Fewlayer

As a concept, fewlayer refers to two-dimensional materials that consist of a small number of atomic layers, typically two to five, though definitions vary and some extend up to ten. In few-layer crystals, interlayer interactions produce thickness-dependent optical, electronic, and mechanical properties. Common examples include few-layer graphene (two to five layers), MoS2, WS2, h-BN, and phosphorene in a few-layer form.

Production methods include mechanical exfoliation, which yields high-quality flakes; chemical vapor deposition (CVD) to grow multilayer films with controlled thickness; and liquid-phase exfoliation to produce dispersions of flakes for inks and composites.

Properties and characterization: Interlayer coupling alters band structure; bilayer graphene can have a tunable bandgap with an external field; optical properties depend on thickness. Characterization relies on Raman spectroscopy, where the shape and position of the G and 2D bands vary with layer number; atomic force microscopy (AFM) measures thickness; transmission electron microscopy (TEM) provides structural information.

Applications include electronics and optoelectronics, flexible devices, sensors, energy storage, and catalysis. Research areas focus on scalable fabrication, layer-number control, and integration with other materials.