Direct fabrication of atomically defined pores in MXenes using feedback-driven STEM
Summary¶
Nanopores in two-dimensional materials are technologically interesting for ion transport, nanofiltration, and related membrane applications, but many fabrication routes rely on plasma etching or broad-beam irradiation with limited in situ control. This Small Methods article reports a feedback-driven aberration-corrected scanning transmission electron microscopy (STEM) workflow that combines sub-angstrom electron probes, real-time atomic imaging, and automated pore sculpting to study how Ti₃C₂Tₓ MXene transforms under electron-beam processing as a function of temperature. Complementing the microscope work, the authors introduce an Electron-Beam Simulator (E-BeamSim) to visualize atomic movements and interactions under irradiation, and they connect the experimental motivation to prior reactive force field studies of beam- and ion-induced defect evolution in graphene that established dose-, ion-size-, and ion-species-dependent trends in defect types and nanopore sizes. The MXene focus extends that mechanistic picture to a chemically complex, surface-terminated two-dimensional ceramic where oxygen-, fluorine-, and hydroxyl-bearing terminations and titanium sublattice mobility can couple to beam-induced disorder.
Methods¶
In situ STEM fabrication (experiment)¶
Aberration-corrected STEM with feedback/real-time imaging during nanopore sculpting in Ti\(_3\)C\(_2\)T\(_x\) (MXene).
Irradiation simulation (E-BeamSim)¶
E-BeamSim tracks displacements and edge restructuring under e-beam exposure.
Atomistic context (literature / cited ReaxFF MD)¶
Intro cites ReaxFF MD on ion-irradiated graphene (defect/nanopore statistics vs dose, ion species) as precedent for knock-on/vacancy behavior; MXene adds surface termination and T-dependent mobility (layerwise vs disordered removal)—full dose/energy in article/SI.
MD application (literature context; not new ReaxFF in this paper). This Small Methods report centers on STEM and E-BeamSim; prior graphene ion-irradiation ReaxFF molecular dynamics in the cited literature used LAMMPS-class engines with periodic supercells, NVT or NVE exposure segments, time step and duration tied to dose metrics, and Nosé–Hoover or Berendsen thermostats as in those sources—N/A to restate those ion-MD numbers on this page. This MXene work’s own simulation is E-BeamSim (not ReaxFF); N/A—NPT barostat; N/A—external DC electric field in the E-BeamSim description here; N/A—metadynamics. Temperature is a key experimental control for STEM processing.
Findings¶
At room temperature, electron-beam exposure induces random atomic displacements and titanium pile-up at nanopore edges; E-BeamSim reproduces this qualitative edge-disorder behavior. At elevated temperature, after surface-group removal and with increased atomic mobility, the system undergoes transformations consistent with more selective, layer-resolved atom removal, enabling more controlled pore growth relative to the room-temperature regime. The authors frame these observations as a route toward defect engineering not only in functionalized MXenes but more broadly in other two-dimensional layers where beam processing can be paired with temperature as a control knob.
Comparisons and sensitivity. E-BeamSim compares qualitatively to STEM at room vs elevated temperature; sensitivity to beam dose and energy is in the main text/SI. Corpus honesty: ReaxFF precedents are literature-level, not new fits in this article.
Limitations¶
Quantitative beam dose, energy, and full simulation parameter sets must be taken from the main text and Supporting Information rather than this wiki summary. E-BeamSim and cited ReaxFF precedents are complementary tools; direct one-to-one quantitative mapping from graphene ion irradiation to MXene electron-beam chemistry should be treated cautiously without article-specific validation.
Relevance to group¶
Couples ReaxFF-capable modeling (van Duin/Yilmaz) with in situ electron microscopy of 2D ceramics for nanopore fabrication.
Citations and evidence anchors¶
- DOI:
10.1002/smtd.202400203