Diffusion of ~(71)Ge and ~(99)Mo in molybdenum disilicide

摘要

Diffusion studies of heterodiffusion of germanium and self-diffusion of molybdenum in molybdenum disilicide were carried out using the radiotracer serial sectioning technique. ~(71)Ge was used to simulate silicon self-diffusion due to the lack of a suitable silicon tracer. Diffusivities were measured for two different orientations of single crystals with the tetragonal C11_b structure. Diffusion annealings were carried out in the temperature range from 830 K to 1970 K. We found a surprisingly fast germanium diffusion and a relatively high anisotropy between both principal directions of the tetragonal lattice. The activation enthalpies for ~(71)Ge are Q = 200+2 kJ/mol for <100> and Q = 169+-2 kJ/mol for <001>. Diffusion of molybdenum is by orders of magnitude slower than germanium. The activation enthalpy for ~(99)Mo is Q = 495+-14 kJ/mol for <001>. Diffusion in both sublattices is decoupled and occurs very likely via an independent sublattice vacancy mechanism.