Evaluation of low resistance contacts on YBa₂Cu₃O₇thin films using the transmission line model

Abstract

In measurements of low contact resistances in planar geometries, the current density through the contact can be inhomogeneous. If this inhomogeneity is neglected. serious systematic errors can occur when calculating the specific contact resistivity. In this work, the transmission line model, commonly used in semiconductor technology, is applied to account for the inhomogeneous current density in low ohmic contacts between gold or silver and YBa,Cu,O, thin films. To evaluate the influence of preparation parameters, several fabrication techniques and different kinds of YBa,Cu,O, thin films have been used to form the metal-YBa,Cu,O, interface. Contact resistivities as low as 1 x lo-' R cm' have been obtained.

Fabricating Nanogaps inYBa2Cu3O7−δBaghdadi1, Arpaia2, Charpentier3 et al. 2015Phys. Rev. Applied211250View full textAdd to dashboardCite

“…From the low-bias conductance values, we can estimate an average value for the contact resistivity of the YBCO=Au interface, from the top and side contact, of approximately 4 × 10 −8 Ω cm 2 . This value is among the best reported in the literature [15,16,50], corroborating the potentiality of the nanogap for proximity hybrid devices, that we demonstrate in the next paragraph.…”

Soldered joints—an essential component of demountable high temperature superconducting fusion magnets

“…The width and length of each joint measured are given in the captions. All the In 52 Sn 48 joints in figure 11 show very straightforward, almost text-book, behaviour following equation (5.1)-the average values for the thickness of the solder layers was 22 μm with a standard deviation of 2 μm which are values consistent with the SEM and an interfacial resistivity that is temperature independent with values of 20-27 nΩ cm 2 -similar to those reported in the literature and attributed to the REBCO/Ag interface [49,50]. The average difference between equation (5.1) and the measured values of R J is 2.3% in the temperature range of 8 K-80 K, demonstrating excellent agreement.…”

YBCO/Ag boundary resistivity in YBCO tapes with metallic substrates

“…The measurements of the resistance R j of the overlapped joints with the different overlapping lengths were carried out on samples 3, 4, 5, and 6. The contact resistivity of the boundary YBCO/Ag was calculated as (neglecting the effect of the indium solder) R b = R j wL j (6) where L j is the length of the overlapping region of the adjoined [7], after annealing of already finished Ag contacts with contact resistivity of ∼10 −10 m 2 in flowing oxygen at a temperature of 250 • C, the contact resistivity dropped by two orders of magnitude. In our sample the copper foil was soldered to YBCO/Ag at a temperature of ∼220 • C, which might be high enough to cause a certain degree of diffusion between Ag and the YBCO layer and to improve the electrical contacts between them.…”