A low voltage operational single-walled carbon nanotube thin-film transistor containing a high capacitance gate dielectric layer produced by layer-by-layer deposition

This paper presents the characteristics of a low voltage driven thin-film transistor (TFT) containing an active layer coated with a single-walled carbon nanotube (SWCNT) network. To make the high capacitance gate dielectrics layers, poly(ethylene imine) and the titanium oxide precursor, titanium(IV) bis(ammonium lactate) dihydroxide, were coated by a layer-by-layer deposition method. Through this process we obtained a capacitance of 118 nF/cm2 and a total thickness of about 70 nm. The SWCNT active layer was deposited by spray-coating onto the layered-gate dielectric using a solution containing purified SWCNTs and a polystyrene additive. We used polystyrene in the coating solution to increase the dispersion of SWCNTs in the 1-methyl-2-pyrrolidone solution and decrease current leakage though the TFT channels. The resulting TFT showed a mobility of 6.7 cm2/V s, a threshold voltage of −0.88 V, and an on/off ratio of about 500 at operating voltages less than 2 V, which is suitable for the operation of various portable electronic devices. The output characteristics showed a good linear character and well-saturated behavior at elevated drain voltage.