X-Ray Photoelectron Spectroscopy in Analysis of Surfaces
Published Online: 15 SEP 2006
Copyright © 2000 John Wiley & Sons, Ltd. All rights reserved.
Encyclopedia of Analytical Chemistry
How to Cite
Oswald, S. 2006. X-Ray Photoelectron Spectroscopy in Analysis of Surfaces. Encyclopedia of Analytical Chemistry. .
- Published Online: 15 SEP 2006
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X-ray photoelectron spectroscopy (XPS) is an analytical technique that uses photoelectrons excited by X-ray radiation (usually Mg Kα or Al Kα) for the characterization of surfaces to a depth of 2–5 nm. Elemental identification and information on chemical bonding are derived from the measured electron energy and energy shifts, respectively. The use of ultrahigh vacuum (UHV) during analysis requires special sample handling. Depth profiling is possible using ion sputtering.
In contrast to the most popular surface analytical technique, Auger electron spectroscopy (AES), nonconducting material can be investigated, little material damage occurs, and the chemical shifts are easier to interpret. However, the lateral resolution of AES (typically 50 nm) is much greater than for XPS (50 µm for standard equipment, down to lower than 3 µm for dedicated instruments). The detection limit (of about 0.1 atom %) is not as low as for mass spectroscopic techniques, but the quantification from XPS peak area measurements is much better, even disclaiming standard sample measurements.
This article briefly discusses the principles of the technique, sample requirements, and the typical measuring strategy. Possible information sources (elements, chemical bonding, depth and lateral distributions) are described and their quantification principles are summarized. The main part deals with typical applications relating to several material classes (metals, semiconductors, insulators, polymers) to give a feeling for the effectiveness of the method over a wide range of research and technological problems. A comparison with similar techniques is given as a summary.
Technological developments in electronics, nanotechnology, polymers, biotechnology and medicine are all concerned with surface-related phenomena, suggesting sustained interest in XPS in the foreseeable future.