DESIGN OF AN ELECTRON SPECTROMETER FOR AUTOMATED PHOTOELECTRON DIFFRACTOGRAM IMAGING OVER PI-STERADIANS

An electron spectrometer is presented which has been designed and buil t for the fast automated acquisition of photoelectron diffraction data over pi steradians above single crystal surfaces. The principle featu res include the use of externally-selectable stainless steel channel a rrays in front of the electron optics for high accuracy definition of the analyzer acceptance angle, a five channeltron detection system all owing the determination of the photocurrent from a given photoemission core level or Auger transition without changing the analyzer energy, a sample holder with heating and cooling capabilities which has been d esigned for very high (<0.1 degrees) angular control around both the p olar and azimuthal rotation axes, and an automated data acquisition sy stem to perform the angular scanning, collect the data, and represent it in the form of photoelectron 'diffractograms'. These data provide a chemically specific visualization of interatomic directions in the fi rst few atomic layers of the system of interest and can be used to ima ge intra-molecular bonds of molecules deposited on surfaces, follow th e epitaxial growth of one substance on the ordered surface of another, or study interdiffusion at interfaces.