Growth mechanism of silicene onAg(111)determined by scanning tunneling microscopy measurements andab initiocalculations

Abstract

Scanning tunneling microscopy has been used to real-time study the growth of silicene on $\mathrm{Ag}(111)$ in the 200--533-K temperature range. We show that the growth mode depends strongly on the deposition temperature $T$. At $T=300\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ and above, the formation of silicene results from the exchange between surface Ag atoms and Si atoms, which are inserted in the substrate top layer. Density functional theory calculations confirm that Si insertion is thermodynamically favored, and we propose an energetic model for explaining the observed growth processes as a function of $T$. For $T\ensuremath{\ge}400\phantom{\rule{0.16em}{0ex}}\mathrm{K}$, ordered structures are observed as soon as silicene domains are large enough. With increasing coverage, disordered and dotted phases progressively transform into stable $(\sqrt{13}\ifmmode\times\else\texttimes\fi{}\sqrt{13})R13.{9}^{\ensuremath{\circ}}$ and $(4\ifmmode\times\else\texttimes\fi{}4)$ structures.