Kitada Masahiro

Effects of temperature, thickness and atmosphere on mixing in Au-Ti bilayer thin films

The interdiffusion and intermetallic compound formation of Au-Ti bilayer thin films annealed at 125 to 350 °C have been investigated. The bilayer thin films were prepared through electron beam deposition at comparatively low temperature. The interdiffusion of annealed specimens was examined by measuring electrical resistance and the depth-composition profile, and by observation using a transmission electron microscope. Interdiffusion between the thin films was detected at temperature above 175°C in a vacuum of 10−4 Pa. The starting temperature at which interdiffusion occurred decreases with lowering annealing vacuum. The intermetallic compounds AuTi, Au4Ti, Au2Ti and Ti3Au form during annealing at over 250 °C. The activation energies of Au in Ti and Ti in Au obtained by the penetration depth are approximately 0.45 and 0.41 eV, respectively. These measurements indicate that the diffusion is controlled by a short-circuit mechanism. The diffusion of Ti species in Au depends on the annealing vacuum and Au thickness.

The effect of annealing on the magnetic properties of permalloy films in permalloyTa bilayers

Abstract The reaction between permalloy and Ta bilayer thin films annealed at 100 to 450°C, and the effects of sputtering order of permalloyTa bilayer thin films on the magnetic properties of the permalloy layer have been investigated. The interdiffusion onset temperature between permalloy and Ta in Ta/permalloy bilayer thin films is lower than that in permalloy/Ta bilayer films. The coercivity of the permalloy layer increases and the magnetostriction changes towards positive values due to the preferential diffusion of Ni from the permalloy layer into the Ta layer. The average grain diameters of permalloy layers are approximately 5 nm for glass substrate and 10 nm for Ta substrate. This is thought to be due to the difference in chemical affinity between glass and Ta substrates. The difference between the average grain diameters is the main cause of the difference in interdiffusion.