Force microscopy imaging in liquids using ac techniques

Two ac techniques for imaging under liquids using atomic force microscopy are investigated. In the first method, the sample is oscillated with a sinusoidal displacement, whereas in the second method, the cantilever is oscillated with a sinusoidal magnetic force. Both techniques are successful for topographic imaging under liquids with the tip in repulsive contact with the sample. Of the two methods, the cantilever driven technique is found to be less noisy. In addition to topographic imaging, noncontact magnetic force imaging under liquid is demonstrated.