Ultra-thin YBa₂Cu₃O_7−xfilms with high critical current density

Abstract

The temperature and field dependence of harmonics in voltage V n = V n − iV n using the screening technique have been measured for YBa 2 Cu 3 O 7−δ superconducting thin films. Using the Sun model we obtained the curves for the temperature-dependent critical current density J c (T). In addition, we applied the criterion proposed by Acosta et al. to compute J c (T). Also, we made used of the empirical law J c ∝ (1 − T /T c) n as an input in our calculations to reproduce experimental harmonic generation up to the fifth harmonic. We found that most models fit well the fundamental voltage but higher harmonics are poorly reproduced. Such behavior suggests the idea that higher harmonics contain information concerning complex processes like flux creep or thermally assisted flux flow.

Experimental evidence for hotspot and phase-slip mechanisms of voltage switching in ultrathin YBa2Cu3O7–x

“…The amorphous YBCO is not superconducting, but serves as a protective layer for the ultra-thin superconducting YBCO film during the lithography process. The room-temperature resistivity of the amorphous YBCO layer is 700  cm, which is six orders of magnitude higher than the resistivity of the superconducting YBCO film and therefore has a negligible influence on the electrical measurements that are discussed below [22]. Further details about the ultra-thin YBCO films used in this work are reported elsewhere [22].…”

“…The room-temperature resistivity of the amorphous YBCO layer is 700  cm, which is six orders of magnitude higher than the resistivity of the superconducting YBCO film and therefore has a negligible influence on the electrical measurements that are discussed below [22]. Further details about the ultra-thin YBCO films used in this work are reported elsewhere [22]. After film deposition, 100-nm-thick Au contact pads were fabricated ex situ using roomtemperature dc magnetron sputtering with a shadow mask.…”

“…Here, we realize ultra-thin YBa2Cu3O7-x (YBCO) films with high critical current densities and smooth surfaces [22] and use focused ion beam (FIB) milling to fabricate YBCO nanowires from them with widths down to 30 nm. We observe voltage switching in current-biased YBCO nanowires and show that it originates from two different mechanisms: hotspot-assisted suppression of the edge barrier and the appearance of phase-slip lines.…”

THz Mixing with High-TC Hot Electron Bolometers: A Performance Modeling Assessment for Y-Ba-Cu-O Devices

“…Besides, the very large T DSB values reported in Reference [13] were attributed to inadequate experimental conditions by the authors, who predicted an improvement of T DSB < 10 4 K up to 6 THz (system noise temperature), a figure compatible with our predicted T DSB = 5 × 10 3 K (mixer noise temperature, not optimized [27]) at 2.5 THz. Our present optimized predictions (solid curve in Figure 16) have therefore to be taken as a limit that could be reached with improved nano-structuring of c-axis oriented YBCO ultrathin films [54,55]. ultrathin films [20,53], due to increased operation temperature (T C = 39 K) and expected instantaneous bandwidth up to 10 GHz.…”

Photoresponse of a La1.85Sr0.15CuO4nanostrip

“…There have been several reports towards the realization of SSPDs using YBa 2 Cu 3 O 7- films with T c about 90 K [11][12][13][14][15]. However, as the thickness decreases to 5 nm, the quality of the films strongly deteriorates [14]. Arpaia superconducting characteristics.…”