Dielectric relaxation study of hydrogen exposure as a source of two-level systems in Al2O3

An important question in the manufacture of superconducting electronics is how to control the two-level systems found in amorphous insulators. The present article shows that hydrogen has a marked impact on the two-level systems in thin films of reactively sputtered Al2O3, a standard tunnel oxide for Josephson junctions. The magnitude of dielectric relaxation current in Al2O3 films, believed to be caused by two-level systems, is shown to increase monotonically with the flow rate of H2 into the chamber during deposition. This points toward a potential need for controlling hydrogen during the manufacture of superconducting electronics utilizing Al2O3.