INTERMITTENT CONTACT SCANNING FORCE MICROSCOPY - THE ROLE OF THE LIQUID NECKS

We have studied the intermittent contact mode for small oscillation am plitudes and soft cantilevers with sharp tips. For appropriate working conditions the tip does not touch the mica surface. Instead, a high d issipative tip-sample interaction takes place which reduces the oscill ation amplitude of the cantilever. Our experiments show that this diss ipative interaction is related to the relative humidity and we believe that it is induced by a nanometer sized liquid neck between tip and s ample. A phase contrast image on different surface materials is then d ue mainly to the wetting properties of the corresponding material rath er than to their elastic or viscoelastic properties. The intermittent contact mode described in this work is especially advantageous since t he tip is extremely gentle with the surface. (C) 1998 American Institu te of Physics.