Robust porous silicon substrates were employed for generating interconnected networks of superconducting ultrathin Nb nanowires. Scanning electron microscopy analysis was performed to investigate the morphology of the samples, which constitute of polycrystalline single wires with grain size of about 10 nm. The samples exhibit nonzero resistance over a broad temperature range below the critical temperature, fingerprint of phase slippage processes. The transport data are satisfactory reproduced by models describing both thermal and quantum fluctuations of the superconducting order parameter in thin homogeneous superconducting wires

Porous silicon, obtained by electrochemical etching, has been used as a substrate for the growth of nanoperforated Nb thin films. The films, deposited by UHV magnetron sputtering on the porous Si substrates, inherited their structure made of holes of 5 or 10 nm diameter and of 10 to 40 nm spacing, which provide an artificial pinning structure. The superconducting properties were investigated by transport measurements performed in the presence of magnetic field for different film thickness and substrates with different interpore spacing. Perpendicular upper critical fields measurements present peculiar features such as a change in the H c2⊥ (T ) curvature and oscillations in the field dependence of the superconducting resistive transition width at H ≈ 1 Tesla. This field value is much higher than typical matching fields in perforated superconductors, as a consequence of the small interpore distance.

We report on the transport properties of an array of N ∼ 30 interconnected Nb nanowires, grown by sputtering on robust porous Si substrates. The analyzed system exhibits a broad resistive transition in zero magnetic field, H, and highly nonlinear V (I) characteristics as a function of H which can be both consistently described by quantum tunneling of phase slips.

Abstract. -Resistive transitions have been measured on a perforated Nb thin film with a lattice of holes with the period of the order of ten nanometers. Bumps in the dR/dH versus H curves have been observed at the first matching field and its fractional values, 1/4, 1/9 and 1/16. This effect has been related to different vortex lattice configurations made available by the underlying lattice of holes.

Articles you may be interested inPerpendicular applied magnetic field dependence of Josephson current and measurement of trapped magnetic flux in Nb superconducting thin film by vibrating sample magnetometer Nb thin films containing a regular square array of antidots with 17 nm diameter and 50 nm spacing have been fabricated using a relatively simple lithographic process. The critical current density j c ͑H͒ curves, obtained here by electric transport measurements, exhibit commensurability effects with pronounced maxima just above the expected 0 H 1 = 0.830 T and 0 H 1/2 = 0.415 T matching fields, down to temperatures as low as 2.3 K. The behavior of j c ͑H͒ as well as the position of the maxima are consistent with the ones calculated in the framework of the time dependent Ginzburg-Landau model.