Local Laser Annealing of Contacts Between MWCNTs and Metallic Electrodes
Keywords:nanodevices, electrical contact, local annealing, laser treatment
A new approach to improve the electrical and thermal contacts between multi-walled carbon nanotubes and metallic electrodes was developed by using spatially localized laser heating coupled with a micro Raman equipment. After the deposition by dielectrophoresis, the nanotubes were heated in ambient atmosphere by a focused laser beam in order to improve the electrical contacts of the nanostructures with different electrodes (W, Ti and Au) and also to excite the Raman signal of the nanotubes. The changes in the vibrational frequencies of the Raman bands of the nanotubes provides a real time feedback of the treatment conditions allowing to estimate the local temperature, which is used for adjusting the parameters of treatment. Laser treatment tests were performed in a single step (single exposition of the sample to laser) or gradually (successive expositions of the sample to laser, with gradual increase of the used laser power density) and better results were obtained for the gradual treatment tests. Laser treatment of contacts carried out after the calibration of the treatment parameters, showed a reduction of up to three orders of magnitude in the electrical resistance of the devices. 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.