nanolayers

Nanolayers refer to films with thickness in the nanometer range, often defined as 1-100 nm, though sometimes up to tens of nanometers. They are engineered to impart specific properties to a substrate, including chemical, optical, electrical, or mechanical attributes. They can be single-layer or stacks of several nanometer-scale layers, and they may be crystalline, amorphous, or polycrystalline.

Fabrication methods include chemical vapor deposition (CVD), atomic layer deposition (ALD), physical vapor deposition (PVD) such as sputtering and evaporation, solution-based spin coating, Langmuir-Blodgett deposition, and molecular self-assembly. Growth modes include layer-by-layer (Frank-van der Merwe), island growth (Volmer-Weber), and mixed modes.

Nanolayers exhibit a range of size- and structure-dependent properties, including quantum-size effects at very thin thicknesses, improved barrier properties against diffusion, enhanced hardness or wear resistance, and tailored refractive index with optical interference effects. Characterization techniques commonly used to assess nanolayers include X-ray reflectivity, ellipsometry, atomic force microscopy, transmission electron microscopy, and various spectroscopic methods.

Applications span protective coatings, diffusion barriers in microelectronics, optical coatings and anti-reflective layers, photovoltaic cells, batteries and supercapacitors, sensors, and catalysis. Representative materials include graphene and other two-dimensional materials, aluminum oxide, silicon dioxide, titanium dioxide, hexagonal boron nitride, and multilayer oxide or metal stacks.

Challenges in the field include achieving uniformity over large areas, controlling interfacial roughness and stress to avoid delamination, scaling deposition processes cost-effectively, and ensuring stability under operational conditions. Ongoing research continues to expand material choices and refine deposition techniques for broader industrial use.