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

Abstract

X-ray nanofabrication has so far been usually limited to mask methods involving photoresist impression and subsequent etching. Herein we show that an innovative maskless X-ray nanopatterning approach allows writing electrical devices with nanometer feature size. In particular we fabricated a Josephson device on a Bi2Sr2CaCu2O8+δ (Bi-2212) superconducting oxide micro-crystal by drawing two single lines of only 50 nm in width using a 17.4 keV synchrotron nano-beam. A precise control of the fabrication process was achieved by monitoring in situ the variations of the device electrical resistance during X-ray irradiation, thus finely tuning the irradiation time to drive the material into a non-superconducting state only in the irradiated regions, without significantly perturbing the crystal structure. Time-dependent finite element model simulations show that a possible microscopic origin of this effect can be related to the instantaneous temperature increase induced by the intense synchrotron picosecond X-ray pulses. These results prove that a conceptually new patterning method for oxide electrical devices, based on the local change of electrical properties, is actually possible with potential advantages in terms of heat dissipation, chemical contamination, miniaturization and high aspect ratio of the devices.

Materials characterization by synchrotron x-ray microprobes and nanoprobes

“…At lower energies [longer time delays, see Fig. 14(a)] temperature mapping, thermal ion motion, and eventual melting, spallation, or cracking effects can be simulated by a finite-element approach (Nicholson et al, 2001;Aldica et al, 2011;Pagliero et al, 2014;Mino, Bonino et al, 2017;Wallander and Wallentin, 2017).…”

“…Recently Pagliero et al (2014) showed that irradiation with a 117 × 116 nm 2 beam at 17 keV can affect both structural and electronic properties of Bi 2 Sr 2 CaCu 2 O 8þδ (Bi-2212) microcrystals, which have a typical T c ≈ 80-90 K. In this material the oxygen nonstoichiometry plays a key role since oxygen content is directly related to the structural and electronic properties, being able to tune the material T c and even to drive it into a nonsuperconducting state (Inomata et al, 2003;Cagliero et al, 2009;Mino, Bonino et al, 2017;. The study highlighted the fact that the nanobeam induces a progressive oxygen depletion in the microcrystals resulting in c-axis elongation and increase of electrical resistance.…”

“…More recently, the same group reported the fabrication of a Josephson device on a Bi-2212 microcrystal by drawing two single lines of only 50 nm width using a 17.4 keV synchrotron nanobeam (Mino, Bonino et al, 2017). A precise control of the fabrication process was achieved by monitoring in situ the variations of the device electrical resistance during x-ray irradiation [see Fig.…”

“…(b) Temporal evolution of the sample temperature calculated with the finite-element method at the point of maximum temperature considering the average continuous photon flux (black curve) and the pulsed nature of SR (red curve, dark gray). The initial temperature of the system was set to 300 K. Previously unpublished figure reporting data published inMino, Bonino et al (2017).…”

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 Cite120110View 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.…”