SURFACE CRYSTALLOGRAPHY OF COSI2(111) DETERMINED BY DYNAMIC LOW-ENERGY ELECTRON-DIFFRACTION

The surface crystallography of bulk CoSi2(111) has been studied by low -energy electron diffraction. Measurements using primary-electron ener gies between 60 and 400 eV indicate that the surface is terminated by one Si layer above the first Co layer. Excellent agreement between the measured I-V curves and the calculated ones has been achieved with a model in which the interlayer spacing between the top (Si) and the sec ond (Co) layer is contracted by 0.09 angstrom, the spacing between the second (Co) and third (Si) layer is expanded by 0.02 angstrom, and th e spacing between the third (Si) and fourth (Si) layer is contracted b y 0.02 angstrom, with a Pendry r-factor of 0. 14.