Ultralow Power Carbon Nanotube Logic Circuits

NU 2013-157

Inventors

Mark C. Hersam*

Michael L. Geier

Pradyumna L. Prabhumirashi

Kanan P. Putambekar

Hyungil Kim

Weichao Xu

Abstract

Complementary metal-oxide-semiconductor (CMOS) logic circuits are the basis for all modern digital electronics. Commercial electronics are dominated by silicon CMOS technology. Carbon nanotube logic circuits represent an alternative material with the additional benefits of mechanical flexibility and solution processability. The thin-film transistors presented here employ sorted semiconducting carbon nanotubes and local metal gate structures to tune the threshold voltages of both the p-type and n-type devices to enable ultralow power CMOS logic. Furthermore, the input and output voltages are suitable for logic gate cascading, thus making these circuits ideal for large-scale integrated circuits. The Northwestern researchers developed digital logic circuits using p-type and n-type carbon nanotube based transistors. Both p-type and n-type transistors have tuned threshold voltages that enable ultralow power operation. This alignment is accomplished by incorporating local metal gate structures and sorted semiconducting carbon nanotubes. The resulting thin-film transistors are then integrated into three basic logic circuits: inverters, NOR gates, and NAND gates. These circuits display ideal input and output voltage behavior while maintaining subnanowatt power consumption. Figure 1. SWCNT CMOS inverter including the unencapsulated p-type TFT and benzyl viologen doped n-type TFT Figure 2. SWCNT CMOS inverter circuit and voltage transfer curves

Applications

• Digital Electronics, encompassing a variety of integrated circuit applications, including:
• Microprocessors and memory
• Displays
• Large-area sensor arrays for environmental or biomedical sensing

Advantages

• High mechanical flexibility relative to conventional Si wafer-based electronics
• Low cost solution processing of active materials
• Not limited to wafer size; scalable to large area devices & applications
• Ultra-low power consumption
• Exceptional noise immunity
  

Publication
Geier M, Prabhumirashi P, McMorrow J, Xu W, Seo JW, Everaerts K, Kim C, Marks T and Hersam M (2013) Subnanowatt Carbon Nanotube Complementary Logic Enabled by Threshold Voltage Control. Nano Letters. 13: 4810-4814.

IP Status

A provisional patent application has been filed.