The low dielectric loss underlying the record performance of strained (SrTiO3)nSrO Ruddlesden–Popper films as tunable microwave dielectrics was postulated to arise from (SrO)2 faults accommodating local non-stoichiometric defects. Here, we explore the effect of non-stoichiometry on (SrTiO3)nSrO using positron annihilation lifetime spectroscopy on a composition series of 300 nm thick n = 6 (Sr1+δTiO3)nSrO thin films. These films show titanium-site vacancies across the stoichiometry series, with evidence that TiOx vacancy complexes dominate. Little change in defect populations is observed across the series, indicating the ability of Ruddlesden–Popper phases to accommodate ± 5% off-stoichiometry. This ability for defect accommodation is corroborated by scanning transmission electron microscopy with electron energy loss spectroscopy. The synthesis science work at Cornell was supported by the U.S. Department of Energy, Office of Basic Sciences, Division of Materials Sciences and Engineering, under Award No. DE-SC0002334. Sample preparation was in part facilitated by the Cornell NanoScale Facility, a member of the National Nanotechnology Coordinated Infrastructure (NNCI), which was supported by the National Science Foundation (Grant No. NNCI-1542081). This work made use of the Cornell Center for Materials Research Shared Facilities, which are supported through the NSF MRSEC program (No. DMR-1719875). B.H.G. and L.F.K. acknowledge support from the Department of Defense Air Force Office of Scientific Research (No. FA 9550-16-1-0305). The FEI Titan Themis 300 was acquired through No. NSF-MRI-1429155, with additional support from Cornell University, the Weill Institute, and the Kavli Institute at Cornell. The Thermo Fisher Helios G4 X FIB was acquired with support by NSF No. DMR-1539918. D.J.K. gratefully acknowledges the financial support provided by FRM-II to perform the high-intensity positron beam measurements at Heinz Maier-Leibnitz Zentrum (MLZ), Garching, Germany.    «

The low dielectric loss underlying the record performance of strained (SrTiO3)nSrO Ruddlesden–Popper films as tunable microwave dielectrics was postulated to arise from (SrO)2 faults accommodating local non-stoichiometric defects. Here, we explore the effect of non-stoichiometry on (SrTiO3)nSrO using positron annihilation lifetime spectroscopy on a composition series of 300 nm thick n = 6 (Sr1+δTiO3)nSrO thin films. These films show titanium-site vacancies across the stoichiometry series, with e...    »