Diffusion of 71Ge in the amorphous ceramic Si28C36N36

Abstract The objective of this research was the determination of the Si self-diffusivity in the polymer-derived amorphous ceramic Si 28 C 36 N 36 , which consists of two amorphous phases, a-Si 3 N 4 and a-C. This diffusivity is of technological importance, since it contributes to the ceramic’s transition from its intermediate amorphous to its final crystalline state. The Si self-diffusion was simulated by the diffusion of 71 Ge. This was done by a radiotracer technique, in which radioactive 71 Ge atoms were implanted. After diffusion annealing, the specimens were serially sectioned by Ar + -beam sputtering. The 71 Ge diffusion coefficients obey Arrhenius laws in the temperature regime investigated (850–1300°C) with a pre-exponential factor of 0.2 m 2 s −1 and a diffusion enthalpy that increases from 4.6 eV in as-produced to 5.5 eV in 1350°C-pre-annealed specimens. These data are interpreted in terms of 71 Ge diffusion in the a-Si 3 N 4 phase which is mediated by smeared-out thermal vacancies.