X-ray Photoelectron Spectroscopy (XPS) is sometimes known as Electron Spectroscopy for Chemical Analysis (ESCA). This is a surface sensitive technique which provides compositional and chemical state information on the top 3 – 10 nm of the material. XPS can be used to analyse both powder and solid samples, including metals, ceramics and polymers. It is capable of detecting all elements except Helium and Hydrogen.

XPS provides the capability to carry out depth profiling using an ion beam. This technology is vital for producing a multi layered depth profile; it provides the ability to measure changes in the oxidation state and composition of elements as a function of depth.

When dealing with uniformed layers, it can be useful to confirm what order the layers are within the material. For this Angle Resolved XPS can be used.

This technique is used widely in the study of thin films, corrosion and adhesion research. A common application is the measurement of silicone transfer rates from release papers or liners.

Theory:

In XPS, the surface of a solid sample is irradiated with X-rays. These excite photoemission from the core levels of the atoms present on the surface and the resulting photoelectrons emerging from the surface are collected and their energy analysed. The kinetic energy of a photoelectron depends on the binding energy of electrons in the core levels from which photoemission is excited and each element gives rise to a set of peaks at characteristic energies. Hence the photoelectron spectrum allows identification of the elements present in the surface. The concentrations of these elements can be calculated from the relative intensities of the photoelectron peaks. In addition, the emitted electrons are of such an energy that only those from the top few atomic layers have a significant chance of escaping from the surface without losing energy, hence the technique is highly surface sensitive.

XPS can also provide detailed chemical information about the surface, as the energy of the photoelectron is dependent on the local chemical environment of the atom from which it arose. This often allows the chemistry of the surface to be inferred and the functional groups present to be identified.

Typical applications:

• Measurement of surface composition in failure analysis and adhesion problems
• Characterisation of the chemistry of surface treatments
• Functional group identification
• Corrosion /oxidation studies
• Evaluation of surface cleanliness
• Catalyst characterisation

Upgrades:

• Additional tilt module for Angle resolved XPS

Specification:

• Ion Gun Operating Range 100 eV - 4 keV
• Maximum Sample Size Maximum analysis area - 60 x 60 mm
• Maximum thickness - 20 mm
• Types of Sample Material Powders, Solids, Ceramics, Metals, Polymers
• Tilt Range -90° to +90°