multicouches

Multicouches, or multilayer structures, are assemblies built from multiple layers of materials stacked on a substrate. Each layer contributes specific properties, such as mechanical strength, barrier performance, electrical conductivity, optical characteristics, or chemical resistance. The order, thickness, and material choices determine the overall behavior, including interfacial adhesion and thermal expansion.

Common architectures include a substrate, adhesion layer, one or more functional layers, and a protective or encapsulating cap. Materials span ceramics, metals, polymers, and carbon-based films. In optics, dielectric multilayers alternating high- and low-refractive-index layers create mirrors or anti-reflection coatings. In electronics, multilayer dielectrics or metal stacks enable capacitors and interconnects.

Fabrication methods include chemical vapor deposition, physical vapor deposition such as sputtering and evaporation, atomic layer deposition, and solution-based processes such as spin coating or dip coating. Roll-to-roll coating extends these techniques to flexible substrates.

Key considerations include adhesion at interfaces, diffusion and intermixing, residual stress and cracking, and thermal expansion mismatch. Optical interference effects can be engineered through layer thickness. Characterization relies on microscopy, spectroscopy, ellipsometry, and electrical tests.

Applications span optics (coatings and mirrors), protective and decorative finishes, barrier films for packaging, energy devices (solar cells, batteries, supercapacitors), and membranes for separation.

Examples include anti-reflective coatings on lenses, dielectric mirrors in laser systems, multilayer stacks in microelectronics packaging, and multilayer polymer films used in food packaging.