YBCO Nanobridges: Simplified Fabrication< newline/> Process by Using a Ti Hard Mask (original) (raw)
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YBa2Cu3O7 nanobridges fabricated by direct-write electron beam lithography
Applied Physics Letters, 1992
A direct method for nondamaging, nanometer-scale patterning of high T, superconductor thin films is presented. We have fabricated superconducting nanobridges in high-quality, epitaxial thin-film YBa$&O, (YBCO) by combining direct-write electron beam lithography and an improved aqueous etchant. Weak links with both length and width dimensions less than 20 nm have exhibited critical currents at 77 K of 4-20 ,uA and 13, products of 10-100 PV which compare favorably with results for other YBCO junction technologies. We have used this technique in the fabrication of a shock-wave pulse former as an initial demonstration of its applicability to monolithic superconductive electronics.
Electrical and magnetic properties of Si ion implanted YBa2Cu3O7−δ thin films and microbridges
Thin Solid Films, 2004
Fabrication of superconducting bilayer YBa 2 Cu 3 O 7 À d (YBCO) thin film structure by Si ion implantation and properties of microbridge patterned on that are presented. YBCO thin film of 150 nm thickness was grown on single crystal (100) SrTiO 3 substrate by inverted cylindrical magnetron sputtering. The sample was implanted with 100 keV, 1 Â 10 16 Si ions/cm 2 . Upon implantation with Si, the sample lost its electrical conductivity and diamagnetism while its crystalline structure was preserved after the annealing of the sample. The implanted ions do not alter the overall crystal structure of high temperature superconductor film. This allows the growth of epitaxial superconducting second layer YBCO film on top of the implanted area without using any buffer layer, thus providing an effective method of fabricating multilayer structures. The second layer film and the microbridge patterned by laser writing technique, showed the superconducting properties similar to those of pure YBCO base layer with a reduced critical current density. D
Matching in YBCO nanobridges due to surface barrier effects
Physica C: Superconductivity, 2004
The critical current density j c of YBa 2 Cu 3 O 7Àd (YBCO) nanobridges (width %200 nm) is measured as a function of the magnetic flux density B, applied perpendicular to the YBCO-film plane. The resulting j c-vs-B characteristics, when analyzed in detail, exhibit a periodic modulation, which can be attributed to an enhanced stability of specific flux-line configurations. Such an increased stability is found for magnetic fields leading to a vortex lattice being commensurable with the width of the bridge and, thus, with the surface barriers at its edges. The magnitude of this new type of matching with perpendicular field orientation appears to be significantly smaller than what has been found in previously reported cases of parallel fields.
YBa sub 2 Cu sub 3 O sub 7 nanobridges fabricated by direct-write electron beam lithography
Appl Phys Lett, 1992
A direct method for nondamaging, nanometer-scale patterning of high T, superconductor thin films is presented. We have fabricated superconducting nanobridges in high-quality, epitaxial thin-film YBa$&O, (YBCO) by combining direct-write electron beam lithography and an improved aqueous etchant. Weak links with both length and width dimensions less than 20 nm have exhibited critical currents at 77 K of 4-20 ,uA and 13, products of 10-100 PV which compare favorably with results for other YBCO junction technologies. We have used this technique in the fabrication of a shock-wave pulse former as an initial demonstration of its applicability to monolithic superconductive electronics.
YBa2Cu3O7−x films with Ba2Y(Nb,Ta)O6 nanoinclusions for high-field applications
Superconductor Science and Technology, 2020
Structural and transport properties of YBa 2 Cu 3 O 7-x films grown by pulsed laser deposition with mixed 2.5 mol.% Ba 2 YTaO 6 (BYTO) and 2.5 mol.% Ba 2 YNbO 6 (BYNO) double-perovskite secondary phases are investigated in an extended film growth rate, R = 0.02-1.8 nm/s. The effect of R on the film microstructure analyzed by TEM techniques shows an evolution from sparse and straight to denser, thinner and splayed continuous columns, with mixed BYNO+BYTO (BYNTO) composition, as R increases from 0.02 nm/s to 1.2 nm/s. This microstructure results in very efficient flux pinning at 77 K leading to a remarkable improvement of the J c behaviour, with the maximum of the pinning force density F p (Max) = 13.5 GN/m 3 and the irreversibility field in excess of 11 T. In this range, the magnetic field values at which the F p , is maximized varies from 1 T to 5 T being related to the BYNTO columnar density. The film deposited with R = 0.3 nm/s exhibits the best performances over the whole temperature and magnetic field ranges achieving F p (Max) = 900 GN/m 3 at 10 K and 12 T. At higher rates, R > 1.2 nm/s, BYNTO columns show a meandering nature and are prone to form short nanorods. In addition, in the YBCO film matrix a more disordered structure with a high density of short stacking faults is observed. From the analysis of the F p (H, T) curves it emerges that in films deposited at the high R limit, the vortex pinning is no longer dominated by BYNTO columnar defects, but by a new mechanism showing the typical temperature scaling law. Even though this microstructure produces a limited improvement at 77 K, it exhibits a strong J c improvement at lower temperature with F p = 700 GN/m 3 at 10 K, 12 T and 900 GN/m 3 at 4.2 K, 18 T.
Physica C: Superconductivity, 1996
Tilt grain-boundary junctions with a 45 ° [001] misorientation were formed in YBa2Cu30 7 x (YBCO) thin films grown by pulsed organometallic beam epitaxy on (100) MgO substrates. The junctions were introduced at predetermined locations due to a modification of the orientation relation between the thin film and substrate following a low-energy argon ion irradiation of specific areas of the substrate surface prior to film deposition. Rutherford backscatter spectrometry and certain surface features observed by atomic force microscopy indicate that implantation of ions is necessary to cause the modified epitaxy. The low-temperature transport characteristics of individual isolated grain boundaries were determined by electromagnetic characterizations of the junction behavior. The same grain boundaries were examined by transmission electron microscopy and high-resolution electron microscopy and it was found that the boundaries are for the most part free of precipitates and well structured at the atomic scale. Regardless of the average grain boundary inclination, asymmetric (110)(100) facets dominate the microstructure of the junctions. Possible mechanisms for epitaxy modification and the transport properties in relation to the observed microstructure are discussed.
Study of in-plane electrical transport anisotropy of a -axis oriented YBa2Cu3O7−δ nanodevices
Physical Review B
In the present work, we report the growth of fully untwinned high-quality a-axis-oriented YBa 2 Cu 3 O 7−δ films on (100) SrLaGaO 4 substrates by using PrBa 2 Cu 3 O 7−δ as a buffer layer. We also fabricated nanowires at different angles γ with respect to the [0,1,0] direction of the substrate and studied the in-plane anisotropy of the critical current density, which we explained by considering the anisotropy in the coherence length ξ and London penetration depth λ L. Finally, half-integer Shapiro-like steps measured in slightly underdoped c-axis oriented (γ = 90 •) nanowires point towards a different transport regime, which could shed light on intriguing issues of high-critical-temperature superconductors.
Growth and BZO-doping of the nanostructured YBCO thin films on buffered metal substrates
Physica C-superconductivity and Its Applications, 2010
The growth of the nanostructured YBa 2 Cu 3 O 6+x (YBCO) films is investigated for the first time on biaxially textured NiW substrates used in coated conductor technology. The optimization process of superconducting layers is made in wide magnetic field and temperature range in order to understand the vortex pinning structure and mechanism in our films prepared from nanostructured material. Structural analysis shows that growth mechanism in YBCO films grown on NiW is completely different when compared to YBCO on STO. Films on NiW are much rougher, there is huge in-plane variation of YBCO crystals and moreover out-of-plane long range lattice ordering is greatly reduced. Magnetic measurements demonstrate that j c in films grown on NiW is higher in high magnetic fields and low temperatures. This effect is connected to the amount of pinning centres observed in films on metal substrates which are effective at low temperature range.
Thin Solid Films, 2007
YBa 2 Cu 3 O 7 − δ (YBCO) thin films, possessing high critical current density (J c ), have been synthesized by embedding a homogeneous array of Y 2 O 3 non-superconducting nanoclusters/nanoparticles using a pulsed laser deposition technique. The size, interparticle spacing, and density of Y 2 O 3 nanoparticles in YBCO thin films were tailored by varying the number of laser pulses in order to determine the optimum size for effective immobilization of vortices. Scanning transmission electron microscopy with atomic number contrast and X-ray diffraction techniques were used to determine the size and structure of the nanoparticles. Both techniques indicate that the Y 2 O 3 particles are epitaxial with respect to the surrounding YBCO matrix. The information about pinning of vortices by the nanoparticles was obtained by investigating the behavior of critical current density as a function of temperature and applied field, which in turn determines the vortex density in the sample. The superconducting transition temperature (T c ) of YBCO films with the inclusion of nanoparticles was observed to remain almost the same or decrease marginally (1-2 K) with respect to T c of pure YBCO films deposited under identical conditions. However, J c s of YBCO films embedded with self-assembled nanoparticles were found to be significantly higher than that of pure YBCO films. The J c enhancement was up to five times in high magnetic field, which is a key requirement for practical application of high-T c materials.