Single crystal

{{short description|Material with a continuous, unbroken crystal lattice}} {{more citations needed|date=February 2010}} {{Crystallization}} In materials science, a '''single crystal''' (or '''single-crystal solid''' or '''monocrystalline solid''') is a material in which the crystal lattice of the entire sample is continuous and unbroken to the edges of the sample, with no grain boundaries.<ref name=":0">{{cite web|url=https://reade.com/product/single-crystals/|work=Reade|title ="Reade Advanced Materials – Single Crystals"|access-date=2021-02-28}}</ref> The absence of the defects associated with grain boundaries can give monocrystals unique properties, particularly mechanical, optical and electrical, which can also be anisotropic, depending on the type of crystallographic structure.<ref name=":5" /> These properties, in addition to making some gems precious, are industrially used in technological applications, especially in optics and electronics.<ref>{{Cite web|title=Single Crystals – Alfa Chemistry|url=https://www.alfa-chemistry.com/products/single-crystals-121.htm|access-date=2021-02-28|website=www.alfa-chemistry.com}}</ref>

Because entropic effects favor the presence of some imperfections in the microstructure of solids, such as impurities, inhomogeneous strain and crystallographic defects such as dislocations, perfect single crystals of meaningful size are exceedingly rare in nature.<ref name=":5" /> The necessary laboratory conditions often add to the cost of production. On the other hand, imperfect single crystals can reach enormous sizes in nature: several mineral species such as beryl, gypsum and feldspars are known to have produced crystals several meters across.{{Citation needed|date=July 2024}}

The opposite of a single crystal is an amorphous structure where the atomic position is limited to short-range order only.<ref name=":3">"4.1: Introduction". ''Engineering LibreTexts''. 2019-02-08. Retrieved 2021-02-28.</ref> In between the two extremes exist ''polycrystalline'', which is made up of a number of smaller crystals known as ''crystallites'', and ''paracrystalline'' phases.<ref name=":1">"DoITPoMS – TLP Library Atomic Scale Structure of Materials". ''www.doitpoms.ac.uk''. Retrieved 2021-02-28.</ref> Single crystals will usually have distinctive plane faces and some symmetry, where the angles between the faces will dictate its ideal shape. Gemstones are often single crystals artificially cut along crystallographic planes to take advantage of refractive and reflective properties.<ref name=":1" />

== Production methods ==

Although current methods are extremely sophisticated with modern technology, the origins of crystal growth can be traced back to salt purification by crystallization in 2500 BCE. A more advanced method using an aqueous solution was started in 1600 CE while the melt and vapor methods began around 1850 CE.<ref name=":2">{{cite book |doi=10.1007/978-0-387-46271-4_29 |chapter=Growing Single Crystals |title=Ceramic Materials |year=2007 |pages=507–526 |isbn=978-0-387-46270-7 |s2cid=240461586 }}</ref> thumb|329x329px|Single-crystal growth methods tree diagram Basic crystal growth methods can be separated into four categories based on what they are artificially grown from: melt, solid, vapor, and solution.<ref name=":5" /> Specific techniques to produce large single crystals (aka boules) include the Czochralski process (CZ), floating zone (or zone movement), and the Bridgman technique. Dr. Teal and Dr. Little of Bell Telephone Laboratories were the first to use the Czochralski method to create Ge and Si single crystals.<ref>Teal, G.K. and Little, J.B. (1950) "Growth of germanium single crystals," ''Phys. Rev.'' 78, 647. Teal and Little of Bell Telephone Laboratories were the first to produce single crystals of Ge and Si by the Cz method. Cited in {{cite book |doi=10.1007/978-0-387-46271-4_29 |chapter=Growing Single Crystals |title=Ceramic Materials |year=2007 |pages=507–526 |isbn=978-0-387-46270-7 |s2cid=240461586 }}</ref> Other methods of crystallization may be used, depending on the physical properties of the substance, including hydrothermal synthesis, sublimation, or simply solvent-based crystallization.<ref>{{cite book |doi=10.1016/b978-0-444-63303-3.00026-2 |chapter=Thermal Stress and Dislocations in Bulk Crystal Growth |title=Handbook of Crystal Growth |year=2015 |last1=Miyazaki |first1=Noriyuki |pages=1049–1092 |isbn=978-0-444-63303-3 }}</ref> For example, a modified Kyropoulos method can be used to grow high quality 300 kg sapphire single crystals.<ref name=":7">Zalozhny, Eugene (Jul 13th, 2015). "Monocrystal enables high-volume LED and optical applications with 300-kg KY sapphire crystals". ''LED's Magazine''. Retrieved February 27, 2021.</ref> The Verneuil method, also called the flame-fusion method, was used in the early 1900s to make rubies before CZ.<ref name=":2" /> The diagram on the right illustrates most of the conventional methods. There have been new breakthroughs such as chemical vapor depositions (CVD) along with different variations and tweaks to the existing methods. These are not shown in the diagram.

[[Image:Quartz synthese.jpg|thumb|A single-crystal quartz bar grown by the hydrothermal method]]

In the case of metal single crystals, fabrication techniques also include epitaxy and abnormal grain growth in solids.<ref>{{cite journal |last1=Jin |first1=Sunghwan |last2=Ruoff |first2=Rodney S. |title=Preparation and uses of large area single crystal metal foils |journal=APL Materials |date=1 October 2019 |volume=7 |issue=10 |page=100905 |doi=10.1063/1.5114861 |s2cid=208729868 |doi-access=free |bibcode=2019APLM....7j0905J }}</ref> Epitaxy is used to deposit very thin (micrometer to nanometer scale) layers of the same or different materials on the surface of an existing single crystal.<ref>{{cite journal |last1=Zhang |first1=Kai |last2=Pitner |first2=Xue Bai |last3=Yang |first3=Rui |last4=Nix |first4=William D. |last5=Plummer |first5=James D. |last6=Fan |first6=Jonathan A. |title=Single-crystal metal growth on amorphous insulating substrates |journal=Proceedings of the National Academy of Sciences |date=23 January 2018 |volume=115 |issue=4 |pages=685–689 |doi=10.1073/pnas.1717882115 |pmid=29311332 |pmc=5789947 |doi-access=free |bibcode=2018PNAS..115..685Z }}</ref> Applications of this technique lie in the areas of semiconductor production, with potential uses in other nanotechnological fields and catalysis.<ref>{{Cite web|title=Single Crystal Substrates – Alfa Chemistry|url=https://www.alfa-chemistry.com/products/single-crystal-substrates-123.htm|access-date=2021-03-11|website=www.alfa-chemistry.com}}</ref>

It is extremely difficult to grow single crystals of the polymers. It is mainly because that the polymer chains are of different length and due to the various entropy reasons. However, topochemical reactions are one of the easy methods to get single crystals of the polymer.[https://pubs.rsc.org/en/content/articlelanding/2013/cs/c2cs35343a]

== Applications ==

=== Semiconductor industry ===

One of the most used single crystals is that of silicon in the semiconductor industry. The four main production methods for semiconductor single crystals are from metallic solutions: liquid phase epitaxy (LPE), liquid phase electroepitaxy (LPEE), the traveling heater method (THM), and liquid phase diffusion (LPD).<ref>{{Citation|last1=Dost|first1=Sadik|title=Chapter 1 – INTRODUCTION|date=2007-01-01|url=https://www.sciencedirect.com/science/article/pii/B978044452232050002X|work=Single Crystal Growth of Semiconductors from Metallic Solutions|pages=3–14|editor-last=Dost|editor-first=Sadik|place=Amsterdam|publisher=Elsevier|language=en|doi=10.1016/b978-044452232-0/50002-x|isbn=978-0-444-52232-0|access-date=2021-03-11|last2=Lent|first2=Brian|editor2-last=Lent|editor2-first=Brian|url-access=subscription}}</ref> However, there are many other single crystals besides inorganic single crystals capable semiconducting, including single-crystal organic semiconductors. [[File:Tantalum single crystal and 1cm3 cube.jpg|thumb|A high-purity (99.999 %) tantalum single crystal, made by the floating zone process, some single crystalline fragments of tantalum, and a high-purity (99.99% = 4N) 1 cm3 tantalum cube for comparison.]] Monocrystalline silicon used in the fabrication of semiconductors and photovoltaics is the greatest use of single-crystal technology today.<ref>{{Citation|last=Kearns|first=Joel K.|title=2 – Silicon single crystals|date=2019-01-01|url=https://www.sciencedirect.com/science/article/pii/B9780081020968000021|work=Single Crystals of Electronic Materials|pages=5–56|editor-last=Fornari|editor-first=Roberto|series=Woodhead Publishing Series in Electronic and Optical Materials|publisher=Woodhead Publishing|language=en|doi=10.1016/b978-0-08-102096-8.00002-1|isbn=978-0-08-102096-8|s2cid=139380571 |access-date=2021-03-11|url-access=subscription}}</ref> In photovoltaics, the most efficient crystal structure will yield the highest light-to-electricity conversion.<ref>"CZ-Si Wafers – Nanografi". ''nanografi.com''. Retrieved 2021-02-28.</ref> On the quantum scale that microprocessors operate on, the presence of grain boundaries would have a significant impact on the functionality of field effect transistors by altering local electrical properties.<ref>{{Citation|title=Chapter 3 – The Current Situation in Ultra-Precision Technology – Silicon Single Crystals as an Example|date=2012-01-01|url=https://www.sciencedirect.com/science/article/pii/B978143777859500003X|journal=Advances in CMP Polishing Technologies|pages=15–111|editor-last=Doi|editor-first=Toshiro|place=Oxford|publisher=William Andrew Publishing|language=en|doi=10.1016/b978-1-4377-7859-5.00003-x|isbn=978-1-4377-7859-5|access-date=2021-03-11|editor2-last=Marinescu|editor2-first=Ioan D.|editor3-last=Kurokawa|editor3-first=Syuhei|url-access=subscription}}</ref> Therefore, microprocessor fabricators have invested heavily in facilities to produce large single crystals of silicon. The Czochralski method and floating zone are popular methods for the growth of silicon crystals.<ref>{{cite book |doi=10.1016/B978-0-444-63303-3.00002-X |chapter=Czochralski Growth of Silicon Crystals |title=Handbook of Crystal Growth |year=2015 |last1=Friedrich |first1=Jochen |last2=von Ammon |first2=Wilfried |last3=Müller |first3=Georg |pages=45–104 |isbn=978-0-444-63303-3 }}</ref> thumb|Fluorescence of (9H-carbazol-9-yl)(4-chlorophenyl)methanone single crystal. Other inorganic semiconducting single crystals include GaAs, GaP, GaSb, Ge, InAs, InP, InSb, CdS, CdSe, CdTe, ZnS, ZnSe, and ZnTe. Most of these can also be tuned with various doping for desired properties.<ref name="Semiconductor Single Crystals">{{Cite web|title=Semiconductor Single Crystals|url=https://princetonscientific.com/materials/semiconductor-single-crystals/|access-date=2021-02-08|website=Princeton Scientific|language=en}}</ref> Single-crystal graphene is also highly desired for applications in electronics and optoelectronics with its large carrier mobility and high thermal conductivity, and remains a topic of fervent research.<ref>{{Cite journal|last1=Ma|first1=Teng|last2=Ren|first2=Wencai|last3=Zhang|first3=Xiuyun|last4=Liu|first4=Zhibo|last5=Gao|first5=Yang|last6=Yin|first6=Li-Chang|last7=Ma|first7=Xiu-Liang|last8=Ding|first8=Feng|last9=Cheng|first9=Hui-Ming|date=2013|title=Edge-controlled growth and kinetics of single-crystal graphene domains by chemical vapor deposition|url= |journal=Proceedings of the National Academy of Sciences of the United States of America|volume=110|issue=51|pages=20386–20391|doi=10.1073/pnas.1312802110|jstor=23761563|pmid=24297886|pmc=3870701|bibcode=2013PNAS..11020386M |doi-access=free}}</ref> One of the main challenges has been growing uniform single crystals of bilayer or multilayer graphene over large areas; epitaxial growth and the new CVD (mentioned above) are among the new promising methods under investigation.<ref>{{cite journal |last1=Wang |first1=Meihui |last2=Luo |first2=Da |last3=Wang |first3=Bin |last4=Ruoff |first4=Rodney S. |title=Synthesis of Large-Area Single-Crystal Graphene |journal=Trends in Chemistry |date=January 2021 |volume=3 |issue=1 |pages=15–33 |doi=10.1016/j.trechm.2020.10.009 |s2cid=229501087 |url=https://scholarworks.unist.ac.kr/handle/201301/49856 |doi-access=free }}</ref>

Organic semiconducting single crystals are different from the inorganic crystals. The weak intermolecular bonds mean lower melting temperatures, and higher vapor pressures and greater solubility.<ref>{{cite journal |last1=Yu |first1=Panpan |last2=Zhen |first2=Yonggang |last3=Dong |first3=Huanli |last4=Hu |first4=Wenping |title=Crystal Engineering of Organic Optoelectronic Materials |journal=Chem |date=November 2019 |volume=5 |issue=11 |pages=2814–2853 |doi=10.1016/j.chempr.2019.08.019 |doi-access=free |bibcode=2019Chem....5.2814Y }}</ref> For single crystals to grow, the purity of the material is crucial and the production of organic materials usually require many steps to reach the necessary purity.<ref>{{cite journal |last1=Chou |first1=Li-Hui |last2=Na |first2=Yaena |last3=Park |first3=Chung-Hyoi |last4=Park |first4=Min Soo |last5=Osaka |first5=Itaru |last6=Kim |first6=Felix Sunjoo |last7=Liu |first7=Cheng-Liang |title=Semiconducting small molecule/polymer blends for organic transistors |journal=Polymer |date=March 2020 |volume=191 |article-number=122208 |doi=10.1016/j.polymer.2020.122208 |s2cid=213570529 }}</ref> Extensive research is being done to look for materials that are thermally stable with high charge-carrier mobility. Past discoveries include naphthalene, tetracene, and 9,10-diphenylanthacene (DPA).<ref>{{cite journal |last1=Tripathi |first1=A. K. |last2=Heinrich |first2=M. |last3=Siegrist |first3=T. |last4=Pflaum |first4=J. |title=Growth and Electronic Transport in 9,10-Diphenylanthracene Single Crystals—An Organic Semiconductor of High Electron and Hole Mobility |journal=Advanced Materials |date=17 August 2007 |volume=19 |issue=16 |pages=2097–2101 |doi=10.1002/adma.200602162 |bibcode=2007AdM....19.2097T |s2cid=97631495 }}</ref> Triphenylamine derivatives have shown promise, and recently in 2021, the single-crystal structure of α-phenyl-4′-(diphenylamino)stilbene (TPA) grown using the solution method exhibited even greater potential for semiconductor use with its anisotropic hole transport property.<ref>{{cite journal |last1=Matsuda |first1=Shofu |last2=Ito |first2=Masamichi |last3=Itagaki |first3=Chikara |last4=Imakubo |first4=Tatsuro |last5=Umeda |first5=Minoru |title=Characterization of α-phenyl-4′-(diphenylamino)stilbene single crystal and its anisotropic conductivity |journal=Materials Science and Engineering: B |date=February 2021 |volume=264 |article-number=114949 |doi=10.1016/j.mseb.2020.114949 |doi-access=free }}</ref>

=== Optical application ===

[[Image:KDP crystal.jpg|thumb|A huge KDP, potassium dihydrogen phosphate, 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.|182x182px]]Single crystals have unique physical properties due to being a single grain with molecules in a strict order and no grain boundaries.<ref name=":5" /> This includes optical properties, and single crystals of silicon is also used as optical windows because of its transparency at specific infrared (IR) wavelengths, making it very useful for some instruments.<ref name=":3" />

Sapphires: also known as the alpha phase of aluminium oxide (Al2O3) to scientists, sapphire single crystals are widely used in hi-tech engineering. It can be grown from gaseous, solid, or solution phases.<ref name=":7" /> The diameter of the crystals resulting from the growth method are important when considering electronic uses after. They are used for lasers and nonlinear optics. Some notable uses are as in the window of a biometric fingerprint reader, optical disks for long-term data storage, and X-ray interferometer.<ref name=":5">{{Cite book |last1=Fornari |first1=Roberto |title=Single Crystals of Electronic Materials: Growth and Properties |date=2018 |publisher=Elsevier Science & Technology |isbn=978-0-08-102097-5 |location=San Diego |oclc=1055046791 }}{{pn|date=November 2022}}</ref>

Indium phosphide: these single crystals are particularly appropriate for combining optoelectronics with high-speed electronics in the form of optical fiber with its large-diameter substrates.<ref>{{Cite web|title=Indium Phosphide PICs|url=https://www.neophotonics.com/technology/indium-phosphide-pics/|access-date=2021-03-12|website=100G Optical Components, Coherent, PIC, DWDM|language=en-US}}</ref> Other photonic devices include lasers, photodetectors, avalanche photo diodes, optical modulators and amplifiers, signal processing, and both optoelectronic and photonic integrated circuits.<ref name=":4">{{Cite book |last=Fornari |first=Roberto |title=Single crystals of electronic materials: growth and properties |date=18 September 2018 |publisher=Woodhead |isbn=978-0-08-102097-5 |oclc=1054250691 }}{{pn|date=November 2022}}</ref> thumb|Aluminium oxide crystals Germanium: this was the material in the first transistor invented by Bardeen, Brattain, and Shockley in 1947. It is used in some gamma-ray detectors and infrared optics.<ref>{{cite conference |conference=31st Annual Technical Symposium on Optical and Optoelectronic Applied Sciences and Engineering |location=San Diego, California, United States |last1=Gafni |first1=G. |last2=Azoulay |first2=M. |last3=Shiloh |first3=C. |last4=Noter |first4=Y. |last5=Saya |first5=A. |last6=Galron |first6=H. |last7=Roth |first7=M. |editor-first1=Irving J. |editor-last1=Spiro |title=Large Diameter Germanium Single Crystals For IR Optics |series=Infrared Technology XIII |date=10 November 1987 |volume=0819 |page=96 |doi=10.1117/12.941806 |bibcode=1987SPIE..819...96G |s2cid=136334692 }}</ref> Now it has become the focus of ultrafast electronic devices for its intrinsic carrier mobility.<ref name=":4" />

Arsenide: arsenide III can be combined with various elements such as B, Al, Ga, and In, with the GaAs compound being in high demand for wafers.<ref name=":4" />

Cadmium telluride: CdTe crystals have several applications as substrates for IR imaging, electrooptic devices, and solar cells.<ref>{{cite journal |last1=Belas |first1=E. |last2=Uxa |first2=Š. |last3=Grill |first3=R. |last4=Hlídek |first4=P. |last5=Šedivý |first5=L. |last6=Bugár |first6=M. |title=High temperature optical absorption edge of CdTe single crystal |journal=Journal of Applied Physics |date=14 September 2014 |volume=116 |issue=10 |page=103521 |doi=10.1063/1.4895494 |bibcode=2014JAP...116j3521B }}</ref> By alloying CdTe and ZnTe together room-temperature X-ray and gamma-ray detectors can be made.<ref name=":4" />

=== Electrical conductors === Metals can be produced in single-crystal form and provide a means to understand the ultimate performance of metallic conductors. It is vital for understanding the basic science such as catalytic chemistry, surface physics, electrons, and monochromators.<ref name=":6">{{Cite web|title=Pure Element Single Crystals – Alfa Chemistry|url=https://www.alfa-chemistry.com/products/pure-element-single-crystals-122.htm|access-date=2021-02-28|website=www.alfa-chemistry.com}}</ref> Production of metallic single crystals have the highest quality requirements and are grown, or pulled, in the form of rods.<ref>{{Cite web|title=Scientists blow hot and cold to produce single-crystal metal|url=https://www.materialstoday.com/metals-alloys/news/scientists-produce-singlecrystal-metal/|access-date=2021-03-12|website=Materials Today}}</ref> Certain companies can produce specific geometries, grooves, holes, and reference faces along with varying diameters.<ref name="Semiconductor Single Crystals"/>

Of all the metallic elements, silver and copper have the best conductivity at room temperature, setting the bar for performance.<ref>{{Cite web|title=TIBTECH innovations: Metal properties comparison: electric conductivity, thermal conductivity, density, melting temperature|url=https://www.tibtech.com/conductivite.php?lang=en_US|access-date=2021-03-12|website=www.tibtech.com}}</ref> The size of the market, and vagaries in supply and cost, have provided strong incentives to seek alternatives or find ways to use less of them by improving performance.

The conductivity of commercial conductors is often expressed relative to the International Annealed Copper Standard, according to which the purest copper wire available in 1914 measured around 100%. The purest modern copper wire is a better conductor, measuring over 103% on this scale. The gains are from two sources. First, modern copper is more pure. However, this avenue for improvement seems at an end. Making the copper purer still makes no significant improvement. Second, annealing and other processes have been improved. Annealing reduces the dislocations and other crystal defects which are sources of resistance. But the resulting wires are still polycrystalline. The grain boundaries and remaining crystal defects are responsible for some residual resistance. This can be quantified and better understood by examining single crystals.

Single-crystal copper did prove to have better conductivity than polycrystalline copper.<ref name="Cho">{{cite journal|last=Cho|first=Yong Chan |author2=Seunghun Lee |author3=Muhammad Ajmal |author4=Won-Kyung Kim |author5=Chae Ryong Cho |author6=Se-Young Jeong |author7=Jeung Hun Park |author8=Sang Eon Park |author9=Sungkyun Park |author10=Hyuk-Kyu Pak |author11=Hyoung Chan Kim |title=Copper Better than Silver: Electrical Resistivity of the Grain-Free Single-Crystal Copper Wire|journal=Crystal Growth & Design|date= March 22, 2010|volume=10|issue=6 |pages=2780–2784|doi=10.1021/cg1003808}}</ref> {| {{Table|class=floatright}} |+ Electrical resistivity ρ for silver (Ag) / copper (Cu) materials at room temperature (293 K) <ref name="Kim">{{cite journal |author1=Ji Young Kim |author2=Min-Wook Oh |author3=Seunghun Lee |author4=Yong Chan Cho |author5=Jang-Hee Yoon |author6=Geun Woo Lee |author7=Chae-Ryong Cho |author8=Chul Hong Park |author9=Se-Young Jeong |title=Abnormal drop in electrical resistivity with impurity doping of single-crystal Ag|journal=Scientific Reports |date=June 26, 2014|volume=4|page=5450|doi=10.1038/srep05450|pmid=24965478 |pmc=4071311|bibcode=2014NatSR...4E5450K}}</ref> |- ! Material !! ρ (μΩ∙cm) !! IACS<ref>{{cite web |url=https://www.nde-ed.org/GeneralResources/IACS/IACS.htm |title= The International Annealed Copper Standard|author= |date=n.d. |website=Nondestructive Testing Resource Center |publisher=The Collaboration for NDT Education, Iowa State University |access-date=November 14, 2016}}</ref> |- | Single-crystal Ag, doped with 3 mol% Cu || 1.35 || 127% |- | Single-crystal Cu, further processed<ref>{{cite journal |author=Muhammad Ajmal |author2=Seunghun Lee |author3=Yong Chan Cho |author4=Su Jae Kim |author5=Sang Eon Park |author6=Chae Ryong Choa |author7=Se-Young Jeong |title=Fabrication of the best conductor from single-crystal copper and the contribution of grain boundaries to the Debye temperature|journal=CrystEngComm |date= 2012|volume=14|issue=4 |pages=1463–1467|doi= 10.1039/C1CE06026K}}</ref> || 1.472 || 117.1% |- | Single-crystal Ag || 1.49 || 115.4% |- | Single-crystal Cu || 1.52 || 113.4% |- | High-purity Ag wire (polycrystalline) || 1.59 || 108% |- | High-purity Cu wire (polycrystalline) || 1.67 || ˃ 103% |} However, the single-crystal copper not only became a better conductor than high purity polycrystalline silver, but with prescribed heat and pressure treatment could surpass even single-crystal silver. Although impurities are usually bad for conductivity, a silver single crystal with a small amount of copper substitutions proved to be the best. As of 2009, no single-crystal copper is manufactured on a large scale industrially, but methods of producing very large individual crystal sizes for copper conductors are exploited for high performance electrical applications. These can be considered meta-single crystals with only a few crystals per meter of length. thumb|232x232px|Pigtail from single-crystal blade casting

=== Single-crystal turbine blades ===

Whilst the absence of grain boundaries decreases yield strength, this is offset by a reduction in thermal creep, making single-crystal solids ideal for high temperature, close tolerance part applications, such as turbine blades.<ref name="spt">Spittle, Peter. [http://users.encs.concordia.ca/~kadem/Rolls%20Royce.pdf "Gas turbine technology"] ''Rolls-Royce plc'', 2003. Retrieved: 21 July 2012.</ref><ref name="turb">[http://www.memagazine.org/backissues/membersonly/feb06/features/crjewels/crjewels.html Crown jewels – These crystals are the gems of turbine efficiency] {{webarchive|url=https://web.archive.org/web/20100325003415/http://www.memagazine.org/backissues/membersonly/feb06/features/crjewels/crjewels.html|date=2010-03-25}} Article on single-crystal turbine blades ''memagazine.com''</ref> Researcher Barry Piearcey found that a right-angle bend at the casting mold would decrease the number of columnar crystals and later, Pratt & Whitney scientist, Tony Giamei, used this to start the blade's single-crystal structure.<ref>{{Cite web |date=2017-02-06 |title=Each Blade a Single Crystal |url=https://www.americanscientist.org/article/each-blade-a-single-crystal |access-date=2021-02-08 |website=American Scientist |language=en}}</ref><ref>{{Cite web |title=Tony in the Sky with Diamonds « Yale62.org |url=https://yale1962.org/speakout/?p=1568 |access-date=2026-05-12 |website=yale1962.org}}</ref>

== In research ==

Single crystals are essential in research especially condensed-matter physics and all aspects of materials science such as surface science.<ref name=":5" /> The detailed study of the crystal structure of a material by techniques such as Bragg diffraction and helium atom scattering is easier with single crystals because it is possible to study directional dependence of various properties and compare with theoretical predictions.<ref>{{Cite web|title=Silver Single Crystal|url=https://www.materialshub.com/material/silver-single-crystal-2/|access-date=2021-03-12|website=Materials Hub|language=en-GB}}</ref> Furthermore, macroscopically averaging techniques such as angle-resolved photoemission spectroscopy or low-energy electron diffraction are only possible or meaningful on surfaces of single crystals.<ref>{{Cite journal|last1=Wang|first1=Ke|last2=Ecker|first2=Ben|last3=Gao|first3=Yongli|date=September 2020|title=Angle-Resolved Photoemission Study on the Band Structure of Organic Single Crystals|journal=Crystals|language=en|volume=10|issue=9|page=773|doi=10.3390/cryst10090773|doi-access=free}}</ref><ref>{{Cite web|date=2015-02-11|title=6.2: Low Energy Electron Diffraction (LEED)|url=https://chem.libretexts.org/Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Book%3A_Surface_Science_(Nix)/06%3A_Overlayer_Structures_and_Surface_Diffraction/6.02%3A_Low_Energy_Electron_Diffraction_(LEED)|access-date=2021-03-12|website=Chemistry LibreTexts|language=en}}</ref> Single crystals are further well-suited to investigate material-inherent properties using surface-sensitive techniques, as they are much less affected by preparation methods than thin films.<ref>{{cite journal |last1=Kammlander |first1=Birgit |last2=García-Fernández |first2=Alberto |last3=Svanström |first3=Sebastian |last4=Giangrisostomi |first4=Erika |last5=Ovsyannikov |first5=Ruslan |last6=Rensmo |first6=Håkan |last7=Cappel |first7=Ute B |title=Investigating charge dynamics at lead halide perovskite single crystal surfaces |journal=Journal of Physics: Energy |date=30 April 2025 |volume=7 |issue=2 |page=025005 |doi=10.1088/2515-7655/ada63a |url=https://iopscience.iop.org/article/10.1088/2515-7655/ada63a |issn=2515-7655}}</ref> In superconductivity there have been cases of materials where superconductivity is only seen in single-crystalline specimen.<ref>{{cite journal |last1=Chen |first1=Jiasheng |last2=Gamża |first2=Monika B. |last3=Banda |first3=Jacintha |last4=Murphy |first4=Keiron |last5=Tarrant |first5=James |last6=Brando |first6=Manuel |last7=Grosche |first7=F. Malte |title=Unconventional Bulk Superconductivity in YFe 2 Ge 2 Single Crystals |journal=Physical Review Letters |date=30 November 2020 |volume=125 |issue=23 |article-number=237002 |doi=10.1103/PhysRevLett.125.237002 |pmid=33337220 |s2cid=220793188 |url=https://www.repository.cam.ac.uk/handle/1810/321630 |arxiv=2007.13584 }}</ref> They may be grown for this purpose, even when the material is otherwise only needed in polycrystalline form.

As such, numerous new materials are being studied in their single-crystal form. The young field of metal-organic-frameworks (MOFs) is one of many which qualify to have single crystals. In January 2021 Dr. Dong and Dr. Feng demonstrated how polycyclic aromatic ligands can be optimized to produce large 2D MOF single crystals of sizes up to 200 μm. This could mean scientists can fabricate single-crystal devices and determine intrinsic electrical conductivity and charge transport mechanism.<ref>{{cite journal |last1=Dong |first1=Renhao |last2=Feng |first2=Xinliang |title=Making large single crystals of 2D MOFs |journal=Nature Materials |date=February 2021 |volume=20 |issue=2 |pages=122–123 |doi=10.1038/s41563-020-00912-1 |pmid=33504985 |bibcode=2021NatMa..20..122D |s2cid=231745364 }}</ref>

The field of photodriven transformation can also be involved with single crystals with something called single-crystal-to-single-crystal (SCSC) transformations. These provide direct observation of molecular movement and understanding of mechanistic details.<ref>{{cite journal |last1=Huang |first1=Sheng-Li |last2=Hor |first2=T.S. Andy |last3=Jin |first3=Guo-Xin |title=Photodriven single-crystal-to-single-crystal transformation |journal=Coordination Chemistry Reviews |date=September 2017 |volume=346 |pages=112–122 |doi=10.1016/j.ccr.2016.06.009 |doi-access=free }}</ref> This photoswitching behavior has also been observed in cutting-edge research on intrinsically non-photo-responsive mononuclear lanthanide single-molecule-magnets (SMM).<ref>{{cite journal |last1=Hojorat |first1=Maher |last2=Al Sabea |first2=Hassan |last3=Norel |first3=Lucie |last4=Bernot |first4=Kevin |last5=Roisnel |first5=Thierry |last6=Gendron |first6=Frederic |last7=Guennic |first7=Boris Le |last8=Trzop |first8=Elzbieta |last9=Collet |first9=Eric |last10=Long |first10=Jeffrey R. |last11=Rigaut |first11=Stéphane |title=Hysteresis Photomodulation via Single-Crystal-to-Single-Crystal Isomerization of a Photochromic Chain of Dysprosium Single-Molecule Magnets |journal=Journal of the American Chemical Society |date=15 January 2020 |volume=142 |issue=2 |pages=931–936 |doi=10.1021/jacs.9b10584 |pmid=31880442 |s2cid=209490756 |url=https://hal.archives-ouvertes.fr/hal-02432642/file/Hojora%20et%20al-2020-Hysteresis%20Photomodulation%20via%20Single-Crystal-to-Single-Crystal%20Isomerization.pdf }}</ref>

== Post-processing of single crystals ==

Single crystals used in semiconductors, optics, and ceramics must often be machined or sliced into wafers, prisms, or other precision components. Due to their hardness and brittleness, these materials require specialized cutting techniques that minimize subsurface damage and kerf loss.

'''Inner diameter (ID) sawing''' is a conventional method, where a thin circular blade embedded with diamond abrasives slices through the crystal. It provides good dimensional accuracy but is limited by blade rigidity and maximum cutting depth.<ref>{{Cite AV media |url=https://www.youtube.com/watch?v=1vCjxOgSL-w |title=what is id saw |date=2023-08-29 |last=Vimfun Optical Sawing |access-date=2025-11-11 |via=YouTube}}</ref>

'''Multi-wire sawing''', which uses long diamond wires moving reciprocally, became the mainstream process for silicon and sapphire wafers. It allows simultaneous slicing of multiple wafers from a single ingot, but the back-and-forth motion can cause vibration and wire wear, leading to surface marks and variable tension.<ref>{{Cite web |date=2024-01-29 |title=3 Types Of Multi Wire Cutting Machines You Need To Know. |url=https://www.endlesswiresaw.com/3-types-of-multi-wire-cutting-machines/ |access-date=2025-11-11 |language=en}}</ref>

'''Endless diamond wire sawing''' (loop-type) is a more recent approach. The wire forms a continuous closed loop, typically several meters in length, running in a single direction at high linear speeds (around 60–80 m/s). Because the wire tension and motion are steady, the process can achieve smoother surfaces, smaller kerf widths, and longer tool life. It has been applied to slicing hard and brittle single-crystal materials such as silicon, sapphire, and advanced ceramics.<ref>{{Cite web |title=Cutting-Edge Innovations: The Endless Diamond Wire Podcast |url=http://www.youtube.com/playlist?list=PLmKC_-zBCT5mha7PLrIRIR3WwRdp3WwQp |access-date=2025-11-11 |website=YouTube |language=en}}</ref>

Other techniques, including '''laser slicing''', '''ultrasonic machining''', and '''ion-beam or chemical-mechanical polishing''', are used for finishing or micro-fabrication stages, especially when optical-grade surface quality is required.

== References ==

== Further reading ==

* [https://web.archive.org/web/20160303181456/http://acaschool.iit.edu/lectures04/JLiangXtal.pdf "Small Molecule Crystallization"] (PDF) at Illinois Institute of Technology website

{{DEFAULTSORT:Single Crystal}} Category:Crystals