Advanced Functional Materials, Vol.21, No.10, 1810-1815, 2011
Ultrathin SWNT Films with Tunable, Anisotropic Transport Properties
Directional transport properties at the nanoscale remain a challenge, primarily due to issues pertaining to control over the underlying anisotropy and scalability to macroscopic scales. Here, we develop a facile approach based on template-guided fluidic assembly of high mobility building blocks - single walled carbon nanotubes (SWNTs) - to fabricate ultrathin and anisotropic SWNTs films. A major advancement is the complete control over the anisotropy in the assembled nanostructure, realized by three-dimensional engineering of the dip-coated SWNTs ultrathin film into alternating hydrophilic and hydrophobic microline patterns with prescribed intra/inter-line widths and line thicknesses. Variations in the contact line profile results in an evaporation-controlled assembly mechanism that leads to alternating, and more importantly, contiguous SWNTs networks. Evidently, the nanoscopic thickness modulations are direct reflections of the substrate geometry and chemistry. The nanostructured film exhibits significant anisotropy in electrical and thermal transport properties as well as an optically transparent nature, as revealed by characterization studies. The direct interplay between the anisotropy and the 3D microline patterns of the substrate combined with the wafer-level scalability of the fluidic assembly allows us to tune the transport properties for a host of nanoelectronic applications.