Fabrication of carbon nanotube & graphitic nanomaterial thin films and their applications as opto-electronic platforms

Abstract

In this study, the fabrication method of single-walled carbon nanotube (SWNT) films and graphene films is demonstrated by the vacuum filtration process. SWNT or graphene films are hybridized with gold nanoparticles or polyelectrolytes to improve their electrical properties. Characterization such as optical absorption, electrical conductivity, electroabsorption, and morphology is carried out for the basis of opto-electronic device technology. A new technique to enhance the electrical conductivity of transparent SWNT films with a negligible loss of their optical transmittance is achieved. Hybridization of the SWNT films with gold nanoparticles increased the electrical conductivity two-fold to a maximum of 2.0 × $10^5$ S/m, while maintaining the transmittance of the initial value. The same trends are shown for other SWNT films with various initial conductivities and transparency levels. Functional changes in the gold nanoparticle-coated SWNT films suggest that the electrical conductivity change is due to an electron depletion mechanism as a result of a doping effect. As the electro-optical property of SWNTs, large electro-absorption susceptibilities in the ultraviolet region for SWNTs supported on quartz are demonstrated, that are approximately $10^3$ larger than the highest values reported to date for any system. The oscillatory behavior is described using a convolution of Airy functions in photon energy ascribing the effect to Franz-Keldysh oscillations. The metallic and semiconducting SWNT composition is varied, and it is shown that the confinement energy correlates with the average band gap for semiconducting SWNT in the film. The large susceptibilities arise from a sub-percolated network of metallic SWNT that enhances the local electric field. Next, a method for the layer-by-layer (LbL) fabrication of graphene thin films and gold nanoparticles is described by simple processes. The process involves reduction of gold ions on graphene sheets without the n...