arXiv subjects

P. M. He

Publications and source records attributed to P. M. He.

2 recordsLinked to original sources

arXiv2007

Graphene on metal surface: gap opening and n-doping

Graphene grown on metal surface, Cu(111), with a boron nitride(BN) buffer layer is studied for the first time. Our first-principles calculations reveal that charge is transferred from the copper substrate to graphene through the BN buffer layer which results in a n-doped graphene in the absence of a gate voltage. More importantly, a gap of 0.2 eV which is comparable to that of a typical narrow gap semicondutor opens just 0.5 eV below the Fermi-level at the Dirac point. The Fermi-level can be easily shifted inside this gap to make graphene a semiconductor which is crucial for graphene-based electronic devices. A graphene based p-n junction can be realized with graphene eptaxially grown on metal surface.

cond-mat.mtrl-sci↗

arXiv2007

Ti-rich and Cu-poor grain-boundary layers of CaCu$_3$Ti$_4$O$_{12}$ detected by x-ray photoelectron spectroscopy

Cleaved and polished surfaces of CaCu$_3$Ti$_4$O$_{12}$ ceramics have been investigated by x-ray photoelectron spectroscopy (XPS) and energy dispersive x-ray spectroscopy (EDX), respectively. While EDX technique shows the identical CaCu$_3$Ti$_4$O$_{12}$ stoichiometry for the two surfaces, XPS indicates that the cleaved surface with grain-boundary layers is remarkably Ti-rich and Cu-poor. The core-level spectrum of Cu 2$p$ unambiguously shows the existence of monovalent copper only for the cleaved surface. Possible grain-boundary structure and its formation are discussed.

cond-mat.mtrl-sci↗