Direct-coupled micro-magnetometer with Y-Ba-Cu-O nano-slit SQUID fabricated with a focused helium ion beam

• Published in: Applied physics letters 2018-10, Vol.113 (16), p.162602-162602
• Main Authors: Cho, Ethan Y., Li, Hao, LeFebvre, Jay C., Zhou, Yuchao W., Dynes, R. C., Cybart, Shane A.
• Format: Article
• Language: English
• Subjects: Applied physics; Concentrators; Electrical measurement; Helium ions; Ion beams; Ion irradiation; Noise measurement; Superconducting quantum interference devices; Superconductivity; Superconductivity and Superconducting Electronics; Thin films; Transition temperature; White noise; YBCO superconductors
• ISSN: 0003-6951; 1077-3118
• DOI: 10.1063/1.5048776

Direct write patterning of high-transition temperature (high-TC) superconducting oxide thin films with a focused helium ion beam is a formidable approach for the scaling of high-TC circuit feature sizes down to the nanoscale. In this letter, we report using this technique to create a sensitive micro superconducting quantum interference device (SQUID) magnetometer with a sensing area of about 100 × 100 μm2. The device is fabricated from a single 35-nm thick YBa2Cu3O7−δ film. A flux concentrating pick-up loop is directly coupled to a 10 nm × 20 μm nano-slit SQUID. The SQUID is defined entirely by helium ion irradiation from a gas field ion source. The irradiation converts the superconductor to an insulator, and no material is milled away or etched. In this manner, a very narrow non-superconducting nano-slit is created entirely within the plane of the film. The narrow slit dimension allows for maximization of the coupling to the field concentrator. Electrical measurements reveal a large 0.35 mV modulation with a magnetic field. We measure a white noise level of 2 μΦ0/Hz1∕2. The field noise of the magnetometer is 4 pT/Hz1∕2 at 4.2 K.