Imaging the displacement field within epitaxial nanostructures by coherent diffraction: a feasibility study

International audienceWe investigate the feasibility of applying coherent diffraction imaging to highly strained epitaxial nanocrystals using finite-element simulations of SiGe islands as input in standard phase retrieval algorithms. We discuss the specific problems arising from both epitaxial and highly strained systems and we propose different methods to overcome these difficulties. Finally, we describe a coherent microdiffraction experimental setup using extremely focused x-ray beams to perform experiments on individual nanostructures

Self-assembled triangular graphene nanostructures: Evidence of dual electronic response

Structural and electronic properties of bilayer graphene films and nanostructures obtained through the graphitization of SiC(0001) were investigated in this work using scanning tunneling microscopy and spectroscopy. We report on the observation of triangular nanostructures which result from extended stacking faults in the SiC substrate and their effects on graphene layers that are formed on top of them. Spectroscopic measurements revealed distinct electronic responses as a function of the local hydrogen intercalation. Spectroscopic signatures ranging from single- to double-layer graphene, as well as intermediate states were observed as a consequence of the (in)complete hydrogen intercalation process. High resolution topographic scanning tunneling microscopy images at resonant bias voltages inside triangular nanostructures reveal that the bottom layer of the bilayer graphene film is still bonded to the substrate. Therefore, the triangular nanostructures present edges and facets with the coexistence of carbon atoms in sp3 and sp2 hybridizations. Using atomistic calculations we have modeled the local density of states of these objects reproducing their electronic response. The generation of regions with distinct electronic responses is potentially interesting for high-density data storage with hidden bit capabilities.The authors acknowledge experimental support by the Brazilian Synchrotron Light Laboratory (LNLS). Financial support was provided by CNPq, CAPES, FAPEMIG and INCT-Nano-Carbono. This work was partially financed by the Project FIS2016-76617-P of the Spanish Ministry of Economy and Competitiveness MINECO, the Basque Government under the ELKARTEK project (SUPER), and the University of the Basque Country (Grant No. IT-756-13).Peer reviewe