Direct-Write X-ray Nanopatterning: A Proof of Concept Josephson Device on Bi₂Sr₂CaCu₂O_8+δ Superconducting Oxide

Abstract

We describe the first use of a novel photoresist-free X-ray nanopatterning technique to fabricate an electronic device. We have produced a proof-of-concept device consisting of a few Josephson junctions by irradiating microcrystals of the Bi2Sr2CaCu2O8+δ (Bi-2212) superconducting oxide with a 17.6 keV synchrotron nanobeam. Fully functional devices have been obtained by locally turning the material into a nonsuperconducting state by means of hard X-ray exposure. Nano-XRD patterns reveal that the crystallinity is substantially preserved in the irradiated areas that there is no evidence of macroscopic crystal disruption. Indications are that O ions have been removed from the crystals, which could make this technique interesting also for other oxide materials. Direct-write X-ray nanopatterning represents a promising fabrication method exploiting material/material rather than vacuum/material interfaces, with the potential for nanometric resolution, improved mechanical stability, enhanced depth of patterning, and absence of chemical contamination with respect to traditional lithographic techniques.

Spectroscopic Indications of Tunnel Barrier Charging as the Switching Mechanism in Memristive Devices

“…Both vacuum as well as X‐ray beam exposure result in an increase of the device current and in a shrinking of the hysteresis. This can be attributed to a loss of oxygen at the YSZ surface in vacuum which is significantly promoted by the presence of an X‐ray beam as reported in the literature for a variety of oxide systems . In our samples, the loss of oxygen will likely result in a reduction of the YSZ tunnel barrier height and thereby to an increase of the device current which might be more pronounced for the HRS, thereby resulting a shrunk hysteresis.…”

Maskless X-Ray Writing of Electrical Devices on a Superconducting Oxide with Nanometer Resolution and Online Process Monitoring

“…This observation is in agreement with a local oxygen depletion process, which is expected to induce an elongation of the c -axis and therefore an expansion along the direction normal to the substrate. Previous nano-XRD measurements highlighted that in this process the local crystallinity of the Bi-2212 is substantially preserved and the only side effect is the possible formation of a layer of polycrystalline α-Bi 2 O 3 on the crystal surface in the irradiated areas 23 .…”

“…4a). Moreover, a possible additional effect could be an increase of the mosaic structure inside the crystal 23 .…”

“…However, the observation that focused hard X-rays are able to modify the crystal oxygen content 14 paved the way to the practical realization of a direct-write hard X-ray patterning method where only oxide/oxide interfaces are present, suggesting that a high enough X-ray dose could locally induce in the material an oxygen depletion large enough to drive it in a non-superconducting state. This idea has been recently demonstrated by fabricating a proof-of-concept IJJ device with this novel photoresist-free approach by means of synchrotron radiation, but, in spite of the nanometric sizes of the probe, only micrometric features have been obtained for the devices 23 .…”

Monte Carlo analysis of the oxygen knock-on effects induced by synchrotron x-ray radiation in the Bi2Sr2CaCu2Torsello1, Mino2, Bonino3 et al. 2018Phys. Rev. MaterialsSelf Cite130110View full textAdd to dashboardCite

“…However, interesting effects that in principle could be useful to modify materials in a controlled way, have been reported in the past [18], including for instance redox reactions [19], metal-insulator [20] and structural phase transitions [21]. Also in the case of HTSCs the irradiation with synchrotron hard X-rays has been reported to modify the normal and the superconducting properties of the target material [22,23], and this fact has recently been exploited to produce functioning electronic devices out of Bi-2212 single crystals by means of a novel nanopatterning technique [24,25]. However, the precise microscopic mechanism linking intense X-ray irradiation to the macroscopically observed properties modifications has not been clarified yet.…”