Even though both graphene and silicene have ultra-high carrier mobility, their zero band gap nature make them cannot be directly used in high performance field effect transistors (FET). Opening a band gap without degrading their high carrier mobility is vital for graphene and silicene to their application in nanoelectronics. Based on their previous works of building the BN/graphene/BN sandwich structure (NPG Asia Materials 4, e6(2012)) and applying external vertical electric field to silicene (Nano Letters 12, 113(2012)) to open a band gap, recently the Computational Materials Group led by Prof. Jing Lu at School of Physics, Peking University proposed a new scheme to open a band gap in silicene --- single side surface adsorption of metal atoms on silicene. Their density functional theory calculations predict that a band gap is opened in silicene by single-side adsorption of alkali atom as a result of sublattice or bond symmetry breaking. The band gap size is controllable by changing the adsorption coverage, with an impressive maximum band gap up to 0.50 eV. The ab initio quantum transport simulation of a bottom-gated FET based on a sodium-covered silicene reveals an on/off current ratio up to 108, meeting the requirement for the high performance logic devices. Therefore, a way is paved for silicene as the channel of a high-performance FET.

This work was published in the new journal of Nature Publishing Group 《Scientific Reports》 (Tunable and sizable band gap in silicene by surface adsorption, Scientific Reports 2, 853 (2012); http://www.nature.com/srep/2012/121114/srep00853/full/srep00853). The first author of this paper is Ruge Quhe, a PhD student from Academy for Advanced Interdisciplinary Studies and School of Physics in Peking University. The collaborators include Prof. Gao Zhengxiang and Prof. Yu Dapeng from School of Physics, Peking University.

The work was supported by the National 973 Projects, Program for New Century Excellent Talents in University of MOE of China, NSFC, and the State Key Laboratory for Artificial Microstructure and Mesoscopic Physics, Peking University.