Tracer self-diffusion and electromigration in thin tin films

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Abstract
A nondestructive tracer‐scanning technique was devised to study lateral self‐diffusion and electromigration in evaporated thin Sn films. The diffusional spreading and migration of tracer distributions of Sn119m in thin Sn film matrices was recorded over a temperature range 142–213 °C. Determination of the profile shape enabled the diffusivity D to be unfolded, while the profile shift provided values of the migration velocity V. The temperature‐dependent results may be summarized as follows: (1) D= (1.8+1.9−0.9) ×10−5 exp(−10 700±700/RT) cm2/sec; (2) V= (1.07+1.10−0.54) ×10−4/T exp(−9800 ±650/RT) cm/sec at a current density of 1×104 A/cm2; and (3) the direction of self‐electrotransport is toward the anode at all temperatures. From these data, values of the effective valence Z* and defect resistivity were derived from the Nernst‐Einstein and Huntington formulas describing electrotransport. The results are consistent with a bulk‐assisted grain‐boundary transport mechanism involving a vacancy defect.