Sekuyiminyaka eminingi ososayensi abavela kuwo wonke umhlaba benza izinto ezimbili - ukusungula nokuthuthukisa. Futhi ngezinye izikhathi akucaci ukuthi yikuphi kwalokhu okunzima kakhulu. Thatha, isibonelo, ama-LED avamile, abonakala elula futhi ajwayelekile kithi kangangokuthi asiwanaki. Kodwa uma ungeza ama-excitons, ingcosana yama-polaritons ne-tungsten disulfide ukunambitha, ama-LED ngeke esaba yi-prosaic. Wonke la magama angacacile angamagama ezingxenye ezingavamile kakhulu, inhlanganisela eyavumela ososayensi baseCity College yaseNew York ukuba benze uhlelo olusha olungadlulisela ulwazi ngokushesha okukhulu ngokusebenzisa ukukhanya. Lokhu kuthuthukiswa kuzosiza ukuthuthukisa ubuchwepheshe be-Li-Fi. Yiziphi ngempela izithako ezisetshenzisiwe zobuchwepheshe obusha, iyini iresiphi yalesi "sitsha" futhi iyini ukusebenza kahle kwe-LED entsha ye-exciton-polariton? Umbiko wososayensi uzositshela ngalokhu. Hamba.
Isisekelo socwaningo
Uma konke kwenziwa lula egameni elilodwa, khona-ke lobu buchwepheshe bulula futhi yonke into ehlangene nayo. Okokuqala, ama-polaritons, avela lapho ama-photons ehlangana ne-medium excitations (amaphononi, ama-exciton, ama-plasmons, ama-magnon, njll.). Okwesibili, ama-exciton ayinjabulo kagesi ku-dielectric, semiconductor noma insimbi, ehamba ngekristalu futhi engahlotshaniswa nokudluliswa kweshaja kagesi nesisindo.
Kubalulekile ukuqaphela ukuthi lawa ma-quasiparticles athanda kakhulu amakhaza; umsebenzi wabo ungabonwa kuphela emazingeni okushisa aphansi kakhulu, okunciphisa kakhulu ukusebenza kwawo okungokoqobo. Kodwa lokho kwakunjalo ngaphambili. Kulo msebenzi, ososayensi bakwazi ukunqoba umkhawulo wokushisa futhi bawasebenzise emazingeni okushisa asekamelweni.
Isici esiyinhloko sama-polaritons yikhono lokubopha ama-photons komunye nomunye. Amaphothoni angqubuzana nama-athomu e-rubidium athola isisindo. Enqubweni yokushayisana okuningi, ama-photon ayagxumana, kodwa ezimweni ezingavamile akha amapheya namawele amathathu, kuyilapho elahlekelwa ingxenye ye-athomu emelwe i-athomu ye-rubidium.
Kodwa ukuze wenze okuthile ngokukhanya, kufanele kubanjwe. Kulokhu, i-resonator optical iyadingeka, okuyinhlanganisela yezinto ezikhanyayo ezakha igagasi lokukhanya elimile.
Kulolu cwaningo, ama-quasiparticles angavamile nakakhulu, ama-exciton-polaritons, akhiwa ngenxa yokuhlangana okuqinile kwama-excitons nama-photon avaleleke emgodini obonakalayo, adlala indima ebalulekile.
Nokho, lokhu akwanele, ngoba isisekelo sezinto ezibonakalayo siyadingeka, ngomqondo ongokomfanekiso. Futhi ubani, uma kungenjalo i-transition metal dichalcogenide (TDM), ozodlala le ndima kangcono kunabanye. Ukunemba kakhudlwana, i-monolayer ye-WS2 (i-tungsten disulfide) yasetshenziswa njengento ekhiphayo, enamandla okubopha ama-exciton ahlaba umxhwele, okwaba ngenye yezindlela eziyinhloko zokukhetha isisekelo sezinto ezibonakalayo.
Inhlanganisela yazo zonke izakhi ezichazwe ngenhla yenze kwaba nokwenzeka ukwakha i-LED ye-polariton elawulwa ngogesi esebenza ekamelweni lokushisa.
Ukuze usebenzise le divayisi, i-WS2 monolayer itholakala phakathi kwezithiyo ze-tunnel ze-boron nitride (hBN) ezacile ezinezendlalelo ze-graphene ezisebenza njengama-electrode.
Imiphumela yocwaningo
I-WS2, eyi-transition metal dichalcogenide, futhi iyimpahla ezacile ye-atom van der Waals (vdW). Lokhu kubonisa izici zayo eziyingqayizivele zikagesi, optical, mechanical kanye ne-thermal.
Ngokuhlanganiswa nezinye izinto ze-vdW, njenge-graphene (njengekhondakta) kanye ne-hexagonal boron nitride (hBN, njengesivikelo), izinhlobonhlobo zamadivaysi e-semiconductor alawulwa ngogesi, ahlanganisa ama-LED, angabonakala. Izinhlanganisela ezifanayo zezinto ze-van der Waals nama-polaritons sezivele zenziwa ngaphambili, njengoba abacwaningi besho ngokungananazi. Kodwa-ke, emibhalweni yangaphambilini, izinhlelo eziwumphumela zaziyinkimbinkimbi futhi zingaphelele, futhi azizange ziveze amandla aphelele wengxenye ngayinye.
Omunye wemibono egqugquzelwe ngabandulelayo kwakuwukusetshenziswa kwesiteji sezinto ezinezinhlangothi ezimbili. Kulesi simo, kungenzeka ukusebenzisa amadivaysi anezendlalelo ze-athomu ezincane ezikhishwayo ezingahlanganiswa nezinye izinto ze-vdW ezisebenza njengabathintwayo (i-graphene) nezithiyo ze-tunneling (hBN). Ngaphezu kwalokho, lobu bukhulu obubili bukwenza kube nokwenzeka ukuhlanganisa ama-LED e-polariton nezinto ze-vdW ezinezakhiwo ezingavamile kazibuthe, i-superconductivity eqinile, kanye/noma ukudluliselwa kwe-topological okungajwayelekile. Njengomphumela wenhlanganisela enjalo, ungathola uhlobo olusha ngokuphelele lwedivayisi, izakhiwo zazo ezingaba ezingavamile kakhulu. Kodwa, njengoba ososayensi besho, lesi yisihloko solunye ucwaningo.
Isithombe #1
Esithombeni I-1 ibonisa imodeli enezinhlangothi ezintathu zedivayisi efana nekhekhe lesendlalelo. Isibuko esingaphezulu se-resonator optical sisendlalelo sesiliva, futhi esiphansi sisakazwa ungqimba oluyi-12. I-Bragg reflector*. Kukhona indawo yomhubhe endaweni esebenzayo.
I-Bragg Reflector* esabalalisiwe - isakhiwo sezendlalelo eziningana, lapho inkomba ye-refractive yezinto ezibonakalayo ishintsha ngezikhathi ezithile i-perpendicular to the layers.
Indawo yomhubhe iqukethe i-vdW heterostructure ehlanganisa i-WS2 monolayer (i-emitter yokukhanya), izendlalelo ezincane ze-hBN ezinhlangothini zombili ze-monolayer (umgoqo womhubhe) kanye ne-graphene (ama-electrode asobala okwethulwa kwama-electron nezimbobo).
Izendlalelo ezengeziwe ezimbili ze-WS2 zengezwe ukuze kwandiswe amandla ewonke e-oscillator futhi ngaleyo ndlela kube nokuhlukaniswa okugqamile kwe-Rabi kwezifunda ze-polariton.
Imodi yokusebenza ye-resonator ishunwa ngokushintsha ukujiya kongqimba lwe-PMMA (i-polymethyl methacrylate, okungukuthi i-plexiglass).
Isithombe 1b lesi isifinyezo se-vdW heterostructure endaweni yesibonisi esisabalalisiwe se-Bragg. Ngenxa yokukhanya okuphezulu kwesibonisi esisabalalisiwe se-Bragg, okuyisendlalelo esingezansi, indawo yomhubhe osesithombeni inomehluko ophansi kakhulu wokubonisa, ngenxa yalokho okubonwa kuphela ungqimba olungaphezulu oluwugqinsi lwe-hBN.
Igrafu 1s imele umdwebo wezoni we-vdW heterostructure emhubheni wejometri ngaphansi kokususwa. I-Electroluminescence (EL) ibonwa ngaphezu kwe-threshold voltage lapho izinga le-Fermi legraphene engenhla (ephansi) igudluzwa ngenhla (ngezansi) kwebhendi ye-WS2 conduction (valence), ivumela i-electron (imbobo) ukuthi ingene ekuqhubeni kwe-WS2 (valence) ibhande. Lokhu kudala izimo ezivumayo zokwakheka kwama-exciton kusendlalelo se-WS2 okulandelwa ukuhlanganisa kabusha kwembobo ye-electron ekhipha imisebe (radiative).
Ngokungafani ne-emitters yokukhanya esekelwe ku-pn junctions, edinga i-doping ukuze isebenze, i-EL evela kumadivayisi emhubhe incike kuphela kumhubhe wamanje, ogwema ukulahlekelwa kwe-optical kanye nanoma yiziphi izinguquko zokuphikiswa okubangelwa ukushintsha kwezinga lokushisa. Ngesikhathi esifanayo, ukwakheka komhubhe kuvumela indawo emisebeni emikhulu kakhulu uma kuqhathaniswa namadivayisi e-dichalcogenide asekelwe ku-pn junctions.
Isithombe 1d ikhombisa izici zikagesi ze-tunnel yamanje (J) njengomsebenzi we-voltage echema (V) phakathi kwama-electrode e-graphene. Ukwenyuka okubukhali kwamandla akho kokubili i-voltage eqondile nengalungile ibonisa ukwenzeka kwamandla omhubhe ngesakhiwo. Ebugqileni obufanele bezendlalelo ze-hBN (~2 nm), amandla omhubhe abalulekile kanye nokwanda kwesikhathi sokuphila kwezithwali ezitshaliwe zokuhlanganiswa kabusha kwemisebe kuyabonwa.
Ngaphambi kokuhlolwa kwe-electroluminescence, idivayisi ibibonakala ngokubonakala kokukhanya okumhlophe okunokulungiswa kwe-angular ukuze kuqinisekiswe ubukhona bokubopha okuqinile kwe-exciton.
Isithombe #2
Esithombeni I-2 i-spectra ebonisa i-engeli exazululiwe evela endaweni esebenzayo yedivayisi iyaboniswa, ibonisa ukuziphatha okuphambene nokuwela. I-Photoluminescence (PL) iphinde yabonwa ngesasasa elingaguquki (460 nm), ikhombisa ukuphuma okukhulu okuvela egatsheni elingezansi le-polariton kanye nokukhipha okubuthakathaka okuvela egatsheni elingenhla le-polariton (2b).
In 2s ukuhlakazwa kwe-electroluminescence ye-polariton kuboniswa ukuze kufakwe u-0.1 μA/μm2. Ukuhlukaniswa kwe-Rabi kanye ne-resonator etholwe ngokufaka amamodi e-oscillator (umugqa omhlophe oqinile nonamachashazi) ekuhlolweni kwe-electroluminescence ingu-～33 meV kanye no-～-13 meV, ngokulandelanayo. I-resonator detuning ichazwa ngokuthi δ = Ec − Ex, lapho i-Ex ingamandla e-exciton kanye ne-Ec amandla e-resonator photon anomfutho oyiziro endizeni. Isheduli 2d iwukusikwa ngama-engeli ahlukene kusukela ekuhlakazweni kwe-electroluminescent. Lapha umuntu angabona ngokucacile ukuhlakazeka kwezindlela ze-polariton ezingenhla neziphansi ezine-anticrossing ezenzeka endaweni ye-exciton resonance.
Isithombe #3
Njengoba i-tunneling yamanje ikhula, ukuqina kwe-EL okuphelele kuyanda. I-EL ebuthakathaka evela kuma-polaritons ibonwa eduze komkhawulo wokufuduka (I-3), ngenkathi ekushintsheni okukhulu ngokwanele ngaphezu komkhawulo, ukuphuma kwe-polariton kuyahluka (3b).
Esithombeni 3s ibonisa igrafu ephothuliwe yokuqina kwe-EL njengomsebenzi we-engeli, ebonisa ikhoni ekhiphayo encane engu-± 15°. Iphethini yemisebe ihlala ingashintshile kukho kokubili ubuncane (ijika eliluhlaza) kanye nobukhulu (ijika eliwolintshi) lamanje lokuvusa amadlingozi. Vuliwe 3d ukuqina okuhlanganisiwe kukhonjiswa emisinga ehlukahlukene enyakazayo yomhubhe, okuthi, njengoba kubonakala kugrafu, iqondile impela. Ngakho-ke, ukwandisa umthamo wamanje kumanani aphezulu kungaholela ekuhlakazweni okuphumelelayo kwama-polariton egatsheni eliphansi futhi kudale iphethini yemisebe emincane kakhulu ngenxa yokukhiqizwa kwama-polaritons. Nokho, kulokhu kuhlolwa, lokhu akwenzekanga ngenxa yomkhawulo ohlobene nokuwohloka kwe-dielectric komgoqo womhubhe we-hBN.
amachashazi abomvu avuliwe 3d khombisa izilinganiso zesinye isikhombisi - sangaphandle ukusebenza kahle kwe-quantum*.
I-Quantum Efficiency* isilinganiso senani lamaphothoni ukumuncwa kwawo kubangele ukwakheka kwama-quasiparticles ukuya enanini eliphelele lamaphothoni amuncwe.
Ukusebenza kahle kwe-quantum okuphawuliwe kuqhathaniswa nalokho kwamanye ama-LED e-polariton (ngokusekelwe ezintweni eziphilayo, amashubhu ekhabhoni, njll.). Kumele kuqashelwe ukuthi ukushuba kongqimba olukhipha ukukhanya kudivayisi efundwayo kungu-0.7 nm kuphela, kuyilapho kwamanye amadivaysi leli nani liphezulu kakhulu. Ososayensi abafihli iqiniso lokuthi inkomba ye-quantum yokusebenza kahle kwedivayisi yabo ayiyona ephakeme kakhulu, kodwa ingandiswa ngokubeka inombolo enkulu yama-monolayers ngaphakathi kwendawo yomhubhe, ehlukaniswe izingqimba ezincane ze-hBN.
Abacwaningi baphinde bahlola ithonya le-resonator detuning ku-polariton EL ngokwenza enye idivayisi, kodwa nge-detuning enamandla (-43 meV).
Isithombe #4
Esithombeni I-4 I-EL spectra iboniswa ngokulungiswa kwe-angular kwedivayisi enjalo ekumineni kwamanje okungu-0.2 μA/μm2. Ngenxa ye-detuning eqinile, idivayisi ibonisa umphumela oshiwo we-bottleneck ku-EL nokuphuma okuphezulu okwenzeka nge-engeli enkulu. Lokhu kuqinisekiswa ngokwengeziwe esithombeni. 4b, lapho izingxenye ze-polar zalo mshini ziqhathaniswa nezokuqala (2s).
Ukuze uthole ulwazi oluningiliziwe ngama-nuances ocwaningo, ngincoma ukubheka .
Epilogue
Ngakho-ke, konke ukubhekwa nokulinganisa okuchazwe ngenhla kuqinisekisa ukuba khona kwe-polariton electroluminescence ku-vdW heterostructure efakwe ku-microcavity optical. Isakhiwo somhubhe wedivayisi esicwaningwayo siqinisekisa ukwethulwa kwama-electron/izimbobo nokuphinda kuhlanganiswe ku-WS2 monolayer, esebenza njengesisi esikhipha ukukhanya. Kubalulekile ukuthi indlela yomhubhe yedivayisi ayidingi i-alloying yezingxenye, okunciphisa ukulahlekelwa kanye nezinguquko ezihlukahlukene ezihlobene nezinga lokushisa.
Kwatholakala ukuthi i-EL inokuqondisa okuphezulu ngenxa yokuhlakazeka kwe-resonator. Ngakho-ke, ukuthuthukisa isici sekhwalithi ye-resonator kanye nokunikezwa kwamanje okuphezulu kuzothuthukisa ukusebenza kahle kwama-microcavity LEDs, kanye nama-microcavity polaritons alawulwa ngogesi nama-photon lasers.
Lo msebenzi uphinde waqinisekisa ukuthi i-transition metal dichalcogenides inezakhiwo eziyingqayizivele ngempela kanye nohlu olubanzi kakhulu lwezinhlelo zokusebenza.
Ucwaningo olunjalo kanye nokusungulwa kwezinto ezintsha kungaba nomthelela omkhulu ekuthuthukisweni nasekusatshalalisweni kobuchwepheshe bokudluliswa kwedatha ngama-LED nokukhanya ngokwako. Ubuchwepheshe obunjalo bekusasa buhlanganisa i-Li-Fi, engahlinzeka ngesivinini esisheshayo kune-Wi-Fi etholakalayo njengamanje.
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Source: www.habr.com