Calculation of an Atomically Modulated Friction Force in Atomic - Force Microscopy

PACS. 82.20K-Potential energy surfaces for chemical reactions. PACS. 71.45N-Calculations of total electronic binding energy. PACS. 68.65-Layer structures, intercalation compolU1ds and superlattices: growth, structure and non-electronic properties. PACS. 61.16D-Electron microscopy determinations (inc. scanning tunnelling microscopy methods). Abstract.-We investigate the microscopic mechanism of energy dissipation in the friction force microscope (FFM), which is a modification of the atomic-force microscope for application to friction. Based on ab initio results for the interaction between Pd and graphite, we determine the atomic-scale modulation of the friction force and the corresponding stick-slip molion at the interface during the relative motion between these solids. We propose two idealized versions of the FF1\1 and show that the friction force depends not only on the Pd-graphite interaction potential, but even more critically on the construction parameters of such a microscope. Friction between two solids is one of the most important and complex processes which affect everyday's life. So far, the science of friction-tribology-has described this phenomenon mainly in a macroscopic and phenomenological way [1]. More recently, successful attempts have been undertaken to observe friction forces on the atomic scale [2] and to understand the underlying microscopic mechanisms in case of sliding friction without wear [3]. Independently, the availability of supercomputers has made predictive calculations [4,5] of atomic-scale friction forces possible. The recent experimental progress in nanotribology has been facilitated by the development of a modified version of the atomic-force microscope [6] (AFM) for application to friction, which is sometimes called the friction force microscope (FFM). Like the AFM, the FFM consists of an «atomically sharp" tip of a material A, suspended on a soft cantilever, which is brought into nondestructive contact with a well-defined substrate B. Measuring the vertical deflection of the cantilever is used to keep the applied load F..xl constant during the sLUface scan. An independent measurement of the cantilever deflection in the direction of