Long-Range Electronic Perturbations Caused by Defects Using Scanning Tunneling Microscopy

Abstract

Real-space observations of long-range electronic perturbations caused by defects have been made with scanning tunneling microscopy. The defects are isolated adsorbed molecules on the surface of graphite. These defects perturb the charge density, giving periodic oscillations similar to Friedel oscillations. The oscillations have a wavelength radical3 times that of the graphite lattice, and the symmetry of the oscillations reflects the nature of the defect.

Scanning tunneling microscopy and spectroscopy of the electronic local density of states of graphite surfaces near monoatomic step edges

“…These superstructures have been also observed by other authors in the vinicity of defects on HOPG surfaces such as grain boundaries, 22 deposited metal particles, 23,24,25,26,27 or holes made by spattering. 28,29 They are attributed to an interference between incident and scattered electron wave functions.…”

“…28,29 They are attributed to an interference between incident and scattered electron wave functions. 23 However, topology of the defect sites was not known in these experiments, while the experimental results were explained by arbitrary combinations between the incident and scattered wave functions. 25,26 On the other hand, the zigzag and armchair edges have well-defined structures in atomic scale.…”

Soft oxidation of graphite studied by XPS and STM

“…These 0 atoms could modify the charge density of their neighboring carbons. In a way similar to Friedel oscillations observed near to defects, which can decay away from defects over some ten lattices constants [18], the 0 atoms influence can extend on some nanometers. The electronic contribution of B site carbon and A site carbon localized near the oxygen atom could be modified in such a way that an electronic enhancement occurs along a given direction.…”

“…The electronic contribution of B site carbon and A site carbon localized near the oxygen atom could be modified in such a way that an electronic enhancement occurs along a given direction. The enhancement of a given cristallographic direction of graphite can be observed when imaging atomic defects on graphite [14,18]. As presented by figure 5 electronic enhancement due to the oxygen atoms should extend along a given direction and should affect both A sites and B sites situated on the two sides of the oxygen linking atom.…”

Effects of Slow Highly Charged Ion Impact Upon Highly Oriented Pyrolytic Graphite-Nanoscale Modification of Electronic States of Graphite Surface-

“…Fig. 2(a) shows symmetric triangular features due to electronic perturbation in the case of Ar + impact, indicating multiple point defects which were typically seen for the singly charged ion irradiation onto HOPG surfaces (18) . On the other hand, in the case of Ar 8+ irradiation, a larger protrusion-like feature was observed due to the contribution of the Coulomb potential of ions as shown in Fig.…”