The local control of H mobility in thin films in combination with an optical indicator which exhibited H concentration dependent colors allows to visualize H diffusion in solids. The large mobility of H in metals and the possibility to tune it over several orders of magnitude makes thin film metal hydrides ideal systems. Planar structures such as prisms could be achieved, allowing to investigate the response of H diffusion fronts as they encounter these structures. Evidence for refraction-like phenomena at interfaces separating areas of different effective diffusivities were presented. The behaviour of the diffusion front could be described by a modified Snell's law, where the square root of the front mobility in the respective media played the role of the refractive index.

Refraction-Like Behaviour of Hydrogen Diffusion Fronts. A.Remhof, R.J.Wijngaarden, R.Griessen: Journal of Alloys and Compounds, 2003, 356-357, 300-4