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 -