Solution-Based Deposition Of Single-Walled Carbon Nanotube Thin Films For High Performance Thin-Film Transistors

Owing to their outstanding chemical,mechanical and electrical properties,single walled carbon nanotubes(SWNT)are promising and favorable contender for a diverse range of applications including high strength hybrid nano-composites,growth platforms for neuronal circuits,highly chemical/biological sensors,electrode material for solar cells and channel of active elements in electronic devices.SWNT and thin film transistors(TFTs)have been a potential candidate for the future electrical and photonic applications,including integrated circuits,control circuits,liquid crystal display and flexible and transparent display.This research field has attracted much attention and intensive efforts.The uniformity,density and morphology of the deposited SWNT thin films has remarkable impact on the device performance.It is significant to improve the performance and uniformity of the fabricated thin film field effect transistors(FETs)for the upcoming integration of logic circuits.In this dissertation,we presented an understanding on fabrication of large-scale and high-performance thin film FET arrays with notably improved reproducibility.In addition,the electrical transport characteristics of the SWNT field effect transistor arrays have been investigated.Solution-based deposition method has been used to deposit high-quality semiconducting SWNT thin films on the Si/Si O₂substrate.The experimental parameters for the solution-based deposition of SWNT thin films have been carefully improved by which thin films with different nanotube densities have been achieved.The relationship between sheet resistance and nanotube density of the deposited thin films has also been studied.The results indicate the inverse relation of sheet resistance and density of deposited SWNT thin films.By obtaining the foremost value of density and sheet resistance,the deposition parameter for the SWNT thin film has been optimized.Semiconducting SWNT thin films with different densities were further employed as a conductive channel to fabricate large-scale thin film FET arrays by the standard photolithography technique.The effects of nanotube density on the transfer and output characteristics of the thin film FETs have been comparatively studied,and the uniform and reproducibility of the device performance have been substantially evaluated by measuring a large amount of the fabricated FETs.The results suggest that the SWNT thin films with a moderate nanotube density can be used to fabricate large-scale thin film FET arrays with high device performance and good reproducibility.By fitting the experimental data,it is found that on-state current device close to the?A level,the switching ratio is maintained at>10⁴,the field effect mobility of about 15.6 cm²V^-1s^-1.