| Autor: |
Gao DZ; Department of Physics and Astronomy, University College London , Gower Street, London WC1E 6BT, United Kingdom., Grenz J, Watkins MB, Federici Canova F, Schwarz A, Wiesendanger R, Shluger AL |
| Jazyk: |
angličtina |
| Zdroj: |
ACS nano [ACS Nano] 2014 May 27; Vol. 8 (5), pp. 5339-51. Date of Electronic Publication: 2014 May 12. |
| DOI: |
10.1021/nn501785q |
| Abstrakt: |
We demonstrate that using metallic tips for noncontact atomic force microscopy (NC-AFM) imaging at relatively large (>0.5 nm) tip-surface separations provides a reliable method for studying molecules on insulating surfaces with chemical resolution and greatly reduces the complexity of interpreting experimental data. The experimental NC-AFM imaging and theoretical simulations were carried out for the NiO(001) surface as well as adsorbed CO and Co-Salen molecules using Cr-coated Si tips. The experimental results and density functional theory calculations confirm that metallic tips possess a permanent electric dipole moment with its positive end oriented toward the sample. By analyzing the experimental data, we could directly determine the dipole moment of the Cr-coated tip. A model representing the metallic tip as a point dipole is described and shown to produce NC-AFM images of individual CO molecules adsorbed onto NiO(001) in good quantitative agreement with experimental results. Finally, we discuss methods for characterizing the structure of metal-coated tips and the application of these tips to imaging dipoles of large adsorbed molecules. |
| Databáze: |
MEDLINE |
| Externí odkaz: |
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