Influence of substrate temperature on submonolayer Au adsorption on an Si(111)-(7x7) surface studied by scanning tunneling microscopy

摘要

The influence of substrate temperature on the adsorption of submonolayer Au on an Si(111)-(7 x 7) surface was investigated using a scanning tunneling microscope. With a small amount of Au deposited at room temperature, Au atoms form small clusters located inside the half unit cells (HUCs) of the Si(111)-(7 x 7) surface while most parts of the surface are undisturbed. When the substrate temperature during deposition of the same Au amounts increases from room temperature up to 565 degrees C, the small Au clusters grow, coalesce into larger clusters, incorporate Si atoms, and finally form a (5 x 2) reconstruction. The Si(111)-(5 x 2) - Au reconstruction takes place in the form of island-hole pairs on a terrace, whereas only holes are formed in the upper terrace at a step. Both the islands and the holes display the (5 x 2) reconstruction. The occurrence of the island - hole pairs of the (5 x 2) reconstruction results from the fact that the Si atom density in the (5 x 2) reconstruction is lower than in the (7 x 7) reconstruction.