Self-Diffusion in Amorphous Silicon

The present Letter reports on self-diffusion in amorphous silicon. Experiments were done on ²⁹Si/^natSi heterostructures using neutron reflectometry and secondary ion mass spectrometry. The diffusivities follow the Arrhenius law in the temperature range between 550 and 700°C with an activation energy of (4.4 ± 0.3) eV. In comparison with single crystalline silicon the diffusivities are tremendously higher by 5 orders of magnitude at about 700°C, which can be interpreted as the consequence of a high diffusion entropy.