Nanomanufacturing of High-temperature Superconductor Circuits Using Focused Ion Beams

研究目标是探索高温陶瓷氧化物超导体电子器件的高通量、大面积纳米制造。在液氮温度下，陶瓷氧化物材料具有超导性，即在不产生电阻的情况下导电。这些超导体是各向异性的，电导率在不同的晶体学方向上变化，这使得制造这些电路的基石约瑟夫森结变得复杂。聚焦离子束技术的最新进展为高温超导体电子器件开辟了一种新的无电阻直接写入纳米制造方法，具有提高性能和降低成本的潜力。这项研究涉及多个科学和工程学科，包括纳米制造、超导体电子学和低温学。该项目将培养学生在薄膜生长、纳米制造、数学建模、先进的低噪声电子传输测量技术以及批判性思维方面的知识和技能，为学生在科学技术工程和数学领域的职业生涯做好准备。该研究所的教师导师计划将用于为妇女和代表性不足的少数民族学生创造机会。从高性能低温计算到高温半导体放大器等领域的超导体电子工业将受到影响。制造高转变温度（高tc）陶瓷氧化物超导体电路有几个挑战。它的各向异性晶体结构使约瑟夫森结的制造复杂化。约瑟夫森结的优值随电路临界维数呈指数级增长。高性能器件需要低于10纳米的特征尺寸。即使是1纳米的变化也会导致性能值的大幅波动。尽管存在这些挑战，在过去的三十年中出现了许多高tc结制造技术，但没有一种技术能够产生大量具有高产量和可预测性能的约瑟夫森结。该奖项利用精细聚焦的0.5 nm氦离子束直接修饰超导材料，用于精确制造用于约瑟夫森结的纳米线。该方法的关键在于材料对晶格中氧的顺序非常敏感，而这种顺序可以通过光离子照射而改变。将这一改变区域限制在纳米尺度上，可以直接在材料中产生平面内的隧道屏障，而不会产生电阻或蚀刻。该方法与市售的在相对便宜的大面积蓝宝石晶圆上的高tc超导体薄膜兼容。在该过程的参数空间中有许多变量，如束流、剂量、膜厚度和空间约瑟夫森结尺寸。目的是研究这些参数的影响，吞吐量，产量和性能均匀性的数字。

The research objective is to investigate high-throughput, large-area nanomanufacturing of high-temperature ceramic oxide superconductor electronics. At liquid nitrogen temperature, ceramic oxide materials superconduct, i.e., they conduct electricity without offering resistance. These superconductors are anisotropic and the conductivity varies in different crystallographic directions, which complicates the manufacturing of Josephson junctions, the building-blocks of these circuits. Recent advances in focused ion beam technology has opened up a new resistless direct-write nanomanufacturing method for high-temperature superconductor electronics that has the potential to improve performance and reduce cost. This research involves several disciplines in science and engineering including nanofabrication, superconductor electronics, and cryogenics. The project will develop knowledge and skills in film growth, nanofabrication, mathematical modeling, advanced low noise electron transport measurement techniques as well as critical thinking to prepare students for careers in Science Technology Engineering and Mathematics. The Institute's Faculty Mentor Program will be utilized to create opportunities for women and underrepresented minority students. The superconductor electronics industry will be impacted in areas from high performance cryogenic computing to high temperature semiconductor amplifiers.The challenges to fabricating high transition temperature (high-Tc) ceramic oxide superconductor circuits are several. Its anisotropic crystal structure complicates the manufacture of Josephson junctions. The figure of merit for Josephson junctions scales exponentially with the circuit critical dimension. High performance devices require feature sizes in the sub-10 nanometer regime. Variation of even 1 nm can result in large fluctuations in the figure of merit. Despite these challenges many high-Tc junction manufacturing techniques have emerged over the last three decades but none is able to generate large numbers of Josephson junctions with high-yield and predictable properties. This award utilizes a finely focused 0.5 nm helium ion beam to directly modify the superconducting material for the precise fabrication of nanowires for Josephson junctions. The key to this method is that the material is very sensitive to the oxygen ordering in the crystal lattice which can be altered by light ion irradiation. Restricting this altered region to the nanoscale allows for the creation of in-plane tunneling barriers directly in the material with no resists or etching. The method is compatible with commercially available high-TC superconductor films on relatively inexpensive large area sapphire wafers. There are a number of variables in the parameter space for this process, such as beam current, dose, film thickness, and spatial Josephson junction dimensions. The goal is to study the impact of these parameters throughput, yield, and figure of merit uniformity.