Thinfilms

Thin films are layers of material with thicknesses from a few nanometers to several micrometers deposited on a substrate. They are engineered so that their properties differ from the bulk material because a large fraction of atoms resides at interfaces and within confined dimensions. Thin films may be continuous or composed of multiple sublayers and can be crystalline, polycrystalline, or amorphous.

Fabrication techniques include physical vapor deposition (PVD) such as evaporation and sputtering; chemical vapor deposition (CVD); atomic layer deposition (ALD); electroplating; and solution-based processes such as spin coating and dip coating for polymers and organics. Advanced methods include pulsed laser deposition and molecular beam epitaxy.

Key properties depend on thickness, composition, microstructure, and interfaces. Optical films influence reflection and transmission; dielectric films govern wave propagation; and metal films support plasmonic or conductive responses. Mechanical properties such as hardness, adhesion, and residual stress are also critical, especially for protective or functional coatings.

Applications cover optics and photonics (anti-reflective and reflective coatings), protective and barrier layers, semiconductor devices and interconnects, solar cells, sensors, MEMS, magnetic storage media, and corrosion protection.

Characterization and metrology span thickness and optical-constant measurements by ellipsometry or spectroscopic reflectometry; surface topography by profilometry, AFM, and SEM; structural analysis by X-ray diffraction; and composition analysis by XPS or EDS. Stress can be assessed from wafer curvature or Raman methods.

Challenges include achieving uniform coverage on complex geometries, controlling interfacial diffusion and stress, ensuring adhesion and environmental stability, and managing fabrication costs.