Dresden 2017 – scientific programme

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O: Fachverband Oberflächenphysik

O 94: Graphene: Electronic Properties, Structure and Substrate Interaction II

O 94.5: Talk

Thursday, March 23, 2017, 16:00–16:15, TRE Ma

Investigation of Graphene using Simultaneous Scanning Tunneling/Atomic Force Microscopy — •Majid Fazeli Jadidi and Hakan Özgür Özer — Istanbul Technical University, Istanbul, Turkey

We investigated graphene layers grown on Cu foils using simultaneous Scanning Tunneling Microscopy/Atomic Force Microscopy (STM/AFM). Atomic resolution images of the surface were obtained in many channels such as STM topography, oscillation amplitude, force, tunnel barrier height and phase shift. The simultaneous acquisition of multiple channels allows us to compare images at every pixel, which in turn sheds light on the contrast mechanisms in probe microscopy. In HOPG or multilayer graphene, due to the shift between two successive layers, 3 atoms of the hexagon have an atom underneath (alpha (A) site) whereas the other 3 don't have (beta (B) site). Hence, three main atomic structures at the surface are A and B atoms and hollow sites. In STM images B atoms appear higher due to the dominance of their electronic structure over A site atoms. In the oscillation amplitude images which is a measure of the interaction stiffness[1], the brighter spots match with the A sites. The oscillation amplitude throughout the entire image is well below the free amplitude which suggests a very high positive interaction stiffness. This observation is supported also by the Force-distance spectroscopy which is simultaneously acquired with all such acquisition channels.

[1] A. Oral, R. A. Grimble, H. Ö. Özer, P. M. Hoffmann, and J. B. Pethica, Appl. Phys. Lett. 79, 1915 (2001).