Formation of step structures by As deposition on a double-domain Si(001) substrate.

Abstract

We report the rich variation in the evolution of step structures of vicinal Si(001) upon As deposition, studied by scanning tunneling microscopy. Clean 1\ifmmode^\circ\else\textdegree\fi{} vicinal Si(001) exhibits a typical double-domain surface that consists of single-monolayer-height steps called ${\mathit{S}}_{\mathit{A}}$ and ${\mathit{S}}_{\mathit{B}}$. On the other hand, As-deposited surfaces show drastic changes in the step structures depending on the substrate temperature during the deposition and the As coverage: At relatively low temperatures (500 \ifmmode^\circ\else\textdegree\fi{}C), the surface becomes nearly a single domain by the deposition of a half monolayer and two-dimensional islands appear after more As is deposited. At medium temperatures (600 \ifmmode^\circ\else\textdegree\fi{}C), however, one-monolayer As deposition makes the surface nearly a single domain, consisting of double-monolayer-height steps called ${\mathit{D}}_{\mathit{B}}$. At high temperatures (700 \ifmmode^\circ\else\textdegree\fi{}C), a double-domain surface is formed containing triple-monolayer-height steps where the dimer rows in the upper terrace are perpendicular to the step edge. These various surface step structures are explained by kinetic effects of atomic movement during deposition and desorption and by the energetically stable shapes of Si(100)-As in equilibrium.