DIRECT OBSERVATION OF THE SELF-DIFFUSION MECHANISM ON THE AG(100) SURFACE

Perturbed angular correlation experiments using soft-landed Ag-111 pro be atoms on a Ag(100) surface allow monitoring of the self-diffusion o f Ag on the surface. Tn total, three different sites are observed as a function of substrate temperature: the adatomic terrace site in the t emperature interval between XO and 150 K, the adatomic step site betwe en 130 and 180 K, and the substitutional terrace site starting from 15 0 K, where adatoms are still present on the surface. These data could be explained only by assuming that the hopping diffusion mechanism is active at low temperatures, while the exchange diffusion mechanism is responsible for the observed substitutional terrace site at 150 It. [S 0031-9007(98)07711-4].