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1 IM2NP - Institut des Matériaux, de Microélectronique et des Nanosciences de Provence

Abstract : Kelvin Probe Force Microscopy KPFM is a technique aiming at the detection and compensation of electrostatic forces arising between a nanoprobe the tip of the microscope and a surface hereafter referred to as the electrodes when they are biased. The origin of these forces differs upon the distance between the electrodes 1. At large distance >1nm, electrostatic forces can be quantitatively connected to the Contact Potential Difference CPD between the electrodes, i.e. the difference between their work functions. Thus the technique gives a quantitative CPD map of the surface on the local scale 2. When measured closer to the surface in the range of 0.5-1 nm, short-range electrostatic forces start to get involved in the imaging process. Then, a KPFM image with atomic-scale resolution can be achieved 3. However, in this situation, the origin of the KPFM signal rather reflects atomic-scale properties of the surface, among which its local polarizability. The ability for the technique to provide access to the CPD and other properties down to the atomic-scale makes KPFM widely used in surface science nowadays. In the 1990-s, the KPFM technique has been successfully coupled with noncontact-AFM 1. The possibility to perform joint experiments where structural and electronic properties become accessible in a row made the couple KPFM-nc-AFM attractive and intensively developed and used in numerous research labs. The goal of this lecture will be to discuss experimental technical implementation, modes, time constants considerations, artefacts

. and theoretical aspects long-short-range electrostatic forces of the KPFM technique when coupled with nc-AFM and to illustrate these by means of examples taken from recent literature.

Autor: Laurent Nony -



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