CU(111) SURFACE RELAXATION BY VLEED

Very-low-energy electron diffraction (VLEED) intensities from a clean Cu(111) surface have been measured in detail in the energy range 15-10 0 eV by low-energy electron microscope (LEEM). This enabled the elimin ation of possible disturbances due to stray magnetic fields. Correspon ding theoretical I-V curves have been obtained in good agreement with experimental data when an image-type surface barrier and anisotropy of the electron attenuation were taken into account. The reliability fac tor analysis indicates a slight expansion of the topmost interatomic s pacing of Cu(111) relative to its bulk value.