Origin of ordered two-dimensional structure ofSi(337)−4×1transformed fromSi(5 5 12)−2×1

Abstract

Through combined studies using scanning tunneling microscopy (STM) and high-energy-resolution synchrotron photoemission, the origin of irreversible structural transformation from $\text{Si}(5\text{ }5\text{ }12)\text{\ensuremath{-}}2\ifmmode\times\else\texttimes\fi{}1$ to $\text{Si}(337)\text{\ensuremath{-}}4\ifmmode\times\else\texttimes\fi{}1$ with (113) facets has been investigated. From the C-dosed $\text{Si}(5\text{ }5\text{ }12)$ surface, it has been found by STM that the transformation from $(5\text{ }5\text{ }12)$ to (337) starts from a tetramer (T) row and a $\ensuremath{\pi}$-bonded $(\ensuremath{\pi})$ chain in the $(5\text{ }5\text{ }12)$ surface, and simultaneously the rest part of $(5\text{ }5\text{ }12)$ converts to T rows and $\ensuremath{\pi}$ chains, which will be transformed to (337) with additional Si atoms. By $\text{Si}\text{ }2p$ and $\text{C}\text{ }1s$ core-level photoemission studies using synchrotron radiation on the identical system, it has been confirmed that such an irreversible structural transformation is due to subsurface C atoms. If the (337) terrace is only composed of T rows and $\ensuremath{\pi}$ chains with a $2\ifmmode\times\else\texttimes\fi{}$ periodicity, the compressive stress exists so that the (337) terrace becomes unstable. However, subsurface C atoms release this compressive stress through breaking one-dimensional structures and induce a stable surface composed of $4\ifmmode\times\else\texttimes\fi{}1$ dotlike structures with additional Si atoms.