Electron Spectroscopy
Introduction
Electron spectroscopies analyze the electrons
that are ejected from a material for qualitative or semi-quantitative analysis.
In general an excitation source such as X-rays or electrons will eject
an electron from an inner-shell orbital of an atom. Detecting photoelectrons
that are ejected by X-rays is call X-ray photoelectron
spectroscopy (XPS) or electron spectroscopy for chemical analysis (ESCA).
Detecting electrons that are ejected from higher orbitals to conserve energy
during electron transitions is called Auger electron
spectroscopy (AES). These electron processes are described below. Ejected
electrons can escape only from a depth of approximately 3 nm or less, making
electron spectroscopy most useful to study surfaces of solid materials.
Depth profiling is accomplished by combining an electron spectroscopy with
a sputtering source that removes surface layers.