ARXPS
A non-destructive technique allowing an increase in the surface sensitivity of the technique by changing the angle at which electrons are detected
Commonly in XPS instruments, the electron energy analyser is positioned so that most of the detected electrons have originated from the sample surface with a trajectory in line with the surface normal. It is here that XPS is the most bulk sensitive it can be for a given X-ray energy, with an information depth generally less than ca. 10 nm.
As electrons can only travel a given distance through a material before an interaction resulting in an energy loss occurs, varying the angle at which the electrons are detected from the surface, we enhance the surface contribution Therefore, by changing the tilt of the sample stepwise from 0° to 75°, surface sensitivity can be increased by the reduction in the XPS information depth.
Benefits
Applications
- non-destructive depth-profile of the top ca. 10 nm of a surface
- yields thin-film thickness measurements
- identifies spectral contributions from the surface vs bulk.
- non-destructive depth-profiling of thin layer interfaces
- thin oxide or overlayer thickness measurements
- layer-ordering of multiple thin layers on a flat substrate.
Availability
All systems at Harwell, Cardiff, UCL and Manchester are equipped with angle resolved capabilities, including a dedicated parallel ARXPS (p-ARXPS) system at UCL. This latter system allows for the simultaneous detection and analysis of electrons from a 60o angular range, greatly reducing analysis time, and making very advanced analysis possible. pARXPS has the advantage of readily analysing larger samples, such as 2" silicon wafers which cannot be tilted in a conventional ARXPS experiment.