STM and STS Studies of One-Dimensional Row Growth: Ag on Si(5 5 12)

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 450°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 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.