Browsing by Subject "68.65.Ac"

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Open Access
Atomic structure of the √3 × √3 phase of silicene on Ag (111)
(American Physical Society, 2014-07-28) Cahangirov, S.; Özçelik, V. O.; Xian, L.; Avila, J.; Cho, S.; Asensio, M. C.; Çıracı, Salim; Rubio, A.
The growth of the 3√×3√ reconstructed silicene on Ag substrate has been frequently observed in experiments while its atomic structure and formation mechanism is poorly understood. Here, by first-principles calculations, we show that 3√×3√ reconstructed silicene is constituted by dumbbell units of Si atoms arranged in a honeycomb pattern. Our model shows excellent agreement with the experimentally reported lattice constant and STM image. We propose a new mechanism for explaining the spontaneous and consequential formation of 3√×3√ structures from 3×3 structures on Ag substrate. We show that the 3√×3√ reconstruction is mainly determined by the interaction between Si atoms and have weak influence from Ag substrate. The proposed mechanism opens the path to understanding of multilayer silicon. ©2014 American Physical Society
Open Access
Silicite: the layered allotrope of silicon
(American Physical Society, 2014) Cahangirov, S.; Özçelik, V. O.; Rubio, A.; Çıracı, Salim
Based on first-principles calculations, we predict two new thermodynamically stable layered-phases of silicon, named as silicites, which exhibit strong directionality in the electronic and structural properties. As compared to silicon crystal, they have wider indirect band gaps but also increased absorption in the visible range making them more interesting for photovoltaic applications. These stable phases consist of intriguing stacking of dumbbell patterned silicene layers having trigonal structure with root 3x root 3 periodicity of silicene and have cohesive energies smaller but comparable to that of the cubic diamond silicon. Our findings also provide atomic scale mechanisms for the growth of multilayer silicene as well as silicites.