Atomic transport in metastable compounds: Case study of self-diffusion in $\text{Si}-\text{C}-\text{N}$ 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.

Figure 1

(Color online) FTIR spectrum of as-deposited and annealed $\text{Si}-\text{C}-\text{N}$.

Figure 2

(Color online) Integrated FTIR intensity of the bands at $2240{\text{cm}}^{-1}$ (marked with dots) and around $900{\text{cm}}^{-1}$ (marked with crosses) after subsequent anneals at $867°\text{C}$ (lines are a guide to the eye).

Figure 3

(Color online) Decrease in first-order Bragg peak after annealing the $\text{Si}-\text{C}-\text{N}$ isotope multilayer at $867°\text{C}$ (lines are a guide to the eye).

Figure 4

(Color online) Average nitrogen self-diffusivity as a function of time, according to Eq. (1) (lines are a guide to the eye).

Figure 5

(Color online) Self-diffusion lengths determined according to Eq. (2).