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 region, between the limiting cases of the Derjaguin–Müller–Toporov (DMT) and the Johnson–Kendall–Roberts (JKR) models.