Case Snapshot

The Challenge

The team needed to identify Bernal and rhombohedral graphene polytypes in nanoscale cavities and observe how controlled mechanical loading changes their stacking state.

The Breakthrough

Park NX-Hivac enabled Conductive AFM current mapping under nitrogen, correlating local current contrast with graphene stacking and tracking force-driven switching events.

The Outcome

The team demonstrated reversible switching between Bernal and rhombohedral polytypes in cavities as small as 30 nm. Channel-connected cavities required less than 1 nN of lateral shear force and less than 1 fJ per switching event.

Why It Matters

The work shows how nanoscale cavity design and low-force AFM manipulation can control stacking states in graphitic materials, supporting research into reconfigurable multiferroic and slidetronic devices.

Switching Graphitic Polytypes in Elastically Coupled Cavities

Tel Aviv University used Park NX-Hivac to map current contrast and study force-driven switching between Bernal and rhombohedral graphene polytypes in elastically coupled nanoscale cavities.

  • Customer: Tel Aviv University, School of Physics and Astronomy, Israel
  • Research Focus: Reversible switching of graphitic polytypes in elastically coupled cavities
  • Solution: Park NX-Hivac for Conductive AFM current mapping and friction force measurement
  • Key Value: Local electrical readout and force-controlled switching of graphene stacking states under nitrogen

The Challenge

Graphitic polytypes differ only in the stacking order of graphene layers, yet this structural difference can strongly influence their electrical and multiferroic properties. Previous switching studies typically required micrometre-scale domains and micronewton loading forces, limiting the practical control of polytype states at the nanoscale.

The team needed a method that could identify Bernal and rhombohedral domains within nanoscale cavities, measure local current contrast under clean and controlled conditions, and observe how mechanical loading triggers switching between the two stacking states.

“To study graphitic polytype switching at the nanoscale, we needed to combine a reliable local electrical readout with controlled mechanical loading.”

— Prof. Moshe Ben Shalom, School of Physics and Astronomy, Tel Aviv University, Israel

The Solution

Park NX-Hivac provided Conductive AFM current mapping in a nitrogen atmosphere for the investigation of graphitic polytypes in cavity-patterned graphene structures. The team used the platform to correlate topography, local current contrast, and friction-force-dependent switching behavior.

  • Controlled-Environment C-AFM: Captured current maps under a nitrogen atmosphere to support reproducible measurements on clean graphene surfaces.
  • Nanoscale Current Mapping: Distinguished current contrast between rhombohedral and Bernal islands within cavity arrays.
  • Contact-Mode Surface Preparation: Used controlled contact-mode scans to remove residual contamination before current mapping.
  • Friction Force Measurement: Recorded lateral tip deflection during forward and backward scans to quantify the force associated with switching events.

The Results

Conductive AFM current maps resolved Bernal and rhombohedral graphene islands in cavities down to 30 nm in diameter. The assignment of the two stacking states was validated through Raman mapping, current measurements, and their relative thermodynamic stability. High-load scans triggered switching between the two polytypes, while subsequent low-load scans confirmed the resulting domain configuration.

By connecting cavities with narrow channels, the team engineered elastic coupling between neighboring islands and reduced the required lateral shear force to less than 1 nN. The corresponding switching energy was below 1 fJ per event. These measurements showed that cavity geometry can tune switching thresholds and the propagation of stacking boundaries.

“Conductive AFM with Park NX-Hivac enabled us to identify local current contrast between Bernal and rhombohedral islands and follow their switching under controlled loading.”

— Prof. Moshe Ben Shalom

Key Outcomes

  • Resolved Bernal and rhombohedral graphene polytypes in cavities down to 30 nm
  • Mapped local current contrast under a controlled nitrogen atmosphere
  • Measured polytype switching with less than 1 nN lateral shear force in channel-connected cavities
  • Demonstrated elastic coupling and sub-femtojoule switching of graphitic stacking states

Related Publication

This work is reported in peer-reviewed research from Tel Aviv University and collaborators on reversible switching of graphitic polytypes in elastically coupled cavities, published in Nature Nanotechnology. (DOI: 10.1038/s41565-025-02121-w)