Gate Capacitance Coupling of Double-Gate Carbon Nanotube\nNetwork Transistors

Abstract

Carbon nanotube (CNT) network channels\nconstructed using a high-purity CNT solution for use in CNT thin-film\ntransistors have the advantages of the possibility of requiring a\nlow-temperature process and needing no special equipment. However,\nthere are empty spaces between individual CNTs, resulting in unexpected\neffects. In this study, double-gate (DG) CNT network transistors were\nfabricated and measured in four different configurations to observe\nthe capacitive coupling effects between the top gate (TG) and bottom\ngate (BG) in the DG structure. As a result, the electrical characteristics\nmeasured with the BG with a thicker gate oxide while floating the\nTG were similar to those measured with the TG with a thinner gate\noxide. A comparison of the measured transfer curves showed that TG\nand BG were strongly coupled through the empty spaces in the channels.\nIn addition, we evaluated the capacitance coupling effect due to changes\nin the CNT density, which is closely related to the empty space of\nthe network channel. Finally, we proposed a method to determine the\neffective gate capacitance by considering the empty spaces between\nCNTs, which enabled the accurate evaluation of mobility. The effects\nof these materials were demonstrated by fabricating transistors using\nAl₂O₃, HfO₂, and ZrO₂ as\nTG oxide materials. By focusing on considerations based on the properties\nof CNT materials, our study provides valuable insights into accurate\nelectrical modeling and potential advancements in CNT-based devices.