Kwa zaka zambiri, asayansi ochokera padziko lonse lapansi akhala akuchita zinthu ziwiri - kupanga ndi kukonza. Ndipo nthawi zina sizidziwika kuti ndi iti mwa izi yomwe ili yovuta kwambiri. Mwachitsanzo, taganizirani ma LED wamba, omwe amawoneka ngati osavuta komanso wamba kwa ife kotero kuti sitiwalabadira. Koma ngati muwonjezera ma excitons, pinch ya polaritons ndi tungsten disulfide kuti mulawe, ma LED sadzakhalanso prosaic. Mawu onsewa abstruse ndi mayina a zigawo zachilendo kwambiri, kuphatikiza komwe kunalola asayansi ochokera ku City College of New York kupanga dongosolo latsopano lomwe lingathe kufalitsa uthenga mofulumira kwambiri pogwiritsa ntchito kuwala. Kukula kumeneku kudzathandiza kukonza ukadaulo wa Li-Fi. Kodi zosakaniza zaukadaulo watsopano zomwe zidagwiritsidwa ntchito ndi chiyani, njira ya "mbale" iyi ndi chiyani ndipo mphamvu ya LED yatsopano ya exciton-polariton ndi yotani? Lipoti la asayansi litiuza za izi. Pitani.
Maziko ofufuza
Ngati chirichonse chiri chophweka kwa liwu limodzi, ndiye kuti teknolojiyi ndi yopepuka komanso zonse zogwirizana nazo. Choyamba, ma polaritons, omwe amatuluka pamene photons amagwirizana ndi zokondweretsa zapakati (phononi, excitons, plasmons, magnons, etc.). Kachiwiri, ma excitons ndi chisangalalo chamagetsi mu dielectric, semiconductor kapena chitsulo, kusuntha kudzera mu kristalo ndipo sichimalumikizidwa ndi kusamutsa kwamagetsi ndi misa.
Ndikofunika kuzindikira kuti quasiparticles amakonda kwambiri kuzizira; ntchito yawo ikhoza kuwonedwa kokha pa kutentha kotsika kwambiri, komwe kumalepheretsa kwambiri ntchito yawo yothandiza. Koma zimenezo zinali kale. Mu ntchitoyi, asayansi adatha kuthana ndi kuchepa kwa kutentha ndikugwiritsa ntchito kutentha kwa chipinda.
Mbali yaikulu ya polaritons ndi luso lomanga ma photon kwa wina ndi mzake. Mafotoni omwe akuwombana ndi maatomu a rubidium amakhala olemera. Pakuwombana kangapo, ma photon amadumpha wina ndi mzake, koma nthawi zambiri amapanga awiriawiri ndi katatu, pamene akutaya chigawo cha atomiki choimiridwa ndi atomu ya rubidium.
Koma kuti achite chinachake ndi kuwala, chiyenera kugwidwa. Pachifukwa ichi, resonator ya kuwala imafunika, yomwe ndi kuphatikiza kwa zinthu zowunikira zomwe zimapanga kuwala koyima.
Mu kafukufukuyu, ma quasiparticles achilendo kwambiri, ma exciton-polaritons, omwe amapangidwa chifukwa cha kulumikizana mwamphamvu kwa ma excitons ndi ma photon omwe amatsekeredwa mumtambo wamagetsi, amagwira ntchito yofunika kwambiri.
Komabe, izi sizokwanira, chifukwa maziko akuthupi ndi ofunikira, titero kunena kwake. Ndipo ndani, ngati si transition metal dichalcogenide (TDM), adzachita bwino kuposa ena. Kunena zowona, monolayer wa WS2 (tungsten disulfide) idagwiritsidwa ntchito ngati zinthu zotulutsa, zomwe zimakhala ndi mphamvu zomangirira za exciton, zomwe zidakhala imodzi mwazofunikira pakusankha maziko azinthu.
Kuphatikizana kwa zinthu zonse zomwe tafotokozazi zidapangitsa kuti pakhale kotheka kupanga polarton LED yoyendetsedwa ndi magetsi yomwe imagwira ntchito kutentha.
Kuti mugwiritse ntchito chipangizochi, WS2 monolayer ili pakati pa zotchinga zowonda za hexagonal boron nitride (hBN) zokhala ndi zigawo za graphene zomwe zimakhala ngati maelekitirodi.
Zotsatira za kafukufuku
WS2, pokhala transition metal dichalcogenide, ndi chinthu chochepa kwambiri cha atomiki van der Waals (vdW). Izi zimasonyeza mphamvu yake yapadera ya magetsi, kuwala, makina ndi kutentha.
Kuphatikiza ndi zida zina za vdW, monga graphene (monga kondakitala) ndi hexagonal boron nitride (hBN, monga insulator), zida zosiyanasiyana zoyendetsedwa ndi magetsi zoyendetsedwa ndi semiconductor, zomwe zimaphatikizapo ma LED, zitha kuzindikirika. Kuphatikizika kofananira kwa zida za van der Waals ndi ma polaritoni kudachitika kale, monga momwe ofufuzawo amanenera mosapita m'mbali. Komabe, m'zolemba zam'mbuyomu, machitidwe otsatilawo anali ovuta komanso opanda ungwiro, ndipo sanaulule mphamvu zonse za zigawozo.
Limodzi mwa malingaliro omwe adalimbikitsidwa ndi omwe adatsogolera anali kugwiritsa ntchito nsanja yazinthu ziwiri. Pankhaniyi, ndizotheka kugwiritsa ntchito zida zokhala ndi zigawo zoonda kwambiri za atomiki zomwe zitha kuphatikizidwa ndi zida zina za vdW zomwe zimagwira ntchito ngati zolumikizirana (graphene) ndi zotchinga (hBN). Kuphatikiza apo, mawonekedwe awiriwa amapangitsa kuti azitha kuphatikiza ma LED a polariton ndi zida za vdW zokhala ndi maginito achilendo, superconductivity yamphamvu, ndi / kapena kusamutsidwa kosavomerezeka kwa topological. Chifukwa cha kuphatikiza koteroko, mutha kupeza mtundu watsopano wa chipangizo, zomwe zimatha kukhala zachilendo kwambiri. Koma, monga asayansi amanenera, uwu ndi mutu wa kafukufuku wina.
Chithunzi #1
Pa chithunzi 1 ikuwonetsa mawonekedwe amitundu itatu ya chipangizo chomwe chimafanana ndi keke wosanjikiza. Galasi wapamwamba wa resonator kuwala ndi siliva wosanjikiza, ndipo m'munsi ndi 12-wosanjikiza anagawira. Bragg reflector*. Pali malo amsewu m'chigawo chogwira ntchito.
Bragg Reflector * Yogawidwa - kapangidwe ka zigawo zingapo, momwe index refractive wa zinthu nthawi amasintha perpendicular zigawo.
Zone ya ngalandeyi imakhala ndi vdW heterostructure yokhala ndi WS2 monolayer (light emitter), zigawo zoonda za hBN mbali zonse za monolayer (chotchinga chotchinga) ndi graphene (maelekitirodi owonekera poyambitsa ma elekitironi ndi mabowo).
Zigawo zina ziwiri za WS2 zinawonjezeredwa kuti ziwonjezere mphamvu zonse za oscillator ndichifukwa chake kukhala ndi kugawanika kwa Rabi kwa mayiko a polariton.
Njira yogwiritsira ntchito resonator imakonzedwa mwa kusintha makulidwe a PMMA wosanjikiza (polymethyl methacrylate, i.e. plexiglass).
chithunzi 1b ichi ndi chithunzithunzi cha vdW heterostructure pamwamba pa kugawidwa kwa Bragg reflector. Chifukwa cha kuwunikira kwakukulu kwa chowunikira cha Bragg chogawidwa, chomwe ndi gawo la pansi, gawo la ngalande pachithunzichi lili ndi mawonekedwe otsika kwambiri, chifukwa chake ndi gawo lokhalo lapamwamba la hBN lomwe limawonedwa.
Zithunzi 1s imayimira chithunzi cha zone ya vdW heterostructure mu tunnel geometry pansi pa kusamutsidwa. Electroluminescence (EL) amawonedwa pamwamba voteji pakhomo pamene mlingo Fermi cha kumtunda (m'munsi) graphene anasintha pamwamba (m'munsimu) ndi WS2 conduction (valence) gulu, kulola ndi elekitironi (dzenje) kuti ngalande mu WS2 conduction (valence) gulu. Izi zimapanga mikhalidwe yabwino yopangira ma excitons mu wosanjikiza wa WS2 wotsatiridwa ndi ma radiation (radiative) electron-hole recombination.
Mosiyana ndi zotulutsa zowunikira zochokera kumagulu a pn, zomwe zimafuna kuti doping igwire ntchito, EL kuchokera ku zipangizo zamakina zimadalira pakalipano, zomwe zimapewa kutayika kwa kuwala ndi kusintha kulikonse kwa resistivity chifukwa cha kusintha kwa kutentha. Panthawi imodzimodziyo, kamangidwe kameneka kamalola malo ochulukirapo kwambiri poyerekeza ndi zida za dichalcogenide zochokera ku pn junctions.
chithunzi 1d ikuwonetsa mawonekedwe amagetsi a tunneling current density (J) ngati ntchito ya bias voltage (V) pakati pa ma electrode a graphene. Kuwonjezeka kwamphamvu kwamagetsi amagetsi abwino komanso oyipa kukuwonetsa kuchitika kwa tunneling yapano kudzera mu kapangidwe kake. Pa makulidwe oyenera a zigawo za hBN (~ 2 nm), kuwongolera kwakukulu kwapano komanso kuwonjezeka kwa moyo wa zonyamulira zobzalidwa kuti ziphatikizidwenso ndi kuwala zimawonedwa.
Asanayambe kuyesa kwa electroluminescence, chipangizochi chinkadziwika ndi kuwala koyera ndi mawonekedwe a angular kuti atsimikizire kukhalapo kwa ma exciton amphamvu.
Chithunzi #2
Pa chithunzi 2 Mawonekedwe owoneka bwino osunthika kuchokera kudera logwira ntchito la chipangizocho akuwonetsedwa, akuwonetsa machitidwe odana ndi kuwoloka. Photoluminescence (PL) idawonedwanso ndi chisangalalo chosatulutsa mpweya (460 nm), kuwonetsa kutulutsa kwakukulu kuchokera kunthambi yotsika ya polariton ndi mpweya wocheperako kuchokera kunthambi yakumtunda kwa polariton (2b).
pa 2s kubalalitsidwa kwa electroluminescence ya polariton kukuwonetsedwa pakuyika kwa 0.1 ΞΌA/ΞΌm2. Kugawanika kwa Rabi ndi kutulutsa kwa resonator komwe kumapezedwa poyika njira za oscillator (mizere yolimba ndi madontho oyera) ku kuyesa kwa electroluminescence ndi ο½33 meV ndi ο½-13 meV, motsatana. Resonator detuning imatanthauzidwa ngati Ξ΄ = Ec - Ex, pomwe Ex ndi mphamvu ya exciton ndipo Ec ndi mphamvu ya resonator photon yokhala ndi zero mu ndege. Ndandanda 2d ndi odulidwa pa ngodya zosiyanasiyana kuchokera electroluminescent dispersion. Apa munthu atha kuwona bwino kubalalitsidwa kwa mitundu yakumtunda ndi yakumunsi ya polariton yokhala ndi anticrossing yomwe imachitika kudera la exciton resonance.
Chithunzi #3
Pamene tunneling ikuwonjezeka, mphamvu yonse ya EL imawonjezeka. EL yofooka kuchokera ku polaritons ikuwoneka pafupi ndi malo osamutsidwa (3), pamene kusintha kwakukulu kokwanira pamwamba pa khomo, kutuluka kwa polariton kumakhala kosiyana (3b).
Pa chithunzi 3s imasonyeza chithunzi cha polar cha mphamvu ya EL ngati ntchito ya ngodya, kusonyeza kanyumba kakang'ono ka Β± 15 Β°. Mtundu wa radiation umakhalabe wosasinthika pazocheperako (zopindikira zobiriwira) komanso zochulukirapo (zopindikira lalanje) zomwe zimasangalatsa pano. Yambani 3d mphamvu yophatikizika imawonetsedwa pamafunde osiyanasiyana osuntha, omwe, monga momwe tawonera pa graph, ndi mzere. Chifukwa chake, kukulitsa zapano mpaka pamtengo wapamwamba kumatha kubweretsa kubalalitsa bwino kwa ma polartons panthambi yotsika ndikupanga mawonekedwe ocheperako kwambiri chifukwa cha kubadwa kwa ma polaritons. Komabe, pakuyesaku, izi sizinali zotheka chifukwa cha kuchepa komwe kumakhudzana ndi kuwonongeka kwa dielectric kwa hBN tunneling chotchinga.
madontho ofiira 3d onetsani miyeso ya chizindikiro china - chakunja kuchuluka kwamphamvu *.
Kuchita bwino kwa Quantum * ndi chiΕ΅erengero cha chiwerengero cha ma photon omwe kuyamwa kwawo kunapangitsa kupanga quasiparticles ku chiwerengero chonse cha ma photons omwe amatengedwa.
Kuwoneka bwino kwachulukidwe kumafanana ndi ma LED ena a polariton (kutengera zinthu zakuthupi, machubu a kaboni, ndi zina). Tiyenera kuzindikira kuti makulidwe a kuwala kotulutsa kuwala mu chipangizo chomwe chikuphunziridwa ndi 0.7 nm, pamene mu zipangizo zina mtengo uwu ndi wapamwamba kwambiri. Asayansi samabisa mfundo yakuti kuchuluka kwa chiwerengero cha chipangizo chawo sichokwera kwambiri, koma chikhoza kuwonjezeka poyika chiwerengero chachikulu cha monolayers mkati mwa chigawo cha ngalandeyo, cholekanitsidwa ndi zigawo zoonda za hBN.
Ofufuzawo adayesanso mphamvu ya resonator yomwe idayimitsidwa pa polariton EL popanga chipangizo china, koma ndikuchotsa mwamphamvu (-43 meV).
Chithunzi #4
Pa chithunzi 4 Mawonekedwe a EL amawonetsedwa ndi kusintha kwa angular kwa chipangizo choterocho pa kachulukidwe kamakono ka 0.2 ΞΌA/ΞΌm2. Chifukwa cha kutsika kolimba, chipangizochi chikuwonetsa kutchulidwa kwa botolo mu EL ndikutulutsa kokwanira komwe kumachitika pamakona akulu. Izi zikutsimikiziridwanso mu chithunzi. 4b, pamene mapulaneti a chipangizochi akufaniziridwa ndi choyamba (2s).
Kuti mudziwe zambiri za ma nuances a phunziroli, ndikupangira kuyang'ana .
Epilogue
Choncho, ziwonetsero zonse ndi miyeso yomwe tafotokozayi imatsimikizira kukhalapo kwa polariton electroluminescence mu vdW heterostructure yomwe ili mu microcavity ya kuwala. Mapangidwe a ngalande ya chipangizo chomwe akuphunziridwa amatsimikizira kukhazikitsidwa kwa ma elekitironi / mabowo ndikuphatikizanso mu WS2 monolayer, yomwe imakhala ngati emitter yowunikira. Nkofunika kuti ngalande limagwirira wa chipangizo sikutanthauza alloying wa zigawo zikuluzikulu, amene kuchepetsa zotayika ndi zosiyanasiyana kutentha zokhudzana kusintha.
Zinapezeka kuti EL ali ndi chiwongolero chachikulu chifukwa cha kubalalitsidwa kwa resonator. Chifukwa chake, kuwongolera mawonekedwe a resonator ndi kupezeka kwaposachedwa kumathandizira kuti ma LED ang'onoang'ono aziwoneka bwino, komanso ma microcavity polaritons oyendetsedwa ndi magetsi ndi ma photon lasers.
Ntchitoyi inatsimikiziranso kuti kusintha kwachitsulo dichalcogenides ali ndi katundu wapadera komanso ntchito zosiyanasiyana.
Kufufuza kotereku komanso kupangidwa kwatsopano kumatha kukhudza kwambiri chitukuko ndi kufalitsa matekinoloje otumizira ma data kudzera mu ma LED ndi kuwala komweko. Tekinoloje zam'tsogolo zotere zikuphatikiza Li-Fi, yomwe imatha kuthamangitsa mwachangu kuposa Wi-Fi yomwe ilipo.
Zikomo chifukwa cha chidwi chanu, khalani ndi chidwi ndikukhala ndi sabata yabwino nonse! π
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