Atomic and electronic structure of amorphous Al–Zr alloy films

Abstract

Amorphous Al73Zr27 alloy film, grown and then subjected to heat treatments at 400 and700 °C,was studied using a combination of x-ray diffraction and soft x-ray spectroscopic techniques. The AlL2, 3 and Al K x-ray absorption spectroscopy (XAS) and AlL2, 3 x-ray emission spectroscopy (XES) used allowed probing the unoccupied and occupied Al3s, d states and unoccupied Al 3p states in the sample studied. An irreversibletransition from amorphous alloy to a mixture of polycrystalline alloy and amorphousalloy, and then to an amorphous oxide phase was observed. After the annealing at400 °C theAl L2, 3 spectra obtained by XAS could be explained as sums of spectra from amorphousAl73Zr27 alloy and (poly)crystalline Al. This indicates that the sample consists of a mixture of Al-richcrystalline and Zr-enhanced amorphous alloys, as compared to the stoichiometry of the as-depositedAl73Zr27 sample, and that the electronic wavefunctions in the crystalline and amorphous regions canbe considered to be confined within the respective regions. The relative amounts of Alatoms were found to be around 1:3 in the crystalline and amorphous phases,respectively, as deduced from the analysis of changes in the electronic structure using AlL2, 3 XAS data. The interpretation was confirmed by the Al K XAS and AlL2, 3 XES. Upon furtherannealing at 700 °C the polycrystalline phase transformed into amorphous oxide, while the amorphous alloyphase underwent gradual oxidation. The important finding was that the greater part of thesample remained in the amorphous state throughout the temperature regimesdescribed.