Abstract
Hydrogen loading causes a significant volume expansion, which is isotropic in free-standing bulk materials. Contrary to bulk samples, thin films are clamped to an elastically stiff substrate, which prevents in-plane expansion.
Hence, volume expansion of a thin film is strongly anisotropic because it expands only in the out-of-plane direction. High internal stresses introduced during hydrogen loading may lead to a situation when detachment of film from the substrate is energetically favorable.
In the present work, we studied hydrogen-induced buckling of thin Pd films using a multi-scale approach. Defects in buckled films were characterized on the atomic level by positron annihilation spectroscopy combined with microstructure studies by transmission electron microscopy.
Meso-scale measurements were performed by acoustics emission. Observations at the macroscopic level were performed by optical microscopy.