An investigation of the YB66(100) surface

Scanning tunneling microscopy (STM), low energy electron diffraction (LEED) and impact collision ion scattering spectroscopy (ICISS) studies were perf ormed on the YB66(100) surface. By varying the scanning conditions in STM w e were able to identify two different surface structures: a regular square lattice with a lattice constant of 11.5 Angstrom For 4 V positive sample bi as and a more complex structure most likely consisting of interconnected B- 12 icosahedra for a negative ? V sample bias. A closer investigation of vac ancies and dislocations in the surface square lattice imaged with 4V positi ve sample bias indicates that this regular structure does not reflect the o rdering of the B-156 supericosahedra. In this context, a surface structure model is offered in which the channels between the giant B-156 supericosahe dra, that is, the yttrium atom sites, form the regular square lattice and d ecomposed B-156 units compose the irregular structure imaged with a -2 V sa mple bias. (C) 1998 Elsevier Science B.V. All rights reserved.