Si epitaxial growth on Br-Si(100): How steric repulsive interactions influence overlayer development

Abstract

Scanning tunneling microscopy results show the consequences of Si adatom deposition onto Br-saturated $\mathrm{Si}(100)\text{\ensuremath{-}}(2\ifmmode\times\else\texttimes\fi{}1)$. Those adatoms undergo an exchange reaction with Br and they are immobile at room temperature. In the low coverage regime, annealing to $650\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ leads to dimerization, limited ordering, and the formation of short Si chains. Adatom capture by those chains produces features of even and odd numbers of atoms. Annealing at $700\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ eliminates the odd chains, but diffusion is highly constrained by Br site blocking. With subsequent Si depositions, there is further nucleation of chains and chain growth. The local patterning of the Si chains reveals the influence of the Br steric repulsive interactions as out-of-phase structures were favored over in-phase structures around any given chain. Eventually, $(3\ifmmode\times\else\texttimes\fi{}2)$ adlayer patches develop. Second layer chains appear after the deposition of $\ensuremath{\sim}0.3\phantom{\rule{0.3em}{0ex}}\mathrm{ML}$, with layer-2 nucleation at antiphase domain boundaries. Bromine loss was observed, even at $650\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, and it is probably tied to the weaker bonding to single isolated Si adatoms.