Interpretation of scanning probe microscope image of the structure of atomic vacancy on graphite: ab initio periodic Hartree–Fock calculations

Abstract

By using the CRYSTAL 95 program, ab initio periodic Hartree–Fock (PHF) calculations with the full potential and 6-21G∗ basis set are applied to the interpretation of scanning tunneling microscope (STM) and atomic force microscopy (AFM) image of the structure of atomic vacancy in graphite. Our results show that change in the total electron density when compared with the ideal structure is considerable at the missing atom site, but it is not considerable beyond a distance upon the missing atom site. However, the partial charge density, which originates from the states near the Fermi energy is enhanced at the atoms surrounding the vacancy. These results are in a good agreement with those of Hahn et al. (Phys. Rev. B 53 (1996) R1725), who take that vacancies are transparent in AFM but imaged as surface protrusions in STM. In conclusion, our results should clarify the reason why vacant sites of graphite are visible shown in STM, while they are not easy to detect in AFM.