Surface roughness and LEED crystallography: Analysis of flat and vicinal W(110)

Abstract

Low-energy electron diffraction intensity vs voltage (LEED I-V) measurements and analysis are used to determine the multilayer surface relaxation of W(110). Measurements and analysis are presented for both flat and vicinal surfaces, demonstrating that surface roughness leads to only small errors in LEED structure determinations. Flat, clean W(110) exhibits first-(d{sub 12}) and second-(d{sub 23}) layer relaxations of {minus}3.0{plus_minus}1.3{percent} and +0.2{plus_minus}1.3{percent}, respectively, relative to the bulk lattice spacing d{sub 0}=2.237h{Angstrom}. This experimentally determined surface relaxation of W(110) is compatible with a recent combined density-functional theory calculation and LEED study [M. Arnold, G. Hupfauer, P. Bayer, L. Hammer, K. Heinz, B. Kohler, and M. Scheffler, Surf. Sci. {bold 382}, 288 (1997)]. Surface roughness (in the present case, uniform atomic height steps) is found to produce a small apparent increase in the measured value of d{sub 12} when determined using standard (flat surface) LEED I-V methodology. However, for low step densities ({lt}20 atoms/step) the apparent change in d{sub 12} is small compared to other sources of error, so it is unlikely that surface roughness is a significant source of error in LEED structure determinations. {copyright} {ital 1999} {ital The American Physical Society}