Abstract
A new approach for improving electrical and thermal contacts between
multi-wall carbon nanotubes (MWCNTs) and metal electrodes by localized
laser heating is presented in this work. The nanotubes were suspended,
using the dielectrophoresis technique, over a gap of 1 mu m width and 5
mu m depth connecting the ends of the patterned electrodes.
Subsequently, the as deposited nanotubes were directly heated, in
ambient atmosphere, by a focused laser beam, which was also used for
exciting the Raman spectra of the nanotubes. The changes in the
vibrational frequencies were used to estimate the local temperature that
was controlled by the incident laser power density. The changes in the
nanotubes due to laser heating were evaluated by using scanning electron
microscopy, Raman spectroscopy and electrical measurements. The method
was employed for improving the electrical contacts between suspended
MWCNTs and different electrodes (W, Ti and Au). The reduction in the
electrical resistance was up to three orders of magnitude, resulting in
contact resistivity as low as similar to 0.1-1 k Omega.mu m(2), with the
lowest values being obtained for Au electrodes. The main advantage of
this method, when compared with traditional and rapid thermal annealing,
is that the thermal treatment is localized in a small region, thus
allowing the processing of circuits composed of different materials,
whereby each process can be individually controlled.
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