Fully Gravure-Printed D Flip-Flop on Plastic Foils Using Single-Walled Carbon-Nanotube-Based TFTs

Since D flip-flop is one of the indispensable building blocks in integrated circuit (IC) design, providing a successful way to print D flip-flop on plastic foils will be the first step to reach fully printed flexible IC. Here, the network structure of single-walled carbon nanotubes (SWNTs) as an active layer has been employed to print the driver and load thin-film transistors (TFTs) of the D flip-flop. The same physical dimensions of driver and load TFTs were first developed to fully gravure print the D flip-flop because of the advantage of tunable electrical properties of network density of SWNTs. Therefore, the circuit design and printing becomes simpler and more convenient than using general design rules. Furthermore, the SWNT network structure in the active layer can also minimize the fluctuation of threshold voltages (V_th) of SWNT-TFTs because of the use of the same physical dimensions in TFTs. The resulting gravure-printed D flip-flop shows a clock-to-output delay of 23 ms for 20-Hz clock signal. This is the first reported D flip-flop performance using all gravure-printing method yet achieved.