DNA Functionalization of Carbon Nanotubes for Ultra-Thin Atomic Layer Deposition of High k Dielectrics for Nanotube Transistors with 60mV/decade Switching

TL;DR

This paper demonstrates that non-covalent DNA functionalization of carbon nanotubes enables ultra-thin high-k dielectric layers via atomic layer deposition, significantly improving the subthreshold swing of nanotube transistors.

Contribution

Introducing a non-covalent DNA functionalization method to achieve uniform ultra-thin high-k dielectric layers on carbon nanotubes for improved transistor performance.

Findings

Achieved dielectric thickness down to 2-3nm with uniform coverage.

Realized subthreshold swing of ~60mV/decade at room temperature.

Enhanced dielectric scaling approaching fundamental limits.

Abstract

For single-walled carbon nanotube (SWNT) field effect transistors, vertical scaling of high k dielectrics by atomic layer deposition (ALD) currently stands at ~8nm with subthreshold swing S~70-90 mV/decade at room temperature. ALD on as-grown pristine SWNTs is incapable of producing a uniform and conformal dielectric layer due to the lack of functional groups on nanotubes and that nucleation of an oxide dielectric layer in the ALD process hinges upon covalent chemisorption on reactive groups on surfaces. Here, we show that by non-covalent functionalization of SWNTs with ploy-T DNA molecules (dT40-DNA), one can impart functional groups of sufficient density and stability for uniform and conformal ALD of high k dielectrics on SWNTs with thickness down to 2-3nm. This enables approaching the ultimate vertical scaling limit of nanotube FETs and reliably achieving S ~ 60mV/decade at room temperature, and S~50mV/decade in band to band tunneling regime of ambipolar transport. We have also carried out microscopy investigations to understand ALD processes on SWNTs with and without DNA functionalization.