Oxygen-rich polycrystalline magnesium oxide—A high quality thin-film dielectric

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Abstract
Sputtering of a magnesium target with a beam of argon ions in the presence of a partial pressure of reactive oxygen gas has been found to yield smooth MgOx thin‐film dielectrics with low electrical loss, good mechanical stability, and excellent reproducibility. The films consist of polycrystalline MgO with a grain size ≲50 Å and an OH‐containing component. The thickness dependence of the areal capacitance is discussed in the context of a two‐layer model in which this oxygen‐rich phase (x≂1.4) overlays a thin (≲40 Å) stoichiometric phase (x≂1.0). Observation of superconducting tunneling characteristics in trilayer Au‐MgOx‐Pb structures confirms pinhole‐free coverage which may have possible application as artificial tunnel barriers.