Ruo ọtụtụ afọ, ndị ọkà mmụta sayensị si n'akụkụ ụwa nile na-eme ihe abụọ - ịmepụta na imeziwanye. Ma mgbe ụfọdụ, o doro anya na nke siri ike karị. Were, dịka ọmụmaatụ, LEDs nkịtị, nke yiri ka ọ dị mfe na ndị nkịtị na anyị na-adịghị etinye uche na ha. Ma ọ bụrụ na ị tinye ole na ole excitons, a tuo nke polaritons na tungsten disulfide nụrụ ụtọ, LEDs agaghịkwa adị otú prosaic. Okwu abstruse ndị a niile bụ aha akụrụngwa pụrụ iche, nchikota nke kwere ka ndị ọkà mmụta sayensị si na City College nke New York mepụta usoro ọhụrụ nke nwere ike ibunye ozi ngwa ngwa site na iji ọkụ. Mmepe a ga-enyere aka melite teknụzụ Li-Fi. Kedu ihe eji eme ihe nke teknụzụ ọhụrụ, kedu ihe bụ uzommeputa maka “efere” a yana kedu ihe arụ ọrụ nke exciton-polariton LED ọhụrụ? Akụkọ ndị ọkà mmụta sayensị ga-agwa anyị banyere nke a. Gaa.
Ntọala nyocha
Ọ bụrụ na anyị na-eme ka ihe niile dị mfe ruo otu okwu, mgbe ahụ, nkà na ụzụ a bụ ìhè na ihe niile jikọtara ya. Nke mbụ, polaritons, nke na-ebilite mgbe photons na-emekọrịta ihe na mkpali nke usoro (phonons, excitons, plasmons, magnons, wdg). Nke abuo, excitons bụ ihe mkpali eletrọnịkị na dielectric, semiconductor ma ọ bụ metal nke na-akwaga na kristal niile na anaghị ejikọta ya na ịnyefe ọkụ eletrik na oke.
Ọ dị mkpa ịmara na quasiparticles ndị a hụrụ oyi n'anya nke ukwuu, ya bụ. Enwere ike ịhụ ọrụ ha na oke okpomọkụ dị oke ala, nke na-egbochi ngwa ha bara uru nke ukwuu. Ma nke ahụ bụbu. N'ime ọrụ a, ndị ọkà mmụta sayensị nwere ike imeri njedebe okpomọkụ ma jiri ha mee ihe na okpomọkụ.
Akụkụ bụ isi nke polaritons bụ ikike ijikọ foton na ibe ya. Photons na-agbakọ na rubidium atom na-enweta oke. Na usoro nke nkukota ugboro ugboro, photons na-agbapụ ibe ha, ma n'ọnọdụ ndị a na-adịghị ahụkebe, ha na-etolite ụzọ abụọ na atọ, ebe ha na-efunahụ akụkụ atọ nke rubidium atom na-anọchi anya ya.
Mana iji ọkụ mee ihe, ịkwesịrị ijide ya. Maka nke a, achọrọ resonator ngwa anya, nke bụ ihe ndị na-atụgharị anya na-eme ka ọkụ na-eguzo ọtọ.
N'ime ọmụmụ ihe a, ọrụ kachasị mkpa na-arụ site n'ụdị quasiparticles ndị ọzọ na-adịghị ahụkebe - exciton-polaritons, nke a na-etolite n'ihi njikọ siri ike nke excitons na photons tọrọ atọ n'ime oghere anya.
Otú ọ dị, nke a ezughị, n'ihi na ihe ndabere ihe onwunwe dị mkpa, dị ka a pụrụ isi kwuo ya. Ma onye dị mma karịa mgbanwe metal dichalcogenide (TMD) ga-arụ ọrụ a? Kpọmkwem, a na-eji monolayer WS2 (tungsten disulfide) mee ihe dị ka ihe na-emepụta ihe, nke nwere nnukwu ike na-ejikọta ike, nke ghọrọ otu n'ime ihe ndị bụ isi maka ịhọrọ ntọala ihe.
Nchikota nke ihe niile a kọwara n'elu mere ka o kwe omume ịmepụta ọkụ eletrik na-achịkwa polariton LED na-arụ ọrụ na ụlọ okpomọkụ.
Iji ghọta ngwaọrụ a, a na-agbanye otu monolayer nke WS2 n'etiti mgbochi hexagonal boron nitride (hBN) nke nwere oghere graphene na-eme dị ka electrodes.
Nsonaazụ nyocha
WS2, ịbụ ihe ngbanwe metal dichalcogenide, bụkwa ihe dị mkpa van der Waals (vdW). Nke a na-ekwu maka ọkụ eletrik ya pụrụ iche, ngwa anya, igwe na ihe ọkụ.
Na mgbakwunye na ihe vdW ndị ọzọ, dị ka graphene (dị ka onye na-eduzi) na hexagonal boron nitride (hBN, dị ka ihe insulator), nwere ike imezu ihe niile nke ngwaọrụ semiconductor na-achịkwa ọkụ eletrik, nke gụnyere LEDs. Ngwakọta ndị yiri nke ahụ nke ihe van der Waals na polaritons achọpụtalarị na mbụ, dịka ndị nyocha ahụ kwuru n'ihu ọha. Otú ọ dị, na ọrụ ndị gara aga, usoro ndị na-esi na ya pụta dị mgbagwoju anya na ndị na-ezughị okè, ma ekpugheghị ikike nke akụkụ ọ bụla.
Otu n'ime echiche sitere n'ike mmụọ nsọ nke ndị bu ya ụzọ bụ iji ikpo okwu ihe nwere akụkụ abụọ. N'okwu a, ọ ga-ekwe omume ịghọta ngwaọrụ ndị nwere akwa mkpuchi ikuku na-adịghị mkpa, nke enwere ike ijikọ ya na ihe vdW ndị ọzọ na-eme dị ka kọntaktị (graphene) na ọwara ọwara (hBN). Na mgbakwunye, ụdị akụkụ abụọ dị otú ahụ na-eme ka o kwe omume ijikọ LEDs polariton na ihe vdW nwere ihe ndọta pụrụ iche, ike superconductivity na/ma ọ bụ mbufe topological na-abụghị ọkọlọtọ. N'ihi nchikota dị otú ahụ, enwere ike ịnweta ụdị ngwaọrụ ọhụrụ kpamkpam, njirimara nke nwere ike ịbụ ihe ọhụrụ. Ma, dị ka ndị ọkà mmụta sayensị na-ekwu, nke a bụ isiokwu maka ọmụmụ ihe ọzọ.
Foto #1
Na onyonyo a 1 na-egosi ụdị akụkụ atọ nke ngwaọrụ nke yiri achicha oyi akwa. Ngosi elu nke resonator anya bụ oyi akwa ọlaọcha, na enyo nke dị ala bụ nkesa 12-layer. Bragg reflector*. Mpaghara nọ n'ọrụ nwere mpaghara ọwara.
Ekesara Bragg reflector* - a Ọdịdị nke ọtụtụ n'ígwé nke refractive index nke ihe onwunwe na-agbanwe kwa oge perpendicular na n'ígwé.
Mpaghara ọwara ahụ nwere vdW heterostructure nke nwere WS2 monolayer (light emitter), obere nchara nke hBN n'akụkụ abụọ nke monolayer (ihe mgbochi ọwara) na graphene (electrodes transperent maka iwebata electrons na oghere).
Agbakwunyere akwa abụọ nke WS2 iji bulie ike oscillator n'ozuzu ya wee wepụta Rabi nkewa karịa nke steeti polariton.
A na-edozi ọnọdụ ọrụ nke resonator site n'ịgbanwe oke nke oyi akwa PMMA (polymethyl methacrylate, i.e. plexiglass).
Image Image 1b Nke a bụ nseta ihuenyo nke vdW heterostructure n'elu ihe ntụgharị Bragg ekesara. N'ihi nlegharị anya dị elu nke onye na-atụgharị Bragg na-ekesa, nke bụ oyi akwa nke ala, mpaghara ọwara dị na onyonyo a nwere ọdịiche dị oke ala, na-eme ka ọ bụrụ naanị oyi akwa hBN dị elu ka a na-ahụ.
Ihe ngosi 1c na-anọchi anya eserese mpaghara vdW nke heterostructure na ọwara geometry n'okpuru nchụpụ. Electroluminescence (EL) na-ahụ n'elu voltaji ọnụ ụzọ mgbe Fermi larịị nke n'elu (ala) graphene gbanwere n'elu (n'okpuru) conduction (valence) band nke WS2, ikwe ka ihe eletrọn (oghere) ka ọwara n'ime conduction (valence) nke WS2. Nke a na-emepụta ọnọdụ dị mma maka nhazi nke excitons na oyi akwa WS2 na-esote radiative (radiative) electron-hole recombination.
N'adịghị ka pn junction light emitters, nke chọrọ doping iji rụọ ọrụ, EL sitere na ngwaọrụ ọwara na-adabere naanị na ọwara ọwara ugbu a, na-ezere mfu ngwa anya na mgbanwe ọ bụla na resistivity kpatara mgbanwe okpomọkụ. N'otu oge ahụ, ihe owuwu ọwara na-enye ohere maka mpaghara ikuku ka ukwuu ma e jiri ya tụnyere ngwaọrụ dichalcogenide dabere na pn junctions.
Image Image 1d na-egosiputa njirimara eletriki nke njupụta nke ọwara ugbu a (J) dị ka ọrụ nke eleghi anya voltaji (V) n'etiti graphene electrodes. Mmụba dị nkọ na nke ugbu a maka ma voltaji dị mma na nke na-adịghị mma na-egosi ihe omume nke tunneling ugbu a site na nhazi ahụ. N'ebe kacha mma nke oyi akwa hBN (~ 2 nm), a na-ahụ nnukwu ọwara mmiri ugbu a yana mmụba na ndụ nke ndị na-ebu agbakwunyere maka nchikota radieshon.
Tupu ịme nnwale electroluminescence, ngwaọrụ ahụ ka ejiri nlegharị anya ọkụ na-acha ọcha na-edozi n'akuku iji gosi na ọnụnọ nke njikọ excitonic siri ike.
Foto #2
Na onyonyo a 2 A na-egosi ụdị nlegharị anya n'akụkụ edoziri site na mpaghara na-arụ ọrụ nke ngwaọrụ ahụ, na-egosipụta omume mgbochi ịgafe. A na-ahụkwa Photoluminescence (PL) n'okpuru mkpali na-adịghị mma (460 nm), na-egosi oke ikuku sitere na alaka polariton dị ala yana ike na-esi na alaka polariton dị elu (2b).
Na 2c na-egosi mgbasasị nke electroluminescence nke polariton na ọnụọgụ ntụtụ nke 0.1 μA/μm2. Nkewa nke Rabi na nchapụta oghere enwetara site na ịkwado ụdị oscillator (ahịrị ọcha siri ike na nke gbajiri agbaji) na nnwale EL bụ 33 meV na ～-13 meV, n'otu n'otu. Akọwapụtara oghere oghere dị ka δ = Ec - Ex, ebe Ex bụ ike exciton na Ec na-egosi ike dị n'ime ụgbọ elu efu-oge oghere ike foton. Nhazi oge 2d Nke a bụ ịkpụ n'akụkụ dị iche iche site na mgbasa electroluminescent. N'ebe a, a na-ahụ anya nke ọma na mgbasa nke ụdị polariton nke elu na nke ala na anticrossing na-eme na mpaghara resonance exciton.
Foto #3
Ka ọwara mmiri na-abawanye, ike EL n'ozuzu na-abawanye. A na-ahụ EL adịghị ike site na polariton n'akụkụ ngbanwe ọnụ ụzọ (3), ebe ọ na-enwe nnukwu nchụpụ n'elu ọnụ ụzọ, ikuku polariton na-adị iche (3b).
Na onyonyo a 3c na-egosi nkata polar nke ike EL dị ka ọrụ nke akụkụ, na-egosipụta cone emission dị warara nke ± 15°. Ụkpụrụ radieshon na-anọgide na-agbanwebeghị maka ma opekempe (ntụgharị akwụkwọ ndụ akwụkwọ ndụ) na nke kachasị (orange curve) mkpali ugbu a. Gbanye 3d na-egosi ike agbakwunyere maka ọwara mmiri dị iche iche na-akpụ akpụ, nke, dịka enwere ike ịhụ site na eserese ahụ, dị larịị. Ya mere, ịba ụba nke ugbu a gaa n'ụkpụrụ dị elu nwere ike iduga na-agbasasị nke ọma nke polaritons n'akụkụ alaka nke ala ma mepụta usoro ikuku dị warara nke ukwuu n'ihi ọgbọ polariton. Otú ọ dị, na nnwale a, ọ gaghị ekwe omume ime nke a n'ihi njedebe nke jikọtara ya na nkwụsịtụ dielectric nke hBN tunnel barrier.
ntụpọ uhie na 3d gosi nha nke ihe ngosi ọzọ - mpụga arụmọrụ quantum*.
Nrụmọrụ quantum* - ọnụ ọgụgụ nke ọnụ ọgụgụ nke photons, absorption nke mere ka e guzobe nke quasiparticles, na ngụkọta ọnụ ọgụgụ nke etinye obi gị dum photons.
Arụmọrụ quantum a na-ahụ anya bụ nke a na-atụnyere na LEDs polariton ndị ọzọ (dabere na akụrụngwa organic, tubes carbon, wdg). Ọ dị mma ịmara na na ngwaọrụ a na-amụ na ọkpụrụkpụ nke oyi akwa na-egbuke egbuke bụ naanị 0.7 nm, ebe na ngwaọrụ ndị ọzọ uru a dị elu karị. Ndị ọkà mmụta sayensị anaghị ezobe eziokwu ahụ bụ na arụmọrụ nke akụrụngwa ha abụghị nke kachasị elu, mana enwere ike ịbawanye ya site na itinye ọnụ ọgụgụ buru ibu nke monolayers n'ime mpaghara ọwara, kewapụrụ site na obere oyi akwa nke hBN.
Ndị nchọpụta ahụ nwalekwara mmetụta nke resonator detuning na polariton EL site n'ịme ngwaọrụ ọzọ, ma na-eji ike siri ike (-43 meV).
Foto #4
Na onyonyo a 4 EL spectra nwere mkpebi angular nke ngwaọrụ dị otú ahụ na njupụta ugbu a nke 0.2 μA/μm2. N'ihi nhụsianya siri ike, ngwaọrụ ahụ na-egosipụta mmetụta ọkpọ ọkpọ akpọpụtara na EL yana oke ikuku na-eme na nnukwu akụkụ. Ekwupụtakwara nke a na onyonyo a 4b, ebe atụnyere polar graphs nke ngwaọrụ a na nke mbụ (2c).
Maka ịmatakwu nke ọma na nuances nke ọmụmụ ihe, ana m akwado ile anya .
Epilogue
Ya mere, nleba anya na nha niile akọwara n'elu na-akwado ọnụnọ nke electroluminescence polariton na vdW heterostructure wuru n'ime microcavity anya. Ihe owuwu ọwara nke ngwaọrụ a na-amụ na-eme ka iwebata electrons/oghere na recombination na WS2 monolayer, nke na-eje ozi dị ka ọkụ emitter. Ọ dị mkpa na usoro ọwara nke ngwaọrụ ahụ anaghị achọ ichikota akụkụ, nke na-ebelata mfu na mgbanwe dị iche iche nke okpomọkụ.
Achọpụtara na EL nwere ntụziaka dị elu n'ihi mgbasa nke resonator. Ya mere, imeziwanye ihe dị mma nke oghere na nnyefe dị elu ugbu a ga-eme ka arụmọrụ nke microcavity LEDs, yana microcavity polaritons na-achịkwa ọkụ eletrik na laser photonic.
Ọrụ a kwadoro ọzọ na metal dichalcogenides mgbanwe nwere ihe pụrụ iche n'ezie na ọtụtụ ngwa ngwa.
Nchọpụta dị otú ahụ na mmepụta ihe ọhụrụ nwere ike imetụta mmepe na mgbasa nke teknụzụ nnyefe data site na iji LED na ọkụ n'onwe ya. Teknụzụ ọdịnihu dị otú ahụ gụnyere Li-Fi, nke nwere ike inye ọsọ ọsọ dị elu karịa Wi-Fi dị ugbu a.
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