Sisebenzisa i-photoemission spectroscopy yexesha kunye ne-angle-esonjululwe (i-tr-ARPES) ukuphanda ukudluliselwa kwentlawulo ye-ultrafast kwi-epitaxial heterostructure eyenziwe nge-monolayer WS2 kunye negraphene. Le heterostructure idibanisa izibonelelo ze-semiconductor ene-gap eyomeleleyo kunye ne-spin-orbit coupling eyomeleleyo kunye nentsebenziswano enamandla yokukhanya kunye nezo ze-semimetal hosting massless carriers kunye nokuhamba okuphezulu kakhulu kunye nexesha elide lokujikeleza. Sifumanisa ukuba, emva kwe-photoexcitation kwi-resonance kwi-A-exciton kwi-WS2, imingxuma e-photoexcited idlulisela ngokukhawuleza kwi-graphene layer ngelixa i-electronics photoexcited ihlala kwi-WS2 layer. Isiphumo sentlawulo-yahlulwe imeko yexeshana ifunyenwe inobomi obuyi-∼1 ps. Sifaka iziphumo zethu kumahluko kwisithuba sesigaba sokusasazwa okubangelwa kukulungelelaniswa okunxulumene ne-WS2 kunye neebhendi zegraphene njengoko kutyhilwe yi-ARPES enesisombululo esiphezulu. Ngokudityaniswa ne-spin-selective optical excitation, i-WS2/graphene heterostructure ephandiweyo inokubonelela ngeqonga lenaliti ye-optical spin esebenzayo kwigraphene.
Ubukho bezinto ezininzi ezahlukeneyo ezine-dimensional dimensional kuvule ithuba lokudala inoveli ekugqibeleni i-heterostructures ebhityileyo enokusebenza okutsha ngokupheleleyo okusekwe kuvavanyo olulungiselelweyo lwe-dielectric kunye neziphumo ezahlukeneyo ezibangelwa ukusondela (1-3). Izixhobo zobungqina bomgaqo-siseko kwizicelo ezizayo kwintsimi ye-electronics kunye ne-optoelectronics ziye zaqatshelwa (4-6).
Apha, sigxila kwi-epitaxial van der Waals heterostructures ebandakanya i-monolayer WS2, i-semiconductor ye-gap ethe ngqo ene-spin-orbit coupling eyomeleleyo kunye nokwahlulwa okukhulu kwesakhiwo sebhendi ngenxa ye-symmetry inversion eyaphukileyo (7), kunye ne-monolayer graphene, isemimetal. kunye nesakhiwo se-conical band kunye nokuhamba okuphezulu kakhulu kwe-carrier (8), ekhuliswe kwi-hydrogen-terinated SiC (0001). Izibonakaliso zokuqala zokudluliselwa kwentlawulo ye-ultrafast (9-15) kunye ne-proximity-induced spin-orbit coupling effects (16-18) yenza i-WS2 / graphene kunye ne-heterostructures efanayo ethembisa abaviwa kwixesha elizayo le-optoelectronic (19) kunye ne-optospintronic (20) izicelo.
Sizimisele ukuveza iindlela zokuphumla ze-photogenerated electron-hole pairs in WS2/graphene with time- and angle-resolved photoemission spectroscopy (tr-ARPES). Ngaloo njongo, sivuyisa i-heterostructure kunye ne-2-eV pump pulses resonant to A-exciton kwi-WS2 (21, 12) kunye nokukhupha i-photoelectrons kunye ne-probe ye-probe pulse okwesibini kwi-26-eV yamandla e-photon. Simisela amandla e-kinetic kunye ne-emission angle ye-photoelectrons nge-analyzer ye-hemispherical njengomsebenzi wokulibaziseka kwempompo-probe ukufumana ukufikelela kwi-momentum-, amandla-, kunye ne-carrier-resolved carrier dynamics. Amandla kunye nexesha lesisombululo yi-240 meV kunye ne-200 fs, ngokulandelanayo.
Iziphumo zethu zibonelela ngobungqina obuthe ngqo bokudluliselwa kwentlawulo ye-ultrafast phakathi kwe-epitaxially aligned layers, eqinisekisa izibonakaliso zokuqala ezisekelwe kubuchule be-optical all in the manually assembled heterostructures kunye nokulungelelaniswa kwe-azimuthal engafanelekanga yeeleyile (9-15). Ukongeza, sibonisa ukuba olu tshintsho lwentlawulo lune-asymmetric ephezulu. Imilinganiselo yethu iveza imo edlulayo ebingajongwanga ngaphambili, enee-electron ezinephotoexcited kunye nemingxunya ebekwe kwi-WS2 kunye negraphene layer, ngokulandelelanayo, ehlala ~1 ps. Sitolika iziphumo zethu ngokweyantlukwano kwisithuba sesigaba sokusasaza kwi-electron kunye nokudluliselwa komngxuma okubangelwa ukulungelelaniswa kwe-WS2 kunye neebhendi zegraphene njengoko kutyhilwa yi-ARPES ephezulu. Idityaniswe ne-spin- kunye ne-valley-selective optical excitation (22–25) i-WS2/graphene heterostructures inokubonelela ngeqonga elitsha le-ultrafast optical spin injection kwigraphene.
Umzobo 1A ubonisa umlinganiselo ophezulu we-ARPES ofunyenwe ngesibane se-helium yesakhiwo sebhendi ecaleni kwe-ΓK-direction of the epitaxial WS2/graphene heterostructure. I-cone ye-Dirac ifunyenwe i-hole-doped kunye ne-Dirac point ebekwe ~ 0.3 eV ngaphezu kwe-equilibrium chemical potential. Umphezulu we-spin-split WS2 ibhendi yevalence ifunyenwe ~1.2 eV ngaphantsi kwesakhono sekhemikhali esilinganayo.
(A) Ulungelelwaniso lwefotocurrent lulinganiswe ecaleni kwe-ΓK-direction kunye nesibane se-helium esingenampolar. (B) I-Photocurrent ye-negative pump-probe ulibaziseko olulinganiswe ne-p-polarized extreme ultraviolet pulses kwi-26-eV photon energy. Imigca egreyi kunye nebomvu edayiweyo iphawula indawo yeeprofayili zomgca ezisetyenziselwa ukukhupha izikhundla zencopho ezidlulayo kwiFig. ye 2 mJ/cm2. Ukuzuza kunye nokulahlekelwa kwee-photoelectrons kuboniswe ngobomvu kunye nohlaza okwesibhakabhaka, ngokulandelanayo. Iibhokisi zibonisa indawo yokudibanisa kwimpompo-probe traces eboniswe kwi-Fig.
Umzobo we-1B ubonisa umfanekiso we-tr-ARPES wesakhiwo sebhendi esikufutshane ne-WS2 kunye negraphene K-points ezilinganiswe nge-100-fs egqithisileyo ye-ultraviolet pulses kwi-26-eV yamandla efoton kwi-negative pump-probe ulibaziseko ngaphambi kokufika kwe-pulse yempompo. Apha, ukwahlukana kwe-spin akusonjululwanga ngenxa yokuthotywa kwesampulu kunye nobukho be-2-eV yepompo ye-pulse ebangela ukuba intlawulo yendawo ibe banzi beempawu ze-spectral. Umzobo we-1C ubonisa utshintsho olubangelwa yimpompo ye-photocurrent ngokubhekiselele kwi-Fig. 1B kwi-pump-probe yokulibaziseka kwe-200 fs apho i-pump-probe signal ifikelela kubuninzi bayo. Imibala ebomvu neluhlaza okwesibhakabhaka ibonisa ukuzuza kunye nokulahlekelwa kweefotoelectrons, ngokulandelanayo.
Ukuhlalutya ezi dynamics zityebileyo kwiinkcukacha ezithe vetshe, siqale sigqibe ngeendawo zencopho ezidlulayo ze-WS2 valence band kunye negraphene π-band ecaleni kwemigca edawuniweyo kuFig. Sifumanisa ukuba ibhendi ye-valence ye-WS2 itshintsha nge-90 meV (Fig. 2A) kunye ne-graphene π-band ihla nge-50 meV (Fig. 2B). Ubomi be-exponential bolu tshintsho lufunyenwe luyi-1.2 ± 0.1 ps ye-valence band ye-WS2 kunye ne-1.7 ± 0.3 ps ye-graphene π-band. Olu tshintsho luyincopho lubonelela ngobungqina bokuqala bokutshaja okwethutyana kwemigangatho emibini, apho intlawulo eyongezelelweyo elungileyo (negative) inyuka (iyancipha) amandla okubopha kumazwe e-elektroniki. Qaphela ukuba i-upshift yebhendi ye-valence ye-WS2 inoxanduva lomqondiso wempompo-probe ebonakalayo kwindawo ephawulwe ngebhokisi emnyama kwi-Fig. 1C.
Utshintsho kwindawo yencopho ye-WS2 yebhendi yevalence (A) kunye negraphene π-band (B) njengomsebenzi wokulibaziseka kwempompo-probe kunye nokulingana okubonakalayo (iimigca engqindilili). Ubomi be-WS2 shift kwi-(A) yi-1.2 ± 0.1 ps. Ubomi begraphene shift in (B) yi-1.7 ± 0.3 ps.
Emva koko, sidibanisa isibonakaliso sempompo-probe phezu kweendawo eziboniswe kwiibhokisi ezinemibala kwi-Fig. abathwali be-photoexcited kufutshane nezantsi kwebhendi yokuqhuba ye-WS2 umaleko kunye nobomi be-1.1 ± 0.1 ps efunyenwe kwi-exponential fit kwidatha (jonga i-Supplementary Materials).
Umkhondo we-Pump-probe njengomsebenzi wokulibaziseka ofunyenwe ngokudibanisa i-photocurrent kwindawo eboniswe kwiibhokisi kwi-Fig 1C. Imigca eshinyeneyo ilingana nedatha. Igophe (1) Inani labathwali abadlulayo kwibhendi yokuqhuba ye-WS2. Igophe (2) Umqondiso wepump-probe ye-π-band yegraphene ngaphezu kwesakhono sekhemikhali sokulingana. Igophe (3) Umqondiso wePump-probe ye-π-band yegraphene ngaphantsi kwekhono lekhemikhali elilinganayo. Igophe (4) Isixhobo somnatha sempompo-probe kwibhendi yevalence yeWS2. Ubomi bufunyaniswa buyi-1.2 ± 0.1 ps ku-(1), 180 ± 20 fs (inzuzo) kunye ~ 2 ps (ilahleko) kwi (2), kunye ne-1.8 ± 0.2 ps kwi-(3).
Kwi-curves 2 kunye ne-3 ye-Fig. 3, sibonisa i-pump-probe signal ye-graphene π-band. Sifumanisa ukuba ukuzuza kwee-electron ngaphezu kwamandla ekhemikhali yokulinganisa (i-curve 2 kwi-Fig. 3) inobomi obufutshane kakhulu (i-180 ± 20 fs) xa kuthelekiswa nokulahlekelwa kwee-electron ngaphantsi kweekhemikhali ezilinganayo (1.8 ± 0.2 ps kwi-curve 3) Umzobo 3). Ukuqhubela phambili, inzuzo yokuqala ye-photocurrent kwi-curve ye-2 ye-Fig. 3 ifunyenwe ukujika ibe yilahleko kwi-t = 400 fs kunye nobomi be ~2 ps. I-asymmetry phakathi kokuzuza kunye nokulahlekelwa ifunyenwe ukuba ayikho kwi-pump-probe signal ye-graphene ye-monolayer engabonakaliyo (jonga umzobo we-S5 kwizinto ezongezelelweyo ze-Supplementary Materials), ebonisa ukuba i-asymmetry iyisiphumo sokudibanisa i-interlayer kwi-WS2 / graphene heterostructure. Ukuqwalaselwa kwenzuzo yexesha elifutshane kunye nelahleko ehlala ixesha elide ngasentla nangaphantsi kweekhemikhali ezilinganayo, ngokulandelanayo, kubonisa ukuba ii-electron zisuswe ngokufanelekileyo kwi-graphene layer phezu kwe-photoexcitation ye-heterostructure. Ngenxa yoko, i-graphene layer iba yi-positive charge, ehambelana nokunyuka kwamandla okubopha i-π-band efunyenwe kwi-Fig 2B. I-downshift ye-π-band isusa umsila ophezulu we-energy yokulinganisa ukusabalalisa kwe-Fermi-Dirac ukusuka ngaphaya kwe-equilibrium chemical potential, echaza ngokuyinxenye utshintsho lwesignali yempompo-probe kwi-curve 2 ye-Fig. bonisa ngezantsi ukuba esi siphumo siphuculwa ngakumbi yilahleko yexeshana yee-electron kwi-π-band.
Le meko ixhaswa yi-net pump-probe signal ye-WS2 valence band kwi-curve 4 ye-Fig. 3. Ezi datha zifunyenwe ngokudibanisa izibalo phezu kwendawo enikwe yibhokisi emnyama kwi-Fig. 1B ebamba i-electrons photoemitted ibhendi yevalence kulo lonke ulibaziseko lwempompo-probe. Ngaphakathi kwemivalo yempazamo yovavanyo, asifumani nkcazelo yobukho bemingxuma kwibhendi yevalence ye-WS2 kulo nakuphi na ukulibaziseka kwempompo-probe. Oku kubonisa ukuba, emva kwe-photoexcitation, le mingxunya iphinda izaliswe ngokukhawuleza ngexesha elifutshane xa lithelekiswa nesisombululo sethu sexeshana.
Ukubonelela ngobungqina bokugqibela be-hypothesis yethu yokwahlulwa kwentlawulo ye-ultrafast kwi-WS2/graphene heterostructure, simisela inani lemingxunya edluliselwe kumaleko wegraphene njengoko kuchazwe ngokweenkcukacha kwiMathiriyeli eyoNgezelelweyo. Ngamafutshane, ukuhanjiswa kwe-elektroniki okwethutyana kwe-π-band kwafakwa ukuhanjiswa kweFermi-Dirac. Inani lemingxunya liye labalwa ukusuka kumaxabiso avela kwikhemikhali yethutyana kunye nobushushu be-elektroniki. Isiphumo siboniswe kuMzobo 4. Sifumanisa ukuba inani elipheleleyo ~ 5 × 1012 imingxuma / cm2 idluliselwe ukusuka kwi-WS2 ukuya kwigraphene kunye nobomi obucacileyo be-1.5 ± 0.2 ps.
Ukutshintsha kwenani lemingxuma kwi-π-band njengomsebenzi wokulibaziseka kwempompo kunye ne-exponential fit inika ubomi be-1.5 ± 0.2 ps.
Ukusuka kwiziphumo kwiFig. I-2 ukuya ku-4, umfanekiso olandelayo we-microscopic yokudluliselwa kwentlawulo ye-ultrafast kwi-WS2 / i-graphene heterostructure ivela (Umfanekiso 5). I-Photoexcitation ye-WS2/graphene heterostructure kwi-2 eV ikholisa kakhulu i-A-exciton kwi-WS2 (Fig. 5A). Imincili eyongezelelweyo ye-elektroniki kwindawo ye-Dirac kwigraphene naphakathi kwe-WS2 kunye ne-graphene bands ziyenzeka ngamandla kodwa zingasebenzi kakuhle kakhulu. Imingxuma enefotoexcited kwibhendi ye-valence ye-WS2 iphinda izaliswe zii-electron ezisuka kwigraphene π-band ngexesha elifutshane xa kuthelekiswa nesisombululo sethu sexeshana (Fig. 5A). I-electrons photoexcited kwi-conduction band ye-WS2 inobomi be-∼1 ps (umzobo 5B). Nangona kunjalo, kuthatha ~ 2 ps ukuphinda ugcwalise imingxuma kwigraphene π-band (Fig. 5B). Oku kubonisa ukuba, ngaphandle kokudluliselwa kwe-electron ngokuthe ngqo phakathi kwebhendi yokuqhuba i-WS2 kunye ne-graphene π-band, iindlela zokuphumla ezongezelelweyo-mhlawumbi ngeemeko zesiphene (26) -kufuneka ziqwalaselwe ukuqonda amandla apheleleyo.
(A) I-photoexcitation kwi-resonance kwi-WS2 A-exciton kwi-2 eV ifaka ii-electron kwi-conduction band ye-WS2. Imingxuma ehambelanayo kwibhendi ye-valence ye-WS2 iphinda izaliswe ngokukhawuleza ngee-electron ezisuka kwi-graphene π-band. (B) Abathwali befotoexcited kwibhanti yokuqhuba ye-WS2 banobomi obuyi-∼1 ps. Imingxuma kwigraphene π-band iphila ∼2 ps, ebonisa ukubaluleka kwamajelo osasazo awongezelelweyo aboniswe ngeentolo ezidayiweyo. Imigca emnyama edayiweyo kwi (A) kunye (B) ibonisa utshintsho lwebhendi kunye notshintsho kwikhono lekhemikhali. (C) Kwimeko edlulayo, umaleko we-WS2 uhlawuliswa kakubi ngelixa umaleko wegraphene uhlawuliswa kakuhle. Ukuzonwabisa okukhethiweyo kwe-spin kunye nokukhanya okujikelezayo okujikelezayo, ii-electron ze-photoexcited kwi-WS2 kunye nemingxuma ehambelanayo kwi-graphene kulindeleke ukuba ibonise i-spin polarization.
Kwimeko yesikhashana, i-electron e-photoexcited ihlala kwi-band conduction ye-WS2 ngelixa imingxuma ye-photoexcited ifumaneka kwi-π-band ye-graphene (Fig. 5C). Oku kuthetha ukuba umaleko we-WS2 uhlawuliswa kakubi kwaye umaleko wegraphene uhlawuliswe kakuhle. Oku kubangela utshintsho oluphezulu lwexeshana (umzobo 2), i-asymmetry ye-graphene pump-probe signal (i-curves 2 kunye ne-3 ye-Fig. 3), ukungabikho kwemingxuma kwi-valence band ye-WS2 (i-curve 4 Fig. 3) , kunye nemingxuma eyongezelelweyo kwi-graphene π-band (Umfanekiso 4). Ubomi beli lizwe elihlulwe-ntlawulo ngu-∼1 ps (i-curve 1 Fig. 3).
Intlawulo efanayo-yahlulwe kumazwe adlulayo aye abonwa kwi-heterostructures enxulumene ne-van der Waals eyenziwe ngee-semiconductors ezimbini ezithe ngqo ezinohlobo lwe-II yolungelelwaniso kunye ne-bandgap egxadazelayo (27-32). Emva kwe-photoexcitation, ii-electron kunye nemingxuma zifunyenwe zihamba ngokukhawuleza ukuya ngaphantsi kwebhendi yokuqhubela phambili kunye nephezulu ye-valence band, ngokulandelanayo, ezifumaneka kwiindawo ezahlukeneyo ze-heterostructure (27-32).
Kwimeko yethu ye-WS2/graphene heterostructure, eyona ndawo inomdla kakhulu kuzo zombini ii-electron kunye nemingxuma ikwinqanaba le-Fermi kumaleko we-metallic graphene. Ngoko ke, umntu unokulindela ukuba zombini ii-electron kunye nemingxuma zitshintshela ngokukhawuleza kwi-graphene π-band. Nangona kunjalo, imilinganiselo yethu ibonisa ngokucacileyo ukuba ukuhanjiswa komngxuma (<200 fs) kusebenza kakhulu kunokudluliselwa kwe-electron (∼1 ps). Sibalela oku kulungelelwaniso olunamandla lwe-WS2 kunye neebhanti zegraphene njengoko zityhilwe kuMzobo 1A obonelela ngenani elikhulu lamazwe akhoyo okugqibela okudluliselwa komngxuma xa kuthelekiswa nokudluliselwa kwe-electron njengoko kulindelwe kutsha nje (14, 15). Kwimeko yangoku, ukuthatha i-∼2 eV WS2 bandgap, i-graphene Dirac point kunye ne-equilibrium chemical potential ifumaneka ~0.5 kunye ne-0.2 eV ngaphezu kombindi we-WS2 bandgap, ngokulandelanayo, ukuphulwa kwe-symmetry ye-electron-hole. Sifumanisa ukuba inani leemeko zokugqibela ezikhoyo zokudluliselwa komngxunya ngu-∼ amaxesha ama-6 amakhulu kunokudluliselwa kwe-electron (jonga i-Supplementary Materials), yiyo loo nto ukuhanjiswa komngxuma kulindeleke ukuba kukhawuleze kunokudluliselwa kwe-electron.
Umfanekiso opheleleyo wemicroscopic ojongiweyo we-ultrafast asymmetric charge transfer kufuneka, nangona kunjalo, kwakhona uqwalasele ukutyhoboza phakathi kwe orbitals ezenza umsebenzi wamaza we-A-exciton kwi-WS2 kunye negraphene π-band, ngokulandelelanayo, i-electron-electron-electron kunye ne-electron-phonon scattering. iziteshi ezibandakanya imiqobo ebekwe ngumfutho, amandla, i-spin, kunye nokugcinwa kwe-pseudospin, impembelelo ye-plasma oscillations (33), kunye nendima ye-excitive enokwenzeka yokukhupha i-phonon oscillations ehambelanayo enokuthi idibanise ukuhanjiswa kwentlawulo (34, 35) . Kwakhona, umntu unokuthelekelela ukuba imeko yokhutshelo lwentlawulo ejongiweyo iqulathe ii-excitons zokhutshelo lwentlawulo okanye iiperi ze-electron-hole zasimahla (jonga i-Supplementary Materials). Uphando oluthe kratya lwethiyori olungaphaya komxholo wephepha langoku luyafuneka ukucacisa le miba.
Isishwankathelo, sisebenzise i-tr-ARPES ukufunda ukudluliselwa kwentlawulo ye-interlayer ye-ultrafast kwi-epitaxial WS2/graphene heterostructure. Sifumene ukuba, xa sivuyiswa kwi-resonance kwi-A-exciton ye-WS2 kwi-2 eV, imingxuma e-photoexcited idlulisela ngokukhawuleza kwi-graphene layer ngelixa i-electronics photoexcited ihlala kwi-WS2 layer. Sibalele oku kwinto yokuba inani lamazwe akhoyo okugqibela okudluliselwa komngxuma likhulu kunokudluliselwa kwe-electron. Ubomi bomrhumo-okwahlulwe kwimeko yesikhashana bufunyenwe ~i-1 ps. Ngokudibanisa ne-spin-selective optical excitation usebenzisa ukukhanya kwe-circularly polarized (22-25), ukudluliselwa kwentlawulo ye-ultrafast kunokuhamba kunye nokudluliselwa kwe-spin. Kule meko, i-WS2/graphene heterostructure ephandiweyo inokusetyenziselwa inaliti esebenzayo ye-optical spin kwigraphene ekhokelela kwizixhobo ezintsha ze-optospintronic.
Iisampulu zegraphene zakhuliswa kwi-semiconducting ye-6H-SiC (0001) yorhwebo yorhwebo evela kwi-SiCrystal GmbH. I-N-doped wafers yayikwi-axis ene-miscut engaphantsi kwe-0.5 °. I-substrate ye-SiC yayifakwe i-hydrogen-etched ukususa imikrwelo kunye nokufumana iiterras eziqhelekileyo ezisicaba. Indawo ecocekileyo kunye ne-atomically flat I-Si-terinated surface emva koko i-graphitize ngokufaka isampuli kwi-Aratmosphere ye-Ar kwi-1300 ° C kwi-8 min (36). Ngale ndlela, sifumene umaleko wekhabhoni enye apho iathom yekhabhoni yesithathu yenza ibhondi edibeneyo kwi-SiC substrate (37). Lo maleko emva koko wajikwa waba yi-sp2-hybridized quasi ngokupheleleyo-emiyo emngxunyeni-doped graphene nge-hydrogen intercalation (38). Ezi sampuli zibizwa ngokuba yigraphene/H-SiC(0001). Yonke le nkqubo iqhutywe kwigumbi lokukhula elimnyama loMnyama ukusuka e-Aixtron. Ukukhula kwe-WS2 kwaqhutyelwa kwi-reactor esemgangathweni yodonga olushushu ngoxinzelelo oluphantsi loxinzelelo lwe-chemical vapor deposition (39, 40) kusetyenziswa i-WO3 kunye ne-S powders enomlinganiselo we-1: 100 njenge-precursors. I-WO3 kunye ne-S powders zigcinwe kwi-900 kunye ne-200 ° C, ngokulandelanayo. I-WO3 powder ibekwe kufuphi ne-substrate. I-Argon yayisetyenziswe njengegesi ethwala kunye nokuhamba kwe-8 sccm. Uxinzelelo kwi-reactor lugcinwe kwi-0.5 mbar. Iisampulu ziphawulwe nge-electron microscopy yesibini, i-atomic force microscopy, iRaman, kunye ne-photoluminescence spectroscopy, kunye ne-electron diffraction ene-low-energy. Le milinganiselo iveze imimandla emibini eyahlukeneyo ye-WS2 yekristale enye apho i-ΓK- okanye i-ΓK'-izalathiso ilungelelaniswe ne-ΓK-umkhomba-ndlela womaleko wegraphene. Ubude becala leDomain bahluka phakathi kwe-300 kunye ne-700 nm, kwaye iyonke i-WS2 yokufikelela yaqikelelwa ukuya ku-∼40%, ilungele uhlalutyo lwe-ARPES.
Iimvavanyo ze-ARPES ezimileyo zenziwa nge-hemispherical analyzer (i-SPECS PHOIBOS 150) kusetyenziswa i-charge-coupled device-detector system ukuze kubonwe i-dimensional-dimensional ye-electron energy kunye nomfutho. I-Unpolarized, monochromatic He Iα radiation (21.2 eV) ye-high-flux He discharge source (VG Scienta VUV5000) isetyenziswe kuzo zonke iimvavanyo ze-photoemission. Amandla kunye nesisombululo se-angular kwiimvavanyo zethu bezingcono kune-30 meV kunye ne-0.3 ° (ehambelana ne-0.01 Å−1), ngokulandelanayo. Zonke iimvavanyo zenziwa kwiqondo lobushushu begumbi. I-ARPES bubuchule obunobuzaza kakhulu kumphezulu. Ukukhupha ii-photoelectrons kuzo zombini i-WS2 kunye ne-graphene layer, iisampulu ezinokhuselo lwe-WS2 olungaphelelanga ~e-40% zisetyenzisiwe.
Umiselo lwe-tr-ARPES lwalusekwe kwi-1-kHz Titanium:Sapphire amplifier (Coherent Legend Elite Duo). I-2 mJ yamandla aphumayo yayisetyenziselwa ukuveliswa kwe-harmonics ephezulu kwi-argon. Ukukhanya okugqithisileyo kwe-ultraviolet okubangelwa kudlula kwi-grating monochromator evelisa i-100-fs probe pulses kwi-26-eV photon energy. I-8mJ yamandla okukhutshwa kweamplifier ithunyelwe kwi-optical parametric amplifier (HE-TOPAS ukusuka kwi-Light Conversion). I-signal beam kwi-1-eV yamandla e-photon yayiphindwe kabini kwi-beta barium borate crystal ukufumana i-2-eV pump pulses. Imilinganiselo ye-tr-ARPES yenziwa nge-hemispherical analyzer (SPECS PHOIBOS 100). Amandla ewonke kunye nesisombululo sexeshana yayiyi-240 meV kunye ne-200 fs, ngokulandelelanayo.
Imathiriyeli eyongezelelweyo yeli nqaku iyafumaneka http://advances.sciencemag.org/cgi/content/full/6/20/eaay0761/DC1
Eli linqaku elivulekileyo lokufikelela lisasazwe phantsi kwemiqathango yelayisensi ye-Creative Commons Attribution-NonCommercial, evumela ukusetyenziswa, ukuhanjiswa, kunye nokuveliswa kwakhona kuyo nayiphi na indlela, okoko nje ukusetyenziswa okubangelwayo kungeyonzuzo yorhwebo kwaye ibonelele umsebenzi wokuqala ngokufanelekileyo. icatshulwe.
QAPHELA: Sicela idilesi yakho ye-imeyile kuphela ukuze umntu omcebisayo eli phepha azi ukuba ubufuna alibone, kwaye asiyoimeyile eyinkunkuma. Asithathi nayiphi na idilesi ye-imeyile.
Lo mbuzo ngowokuvavanya ukuba ngaba ungumtyeleli wabantu okanye awunguye kwaye uthintele ukuhanjiswa komyalezo ozenzekelayo.
NguSven Aeschlimann, Antonio Rossi, Mariana Chávez-Cervantes, Razvan Krause, Benito Arnoldi, Benjamin Stadtmüller, Martin Aeschlimann, Stiven Forti, Filippo Fabbri, Camilla Coletti, Isabella Gierz
Sityhila ukwahlukana kwentlawulo ekhawulezayo kwi-WS2/graphene heterostructure enokuthi ivumele inaliti ye-optical spin kwigraphene.
NguSven Aeschlimann, Antonio Rossi, Mariana Chávez-Cervantes, Razvan Krause, Benito Arnoldi, Benjamin Stadtmüller, Martin Aeschlimann, Stiven Forti, Filippo Fabbri, Camilla Coletti, Isabella Gierz
Sityhila ukwahlukana kwentlawulo ekhawulezayo kwi-WS2/graphene heterostructure enokuthi ivumele inaliti ye-optical spin kwigraphene.
© 2020 Umbutho waseMelika wokuPhucula iNzululwazi. Onke Amalungelo Agciniwe. I-AAAS ngumlingane we-HINARI, i-AGORA, i-OARE, i-CHORUS, i-CLOCKSS, i-CrossRef kunye ne-COUNTER.I-Science Advances ISSN 2375-2548.
Ixesha lokuposa: May-25-2020