Force and conductance during contact formation to a C60molecule

Force and conductance were simultaneously measured during the formation of Cu–C 60 and C 60 –C 60 contacts using a combined cryogenic scanning tunneling and atomic force microscope. The contact geometry was controlled with submolecular resolution. The maximal attractive forces measured for the two types of junctions were found to differ significantly. We show that the previously reported values of the contact conductance correspond to the junction being under maximal tensile stress.