The differential atomic response of the topmost graphene layer on graphite

• Published in: Journal of physics. Condensed matter Vol. 21; no. 19; pp. 195402 - 195402 (8)
• Main Authors: Khara, G S, Choi, Jaewu
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 13.05.2009; Institute of Physics
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures; Electronic structure of nanoscale materials : clusters, nanoparticles, nanotubes, and nanocrystals; Exact sciences and technology; Physics; Scanning tunneling microscopy; Energy gap; Electronic structure; Lattice distortion; Graphene; Tunnel effect; Graphite; Electron interaction; Switching; Image contrast
• ISSN: 0953-8984; 1361-648X
• DOI: 10.1088/0953-8984/21/19/195402

The atomic response of the topmost graphene layer on graphite was studied by using scanning tunneling microscopy (STM) as a function of tunneling gap distance, gap voltage and bias polarity. The contrast of the site-dependent topographical image depends on the gap distance, and the site-dependent tunneling current order of magnitude at a given gap distance is switched with the gap voltage (i.e. the contrast is significantly altered). The site-dependent current order is altered at the lower positive gap voltage as the gap distance is reduced between the probe and the carbon atoms of the topmost graphene layer. The switching in the atomic image contrast and the current order of magnitude is directly related to the differential atomic response of carbon atoms to the STM probe originating from the electronically active and mechanically soft β-carbon atoms.