Increased flux pinning in YBa ₂ Cu ₃ O _7−δ thin-film devices through embedding of Au nano crystals

Abstract

We prepared direct-current superconducting quantum interference device (dc-SQUID) gradiometers consisting of a single YBa2Cu3O 7−δ (YBCO) layer on SrTiO3 (STO) bicrystal substrates. The superconducting thin film was modified by embedding crystalline gold nanoparticles. We investigated the growth conditions of these particles as well as their influence on the properties of the YBCO thin film. In our magneto-optical measurements we found that the presence of embedded nano crystals results in a distinct enhancement of jc over the whole investigated temperature range. We attribute the higher critical current density to an increased pinning, which also results in a reduction of the flux noise of our investigated gradiometers.

Modifications of the Meissner screening profile in YBa2Cu3O7−δthin films by gold nanoparticles

“…With the Au seed layer thickness used the typical Au particle size is in the range 10 − 40 nm. 8 The area distribution of the Au nanoparticles is quite homogeneous, whereas the concentration within the depth profile varies, as later discussed.arXiv:1401.6295v1 [cond-mat.supr-con] …”

“…6 Recently, it has been demonstrated that Au nanoparticles, incorporated in YBCO thin films, lead to an increase of T c and the critical current density j c (from 4 · 10 7 A/cm 2 to 6 · 10 7 A/cm 2 at 10 K). 7,8 Since YBCO is superconducting above the boiling temperature of nitrogen this is of special interest for applications. A stronger flux pinning of the vortices at the Au nanoparticles causes a higher j c , which is crucial in order to improve superconducting magnetic field sensors 8,9 as used in dc-SQUID gradiometers.…”

Gold nanocrystals in high-temperature superconducting films: creation of pinning patterns of choice

“…If one cannot avoid vortex penetration into the superconductor in the first place [5], one can suppress vortex motion through pinning the flux lines at inherent or artificial pinning centres. Several efficient techniques are currently known to introduce such artificial pinning centres into thin films of optimally doped high-temperature superconducting YBa 2 Cu 3 O 7−δ (YBCO) [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20].…”

“…This means, for example, a thin film superconducting quantum interference device (SQUID) gradiometer structure can be manufactured where strong pinning in the antenna structures can be combined with grain boundary Josephson junctions with lower critical currents. The combination of both engineering steps would lead to a significant increase in the signal to noise ratio of the device [20].…”

Electron backscatter diffraction analysis of gold nanoparticles on Y1Ba2Cu3O7−δ

“…10 With a transmission electron microscopic (TEM) analysis, it has been shown that the orientation of the gold nanoparticles with their {111} planes is mostly parallel to the substrate surface. 11 A question still completely unanswered covers the role of the spatial distribution and crystallographic orientation of the crystalline nanoparticles play in this context. Procedures using electron backscatter diffraction (EBSD) provide both integral statements about the particle ensemble and local statements on the nanoparticles based on the available resolution.…”