Thin films are layers of material ranging in thickness from nanometers (10−9 m) to micrometers (10−6 m). They are used commonly for coating optical surfaces and also for coatings on semiconductors. Thin films are used to make mirrors, and these can be finely tuned (in terms of their composition and thickness) to obtain optical surfaces with a wide variety of specific reflection properties, such as wavelength specific mirrors and two-way mirrors (the ones that are transparent from one side but reflective from the other). Thin films are also very useful for coating semiconductors to tune their conductive properties for different applications.
