Carbon nanotubes synthesized by plasma enhanced CVD: Preparation for measurements of their electrical properties

Carbon nanotubes (CNTs) were synthesized in atmospheric pressure microwave plasma torch in the mixture of argon, methane and hydrogen on the silicon substrate with SiO2 overlayer and a thin top iron film serving as a catalyst. This deposition technique is unique because of its simplicity and high CNT growth rate but it is still under investigation as concerns exits around its reproducibility. CNTs were deposited with the future prospect of their applications or further characterization that might require CNTs in the form of suspension or powder. One of the research directions includes measurements of CNT electrical properties such as their current-voltage (I–V) characteristics. Preparation of solutions with well dispersed CNTs was studied using various liquids (distilled water, ethyl alcohol) and ultrasonication. Dried drops of these solutions were investigated by scanning electron microscopy (SEM) and atomic force microscopy (AFM) in order to assess CNT appearance and dispersion. Electrical measurement chips with gold electrodes were prepared by electron lithography. CNTs were placed on the chips by dropping their solution and the I–V characteristics may be measured by contacting the electrodes bridged by CNTs.