Diffusion of ~(71)Ge in Molybdenum Disilicide

摘要

The radiotracer ~(71)Ge was used to study diffusion in oriented single crystals of MoSi_2 . Ge was chosen in order to simulate Si self-diffusion. ~(71)Ge was produced by neutron activation and implanted below the sample surface. Diffusion was measured for two different oriem ations of single crystals with the tetragonal C11_b crystal structure. The diffusion annealings were carried out in a temperature range of 900 K to 1250 K. We found a surprisingly fast Ge diffusion and a relatively high anisotropy between both principal directions of the crystal. Diffusion perpendicular to the tetragonal axis is about a factor of 5 faster than parallel to the axis. The activation enthalpies are very similar for both principal directions: Q = 190 +- 5 kJmol~(-1) for <100> and Q = 196 +- 3 kJmol~(-1) for <001>.