Fabricating one-dimensional van der Waals heterostructures on chirality-sorted single-walled carbon nanotubes

We previously demonstrated the experimental synthesis of one-dimensional van der Waals (1D vdW) heterostructures, where single-crystal boron nitride nanotubes (BNNT) and/or molybdenum disulfide nanotubes seamlessly wrap around a single-walled carbon nanotube (SWCNT) and form a coaxial hetero-nanotube with a diameter of only several nm. However, in that work, the inner-most templates are SWCNTs with mixed diameters and band structures, so the electronic property of the heterostructure is not controllable. In this work, we demonstrate the possibility of building 1D vdW heterostructures on atomically precise, single-chirality SWCNTs. This is achieved by a long route of dispersing, sorting, re-depositing and cleaning SWCNTs before performing the synthesis of 1D heterostructures. We employ five different single-chirality SWCNTs and confirm that 1D heterostructures can be fabricated on these solution-sorted SWCNT templates if the surfactant can be readily removed. The obtained heterostructures show a very minor variation in inner diameters, suggesting the high uniformity of the starting SWCNT template. Solution processes are found to have minor side effects and the defects are largely healed after the high temperature BNNT growth. As a result, the obtained heterostructures show a high crystal quality according to the spectroscopic and microscopic characterizations. Finally, we perform a structural analysis using (6, 5) SWCNT based 1D heterostructures as the example. Electron diffraction reveals an abundance of 80% of (6, 5) SWCNTs in the starting material, which allowed us to conveniently observe different types of BNNTs on SWCNTs of the identical chirality. We visualize that all zigzag, near-armchair, and chiral BNNTs can form on (6, 5) SWCNTs. As the property of a 1D heterostructure is largely affected by the inner-most template, being able to use atomically precise SWCNT as the starting material is an initial but critical step towards the fabrication of more function-designable 1D hetero-nanotube devices.