Single crystal: Difference between revisions - Wikipedia

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In [[materials science]], a '''single-crystal''', 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 boundary|grain boundaries]].<ref name=":0">RIWD. "Reade Advanced Materials -– Single Crystals". ''www.reade.com''. Retrieved 2021-02-28.</ref> The absence of the [[crystallographic defect|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 [[crystallography|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>"Single Crystals -– Alfa Chemistry". ''www.alfa-chemistry.com''. Retrieved 2021-02-28.</ref>

Because [[entropy|entropic]] effects favor the presence of some imperfections in the microstructure of solids, such as [[impurity|impurities]], inhomogeneous strain and crystallographic defects such as [[dislocation]]s, 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 [[feldspar]]s are known to have produced crystals several meters across.<ref name=":6">"Pure Element Single Crystals -– Alfa Chemistry". ''www.alfa-chemistry.com''. Retrieved 2021-02-28.</ref><ref name=":0" />

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 ''[[crystallite]]s'', 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">(2007) Growing Single Crystals. In: Ceramic Materials. Springer, New York, NY. {{doi|10.1007/978-0-387-46271-4_29}}</ref>

[[File:Single Crystal Growth Methods Flow Chart .png|thumb|329x329px|Single-crystal ~~Crystal~~growth ~~Growth~~methods ~~Methods~~tree ~~Tree Diagram~~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 [[Boule (crystal)|boules]]) include the [[Czochralski process|Czochralski process (CZ)]], Floating zone (or Zone Movement), and the [[Bridgman–Stockbarger technique|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.</ref> Other methods of crystallization may be used, depending on the physical properties of the substance, including [[hydrothermal synthesis]], [[Sublimation (chemistry)|sublimation]], or simply [[Recrystallization (chemistry)|solvent-based crystallization]].<ref>Miyazaki, Noriyuki (2015-01-01), Rudolph, Peter (ed.), "26 -– Thermal Stress and Dislocations in Bulk Crystal Growth", ''Handbook of Crystal Growth (Second Edition)'', Handbook of Crystal Growth, Boston: Elsevier, pp. 1049–1092, {{doi|10.1016/b978-0-444-63303-3.00026-2}}, {{ISBN|978-0-444-63303-3}}, retrieved 2021-02-28</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 synthesis|hydrothermal method]]]]

In the case of metal single crystals, fabrication techniques also include [[epitaxy]] and abnormal grain growth in solids.<ref>Jin, Sunghwan; Ruoff, Rodney S. (2019-10-01). "Preparation and uses of large area single -crystal metal foils". ''APL Materials''. '''7''' (10): 100905. {{doi|10.1063/1.5114861}}.</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>Zhang, Kai; Pitner, Xue Bai; Yang, Rui; Nix, William D.; Plummer, James D.; Fan, Jonathan A. (2018). "Single-crystal metal growth on amorphous insulating substrates". ''Proceedings of the National Academy of Sciences of the United States of America''. '''115''' (4): 685–689. {{doi|10.2307/26506454}}. {{issn|0027-8424}}.</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>

== Applications ==

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=== 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}}</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 [[Zone melting|floating zone process]], some single crystalline fragments of tantalum, as well as a high purity (99.99 % = 4N) 1 cm3 tantalum cube for comparison. This photo was taken by Alchemist-hp.]]

[[Monocrystalline silicon]] used in the [[Fabrication (semiconductor)|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|access-date=2021-03-11}}</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 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.<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}}</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>Czochralski Growth of Silicon Crystals Jochen Friedrich 2 , Wilfried von Ammon 1 , Georg Müller 3 3

''Handbook of Crystal Growth : Bulk Crystal Growth'', edited by Peter Rudolph, Elsevier, 2014. ''ProQuest Ebook Central'', <nowiki>http://ebookcentral.proquest.com/lib/dartmouth-ebooks/detail.action?docID=1840493</nowiki>.</ref>

Other [[Inorganic compound|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 (semiconductor)|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|issn=0027-8424|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.|date=2021-01-01|title=Synthesis of Large-Area Single-Crystal Graphene|url=https://www.cell.com/trends/chemistry/abstract/S2589-5974(20)30269-0|journal=Trends in Chemistry|language=English|volume=3|issue=1|pages=15–33|doi=10.1016/j.trechm.2020.10.009|s2cid=229501087|issn=2589-7209}}</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|date=2019-11-14|title=Crystal Engineering of Organic Optoelectronic Materials|journal=Chem|language=English|volume=5|issue=11|pages=2814–2853|doi=10.1016/j.chempr.2019.08.019|issn=2451-9294|doi-access=free}}</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|date=2020-03-16|title=Semiconducting small molecule/polymer blends for organic transistors|url=https://www.sciencedirect.com/science/article/pii/S0032386120300525|journal=Polymer|language=en|volume=191|pages=122208|doi=10.1016/j.polymer.2020.122208|s2cid=213570529|issn=0032-3861}}</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.|date=2007-08-17|title=Growth and Electronic Transport in 9,10-Diphenylanthracene Single Crystals—An Organic Semiconductor of High Electron and Hole Mobility|url=http://doi.wiley.com/10.1002/adma.200602162|journal=Advanced Materials|language=en|volume=19|issue=16|pages=2097–2101|doi=10.1002/adma.200602162}}</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 anistropic hole transport property.<ref>{{Cite journal|date=2021-02-01|title=Characterization of α-phenyl-4′-(diphenylamino)stilbene single crystal and its anisotropic conductivity|journal=Materials Science and Engineering: B|language=en|volume=264|pages=114949|doi=10.1016/j.mseb.2020.114949|issn=0921-5107|doi-access=free|last1=Matsuda|first1=Shofu|last2=Ito|first2=Masamichi|last3=Itagaki|first3=Chikara|last4=Imakubo|first4=Tatsuro|last5=Umeda|first5=Minoru}}</ref>

=== Optical application ===

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=== Electrical conductors ===

Metals can surprisingly 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 [[monochromator]]s.<ref name=":6" /> 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 [[Electrical conductivity|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.

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| Single-crystal Cu || 1.52 || 113.4%

| High -purity Ag wire (polycrystalline) || 1.59 || 108%

| High -purity Cu wire (polycrystalline) || 1.67 || ~~˃103~~˃ 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.

[[File:Pigtail from Single Crystal Blade Casting shown with Kennedy Half Dollar for size comparison.jpg|thumb|232x232px|Pigtail from ~~Single~~single-crystal ~~Crystal~~blade ~~Blade Casting~~casting]]

=== Single-crystal turbine blades ===

Another application of single -crystal solids is in materials science in the production of high strength materials with low thermal [[creep (deformation)|creep]], 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> Here, the absence of grain boundaries actually gives a decrease in yield strength, but more importantly decreases the amount of creep which is critical for high temperature, close tolerance part applications.<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, scientist Giamei used this to start the single-crystal structure of the turbine blade.<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>

== 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 <!-- Powder diffraction is actually easier and more efficient

- If you could find a source to cite, please add! -->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|pages=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> 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|date=2020-11-30|title=<nowiki>Unconventional Bulk Superconductivity in ${\mathrm{YFe}}_{2}{\mathrm{Ge}}_{2}$ Single Crystals</nowiki>|url=https://link.aps.org/doi/10.1103/PhysRevLett.125.237002|journal=Physical Review Letters|volume=125|issue=23|pages=237002|doi=10.1103/PhysRevLett.125.237002|pmid=33337220|s2cid=220793188}}</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 (MOF's) 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>Dong, Renhao; Feng, Xinliang (2021-02). "Making large single crystals of 2D MOFs". ''Nature Materials''. '''20''' (2): 122–123. {{doi|10.1038/s41563-020-00912-1}}. {{issn|1476-4660}}.</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>Huang, Sheng-Li; Hor, T. S. Andy; Jin, Guo-Xin (2017-09-01). "Photodriven single-crystal-to-single-crystal transformation". ''Coordination Chemistry Reviews''. SI: 42 iccc, Brest-- by invitation. '''346''': 112–122. {{doi|10.1016/j.ccr.2016.06.009}}. {{issn|0010-8545}}.</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|date=2020-01-15|title=Hysteresis Photomodulation via Single-Crystal-to-Single-Crystal Isomerization of a Photochromic Chain of Dysprosium Single-Molecule Magnets|url=https://pubs.acs.org/doi/10.1021/jacs.9b10584|journal=Journal of the American Chemical Society|language=en|volume=142|issue=2|pages=931–936|doi=10.1021/jacs.9b10584|pmid=31880442|issn=0002-7863}}</ref>