Inverse Hysteresis and Ultrasmall Hysteresis Thin-Film Transistors Fabricated Using Sputtered Dielectrics

Large current hysteresis is observed in carbon nanotube (CNT) transistors and usually shows as a positive threshold voltage shift when the gate sweeping direction changes from positive to negative. This paper reports fabrication of inverse hysteresis CNT thin-film transistors (TFTs) using magnetron sputtered oxide as a dielectric. Stacking of the sputtered dielectric with dielectrics deposited by other methods, such as atomic layer deposition, can effectively reduce or even eliminate the hysteresis. This can be explained as a combination of the effects of surface and interface trapped charges. Additionally, this hysteresis reduction method is widely compatible with various CNT-TFT structures and types and is even suitable for MoS2 TFTs. The output characteristics and frequency responses of large and small hysteresis devices are compared and show that the small-hysteresis inverter has lower distortion, and that its maximum operating frequency is nearly five times larger than that of TFTs with normal hysteresis.