Biomedical Engineering Reference
In-Depth Information
probed via STM. Simulated constant-current STM images are shown
in Fig. 5.12.
Calculations were based on the theory of Tersoff and Hamann
[30] for a constant-current STM imaging, which in a nutshell states
that the STM tip position map follows the contours of a local density
of states (LDOS) isosurface. Assuming the s-wave probe tip, we
use the states closest to the Fermi level. The isosurfaces used here
(both for atom and pair adsorption) have been chosen solely to get
a topography that is quantitatively consistent with the reported tip
position corrugation in Ref. [13], i.e., the “bright spots” are about 2 Å
above the clean sections of the surface.
Figure 5.12
(top row) Simulated STM images (tip
position plots). (a) H
atom on graphene, (b) p1 pair on graphene, and (c) p6 pair
on graphene. All images are shown using the same scale. The
middle row shows the approximate position of honeycomb
lattice of C atoms, which we include for visual reference.
Bottom panels show, for comparison, the hydrogen structures
together with reconstruction extents.
z
Figure 5.10d and e indicates that the presence of adsorbed
hydrogen atom should be very well observed from a strong disruption
of the graphene surface electronic states: the presence of the H atom
