物理学教室 談話会(12月19日)

コロキウム・談話会 2024/12/11

演目:Exploring Nanoscale Superconducting Phenomena and Devices Through Advanced Ion Beam Patterning Techniques 
講師:Shane Cybart教授
所属:カリフォルニア大学リバーサイド校
日時:2024年12月19日(木) 11時-12時30分
場所:理学部1号館233号室

In his famous 1959 lecture, "There's Plenty of Room at the Bottom," Richard Feynman foreshadowed the rise of nanoengineering, suggesting that finely focused electron and ion beams could one day allow us to precisely engineer structures at the atomic level. Today, electron beam lithography systems and gallium focused ion beams are commonplace in nanotechnology, capable of creating structures on the order of tens of nanometers. However, scaling down to sub-10 nm has been a significant technological challenge, until the advent of gas field ion sources (GFIS) over the past decade.

The GFIS utilizes a tungsten wire sharpened to just three atoms. Helium gas is field-ionized by one of these atoms, producing a helium ion beam with a diameter of only 0.25 nm. This tool is proving invaluable for sub-10 nm structuring of materials. Helium ions offer distinct advantages: helium is small, chemically inert, and allows for direct modification of material properties without the need for resists or significant material removal.

My research group has been using GFIS for the direct patterning of ceramic high-temperature superconducting materials, facilitating fundamental tunneling studies in cuprate superconductors and enabling the creation of novel quantum devices. The helium ion beam induces nanoscale disorder, converting the material’s electrical properties from superconducting to insulating. We have demonstrated insulating features as small as 2 nm, leading to the development of unique quantum devices. Much of this progress stems from the sensitivity of high-temperature superconductors to irradiation, particularly due to the loosely bound oxygen atoms in their crystal lattice that are easily displaced.

In this seminar, I will detail the GFIS technology, its role in enabling nanoscale tunneling experiments to study cuprate superconductors, and highlight some of the innovative devices we’ve realized. new insights gained into cuprate superconductors from nanoscale tunneling experiments. I will conclude by presenting several applications including magnetic field sensing, high frequency detection and adiabatic quantum flux parametron digital logic.

BIO:
Professor Shane Cybart earned his Ph.D. in Materials Science and Engineering from UC San Diego in 2005, specializing in nanofabrication and the device physics of high-transition temperature Josephson devices. From 2006 to 2009, he continued his research in superconductive electronics as a postdoctoral researcher at UC Berkeley. He remained at UC Berkeley and later UC San Diego as a scientist, developing oxide electronic devices for a wide range of applications from 2009 to 2016.

In June 2016, Professor Cybart joined the Bourns College of Engineering at the University of California, Riverside. In 2019, he was awarded a U.S. patent for the invention of the helium ion Josephson junction. He is currently a Professor of Electrical Engineering and serves as the Director of the California Institute for Telecommunications and Information Technology (Calit2) at UC Riverside, as well as the Director of the Center for Superconductive Quantum Electronics.

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