Electron Transport in Very Clean, As-Grown Suspended Carbon Nanotubes

TL;DR

This paper demonstrates that fully suspended, defect-free single-walled carbon nanotubes exhibit clear quantum transport phenomena over wide energy ranges, enabling detailed study of their intrinsic electrical properties and band structures.

Contribution

It introduces a method to produce ultra-clean, suspended SWNTs with well-defined transport characteristics, revealing new quantum states and correlating contact resistance with transport regimes.

Findings

Observation of quantum states shell-filling, splitting, and crossing in magnetic fields.

Correlation between contact junction resistance and transport regimes.

Transport data used to probe nanotube band structures.

Abstract

Single walled carbon nanotubes (SWNT) have displayed a wealth of quantum transport phenomena thus far. Defect free, unperturbed SWNTs with wellbehaved or tunable metal contacts are important to probing the intrinsic electrical properties of nanotubes. Meeting these conditions experimentally is nontrivial due to numerous disorder and randomizing factors. Here we show that ~ 1 um long fully suspended SWNTs grown-in-place between metal contacts afford SWNT devices exhibiting well-defined characteristics over much wider energy ranges than nanotubes pinned on substrates. Various low temperature transport regimes in true-metallic, small and large bandgap semiconducting nanotubes are observed including quantum states shell-filling, -splitting and -crossing in magnetic fields for medium conductance devices. The clean transport data reveals a correlation between the contact junction resistance and the various transport regimes in SWNT devices. Further, we show that electrical transport data can be used to probe the band structures of nanotubes including nonlinear band dispersion.