Improvement of the electrical contact between carbon nanotubes and metallic electrodes by laser irradiation

In this work we used a new approach for electrical contact improvement between multi-wall carbon nanotubes and metallic electrodes by localized laser heating. The nanotubes were suspended, using the dielectrophoresis technique, over a gap of 1μm width and 5μm depth connecting the ends of the patterned electrodes. Subsequently, the as deposited nanotubes were directly heated, in ambient atmosphere, by a laser having a wavelength of 473nm. The Raman signal of the nanotubes, through its G band displacement, was used to determine the process temperature and this parameter was controlled by calibrating the incident power density. The changes in the nanotubes morphology were evaluated using scanning electron microscopy, Raman spectroscopy and electrical measurements. After calibration, this method was employed for improving the electrical contact between suspended multi-wall carbon nanotubes and different electrodes (W, Ti and Au). The reduction in the electrical resistance was between 80 - 99%, 80 - 95% and 10 - 90% for W, Ti and Au electrodes, respectively, resulting in contact resistivity as low as ~1 kΩμm².