Vertical Alignment of Carbon Nanotubes Using the Magneto-Evaporation Method

Abstract

We developed a novel method of vertical alignment of SWNTs using a single-step process for the simultaneous vertical alignment of the SWNTs by a magnetic field and the fixation of their alignment by means of the direct evaporation of the films. We fabricated Fe-oxide/SWNT samples that are reacted by iron-oleate complex, oleic acid and cut SWNTs in 1-octadecene. The Fe-oxide/SWNT samples are dispersed in NN-dimethylformamide and the resulting solution was deposited on an ITO glass substrate using the spraying method with magnetic field. After evaporation of the SWNT solution in the presence of a magnetic field, we transferred the nanotubes to the vacuum-evaporator chamber, and titanium is evaporated by e-beam evaporation to hold the vertical alignment of the SWNTs. The resulting SWNTs exhibit the formation of a high degree of vertically aligned SNWTs over a large area. We showed that the degree of orientation of the SWNTs is strongly influenced by the field strength, film thickness of the evaporating molecules and evaporating rates. This technique takes significant advantages of the alignment of SWNTs with high aspect ratio at room temperature, without any organic binders and without the need for further alignment procedures. Moreover, this method might be applicable to other anisotropic materials with high aspect ratio.