Study On Solution-processed Fabrication Of Single-walled Carbon Nanotube Thin Films And Their Iodine Doping

Single-walled carbon nanotube thin films?SWNT-TFs?have attracted significant attention for potential applications in large-area thin-film devices,due to their excellent electronic properties,good transparency and flexibility.Large scale fabrication of high quality and high purity semiconducting SWNT-TFs plays the key role toward practical applications in various fields.Solution-processed technology has been widely used to fabricate SWNT-TFs by efficiently depositing SWNTs on functionalized substrates.Although the large-area SWNT-TFs can be successfully fabricated,further investigation is still needed to improve and control the quality of the thin films.In this thesis,we used the semiconducting SWNT solution with a high purity of 99 % and fabricated SWNT-TFs by using solution-processed method on functionalized Si/SiO₂ substrates.The effect of substrate functionalization,deposition time and deposition temperature on the density,morphology and sheet resistance of fabricated SWNT-TFs was further studied.The experimental results revealed that the Si/SiO₂ substrates functionalized by poly-L-lysine?PLL?and aminopropyl-triethoxysilane?APTES?possessed good affinities with semiconducting SWNTs and the deposited thin films were quite uniform.Moreover,PLL@ Si/SiO₂ substrate showed better affinity with semiconducting SWNTs than that of APTES@Si/SiO₂ substrate,and tended to form more nanotube bundles.With increasing the deposition time or deposition temperature,the density of SWNT-TFs gradually increased,and thus the corresponding sheet resistance showed a decrease.When the depositing temperature was kept constant,the density of the fabricated SWNT-TFs steadily increased as the depositing time was extended.When the depositing time was kept unchanged,however,the density of the SWNT-TFs did not show obvious change under relatively low temperature;while the depositing temperature rose over 60 ?,uniformly distributed SWNT-TFs can be deposited in a short time.The fabricated high-purity semiconducting SWNT-TFs were further doped by iodine through the gaseous phase method,which was characterized by Raman spectroscopy.The experimental results revealed that,after a careful washing process the doped SWNT-TFs were quite clean.After iodine doping,the peak position and lineshape of the G band of the SWNT-TFs did not show obvious change,while its intensity remarkably decreased.In the low-frequency region of the Raman spectrum,a new peak at 168 cm^-1 and its higher harmonics at 343 cm^-1 was detected,which can be assigned to the-polyiodide chain structures,indicating that the iodine successfully filled into the internal of SWNTs.