L. Xu

Graphene grown out of diamond

Most applications of graphene need a suitable support substrate to present its excellent properties. But transferring graphene onto insulators or growing graphene on foreign substrates could cause properties diminishing. This paper reports the graphene growth directly out of diamond (111) by B doping, guided by first-principles calculations. The spontaneous graphene formation occurred due to the reconstruction of the diamond surface when the B doping density and profile are adequate. The resulting materials are defect free with high phase purity/carrier mobility, controllable layer number, and good uniformity, which can be potentially used directly for device fabrication, e.g., high-performance devices requiring good thermal conductivity.

Structural stability and electronic properties of alkaline-earth metal induced Si(111)-(3 × 2) surfaces

Alkaline-earth metal (Ca, Sr, and Ba) induced Si(111)-(3 × 2) honeycomb chain-channel (HCC) surfaces have been systematically studied by means of ab initio calculations. The large adsorption energy and anisotropic diffusion energy barriers ensure the high structural stability of the one-dimensional HCC structure. Electronic band structures and band-decomposed charge density distributions reveal that the first conduction band and the third valence band level are contributed by the surface Si and metal atoms, while the top first and second valence bands are caused by the bulk silicon atoms. These results identify a larger surface band gap of 1.65-1.68 eV and provide an excellent explanation for the recent experimental observations of a band gap of 1.7 eV for the Sr/Si(111)-(3 × 2) HCC surface.