Nanomanufacturing of High-temperature Superconductor Circuits Using Focused Ion Beams

研究目标是研究高温陶瓷氧化物超导体电子学的高通量、大面积纳米制造。在液氮温度下，陶瓷氧化物材料超导性，即它们导电而不提供电阻。这些超导体是各向异性的，电导率在不同的晶体方向上变化，这使得约瑟夫森结的制造变得复杂，约瑟夫森结是这些电路的组成部分。聚焦离子束技术的最新进展为高温超导电子器件开辟了一种新的无电阻直写纳米制造方法，具有提高性能和降低成本的潜力。这项研究涉及科学和工程中的几个学科，包括纳米制造、超导电子学和低温学。该项目将培养薄膜生长、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方案将被用来为妇女和代表不足的少数族裔学生创造机会。超导电子业将在从高性能低温计算到高温半导体放大器等领域受到影响。制造高温陶瓷氧化物超导电路面临着几个挑战。其各向异性的晶体结构使约瑟夫森结的制造变得复杂。约瑟夫森结的品质因数与电路临界尺寸成指数关系。高性能设备要求特征尺寸在10纳米以下。甚至1纳米的变化也会导致品质因数的大幅波动。尽管有这些挑战，在过去的三十年里已经出现了许多高T_c结的制造技术，但没有一种能够产生大量具有高成品率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氦离子束直接修改超导材料，用于精确制造约瑟夫森结的纳米线。这种方法的关键是材料对晶格中的氧有序性非常敏感，这种有序性可以通过光离子辐照来改变。将这种改变的区域限制在纳米级，允许在材料中直接创建平面内隧道势垒，而不需要抗蚀剂或蚀刻。该方法与在相对便宜的大面积蓝宝石晶片上可以买到的高温超导薄膜兼容。这一过程的参数空间中有许多变量，例如束流、剂量、薄膜厚度和约瑟夫森结的空间尺寸。我们的目标是研究这些参数对吞吐量、成品率和品质因数一致性的影响。

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.