Electronic properties of solid surfaces

Since the beginning of the industrial revolution, the surfaces of materials have been of great practical interest, being the seat of important phenomena such as corrosion, heterogeneous catalysis, thermo-ionic emission from the filaments of light bulbs and electronic vacuum tubes.... By applying the kinetic theory of gases, it can in fact be shown that all the reactive sites on a clean surface at time t ₀ are visited by an atom or molecule from the ambient atmosphere in about a single microsecond. As the best accessible voids have long remained in the millibar range, the surfaces studied were, at room temperature, mostly covered and masked by adsorbed layers of atoms and molecules of unknown nature. In the absence of advanced vacuum production techniques, atomically clean surfaces could only be formed at very high temperatures in favorable cases where the adsorbates evaporated. Thus, as early as 1927, a few years after de Broglie had formulated the hypothesis that particles of matter possessed a wave-like character, Davisson and Germer, working at the Bell Telephone laboratories, were able to demonstrate the existence of diffraction patterns when low-energy electrons were backscattered by the surface of a nickel film. For this experimental confirmation of the wave-corpuscle duality, Davison was awarded the Nobel Prize in Physics in 1937, along with Thomson, for the discovery of "electron waves". Since the 1970s, very high vacuums of the order of 0.1 picobar (the ultra-high-vacuum or UHV domain) have been routinely produced in the laboratory, making it possible to prepare surfaces that are very well characterized at atomic level, whether clean or deliberately coated with an adsorbate with an accuracy of a fraction of a monolayer .

With the advent of the near-field microscopies invented by Binnig and Rohrer in the 1980s, physicists acquired the ability to visualize the topography and atomic structure of surfaces in direct space with sub-angstrom precision. This remarkable tool is complemented by a whole range of surface characterization techniques, less local but equally powerful probes giving access to atomic and chemical composition and crystalline structure, the best-known of which are Auger electron spectroscopy (AES), slow or fast electron diffraction (LEED, RHEED), photoelectron spectroscopy (UPS, XPS, XPD).... Thus, the last decades of the twentieth century witnessed an unprecedented boom in the science of surfaces and interfaces between two volumetric phases, also stimulated by advances in vacuum techniques, and materialized, among...