Enhanced dielectric constant resolution of thin insulating films by electrostatic force microscopy

This is the author’s version of a work that was accepted for publication in Journal of Physics: Condensed Matter. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Journal of Physics: Condensed Matter 24.15 (2012) 10.1088/0953-8984/24/15/155303Electrostatic Force Microscopy has been shown to be a useful tool to determine the dielectric constant of insulating films of nanometer thicknesses that play a key role in many electrical, optical and biological phenomena. Previous approaches make use of simple analytical formulae to analyse the experimental data for thin insulating films deposited directly on a metallic substrate. Here we show that the sensitivity of the EFM signal to changes in the dielectric constant of the thin film can be enhanced by using dielectric substrates with low dielectric constants. We present detailed numerical calculations of the tip-sample electrostatic interaction in the following set-up: the insulating thin film, a dielectric substrate (or spacing layer) of known low dielectric constant and a metallic electrode. The EFM sensitivity to the dielectric constant increases with the thickness of the spacing layer and saturates for thicknesses above 100-300 nm, when it is close to that of an infinite medium.Authors acknowledge C. Gómez-Navarro, J. Gómez-Herrero, P. Varona and F. Rodríguez for insightful discussions. This work was supported by TIN2010-19607, the Spanish MICINN ( Grant No: FIS2009 − 13430 −C02 − 02 ) and by the Comunidad de Madrid Microseres Program (Grant No: S2009/T IC − 1476). GMS acknowledges support from the Spanish Ramón y Cajal Program