Silicene, an allotrope of silicon synthesized recently, is similar to graphene in hexagonal lattice and ultrahigh mobilities (probably up to 105 cm2/(Vs) under some presumption). However, its buckled structure is crucially different from flat graphene sheet and leads to unique properties. By using ab initio calculations, Prof. Jing Lu, Zhengxiang Gao, and their undergraduate Zeyuan Ni predict that a vertical electric field is able to open a band gap in semimetallic single-layer buckled silicene and germanene with their ultrahigh mobilities preserved. The sizes of the band gap in both silicene and germanene increase linearly with the electric field strength. Ab initio quantum transport simulation of an h-BN-protected dual-gated silicene field effect transistor confirms that the vertical electric field opens a transport gap and a significant switching effect by an applied gate voltage is observed. Therefore, biased single-layer silicene and germanene can work effectively at room temperature as field effect transistors. This work is published on line in Nano Letters （DOI: 10.1021/nl203065e）.

This work was supported by the NSFC (grant no. 10774003), National 973 Projects (no. 2007CB936200, MOST of China), Fundamental Research Funds for the Central Universities, National Foundation for Fostering Talents of Basic Science (no. J0630311), and Program for New Century Excellent Talents in University of MOE of China.