Spannungen, Dehnungen und Lage der Phasengrenzen in dünnen Nb- und Y-Schichten bei Wasserstoffbe- und -entladung

Abstract

In this work the influence of the stresses induced by hydrogen loading on the position of phase boundaries in niobium and yttrium thin films is studied. The films were loaded with hydrogen electrochemically. The hydrogen concentration was calculated by use of Faraday"s law. The stresses were measured using an optical beam deflection setup. The strains and the position of the phase boundaries were determined in situ during hydrogen (un-)loading at the synchrotron. The results were compared to a one-dimensional linear elastic model using bulk elastic constants and bulk hydrogen induced expansion data. The measurements on epitactic niobium thin films of different thicknesses and on nanocrystalline niobium thin films on thin polymer film substrates in comparison to nanocrystalline films on silicon substrates showed a strong correlation between the hydrogen induced stresses and the shift of phase boundaries in these thin films. Measurements on yttrium thin films however revealed only small stresses built up by hydrogen loading and unloading. Additionally performed synchrotron measurements could show that there is in contrast to the literature no significant shift of phase boundaries compared to the bulk yttrium-hydrogen system.