Solution-Based Fabrication and Characterization of a Logic Gate Inverter Using Random Carbon Nanotube Networks

Semiconducting carbon nanotubes (CNTs) are considered as one of the most promising candidates to replace silicon in future nano-electronics. Single-walled carbon nanotubes (SWNTs) have been used as an active channel material in field-effect transistors (FETs). The nanotube-based circuits show great potential in future electronics and computer technology. Integrating SWNT FETs to form logic gates-the basic units of integrated circuits (ICs)-needs both p- and n-type SWNT FETs. However, without doping, annealing, or other special treatment, the as-obtained SWNT FETs are typically p-type. Here we report a SWNT-based logic device-a logic gate inverter (or a NOT gate)-using simple fabrication methods. The critical components of the inverter including a p-type SWNT FET and an n-type SWNT FET are fabricated using low-cost materials and an easy-to-control solution-based process. The introduction of polyethylenimine (PEI), a polymer with high electron-donating ability, to the device successfully converts the p-type FET to an n-type device. The resulting devices are air-stable outside a vacuum or an inert environment. Electrical characterization of these devices demonstrates that both p-type and n-type FETs produce typical field effects and the resulting logic gate inverter exhibits satisfactory switching characteristics. We believe that the combination of the simple fabrication methods, easy conversion of the transistors, and satisfactory logic gate switching performance can influence fundamental research in nano-materials and practical applications of nano-electronics.