Low Leakage Superconducting Tunnel Junctions with a Single Crystal Al2O3 Barrier
National Institute of Standards and Technology Boulder United States
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We have developed a two-step growth scheme for single-crystal Al2O3 tunnel barriers. The barriers are epitaxially grown on single-crystal rhenium Re base electrodes that are grown epitaxially on a sapphire substrate, while polycrystalline Al is used as the top electrode. We show that by first growing an amorphous aluminum Al oxide layer at room temperature and crystallizing it at a high temperature in oxygen environment, a morphologically intact single-crystal Al2O3 layer is obtained. Tunnel junctions fabricated from these trilayers show very low subgap leakage current. This single-crystal Al2O3 junction may open a new venue for coherent quantum devices.