The influence of impurities on quantum plasticity of β-Sn crystals

The influence of slight In, Cd, and Zn dopes (0.01 at.%) on the temperature dependences of plasticity properties of β-Sn single crystals was studied in the range 0.5 K < T < 4.2 K. The plastic deformation of the samples was responsible for by dislocation slipping in the (100)<010> system. It has been previously found that in pure β-Sn the main obstacles to dislocation motion in this slip system are Peierls barriers. Moreover, there exists a threshold temperature Tg ∼ 1.2 K above which the dislocation surmount the barriers owing to thermal fluctuations (thermal activated plasticity) and below which - by way of quantum mechanical tunneling (quantum plasticity). The investigation under consideration demonstrates that a slight doping of β-Sn with different impurities retains the determining effect Peierls relief on dislocation mobility at low temperatures. At the same time it results in a considerable shift of Tg towards higher temperatures (δTg ∼ 0.2-1 K), that is the temperature range of quantum plasticity becomes broader. The threshold temperature shift depends in a complicated way on power of impurity atoms that create local barriers to dislocation slip. The modern theory state makes it impossible to interpret this dependence unambiguously.