Atomic-scale view of motion on surfaces

Scanning tunneling microscopy has been used to obtain an atomic-scale view of the motion of adsorbates on surfaces. For sufficiently slow diffusion, we have followed this motion in real time. For faster adsorbate motion we were able to observe the partial and transient occupancy of surface sites on the time scale of our measurements. For lateral motion induced by surface processes such as adsorption or chemical reaction, we were able to analyze the final positions of the adsorbates or reaction products in order to measure the distances covered and to elucidate the means by which energy is accommodated to the surface.