Nanofabrication of High Transition Temperature Superconductive Electronics with Focused Helium Ion Irradiation

In navigating the post–Moore’s law era, superconductive electronics offer a compelling architecture, enabling ultrafast switching, low power dissipation, and functionality across digital, stochastic, neuromorphic, and quantum regimes. However, practical, scalable, and reliable fabrication of superconductive circuits remains at a disadvantage compared to currently commercialized technologies, due to both fabrication complexity and the need for cryogenic operation.

The use of cuprate materials, such as YBa₂Cu₃O₇₋δ (YBCO), are desirable due to having superconducting transitions above the liquid nitrogen temperature. However, their anisotropic crystal structure renders conventional multilayer fabrication processes infeasible. In particular, the realization of Josephson junctions—a fundamental component of superconductive electronics—has remained challenging using the already highly developed techniques for low–critical temperature superconductors. Josephson junctions consist of a nanoscale non-superconducting barrier between superconducting electrodes, and their performance is highly sensitive to barrier structure and uniformity.

Focused helium ion beam (FHIB) lithography locally modifies superconducting materials with nanometer precision. Using a sub-nanometer beam, select regions of a YBCO film can be tuned into superconducting, metallic, or insulating regions as a function of ion dose, enabling maskless writing of circuit elements.

I will present fabrication methods and example devices of superconductive circuits entirely within a single thin film using FHIB lithography. Ion fluence serves as a continuous control parameter, enabling junctions ranging from weak links to well-defined tunnel barriers. These junctions are highly tunable and written in a maskless, interface-free process through controlled defect introduction.

We establish practical design rules that relate ion dose, geometry, and material response to predictable device behavior, enabling realization of Josephson junctions and resistive, inductive, and capacitive elements within a YBCO film. This enables a fully FHIB-defined superconductive electronics architecture with high device density, reduced flux trapping, and rapid prototyping capability, providing a scalable technology toward next-generation superconductive electronics.