Dukoresha spectroscopy ya photoemission ishingiye ku gihe n'inguni (tr-ARPES) kugira ngo dukore ubushakashatsi ku ihererekanya ry'amashanyarazi ryihuse cyane mu buryo bwa heterostructure ya epitaxial ikozwe muri monolayer WS2 na graphene. Ubu buryo bwa heterostructure buhuza ibyiza bya semiconductor ifite icyuho gikomeye hamwe n'imikoranire ikomeye ya spin-orbit hamwe n'imikoranire ikomeye y'urumuri n'iby'ibikoresho bitagira ingano bifite ubushobozi bwo kugenda cyane kandi bimara igihe kirekire. Twasanze, nyuma yo gushyushya kuri photoexciton kuri resonance kuri A-exciton muri WS2, imyobo ya photoexcited yimukira vuba mu buryo bwa graphene mu gihe electron za photoexcited ziguma mu buryo bwa WS2. Imiterere y'igihe gito ivamo charge-diparated yabonetse yasanze ifite igihe cy'ubuzima cya ~1 ps. Twavuze ko ibyo twabonye biterwa n'itandukaniro mu mwanya wa scattering phase riterwa no guhuza WS2 na graphene bands nk'uko byagaragajwe na ARPES ifite ubushobozi bwo hejuru. Hamwe na spin-selective optical excitation, WS2/graphene heterostructure yakoreweho ubushakashatsi ishobora gutanga urubuga rwo gushyira optique spin muri graphene neza.
Kuba hari ibikoresho byinshi bitandukanye bifite imiterere ibiri byatumye habaho uburyo bwo gukora imiterere mishya y’uruhererekane rw’amashanyarazi hamwe n’imikorere mishya ishingiye ku gusuzuma amashanyarazi mu buryo bwa dielectric hamwe n’ingaruka zitandukanye ziterwa no kwegereza (1–3). Ibikoresho bihamya amahame ngenderwaho yo gukoreshwa mu gihe kizaza mu bijyanye n’ikoranabuhanga n’ikoranabuhanga rya optoelectronics byagezweho (4–6).
Aha, twibanda ku miterere ya heterostructures ya epitaxial van der Waals igizwe na monolayer WS2, semiconductor ifite icyuho gikomeye hamwe n’ihindagurika rikomeye ry’imiterere y’umugozi bitewe n’ihindagurika rya inversion symmetry (7), na monolayer graphene, semimetal ifite imiterere ya conical band hamwe n’uburyo bwo gutwara ibintu bwinshi cyane (8), ikura kuri hydrogen-terminated SiC (0001). Ibimenyetso bya mbere byo kohereza charge yihuta cyane (9–15) hamwe n’ingaruka zo guhuza spin-orbit (16–18) bituma WS2/graphene n’imiterere isa nayo itera inkunga abakandida bazakoreshwa mu gihe kizaza mu buryo bwa optoelectronic (19) na optospintronic (20).
Twatangiye kugaragaza inzira zo kuruhuka z’ibice bibiri bya electron-hole bikozwe na photoelectron muri WS2/graphene hamwe na spectroscopy ya photoemission ifite igihe n’inguni (tr-ARPES). Muri iyo ntego, dushishikariza heterostructure dukoresheje 2-eV pump pulses zihuza na A-exciton muri WS2 (21, 12) hanyuma tugasohora photoelectrons dukoresheje pulse ya probe yatinze gusubikwa ku ngufu za photon za 26-eV. Tugena ingufu za kinetic n’inguni y’ibyuka bya photoelectrons dukoresheje hemispherical analyzer nk'igikorwa cyo gutinda kwa pompe-probe kugira ngo tubone uburyo bwo gufata momentum-, energy-, na time-resolved carrier dynamics. Ingufu n’igihe ni 240 meV na 200 fs, uko bikurikirana.
Ibisubizo byacu bitanga ibimenyetso bitaziguye by’uko amashanyarazi yihuta cyane hagati y’imiterere y’impande zombi, byemeza ibimenyetso bya mbere bishingiye ku buhanga bwose bw’izuba mu miterere isa n’iy’izuba yakusanyijwe n’intoki hamwe n’imiterere y’imiterere y’imiterere y’izuba (9-15). Byongeye kandi, tugaragaza ko iyi miterere y’amashanyarazi idahuje cyane. Ibipimo byacu bigaragaza imiterere y’izuba itagaragara mbere y’aho amashanyarazi atandukanyijwe n’izuba hamwe n’imyenge n’imyobo iri mu cyiciro cya WS2 na graphene, uko bikurikirana, ikaba imara kuri 0.1 ps. Dusobanura ibyo twabonye mu buryo butandukanye mu mwanya w’izuba ry’izuba ry’izuba ry’izuba ry’izuba n’imyobo bitewe n’imiterere y’imirongo ya WS2 na graphene nk’uko byagaragajwe na ARPES ifite ubushobozi bwo hejuru. Hamwe n’izuba ry’izuba n’iry’izuba (22-25) imiterere y’izuba rya WS2/graphene ishobora gutanga urubuga rushya rwo gushyiramo amashanyarazi yihuta cyane muri graphene.
Ishusho ya 1A igaragaza igipimo cya ARPES cyo hejuru cyabonetse hakoreshejwe itara rya helium ry’imiterere y’umugozi ku cyerekezo cya ΓK cy’imiterere ya heterostructure ya epitaxial WS2/graphene. Umugozi wa Dirac uboneka ko ufite umwobo aho Dirac iherereye kuri ~0.3 eV hejuru y’ubushobozi bwa equilibrium chemical. Igice cyo hejuru cy’umugozi wa WS2 valence ugaragara ko kiri kuri ~1.2 eV munsi y’ubushobozi bwa equilibrium chemical.
(A) Umuvuduko w'ifoto upima mu cyerekezo cya ΓK hakoreshejwe itara rya helium ridafite polarized. (B) Umuvuduko w'ifoto upima gutinda kwa pompe-probe hapimwa hakoreshejwe imirasire ya ultraviolet ya p-polarized extreme ultraviolet kuri energy ya fotoni ya 26-eV. Imirongo y'imvi n'umutuku iragaragaza aho umurongo uherereye ukoreshwa mu gukuramo imyanya y'impeshyi y'igihe gito ku Ishusho ya 2. (C) Impinduka za pompe-photocurrent 200 fs nyuma yo gushyuha ku ngufu za pompe ya fotoni ya 2 eV hamwe n'umuvuduko wa pompe ya 2 mJ/cm2. Kuzamuka no gutakaza kwa photoelectron bigaragazwa mu ibara ry'umutuku n'ubururu, uko bikurikirana. Udusanduku tugaragaza agace k'aho pompe-probe ihurira n'imirongo igaragara ku Ishusho ya 3.
Ishusho ya 1B yerekana ishusho ya tr-ARPES y'imiterere y'umugozi hafi ya WS2 na graphene K-points bipimwe hakoreshejwe 100-fs extreme ultraviolet pulses kuri 26-eV photon energy kuri negative pump-probe delay mbere yuko pump pulse igera. Aha, gucikamo ibice ntibikemuka bitewe no kwangirika kw'icyitegererezo no kuba hari 2-eV pump pulse ituma imiterere ya spectral yaguka. Ishusho ya 1C igaragaza impinduka zatewe na pump ku muvuduko wa photocurrent ugereranije n'Ishusho ya 1B kuri 200 fs aho pump-probe signal igera ku rugero ntarengwa. Amabara y'umutuku n'ubururu agaragaza kwiyongera no gutakaza kwa photoelectron, uko bikurikirana.
Kugira ngo dusesengure iyi mikorere irambuye, tubanza kumenya aho umurongo wa WS2 valence band na graphene π-band iherereye ku mirongo iciye ku ishusho ya 1B nk'uko byasobanuwe mu buryo burambuye mu bikoresho by'inyongera. Dusanga umurongo wa WS2 valence uzamukaho meV 90 (Ishusho ya 2A) naho umurongo wa graphene π-band umanukaho meV 50 (Ishusho ya 2B). Igihe cy'uburambe bw'izi mpinduka cyagaragaye ko ari 1.2 ± 0.1 ps kuri valence band ya WS2 na 1.7 ± 0.3 ps kuri graphene π-band. Izi mpinduka zitanga ikimenyetso cya mbere cy'ubushyuhe bw'igihe gito bw'ibice bibiri, aho charge y'inyongera (negative) yongera (igabanya) ingufu zo gufatanya z'imiterere y'ikoranabuhanga. Menya ko kuzamuka k'umurongo wa WS2 valence band ari byo bituma ikimenyetso cya pompe-probe kigaragara mu gace kagaragajwe n'agasanduku k'umukara ku ishusho ya 1C.
Impinduka mu mwanya w’agace k’umugozi wa WS2 valence (A) na graphene π-band (B) nk’uko bigenda ku gutinda kwa pompe-probe hamwe n’impinduka za exponential (imirongo minini). Igihe cy’impinduka ya WS2 muri (A) ni 1.2 ± 0.1 ps. Igihe cy’impinduka ya graphene muri (B) ni 1.7 ± 0.3 ps.
Hanyuma, duhuza ikimenyetso cya pompe-probe ku bice byerekanwe n'udusanduku tw'amabara ku Ishusho ya 1C hanyuma tugashushanya imibare yavuyemo nk'igikorwa cyo gutinda kwa pompe-probe ku Ishusho ya 3. Umurongo wa 1 ku Ishusho ya 3 werekana imiterere y'ibitwara umwuka bifotora hafi y'igice cyo hasi cy'umurongo w'amashanyarazi w'urwego rwa WS2 hamwe n'ubuzima bwa 1.1 ± 0.1 ps byabonetse bivuye ku guhuza amakuru n'amakuru (reba Ibikoresho by'inyongera).
Ibimenyetso bya pompe-probe nk'igikorwa cyo gutinda kuboneka binyuze mu guhuza umuyoboro w'amashanyarazi ku gace kagaragajwe n'udusanduku turi ku Ishusho ya 1C. Imirongo minini ihuye n'amakuru. Umuyoboro (1) Umubare w'abantu batwara igihe gito mu gice cyo kuyobora cy'amashanyarazi cya WS2. Umuyoboro (2) Ikimenyetso cya pompe-probe cy'umuyoboro wa π wa graphene hejuru y'ubushobozi bwa shimi bwo kuringaniza. Umuyoboro (3) Ikimenyetso cya pompe-probe cy'umuyoboro wa π wa graphene munsi y'ubushobozi bwa shimi bwo kuringaniza. Umuyoboro (4) Ikimenyetso cya pompe-probe cy'ukuri mu gice cyo kuringaniza cy'amashanyarazi cya WS2. Igihe cy'ubuzima kiboneka ari 1.2 ± 0.1 ps muri (1), 180 ± 20 fs (inyungu) na ∼2 ps (igihombo) muri (2), na 1.8 ± 0.2 ps muri (3).
Mu mirongo ya 2 na 3 by'Ishusho ya 3, tugaragaza ikimenyetso cya pompe-probe cya graphene π-band. Twasanze inyungu ya electron hejuru y'ubushobozi bwa equilibrium chemical (ishusho ya 2 mu Ishusho ya 3) ifite igihe gito cyane cy'ubuzima (180 ± 20 fs) ugereranije n'igihombo cya electron munsi y'ubushobozi bwa equilibrium chemical (1.8 ± 0.2 ps mu murongo wa 3). Byongeye kandi, inyungu ya mbere y'umuyoboro wa photocurrent mu murongo wa 2 w'Ishusho ya 3 ihinduka igihombo kuri t = 400 fs hamwe n'igihe cy'ubuzima cya ~ 2 ps. Ubusumbane hagati y'ubwiyongere n'igihombo bugaragara ko butaboneka mu kimenyetso cya pompe-probe cya graphene y'urubara rudafite uruvange (reba ishusho ya S5 mu bikoresho by'inyongera), bigaragaza ko ubusumbane ari ingaruka zo guhuza hagati y'urubara mu miterere ya WS2/graphene. Kubona inyungu y'igihe gito n'igihombo cy'igihe kirekire kiri hejuru no munsi y'ubushobozi bwa elegitoroniki, bigaragaza ko elektroni zikurwa neza mu cyiciro cya graphene iyo habayeho gushyuha kw'imiterere ya heterostructure. Kubera iyo mpamvu, urwego rwa graphene ruhinduka positive chaji, ibi bikaba bihuye n'ubwiyongere bw'ingufu zo gufatana kwa π-band ziboneka ku Ishusho ya 2B. Guhindagurika kwa π-band bikuraho umurizo w'ingufu nyinshi z'ikwirakwizwa rya egitoroniki rya Fermi-Dirac hejuru y'ubushobozi bwa elegitoroniki, ibi bikaba bisobanura igice cy'impinduka z'ikimenyetso cya pompe-probe mu murongo wa 2 w'Ishusho ya 3. Tuzagaragaza hepfo ko iyi ngaruka irushaho kwiyongera no gutakaza by'igihe gito kwa elektroni muri π-band.
Iyi mimerere ishyigikiwe n'ikimenyetso cya pompe-probe cy'umurongo wa valence wa WS2 mu murongo wa 4 w'Ishusho ya 3. Aya makuru yabonetse binyuze mu guhuza imibare ku gace katanzwe n'agasanduku k'umukara ku Ishusho ya 1B gafata electrons foto zisohoka mu murongo wa valence mu gihe cyose pompe-probe itinze. Mu mirongo y'ikosa ry'igerageza, nta kimenyetso tubona cyerekana ko hari imyobo mu murongo wa valence wa WS2 ku gutinda kwa pompe-probe. Ibi bigaragaza ko, nyuma yo gushyuha, iyi myobo yuzura vuba mu gihe gito ugereranije n'igihe twabonye.
Kugira ngo dutange igihamya cya nyuma cy’igitekerezo cyacu cyo gutandukanya ingufu zihuta cyane mu miterere ya WS2/graphene, tumenya umubare w’imyobo yimuwe ku rwego rwa graphene nk’uko byasobanuwe mu buryo burambuye mu bikoresho by’inyongera. Muri make, ikwirakwizwa ry’amashanyarazi ry’igihe gito rya π-band ryashyizwemo ikwirakwizwa rya Fermi-Dirac. Umubare w’imyobo wabaye ubazwe uhereye ku gaciro kavuyemo k’ubushobozi bw’ingufu zihoraho n’ubushyuhe bw’amashanyarazi. Ibisubizo bigaragara ku Ishusho ya 4. Twasanze umubare wose w’imyobo ∼5 × 1012 / cm2 wimuwe kuva kuri WS2 ukajya kuri graphene ufite ubuzima bwa exponential bwa 1.5 ± 0.2 ps.
Ihinduka ry'umubare w'imyobo iri mu gice cya π nk'igikorwa cyo gutinda kwa pompe hamwe no gukwirakwira kwa exponential bitanga ubuzima bwa 1.5 ± 0.2 ps.
Mu byavumbuwe ku mashusho ya 2 kugeza kuri 4, hagaragara ishusho ikurikira ya mikorosikopi y’uburyo bwo kohereza ingufu mu buryo bwihuse muri heterostructure ya WS2/graphene (Ishusho ya 5). Gutuma WS2/graphene heterostructure ikora kuri 2 eV byuzuyemo cyane A-exciton muri WS2 (Ishusho ya 5A). Inyongera z’ibishyushya mu buryo bw’ikoranabuhanga ku gice cya Dirac muri graphene ndetse no hagati ya WS2 na graphene bands zirashoboka ariko ntizikora neza cyane. Utwobo dushyushya mu gice cya valence cya WS2 twuzura na electrons zikomoka kuri graphene π-band ku gipimo cy’igihe gito ugereranije n’igihe cyacu cyo gusubiza (Ishusho ya 5A). Electrons zishyushya mu gice cya conduction cya WS2 zifite igihe cy’ubuzima cya ∼1 ps (Ishusho ya 5B). Ariko, bisaba ∼2 ps kugira ngo wongere utwobo muri graphene π-band (Ishusho ya 5B). Ibi bigaragaza ko, uretse kohereza electron mu buryo butaziguye hagati y’umurongo wa WS2 uyobora amashanyarazi n’umurongo wa graphene π, hari izindi nzira zo kuruhuka—bishoboka ko zinyura mu mimerere y’ubusembwa (26)—zigomba gusuzumwa kugira ngo dusobanukirwe imiterere yuzuye.
(A) Gutuma urumuri ruzamuka mu kirere (photoexciton) kuri WS2 A-exciton kuri 2 eV bitera electron mu gice cyo kuyobora cy’amashanyarazi cya WS2. Utwobo duhuye na two mu gice cyo kuyobora cy’amashanyarazi cya WS2 twongerwamo ako kanya na electron zo mu gice cyo kuyobora cy’amashanyarazi cya graphene π. (B) Utwobo dutwara urumuri ruzamuka mu gice cyo kuyobora cy’amashanyarazi cya WS2 dufite igihe cy’ubuzima bwa ∼1 ps. Utwobo turi mu gice cyo kuyobora cy’amashanyarazi cya graphene π tubaho ∼2 ps, bigaragaza akamaro k’inyongera zo gukwirakwiza zigaragazwa n’imyambi yaciwe. Imirongo y’umukara yaciwe muri (A) na (B) igaragaza impinduka mu gice cyo kuyobora n’impinduka mu bushobozi bwa shimi. (C) Mu gihe cy’impinduka, urwego rwa WS2 rushyushwa nabi mu gihe urwego rwa graphene rufite amashanyarazi meza. Ku bijyanye no gukurura urumuri ruzunguruka hamwe n’urumuri rwazunguruka, electron zaciwe muri WS2 n’utwobo duhuye na two muri graphene byitezwe ko bigaragaza polarisation inyuranye.
Mu gihe cy'igihe gito, electron zishyushye ziba mu gice cy'umuyoboro wa WS2 mu gihe imyobo ishyushye iba mu gice cy'umuyoboro wa π cya graphene (Ishusho ya 5C). Ibi bivuze ko urwego rwa WS2 rufite ingufu nke kandi urwego rwa graphene rufite ingufu nziza. Ibi bikubiyemo impinduka z'igihe gito (Ishusho ya 2), kudahuza kw'ikimenyetso cya graphene pump-probe (impande ya 2 na 3 z'Ishusho ya 3), kutagira imyobo mu gice cy'umuyoboro wa valence cya WS2 (impande ya 4 Ishusho ya 3), ndetse n'imyobo y'inyongera mu gice cy'umuyoboro wa graphene π (Ishusho ya 4). Igihe cy'ubuzima cy'iyi mimerere itandukanye ni ∼1 ps (impande ya 1 Ishusho ya 3).
Imiterere nk'iyi y'igihe gito itandukanyijwe n'amashanyarazi yagaragaye mu miterere ya van der Waals igizwe na semiconductor ebyiri zifite imiterere y'umugozi umwe (direct-gap) hamwe n'umugozi umwe (staggered band gap) (27-32). Nyuma yo gushyushya urumuri, byagaragaye ko electrons n'imyobo byimuka vuba cyane mu gice cyo hasi cy'umugozi umwe no hejuru y'umugozi umwe (valence band), biri mu byiciro bitandukanye by'umugozi umwe (27-32).
Ku bijyanye n'imiterere yacu ya WS2/graphene, ahantu heza cyane ho gukoresha ingufu haba kuri electron n'imyobo ni ku rwego rwa Fermi mu gice cya graphene cy'icyuma. Kubwibyo, umuntu yakwitega ko electron n'imyobo byombi byimukira vuba kuri graphene π-band. Ariko, ibipimo byacu bigaragaza neza ko kwimura imyobo (<200 fs) ari byiza cyane kuruta kwimura electron (∼1 ps). Ibi tubishingira ku guhuza ingufu kwa WS2 n'imirongo ya graphene nk'uko byagaragajwe ku Ishusho ya 1A itanga umubare munini w'imiterere ya nyuma iboneka yo kwimura imyobo ugereranije no kwimura electron nk'uko byari byitezwe vuba aha na (14, 15). Muri iki gihe, dufashe ko hari ∼2 eV WS2 bandgap, graphene Dirac point na equilibrium chemical potential biri kuri ∼0.5 na ∼0.2 eV hejuru y'igice cya WS2 bandgap, uko bikurikirana, bigaca symmetry ya electron-hole. Twasanze umubare w'imiterere ya nyuma ihari yo kohereza imyobo ari munini inshuro zigera kuri ∼6 ugereranyije no kohereza electron (reba Ibikoresho by'inyongera), ari nayo mpamvu kohereza imyobo byitezwe ko bizarushaho kwihuta kurusha kohereza electron.
Ishusho yuzuye ya mikorosikopi y’iyimurwa ry’amashanyarazi ritagenda neza cyane ryagaragaye, ariko, rigomba no gusuzuma isano iri hagati y’imirongo igize imikorere y’umuraba wa A-exciton muri WS2 na graphene π-band, uko bikurikirana, imiyoboro itandukanye ya electron-electron na electron-phononi irimo inzitizi zishyirwaho n’umuvuduko, ingufu, spin, na pseudospin, ingaruka za plasma oscillations (33), ndetse n’uruhare rw’ihindagurika rishoboka ry’ihindagurika rya phononi rishobora kuba rihuza iyimurwa ry’amashanyarazi (34, 35). Nanone, umuntu ashobora gutekereza niba imiterere y’iyimurwa ry’amashanyarazi ryagaragaye igizwe na excitons zo kwimura umuriro cyangwa pairs za electron-hole zigenga (reba Ibikoresho by’inyongera). Hakenewe ubundi bushakashatsi bw’imitekerereze burenze urugero rw’iyi nyandiko kugira ngo busobanure neza ibi bibazo.
Muri make, twakoresheje tr-ARPES kugira ngo twige uburyo bwo kohereza amashanyarazi mu buryo bwa ultrafast interlayer muri heterostructure ya epitaxial WS2/graphene. Twasanze, iyo habayeho gukururwa na A-exciton ya WS2 kuri 2 eV, imyobo ishyushye yimukira vuba mu cyiciro cya graphene mu gihe electron zishyushye ziguma mu cyiciro cya WS2. Twavuze ko ibi biterwa n'uko umubare w'imiterere ya nyuma iboneka yo kohereza imyobo ari munini kuruta iyo kohereza electron. Igihe cy'ubuzima cya charge-separated transient state cyagaragaye ko ari ∼1 ps. Hamwe n'ingufu zitoranya spin optical hakoreshejwe urumuri ruzunguruka (22-25), iyo kohereza amashanyarazi mu buryo bwa ultrafast charge yagaragaye ishobora guherekezwa no kohereza spin. Muri iki gihe, heterostructure ya WS2/graphene yasuzumwe ishobora gukoreshwa mu gushyira spin optique neza muri graphene bigatuma habaho ibikoresho bishya bya optospinttronic.
Ingero za graphene zahinzwe ku macupa ya 6H-SiC (0001) acuruza ibikoresho by’ubucuruzi bya SiCrystal GmbH. Amacupa ya N-doped yari ku murongo umwe afite icyuho kiri munsi ya 0.5°. Substrate ya SiC yakuweho hydrogen kugira ngo ikureho iminkanyari no kubona amaterasi asanzwe. Ubuso bwa Si-busukuye kandi butambitse bwashyizwemo atome bwashyizwemo graphite binyuze mu gukurura ingero mu kirere cya Ar kuri 1300°C mu gihe cy'iminota 8 (36). Muri ubu buryo, twabonye urwego rumwe rwa karuboni aho buri atome ya karuboni ya gatatu yakoraga umugozi wa covalent kuri substrate ya SiC (37). Uru rwego rwahinduwe graphene yuzuye ya sp2-hybrided quasi free-standing hole-doped graphene binyuze mu gukwirakwiza hydrogen (38). Izi ngero zitwa graphene/H-SiC (0001). Igikorwa cyose cyakorewe mu cyumba cy’ubucuruzi cya Black Magic gikuramo Aixtron. Iterambere rya WS2 ryakozwe mu cyuma gishyushya gisanzwe hakoreshejwe umwuka w’ubushyuhe buke (39, 40) hakoreshejwe ifu ya WO3 na S ifite igipimo cy’uburemere cya 1:100 nk’ibibanziriza. Ifu ya WO3 na S yabitswe kuri dogere selisiyusi 900 na 200. Ifu ya WO3 yashyizwe hafi y’aho iherereye. Argon yakoreshejwe nk'umwuka utwara ibintu ufite umuvuduko wa cm 8. Umuvuduko muri icyo cyuma wabitswe kuri 0.5 mbar. Ingero zagaragajwe hakoreshejwe mikorosikopi ya elegitoroni ya kabiri, mikorosikopi ya atome, Raman, na spectroscopy ya photoluminescence, ndetse na diffraction ya elegitoroni ifite ingufu nke. Ibi bipimo byagaragaje uturere tubiri dutandukanye twa WS2 tw’ubutare bumwe aho icyerekezo cya ΓK- cyangwa ΓK' gihujwe n’icyerekezo cya ΓK cy’urwego rwa graphene. Uburebure bw'impande z'aho ibintu biherereye bwari hagati ya nanometero 300 na 700, kandi ubwinshi bw'ubuso bwa WS2 bwageraga kuri 40%, bukwiriye isesengura rya ARPES.
Igerageza rya ARPES rihoraho ryakozwe hifashishijwe isesengura rya hemispherical (SPECS PHOIBOS 150) hakoreshejwe sisitemu yo gupima amashanyarazi ihuza ibikoresho kugira ngo hamenyekane ingufu za electron n'umuvuduko w'amashanyarazi. Imirasire ya He Iα idafite polarized, monochromatic (21.2 eV) y'isoko rya He risohora amashanyarazi menshi (VG Scienta VUV5000) yakoreshejwe mu igerageza ryose rya photoemission. Ingufu n'imiterere y'inguni mu igerageza ryacu byari byiza kurusha 30 meV na 0.3° (bihwanye na 0.01 Å−1), uko bikurikirana. Igerageza ryose ryakozwe ku bushyuhe bw'icyumba. ARPES ni uburyo bworoshye cyane bwo kwihuta ku buso. Kugira ngo hasohorwe photoelectron muri WS2 no muri graphene layer, hakoreshejwe ingero zifite WS2 idahagije ya ∼40%.
Imiterere ya tr-ARPES yari ishingiye kuri amplifier ya 1-kHz Titanium:Sapphire (Coherent Legend Elite Duo). Ingufu za 2 mJ zo gusohora zakoreshejwe mu gukora harmonics nyinshi muri argon. Urumuri rwinshi rwa ultraviolet rwavuyemo rwanyuze muri monochromator ya grating ikora pulses za probe za 100-fs kuri energy ya photon ya 26-eV. Ingufu za 8mJ zo gusohora amplifier zoherejwe muri amplifier ya optique parametric (HE-TOPAS iturutse ku Guhindura Umucyo). Umurabyo w'ikimenyetso kuri 1-eV energy ya photon wikubye kabiri muri crystal ya beta barium borate kugira ngo haboneke pulses za pompe ya 2-eV. Ibipimo bya tr-ARPES byakozwe hifashishijwe hemispherical analyzer (SPECS PHOIBOS 100). Ingufu zose hamwe n'ingufu byari 240 meV na 200 fs, uko bikurikirana.
Ibikoresho by'inyongera kuri iyi nkuru biraboneka kuri http://advances.sciencemag.org/cgi/content/full/6/20/eaay0761/DC1
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Bya Sven Aeschlimann, Antonio Rossi, Mariana Chávez-Cervantes, Razvan Krause, Benito Arnoldi, Benjamin Stadtmüller, Martin Aeschlimann, Stiven Forti, Filippo Fabbri, Camilla Coletti, Isabella Gierz
Twagaragaje ko gutandukanya amashanyarazi yihuta cyane mu buryo bwa WS2/graphene bishobora gutuma graphene ishyirwamo optique spin.
Bya Sven Aeschlimann, Antonio Rossi, Mariana Chávez-Cervantes, Razvan Krause, Benito Arnoldi, Benjamin Stadtmüller, Martin Aeschlimann, Stiven Forti, Filippo Fabbri, Camilla Coletti, Isabella Gierz
Twagaragaje ko gutandukanya amashanyarazi yihuta cyane mu buryo bwa WS2/graphene bishobora gutuma graphene ishyirwamo optique spin.
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Igihe cyo kohereza: Gicurasi-25-2020