Surface diffusion: an STM view

We employ a high-speed high-temperature scanning tunneling microscope to investigate two manifestations of surface diffusion. The step fluctuations observed on metal surfaces are shown to be the result of the fast diffusive motion of pre-existing kinks in the steps. We find that a high density of kinks can be induced by a minute concentration of impurities. At sufficiently high temperatures, surfaces can "jump" to physical contact with the Tip of the microscope. Such jumps are followed by a "sintering" process in which a massive connecting neck rapidly builds up between the surface and the Tip.