MICROSTRUCTURAL TRANSITIONS IN TITANIUM-ALUMINUM THIN-FILM MULTILAYERS

This paper presents the results of a detailed study of titanium-aluminum thin film multilayers fabricated using ultrahigh vacuum magnetron sputtering. Transmission electron microscopy (TEM) techniques have been used to characterize the structure of these multilayers and to study the various structural transitions as a function of the bilayer thickness. Evidence is presented which indicates the existence of a titanium based face-centered cubic structure in these films, below a critical bilayer thickness. Upon decreasing the bilayer thickness further, both the Ti and Al layers adopt the hexagonal close-packed structure and are coherent with each other. The evolution of thin film microstructures has been studied using high resolution TEM and an attempt is made to rationalize the stability of different phases based on the energetics of atomic stacking. Microstructural characterization has been complimented with resistivity measurements of the.multilayers, to investigate the relative importance of crystallographic structure, interface scattering, and grain boundary scattering on the resistivity of multilayered materials.