講演情報
[18p-A36-4]Nanoscale High-Transition Temperature Josephson Junctions and SQUIDs
〇Shane Cybart1 (1.UC Riverside)
キーワード：
superconductor、Josephson junction、helium ion beam
Focused helium ion beam nanolithography is a promising approach for fabrication of high-transition temperature superconductor circuits. With this method, a 0.5 nm diameter beam of 40-kV helium ions is scanned over the material, which undergoes a metal-to-insulator transition, due to ion beam induced disorder. Regions converted to insulators can be as narrow as 2 nm and serve as Josephson junctions and SQUIDs. Our laboratory has investigated the helium ion beam process and report the electronic transport properties of Josephson junctions fabricated from a range of different ion doses. At doses below 200 ions /nm the junctions exhibit superconductor-normal metal-superconductor (SNS) properties. These SNS junctions have higher resistances and less excess current than masked ion beam junctions. For higher ion beam doses greater than 300 ions/nm, we observe Josephson junctions with superconductor-insulator-superconductor (SIS) properties. In these devices the voltage state resistance increases with decreasing temperature which suggests that the intrinsic shunt is behaving as an insulator with hopping conduction. We correlate these transport properties with Monte Carlo ion implantation simulations which estimate the extent and spatial distribution of the ion beam induced disorder.
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