X‐Ray Photoelectron Spectroscopy in Analysis of Surfaces

Abstract

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.

Mesoporous Silica Modified with Polydopamine and Zinc Ions as a Potential Carrier in the Controlled Release of Mercaptopurine

“…Based on the X-ray photoelectron spectroscopy (XPS) results, they determined that 0.34% Zn is on the surface. The greater content compared to that in this work is due to the fact that the EDS technique determines the ion content deeper than the XPS technique [ 49 , 50 ]. Zinc ions are on the surface, so their amount in the presented work is smaller.…”

Automatic Joining of Electrical Components to Smart Textiles by Ultrasonic Soldering

“…The tensile strength during the peeling test decreased from 25.5 N to 23.5 N, which means around 10%. In X-ray Spectroscopy (XPS) tests for surface cleaning, it was proven that acetone or other cleaning agents leave (carbon) residues on surfaces that negatively influence subsequent coating processes [ 30 ].…”

“…The tensile strength during the peeling test decreased from 25.5 N to 23.5 N, which means around 10%. In X-ray Spectroscopy (XPS) tests for surface cleaning, it was proven that acetone or other cleaning agents leave (carbon) residues on surfaces that negatively influence subsequent coating processes [30]. Related to our test setup and our equipment possibilities, we found the following soldering parameters as a compromise between shear strength and contact resistance: Sn99.7Cu0.3 at 350 • C, an ultrasonic working time of 0.5 s and a power of 10 W (Table 1).…”

X‐Ray Photoelectron Spectroscopy in Analysis of SurfacesUpdate based on the original article by Steffen Oswald,Encyclopedia of Analytical Chemistry, © 2000, John Wiley & Sons, Ltd.

“…Metal-metal interfaces are often used in electronic contacts. Marinova et al (93) showed an example of an Al−Ni−Al on SiC contact system where both the elemental changes and peak shape changes connected with phase formation were explained on the basis of depth-profiling measurements. Working with Pd−Co superlattices, Lesiak et al (94) determined the interface phases using a pattern recognition method.…”