Decoupling strain and finite size effects in epitaxially grown vanadium thin films for hydrogen storage

Finite size, straine, and proximity effects are often simultaneously present in nanosized metal hydrides, while it is difficult to discriminate their effect on thermodynamic properties. Here, we present quantitative strain analysis of epitaxially grown V thin films by a combination of real and reciprocal space techniques. We find that films up to ≈90 nm preserve tetragonal distortion imposed by the rigid substrate. Free from non-uniform strain profiles, we demonstrate that hydrogenated VHx films of different thicknesses (30, 60, and 90 nm) feature octahedral occupancy of H.