Atomic transport in metastable compounds: Case study of self-diffusion in Si-C-N films using neutron reflectometry

The investigation of atomic mobilities in transient metastable phases is a challenging task in diffusion science. For amorphous silicon carbonitrides we identified a transient metastable bonding configuration by Fourier-transform infrared spectroscopy on samples annealed in a defined time-temperature domain. We demonstrate that it is possible to determine nitrogen self-diffusivities in this state using neutron reflectometry. The results revealed that the diffusion experiments on this system are feasible only if very short diffusion lengths on the order of 1 nm and very low diffusivities can be measured, as it is the case for neutron reflectometry technique applied in our studies.