Structure of Silicene Grown on Ag(111)

The structure of silicene, the two-dimensional honeycomb sheet of Si, grown on Ag(111) was investigated by scanning tunneling microscopy (STM) and low-energy electron diffraction (LEED) combined with density functional theory (DFT) calculation. Two atomic arrangements of honeycomb configuration were...

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Published inApplied physics express Vol. 5; no. 4; pp. 045802 - 045802-3
Main Authors Lin, Chun-Liang, Arafune, Ryuichi, Kawahara, Kazuaki, Tsukahara, Noriyuki, Minamitani, Emi, Kim, Yousoo, Takagi, Noriaki, Kawai, Maki
Format Journal Article
LanguageEnglish
Published The Japan Society of Applied Physics 01.04.2012
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Summary:The structure of silicene, the two-dimensional honeycomb sheet of Si, grown on Ag(111) was investigated by scanning tunneling microscopy (STM) and low-energy electron diffraction (LEED) combined with density functional theory (DFT) calculation. Two atomic arrangements of honeycomb configuration were found by STM, which are confirmed by LEED and DFT calculations; one is $4{\times}4$ and the other is $\sqrt{13}{\times}\sqrt{13}$ R13.9°. In the $4{\times}4$ structure, the honeycomb lattice remains with six atoms displaced vertically, whereas the $\sqrt{13}{\times}\sqrt{13}$ R13.9° takes the regularly buckled honeycomb geometry.
Bibliography:(a) Topographic STM image ($22.7\times 15.1$ nm 2 ) of silicene on Ag(111) taken at 6 K with the tunneling current ($I$) of 0.2 nA and sample bias ($V$) of $-0.7$ V. The red and blue arrows show the direction of a unit vector of $\alpha$ and $\beta$ structures, respectively. The black arrows show three highly symmetric axes of Ag(111). Highly resolved topographic images of (b) $\alpha$ ($I = 0.2$ nA, $V = 0.5$ V) and (c) $\beta$ ($I = 0.3$ nA, $V = - 0.02$ V) phases taken at 6 K. Both image sizes are $3.8\times 3.8$ nm 2 . (a) $4{\times}4$ and (b) $4{\times}4+\sqrt{13}{\times}\sqrt{13}$ R13.9° LEED patterns of silicene on Ag(111) taken at room temperature with the kinetic energies of incident electron of (a) 47.7 and (b) 53.9 eV, respectively. The LEED patterns calculated for (c) $4{\times}4$ and (d) $4{\times}4 +\sqrt{13}{\times}\sqrt{13}$ R13.9° are shown for comparison. The red, blue, and black spots represent the ones originating from $4{\times}4$, $\sqrt{13}{\times}\sqrt{13}$ R13.9°, and $1{\times}1$ structures, respectively. Optimized structure models of (a) $4{\times}4$ and (b) $\sqrt{13}{\times}\sqrt{13}$ R13.9° silicene on Ag(111) determined by DFT calculations. Both top view and side view are illustrated. The small and large balls represent Si and Ag atoms, respectively. The Si atoms are classified by color depending on the vertical displacement. The blue and green Si atoms are lower and higher, respectively. (c) and (d) are the simulated STM images combined with the real STM results for $4{\times}4$ and $\sqrt{13}{\times}\sqrt{13}$ R13.9°, respectively.
ISSN:1882-0778
1882-0786
DOI:10.1143/APEX.5.045802