Thermal stability of thin Ti films on Al single crystal surfaces

Abstract

Chemical roughness and alloy formation at metallic interfaces can significantly degrade the performance of multilayer thin film magnetic device structures. We have investigated the use of Ti interlayers, one or two atoms thick, to stabilize the interface for ordered growth of Fe films on Al(100), a system characterized by considerable interdiffusion at room temperature. The practicality of the interlayer concept is strongly coupled to the stability of the interlayer at elevated temperatures. In this investigation we have characterized the structure of thin Ti layers on Al single crystal surfaces as a function of temperature using Rutherford backscattering and channeling and low-energy ion scattering. The Ti layers are shown to be stable up to temperatures of about 675 K, at which point diffusion of Ti into the Al lattice occurs. Channeling measurements show that the Ti atoms sit on Al lattice sites as substitutional impurities. The stability of the Ti film appears to increase with the packing density of the Al surface, being slightly more stable for the close-packed Al(111) surface, and diffusing into the more open Al(110) surface at a lower temperature.

Thermal and chemical stability of epitaxial Fe films grown on the Ti-stabilized Al(100) surface

“…We previously reported [32] on the stability of an 8 ML Ti film on Al(1 0 0), noting that the Ti surface peak began to decrease in area for temperatures above 300°C, and continued to decrease for annealing at temperatures up to 450°C. We attributed this decrease to Ti atoms moving into the Al substrate and occupying substrate lattice sites where the Ti atoms are shadowed by Al atoms.…”

“…This indicates that Ti atoms are being shadowed by Al or Ti atoms closer to the surface, characteristic of Ti atoms moving into the substrate and occupying substitutional sites on the fcc Al lattice. More details on the characteristic behavior of Ti substitutional site occupation in the fcc Al lattice upon thermal diffusion for Al(1 0 0) and Al(1 1 0) surfaces has been reported elsewhere [32]. Finally, to see how the interlayer thickness affects the thermal stability of the interlayer structure, we performed channeling measurements as a function of annealing temperature for Fe films deposited on the Al(1 0 0) surface with a 3 ML Ti interlayer.…”

“…The significant rise in peak area after annealing at 400°C is attributed to the onset of a major change in the Fe/Ti/Al(1 0 0) structure, possibly due to diffusion of Al atoms to the surface, and movement of Fe and Ti into the Al substrate. We discuss below, and elsewhere [32,33], the stability of the Ti film on the Al(1 0 0) surface with no Fe deposition. The annealing experiments were stopped at 400°C because of the difficulty of cleaning the Al surface following the diffusion of Fe atoms deep into the bulk of the Al crystal.…”

Fe-Al interface intermixing and the role of Ti, V, and Zr as a stabilizing interlayer at the interface

“…4 We have extensively investigated the composition, structure and stability of TM-Al single crystal systems ͑TM = Fe,Ti,Zr,Co,Ni,Pd,Ag͒ over the last several years. [5][6][7][8][9][10] For most of the systems studied, intermixing of TM atoms with the single-crystal Al substrate was observed in the first few monolayers of TM deposition before the onset of growth of TM rich films. In previous studies of interface intermixing of sputter-deposited polycrystalline bilayers, a large amount of intermixing was observed for many TM/Al systems at room temperature.…”

Galvanic Deposition of Ti atop Al 6061 Alloy

“…7 Ti thin films are typically deposited by evaporation and sputtering methods using expensive vacuum systems. [8][9][10] Electrochemical deposition is generally simpler and less expensive, but Ti electrodeposition from aqueous electrolytes is difficult due to the highly cathodic potential required. For this reason, Ti electrodeposition is typically performed from high temperature molten salts.…”