PRECISE FORCE CURVE DETECTION SYSTEM WITH A CANTILEVER CONTROLLED MAGNETIC FORCE FEEDBACK

We present the development of an atomic force microscope (AFM) with an externally controllable force using an electromagnet. The position of the AFM cantilever with magnetic material at the end of the backside is controlled directly by the external magnetic field of an electromag net. It is possible to use an optical detection system because the ele ctromagnet is located inside the piezo tube on which the sample is mou nted. A magnetic force feedback system has been implemented in this AF M. The effective stiffness of the cantilever is increased by the open loop gain of the feedback. We are able to control the motion of a soft cantilever (0.16 N/m) with this feedback system in air. Force feedbac k using an electromagnet allows the elimination of ''snap-in'' contact which may physically damage the tip and mica sample. (C) 1997 America n Institute of Physics. [S0034-6748(97)01711-5].