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We report the growth and multi-technique characterization of stoichiometric Nb3Sn/Al2O3 multilayers with good superconducting and RF properties. We developed an adsorption-controlled growth process by co-sputtering Nb and Sn at high temperatures with a high overpressure of Sn. SIS multilayers with up to 4 Nb3Sn layers of thickness 50-60 nm, separated by 5-6 nm thick Al2O3 interlayers have been grown on 2” sapphire wafers. The cross-sectional scanning electron transmission microscope images show no interdiffusion between Al2O3 and Nb3Sn and STM measurements reveled a superconducting gap corresponding to a stoichiometric Nb3Sn. Low-field RF measurements have shown that our Nb3Sn trilayer has quality factor comparable with cavity-grade Nb at 4.2 K. These results provide a materials platform for the development and optimization of high-performance SIS multilayers for SRF cavity applications.
