Control of magnitude of charge transfer and direct observation of the triboelectric charges with atomic force mircoscopy

Abstract

In this work, we demonstrate contact electrification with peak force tapping atomic force microscopy (AFM). In comparison to friction force microscopy, this method offers vertical motion of tip with direct force control minimizing lateral forces. This mode was used in order to investigate the magnitude of charging as changing the writing conditions such as loading force, and the number of tapping without changing lateral force. The measured surface potential shows that charges can be generated much more as increasing contact force and the number of tapping. We also explored the accumulation of triboelectric charges by measuring tip-sample current. The results show that current increases and eventually reaches saturation value while the slope of it decreases as a function of time implying dissipation of surface charges. This trend is also verified by detecting different surface potential and current profiles depending on hydrophilicity of sample surface. Since uv-radiation generates formation of hydroxyl group making tribocharges dissipate quickly, uv-radiated samples shows less trapped charges and lower variation of cycle-averaged current. This work would provide a new method to investigate triboelectrification, especially controlling magnitude of charge transfer with reduced damage to sample surface and quantifying accumulation rate of tribocharges depending on surface properties of materials.