Quantitative scanning tunneling spectroscopy of non-polar III-V compound semiconductor surfaces

The Greek philosopher Democritus (460-370 BC) and his mentor Leucippus are said to have been the first who introduced the theory of atomism.[1] They proposed that the universe is composed of indivisible elements (atomos) and void, only. The concept was based upon philosophical considerations only. First scientic approaches that employ atomic models, came up in the 18th and 19th century. Especially the development of the kinetic theory of gases, which was motivated by Bernoulli in 1738,[2] developed by Maxwell (1860),[3] and generalized by Boltzmann (1872),[4] represents a milestone for the acceptance of the hypothesis of atoms and molecules, since the macroscopic properties of gases where related to the microscopic motion of a many particle system. In general, the experimental observation of the Brownian motion of particles in a uid and the theoretical description of this phenomenon, given by Einstein in 1905,[5] is considered as first evidence for the existence of molecules and atoms. Nevertheless, no one had ever observed a single atom at that time. With the development of modern non-optical microscopes, mankind was enabled to take a look at the atomic world in real space for the first time in more than 2200 years of history of the atom: Shortly after the discovery of magnetic lenses, the electron microscope was invented by Ruska and Knoll in 1931.[6] However, great effort was still needed to overcome spherical and chromatic aberration effects and hence, first images of single atoms where obtained in the early 70s.[7] Five years after the construction of the first electron microscopes, in 1936, Muller invented the feld ion microscope[8, 9] and 20 years later he had managed to improve the resolution of this device so far that individual atoms of a sharp tungsten tip became visible.[10] Thus, Muller is said to be the first person who has ever seen an atom. Things dramatically changed with the invention of the scanning tunneling microscope by Binnig and Rohrer in 1981.[11, 12] This technique provided atomic resolution over large regions right from the beginning