Tau ntau xyoo, cov kws tshawb fawb los ntawm thoob plaws lub ntiaj teb tau ua ob yam - tsim thiab txhim kho. Thiab qee zaum nws tsis meej tias qhov twg nyuaj dua. Piv txwv li, LEDs zoo tib yam, uas zoo li yooj yim thiab zoo tib yam rau peb uas peb tsis txawm them rau lawv. Tab sis yog tias koj ntxiv ob peb excitons, pinch ntawm polaritons thiab tungsten disulfide rau saj, LEDs yuav tsis yog li prosaic. Tag nrho cov lus tsis txaus ntseeg no yog cov npe ntawm cov khoom sib txawv heev, kev sib xyaw ua ke uas tso cai rau cov kws tshawb fawb los ntawm City College of New York los tsim cov txheej txheem tshiab uas muaj peev xwm xa cov ntaub ntawv sai heev uas siv lub teeb. Qhov kev txhim kho no yuav pab txhim kho Li-Fi thev naus laus zis. Dab tsi yog cov khoom xyaw ntawm cov thev naus laus zis tshiab tau siv, dab tsi yog daim ntawv qhia rau "zaub mov" no thiab dab tsi yog qhov kev ua haujlwm ntawm exciton-polariton LED tshiab? Daim ntawv tshaj tawm ntawm cov kws tshawb fawb yuav qhia peb txog qhov no. Mus.
Kev tshawb fawb hauv paus
Yog tias peb ua kom yooj yim txhua yam mus rau ib lo lus, ces qhov kev siv tshuab no yog lub teeb thiab txhua yam txuas nrog nws. Ua ntej, polaritons, uas tshwm sim thaum photons cuam tshuam nrog excitations ntawm nruab nrab (phonons, excitons, plasmons, magnons, thiab lwm yam). Qhov thib ob, excitons yog hluav taws xob excitations nyob rau hauv ib tug dielectric, semiconductor los yog hlau uas tsiv mus nyob thoob plaws hauv lub siv lead ua thiab tsis txuam nrog kev hloov ntawm hluav taws xob nqi thiab loj.
Nws yog ib qho tseem ceeb kom nco ntsoov tias cov quasiparticles nyiam txias heev, piv txwv li. Lawv cov dej num tsuas tuaj yeem pom ntawm qhov kub thiab txias, uas txwv tsis pub lawv cov kev siv tau zoo heev. Tab sis ua ntej ntawd. Hauv txoj haujlwm no, cov kws tshawb fawb muaj peev xwm kov yeej qhov kev txwv qhov kub thiab siv rau hauv chav tsev kub.
Lub ntsiab feature ntawm polaritons yog lub peev xwm los khi photons nrog ib leeg. Photons sib tsoo nrog rubidium atoms tau txais huab hwm coj. Nyob rau hauv tus txheej txheem ntawm kev sib tsoo, cov photons thaws tawm ib leeg, tab sis nyob rau hauv tsawg zaus lawv tsim khub thiab triplets, thaum poob lub atomic tivthaiv sawv cev los ntawm rubidium atom.
Tab sis ua ib yam dab tsi nrog lub teeb, koj yuav tsum tau ntes nws. Rau qhov no, xav tau ib qho optical resonator, uas yog ib txheej ntawm cov ntsiab lus ntawm kev xav uas tsim ib lub teeb yoj sawv.
Nyob rau hauv txoj kev tshawb no, lub luag hauj lwm tseem ceeb tshaj plaws yog ua los ntawm ntau yam txawv txawv quasiparticles - exciton-polaritons, uas yog tsim vim muaj zog coupling ntawm excitons thiab photons daig nyob rau hauv ib tug optical kab noj hniav.
Txawm li cas los xij, qhov no tsis txaus, vim tias yuav tsum muaj cov khoom siv hauv paus, yog li hais. Thiab leej twg zoo dua li kev hloov pauv hlau dichalcogenide (TMD) yuav ua lub luag haujlwm no? Ntau qhov tseeb, WS2 (tungsten disulfide) monolayer tau siv los ua cov khoom siv hluav taws xob, uas muaj lub zog exciton binding energies, uas tau los ua ib qho tseem ceeb ntawm kev xaiv cov khoom siv hauv paus.
Kev sib xyaw ua ke ntawm tag nrho cov ntsiab lus tau piav qhia saum toj no ua rau nws tuaj yeem tsim hluav taws xob tswj hluav taws xob polariton LED ua haujlwm ntawm chav tsev kub.
Yuav kom paub txog cov cuab yeej no, ib qho monolayer ntawm WS2 yog sandwiched ntawm nyias hexagonal boron nitride (hBN) tunnel barriers nrog graphene txheej ua raws li electrodes.
Cov txiaj ntsig tshawb fawb
WS2, ua ib qho kev hloov pauv hlau dichalcogenide, kuj yog cov khoom siv atomically nyias van der Waals (vdW). Qhov no hais txog nws qhov tshwj xeeb hluav taws xob, kho qhov muag, mechanical thiab thermal zog.
Ua ke nrog lwm cov ntaub ntawv vdW, xws li graphene (raws li tus neeg xyuas pib) thiab hexagonal boron nitride (hBN, raws li ib qho insulator), tag nrho cov tswv ntawm cov khoom siv hluav taws xob tswj cov khoom siv hluav taws xob, uas suav nrog LEDs, tuaj yeem ua tiav. Kev sib xyaw ua ke zoo sib xws ntawm van der Waals cov ntaub ntawv thiab cov polaritons twb tau paub ua ntej, raws li cov kws tshawb fawb tau qhib siab. Txawm li cas los xij, hauv kev ua haujlwm yav dhau los, cov txiaj ntsig tau ua haujlwm nyuaj thiab tsis zoo, thiab tsis tau nthuav tawm tag nrho cov peev txheej ntawm txhua yam.
Ib qho ntawm cov tswv yim uas tau tshwm sim los ntawm cov neeg ua ntej yog kev siv cov khoom siv ob sab. Nyob rau hauv rooj plaub no, nws muaj peev xwm ua kom paub cov khoom siv nrog atomically nyias emissive txheej, uas tuaj yeem ua ke nrog lwm cov ntaub ntawv vdW ua haujlwm raws li kev sib cuag (graphene) thiab qhov thaiv qhov thaiv (hBN). Tsis tas li ntawd, qhov ob-dimensionality no ua rau nws muaj peev xwm ua ke cov polariton LEDs nrog vdW cov ntaub ntawv uas muaj cov khoom sib nqus txawv txawv, muaj zog superconductivity thiab / lossis tsis yog tus qauv topological hloov pauv. Raws li ib tug tshwm sim ntawm xws li ib tug ua ke, ib tug kiag li tshiab ntaus ntawv yuav tau txais, cov khoom uas yuav txawv heev. Tab sis, raws li cov kws tshawb fawb hais, qhov no yog lub ntsiab lus rau lwm txoj kev tshawb fawb.
Duab #1
Ntawm daim duab 1 qhia peb-dimensional qauv ntawm ib lub cuab yeej zoo li lub ncuav mog qab zib txheej. Sab saum toj daim iav ntawm optical resonator yog ib txheej nyiaj, thiab daim iav qis yog 12-txheej faib Bragg reflector *. Lub active cheeb tsam muaj ib tug tunnel cheeb tsam.
Distributed Bragg reflector * - ib tug qauv ntawm ob peb txheej nyob rau hauv uas lub refractive index ntawm cov khoom ib ntus hloov perpendicular mus rau cov khaubncaws sab nraud povtseg.
Thaj chaw qhov av muaj vdW heterostructure muaj xws li WS2 monolayer (lub teeb emitter), nyias txheej ntawm hBN ntawm ob sab ntawm monolayer (tunnel barrier) thiab graphene (pob tshab electrodes rau qhia electrons thiab qhov).
Ob txheej ntxiv ntawm WS2 tau ntxiv los ua kom lub zog tag nrho ntawm cov oscillator thiab li no los tsim cov lus tshaj tawm Rabi splitting ntawm lub xeev polariton.
Kev khiav hauj lwm hom ntawm lub resonator yog kho los ntawm kev hloov lub thickness ntawm PMMA txheej (polymethyl methacrylate, i.e. plexiglass).
Image Duab 1b Qhov no yog ib tug snapshot ntawm ib tug vdW heterostructure nyob rau saum npoo ntawm ib tug faib Bragg reflector. Vim yog lub siab xav tau ntawm qhov kev faib tawm Bragg reflector, uas yog txheej hauv qab, thaj tsam qhov hauv daim duab muaj qhov sib txawv tsis tshua muaj kev cuam tshuam, uas ua rau tsuas yog sab saum toj tuab hBN txheej.
Teeb 1c ib yog vdW zone diagram ntawm heterostructure nyob rau hauv lub qhov geometry nyob rau hauv kev hloov chaw. Electroluminescence (EL) raug soj ntsuam saum toj ntawm qhov pib voltage thaum Fermi theem ntawm sab saum toj (hauv qab) graphene hloov mus rau saum toj (hauv qab) cov conduction (valence) band ntawm WS2, tso cai rau ib qho hluav taws xob (qhov) mus rau hauv qhov conduction (valence) band WS 2. Qhov no tsim cov kev mob zoo rau kev tsim cov excitons hauv WS2 txheej nrog cov hluav taws xob tom ntej (radiative) electron-qhov recombination.
Tsis zoo li pn hlws ris lub teeb emitters, uas yuav tsum tau doping rau kev khiav hauj lwm, EL los ntawm qhov tunnel devices nyob ntawm lub qhov tam sim no nkaus xwb, zam optical losses thiab tej yam kev hloov nyob rau hauv resistivity los ntawm kub hloov. Nyob rau tib lub sijhawm, qhov kev tsim vaj tsev tso cai rau thaj tsam emission loj dua piv rau cov khoom siv dichalcogenide raws li pn junctions.
Image Duab 1d ua kom pom cov yam ntxwv hluav taws xob ntawm qhov tunneling tam sim no ceev (J) raws li kev ua haujlwm ntawm bias voltage (V) ntawm graphene electrodes. Ib qho kev nce ntxiv hauv tam sim no rau ob qho tib si zoo thiab tsis zoo voltages qhia qhov tshwm sim ntawm tunneling tam sim no los ntawm cov qauv. Ntawm qhov zoo tshaj plaws thickness ntawm hBN txheej (~ 2 nm), ib tug tseem ceeb tunneling tam sim no thiab ib tug nce nyob rau hauv lub neej ntawm embedded cab kuj rau radiative recombination.
Ua ntej ua qhov kev sim electroluminescence, cov cuab yeej tau pom los ntawm lub kaum sab xis daws teeb meem dawb lub teeb pom kev kom paub meej tias muaj qhov muaj zog excitonic coupling.
Duab #2
Ntawm daim duab 2 Angle-resolved reflectance spectra los ntawm thaj chaw nquag ntawm cov cuab yeej tau pom, ua qauv qhia kev tiv thaiv kev hla. Photoluminescence (PL) kuj tau pom nyob rau hauv uas tsis yog-resonant excitation (460 nm), uas qhia cov emission khaus los ntawm sab polariton ceg thiab tsis muaj zog emission los ntawm sab sauv polariton ceg (2b).
rau 2c ib qhia cov dispersion ntawm polariton electroluminescence ntawm kev txhaj tshuaj ntawm 0.1 ΞΌA / ΞΌm2. Rabi splitting thiab kab noj hniav detuning tau los ntawm haum cov oscillator hom (khoom thiab dashed dawb kab) rau EL sim yog ο½33 meV thiab ο½-13 meV, feem. Cov kab noj hniav detuning yog txhais raws li Ξ΄ = Ec β Ex, qhov twg Ex yog lub zog exciton thiab Ec qhia txog lub dav hlau xoom-momentum kab noj hniav photon zog. Teem caij 2d Qhov no yog txiav ntawm cov ces kaum sib txawv los ntawm electroluminescent dispersion. Ntawm no, qhov tawg ntawm sab sauv thiab sab polariton hom nrog anticrossing tshwm sim hauv thaj chaw exciton resonance yog pom meej.
Duab #3
Raws li qhov tunneling tam sim no nce, tag nrho EL kev siv zog nce. Tsis muaj zog EL los ntawm polaritons tau pom nyob ze ntawm qhov pib ua haujlwm (3), thaum nyob rau ntawm qhov chaw loj txaus siab tshaj qhov pib, polariton emission yuav txawv (3b).
Ntawm daim duab 3c ib qhia txog lub ntsiab lus ntawm EL kev siv zog ua haujlwm ntawm lub kaum sab xis, qhia txog lub voj voog nqaim ntawm Β± 15 Β°. Cov qauv hluav taws xob tseem zoo li tsis hloov pauv rau qhov tsawg kawg nkaus (ntsuab nkhaus) thiab qhov siab tshaj plaws (txiv kab ntxwv nkhaus) excitation tam sim no. Ntawm 3d qhia tau hais tias muaj kev sib xyaw ua ke rau ntau yam kev txav ntawm qhov tam sim no, uas, raws li tau pom los ntawm daim duab, yog linear heev. Yog li ntawd, kev nce tam sim no mus rau qhov muaj txiaj ntsig siab tuaj yeem ua rau muaj kev vam meej tawg ntawm cov polaritons raws cov ceg qis thiab tsim kom muaj cov qauv nqaim nqaim heev vim yog tiam polariton. Txawm li cas los xij, hauv qhov kev sim no nws tsis tuaj yeem ua tiav qhov no vim qhov kev txwv cuam tshuam nrog dielectric tawg ntawm hBN qhov barrier.
Liab dots rau 3d qhia kev ntsuas ntawm lwm qhov ntsuas - sab nraud quantum efficiency *.
Quantum efficiency * - qhov piv ntawm tus naj npawb ntawm photons, qhov nqus ntawm uas ua rau tsim ntawm quasiparticles, mus rau tag nrho cov naj npawb ntawm photons absorbed.
Qhov pom kev ua haujlwm ntawm quantum yog piv rau lwm cov polariton LEDs (raws li cov khoom siv organic, carbon tubes, thiab lwm yam). Nws yog ib nqi sau cia hais tias nyob rau hauv lub ntaus ntawv nyob rau hauv kev kawm lub thickness ntawm lub teeb-emitting txheej tsuas yog 0.7 nm, thaum nyob rau hauv lwm yam khoom siv no tus nqi yog ntau dua. Cov kws tshawb fawb tsis zais qhov tseeb tias quantum efficiency ntawm lawv cov cuab yeej tsis yog qhov siab tshaj plaws, tab sis nws tuaj yeem nce ntxiv los ntawm kev tso cov monolayers ntau dua hauv thaj tsam qhov av, sib cais los ntawm nyias txheej ntawm hBN.
Cov kws tshawb fawb kuj tau sim cov nyhuv ntawm resonator detuning ntawm polariton EL los ntawm kev ua lwm yam cuab yeej, tab sis nrog lub zog detuning (-43 meV).
Duab #4
Ntawm daim duab 4 EL spectra nrog angular daws teeb meem ntawm cov cuab yeej zoo li no tau pom ntawm qhov ceev tam sim no ntawm 0.2 ΞΌA / ΞΌm2. Vim yog qhov muaj zog detuning, cov cuab yeej nthuav tawm cov txiaj ntsig ntawm lub raj mis hauv EL nrog rau qhov siab tshaj plaws emission tshwm sim ntawm lub kaum sab xis loj. Qhov no tau lees paub ntxiv hauv daim duab 4b, qhov twg lub polar graphs ntawm cov cuab yeej no muab piv nrog thawj tus (2c ib).
Rau cov ncauj lus kom ntxaws ntxiv nrog cov nuances ntawm txoj kev tshawb no, kuv xav kom saib .
Epilogue
Yog li, tag nrho cov kev soj ntsuam thiab kev ntsuas tau piav qhia saum toj no paub meej tias muaj cov polariton electroluminescence nyob rau hauv vdW heterostructure ua rau hauv qhov chaw kho qhov muag microcavity. Lub tunnel architecture ntawm lub cuab yeej nyob rau hauv txoj kev tshawb fawb xyuas kom meej qhov kev taw qhia ntawm electrons / qhov thiab recombination nyob rau hauv WS2 monolayer, uas ua hauj lwm raws li lub teeb emitter. Nws yog ib qho tseem ceeb uas lub tunnel mechanism ntawm lub cuab yeej tsis tas yuav tsum tau alloying ntawm lub Cheebtsam, uas minimizes poob thiab ntau yam kub-txog kev hloov.
Nws tau pom tias EL muaj kev coj ncaj ncees siab vim qhov tawg ntawm lub resonator. Yog li ntawd, kev txhim kho cov kab noj hniav zoo thiab kev xa khoom ntau dua tam sim no yuav txhim kho kev ua haujlwm ntawm microcavity LEDs, nrog rau cov hluav taws xob tswj microcavity polaritons thiab photonic lasers.
Qhov haujlwm no tau lees paub dua tias kev hloov pauv hlau dichalcogenides muaj cov khoom tshwj xeeb tiag tiag thiab ntau yam kev siv.
Xws li kev tshawb fawb thiab kev tsim kho tshiab tuaj yeem cuam tshuam rau txoj kev loj hlob thiab kev sib kis ntawm cov ntaub ntawv xa mus siv cov LEDs thiab lub teeb nws tus kheej. Xws li futuristic technologies suav nrog Li-Fi, uas tuaj yeem muab kev nrawm dua li tam sim no muaj Wi-Fi.
Ua tsaug rau kev nyeem ntawv, nyob xav paub thiab muaj lub lim tiam zoo! π
Ua tsaug uas koj nyob nrog peb. Koj puas nyiam peb cov ntawv? Xav pom cov ntsiab lus nthuav ntxiv? Txhawb nqa peb los ntawm kev tso ib qho kev txiav txim lossis qhia rau cov phooj ywg, 30% luv nqi rau cov neeg siv Habr ntawm qhov tshwj xeeb analogue ntawm nkag-theem servers, uas tau tsim los ntawm peb rau koj: (muaj nrog RAID1 thiab RAID10, mus txog 24 cores thiab mus txog 40GB DDR4).
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