Interaction of electrons and positrons with solids: from bulk to surface in thirty years

Abstract

In 1963 electrons and positrons were regarded as probes of the bulk properties of solids via, e.g., energy-band theory, fast electron energy loss spectroscopy, and positronium decay. During the late 1960s it was recognized that at energies in the range 10 ⩽ E ⩽ 1000 eV,the inelastic collision mean free paths, λ, of electrons and positrons become comparable to atomic dimensions, i.e., λ ≈ 10 Å, so that the elastic reflection or emission of these particles from solids probes the properties of the uppermost few atomic layers. This recognition led to the development of core level spectroscopies (e.g., Auger electron spectroscopy, X-ray photoelectron spectroscopy) for surface compositional analysis in the 1960s, to the application of low-energy electron diffraction for quantitative surface structure determination in the 1970s, and to that of low-energy positron diffraction for surface structure analysis in the 1980s. In addition, in the 1960s it was recognized that resonant field emission through adsorbed species offers a quantitative spectroscopy of the single-electron excitation spectrum of these species: a discovery which presaged the use of photoemission spectroscopy for this purpose in the 1970s and the development of scanning tunneling spectroscopy in the 1980s. This article is an exposition of how the evolution of the understanding of the nature of electron (positron) solid interactions together with advances in ultrahigh vacuum instrumentation and semiconductor microelectronics led from the dawn of the surface science revolution in the 1950s and 1960s to the quantitative electron (positron) surface spectroscopies which are routinely deployed in the 1990s.