Acquisition of a Low Energy Electron Microscope (LEEM)

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This project will provide a commercial Low Energy Electron Microscope (LEEM) to Arizona State University. It will be one of two such instruments located at Universities in the United States. The instrument will be located in the Physics building, next to the NSF supported Center for High Resolution Electron Microscopy, and will complement the scanning tunneling microscopes as well as the electron microscopes. Several features distinguish the LEEM from other microscopes: (a) it uses very low energy illuminating beam, about 10 eV; (b) the low beam energies are usually below the threshold of electron stimulated desorption and do practically no damage to the surface; (c) it uses a static rather than a scanning beam, and thus operates in a parallel detection mode which allows real-time imaging of surface kinetic processes at video rates with a lateral resolution of 5 nm. The surface science research group in the Department of Physics and Astronomy has proposed several experiments aimed at studying the dynamics of surface processes in real time, such as surface reconstructions and phase transitions induced by temperature change and/or adsorbate coverage, surface compound formation and epitaxial growth, step motions induced by externally applied stress, and influence of defect structure and defect density on nucleation and growth of thin films. Theoretical models and simulations of their observations in the LEEM will complement the experimental effort in order to achieve a full understanding of the surface processes.