Interaction of aluminum with iridium surface: Adsorption, desorption, dissolution, and formation of surface compounds

The interaction of aluminum with an iridium (111) surface was studied in ultrahigh vacuum by Auger electron spectroscopy over the broad temperature range 300–2000 K. At room temperature, layer-by-layer growth of an aluminum film was observed, with a monolayer forming in coherent relation to the substrate. Deposition at 1100–1300 K gives rise to the formation of surface aluminide Ir₄Al with an adatom concentration N _Al = (4.20 ± 0.15) × 10¹⁴ cm^?2. It was shown that aluminum escapes out of the surface aluminide by thermal desorption in the 1300–1700-K temperature interval, with the desorption activation energy changing from ～4.5 to ～5.7 eV as the coverage decreases from the value corresponding to the surface aluminide (taken for unity) down to zero.