Josephson Junctions and SQUIDs Created by Focused Helium-Ion-Beam Irradiation of YBa2Cu3O7
B. Müller, M. Karrer, F. Limberger, M. Becker, B. Schröppel, C.J. Burkhardt, R. Kleiner, E. Goldobin, D. Koelle
DOI 10.1103/PhysRevApplied.11.044082 · Physical Review Applied
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Abstract
By scanning with a 30-keV focused He ion beam (He-FIB) across YBa2Cu3O7 (YBCO) thin-film microbridges, we create Josephson barriers with critical current density jc adjustable by irradiation dose D. The dependence jc(D) yields an exponential decay. At 4.2K, a transition from flux-flow to Josephson behavior occurs when jc decreases below approximately 2MA/cm2. The Josephson junctions exhibit current-voltage characteristics (IVCs) that are well described by the resistively and capacitively shunted junction model, without excess current for characteristic voltages Vc≲1mV. Devices on MgO and LSAT substrates show nonhysteretic IVCs, while devices on SrTiO3 show a small hysteresis. For all junctions, an approximate scaling Vc∝jc1/2 is found. He-FIB irradiation with a high dose produces barriers with jc=0 and high resistances of 10kΩ to 1GΩ. This provides the possibility to write highly resistive walls or areas into YBCO using a He-FIB. Transmission electron microscopy reveals an amorphous phase within the walls, whereas for lower doses the YBCO stays crystalline. We have also “drawn” superconducting quantum-interference devices (SQUIDs) by using a He-FIB for the definition of the SQUID hole and the junctions. The SQUIDs show high performance, with flux noise <500nΦ0/Hz1/2 in the thermal white-noise limit for a device with 19pH inductance.
Source-reported materials — not catalogue approval
| Formula | Reported Tc (K) | Pressure (GPa) | Type |
|---|---|---|---|
| YBa2Cu3O7 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 89 | Pressure not reported | onset |
| YBa2Cu3O7-δ Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 90 | Pressure not reported | unknown |
| La1.84Sr0.16CuO4 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | — | Pressure not reported | unknown |
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