DNA functionalization of carbon nanotubes for ultrathin atomic layer deposition of high $ dielectrics for nanotube transistors with 60 mv/decade switching

For single-walled carbon nanotube (SWNT) field effect transistors, vertical scaling of high κ dielectrics by atomic layer deposition (ALD) currently stands at ∼8 nm with a 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 because nucleation of an oxide dielectric layer in the ALD process hinges upon covalent chemisorption on reactive groups on surfaces. Here, we show that by noncovalent functionalization of SWNTs with poly-T DNA molecules (dT40-DNA), one can impart functional groups of sufficient density and stability for uniform and conformal ALD of high κ dielectrics on SWNTs with thickness down to 2−3 nm. This enables approaching the ultimate vertical scaling limit of nanotube FETs and reliably achieving S ≈ 60 mV/decade at room temperature, and S ≈ 50 mV/decade in the 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.