Inhibiting molecular array formation on Si(111)-7×7using site-selective Ge/Si exchange

Abstract

The Si(111)-$7\ifmmode\times\else\texttimes\fi{}7$ surface reconstruction can be used to template an array of mesitylene (1,3,5-trimethyl-benzene) molecules in which each molecule bridges a corner Si adatom and a neighboring Si rest atom. The molecules adsorb in corner sites to minimize a weak steric interaction associated with nearest-neighbor bridging sites. We demonstrate that the formation of the molecular array can be blocked by adding submonolayer amounts of Ge to the surface. The Ge atoms block the formation of the array because they substitute preferentially for Si adatoms located in corner sites, and the Ge--C bond strength is $\ensuremath{\approx}$0.8 eV weaker than the Si--C bond strength.