STM and STS studies of one-dimensional row growth: Ag on Si(5512)

We have studied the growth of Ag on Si(5 5 12) using scanning tunneling microscopy and spectroscopy (STM/STS). At metal coverages as low as 0.05 monolayer (ML), Ag forms well-ordered overlayer rows, or one-dimensional clusters, on the underlying silicon surface. To produce these ordered structures, it is necessary to anneal the surface to approximate to 450 degrees C. As the coverage is increased above 0.05 ML, the rows grow in length and number until the surface forms a periodic array of such structures at similar to 0.25 ML. A statistical analysis of the rows reveals a linear increase in median row length as a function of coverage. With regard to their electronic behavior, STS measurements show a significantly narrower band gap along the Ag rows than is found on the underlying silicon structures. Therefore, the deposited Ag atoms do retain some metallic behavior.