Tapping mode atomic force microscopy using electrostatic force modulation

We have developed a simple tapping mode in atomic force microscopy using a capacitive electrostatic force. In this technique, the probe-to-sample distance is modulated by the capacitive force between tip and sample induced by a sinusoidal bias applied to the conductive probe instead of a conventional mechanical vibration. The electrostatic force versus distance curve of the probe indicates that it is necessary to use a rather stiff cantilever to prevent the snapping of the tip into the surface due to the adhesive force at the surface. We have succeeded in obtaining topographic images of a conductive surface as well as a soft polystyrene sample with a low tracking and lateral force through this method.