The growth of ultrathin Al2O3 films on Cu(1 1 1)

The growth of ultrathin films of Al2O3 on Cu(1 1 1) in the temperature range 300–1200 K was investigated by using Auger electron spectroscopy (AES), low-energy electron diffraction (LEED) and high-resolution electron energy loss spectroscopy (HREELS). Eight monolayers of a mixture of nickel and aluminum (Ni:Al=1:2) were deposited on Cu(1 1 1) at 300 K by simultaneous evaporation of both Ni and Al from NiAl crystal material. The bimetal layer was oxidized at 300 K until saturation and annealed gradually to 1200 K. During oxygen adsorption, only aluminum is oxidized. Annealing of the oxidized layer to 1200 K leads to the formation of a well-ordered aluminum oxide. The HREEL spectra show the characteristic Fuchs–Kliever phonons of Al2O3 (410, 620 and 885 cm−1). During annealing, Ni diffuses into the Cu(1 1 1) substrate. The LEED pattern of the ultrathin oxide layer has a hexagonal structure with a lattice constant of 3.1 Å, which corresponds to the distance between two oxygen ions in the aluminum oxide.