Finite size effects on reconstruction domains of tungsten(001) surfaces

Abstract

The size of reconstruction domains on low-temperature, clean W(001) and also hydrogen-covered W(001) have been studied for both planar and stepped surfaces through analysis of LEED intensities and beam shapes. The stepped surface with step edges parallel to the [110] has an average terrace width of ∼28 Å. For the low temperature, clean, planar surface the average equilibrium reconstruction domain size is ∼130 Å. On the stepped surface, ‘‘zig–zag’’ orientational domains with atomic displacements perpendicular to the steps are preferred and the domain size perpendicular to the steps is limited by the terrace width, while the size parallel to the steps is nearly the same as on the planar surface. Hydrogen-induced reconstruction domains for the commensurate phase are similar in size to the clean surface domains on the planar surface. On the stepped surface, the ‘‘dimer’’ domains are also limited by the terrace width perpendicular to the steps and are additionally limited parallel to the steps to approximately half their planar surface dimension. With increasing hydrogen exposure and the development of the incommensurate phase, the domain dimensions are observed to shrink to less than 12 Å before the transition to the (1×1)-H structure occurs on both planar and stepped surfaces.