Towards supersensitive bolometers and electron coolers based on Carbon nanotubes

Mikhael Tarasov, Johannes Svensson and Leonid Kuzmin

Carbon nanotubes (CNT) are being intensively developed for novel electronics. Electron cooling by superconductor-insulator-nanotube (SIN) tunnel junctions could be extremely effective due to the small volume of the CNT. A novel concept of a Cold-Electron Bolometer with a CNT as absorber should demonstrate record sensitivity due to the very low temperature that is predicted to be reached in the CNT (less than the phonon temperature).  Objectives of this work are to demonstrate effective electron cooling in superconducting nanostructures comprising a Carbon Nanotube; and to develop a supersensitive Cold-Electron Bolometer based on a cooled carbon nanotube as absorber.  This will be one of the first practical implementations of CNT in electronics.

The CNT is produced by chemical vapour deposition or plasma-enhanced chemical vapour deposition.  The latter will be used to produce high quality metallic MWNT of controlled length and diameter that can then be deposited between electrodes to form the basic structure of the electron cooler.  Additional electrodes are deposited on top of the nanotube using standard deep UV or e-beam lithography techniques.  The first method (chemical vapour deposition) will be used to grow aligned SWNT at well-defined positions on a chip.  This will enable “mass-scaled” production of many structures simultaneously.  This requires the refinement of the production methods and optimisation of the substrate materials and pattern geometry to obtain the most favourable conditions for the cooling application. This will be carried out in parallel with studies to attempt to control the electronic behaviour of the CVD grown SWNT (i.e. metallic or semi-conducting).

Students involved in this project will design and fabricate a layout and photomask compatible for both technologies.  The next step will be to obtain two or four tunnel contacts to CNT.  This should be arranged by the next lithography step and deposition of an Al thin film layer.  Fabricated nanotubes will demonstrate many interesting phenomena such as a single electron tunneling mechanism with a typical Coulomb blockade.  Such features will be measured at temperature about 300 mK in a closed-cycle cryofree He3 refrigerator. 

This work is supported by the Swedish Institute, INTAS and the SSF.

The results will be summarized in the form of a report and could be presented for publication.

Contact:
Leonid Kuzmin
<leonid.kuzmin -et- mc2.chalmers.se>