Tracer self-diffusion and electromigration in thin tin films

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 Sn^119m 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.