Effect of electrostatic force and tapping mode operation of atomic force microscope

We investigated tip-sample interaction under an electrostatic field. We have also demonstrated the tapping mode microscopy using an electrostatic force modulation. By applying dc and ac bias voltages between the probe and sample, we measured the dc and ac electrostatic force. Our result indicates that the ac force curve as a function of tip to sample distance produces more quantitative information on the tip-sample interaction than the dc force curve. The ac force vs. distance curve can be used for the tapping mode operation of the microscope using the electrostatic force. The tapping mode technique can be applied to obtain the image of soft samples with a high spatial resolution. In addition, by applying the tapping mode technique, we measured the surface potential and topography of a test device simultaneously.