Gate Capacitance Coupling of Double-Gate Carbon Nanotube Network Transistors

Area of Science:

• Materials Science
• Nanotechnology
• Electrical Engineering

Background:

• Carbon nanotube (CNT) network channels offer low-temperature processing for thin-film transistors.
• Unaccounted empty spaces between CNTs in network channels cause unexpected electrical effects.
• Capacitive coupling in double-gate (DG) structures is a critical factor in device performance.

Purpose of the Study:

• Investigate capacitive coupling effects between top gate (TG) and bottom gate (BG) in DG CNT network transistors.
• Analyze the influence of empty spaces and CNT density on capacitive coupling.
• Develop a method for accurate mobility evaluation by accounting for gate capacitance.

Main Methods:

• Fabrication of DG CNT network transistors in four configurations.
• Electrical characterization and measurement of transistor performance.
• Evaluation of capacitance coupling effects by varying CNT density and gate oxide materials (Al2O3, HfO2, ZrO2).

Main Results:

• Electrical characteristics measured with BG (thicker oxide, floating TG) mimicked those with TG (thinner oxide).
• Strong capacitive coupling between TG and BG was observed, attributed to inter-CNT empty spaces.
• A method was proposed to determine effective gate capacitance, enabling accurate mobility assessment.

Conclusions:

• Empty spaces in CNT networks significantly influence capacitive coupling in DG transistors.
• Accurate electrical modeling requires considering inter-CNT empty spaces and their impact on capacitance.
• The study provides insights for advancing CNT-based device design and performance evaluation.