title: Nanoscale Mapping of Dielectric Properties of Nanomaterials from Kilohertz to Megahertz Using Ultrasmall Cantilevers.
abstract: Electrostatic force microscopy (EFM) is often used for nanoscale dielectric spectroscopy, the measurement of local dielectric properties of materials as a function of frequency. However, the frequency range of atomic force microscopy (AFM)-based dielectric spectroscopy has been limited to a few kilohertz by the resonance frequency and noise of soft microcantilevers used for this purpose. Here, we boost the frequency range of local dielectric spectroscopy by 3 orders of magnitude from a few kilohertz to a few megahertz by developing a technique that exploits the high resonance frequency and low thermal noise of ultrasmall cantilevers (USCs). We map the frequency response of the real and imaginary components of the capacitance gradient (∂C(ω)/∂z) by using second-harmonic EFM and a theoretical model, which relates cantilever dynamics to the complex dielectric constant. We demonstrate the method by mapping the nanoscale dielectric spectrum of polymer-based materials for organic electronic devices. Beyond offering a powerful extension to AFM-based dielectric spectroscopy, the approach also allows the identification of electrostatic excitation frequencies which affords high dielectric contrast on nanomaterials.
authors.affiliation: School of Mechanical Engineering, Purdue University , West Lafayette, Indiana 47907, United States.|Birck Nanotechnology Center, Purdue University , West Lafayette, Indiana 47907, United States.
authors.forename: Maria J
authors.initials: MJ
authors.lastname: Cadena
authors.affiliation: School of Chemical Engineering, Purdue University , West Lafayette, Indiana 47907, United States.
authors.forename: Seung Hyun
authors.initials: SH
authors.lastname: Sung
authors.affiliation: School of Chemical Engineering, Purdue University , West Lafayette, Indiana 47907, United States.
authors.forename: Bryan W
authors.initials: BW
authors.lastname: Boudouris
authors.affiliation: Birck Nanotechnology Center, Purdue University , West Lafayette, Indiana 47907, United States.|Department of Physics, Purdue University , West Lafayette, Indiana 47907, United States.
authors.forename: Ronald
authors.initials: R
authors.lastname: Reifenberger
authors.affiliation: School of Mechanical Engineering, Purdue University , West Lafayette, Indiana 47907, United States.|Birck Nanotechnology Center, Purdue University , West Lafayette, Indiana 47907, United States.
authors.forename: Arvind
authors.initials: A
authors.lastname: Raman
keywords: EFM; capacitance gradient; dielectric spectroscopy; second harmonic; ultrasmall cantilevers