2Dmaterial

2Dmaterial is a general term used to describe crystalline solids that consist of a single layer of atoms or a few layers only a few nanometers thick. These materials feature strong in-plane covalent bonds and relatively weak interlayer van der Waals forces, which enable exfoliation from layered bulk precursors and the isolation of ultrathin sheets. Graphene, a single layer of carbon atoms, is the best known example, with hexagonal boron nitride and transition metal dichalcogenides such as MoS2 and WS2 following closely. Other families include phosphorene, MXenes, and various layered oxides and sulfides.

Properties vary across materials. In-plane properties are typically robust, giving high mechanical strength and stiffness. Electronic behavior ranges from metallic to semiconducting; notably, graphene lacks an intrinsic band gap, while monolayer TMDCs possess direct band gaps suitable for electronics and optoelectronics. The reduced dimensionality enhances light–matter interactions, exciton binding energies, and nonlinear optical effects. Stacking different 2D layers creates van der Waals heterostructures with emergent properties not present in the individual layers.

Synthesis and processing methods include mechanical exfoliation from bulk crystals, chemical vapor deposition for large-area films, and liquid-phase exfoliation in suitable solvents. Chemical synthesis and bottom-up approaches are also pursued for certain materials to tailor composition and defects.

Applications span nanoelectronics, optoelectronics, flexible and transparent devices, energy storage and catalysis, sensing, and membranes for filtration or separation. 2D materials are also explored as catalysts, lubricants, and protective coatings at reduced thickness.

Challenges include achieving uniform large-area production, reducing contact resistance, ensuring environmental stability and scalable integration with existing semiconductor processes, and precise control of defects and layer alignment. Ongoing research focuses on heterostructures, controlled doping, and functionalization to tailor properties for specific uses.