Force interactions and adhesion of gold contacts using a combined atomic force microscope and transmission electron microscope

We have investigated force interactions between two gold samples using a combination of atomic force microscope (AFM) and a transmission electron microscope (TEM) (TEM-AFM). The size and shape of the tip and sample as well as size of contact area and interactions type (elastic-plastic) is observed directly. The force was measured by direct measurement of the displacement of the AFM tip. An anomalous high value of the jump-to-contact distance was found, which we interpret as due to an enhanced surface diffusion of gold atoms towards the tip-sample gap due to the van der Waals force, leading to an avalanche situation where the gap is quickly filled until the ordinary jump-to-contact distance. The contact radius at zero applied load were measured and compared with adhesion theories. The results were in the Maugis transition re-ion, between the limiting cases of the Derjaguin-Willer-Toporov (DMT) and the Johnson-Kendall-Roberts (JKR) models. (C) 2002 Elsevier Science B.V. All rights reserved.