Determination of elastic constants in thin films using hydrogen loading

By measuring stress and strain that build up in thin films during hydrogen absorption, the elastic constants of the films can be determined, if a one-dimensional elastic behavior occurs only. This will be demonstrated for hydrogen absorption in Nb films. The in-plane stress is determined from the substrate curvature that is measured by using a two-beam laser setup. The out-of-plane strain is measured via x-ray diffraction. Furthermore, this method allows us to distinguish whether the film is plastically or elastically deformed by checking the reversibility of the stress-strain curve. In the case of a 250-nm-thick Nb film, the elastic constants obtained are similar to that of bulk Nb. (C) 1999 American Institute of Physics. [S0003-6951(99)00405-2].