Circular AFM Mode: A New AFM Mode for Investigating Surface Properties
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Circular AFM Mode: A New AFM Mode for Investigating Surface Properties
Olivier Noel1, Pierre-Emmanuel Mazeran2, Hussein Nasrallah1 1 Molecular Landscapes & Biophotonics Group, LPEC UMR CNRS 6087, Université du Maine, Le Mans, France 2 Surface Mechanics Group, Laboratoire Roberval, UMR CNRS 6253, Université de Technologie de Compiègne, France ABSTRACT For the first time, a new AFM mode is presented that simultaneously allows the measuring of adhesion and friction forces at different constant and continuous sliding velocities. Our methodology consists of implementing a circular relative displacement of the contact to reach a constant sliding velocity, with no stop periods. Some of the main advantages of performing a circular displacement is that continuous and high sliding velocities (more than 1 mm/s) can be reached compared to the low sliding velocities (up to 10 μm/s) available when using commercial AFM. Also, a stationary state is reached when doing measurements. Moreover, the circular mode can be coupled with the classical operating mode, for instance, force spectrum. Main applications of this circular mode are related to metrological measurements in physics that require high speed displacements. As an example, we report the evolution of friction and adhesive forces measured in air at different high sliding velocities. INTRODUCTION The development of new techniques such as the Atomic Force Microscopy (AFM) offers new opportunities to understanding, at a nanometric scale, phenomenological mechanisms encountered in many fields such as material science, mechanics, biology or microelectronics. Indeed, this widely used technique has become a powerful analytical tool for measuring intermolecular interaction forces with high sensitivity. In particular, it is possible to generate a relative back and forth displacement of a nanometer probe to a sample surface. The amplitude of this relative displacement ranges from 0 to 100 μm, with typical frequencies ranging between 0.1 and 10 Hz, while measuring torsion forces (for a displacement of the probe in the plane of the sample) or adhesive forces (for a displacement of the probe perpendicular to the sample) [2]. It also offers the capability of imaging surface properties and topography with high resolution [3].
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Although the design of high-speed AFM has improved to get fast surface properties imaging [47], it is still challenging to get experimental accurate results for displacement velocities higher than 100 μm/s. In addition, the inversion of the movement direction when performing image scanning or spectra force acquisition generates stop periods during which the nature of the tip/sample contact may evolve significantly. In all cases, no stationary state is obtained during measurements or scanning. Here, we present for the first time a new AFM mode called “the circular AFM mode”[1] that allows collecting data at different constant and continuous high sliding velocities (higher than 1 mm/s) without any stop periods. Our methodology consists of modifying an AFM to achie
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