Microscopic investigations on the origins of triboelectrific effect by combined multi-scanning probe microscopes / scanning electron microscope – NANOTRIBELEC

The ANR NanoTribElec is based on local measurements of topography and electrical spectroscopy performed by scanning probe microscopy. In this context, a multi-probes microscope (multi-SPM) is under development in the laboratory of tribology and system dynamics (LTDS). This instrument will combine in situ atomic force microscopy to characterize the surface topography (AFM) or applying a frictional force (LFM), electrostatic force microscopy (EFM / KPFM) for determining the local distribution of induced electrical charges and a scanning electron (SEM) for controlling the spatial positioning of the probes and / or inject charges microscopy.

A first version of the microscope design is already drawn and the system related to its running is operational. It consists of an electronic control unit and a high voltage generator from Nanonis and Attocube companies and a phase locked loop ( PLL) of Zurich Instrument. With this control electronics, a first resonance test was successfully completed on levers Akiyama.

Motivated by many questions in fundamental physics and industrial interest to reduce wear and energy loss, research in this ANR will first focus on the microscopic origin of the triboelectrification in the diamond and III -N semiconductors. These materials are particularly important for emerging nanotechnology -based NEMS or nanopiezotronics. Thereafter, the versatile and evolving nature of the multi-probe microscope will offer many possibilities of study.

Internship report of Z. Wang on ' local electrical properties of copper -DLC coating probed by scanning spreading resistance microscopy'. Article in preparation.

NANOTRIBELEC project concerns the microscopic studies of the triboelectrific effect, i.e. the charges generation due to contacts and frictions. Up to now, this phenomenon is still not well-understood especially between two poor electrical conductors and its effects on adhesion and wear are unclear. This research project is not only motivated by questions on fundamental physics but also by its relevance for emerging nanotechnologies based on NEMS or nanopiezotronics and by obvious interests in general industries to reduce wear and related energy lost.

Our goal is first to identify and quantify the electrical charges generated by friction and to correlate them with the microscopic properties of several types of materials having different sorts of defects and electrical properties. Our study approach or strategy will be based on local probing technique. A unique tool will be developed, which combine in situ scanning electron microscopy (SEM) for rough spatial localization or precise charges injection, atomic force microscopy (AFM) for either surface topography characterizations or to apply controlled friction, and electrostatic force microscopy (EFM/KPFM) for the determination of local charges distribution. Such a multi-probes microscope will be completely polyvalent and evolutionary in order to offer several possibilities of future studies for PhD students and others members of our tribology laboratory. As a first use, we will focus on the microscopic origin of the triboelectrific effect in diamond and III-N semiconductor since they are important materials for nano- sciences and technology.

This project combines several persons working in different fields: F. Dahlem (expert on nanophysics and local probing of electrical charges), D. Juve (expert on modified SEM), M. Guibert and D. Roux (experts on mechanical engineering), M-I de Barros (expert on diamond growth), R. Songmuang (expert on growth of bulk and nanoobject of several types of semiconductor), L. Galitre (head of Communications).