Incandescence is the emission of electromagnetic radiation from a hot body as a result of its temperature. The term derives to glow white. Incandescence is a special case of thermal radiation. Incandescence refers to visible light, while thermal radiation refers to infrared or any other electromagnetic radiation. For information on the intensity and spectrum of incandescence, see thermal radiation. In practice all solid or liquid substances start to glow around 798 K, with a mildly dull red color, whether or not a chemical reaction takes place that produces light as a result of an exothermic process; this limit is called the Draper point. The incandescence does not vanish below that temperature, but it is too weak in the visible spectrum to be perceivable. At higher temperatures, the substance becomes brighter and its color changes from red towards white and blue. Incandescence is exploited in incandescent light bulbs, in which a filament is heated to a temperature at which a fraction of the radiation falls in the visible spectrum.
The majority of the radiation however, is emitted in the infrared part of the spectrum, rendering incandescent lights inefficient as a light source. If the filament could be made hotter, efficiency would increase. More efficient light sources, such as fluorescent lamps and LEDs, do not function by incandescence. Sunlight is the incandescence of the "white hot" surface of the sun; the word incandescent is used figuratively to describe a person, so angry that they are imagined to glow or burn red hot or white hot. Red heat List of light sources
Silver is a chemical element with symbol Ag and atomic number 47. A soft, lustrous transition metal, it exhibits the highest electrical conductivity, thermal conductivity, reflectivity of any metal; the metal is found in the Earth's crust in the pure, free elemental form, as an alloy with gold and other metals, in minerals such as argentite and chlorargyrite. Most silver is produced as a byproduct of copper, gold and zinc refining. Silver has long been valued as a precious metal. Silver metal is used in many bullion coins, sometimes alongside gold: while it is more abundant than gold, it is much less abundant as a native metal, its purity is measured on a per-mille basis. As one of the seven metals of antiquity, silver has had an enduring role in most human cultures. Other than in currency and as an investment medium, silver is used in solar panels, water filtration, ornaments, high-value tableware and utensils, in electrical contacts and conductors, in specialized mirrors, window coatings, in catalysis of chemical reactions, as a colorant in stained glass and in specialised confectionery.
Its compounds are used in X-ray film. Dilute solutions of silver nitrate and other silver compounds are used as disinfectants and microbiocides, added to bandages and wound-dressings and other medical instruments. Silver is similar in its physical and chemical properties to its two vertical neighbours in group 11 of the periodic table and gold, its 47 electrons are arranged in the configuration 4d105s1 to copper and gold. This distinctive electron configuration, with a single electron in the highest occupied s subshell over a filled d subshell, accounts for many of the singular properties of metallic silver. Silver is an soft and malleable transition metal, though it is less malleable than gold. Silver crystallizes in a face-centered cubic lattice with bulk coordination number 12, where only the single 5s electron is delocalized to copper and gold. Unlike metals with incomplete d-shells, metallic bonds in silver are lacking a covalent character and are weak; this observation explains the low high ductility of single crystals of silver.
Silver has a brilliant white metallic luster that can take a high polish, and, so characteristic that the name of the metal itself has become a colour name. Unlike copper and gold, the energy required to excite an electron from the filled d band to the s-p conduction band in silver is large enough that it no longer corresponds to absorption in the visible region of the spectrum, but rather in the ultraviolet. Protected silver has greater optical reflectivity than aluminium at all wavelengths longer than ~450 nm. At wavelengths shorter than 450 nm, silver's reflectivity is inferior to that of aluminium and drops to zero near 310 nm. High electrical and thermal conductivity is common to the elements in group 11, because their single s electron is free and does not interact with the filled d subshell, as such interactions lower electron mobility; the electrical conductivity of silver is the greatest of all metals, greater than copper, but it is not used for this property because of the higher cost.
An exception is in radio-frequency engineering at VHF and higher frequencies where silver plating improves electrical conductivity because those currents tend to flow on the surface of conductors rather than through the interior. During World War II in the US, 13540 tons of silver were used in electromagnets for enriching uranium because of the wartime shortage of copper. Pure silver has the highest thermal conductivity of any metal, although the conductivity of carbon and superfluid helium-4 are higher. Silver has the lowest contact resistance of any metal. Silver forms alloys with copper and gold, as well as zinc. Zinc-silver alloys with low zinc concentration may be considered as face-centred cubic solid solutions of zinc in silver, as the structure of the silver is unchanged while the electron concentration rises as more zinc is added. Increasing the electron concentration further leads to body-centred cubic, complex cubic, hexagonal close-packed phases. Occurring silver is composed of two stable isotopes, 107Ag and 109Ag, with 107Ag being more abundant.
This equal abundance is rare in the periodic table. The atomic weight is 107.8682 u. Both isotopes of silver are produced in stars via the s-process, as well as in supernovas via the r-process. Twenty-eight radioisotopes have been characterized, the most stable being 105Ag with a half-life of 41.29 days, 111Ag with a half-life of 7.45 days, 112Ag with a half-life of 3.13 hours. Silver has numerous nuclear isomers, the most stable being 108mAg, 110mAg and 106mAg. All of the remaining radioactive isotopes have half-lives of less than an hour, the majority of these have half-lives of less than three minutes. Isotopes of silver range in relative atomic mass from 92.950 u
Boron is a chemical element with symbol B and atomic number 5. Produced by cosmic ray spallation and supernovae and not by stellar nucleosynthesis, it is a low-abundance element in the Solar system and in the Earth's crust. Boron is concentrated on Earth by the water-solubility of its more common occurring compounds, the borate minerals; these are mined industrially as evaporites, such as kernite. The largest known boron deposits are in the largest producer of boron minerals. Elemental boron is a metalloid, found in small amounts in meteoroids but chemically uncombined boron is not otherwise found on Earth. Industrially pure boron is produced with difficulty because of refractory contamination by carbon or other elements. Several allotropes of boron exist: amorphous boron is a brown powder; the primary use of elemental boron is as boron filaments with applications similar to carbon fibers in some high-strength materials. Boron is used in chemical compounds. About half of all boron consumed globally is an additive in fiberglass for insulation and structural materials.
The next leading use is in polymers and ceramics in high-strength, lightweight structural and refractory materials. Borosilicate glass is desired for its greater strength and thermal shock resistance than ordinary soda lime glass. Boron as sodium perborate is used as a bleach. A small amount of boron is used as a dopant in semiconductors, reagent intermediates in the synthesis of organic fine chemicals. A few boron-containing organic pharmaceuticals are in study. Natural boron is composed of two stable isotopes, one of which has a number of uses as a neutron-capturing agent. In biology, borates have low toxicity in mammals, but are more toxic to arthropods and are used as insecticides. Boric acid is mildly antimicrobial, several natural boron-containing organic antibiotics are known. Boron is an essential plant nutrient and boron compounds such as borax and boric acid are used as fertilizers in agriculture, although it's only required in small amounts, with excess being toxic. Boron compounds play a strengthening role in the cell walls of all plants.
There is no consensus on whether boron is an essential nutrient for mammals, including humans, although there is some evidence it supports bone health. The word boron was coined from borax, the mineral from which it was isolated, by analogy with carbon, which boron resembles chemically. Borax, its mineral form known as tincal, glazes were used in China from AD 300, some crude borax reached the West, where the Perso-Arab alchemist Jābir ibn Hayyān mentioned it in AD 700. Marco Polo brought some glazes back to Italy in the 13th century. Agricola, around 1600, reports the use of borax as a flux in metallurgy. In 1777, boric acid was recognized in the hot springs near Florence and became known as sal sedativum, with medical uses; the rare mineral is called sassolite, found at Sasso, Italy. Sasso was the main source of European borax from 1827 to 1872. Boron compounds were rarely used until the late 1800s when Francis Marion Smith's Pacific Coast Borax Company first popularized and produced them in volume at low cost.
Boron was not recognized as an element until it was isolated by Sir Humphry Davy and by Joseph Louis Gay-Lussac and Louis Jacques Thénard. In 1808 Davy observed that electric current sent through a solution of borates produced a brown precipitate on one of the electrodes. In his subsequent experiments, he used potassium to reduce boric acid instead of electrolysis, he named the element boracium. Gay-Lussac and Thénard used iron to reduce boric acid at high temperatures. By oxidizing boron with air, they showed. Jöns Jakob Berzelius identified boron as an element in 1824. Pure boron was arguably first produced by the American chemist Ezekiel Weintraub in 1909; the earliest routes to elemental boron involved the reduction of boric oxide with metals such as magnesium or aluminium. However, the product is always contaminated with borides of those metals. Pure boron can be prepared by reducing volatile boron halides with hydrogen at high temperatures. Ultrapure boron for use in the semiconductor industry is produced by the decomposition of diborane at high temperatures and further purified by the zone melting or Czochralski processes.
The production of boron compounds does not involve the formation of elemental boron, but exploits the convenient availability of borates. Boron is similar to carbon in its capability to form stable covalently bonded molecular networks. Nominally disordered boron contains regular boron icosahedra which are, bonded randomly to each other without long-range order. Crystalline boron is a hard, black material with a melting point of above 2000 °C, it forms four major polymorphs: β-rhombohedral, γ and β-tetragonal. Most of the phases are based on B12 icosahedra, but the γ-phase can be described as a rocksalt-type arrangement of the icosahedra and B2 atomic pairs, it can be produced by compressing other boron phases to 12–20 GPa and heating to 1500–1800 °C. The T phase is produced at similar pressures, but higher temperatures of 1800–2200 °C; as to the α and β phases, they might both coexist at ambient conditions with the β phase being more stable
General Electric Company is an American multinational conglomerate incorporated in New York and headquartered in Boston. As of 2018, the company operates through the following segments: aviation, power, renewable energy, digital industry, additive manufacturing, venture capital and finance and oil and gas. In 2018, GE ranked among the Fortune 500 as the 18th-largest firm in the U. S. by gross revenue. In 2011, GE ranked among the Fortune 20 as the 14th-most profitable company but has since severely underperformed the market as its profitability collapsed. Two employees of GE—Irving Langmuir and Ivar Giaever —have been awarded the Nobel Prize. During 1889, Thomas Edison had business interests in many electricity-related companies including Edison Lamp Company, a lamp manufacturer in East Newark, New Jersey. P. Morgan and the Vanderbilt family for Edison's lighting experiments. In 1889, Morgan & Co. a company founded by J. P. Morgan and Anthony J. Drexel, financed Edison's research and helped merge those companies under one corporation to form Edison General Electric Company, incorporated in New York on April 24, 1889.
The new company acquired Sprague Electric Railway & Motor Company in the same year. In 1880, Gerald Waldo Hart formed the American Electric Company of New Britain, which merged a few years with Thomson-Houston Electric Company, led by Charles Coffin. In 1887, Hart left to become superintendent of the Edison Electric Company of Missouri. General Electric was formed through the 1892 merger of Edison General Electric Company of Schenectady, New York, Thomson-Houston Electric Company of Lynn, with the support of Drexel, Morgan & Co. Both plants continue to operate under the GE banner to this day; the company was incorporated in New York, with the Schenectady plant used as headquarters for many years thereafter. Around the same time, General Electric's Canadian counterpart, Canadian General Electric, was formed. In 1896, General Electric was one of the original 12 companies listed on the newly formed Dow Jones Industrial Average, where it remained a part of the index for 122 years, though not continuously.
In 1911, General Electric absorbed the National Electric Lamp Association into its lighting business. GE established its lighting division headquarters at Nela Park in Ohio; the lighting division has since remained in the same location. Owen D. Young, through GE, founded the Radio Corporation of America in 1919, after purchasing the Marconi Wireless Telegraph Company of America, he aimed to expand international radio communications. GE used RCA as its retail arm for radio sales. In 1926, RCA co-founded the National Broadcasting Company, which built two radio broadcasting networks. In 1930, General Electric was charged with antitrust violations and decided to divest itself of RCA. In 1927, Ernst Alexanderson of GE made the first demonstration of his television broadcasts at his General Electric Realty Plot home at 1132 Adams Rd, New York. On January 13, 1928, he made what was said to be the first broadcast to the public in the United States on GE's W2XAD: the pictures were picked up on 1.5 square inch screens in the homes of four GE executives.
The sound was broadcast on GE's WGY. Experimental television station W2XAD evolved into station WRGB which, along with WGY and WGFM, was owned and operated by General Electric until 1983. Led by Sanford Alexander Moss, GE moved into the new field of aircraft turbo superchargers. GE introduced the first set of superchargers during World War I, continued to develop them during the interwar period. Superchargers became indispensable in the years prior to World War II. GE supplied 300,000 turbo superchargers for use in bomber engines; this work led the U. S. Army Air Corps to select GE to develop the nation's first jet engine during the war; this experience, in turn, made GE a natural selection to develop the Whittle W.1 jet engine, demonstrated in the United States in 1941. GE was ranked ninth among United States corporations in the value of wartime production contracts. Although, their early work with Whittle's designs was handed to Allison Engine Company. GE Aviation emerged as one of the world's largest engine manufacturers, bypassing the British company, Rolls-Royce plc.
Some consumers boycotted GE light bulbs and other products during the 1980s and 1990s. The purpose of the boycott was to protest against GE's role in nuclear weapons production. In 2002, GE acquired the wind power assets of Enron during its bankruptcy proceedings. Enron Wind was the only surviving U. S. manufacturer of large wind turbines at the time, GE increased engineering and supplies for the Wind Division and doubled the annual sales to $1.2 billion in 2003. It acquired ScanWind in 2009. In 2015, GE Power garnered press attention when a model 9FB gas turbine in Texas was shut down for two months due to the break of a turbine blade; this model uses similar blade technology to GE's newest and most efficient model, the 9HA. After the break, GE developed heat treatment methods. Gas turbines represent a significant portion of GE Power's revenue, represent a significant portion of the power generation fleet of several utility companies in the United States. Chubu Electric of Japan and Électricité de France had units that were impacted.
Copper is a chemical element with symbol Cu and atomic number 29. It is a soft and ductile metal with high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkish-orange color. Copper is used as a conductor of heat and electricity, as a building material, as a constituent of various metal alloys, such as sterling silver used in jewelry, cupronickel used to make marine hardware and coins, constantan used in strain gauges and thermocouples for temperature measurement. Copper is one of the few metals; this led to early human use in several regions, from c. 8000 BC. Thousands of years it was the first metal to be smelted from sulfide ores, c. 5000 BC, the first metal to be cast into a shape in a mold, c. 4000 BC and the first metal to be purposefully alloyed with another metal, tin, to create bronze, c. 3500 BC. In the Roman era, copper was principally mined on Cyprus, the origin of the name of the metal, from aes сyprium corrupted to сuprum, from which the words derived and copper, first used around 1530.
The encountered compounds are copper salts, which impart blue or green colors to such minerals as azurite and turquoise, have been used and as pigments. Copper used in buildings for roofing, oxidizes to form a green verdigris. Copper is sometimes used in decorative art, both in its elemental metal form and in compounds as pigments. Copper compounds are used as bacteriostatic agents and wood preservatives. Copper is essential to all living organisms as a trace dietary mineral because it is a key constituent of the respiratory enzyme complex cytochrome c oxidase. In molluscs and crustaceans, copper is a constituent of the blood pigment hemocyanin, replaced by the iron-complexed hemoglobin in fish and other vertebrates. In humans, copper is found in the liver and bone; the adult body contains between 2.1 mg of copper per kilogram of body weight. Copper and gold are in group 11 of the periodic table; the filled d-shells in these elements contribute little to interatomic interactions, which are dominated by the s-electrons through metallic bonds.
Unlike metals with incomplete d-shells, metallic bonds in copper are lacking a covalent character and are weak. This observation explains the low high ductility of single crystals of copper. At the macroscopic scale, introduction of extended defects to the crystal lattice, such as grain boundaries, hinders flow of the material under applied stress, thereby increasing its hardness. For this reason, copper is supplied in a fine-grained polycrystalline form, which has greater strength than monocrystalline forms; the softness of copper explains its high electrical conductivity and high thermal conductivity, second highest among pure metals at room temperature. This is because the resistivity to electron transport in metals at room temperature originates from scattering of electrons on thermal vibrations of the lattice, which are weak in a soft metal; the maximum permissible current density of copper in open air is 3.1×106 A/m2 of cross-sectional area, above which it begins to heat excessively. Copper is one of a few metallic elements with a natural color other than silver.
Pure copper acquires a reddish tarnish when exposed to air. The characteristic color of copper results from the electronic transitions between the filled 3d and half-empty 4s atomic shells – the energy difference between these shells corresponds to orange light; as with other metals, if copper is put in contact with another metal, galvanic corrosion will occur. Copper does not react with water, but it does react with atmospheric oxygen to form a layer of brown-black copper oxide which, unlike the rust that forms on iron in moist air, protects the underlying metal from further corrosion. A green layer of verdigris can be seen on old copper structures, such as the roofing of many older buildings and the Statue of Liberty. Copper tarnishes when exposed to some sulfur compounds, with which it reacts to form various copper sulfides. There are 29 isotopes of copper. 63Cu and 65Cu are stable, with 63Cu comprising 69% of occurring copper. The other isotopes are radioactive, with the most stable being 67Cu with a half-life of 61.83 hours.
Seven metastable isotopes have been characterized. Isotopes with a mass number above 64 decay by β−, whereas those with a mass number below 64 decay by β+. 64Cu, which has a half-life of 12.7 hours, decays both ways.62Cu and 64Cu have significant applications. 62Cu is used in 62Cu-PTSM as a radioactive tracer for positron emission tomography. Copper is produced in massive stars and is present in the Earth's crust in a proportion of about 50 parts per million. In nature, copper occurs in a variety of minerals, including native copper, copper sulfides such as chalcopyrite, digenite and chalcocite, copper sulfosalts such as tetrahedite-tennantite, enargite, copper carbonates such as azurite and malachite, as copper or copper oxides such as cuprite and tenorite, respectively; the largest mass of elemental copper discovered weighed 420 tonnes and was found in 1857 on the Keweenaw Peninsula in Michigan, US. Native copper is a polycrystal
Planar Systems, Inc. is a U. S. digital display manufacturing corporation based in Oregon. Founded in 1983 as a spin-off from Tektronix, it was the first U. S. manufacturer of electroluminescent digital displays. Planar makes a variety of other specialty displays. Since 2015, it has been a subsidiary of Shenzhen, China-based Leyard Optoelectronic Co.. Planar was founded in 1983 by Jim Hurd, Chris King, John Laney and others as a spin-off from the Solid State Research and Development Group of the Beaverton, based Tektronix. In 1986, a division formed InFocus. In 1991, Planar purchased a competitor in Espoo, Finland; this location now serves as the company's European headquarters. Planar's executives took the company public in 1993, listing the stock on the NASDAQ boards Planar acquired Tektronix's avionics display business, creating the short-lived Planar Advance in 1994. Standish Industries, a manufacturer of flat panel LCDs in Lake Mills, was sold to Planar in 1997; this plant was closed in 2002 as worldwide LCD manufacturing shifted to East Asian countries.
On April 23, 2002, DOME Imaging Systems was purchased by Planar and became the company's medical business unit. Planar acquired Clarity Visual Systems on September 12, 2006, now referred to as the Control Room and Signage business unit. On May 23, 2007, Planar acquired Runco International, a leading brand in the high-end, custom home theater market. On August 6, 2008, Planar sold its medical business unit to NDS Surgical Imaging. In November 2012, Planar announced the sale of its electroluminescent business to Beneq Oy, a supplier of production and research equipment for thin film coatings. Under the terms of the transaction, consideration consists of a $6.5 million base purchase price, of which $3.9 million was paid in cash at closing and $2.6 million was paid in the form of a promissory note. Planar was purchased by Leyard Optoelectronic Co. of China in 2015 for $157 million. It became a subsidiary after trading on the NASDAQ under the symbol PLNR. In November 2016, Planar announced that it was to enter a merger agreement with NaturalPoint Inc. which sells infrared point tracking systems for use on CGI movie sets, home use both for assisted computing and computer gaming.
The merger was finalized in January 2017. NaturalPoint will remain a separate business with its own executive team and market initiatives. Video Walls Large Format LCD Displays Touch Screen Monitors Rear Projection Video Walls 4K Large Format Display Displays LCD Monitors Video Wall Processors Planar assembles and services videowalls and other displays in Hillsboro. Planar's EL manufacturing operations were consolidated into Planar's Espoo, Finland facility in 2002. Additional large-format displays are integrated in Albi, France. On November 27, 2015, Planar closed its sale to become a subsidiary of Leyard Optoelectronic Co. an LED display product corporation. With the merger, Planar increased its capabilities to offer indoor, outdoor and creative LED display solutions. Headquarters operations for Planar remain in OR following the sale. In addition to its Oregon, U. S. headquarters, Planar has worldwide reach. Its sales offices are located in Europe, North America, Asia, it has manufacturing facilities in France, North America, Finland.
Government Video Salute 2013 Planar UltraRes Series Commercial Integrator BEST 2013 Video Wall Solution: Clarity Matrix MultiTouch LCD Video Wall Sound & Video Contractor Most Innovative Product 2013 Planar UltraRes Series Technology Integrator Exc!te Award 2013 Planar UltraRes Series rAVE 2013 Best New Video Wall Product: Planar Mosaic Video Wall Best of Show 2014 Clarity Matrix LCD Video Wall G2 Architecture Technology Integrator Daily - ExC!te Award 2014 Planar EP-Series 4K Systems Contractor News Installation Product Award 2014 Most Innovative Video Display: Planar UltraRes Series Tom’s Hardware Smart Buy 2014 Planar IX2850 rAVe 2015 Best Indoor Display for DSE: Planar DirectLight LED Video Wall System DIGI Award 2015 Best 4K Display Device: Planar UltraRes Series & DIGI Award 2015 Best New Display Device, Large Screen: Clarity Matrix LCD Video Wall with G2 Architecture Silicon Forest List of companies based in Oregon Official website Hoover's Profile of Planar Systems International Directory of Company Histories, Volume 61 via Answers.com Planar Systems topic at New York Times
A semiconductor material has an electrical conductivity value falling between that of a metal, like copper, etc. and an insulator, such as glass. Their resistance decreases as their temperature increases, behaviour opposite to that of a metal, their conducting properties may be altered in useful ways by the deliberate, controlled introduction of impurities into the crystal structure. Where two differently-doped regions exist in the same crystal, a semiconductor junction is created; the behavior of charge carriers which include electrons and electron holes at these junctions is the basis of diodes and all modern electronics. Some examples of semiconductors are silicon and gallium arsenide. After silicon, gallium arsenide is the second most common semiconductor used in laser diodes, solar cells, microwave frequency integrated circuits, others. Silicon is a critical element for fabricating most electronic circuits. Semiconductor devices can display a range of useful properties such as passing current more in one direction than the other, showing variable resistance, sensitivity to light or heat.
Because the electrical properties of a semiconductor material can be modified by doping, or by the application of electrical fields or light, devices made from semiconductors can be used for amplification and energy conversion. The conductivity of silicon is increased by adding a small amount of trivalent atoms; this process is known as doping and resulting semiconductors are known as doped or extrinsic semiconductors. Apart from doping, the conductivity of a semiconductor can be improved by increasing its temperature; this is contrary to the behaviour of a metal in which conductivity decreases with increase in temperature. The modern understanding of the properties of a semiconductor relies on quantum physics to explain the movement of charge carriers in a crystal lattice. Doping increases the number of charge carriers within the crystal; when a doped semiconductor contains free holes it is called "p-type", when it contains free electrons it is known as "n-type". The semiconductor materials used in electronic devices are doped under precise conditions to control the concentration and regions of p- and n-type dopants.
A single semiconductor crystal can have many p- and n-type regions. Although some pure elements and many compounds display semiconductor properties, silicon and compounds of gallium are the most used in electronic devices. Elements near the so-called "metalloid staircase", where the metalloids are located on the periodic table, are used as semiconductors; some of the properties of semiconductor materials were observed throughout the mid 19th and first decades of the 20th century. The first practical application of semiconductors in electronics was the 1904 development of the cat's-whisker detector, a primitive semiconductor diode used in early radio receivers. Developments in quantum physics in turn allowed the development of the transistor in 1947 and the integrated circuit in 1958. Variable electrical conductivity Semiconductors in their natural state are poor conductors because a current requires the flow of electrons, semiconductors have their valence bands filled, preventing the entry flow of new electrons.
There are several developed techniques that allow semiconducting materials to behave like conducting materials, such as doping or gating. These modifications have two outcomes: p-type; these refer to the shortage of electrons, respectively. An unbalanced number of electrons would cause a current to flow through the material. Heterojunctions Heterojunctions occur when two differently doped semiconducting materials are joined together. For example, a configuration could consist of n-doped germanium; this results in an exchange of electrons and holes between the differently doped semiconducting materials. The n-doped germanium would have an excess of electrons, the p-doped germanium would have an excess of holes; the transfer occurs until equilibrium is reached by a process called recombination, which causes the migrating electrons from the n-type to come in contact with the migrating holes from the p-type. A product of this process is charged ions. Excited electrons A difference in electric potential on a semiconducting material would cause it to leave thermal equilibrium and create a non-equilibrium situation.
This introduces electrons and holes to the system, which interact via a process called ambipolar diffusion. Whenever thermal equilibrium is disturbed in a semiconducting material, the number of holes and electrons changes; such disruptions can occur as a result of a temperature difference or photons, which can enter the system and create electrons and holes. The process that creates and annihilates electrons and holes are called generation and recombination. Light emission In certain semiconductors, excited electrons can relax by emitting light instead of producing heat; these semiconductors are used in the construction of light-emitting diodes and fluorescent quantum dots. High thermal conductivitySemiconductors with high thermal conductivity can be used for heat dissipation and improving thermal management of electronics. Thermal energy conversion Semiconductors have large thermoelectric power factors making them useful in thermoelectric generators, as well as high thermoelectric figures of merit making them useful in thermoelectric coolers.
A large number of elements and compounds have semiconducting properties, including: Certain pure elements are found in Group 14 of the p