The interpretation of scanning tunneling microscopic images of a single atomic vacancy on single and double graphene sheets as a model for the (00▪1) surface of graphite was considered. A 1-layer model was first selected which permitted the running of periodic density-functional theory calculations without destroying the charge density waves that formed in the vicinity of the vacancy. The main features of scanning tunneling microscopic images (bright spots in the vicinity of the defect, (√3 x √3)R30° modulation of the local electronic density near the Fermi level, third-order symmetry structure) were attributed to the electronic band structure of the defective graphite surface. Further analysis was made of a more extended crystal working cell model to ensure convergence toward the isolated atomic vacancy. The interlayer interaction played a crucial role in the interpretation of scanning tunneling microscopic images. A double-layer model was then considered and the impact of the interlayer interaction was analyzed. The local density of states was produced for the α and β vacancies which could be differentiated. The calculations reproduced the main features of scanning tunneling microscopic images, and the results were in good agreement with experimental observations.

Interpretation of STM Images of Graphite with an Atomic Vacancy via Density-Functional Calculations of Electronic Structure. Y.Ferro, A.Allouche: Physical Review B, 2007, 75[15], 155438 (10pp)