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 mic roscopy and spectroscopy (STM/STS). At metal coverages as low as 0.05 monol ayer (ML), Ag forms well-ordered overlayer rows, or one-dimensional cluster s, on the underlying silicon surface. To produce these ordered structures, it is necessary to anneal the surface to approximate to 450 degrees C. As t he 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 med ian row length as a function of coverage. With regard to their electronic b ehavior, 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.