Effect of impurities on the quantum plasticity of β-tin single crystals

The effect of small additions (0.01 at. %) of indium, cadmium, and zinc impurities on the temperature dependences of the plasticity characteristics of beta-tin single crystals in the interval 0.5 K < T < 4.2 K is studied. Plastic deformation of the samples occurred by means of dislocation slip in the system (100)< 010 >. It has been shown in previous work that Peierls barriers are the main obstacles to the motion of dislocations of this system in pure beta-tin. There exists a threshold temperature T-g approximate to 1.2 K above which dislocations overcome barriers by means of thermal fluctuations (thermally activated plasticity) and below which by means of quantum-mechanical tunneling (quantum plasticity). The present investigation shows that for weak doping of beta-tin by various types of impurities the influence of Peierls relief on dislocation mobility remains dominant at low temperatures but T-g shifts appreciably in the direction of high temperatures (delta T-g approximate to 0.2-1 K), i.e. the temperature interval of quantum plasticity becomes wider. The experimentally observed shift of the threshold temperature depends in a complicated manner on the size of the impurities atoms, which create local barriers for dislocation slip. Current theory cannot give an unequivocal interpretation of such a dependence. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3418993]