The differential atomic response of the topmost graphene layer on graphite

Abstract

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.

Moiré patterns on STM images of graphite induced by rotations of surface and subsurface layers

“…At first, a few decades ago and from a fundamental point of view, atomic resolved STM images were obtained from the highly oriented pyrolitic graphite (HOPG) surface. As at atomic scale such STM images show triangular and/or honeycomb lattices, even under different experimental conditions [1][2][3], several efforts have been done to understand this behavior [4][5][6][7], but only recently a conclusive explanation has been reached [8]. In the nineties the research on graphitic surfaces shifted the attention to the STM observation of superstructures [9][10][11], and thereafter to the interaction between such superstructures and grain boundaries in graphite [12].…”

Theoretical reproduction of superstructures revealed by STM on bilayer graphene

“…[15] and references therein). This has been a long standing controversy which has attracted renewed interest over the STM image formation of graphite surface [11,16,17,18] and over the physical origin of superstructures [15,19,20,21].…”