Fabrication, electrical characterization and mechanical flexibility test of back gated carbon nanotube thin film transistors on polyimide substrate

Abstract

This work demonstrates the scalable method of fabricating back gated carbon nanotube thin film transistors (CNTTFTs) on a polyimide (kapton) substrate using photo lithography and lift-off process for patterning gate dielectrics and metals deposited for electrodes , and dip coating method for single walled carbon nanotubes deposition on functionalized dielectric surface. The CNTTFTs of varying dimensions are fabricated and electrical characterizations are done at room temperature and the CNTTFTs have exhibited p-type behaviour. The CNTTFT of channel length(L) 3 μm, width(W) 10 μm exhibits on-off current ratio of 9.219 × 105, carrier mobility of 4.9 cm2 V−1 s−1, trans conductance of 26 μS and on current of 472 μA when the substrate is kept flat (not bent). The mechanical flexibility test of CNTTFTs is done by conducting electrical characterization of CNTTFTs with the substrate bent to different diameters. Irrespective of the channel length, CNTTFTs have exhibited minimal change in the electrical characteristics when bent to 14 mm diameter. However, short channel CNTTFT (L = 3 μm) has shown considerable change in electrical characteristics when bent to 8 mm diameter compared to long channel length CNTTFT (L = 75 μm). The fabricated back gated flexible CNTTFTs work as CNTTFTs when bent up to the diameter of 8 mm, demonstrates that the CNTTFTs can be used for practical applications in the area of flexible electronics.