Se kilde til Kvanteø

{{Kvantemekanik}}
[[Fil:Quantum Dots with emission maxima in a 10-nm step are being produced at PlasmaChem in a kg scale.jpg|thumb|Kvanteøer får forskellige farve under [[UV-lys]] afhængig af størrelsen.]]
En '''kvanteø''', '''kvanteprik''', '''halvledernanokrystal''' eller et '''kvantepunkt''' ('''QD''' fra eng. ''quantum dot'') er et [[halvleder]]krystal indeholdt i en [[diameter]] på nogle få nanometer. Pga. sin lille størrelse opfører en kvanteø sig som en [[potentialbrønd]]. En potentialbrønd fastholder [[elektron]]er i 3 [[dimension]]er i et område med en størrelse, som svarer til elektronens [[de Broglie-bølgelængde]], hvilket er nogle få nanometer i en halvleder. Sammenlign det med [[kvanteledning]]er (fastholder i 2D) og [[kvantebrønd]]e (fastholder i 1D).

Pga. fastholdelsen er elektronens energiniveauer kvantiserede, ligesom i et [[atom]]. Det er grunden til at kvanteøer kaldes "'''kunstige atomer'''". Energiniveauerne kan styres ved at størrelsen og formen på kvanteøen ændres.

== Anvendelser ==
Pga. kvanteøers halv-nul dimensionelle udstrækning har de et skarpere {{illsup|en|tilstandstæthed|density of states}} end højere-dimensionelle strukturer. Resultatet er, at kvanteøer har uovertrufne transport- og optiske egenskaber og der bliver forsket i at deres anvendelse i f.eks. højeffektive [[lysdiode]]r, højeffektiv [[UVA]] til hvidt lys [[fluorescens]], [[Optisk fiber|fiberoptisk]] lysregenerering, [[diodelaser]]ere og detektorer.<ref>Fujitsu (10. september 2004). ''[http://www.fujitsu.com/news/pr/archives/month/2004/20040910-01.html Fujitsu, University of Tokyo Develop World's First 10Gbit/s Quantum Dot Laser Featuring Breakthrough Temperature-Independent Output]''. Press Release. </ref>
<ref>{{Cite web |url=http://evidenttech.com/applications/quantum-dot-photonics.php |title=Webarchivebackup: evidenttech.com: Quantum Dots and Non-Linear Optical Capabilities: Quantum Dots and Photonics to Improve Information Technology |access-date= 7. april 2007 |archive-date= 7. april 2007 |archive-url=https://web.archive.org/web/20070407011652/http://evidenttech.com/applications/quantum-dot-photonics.php |url-status=dead }}</ref>
<ref>[http://www.fujitsu.com/global/news/pr/archives/month/2005/20050304-01.html Fujitsu Develops World's First Semiconductor Optical Amplifier with Signal Waveform Re-shaping Function at 40Gbps. Uses quantum dots to eliminate waveform degradation and significantly reduce noise]</ref>
<ref>[http://www.llnl.gov/str/Lee.html Mighty Small Dots] {{Webarchive|url=https://web.archive.org/web/20050630073502/http://www.llnl.gov/str/Lee.html |date=30. juni 2005 }} Citat: "..."For years," says Lee, "scientists have been trying to make silicon emit light efficiently and in the visible range. This has been one of the holy grails of science."...What makes our dots unique is that their luminescence can be tuned to any wavelength over a broad spectral range and be stable under ambient conditions. No one else has done this. We also believe we understand the underlying physics..."</ref>
<ref>[http://www.sciencedaily.com/releases/2004/06/040623083024.htm 2004-06-23, Sciencedaily: Wireless Nanocrystals Efficiently Radiate Visible Light] Citat: "...The efficiency of the energy transfer from the quantum well to the nanocrystals was approximately 55 percent – although in theory nearly 100 percent transfer of the energy is possible and might be achieved with further tweaking...The work is another step in creating more efficient white-light-emitting diodes..."</ref>
<ref>[http://www.sciencedaily.com/releases/2005/10/051021123902.htm 2005-10-21, sciencedaily: Quantum Dots That Produce White Light Could Be The Light Bulb's Successor] Citat: "...The report of their discovery, which happened by accident, appears in the communication “White-light Emission from Magic-Sized Cadmium Selenide Nanocrystals”...As a result, the light produced by the quantum dots looks more nearly like the “full spectrum”...either 33 or 34 pairs of atoms, which happens to be a “magic size”...The quantum dots were supposed to emit blue light, but instead they were giving off a beautiful white glow..."</ref>
<ref>[http://www.sciencedaily.com/upi/index.php?feed=Science&article=UPI-1-20070925-13355000-bc-us-quantumdots.xml Sept. 25, Science Daily: Quantum dots are made brighter] {{Webarchive|url=https://web.archive.org/web/20071005234857/http://www.sciencedaily.com/upi/index.php?feed=Science&article=UPI-1-20070925-13355000-bc-us-quantumdots.xml |date= 5. oktober 2007 }} Citat: "...While the researchers report an enhancement of fluorescence intensity by a factor of up to 108 compared with quantum dots on an unpatterned surface, Cunningham said more recent, but unpublished, work has exceeded a factor of 550..."</ref>

En kvanteø er den aktive del i en [[Single electron transistor|enkelt elektron transistor]].

[[Kvantemekanisk sammenfiltring]] af flere kvanteøer (i rollen som [[qubit]]s) er en af de mest håbefulde kandidater til faststof [[kvantecomputer]]e.

Kvanteøer kan sandsynligvis anvendes til fremstilling af [[solcelle]]r med en virkningsgrad på 65% ifølge (May 2005, ''American Chemical Society's Nano Letters Journal''), hvilket er mere end dobbelt så meget som dagens bedste masseproducerede solceller.
<ref>[https://phys.org/news/2005-05-quantum-dot-materials-boost-electrical.html May 23, 2005, physorg: Quantum Dot Materials Can Reduce Heat, Boost Electrical Output], [https://web.archive.org/web/20231004173220/https://phys.org/news/2005-05-quantum-dot-materials-boost-electrical.html backup] Citat: "..."We have shown that solar cells based on quantum dots theoretically could convert more than 65 percent of the sun's energy into electricity, approximately doubling the efficiency of solar cells," Nozik said..."</ref>

== Fabrikation og størrelse ==
I halvledere er kvanteøer små områder af et materiale "begravet" i et andet materiale med et større [[båndgab]].

Kvanteøen er i en størrelsesorden på elektronens [[de Broglie-bølgelængde]] og den er ved stuetemperatur:

<math>\frac{h}{\sqrt{2 m_e E}}</math>

Her gælder der:

<math>E = k_b \cdot T = 1,38 10^{-23} \frac{J}{K}  \cdot 300K </math>

Det giver så:

<math>\frac{6,626 10^{-34} Js}{\sqrt{2\cdot 9,109 10^{-31} kg\cdot 1,38 10^{-23} \frac{J}{K}  \cdot 300K}} \approx 7,6 nm</math>

== Nobelpris i kemi ==
I 2023 modtog [[Moungi G. Bawendi]], [[Louis E. Brus]], og [[Aleksej Jekimov|Aleksej I. Jekimov]] [[Nobelprisen]] i kemi for deres henholdsvis opdagelse, og syntese af kvanteø.<ref>[https://www.nobelprize.org/prizes/chemistry/2023/press-release/ Press release: The Nobel Prize in Chemistry 2023 - NobelPrize.org<!-- Botgenereret titel -->]</ref>

== Kilder ==
{{reflist}}
* Michalet, X. & Pinaud, F. F. & Bentolila, L. A. & Tsay, J. M. & Doose, S. & Li, J. J. & Sundaresan, G. & Wu, A. M. & Gambhir, S. S. & Weiss, S. (2005, January 28). [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=15681376 Quantum dots for live cells, in vivo imaging, and diagnostics.] In ''Science,'' 307, 538 – 544.
* W. E. Buhro and V. L. Colvin, [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=12612665 Semiconductor nanocrystals: Shape matters], ''Nat. Mater.,'' 2003, 2, 138 139.

== Se også ==
* [[kvantetråd]]
* [[supergitter]]
* [[kvanterør]]
* [[Fotonisk krystal]]

== Eksterne henvisninger ==
* [http://www.inano.dk/sw237.asp inano.dk: Halvleder-kvanteøer] {{Webarchive|url=https://web.archive.org/web/20050211164807/http://www.inano.dk/sw237.asp |date=11. februar 2005 }}
* [http://www.evidenttech.com/qdot-definition/quantum-dot-introduction.php How quantum dots works – flash animations] {{Webarchive|url=https://web.archive.org/web/20150120021952/http://www.evidenttech.com/qdot-definition/quantum-dot-introduction.php |date=20. januar 2015 }}
* [http://www.sciencedaily.com/releases/2005/06/050616060710.htm 2005-06-17, Sciencedaily: A New Model Of Quantum Dots: Rethinking The Electronics]

{{Autoritetsdata}}

[[Kategori:Nanoteknologi]]
[[Kategori:Halvlederstrukturer]]
[[Kategori:Fremspirende teknologi]]