Nano-patterning of cuprate superconductors by masked He+ ion irradiation: 3-dimensional profiles of the local critical temperature

Abstract

Irradiation of cuprate high-T c superconductors with light ions of moderate energy creates point defects that lead to a reduction or full suppression of the critical temperature. By shaping the ion flux with a stencil mask, nanostructures for emerging superconducting electronics can be fabricated. The 3-dimensional shape of such defect landscapes is examined, based on calculations of full collision cascades and atom displacements. A relation between the calculated defect density and experimental values of the critical temperature T c in thin YBa 2 Cu 3 O 7−δ films is etablished that allows to determine the distribution of local T c 's and its 3-dimensional visualization. The results confirm that, using 75 keV He + ion irradiation and a stencil mask, well-defined patterns of non-superconducting material in the superconducting matrix can be produced with low blurring.

Ultradense Tailored Vortex Pinning Arrays in Superconducting YBa2Cu3O7−δThin Films Created by Focused He Ion Beam Irradiation for Fluxonics Applications

“…The resulting three-dimensional shape of CDs with suppressed T c is inferred from simu-lations of ion-matter interaction and collision cascades with the program SRIM 32 and calibrated to experimental data of T c suppression as a function of defect density. 33 A defocused 30 keV He + beam of 20 nm FWHM diameter creates well-defined cylindrical channels with diameters ∼ 25 nm in a YBCO film within which T c is suppressed or reduced up to a depth of 80 nm, as evidenced in Fig. 1(c).…”

“…(d) Sketch of the pinning lattice with lattice spacing a: red disks represent irradiated spots, the blue dashed lines indicate the unit cell of the quasi-kagomé tiling, and gray crosses mark those sites that were removed from the hexagonal lattice to form the quasi-kagomé tiling. The aperture angle of the ion beam is ±0.07 • , hence the ion beam hits the sample surface almost orthogonally with a nearly Gaussian fluence profile 26 with a full-width half maximum (FWHM) of about 20 nm.The resulting three-dimensional shape of CDs with suppressed T c is inferred from simu-lations of ion-matter interaction and collision cascades with the program SRIM 32 and calibrated to experimental data of T c suppression as a function of defect density 33. A defocused 30 keV He + beam of 20 nm FWHM diameter creates well-defined cylindrical channels with diameters ∼ 25 nm in a YBCO film within which T c is suppressed or reduced up to a depth of 80 nm, as evidenced inFig.…”

Structural Changes in YBa2Cu3O7 Thin Films Modified with He+-Focused Ion Beam for High-Temperature Superconductive Nanoelectronics

“…36,37 At higher irradiation doses, YBCO becomes amorphous. 7,12,13,32,38,39 However, it remains to be seen whether the localized effects of a nanofocused beam (Figure 1b) yield the same structural modifications in YBCO.…”

“…Broad beam irradiation, involving an unfocused and uniform flux of high-energy ions (Figure a), appears to displace oxygen atoms from their crystallographic positions at O(1) (Figure a). − The removal of oxygen atoms from the O(1) sites, primarily but not exclusively to the vacant O(5) positions within the same Cu(1)–O(1) layers, induces a structural shift from the orthorhombic to tetragonal phase. This transition is characterized by the convergence of otherwise distinct lattice parameters a and b , alongside a monotonic increase in the lattice parameter c . , Notably, this structural phase transition can also be triggered by changing the oxygen concentration δ in YBa 2 Cu 3 O 7−δ , or varying the temperature. , At higher irradiation doses, YBCO becomes amorphous. ,,,,, However, it remains to be seen whether the localized effects of a nanofocused beam (Figure b) yield the same structural modifications in YBCO.…”

Влияние Радиационных Дефектов Различного Типа На Критический Ток Слоистого Анизотропного Сверхпроводника

“…В [18] исследовалось влияние облучения на скорость релаксации в сверхпроводнике CaFe 2 As 2 . Влияние облучения на величину критического тока исследовалось с начала 1990-х [19][20][21], но продолжает быть актуальным и в настоящее время [22][23][24]. В [19]…”