gasfasdeposition

Gas-phase deposition is a family of thin-film fabrication methods in which material is delivered to a substrate from a gas or vapor. It is distinguished from liquid- or solid-phase deposition by the transport and reaction of gaseous precursors, often under reduced pressure or in a controlled atmosphere. The techniques are used to produce coatings and layered structures with a wide range of materials and properties.

The main categories are chemical vapor deposition (CVD) and physical vapor deposition (PVD). In CVD, volatile precursors react chemically on or near the substrate to form the desired film, with byproducts removed from the reactor. Variants include plasma-enhanced CVD (PECVD), which uses plasma to promote reactions at lower temperatures, and atomic layer deposition (ALD), which employs self-limiting surface reactions for atomic-scale thickness control. In PVD, material is vaporized from a solid target and then transported to the substrate where it condenses; methods include evaporation and sputtering, often performed under vacuum. Molecular beam epitaxy (MBE) is a high-vacuum, gas-phase technique used for precise epitaxial growth.

Process parameters such as substrate temperature, chamber pressure, gas flow, and reactor design determine deposition rate, film uniformity, conformality, and microstructure. Gas-phase deposition is widely used in electronics, photovoltaics, optics, and protective coatings, enabling materials like SiO2, Si3N4, Al2O3, TiN, ZnO, and various oxides and nitrides. Challenges include precursor availability and stability, byproduct management, and ensuring film quality for complex geometries.