Direct-write Helium Ion Lithography of High-Transition Temperature Superconducting Electronics

Abstract:

In 1987 the discovery of high transition temperature (high-TC) superconductivity in ceramic materials at temperatures around 90 degrees Kelvin set off a frenzy of research in the development of high-TC electronics, motivated by the prospects of electronics operating in low cost liquid nitrogen at 77 K opposed to 4 K liquid helium. Unfortunately, researchers soon discovered that these new materials were much more difficult to process into devices than conventional metal low transition temperature (low-TC) superconductors. High-TC materials are very anisotropic and the superconducting properties vary along the different crystallographic directions which severely complicates manufacturing of the basic building blocks of superconducting electronics: Josephson junctions. Furthermore, the length scale of superconductivity in high-TC ceramics is very short compared to low-TC metals. Despite these challenges many high-TC Josephson junction manufacturing techniques have emerged over the last three decades but none of these techniques is able to generate large numbers of junctions with predictable characteristics necessary for large scale circuits. Prior manufacturing techniques rely on small centimeter sized substrates that must be processed one-at-a-time and rigorously tested one-by-one to find the few devices with suitable characteristics. The low yields and low throughput has kept the costs too high for widespread high-TC superconductor electronic applications. For a single low-noise superconducting quantum interference device (SQUID) magnetic field sensor, (the simplest of all superconducting electronic circuits containing only two Josephson junctions), the cost is roughly $10,000 each. For systems requiring hundreds of sensors like non-evasive magnetoencephalography (MEG) brain imaging machines, the sensors alone would cost millions of dollars! Additionally, the low manufacturing throughput is even more prohibitive than the cost. The machinery and test equipment to build just one sensor per week costs 2 million dollars and fills a 2000 square foot lab. Recently, my group has demonstrated a new scalable nanomanufacturing method of high TC electronics using the finely focused beam from a helium ion microscope, which has the potential to deliver large numbers of high-quality circuits while at the same time reducing the costs by orders of magnitude. In this seminar I will present some of the novel characteristics and applications of this new remarkable technology.

Biography:

Dr. Shane Cybart is a scientist and principle investigator of the Oxide Nano Electronics Laboratory at UC San Diego. He obtained a BS degree in physics from the University of Michigan in 2000 and a PhD in Materials Science from the UC San Diego in 2005 studying high-transition temperature Josephson devices. He continued his work in superconducting electronics as a post-doctoral research at UC Berkeley from 2006-2009, developing applications for arrays of superconducting quantum interference devices. More recently, he served as a project scientist at UC Berkeley and the Lawrence Berkeley Laboratory on multiferroic and magnetic oxides. He is currently leading a group of researchers at UC San Diego to develop oxide electronic devices for a diverse range of applications.