Monolayer Physics

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9876763VilchesThis is a low temperature physics project dealing with helium adsorbed on solid surfaces. Various phases of quasi two-dimensional (2-d) matter, as occurring in films adsorbed on solid surfaces, are studied with thermodynamic and neutron scattering techniques. Liquid mixtures of 3He and 4He are measured below 0.2K to search for 2-d phase separation, and solid mixtures of D2-Ne are investigated between 2K and 20K to search for and study mixing, solidification, and 2-d eutectic points. New adsorbing surfaces are developed to explore changes in the freezing point of 2-d H2 which may lead to a new superfluid. Neutron scattering measurements on solid films containing deuterium and/or liquid films with deuterium hydride complement the thermodynamic measurements yielding the structure of solids and the mobility of liquids. The fast freezing of relatively thick uniform films explores the parameters which control the supercooling of liquids.%%%This low temperature physics project studies gaseous, liquid, and solid films, one to a few atomic or molecular layers thick, formed by atoms and/or molecules which wet solid surfaces. Results of measurements yield information on atomic mobilities, mixing and unmixing of different components, fabrication of new surfaces to produce mobile films, wetting of surfaces by certain fluids, and supercooling in pure and mixture liquid films. Thermodynamic measurements are carried out by graduate and undergraduate students at the University of Washington with experiments designed and built in house, while neutron scattering measurements are done at Saclay and Grenoble in collaboration with foreign scientists. Graduate students participate in the international experiments. This work trains students in refrigeration, modern data acquisition methods, high vacuum technology, measurements on very small samples (nanotechnology), and surface analysis tools. ***