Electrical Characteristics of CNT-FETs with Symmetric Field-Effect-Free-on Source and Drain

The carbon-nanotube field-effect-transistors (CNTFETs) have been explored and proposed to be the promising candidates for the next generation integrated-circuit (IC) devices. The so-called Schottky barrier (SB)-FET is widely used to characterize the operation behavior of a CNTFET, and the Schottky barriers are affected by the gate fields at the metal-nanotube interfaces. By using the double-layered catalyst configuration (nickel and upper SiO2layer), SWNTs were in-situ grown across two catalytic pads on a substrate with a thinner thermal oxide layer above the channel and thicker ones at the two source/drain junction terminals. The uni-polar characteristics of a p-type CNTFET was consequently achieved by electrostatic engineering. The turn-off current (Ioff) was significantly reduced and the turn-on current (Ion) to Ioffratio was then increased up to ∼ 104. The p to n conversion was observed after several cycles of measurement in a vacuum environment presumably due to removal of adsorbed O2molecules. On the other hand, the hysteresis behavior of transfer characteristics was still observed, suggesting that the CNTFET could be used in non-volatile memory applications.