film - Thin film
Photograph by swanksaloton Flickr.
Molecular beam epitaxy allows film a single layers of atoms to be deposited at a time. It is useful in the manufacture of optics (for reflective, anti-reflective coatings or self-cleaning glass, for instance), electronics (layers of insulators, semiconductors, and conductors form integrated circuits), packaging (i.e., aluminum-coated film Sundance Film Festival PET film), and in contemporary art (see the work of Larry Bell). Thin is a relative term, but most deposition techniques control layer thickness within a few tens of nanometres.
In particular, the use of such coatings on cutting tools can extend the life of these items by several orders of magnitude. Research is being done on a new class of thin film inorganic oxide materials, called amorphous heavy-metal cation multicomponent oxide, which could be used to make transparent transistors that are inexpensive, stable, and environmentally benign. The act of applying a thin film to a surface is thin-film deposition - any technique for depositing a thin film of material onto a substrate or onto previously deposited layers. The rationale for this is that thin-film modules are cheaper to manufacture owing to their reduced material costs, energy costs, handling costs and capital costs.
A very thin film coating (less than a nanometre) is used to produce two-way mirrors. The performance of optical coatings (e.g. An everyday example is the formation of soot on a cool object when it is placed inside a flame.
An everyday example is the formation of frost. Since particles tend to follow a straight path, films deposited by physical means are commonly directional, rather than conformal. Examples of physical deposition include: Some methods fall outside these two categories, relying on a mixture of chemical and physical means: Thin-film technologies are also being developed as a means of substantially reducing the cost of photovoltaic (PV) systems.
Thin-films are used to produce thin-film batteries. Ceramic thin films are in wide use. Thin-film batteries can be deposited directly onto chips or chip packages in any shape or size.
Flexible batteries can be made by printing onto plastic, thin metal foil, or paper. . The whole system is kept in a vacuum deposition chamber, to allow the particles to travel as freely as possible.
This is especially represented in the use of printed electronics (roll-to-roll) processes. Thin films belong to the second and third photovoltaic cell generations. Thin-film printing technology is being used to apply solid-state lithium polymers to a variety of substrates to create unique batteries for specized applications. Similar processes are sometimes used where thickness is not important: for instance, the purification of copper by electroplating, and the deposition of silicon and enriched uranium by a CVD-like process after gas-phase processing. Deposition techniques fall into two broad categories, depending on whether the process is primarily chemical or physical. Here, a fluid precursor undergoes a chemical change at a solid surface, leaving a solid layer.
Since the fluid surrounds the solid object, deposition happens on every surface, with little regard to direction; thin films from chemical deposition techniques tend to be conformal, rather than directional. Chemical deposition is further categorized by the phase of the precursor: Physical deposition uses mechanical or thermodynamic means to produce a thin film of solid. The relatively high hardness and inertness of ceramic materials make this type of thin coating of interest for protection of substrate materials against corrosion, oxidation and wear.
Electronic semiconductor devices and optical coatings are the main applications benefiting from thin film construction. A familiar application of thin films is the household mirror which typically has a thin metal coating on the back of a sheet of glass to form a reflective interface. antireflective, or AR, coatings) are typically enhanced when the thin film coating consists of multiple layers having varying thicknesses and refractive indices.
Thin films are thin material layers ranging from fractions of a nanometre (monolayer) to several micrometres in thickness. Similarly, a periodic structure of alternating thin films of different materials may collectively form a so-called superlattice which exploits the phenomenon of quantum confinement by restricting electronic phenomena to two-dimensions. Work is being done with ferromagnetic thin films for use as computer memory.
Since most engineering materials are held together by relatively high energies, and chemical reactions are not used to store these energies, commercial physical deposition systems tend to require a low-pressure vapor environment to function properly; most can be classified as physical vapor deposition (PVD). The material to be deposited is placed in an energetic, entropic environment, so that particles of material escape its surface. It is also being applied to pharmaceuticals, via thin film drug delivery.
