Name Ernst Bauer | Role Physicist | |
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Education Ludwig Maximilian University of Munich Books Surface Microscopy with Low Energy Electrons, Interactions on Metal Surfaces | ||
Ernst G. Bauer (born 27 February 1928) is a German-American physicist. He is known for his studies in the field of surface science. His most notable contributions are his work on establishing thin film growth and nucleation mechanisms, and his invention in 1962 of the low energy electron microscope. He is currently Distinguished Research Professor Emeritus at the Arizona State University.
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Biography
Ernst Bauer studied at the Universität München, Germany, where he received his MS (1953) and PhD (1955) degrees in physics. In 1958 he moved to the Michelson Laboratory in China Lake, California, where he became the Head of the Crystal Physics Branch and a U.S. citizen. He assumed the position of Professor and Director of the Physics Institute at the Technical University Clausthal, Germany, in 1969. He was appointed Distinguished Research Professor in 1991 at the Arizona State University. He continued his research activity in Germany until 1996. Since 1996 he is working full-time at the Arizona State University, and since 2010 he is Distinguished Research Professor Emeritus still working full-time in ASU.
Thin film growth
Ernst Bauer has contributed to the field of epitaxy and film growth since the mid-1950s. He started his scientific career in München with the study of the growth and structure of antireflection layers with electron microscopy and electron diffraction. His PhD thesis was concerned with the structure and growth of thin evaporated layers of ionic materials and was the first systematic extensive study of epitaxial and fiber orientation growth combining electron microscopy and electron diffraction. This experimental work stimulated a basic contribution to the theory of epitaxy. He derived in 1958 a classification of the basic thin film growth modes, which he called Frank-van der Merwe (layer-by-layer growth), Volmer-Weber (island growth) and Stranski-Krastanov growth (layer+island growth). His thermodynamic criterion and terminology are used worldwide today. In the same year Ernst Bauer's book on "Electron diffraction: theory, practice and application" appeared.
Surface science and LEEM, SPLEEM, SPELEEM
Soon after his arrival at the Michelson Laboratory in California, surface science was born. He was involved early in it in order to understand thin film phenomena. In this period he started in situ thin film growth studies by conventional electron microscopy, UHV reflection electron diffraction, LEED and Auger electron spectroscopy. He was one of the first to recognize the importance of exchange, polarization, multiple scattering, and of the energy dependence of inelastic scattering of very slow electrons in LEED studies of surfaces, and he took them into account theoretically. The importance of adsorption on the initial growth of thin films led him also to adsorption studies. In these early years of UHV technique and surface science much of the work went into technological and methodological development. The invention in 1962 of the Low Energy Electron Microscope (LEEM) was stimulated by a scientific dispute with Lester Germer about the difficulties in the interpretation of low energy electron diffraction (LEED) patterns. Ernst Bauer realized that electron microscopy using the diffracted electrons for imaging would be extremely important for the future of the surface science. He constructed the first LEEM prototype and reported it at the Fifth International Congress for Electron Microscopy in 1962.
At the Technical University Clausthal Ernst Bauer built up a broadly based surface science group encompassing a large variety of electron and ion beam techniques as well as optical methods. The quantitative interpretation of thermal desorption spectra was developed with the goal to obtain information on the interactions in adsorption layers. Work function measurements were developed and used for the determination of the thermodynamic properties of two-dimensional systems with attractive lateral interactions. For the study of two-dimensional systems with repulsive or oscillatory interactions, his group developed LEED-diffractometry that allows the determination of critical exponents in chemisorbed layers with accuracy comparable to that achieved with x-rays in physisorbed layers. He developed electron stimulated desorption (ESD) and static SIMS for the study of adsorbed layers and ultrathin films on single crystal surfaces; alkali ion scattering (ISS) for structural analysis of surfaces; field ion microscopy (FIM) of single atoms and clusters; UHV-SEM studies of surface melting.
In this period (in 1985) the LEEM came also to fruition. In the late 1980s early 1990s Ernst Bauer extended the LEEM technique in two important directions by developing Spin-Polarized Low Energy Electron Microscopy (SPLEEM) and Spectroscopic Photo Emission and Low Energy Electron Microscopy (SPELEEM). The combination of these methods now allows a comprehensive (structural, chemical, magnetic and electronic) characterization of surfaces and thin films on the 10 nm scale.
Numerous LEEM instruments are now installed and operating in many laboratories and synchrotron radiation facilities around the world. An important recognition for Ernst Bauer’s efforts in the field of surface microscopy is the increasing number of the scientists involved in LEEM research, which is reflected in the organization of bi-annual LEEM/PEEM workshops. His work directly or indirectly impacts many areas of modern materials science: surfaces, thin films, electronic materials, and instrumentation. The invention and development of surface microscopy with slow electrons has revolutionized the study of surface science and thin film science.
Ernst Bauer has authored or co-authored more than 460 publications (among them 85 review papers and book chapters) and two books: "Electron Diffraction: Theory, Practice and Applications", 1958 (in German) and “Surface Microscopy with Low Energy Electrons”, 2014.