ATOMIC-FORCE MICROSCOPY UNDER LIQUID - A COMPARATIVE-STUDY OF 3 DIFFERENT AC MODE-OPERATIONS

The image contrast mechanism of three newly proposed AC mode operation s under liquid in three different frequency ranges is presented. They all rely on a strong repulsive force to damp the cantilever and the ti p still 'touches' the sample surface. A direct comparison of the three different modes of operation with the conventional DC mode technique using the same gold sample under isopropanol was conducted, It was fou nd that all the three AC modes exerted a much smaller lateral force th an the DC mode although the normal loads were of the same order of mag nitude, The suitability of such techniques in imaging physisorbed syst ems on hard substrates (such as soft biological samples) and the prosp ect of a true non-contact repulsive mode operation are discussed.