Initial stage growth and interface formation of Al on Si(001)2 × 1

Abstract

Initial stage growth and interface formation of Al on a Si(001)2 × 1 surface has been studied by core-level and valence-band photoelectron spectroscopy using synchrotron radiation for the Al coverages ( Θ Al) up to ∼2 ML at room temperature (RT) and 300°C. The measured Al 2p and Si 2p spectra reveal, for the first time, the existence of interfacial reaction of Al with Si in addition to the rather well-known dimer adsorption of Al. The reaction occurs even at RT for Θ Al ≥ 0.5 ML, which progresses significantly by annealing at 300°C from earlier stage of adsorption. Beyond 0.5 ML, Al 2p core levels indicate formation of Al clusters at both temperatures, which is accompanied by increase of the reacted phase. This interfacial reaction explains the 1 × 1 phase at 300°C found by LEED and the difference in band bending between RT and 300°C above ∼0.5 ML. The evolution of the valence-band surface electronic structures with respect to Θ Al is interpreted in a consistent way to the core-level results.