GROWTH-MORPHOLOGY AND ELECTRONIC-PROPERTIES OF ULTRATHIN AL FILMS ON PT(111)

The growth morphology and electronic properties of Al films on Pt(111) have been investigated by STM, XPS and AES at 160 K and 300 K. Film g rowth is kinetically controlled at both temperatures, with formation o f 2D Al dendrites during the initial stages of deposition. At 300 K, c ompletion of the first monolayer is followed by 3D island formation, w hile at 160 K layer-by-layer growth persists for Al coverages greater than or equal to 5 monolayers. Pt core-level and valence-band X-ray ph otoelectron spectra show growth of a high binding energy interfacial P t state during 300 K deposition, indicative of Pt/Al surface alloying. No significant alloying occurs during 160 K growth. At 300 K, deposit ion of second-layer Al signals the onset of adatom place exchange with the underlying Pt, reflecting a rather delicate balance between surfa ce energy and free energy of alloy formation. The limiting Pt/Al surfa ce alloy stoichiometry corresponds to Pt2Al3, and the associated Pt co re level shift is in quantitative accord with an interesting linear co rrelation which is found between the composition and associated core-l evel shifts of other Al-transition metal alloys. (C) 1997 Elsevier Sci ence B.V.