Fabrication and properties of arrays of superconducting nanowires
- PDF / 283,363 Bytes
- 7 Pages / 612 x 792 pts (letter) Page_size
- 104 Downloads / 231 Views
MATERIALS RESEARCH
Welcome
Comments
Help
Fabrication and properties of arrays of superconducting nanowires S. Dubois Unit´e PCPM, 1 Place Croix du Sud, B-1348 Louvain la Neuve, Belgium
A. Michel and J. P. Eymery Laboratoire de M´etallurgie Physique, UMR 6630, Bd 3-T´el´eport 2-BP 179, 86960 Futuroscope Cedex, France
J. L. Duvail and L. Piraux Unit´e PCPM, 1 Place Croix du Sud, B-1348 Louvain la Neuve, Belgium (Received 20 March 1998; accepted 30 June 1998)
We report on the fabrication and structural characterization of arrays of superconducting nanowires by electroplating lead into the nanopores of track-etched polymer membranes. The diameters of the lead nanowires range from 400 down to 70 nm, whereas their length is about 20 mm. Large enhancement of the critical field has been observed in good agreement with the Ginsburg–Landau–Silin theory. By comparing the predicted critical field enhancement for thin cylinders with experimental results, we have extracted the effective penetration depth. The dependence of the effective penetration depth and electron mean free path on the wire diameter is also discussed.
I. INTRODUCTION
Currently, there is considerable interest in the fabrication of materials with dimensions in the nanoscale range. Nanophysics methods such as molecular beam epitaxy followed by nanolithography of ever increasing resolution are usually considered to represent the ultimate limit for producing nanoscale materials. However, such nanoscale materials can also be fabricated using a different method, whose key ingredients are template and electrodeposition. In this method, thin fibrils of the desired materials are electrochemically synthesized within the voids of the template material. Most studies were performed using nuclear track-etched polymer films or anodic porous alumina as templates. Both nanoporous systems enable making a very thin cylinders of uniform dimensions with controlled diameter as small as a few tens of nanometer. As a result, nanowires with aspect ratios (length over diameter) as large as 103 can be obtained. Arrays of metal nanowires exhibit very interesting properties, such as 1D quantum phenomena in the electron transport,1 giant magnetoresistance in magnetic multilayered nanowires,2 highly anisotropic magnetic properties,3 etc. In contrast, the use of the template method to produce arrays of superconducting nanowires was not reported till now. For a nanoscale superconductor with L of the order of le (where le is the effective penetration depth and L is a characteristic sample dimension), it is predicted that the critical field (hc ) is larger than the bulk value (Hc ) by a factor of order (leyL). Such enhancement of the critical field in small samples simply results from the reduced free energy density of the superconducting state due to a more significant effect J. Mater. Res., Vol. 14, No. 3, Mar 1999
http://journals.cambridge.org
Downloaded: 03 Apr 2015
of the field penetration in small specimens. For a long thin cylinder in a longitudinal field, the approximation o
Data Loading...
