Grain Boundary Effects in Polycrystalline Graphene Systems

Polycrystalline graphene consists of multiple crystalline domains joined by grain boundaries, where differences in lattice orientation and atomic registry produce line defects that strongly influence material properties. These boundaries act as scattering centres for charge carriers and phonons, reducing electrical and thermal conductivities compared with single-crystal graphene. Mechanical stabilities are likewise modulated by the nature and density of boundary defects, which can induce out-of-plane buckling, local strain accumulation and altered fracture mechanisms. Unusual tribological phenomena have also been attributed to dynamic deformations at grain junctions, leading in some cases to negative frictional responses. Across applications—from flexible electronics and high-frequency devices to sensors and superlubric contacts—the precise control and engineering of grain boundaries have emerged as critical for optimising performance at wafer scale. Recent advances have further revealed routes to harness boundary-guided self-assembly, reversible defect tuning and scalable growth processes, thereby transforming what was once considered an imperfection into a means of functionalising two-dimensional materials.

Research from Nature Portfolio

Recent studies have demonstrated that corrugated grain boundaries can exhibit negative friction coefficients under shear, a behaviour traced to dynamic buckling of dislocation protrusions which dissipates energy non-monotonically with sliding velocity. This discovery suggests design principles for large-scale dry superlubric interfaces built from polycrystalline two-dimensional materials. Other work has systematically varied grain size via controlled chemical vapour deposition, revealing that thermal conductivity declines steeply with decreasing grain diameter due to boundary resistance, whereas electrical resistivity remains remarkably low and exhibits only a minor transport gap. The study established scaling laws that guide the tailoring of optoelectronic and thermoelectric performance. Furthermore, efforts in reversible defect engineering have shown that boundary chemistry and thermodynamics can be manipulated to switch electronic mobility by an order of magnitude in monolayer channels, with water permeation assays confirming that changes localise at grain junctions. This thermodynamic control enables repeatable adjustment of electronic and mechanical properties over large areas.

Grain Boundary Effects in Polycrystalline Graphene Systems publication trend

The graph below shows the total number of articles in grain boundary effects in polycrystalline graphene systems across all publications each year (not limited to Nature Index journals).

Technical terms

Grain boundary: A one-dimensional defect separating two crystalline domains with different lattice orientations, often comprising non-hexagonal rings or dislocation cores.

Polycrystalline graphene: A sheet of graphene composed of multiple crystalline grains rather than a single continuous lattice, connected by grain boundaries.

Out-of-plane buckling: Localised bending or warping of the graphene sheet at a grain boundary, altering electronic and mechanical properties.

Friction coefficient: A dimensionless measure of resistance to sliding, which in polycrystalline interfaces can become negative due to dynamic boundary deformations.

Magic angle: A specific small twist angle between graphene layers (near 1.1°) that gives rise to flat electronic bands and correlated phenomena such as superconductivity.

References

1. Non-Amontons frictional behaviors of grain boundaries at layered material interfaces. Nature Communications (2024).
2. Grain Boundary Guided Folding of Graphene for Twisted Bilayer Graphene. Nanomaterials (2025).
3. First principles study of electronic structure and transport in graphene grain boundaries. 2D Materials (2024).
4. Tailoring the thermal and electrical transport properties of graphene films by grain size engineering. Nature Communications (2017).
5. Reversible defect engineering in graphene grain boundaries. Nature Communications (2019).