Ground state of theSn/Ge(111)−3×3surface and its electron-beam-induced disordering

Abstract

Low-energy electron diffraction (LEED) studies at 14 K revealed that the ground state of the $\text{Sn}/\text{Ge}(111)\text{\ensuremath{-}}3\ifmmode\times\else\texttimes\fi{}3$ surface is the so-called one-Sn-up and two-Sn-down (1U2D) structure. The electron beam in the LEED observation was found to disorder the 1U2D structure below $\ensuremath{\sim}40\text{ }\text{K}$. Cross sections for the structural change suggest that an interband transition between Sn-derived surface state bands becomes the trigger for the structural change. A mechanism of the excitation-induced structural change activated below $\ensuremath{\sim}40\text{ }\text{K}$ is discussed.