Milli-Electron Volt Energy Resolution Photoemission Studies of Solids

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Very high energy resolution (less than 5meV at count rates of 1kHz) photoemission studies of solids at low temperatures will be undertaken on a recently built instrument. These parameters are a significant improvement over previously published work on solid samples, and allows photoelectron spectroscopy to make contact with other experimental methods that study excitations with energies of order kT. Several specific experiments are proposed: Studies of the effects of the electron-phonon interaction on Fermi edges in angle integrated spectra, and on individual surface state dispersion at small binding energy in wide band metals such as copper will be undertaken; this will yield detailed information about the interaction between electrons and phonons at and near solid surfaces. Studies of emission from phosphorus donor levels in silicon for concentration ranges near the metal/insulator critical concentration will determine the one electron density of states and aid in understanding the competition between correlation and disorder in driving this transition. Studies of emission (peak dispersion and line shape) and of the band-gap in conventional and high temperature superconductors will help to determine the mechanism of superconductivity in these materials. %%% The purpose of this research is to bring the power and discrimination of a newly developed high resolution photoelectron spectrometer to bear on a number of current problems in materials physics. The improved resolution could impinge strongly on technological fields such as superconductivity and semiconductor device operation, as well as in various related areas of more fundamental interest. This research will extend the energy resolution of photoelectron spectroscopy by about an order of magnitude, permitting detailed studies of the electrons responsible for device operation. In particular, metal/insulator transitions in semiconductors, the origin of the energy gap in high temperature and conventional superconductors, and the interaction between electrons and atomic vibrations in more ordinary materials will be investigated.