Self-diffusion experiments were carried out on monocrystalline silicon at 900C by using a method that was based on neutron reflectometry in combination with 29Si/28Si isotope multilayers. The experimental reflectivity pattern showed artificial Bragg peaks due to isotope periodicity and was fitted by the program Parratt32. Diffusivities were calculated from the roughness parameter of the isotope interfaces. The results were compared to that one obtained from a simple analytical expression on the reduction of the Bragg peak. The results showed that both methods deliver identical diffusivities within error limits. The diffusivity of 4 x 10−22m2/s did not depend upon annealing time for diffusion on a length scale of 1 to 6nm and was in good accordance to literature data, ranging between 1 and 10 x 10−22m2/s. The results demonstrated that the neutron reflectometry method was well suited to determine self-diffusivities in single crystalline silicon at very short length scales.

A Neutron Reflectometry Study on Silicon Self-Diffusion at 900C. E.Hüger, R.Kube, H.Bracht, J.Stahn, T.Geue, H.Schmidt: Physica Status Solidi B, 2012, 249[11], 2108-12