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.

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.

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.

Angle-resolved XPS data is collected using a series of sample tilt angles.
Angle-resolved XPS data is collected using a series of sample tilt angles.

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