Environmental Stability of High T<sub>c</sub> Superconducting Ceramics

Barkatt, Aaron; Hojaji, H.; Amarakoon, Vasantha R. W.; Fagan, John

doi:10.1557/s0883769400038021

Cited by 36 publications

(14 citation statements)

References 83 publications

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“…Only the coverage of the surface with an orthogonal network of particles has increased substantially. This is an indication that the particles are related to chemical reactions with the ambient: Barium is well known to form BaCO 3 and Ba(OH) 2 at YBCO surfaces [13][14][15][16] and might therefore be responsible for the formation of the observed particles.…”

Section: Surface Analysis By Scanning Probe Microscopymentioning

confidence: 94%

YBa 2 Cu 3 O 7-δ single crystals revisited: Scanning probe data on very pure samples grown in BaZrO 3 crucibles

Hubler¹,

Jess²,

Lang³

et al. 1998

Applied Physics A: Materials Science & Processing

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We have studied very pure YBa 2 Cu 3 O 7−δ (YBCO) single crystals grown in BaZrO 3 crucibles by scanning and friction force microscopy (SFM, FFM) as well as by scanning tunneling microscopy (STM) and angle resolved X-ray photo-electron spectroscopy (ARXPS). By STM and SFM, clean stepped terraces are observed on as-grown crystals. Friction contrast, however, implies the presence of different materials, presumably traces of flux. After oxidation of the YBCO crystals, particles of 10 to 100 nm in size appear on the surface. Their number per unit area increases with time when the crystal is stored in air. Complementary information on such aged YBCO surfaces is provided by ARXPS. These data reveal 3 nm of mainly BaCO 3 and CuO on top of the YBCO matrix and suggest a very slow aging rate of the crystals, which is 20 times slower than for epitaxial thin films. The superconducting energy gap has been determined on fresh crystals by scanning tunneling spectroscopy (STS) at 4.6 K as 2∆ ≈ 30 meV. By spatially resolved tunneling spectroscopy the vortex lattice in a magnetic field of 4 T has been imaged. The inter-vortex distance amounts to 20 ± 2 nm.Scanning probe methods and angle resolved X-ray photoelectron spectroscopy (ARXPS) are well established tools for studying the surface properties of high-temperature superconductors [1][2][3][4]. Each of these methods probes specific qualities and depths of a material, allowing the reconstruction of a three-dimensionally resolved interface. Scanning tunneling microscopy (STM) and scanning force microscopy (SFM) not only allow investigations of the surface morphology on a nanometer to micrometer scale, but also provide material contrast by use of friction force microscopy (FFM). This yields valuable information on the purity of such surfaces. Complementary data on their chemical composition and aging process is provided by ARXPS. Furthermore, scanning tunneling spectroscopy (STS) probes the electronic density of states (DOS) near the Fermi level and allows the determination of the superconducting energy gap from current vs. voltage (I(V )) characteristics [5].Until recently, traces of residual flux on YBa 2 Cu 3 O 7−δ (YBCO) surfaces (mainly BaCuO 2 and CuO serving as flux solvents) as well as impurities originating from crucible materials (e.g. Al 2 O 3 , Au, MgO) constituted a major problem for crystal growers. Poor surface quality presents a problem especially when a surface-sensitive technique, such as STM or STS, is applied to probe electronic properties in the superconducting state. The short coherence length in YBCO, which is only of the order of a few Å in the [001] direction, means measurements are strongly affected even by thin contamination layers.These problems seem to have been overcome by using BaZrO 3 as the crucible material [6][7][8]. This material shows a sharp and non-reactive interface with the flux used in the YBCO growth process. Furthermore, Zr is unlikely to be incorporated into YBCO by substitution reactions, since its ion size does not fit in the structur...

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Section: Surface Analysis By Scanning Probe Microscopymentioning

confidence: 94%

YBa 2 Cu 3 O 7-δ single crystals revisited: Scanning probe data on very pure samples grown in BaZrO 3 crucibles

Hubler¹,

Jess²,

Lang³

et al. 1998

Applied Physics A: Materials Science & Processing

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“…In both cases, on the other hand, YBCO thin films, particularly the sensitive elements of the devices, such as Josephson junctions, are exposed to high temperatures caused by the deposition system and to chemicals used in the patterning process [7]. Since a YBCO thin film is very sensitive to the temperature in terms of the oxygen content [8] and to some extent a humid environment caused by the lithographic process [9], these additional steps can likely cause significant degradation in the superconducting properties of the final device [10]. Moreover, in the case of the dry etching of the metal layer (i.e., an ion beam etch), the device is exposed to energetic ions that also cause overheating [11].…”

Section: Introductionmentioning

confidence: 99%

Performance Analysis of Direct Gold Wire Bonding on Superconducting <inline-formula><tex-math notation="LaTeX">$\mbox{YBa}_{2}\mbox{Cu}_{3}\mbox{O}_{7\mbox{-}x}$</tex-math></inline-formula> Thin Films and Devices

Avci

Kuran

Uzun

2015

IEEE Trans. Appl. Supercond.

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The performance analysis of direct gold (Au) wire bonding on YBa 2 Cu 3 O 7-x (YBCO) thin films was performed. In a number of applications, YBCO thin films and devices are wire bonded on chip carriers or printed circuit boards for further electronic connections via the metallization of the contact pads of YBCO thin films. Although metallization for contact wiring is generally performed by thermal evaporation or sputtering at room temperature, the surface of a film is generally exposed to high temperatures by evaporated material or sputtering plasma. Moreover, an additional lithographic process (i.e., the application of a photoresist, baking, developing, and dry or wet etching) is necessary after the metal layer deposition in order to define contact pads. Since the superconducting properties of YBCO thin films and Josephson junctions are very sensitive to temperature and a humid environment, the metallization and additional lithographic processes during the fabrication cause significant degradation in the performance of the devices. In order to eliminate these additional steps, we performed a direct wire bonding process on YBCO thin films. Films of various thicknesses were deposited onto (100) SrTiO 3 (STO) substrates by direct-current magnetron sputtering, and 20-μm-wide meander-type microbridges were patterned. The contact pads of the devices were wire bonded onto chip carriers by a thermosonic wedge bonder without using any metallization layer. The reliability and performance analyses of the bonds were performed under several aggressive thermal cycling conditions from liquid nitrogen (LN, 77 K) up to 450 K. The superconducting properties of the samples were then analyzed by means of resistance-temperature (R-T ) and current-voltage (I-V ) measurements. A resistance model was developed for the bonding layout, and a specific contact resistivity was derived as ∼3 × 10 −6 Ω · cm 2 .

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“…7,8 When they are in contact with water, the constituent alkaline earth cation gradually dissolves and the pH of the solution is increased. [8][9][10][11][12][13][14][15] Mass equation of Y-123 in water is 16,17 YBa 2 Cu 3 O 7 + 1.5 H 2 O → 2.5 CuO + 1.5 Ba 2+ + 3 OH − + 0.5 Y 2 BaCuO 5 + 0.25 O 2 .…”

Section: Introductionmentioning

confidence: 99%

“…12,18,19 Although Y-123 is greatly degraded by water and humid air, 9,20 this effect should not preclude its practical application since it is possible to protect Y-123 by coating of silver or glass. [21][22][23][24][25] Although most of the literature reports are focusing on the reaction of high-T c superconductors with water or vapor qualitatively, 11,16,17 we have investigated the reaction of Bi-2223 with water kinetically. 14,15 It is found that the rate law is first order dependent on the surface area of the powder sample, and the reaction rate is greatly reduced at high pH.…”

Section: Introductionmentioning

confidence: 99%

Kinetic Study on the Reaction of YBa₂Cu₃O_y Powder with Water

Lin

Wang

et al. 2003

Int. J. Mod. Phys. B

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The reaction of superconducting YBa 2 Cu 3 Oy powder with water is studied kinetically. The initial rate law is found aso is the initial surface area of the solid, a and b is found to be 0.94 ± 0.02 and 0.318 ± 0.002, respectively. For 100.7 mg powder with a mean radius of 0.0265 mm at pH 7.00 and 298 K, Ro is 2.21 × 10 −4 mol · min −1 . Using a = 1 and b = 0.3, the rate constant, k, obtained at 283, 298 and 313 K is 0.64, 1.84 and 4.91 × 10 −3 mol · min −1 · cm −2 · M −0.3 , respectively. The activation energy is 50.0 kJ · mol −1 and pre-exponential factor is 1.09 × 10 6 mol · min −1 · cm −2 · M −0.3 , as calculated from the Arrhenius equation.

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Environmental Stability of High T_c Superconducting Ceramics

Cited by 36 publications

References 83 publications

YBa 2 Cu 3 O 7-δ single crystals revisited: Scanning probe data on very pure samples grown in BaZrO 3 crucibles

YBa 2 Cu 3 O 7-δ single crystals revisited: Scanning probe data on very pure samples grown in BaZrO 3 crucibles

Performance Analysis of Direct Gold Wire Bonding on Superconducting <inline-formula><tex-math notation="LaTeX">$\mbox{YBa}_{2}\mbox{Cu}_{3}\mbox{O}_{7\mbox{-}x}$</tex-math></inline-formula> Thin Films and Devices

Kinetic Study on the Reaction of YBa₂Cu₃O_y Powder with Water

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Environmental Stability of High Tc Superconducting Ceramics

Cited by 36 publications

References 83 publications

YBa 2 Cu 3 O 7-δ single crystals revisited: Scanning probe data on very pure samples grown in BaZrO 3 crucibles

YBa 2 Cu 3 O 7-δ single crystals revisited: Scanning probe data on very pure samples grown in BaZrO 3 crucibles

Performance Analysis of Direct Gold Wire Bonding on Superconducting <inline-formula><tex-math notation="LaTeX">$\mbox{YBa}_{2}\mbox{Cu}_{3}\mbox{O}_{7\mbox{-}x}$</tex-math></inline-formula> Thin Films and Devices

Kinetic Study on the Reaction of YBa2Cu3Oy Powder with Water

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Product

Resources

About

Environmental Stability of High T_c Superconducting Ceramics

Kinetic Study on the Reaction of YBa₂Cu₃O_y Powder with Water