Photoemission and Auger Spectroscopy

X-ray photoelectron spectroscopy (XPS) Ultraviolet photoelectron spectroscopy (UPS) Auger electron spectroscopy (AES) 

Photoemission spectroscopy is based on the photoelectric effect a sample that is irradiated with light of sufficiently small wavelength emits electrons. The number of photoelectrons depends on the light intensity, and the energy of the electrons on the wavelength of the light. 

It was a half-century later before the photoelectric effect was applied in spectroscopy. As described by Ertl and Kiippers [5], three parallel developments took place  

The development of Auger electron spectroscopy (AES) has its own history. In 1925, Pierre Auger discovered that photographic plates exposed to hard X-rays exhibited traces due to electrons [11]. He interpreted them as the result of a relax- 

In hindsight, it was Hertz who, unknowingly, reported the first photoemission experiments in 1887, when he noticed that electrical sparks induced the formation of a second spark in a variety of samples [1], Hertz correctly recognized that the effect was due to UV light generated by the first spark, but he did not understand the nature of the induced spark. In fact he could not have done so, because the electron had not yet been discovered. About ten years later Thomson identified the radiation in 

Hertz s experiment as being caused by electrons [2], The phenomenon of photoemission has played an important role in confirming Einstein s famous postulate, published in 1905, that light is quantized in photons of energy hv[3J. We refer to Margaritondo [4] for an interesting review on the early days of the photoelectric effect. 

XPS and AES are now among the most often applied techniques in the characterization of solid surfaces [15]. UPS is a typical surface science method best suited for fundamental studies on single crystals. All three spectroscopies give surface sensitive information. 

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