Structural evolution of Bi thin films on Au(111) revealed by scanning tunneling microscopy

Abstract

We present the structural evolution of Bi on Au(111) from monolayer to multilayer regimes explored mainly by scanning tunneling microscopy. At the monolayer regime, Bi clusters distribute homogeneously to make an array with $5\phantom{\rule{4pt}{0ex}}\ifmmode\times\else\texttimes\fi{}\phantom{\rule{4pt}{0ex}}5$ periodicity. Further increase of the coverage converts these clusters to the two-dimensional periodic $(\sqrt{37}\ifmmode\times\else\texttimes\fi{}\sqrt{37})\mathrm{R}25.{3}^{\ensuremath{\circ}}$ and $(\mathrm{p}\phantom{\rule{4pt}{0ex}}\ifmmode\times\else\texttimes\fi{}\sqrt{3})$ structures. We propose a model of the $(\sqrt{37}\ifmmode\times\else\texttimes\fi{}\sqrt{37})\mathrm{R}25.{3}^{\ensuremath{\circ}}$ structure based on the STM measurements and density-functional theory calculations. In the multilayer regime, superstructures at first appear with long-range periodicities arising from the moir\'e structures due mainly to the stacking of Bi layers. Then, the thicker films grow whose lattice constants are close to those of the (110) surface of rhombohedral Bi crystal. The Bi(110) films of more than 60 layers grow stably. Thus, this system provides a good stage for further investigation of the peculiar electronic properties of Bi(110).