Top-down fabrication of small carbon nanotubes

Abstract

The control of diameter and chirality of carbon nanotubes (CNTs) has long been extremely challenging and critical for various CNT applications. Here, we report a top-down method that allows for reliable control of the diameter of individual few-walled carbon nanotubes (CNTs), thereby producing nanotubes with a desired diameter, including the smallest ones. This method involves the use of electron irradiation assisted by concurrent thermal annealing, which enables carbon removal from a CNT in a rather organized fashion, leading the nanotube to shrink uniformly and flawlessly. The smallest nanotubes can be routinely obtained by this self-contracting process of any few-walled nanotubes (1–4 shells) to reach their diameter limits, that is, 4.1 Å for single-walled CNTs (likely indexed as (5, 0) or (3, 3)), and 1.01, 1.66 and 2.41 nm for 2–4 walled CNTs, respectively (with their innermost tubes of ∼3.2 Å presumably indexed as (4, 0)). A new scenario based solely on the climb movements of 5|7 dislocations is proposed to well explain the observed nanotube shrinking processes, which are associated with the motions of atomic-scale kinks in different pathways. Due to the unique ability to dictate the exact CNT diameter, this facile method may open up a new avenue toward the ultimate strategy for bulk production of monosized and even chirality-specific small CNTs.