spectrum (< 50 eV) provides valuable information about the band structure and in particular about the dielectric properties of a material (e.g., band gap, surface plasmons). The information depth is ~3nm.

Moreover, the Ultra High Vacumm Chamber is equipped with:

(a) Ion gun for sputtering the surfaces (for contamination removal) and for controllable induce defects onto graphene sheets,

(b) a stainless steel sample holder able to be heated up to 650 °C in order to thermal reduction of oxides, GO, e.t.c.,

(c) gas inlet systems in order to surface exposure under various gases and controllable pressures ranging from 10-6mbar up to 1bar.

Last modified on Tuesday, 19 March 2019 22:02