TY  - JOUR
Y1  - 2014/05//
ID  - discovery1433814
UR  - http://dx.doi.org/10.1021/nn501785q
N2  - 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.
SP  - 5339 
VL  - 8
A1  - Gao, DZ
A1  - Grenz, J
A1  - Watkins, MB
A1  - Canova, FF
A1  - Schwarz, A
A1  - Wiesendanger, R
A1  - Shluger, AL
JF  - ACS NANO
AV  - public
SN  - 1936-0851
TI  - Using Metallic Noncontact Atomic Force Microscope Tips for Imaging Insulators and Polar Molecules: Tip Characterization and Imaging Mechanisms
EP  -  5351
IS  - 5
N1  - © 2014 American Chemical Society. Terms of Use CC-BY. 

PubMed ID: 24787716
KW  - NC-AFM
KW  -  insulator
KW  -  imaging mechanism
KW  -  metallic tip
KW  -  virtual AFM
ER  -