Physica Status Solidi (C) Current Topics in Solid State Physics
Volume:
6
Issue:
11
Conference title:
International Conference on Positron Annihilation (15., 2009, Kolkata)
Conference title:
15th International Conference on Positron Annihilation (ICPA-15)
Venue:
Kolkata
Year of conference:
2009
Date of conference beginning:
18.01.2009
Date of conference ending:
23.01.2009
Year:
2009
Pages from - to:
2364-2366
Language:
Englisch
Abstract:
Hydrogen absorbed in crystalline solids causes a lattice expansion and the formation of hydride phases. Contrary to free standing bulk samples, thin films are fixed at substrates, which prevent their in-plane expansion. This makes hydrogen-induced expansion of thin films highly anisotropic and leads to the formation of high stresses in hydrogen loaded thin films. As a consequence, lattice defects may be created in thin films loaded with hydrogen. This work reports about defects created by hydrogen loading in epitaxial Pd films deposited on Al(2)O(3) substrates by cold cathode beam sputtering. Hydrogen-induced defects are characterized by positron annihilation spectroscopy performed with variable energy slow positron beams. Extended studies of defect depth profile and its development with increasing concentration of hydrogen are performed by measurement of Doppler broadening of annihilation profile using a continuous positron beam. Selected states are investigated also by positron lifetime spectroscopy on an intense pulsed positron beam. Firstly, the microstructure of virgin films is characterized. Subsequently, the hydrogen concentration in the films is increased step-by-step by electrochemical charging. The development of the film microstructure and the evolution of defects are investigated. «
Hydrogen absorbed in crystalline solids causes a lattice expansion and the formation of hydride phases. Contrary to free standing bulk samples, thin films are fixed at substrates, which prevent their in-plane expansion. This makes hydrogen-induced expansion of thin films highly anisotropic and leads to the formation of high stresses in hydrogen loaded thin films. As a consequence, lattice defects may be created in thin films loaded with hydrogen. This work reports about defects created by hydrog... »