Auger Electron Spectroscopy

(AES)

Principle of AES A fine focused electron beam

bombards the sample and ejects an electron of the inner shell of the atom.

This vacancy must be refilled by an electron from a higher energy level.

When the higher energy electron fills the hole, the release of energy is transferred to an electron in an outer orbit electron.

That electron has sufficient energy to overcome the binding energy and the work function to be ejected with a characteristic kinetic energy.

The ejected electron is referred to as an Auger electron after Pierre Auger who first discovered it in 1925.

Principle of AES

The Auger electron has an energy given by:

EAuger = EK – EL1 – EL2,3 -

where EK, EL1 and EL2,3 are the binding energies of the K1, L1 and L2,3 electron orbits of the atom. is the work function.

Principal Auger Electron Energies

Auger Electron Yield

Direct and Differential Spectra

Direct and Differential Spectra

Chemical Effects

Chemical Effects

Spectrometer

Cylindrical Mirror Analyzer (CMA)

Secondary electrons passing through a slit in the inner cylinder are deflected by a negative potential applied to the outer cylinder and pass through the exit slit onto an electron multiplier where they are detected.

For any given potential applied to the cylinder, only electrons with specific energy will pass through the exit slit.

A spectrum is built up by sweeping the outer cylinder potential.

Spectrometer

Spectrometer

Auger Maps

Analysis of Surface Contamination

Sputter Profiling

Sputter Profiling

Sputter Profiling

References

J. M. Walls, Editor, Methods of Surface Analysis: Techniques and Applications, Cambridge University Press, Cambridge, 1989.

J. P. Sibilia, Editor, A Guide to Materials Characterization and Chemical Analysis, VCH Publishers, Inc., New York, 1988.

P. E. J. Flewitt and R. K. Wild, Physical Methods for Materials Characterization, Institute of Physics Publishing, Bristol, 1994.

D. Briggs and M. P. Seah, Practical Surface Analysis by Auger and X-ray Photoelectron Spectroscopy, John Wiley and Sons, New York, 1983.