Seminars Archive

Quantifying the dielectric constant at the nanoscale

Abstract
The dielectric constant of insulating materials plays a key role in many electrical, optical, and biological phenomena. However, with scaling of technological applications towards nanoscale lengths, the accurate measurement of this parameter has become increasingly difficult, since standard dielectric characterization techniques are limited to micrometer-scale spatial resolution. Recently, we made great advances in this direction by developing a scanning force microscopy technique, referred to as nanoscale dielectric microscopy (NDM), which allow quantifying the dielectric constant at the nanoscale in the low-frequency range (<1MHz). In NDM, quantitative dielectric constant images are reconstructed from local capacitance (or capacitance gradient) images obtained with state-of-the-art alternating-current (or electrostatic) force microscopy assisted by theoretical models (analytical1-3 or based on finite-element calculations4). The dielectric constants thus obtained are independent from the experimental parameters e.g. probe radius, scan height, etc… and hence they represent the intrinsic property of the material at the nanoscale. In this communication we will present the principles of Nanoscale Dielectric Microscopy and its application to a wide variety of nanoscale systems including thin1 and thick3 dielectric films, supported biomembranes2,3 and self-assembled lipid layers. 1 L. Fumagalli, G. Ferrari, M. Sampietro and G. Gomila, Appl. Phys. Lett. 91, 243110 (2007). 2 L. Fumagalli, G. Ferrari, M. Sampietro and G. Gomila, Nano Lett. 9, 1604 (2009). 3 G. Gramse, I. Casuso, J. Toset, L. Fumagalli and G. Gomila, Nanotechnology 20, 395702 (2009). 4 L. Fumagalli, G. Gramse, D. E. Esteban, M. A. Edwards and G. Gomila, Appl.Phys.Lett, in press.