Direct Observation of Silver Atoms on Si

The dynamics of single silver atoms adsorbed on the Si(111)-7 times 7 surface has been studied between 300 K and 423 K with a variable-temperature scanning tunneling microscope. We discuss the diffusion behavior of one and two silver atoms when they diffuse into a half unit cell of the 7 times 7 reconstructed Si(111) surface. Detailed tracking of the movements of individual silver atoms within a 7 times 7 half unit cell was done at ~80 K. The activation energies and preexponential factors for different diffusion paths were estimated. Finally, possible mechanisms of silver atom diffusion on the Si(111)-7 times 7 surface are proposed based on both our data and those recently published by others