Correlation between Adatom-Adatom Pair Interaction and Adlayer Superstructure Formation: Si on W {110}

Pair energies for Si adatoms on the W{110} for several bond lengths were obtained by direct field-ion—microscopy observations. Maximum binding occurred at a distance $\sqrt{2}a$ in the [$1\overline{1}0$] and maximum antibinding at $a$ in the [001]; $a$ is the lattice constant. From the data, the two-dimensional binding energy per adatom in an adlayer can be calculated. The $[\frac{2\sqrt{2}}{\sqrt{3}}\times \frac{4}{\sqrt{3}}]R35.26°$ superstructure has the lowest energy. Our search for a superstructure formation by thermal equilibration of Si adatoms confirmed this prediction.