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Highlight works in silicene

(1). Evidence for Dirac Fermions in a Honeycomb Lattice Based on Silicon,
Lan Chen, Cheng-Cheng Liu, Baojie Feng, Xiaoyue He, Peng Cheng, Zijing Ding, Sheng Meng, Yugui Yao, and Kehui Wu,
Physical Review Letters 109, 056804(2012).[PDF]

Group IV (Si, Ge) analogs of graphite have been discussed for a long time even before the synthesis of isolated graphene, and recently there has been renewed interest in this topic due to the novel concepts and applications brought on by graphene. The silicon version of graphene in which Si atoms replace C atoms in a two-dimensional honeycomb lattice is named silicene. Theoretical calculations show that silicene also has graphenelike electronic band structure, supporting charge carriers behaving as massless Dirac fermions . Compared with graphene, silicene has a larger spin-orbit coupling strength, which may lead to a larger energy gap at the Dirac point and favor a detectable quantum spin Hall effect . Currently a quantum spin Hall effect has been realized only in HgTe-CdTe quantum wells and further studies have been hindered by the challenging material preparation. Easy preparation and compatibility with silicon-based nanotechnology make silicene particularly interesting for applications like quantum spin Hall effect devices.

As the theoretical studies on silicene are rapidly increasing, the major challenge in this field is now the preparation of high quality silicene films. However, to date, there is still no solid evidence for the observation of a silicene film. Recently, we have made significant progress in the preparation of silicene and investigation on their electronic properties. After we successfully obtained monolayer and multilayer silicene films on Ag(111), we perform STM/STS using a fully home-made low temperature (4K) scanning tunneling microscopy/spectroscopy. We found that the electronic property measured by STS is consistent with theory very well. For example, quasiparticle interference (QPI) patterns suggesting intervalley and intravalley scattering of charge carriers were observed, and a linear energy-momentum dispersion relation and a large Fermi velocity were derived. These results unambiguously prove the existence of Dirac fermions in silicene, and provide a solid basis for further studies on the electronic property and device applications of silicene

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(2) Evidence of Silicene in Honeycomb Structures of Silicon on Ag(111),
Baojie Feng, Zijing Ding, Sheng Meng, Yugui Yao, Xiaoyue He, Peng Cheng, Lan Chen, and Kehui Wu,
Nano Letters 12,3507(2012).[PDF]

We performed systematic study of the self organized superstructures formed by submonolayer silicon grown on Ag(111), by STM and scanning tunneling spectroscopy (STS). They found that, depending on the substrate temperature and silicon coverage, several monolayer superstructures can form on Ag(111). These superstructures are distinct from any known surface structures of bulk silicon and are characterized by honeycomb building blocks and structures. At sufficiently high temperature and Si coverage, monolayer and multilayer silicene films were grown. This work provides a complete understanding of the structure evolution of Si on Ag(111), which is desirable for fabrication of high-quality silicene and exploring its novel physics and applications.

 

Kehui Wu Group Dec.2012 , All rights reserved