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Advances in Condensed Matter Physics - Volume 2015 2015, Article ID 754098, 6 pages -

Research Article

Instituto de Ciencia de Materiales de Madrid, CSIC, Campus de Cantoblanco, 28049 Madrid, Spain

Departamento de Ingeniería Informática, Escuela Politécnica Superior, Universidad Autónoma de Madrid, 28049 Madrid, Spain

Received 7 May 2015; Revised 26 August 2015; Accepted 30 August 2015

Academic Editor: Da-Ren Hang

Copyright © 2015 E. Castellano-Hernández and G. M. Sacha. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


A study of the electrostatic force between an Electrostatic Force Microscope tip and a dielectric thin film with finite conductivity is presented. By using the Thomas-Fermi approximation and the method of image charges, we calculate the electrostatic potential and force as a function of the thin film screening length, which is a magnitude related to the amount of free charge in the thin film and is defined as the maximum length that the electric field is able to penetrate in the sample. We show the microscope’s signal on dielectric films can change significantly in the presence of a finite conductivity even in the limit of large screening lengths. This is particularly relevant in determining the effective dielectric constant of thin films from Electrostatic Force Microscopy measurements. According to our model, for example, a small conductivity can induce an error of more than two orders of magnitude in the determination of the dielectric constant of a material. Finally, we suggest a method to discriminate between permittivity and conductivity effects by analyzing the dependence of the signal with the tip-sample distance.

Author: E. Castellano-Hernández and G. M. Sacha



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