Structure of silicene on a Ag(111) surface studied by reflection high-energy positron diffraction

The structure of silicene fabricated on a Ag(111) surface was determined using reflection high-energy positron diffraction with a linac-based brightness-enhanced intense positron beam. From the rocking curve analysis, the silicene was verified to have a buckled structure with a spacing of $0.83\phantom{\rule{0.28em}{0ex}}\AA{}$ between the top and the bottom Si layers. The distance between the bottom Si layer in the silicene and the first Ag layer was determined to be $2.14\phantom{\rule{0.28em}{0ex}}\AA{}$. These results agree with the theoretically predicted values from a previous study [Phys. Rev. Lett. 108, 155501 (2012)] within an error of $\ifmmode\pm\else\textpm\fi{}0.05\phantom{\rule{0.28em}{0ex}}\AA{}$.