Solute Trapping: Comparison of Theory with Experiment

The dependence of the nonequilibrium partition coefficient k of Bi in Si upon solidification velocity v has been measured with sufficient accuracy to distinguish between proposed solute-trapping mechanisms. For the range of measured velocities, 2-14 m/s, we observe a much more gradual increase in k with increasing v than those previously reported and no evidence for a "saturation" effect, i.e., dkdv0 at k<1. The continuous-growth model of Aziz fits the data quite well; the Aziz stepwise-growth model and the two-level Baker model yield values of dkdv that are too high.