Neutron Reflectometry for the Investigation of Self-Diffusion in Amorphous Silicon

摘要

We present experiments based on neutron reflectometry in combination with ~(29)Si/~(nat)Si isotope multilayers in order to investigate the self-diffusion in amorphous silicon. Such experiments allow the detection of diffusion processes in the amorphous state on length scales below 10 nm. First results at 650 ℃ show a continuous decrease of the artificial Bragg peak produced by the multilayer, corresponding to a diffusivity of (1.1 ± 0.4) × 10~(-20) m~2/s on a length scale of 2 - 7 nm. The diffusivity is not time-dependent for annealing times between 3 min and 1 h. Compared to recent measurements in silicon single crystals by the same method, the diffusivity is higher by a factor of about 10~5.