Single crystal
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2008-06-26T11:14:33Z
Vsmith
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[[Image:KDP crystal.jpg|thumb|righth|250px|A huge [[Monopotassium phosphate|KDP]] crystal grown from a [[seed crystal]] in a [[supersaturated]] aqueous solution at [[LLNL]] which is to be cut into slices and used on the [[National Ignition Facility]] for [[frequency doubling]] and tripling.]]
A '''single crystal''', also called '''monocrystal''', is a [[crystal]]line [[solid]] in which the [[crystal lattice]] of the entire sample is continuous and unbroken to the edges of the sample, with no [[grain boundaries]]. The opposite of a single crystal sample is an amorphous structure where the atomic position is limited to short range order only. In between the two extremes exist ''[[polycrystalline]]'' and ''[[paracrystalline]]'' phases, which are made up of a number of smaller crystals known as ''[[crystallite]]s''. Because of a variety of [[entropy|entropic]] effects on the microstructure of solids, including the distorting effects of [[impurity|impurities]] and the mobility of [[crystallographic defect]]s and [[dislocation]]s, single crystals of meaningful size are exceedingly rare in nature, and can also be difficult to produce in the laboratory under controlled conditions (see also [[recrystallisation]]).
[[Image:Monokristalines Silizium für die Waferherstellung.jpg|thumb|left|80px|Single-crystal [[silicon]] [[Boule (crystal)|boule]].]]
[[Image:Synthetic quartz crystal.jpg|thumb|A single-crystal [[quartz]] bar grown by the [[Hydrothermal synthesis|hydrothermal method]]]]
Because [[grain boundary|grain boundaries]] can have significant effects on the physical and electrical properties of a material, single crystals are of interest to industry, and have important industrial applications. The most notable of these is the use of single crystal [[silicon]] in the [[Fabrication (semiconductor)|fabrication of semiconductors]]. On the [[quantum mechanics|quantum]] scale that [[microprocessor]]s operate on, the presence of grain boundaries would have a significant impact on the functionality of [[field effect transistor]]s by altering local electrical properties. Therefore, microprocessor fabricators have invested heavily in facilities to produce large single crystals of silicon.
Fabrication of single crystals usually involves the building of a crystal layer by layer of atoms. Techniques to produce large single crystals ([[boule (crystal)|boules]]) include slowly drawing a rotating "[[seed crystal]]" in a molten bath of feeder material (as in the [[Czochralski process]] and the [[Bridgeman technique]]). Some [[thin film deposition]] techniques can be used for [[epitaxy]], forming a new layer of material with the same structure on the surface of an existing single crystal.
==Uses==
* Monocrystals of [[silicon]] and other [[semiconductor]]s are important for manufacture of [[integrated circuit]]s.
* Monocrystaline silicon [[photovoltaic cell]]s have superior performance characteristics to chemically identical ''polycrystaline'' solar cells.{{Fact|date=May 2008}}
* Monocrystals of [[sapphire]] and other materials are used for [[laser]]s and [[nonlinear optics]].
* Monocrystals of [[fluorite]] are sometimes used in the objective lenses of [[apochromat]]ic [[refractor|refracting telescopes]].{{Fact|date=May 2008}}
* Monocrystals of metals, especially [[superalloy]]s, are used for their special mechanical properties. [[Turbine]] blades of some [[gas turbine]]s are made of single crystal [[casting|cast]] [[superalloy]].{{Fact|date=May 2008}}
* Monocrystals of copper ([[crystalline copper]]) are used for fine crystalline powders and [[hi tech]] wires.{{Fact|date=May 2008}}
* Monocrystaline [[superconductor]]s have superior performance characteristics to chemically identical ''polycrystaline'' superconductors.{{Fact|date=May 2008}}
==See also==
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* [[Crystal]]
* [[Crystal structure]]
* [[Crystallite]]
* [[Crystallization]] and [[Crystallization (engineering aspects)|engineering aspects]]
* [[Fractional crystallization (chemistry)]]
* [[Recrystallization]]
* [[Seed crystal]]
* [[Wafer (electronics)]]
==References==
* [http://acaschool.iit.edu/lectures04/JLiangXtal.pdf "Small Molecule Crystallization"] ([[PDF]]) at [[Illinois Institute of Technology]] website
[[Category:Crystals]]
[[Category:Semiconductor growth]]
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