Transistors based on carbon nanotube random networks

Single-wall carbon nanotube (SWCNT) networks have been potentially envisioned as one of promising semiconducting materials for transistors in logic circuit applications. The advantage of using SWCNT random networks as field-efect transistors (FET) is the ease of fabrication, which practically makes cost-efective solution processable and printable electronics feasible. It is challenging to fabricate SWCNT FET on a large scale with reasonably high mobility and full yield of semiconductor devices owing to the co-existence of metallic (M) and semiconducting (S) tubes in its networks or films. This chapter will introduce several major approaches, including specific synthesis of S-SWCNTs, selective elimination or destruction of M-SWCNTs, and photolithography-assisted stripping to intentionally improve the semiconducting characteristics from its networks. Meanwhile, tremendous eforts have been devotedto sort out M- and S-SWCNTs for preparing S-SWCNT richink for solution-based fabrication, including surfactant wrapping, aromatic extraction, amine reaction, selective oxidation, dielectrophoresis, bundled tubes removal, DNA or polymer wrapping, density gradient ultracentrifugation (DGU) and gel-based separation techniques. In addition, methods such as selective modification of SWCNTs with diazonium reagents or organic free radicals are adopted to successfully demonstrate full semiconductor device yield and reasonably high carrier mobility. Fundamental issues which limit the performance of SWCNT networks are also discussed.