Microanalysis of surfaces and thin films

Microanalysis aims to determine the elemental chemical composition of the smallest possible volume of matter. The principle consists of probing this matter with a more or less loose brush of energetic particles known as primary particles – electrons, photons, neutrons, protons or heavy ions – and analyzing in return the effects of their interaction with the atoms of the solid. These effects result from the transfer of energy from the primary particles to the atoms of the solid during collisions which, in most cases, can be considered as binary.

Based on this energy transfer, there are two main ways of chemically identifying an atom. The first is to link the loss of energy of the primary particle to an interaction characteristic of the target atom, while the second is to follow the effects of relaxation of the excited atom. This relaxation is in fact accompanied by the emission of secondary particles whose nature and energy make it possible to identify the emitting atom. There are thus two main approaches to microanalysis, both highly complementary in certain respects.

Microanalysis is one of the many methods of chemical characterization of elements that have been developed in the wake of the Castaing electron microprobe over the last thirty years. Today, it is one of the major tools for understanding condensed matter in many fields of science. When performed by scanning a beam of primary particles across the surface of a sample, from close up to close up, microanalysis enables the sample to be chemically mapped.

The microanalysis methods discussed in this article have been grouped into three main families, based on the nature of the primary particles used (Tables 1 , 2 and 3 ). These methods have been the subject of numerous individual descriptions, which can be found in the articles of this treatise:

• Electron energy loss spectroscopy in solids ;

• Nuclear microprobe [P 2 563] ;

• Auger electron spectroscopy