ADSORPTION OF AL ON SI(100) - A SURFACE POLYMERIZATION REACTION

We study the adsorption of Al on the Si(100) surface by ab initio calculations for a complete range of coverages from an isolated Al adatom up to full surface coverage. Analysis of the energetics of adsorption and the mobility of Al adatoms reveals that the long, one-dimensional strings of Al dimers observed experimentally result from a sequence of reaction steps which can be classified as a surface polymerization. The calculated local density of states (LDOS) of the adsorbed Al row is compared with scanning tunneling microscopy images. The LDOS characteristic of the reaction sites which mediate the polymerization should be observable by scanning tunneling spectroscopy.