Oxidized amorphous-silicon superconducting tunnel junction barriers

A systematic study of the behavior of oxidized amorphous silicon layers as tunneling barriers in transition-metal-based superconducting tunnel junctions is reported. These barriers are found to work universally well, provided the native oxide of the base electrode has a sufficiently low conductance to block pinholes. For silicon layers larger than ∼2 nm the properties of the barriers are found to be independent of the base electrode and lead to a simple model of the barrier which should be useful for further applications.