High Resolution Low Energy Electron Diffraction Studies of Surface and Overlayer Ordering

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The fundamental physical laws that govern the equilibrium and non-equilibrium collective phenomena of a clean surface near the melting temperature, and of an adsorbed overlayer will be investigated using the high resolution low-energy electron diffraction technique (HRLEED). They propose to study the change of structural and thermodynamic properties of clean metal surfaces during surface roughening/melting using HRLEED. Research efforts will include: (1) identification of the nature of the disorder and measurement of the density of defects generated at the surface near the melting temperature; (2) measurement of the short range correlations and critical exponents associated with the surface roughening/melting phase transition. For an adsorbed overlayer, research efforts will include (1) quantitative determination of overlayer domain growth during the relaxation of statistical mechanical states far from equilibrium; (2) testing of 2-D kinetic scaling theory and universality for an overlayer with ground state degeneracy greater than two; and (3) effects of impurities (random fields) on 2-D phase transitions and domain growth of a system with ground state degeneracy greater than two. The results of this research will not only help us gain insight into the fundamental power, scaling and growth laws which describe the clean surface and adsorbed overlayer ordering, but will also increase our knowledge in controlling important practical processes such as crystal growth and heterogeneous catalysis.