One-dimensional van der Waals Heterostructures: Growth Mechanism and Handedness Correlation Revealed by Non-destructive TEM

TL;DR

This study uses non-destructive TEM to reveal detailed structural and growth mechanisms of 1D van der Waals heterostructures, highlighting the correlation between nanotube handedness and growth conditions.

Contribution

It provides new insights into the formation, structural details, and handedness correlation of 1D van der Waals heterostructures using a transfer-free TEM approach.

Findings

Distinct edge structures linked to chiral angles and polarity.

Surface cleanliness crucial for high-quality heterostructure formation.

Handedness of nanotubes correlates with the template structure.

Abstract

In this work, we perform a follow-up and comprehensive study on the structural details and formation mechanism of chemical vapor deposition (CVD) synthesized one-dimensional (1D) van der Waals heterostructures. Edge structures, nucleation sites, crystal epitaxial relationships are clearly revealed using transmission electron microscopy (TEM). This is achieved by the direct synthesis of heteronanotubes on a CVD-compatible Si/SiO2 TEM grid, which enabled a transfer-free and non-destructive access to many intrinsic structural details. In particular, we have distinguished different shaped boron nitride nanotube (BNNT) edges, which are confirmed, by electron diffraction at the same location, to be strictly associated with its own chiral angle and polarity. We also demonstrate the importance of surface cleanness and isolation for the formation of perfect 1D heterostructures. Furthermore, we elucidate the handedness correlation between SWCNT template and BNNT crystals. This work not only provides an in-depth understanding of this new 1D heterostructure material group, but also, in a more general perspective, serves as an interesting investigation on crystal growth on highly curved (radius of a couple of nm) atomic substrates.