Structures of the As-deficient phase onGaAs(001)−(2×4)

Abstract

The atomic structures of the $\mathrm{GaAs}(001)\text{\ensuremath{-}}(2\ifmmode\times\else\texttimes\fi{}4)$ surface have been studied using scanning tunneling microscopy (STM), reflectance difference spectroscopy (RDS), and reflection high-energy electron diffraction (RHEED). While STM images from the $\ensuremath{\beta}$ phase show well-ordered $\ensuremath{\beta}2$ structures, the $\ensuremath{\alpha}$ phase consists of $(2\ifmmode\times\else\texttimes\fi{}4)$ structures with surface As dimers locally missing from the basic $\ensuremath{\beta}2(2\ifmmode\times\else\texttimes\fi{}4)$ units. Our RDS and RHEED analyses, together with STM observations, clearly show that the missing-dimer defect has local atomic geometry identical to the $\ensuremath{\alpha}2(2\ifmmode\times\else\texttimes\fi{}4)$ structure.