Polymer-wrapped carbon nanotubes for high performance field effect transistors

This thesis focuses on fabrication and optimization of SWNT field effect transistors, aiming to improve performance and develop highly scalable and reproducible fabrication technique. The outline of the thesis is given below. In Chapter 2 we introduce Blade Coating deposition technique for SWNT alignment and discuss performance comparison of FETs based on SWNTs selected with poly-9,9-di-n-dodecyl-fluorenyl-2,7-diyl (PF12) and poly(3-dodecylthiophene-2,5-diyl) (P3DDT) polymers. Chapter 3 shows a study of the carrier transport mechanism in ambipolar FETs of semialigned networks of polymer-wrapped carbon nanotubes. The ambipolar characteristics persist with much improved on/off ratio values (106) when the FET is cooled down to liquid N2 temperature. We observe that the mobility values of both holes and electrons decrease by cooling, but with some anomalies as a slight increase below 150 K. Chapter 4 demonstrates short-channel ambipolar single-SWNT transistors prepared from a polymer-wrapped s-SWNT solution obtained with poly(2,5-dimethylidynenitrilo-3,4-didodecylthienylene) (PAMDD) polymer. By performing electrical characterization of the prepared field effect transistors we estimated the purity of semiconducting SWNT solution to be higher than 99.9%. Chapter 5 is devoted to the fabrication of carbon nanotube field effect transistors by chemical self-assembly of semiconducting single-walled carbon nanotubes on pre-patterned substrates. We functionalized the polymer with side chains containing thiols, to obtain chemical self-assembly of the selected s-SWNTs on gold electrodes. SWNTs devices based on individual tubes show an unprecedented (100%) yield for working devices. The SWNTs assembled by mean of the thiol groups are stably anchored to the substrate and are resistant to external perturbation as sonication in organic solvents.