Understanding the Role of Hydrogen and Oxygen in Electronic Phase Changes of Nickelates
Laura Guasco (Max Planck Institute for Solid State Research, Heinz Maier-Leibnitz Zentrum)
Rebecca Pons (Max Planck Institute for Solid State Research)
David Cortie (Australian Nuclear Science and Technology Organisation)
Lars J. Bannenberg (TU Delft - RID/TS/Instrumenten groep)
Peter Wochner (Independent researcher)
Eberhard Goering (Max Planck Institute for Solid State Research)
Peter Nagel (Karlsruhe Institut für Technologie)
Stefan Schuppler (Karlsruhe Institut für Technologie)
Eva Benckiser (Max Planck Institute for Solid State Research)
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Abstract
Many electronic and electrochemical devices rely on the exchange of light elements such as hydrogen and oxygen with the environment. Understanding and tailoring the device functionality requires accurate information about the concentration and chemical bonding of such species inside a solid, which is particularly difficult if several species are exchanged. In LaNiO3 thin films in situ transport experiments reveal a re-entrant metal–insulator transition upon hydrogen exposure. The origin of this unusual behavior can be understood by combining information about the stoichiometry and chemical bonding of hydrogen and oxygen as determined by neutron reflectometry and x-ray absorption spectroscopy, respectively. In addition to the metallic parent phase, an insulating phase with composition LaNiO2.65 and a re-entrant metallic phase with composition LaNiO2.15(OH)0.5 are identified. They can be inter-converted by redox reactions in different external environments. The methodology employed offers new insights into the mechanisms underlying the influence of hydrogen in functional devices.
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