Silicene multilayers on Ag(111) display a cubic diamondlike structure and a $\surd 3\times \surd 3$ reconstruction induced by surfactant Ag atoms

The structure of silicene multilayers grown on $\mathrm{Ag}\left(111\right)$ and the nature of their $\sqrt{3}\times \sqrt{3}R{30}^{\circ }$ reconstruction were studied by low-energy electron diffraction, Auger spectroscopy, and optical reflectance methods. It is shown that the surface reconstruction is induced by a surfactant layer of silver atoms during the growth of the silicon film and is not due to pristine Si. The Si film displays the optical characteristics of bulk cubic diamondlike Si, which indicates that it is not formed by any other allotropic phase of Si, which does not exist in nature, whether it is stacking of silicene layers, or “silicite.”

Figure 1

(a) Evolution of the normalized intensities of the Ag MNN (black continuous line/dots) and Si LVV (red dotted line/squares) Auger transitions during growth at 200 K (symbols) and 473 K (lines). (b) LEED diagram for 10 ML grown at 503 K $(E=80\mathrm{eV})$ Unit cells of $\mathrm{Ag}\left(111\right)$ and $\mathrm{Si}\left(111\right)-\sqrt{3}$ domains are drawn in black, blue, and red, respectively.

Figure 2

Differential reflectance spectra. Red circles: experiment. Continuous lines: calculations for different dielectric functions of the 2.1-nm silicon film. Blue (1): silicene stacking; green (2): silicite; purple (3): a-Si; black (4): cdSi; red (5): half cdSi and a-Si. The curves have been shifted upward for a better visualization.

Figure 3

Thermoreflectance spectra. Circles: experiments; red: 2.1-nm Si/Ag; black: bulk Si; blue: bulk Ag. Continuous lines: calculations for different dielectric functions of the 2.1-nm silicon film on Ag (same as in Fig. 2). For spectra (1) and (2), the dashed lines are the spectra amplified by a factor of 7. The curves have been shifted vertically for a better visualization.