INITIAL-STAGE GROWTH AND INTERFACE FORMATION OF AL ON SI(001)2X1

Initial stage growth and interface Formation of Al on a Si(001)2 x 1 s urface has been studied by core-level and valence-band photoelectron s pectroscopy using synchrotron radiation for the Al coverages (theta(Al )) up to similar to 2 ML at room temperature (RT) and 300 degrees C. T he measured Al 2p and Si 2p spectra reveal, for the first time, the ex istence of interfacial reaction of Al with Si in addition to the rathe r well-known dimer adsorption of Al. The reaction occurs even at RT fo r theta(Al) greater than or equal to 0.5 ML, which progresses signific antly by annealing at 300 degrees C from earlier stage of adsorption. Beyond 0.5 ML, Al 2p core levels indicate formation of Al dusters at b oth temperatures, which is accompanied by increase of the reacted phas e. This interfacial reaction explains the 1 x 1 phase at 300 degrees C found by LEED and the difference in band bending between RT and 300 d egrees C above similar to 0.5 ML. The evolution of the valence-band su rface electronic structures with respect to theta(Al) is interpreted i n a consistent way to the core-level results.