# Electron-Beam Manipulation of Silicon Impurities in Single-Walled Carbon Nanotubes

## TL;DR

This study demonstrates the precise manipulation of silicon impurities in single-walled carbon nanotubes using focused electron beams, enabling atomic-level engineering for potential electronic device applications.

## Contribution

It introduces a method for controlled silicon atom manipulation in SWCNTs via electron irradiation, with detailed analysis of displacement mechanisms and energy thresholds.

## Key findings

- Over 90 controlled lattice jumps of silicon atoms were achieved.
- Displacement cross sections were estimated for the manipulation process.
- Molecular dynamics simulations revealed orientation-dependent energy thresholds.

## Abstract

The recent discovery that impurity atoms in crystals can be manipulated with focused electron irradiation has opened novel perspectives for top-down atomic engineering. These achievements have been enabled by advances in electron optics and microscope stability, but also in the preparation of suitable materials with impurity elements incorporated via ion and electron-beam irradiation or chemical means. Here it is shown that silicon heteroatoms introduced via plasma irradiation into the lattice of single-walled carbon nanotubes (SWCNTs) can be manipulated using a focused 55-60 keV electron probe aimed at neighboring carbon sites. Moving the silicon atom mainly along the longitudinal axis of large 2.7 nm diameter tubes, more than 90 controlled lattice jumps were recorded and the relevant displacement cross sections estimated. Molecular dynamics simulations show that even in 2 nm SWCNTs the threshold energies for out-of-plane dynamics are different than in graphene, and depend on the orientation of the silicon-carbon bond with respect to the electron beam as well as the local bonding of the displaced carbon atom and its neighbors. Atomic-level engineering of SWCNTs where the electron wave functions are more strictly confined than in two-dimensional materials may enable the fabrication of tunable electronic resonators and other devices.