Showing papers by "Vincent Repain published in 2014"
TL;DR: Grain boundaries in epitaxial graphene on the SiC(000$\bar{1}$) substrate are studied using scanning tunneling microscopy and spectroscopy.
Abstract: Grain boundaries in epitaxial graphene on the SiC(000$\bar{1}$) substrate are studied using scanning tunneling microscopy and spectroscopy. All investigated small-angle grain boundaries show pronounced out-of-plane buckling induced by the strain fields of constituent dislocations. The ensemble of observations allows to determine the critical misorientation angle of buckling transition $\theta_c = 19 \pm~2^\circ$. Periodic structures are found among the flat large-angle grain boundaries. In particular, the observed $\theta = 33\pm2^\circ$ highly ordered grain boundary is assigned to the previously proposed lowest formation energy structural motif composed of a continuous chain of edge-sharing alternating pentagons and heptagons. This periodic grain boundary defect is predicted to exhibit strong valley filtering of charge carriers thus promising the practical realization of all-electric valleytronic devices.
33 citations
TL;DR: In this article, the structural and magnetic properties of self-organized CoxPt1−x nanostructures grown by codeposition at room temperature on Au(1 1/1) are reported.
Abstract: The structural and magnetic properties of self-organized CoxPt1−x nanostructures grown by codeposition at room temperature on Au(1 1 1) are reported. The samples have been imaged by scanning tunnelling microscopy and characterized by x-ray magnetic circular dichroism in the same ultra-high vacuum setup. We observe that the ordered growth is preserved for a large range of Pt concentrations. The magnetization cycles as functions of the magnetic field angle and the temperature are well reproduced by a simple model, giving a good estimation of the magnetic anisotropy distributions in these assemblies of nanostructures. The initially out-of-plane anisotropy for pure Co nanostructures strongly decreases until it lies in-plane for a 40% Pt concentration. This spin reorientation transition and the measured broadening of the switching field distribution with x are discussed using a phenomenological pair model that reproduces well the main magnetic properties of CoxPt1−x epitaxial nanostructures.
2 citations