An important feature of ultra-clean single-walled carbon nanotube channels is that a small gate voltage can tune them from n-type (electron-doped) to p-type (hole-doped) devices. It is then possible to create a quantum transistors with drastically different characteristics under electron or hole doping. The problem is the intrinsic transport properties of these nanotubes are mostly symmetric and to have a functional device it is necessary to create an e-h transport asymmetry.
Resolving this problem would allow to create nanotube transistors with a giant e – h transport asymmetry. That will lead to applications in the physics of near molecular size nanoelectromechanical systems, to shrink down qubits devices and to create carbon nanotube THz detectors or gate programmable transistors.
In a recent paper, a research team from Montréal reported having solved this electron-hole transport asymmetry challenge. They created a 10 to 100 nm scale suspended nanotube transistors with a large e-h transport. The experimental devices consist of naked nanotube channels contacted with sections of the tube under annealed gold. The annealed gold acts as an n-doping top gate, allowing coherent quantum transport, and can create nanometre-sharp barriers.
“The most exciting implications are for building quantum circuits with single devices that can either store or pass quantum information along with the flick of a switch. […] Our study also shows that we can build devices with dual capabilities, which could be useful in building smaller electronics and packing things in more tightly. In addition, these ultra-short nanotube transistors could be used as tools to study the interplay between electronics, magnetism, mechanics and optics, at the quantum level.”
A.C. McRae, Department of Physics, Montréal, Canada