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

Abstract

The growth of ultrathin films of Al2O3 on Cu(111) in the temperature range 300–1200K 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(111) at 300K by simultaneous evaporation of both Ni and Al from NiAl crystal material. The bimetal layer was oxidized at 300K until saturation and annealed gradually to 1200K. During oxygen adsorption, only aluminum is oxidized. Annealing of the oxidized layer to 1200K leads to the formation of a well-ordered aluminum oxide. The HREEL spectra show the characteristic Fuchs–Kliever phonons of Al2O3 (410, 620 and 885cm−1). During annealing, Ni diffuses into the Cu(111) substrate. The LEED pattern of the ultrathin oxide layer has a hexagonal structure with a lattice constant of 3.1Å, which corresponds to the distance between two oxygen ions in the aluminum oxide.