Chirality engineering for carbon nanotube electronics

Carbon nanotubes (CNTs), tubular nanostructures consisting of rolled-up graphene, are promising materials for electronic devices at the nanometre and molecular regimes. Fundamentally, the electronic properties of CNTs and their junctions depend on global and local chiralities, as defined by quantum boundary conditions along the circumferential and longitudinal directions. As such, CNTs can behave as a metal, a semiconductor or a quantum dot in an electronic device. Much of the progress in CNT electronics, going from single resistors and transistors to complex functional logic and communication devices, thin films and flexible electronics, sensors and intelligent systems, has been achieved through control over the ‘global chirality’ of CNTs — the distribution of chiralities at the macroscale. In this Review, we summarize approaches to control global and local CNT chiralities by growth, separation and transformation strategies. We then discuss opportunities and challenges for chirality engineering towards surpassing the performance of conventional electronic devices, and development of unconventional CNT quantum electronics including coherent quantum transistors and quantum sensors. Chirality fundamentally determines the electrical properties of CNTs and is therefore critical for the performance of CNT electronics. This Review summarizes approaches in controlling the global chirality distribution and local chirality junctions and discusses the progress in CNT electronics.