On the Kondo effect in carbon nanotubes at half halfing

In a single state of a quantum dot the Kondo effect arises due to the spin-degeneracy, which is present if the dot is occupied with one electron (N = 1). The eigenstates of a carbon nanotube quantum dot possess an additional orbital degeneracy leading to a four-fold shell pattern. This additional degeneracy increases the possibility for the Kondo effect to appear. We revisit the Kondo problem in metallic carbon nanotubes by linear and non-linear transport measurement in this regime, in which the four-fold pattern is present. We have analyzed the ground state of CNTs, which were grown by chemical vapor deposition, at filling N = 1, N = 2, and N = 3. Of particular interest is the half-filled shell, i.e. N = 2. In this case, the ground state is either a paired electron state or a state for which the singlet and triplet states are effectively degenerate, allowing in the latter case for the appearance of the Kondo effect. We deduce numbers for the effective missmatch d of the levels from perfect degeneracy and the exchange energy J. While d ~ 0.1 - 0.2 (in units of level spacing) is in agreement with previous work, the exchange term is found to be surprisingly small: J < 0.02. In addition we report on the observation of gaps, which in one case is seen at N = 3 and in another is present over an extended sequence of levels.Comment: full paper including figures at: http://www.unibas.ch/phys-meso/Research/Papers/2004/Kondo-4shell-SWNT.pd

Suitability of carbon nanotubes grown by chemical vapor deposition for electrical devices

Using carbon nanotubes (CNTs) produced by chemical vapor deposition, we have explored different strategies for the preparation of carbon nanotube devices suited for electrical and mechanical measurements. Though the target device is a single small diameter CNT, there is compelling evidence for bundling, both for CNTs grown over structured slits and on rigid supports. Whereas the bundling is substantial in the former case, individual single-wall CNTs (SWNTs) can be found in the latter. Our evidence stems from mechanical and electrical measurements on contacted tubes. Furthermore, we report on the fabrication of low-ohmic contacts to SWNTs. We compare Au, Ti and Pd contacts and find that Pd yields the best results.Comment: pdf including figures, see: http://www.unibas.ch/phys-meso/Research/Papers/2004/Suitability-CVD-tubes.pd

Workshop on Investment Vehicles and Financial Instruments supporting Technology Transfer and Innovation: Focus on the Danube Region and the Western Balkans countries

The objectives of the workshop were to identify existing financial instruments to support innovation and technology transfer activities in the Danube Region and the Western Balkan countries, to explore where the evident gaps exist and discuss ways to address currently unmet demand with synergistic solutions. The workshop aimed to strengthen and cement an emerging community of practice on these issues that should help to maximise impact on regional innovation. The workshop stimulated exchange and discussion on the nature, features and the general suitability of existing financial instruments for the financing of different innovation and tech transfer projects (including start-up creation, joint ventures, licensing transactions etc.). The final results are a definition of the type of financing instruments necessary for the region (in the form of vouchers, financial products, enhancements of features of existing innovation funds etc.) and a plan to accelerate their creation.JRC.I.4-Intellectual Property and Technology Transfe