Regensburg 2010 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 9: SC: Poster Session
TT 9.53: Poster
Montag, 22. März 2010, 14:00–18:00, Poster A
Supercurrents through carbon nanotubes with Nb contacts — •Thomas Geiger — Institute for Experimental and Applied Physics, University of Regensburg
Based on previous work in our group, proximity induced supercurrents through a MWCNT of length 1.3 µm and diameter about 15 nm was measured. The sample was connected in 3-point geometry using a Pd/Nb 2.5/45 nm bilayer as direct contact material. Since Nb is the strongest elementary superconductor, it promises advantages over other materials like Al. Contact separation was about 300 nm, exceeding the typical scattering length in the tube. An elaborate on-chip RC-environment consisting of high-Ohmic leads and large bonding pads made of AuPd was used to ensure good electrical filtering in direct vicinity of the structure. In addition to thorough electrical filtering of the measurement lines this enabled us to perform sensitive measurements of the critical current.
The sample was covered with 50 nm Al2O3 and a local 2.6 µm wide and 55 nm thick Pd-topgate directly above the nanotube. This gate showed very effective and reliable operation. Despite the coverage of the nanotube, supercurrent was still detectable.
We found a peculiar subgap structure in the dI/dV- and IV-characteristics and investigated its temperature and gate voltage dependence.