THERMAL ANNEALING OF THE EPITAXIAL AL SI(111)7X7 INTERFACE - AL CLUSTERING, INTERFACIAL REACTION, AND AL-INDUCED P(+) DOPING/

The structural and electronic properties of the epitaxial Al/Si(111)7x 7 interface and their modifications upon thermal annealing were invest igated by scanning tunneling microscopy, high-resolution photoelectron spectroscopy, and low-energy electron diffraction. Room-temperature d eposition of 40 Angstrom Al on Si(111)7X7 is mainly characterized by e pitaxial growth and a decrease of the Fermi-level position by 0.32 eV. Annealing at temperatures around 500 degrees C results in the formati on of large Al clusters with a thin reacted film in between. Subsequen t annealing up to 900 degrees C results in complete desorption of Al a nd a recovery of the original 7X7 surface structure, while a potential variation underneath the Si surface, completely different from that o f the starting surface, is observed in the Si 2p photoemission spectra . These results strongly indicate the formation of a p(+)-Si layer ind uced by Al diffusion. (C) 1995 American Vacuum Society.