An analytical framework for quantifying radiation-enhanced diffusion coefficients of H and He in nanometric freestanding membranes under high-radiation environments

Irradiation-driven diffusion plays a central role in a broad range of microstructural phenomena induced by intense ion fluxes. Quantifying radiation-enhanced diffusion coefficients, D RED , in nanometric volumes is therefore essential for identifying materials capable of withstanding continuous irradiation while preserving their structural and functional integrity. Here, we present an analytical framework that uses two experimentally accessible quantities—the membrane thickness, L , and the characteristic saturation time, τ —to quantify radiation-enhanced diffusion coefficients for H/He in nanometric freestanding membranes. Within a Fickian slab model, the dominant diffusion mode gives D RED = L 2 / ( π 2 τ ) . Applying this framework to experimental data on saturated H and He uptake in 20–30 nm amorphous Ta 2 O 5 membranes, the analysis yields D RED = 1 0 − 19 – 1 0 − 20 m 2 s −1 at damage rates of 3– 6 × 1 0 − 3 dpa s −1 . The corresponding diffusion length, D RED τ ≈ 10 nm , is commensurate with the membrane thickness, indicating that the approach probes irradiation-driven transport in truly nanometric volumes.