STM study of Au adsorption on Si(111)-7 x 7 surface: voltage and temperature dependence.

We presented the scanning tunneling microscopy (STM) results on the study of Au adsorption at Si(111)-7 x 7 reconstructed surface. The voltage-dependent STM measurements indicated that there are at least three kinds of Au clusters and two types of single Au atoms adsorption on Si(111)-7 x 7 surface with Au coverage of about 0.2 monolayer. After the Au adsorbed Si surface was annealed at about 250 degrees C, the adsorbed Au clusters would diffuse into the Si substrate, and consequently create surface defects on the Si substrate. Sequentially annealed the sample at about 500 degrees C, the diffused Au would emerge out again and form larger 3-dimension Au clusters at the Si surface.