title: Dielectric constants by multifrequency non-contact atomic force microscopy.
abstract: We present a method to obtain capacitive forces and dielectric constants of ultra-thin films on metallic substrates using multifrequency non-contact atomic force microscopy with amplitude feedback in air. Capacitive forces are measured via cantilever oscillations induced at the second bending mode and dielectric constants are calculated by fitting an analytic expression for the capacitance (Casuso et al 2007 Appl. Phys. Lett. 91 063111) to the experimental data. Dielectric constants for self-assembled monolayers of thiol molecules on gold (2.0±0.1) and sputtered SiO2 (3.6±0.07) were obtained under dry conditions, in good agreement with previous measurements. The high Q-factor of the second bending mode of the cantilever increases the accuracy of the capacitive measurements while the low applied potentials minimize the likelihood of variation of the dielectric constants at high field strength and of damage from dielectric breakdown of air.
authors.affiliation: Department of Physics and Astronomy, University of South Carolina, 712 Main Street, Columbia, SC 29208, USA.
authors.forename: Bharat
authors.initials: B
authors.lastname: Kumar
authors.forename: Joseph C
authors.initials: JC
authors.lastname: Bonvallet
authors.forename: Scott R
authors.initials: SR
authors.lastname: Crittenden
mesh_terms: D025802:Electric Capacitance; D008670:Metals / Q000737:chemistry; D018625:Microscopy, Atomic Force / Q000379:methods*; D013438:Sulfhydryl Compounds / Q000737:chemistry
chemical_list: D008670:Metals; D013438:Sulfhydryl Compounds