Observations of adhesion-induced deformations between spheroidal gold particles and conducting substrates

Abstract

Spheroidal gold particles, approximately 3 μm in diameter, were deposited on both hard and soft planar, electrically conducting substrates, and the interfaces were observed using scanning electron microscopy. It was observed that the particles appeared to embed into the softer substrate, but not into the harder one. The softer substrate also appeared to flow up the sides of the particles. The diameters of the craters formed are compared with the predictions based on Hertz’ [Zimon, Adhesion of Dusts and Powders (Consultants Bureau, New York, 1982)] model of elastic deformation, Krupp’s [Adv. Colloid Interface Sci. 1, 111 (1967)] model of plastic response [assuming van der Waals (Zimon, ibid. and Krupp, ibid.) interactions], and Johnson, Kendall, and Roberts’ [Proc. R. Soc. London Ser. A 324, 301 (1971)] model of tensile response due to surface tension. These calculations suggest that the observed deformation on the softer substrate is predominantly plastic rather than elastic and that surface tension is significant. The techniques are expanded and results reported for the case of gold particles on insulating surfaces.