Field Emission Properties of Two-Dimensional Nanomaterials

Two-dimensional (2D) nanomaterials such as graphene, transition metal dichalcogenides and phosphorene exhibit exceptional field emission characteristics by virtue of their atomic thickness, high aspect ratio and unique electronic structure. The atomically sharp edges and exposed basal planes of these crystals concentrate electric fields, enabling electron tunnelling into vacuum at relatively low macroscopic fields. Quantum confinement normal to the 2D plane modifies the energy barrier, while weak interlayer van der Waals interactions govern stacking in heterostructures. Advances in synthesis have produced vertically aligned and edge-terminated morphologies that enhance emission stability and uniformity. Composite architectures combining 2D layers with graphene or carbon nanotubes further increase field enhancement factors and reduce turn-on fields. The global significance of this research lies in the development of compact cold cathodes for vacuum microelectronics, flat-panel displays, high-resolution electron microscopy tips and energy-efficient electron sources. Ongoing efforts seek to optimise emission coherence, directional control and environmental robustness under high-vacuum and moderate-vacuum conditions.

Research from Nature Portfolio

Vertically aligned MoS₂ nanosheets synthesised by chemical vapour deposition have demonstrated a dramatic reduction in turn-on field due to the proliferation of exposed edge sites. The vertical geometry amplifies local field concentration and yields enhanced current density from few-layer films. Layered composites of WS₂ and reduced graphene oxide reveal a synergistic effect, with the graphene network facilitating charge transport and the WS₂ sheets providing abundant emission sites; field enhancement factors approaching several thousand have been reported, alongside stable currents at low pressures. More recent work on WS₂ nano-petals and nano-bristles grown on carbon nanotube scaffolds has shown that template-driven assembly can produce two distinct 2D morphologies, each lowering the threshold voltage for emission and enabling current saturation control through interface engineering. These studies collectively illustrate how controlled morphology and hybrid architectures bolster emission performance while maintaining material stability.

Field Emission Properties of Two-Dimensional Nanomaterials publication trend

The graph below shows the total number of articles in field emission properties of two-dimensional nanomaterials across all publications each year (not limited to Nature Index journals).

Technical terms

Field emission: Electron emission from a solid surface under a strong electric field via quantum tunnelling.

Fowler–Nordheim tunnelling: Quantum mechanical process describing electron tunnelling through a triangular barrier under high fields.

Turn-on field: The macroscopic electric field at which a defined emission current density (often 1 µA cm⁻²) is achieved.

Field enhancement factor: Ratio of local electric field at an emitter’s apex to the applied macroscopic field.

Van der Waals materials: Layered crystals whose individual sheets are bound by weak intermolecular forces, enabling exfoliation into 2D structures.

References

1. Microscopic Quantum Transport Processes of Out‐of‐Plane Charge Flow in 2D Semiconductors Analyzed by a Fowler–Nordheim Tunneling Probe. Advanced Electronic Materials (2023).
2. Cold Cathodes with Two-Dimensional van der Waals Materials. Nanomaterials (2023).
3. Synthesis and characterization of vertically standing MoS2 nanosheets. Scientific Reports (2016).
4. Superior Field Emission Properties of Layered WS2-RGO Nanocomposites. Scientific Reports (2013).
5. Field Emission Characterization of MoS2 Nanoflowers. Nanomaterials (2019).
6. WS2 Nano-petals and Nano-bristles Supported on Carbon Nanotubes for Electron Emission Applications. Scientific Reports (2019).
7. Electron emission from a two-dimensional crystal with atomic thickness. AIP Advances (2013).