What is angle-resolved XPS?
Analysis of a thin oxide film on a metal at near-normal and near-grazing collection angles could produce spectra with a larger relative intensity of the oxide peak at the near-grazing emission angle.
The information depth for XPS is a few nanometers, depending upon the kinetic energy of the electrons and the material being analyzed. Angle-resolved XPS (ARXPS), however, is a technique that varies the emission angle at which the electrons are collected, thereby enabling electron detection from different depths. ARXPS provides information about the thickness and composition of ultra-thin films. Such measurements are non-destructive, unlike sputter profiling.
Three major reasons why angle-resolved XPS is useful
- It can be applied to films that are too thin to be analyzed by conventional depth profiling techniques.
- It can be applied to films that are irretrievably damaged by sputtering (e.g., polymers).
- It is non-destructive and can provide chemical state information, unlike methods based upon sputtering.
Angle-resolved XPS measurements provide the following information:
- Ordering of layers in an ultra-thin film.
- Thickness of layers
- Distribution of elements and chemical states within the film (depth profile reconstruction).
Angle-resolved XPS data acquisition
Angle-resolved XPS experiments are undertaken in a serial manner, by limiting the angular acceptance of the analyzer and stepping through a range of angles in turn. This is usually undertaken by tilting the sample with respect to the analyzer.