Timagwiritsa ntchito nthawi ndi angle-resolved photoemission spectroscopy (tr-ARPES) kuti tifufuze kusamutsidwa kwachangu kwambiri mu epitaxial heterostructure yopangidwa ndi monolayer WS2 ndi graphene. Heterostructure iyi imaphatikiza phindu la semiconductor yachindunji yokhala ndi ma spin-orbit coupling amphamvu komanso kulumikizana kwamphamvu kwa zinthu zowala ndi zomwe zimanyamula zonyamula zopanda pake zomwe zimakhala ndikuyenda kwambiri komanso nthawi yayitali yamoyo. Timapeza kuti, pambuyo photoexcitation pa resonance kwa A-exciton mu WS2, maenje photoexcited mofulumira kusamutsa mu graphene wosanjikiza pamene ma elekitironi photoexcited kukhala mu wosanjikiza WS2. Zotsatira zake zosiyanitsidwa ndi mtengo wanthawi yochepa zimapezeka kuti zimakhala ndi moyo ~ 1 ps. Tikunena zomwe tapeza chifukwa cha kusiyana kwa gawo lobalalitsa lomwe limayambitsidwa ndi kuyanjanitsa kwa WS2 ndi magulu a graphene monga momwe ARPES amawululira. Kuphatikizana ndi kusangalatsidwa kwa ma spin-selective optical, kufufuzidwa kwa WS2/graphene heterostructure kungapereke nsanja yojambulira bwino kuwala kwa graphene.
Kupezeka kwa zida zambiri zamitundu iwiri kwatsegula mwayi wopanga ma heterostructures opyapyala okhala ndi magwiridwe antchito atsopano kutengera kuwunika kwa dielectric ndi zotsatira zosiyanasiyana zoyandikira (1-3). Zipangizo zotsimikiziranso zomwe zidzagwiritsidwe ntchito m'tsogolomu pazamagetsi ndi ma optoelectronics zakwaniritsidwa (4-6).
Apa, timayang'ana pa epitaxial van der Waals heterostructures yopangidwa ndi monolayer WS2, semiconductor yolunjika-gap yokhala ndi kulumikizana kolimba kozungulira komanso kugawanika kwakukulu kwa bandi chifukwa cha kusweka kwa symmetry (7), ndi monolayer graphene, semimetal. yokhala ndi gulu la conical komanso kuyenda kwambiri (8), yokulirapo pa SiC (0001) ya haidrojeni. Zizindikiro zoyamba za kusamutsa kwachangu kwambiri (9-15) ndi kuyandikira-kuyambitsa spin-orbit coupling zotsatira (16-18) kumapangitsa WS2/graphene ndi ma heterostructures ofanana omwe amalonjeza ofuna optoelectronic (19) ndi optospintronic (20) m'tsogolo.
Tidayamba kuwulula njira zopumulira za ma electron-hole awiriawiri opangidwa ndi ma electron mu WS2/graphene okhala ndi nthawi ndi ma angle-resolved photoemission spectroscopy (tr-ARPES). Pachifukwa chimenecho, timasangalala ndi mawonekedwe a heterostructure okhala ndi 2-eV pump pulses resonant to A-exciton mu WS2 (21, 12) ndikutulutsa ma photoelectrons ndi kuchedwa kwachiwiri kochedwa kugunda kwa 26-eV photon mphamvu. Timazindikira mphamvu ya kinetic ndi emission angle ya ma photoelectrons ndi hemispherical analyzer monga ntchito ya pump-probe kuchedwa kuti tipeze mphamvu, mphamvu-, ndi mphamvu zotengera nthawi. Kusintha kwamphamvu ndi nthawi ndi 240 meV ndi 200 fs, motsatana.
Zotsatira zathu zimapereka umboni wachindunji wa kusamutsidwa kopitilira muyeso pakati pa zigawo zofananira ndi epitaxially, kutsimikizira zisonyezo zoyambira kutengera njira zonse zowoneka bwino muzinthu zofananira pamanja zomwe zimasonkhanitsidwa ndi ma azimuthal osagwirizana ndi zigawo (9-15). Kuphatikiza apo, tikuwonetsa kuti kusamutsa kwa ndalamaku ndikokwanira kwambiri. Miyezo yathu imawulula dera lomwe silinawonedwe, losiyanitsidwa ndi mtengo, lomwe lili ndi ma electron okondwa ndi mabowo omwe ali mu WS2 ndi graphene wosanjikiza, motsatana, omwe amakhala ~1 ps. Timatanthauzira zomwe tapeza potengera kusiyana kwa gawo lobalalitsa gawo la ma elekitironi ndi kusamutsidwa kwa dzenje komwe kumachitika chifukwa cha kulumikizana kwa WS2 ndi magulu a graphene monga zawululidwa ndi ARPES yotsimikizika kwambiri. Kuphatikizidwa ndi ma spin- ndi valley-selective Optical excitation (22-25) WS2/graphene heterostructures atha kupereka nsanja yatsopano ya jakisoni wa ultrafast optical spin mu graphene.
Chithunzi 1A chikuwonetsa muyeso wapamwamba wa ARPES wopezedwa ndi nyali ya helium ya kamangidwe ka bandi motsatira ΓK-direction of the epitaxial WS2/graphene heterostructure. Dirac cone imapezeka kuti ili ndi dzenje-doped ndi mfundo ya Dirac yomwe ili ~ 0.3 eV pamwamba pa mphamvu ya mankhwala ofanana. Pamwamba pa spin-split WS2 valence band imapezeka kuti ndi ~ 1.2 eV pansi pa mphamvu ya mankhwala ofanana.
(A) Chithunzi chofananira choyezera motsatira njira ya ΓK ndi nyali ya helium yopanda polarized. (B) Photocurrent ya kuchedwa kwa mpope-probe kuyeza ndi p-polarized kwambiri ultraviolet pulses pa 26-eV photon mphamvu. Mizere yodukidwa imvi ndi yofiira imasonyeza malo a mbiri ya mzere womwe umagwiritsidwa ntchito pochotsa malo apamwamba osakhalitsa mu Chithunzi 2. (C) Kusintha kwapampu kwa photocurrent 200 fs pambuyo pa photoexcitation pa pump photon mphamvu ya 2 eV ndi pampu fluence 2 mJ/cm2. Kupindula ndi kutayika kwa ma photoelectrons kumawonetsedwa mofiira ndi buluu, motero. Mabokosiwo amasonyeza malo ophatikizirapo zofufuza zapampu zomwe zikuwonetsedwa mu Chithunzi 3.
Chithunzi 1B chikuwonetsa chithunzithunzi cha tr-ARPES cha kamangidwe ka bandi pafupi ndi WS2 ndi ma graphene K-points oyezedwa ndi 100-fs kwambiri ultraviolet pulses pa 26-eV photon mphamvu pa negative mpope-probe kuchedwa kufika kwa mpope kugunda. Apa, kugawanika kwa ma spin sikungathetsedwe chifukwa cha kuwonongeka kwa zitsanzo komanso kupezeka kwa 2-eV pampu yamagetsi yomwe imapangitsa kuti danga liwonjezeke kwa mawonekedwe a spectral. Chithunzi cha 1C chikuwonetsa kusintha kwapampu kwa photocurrent ponena za Mkuyu 1B pampopi-probe kuchedwa kwa 200 fs kumene chizindikiro cha mpope-probe chimafika pamtunda wake. Mitundu yofiira ndi yabuluu imasonyeza kupindula ndi kutayika kwa ma photoelectrons, motero.
Kuti tifufuze zamphamvu izi mwatsatanetsatane, choyamba timadziwa malo osakhalitsa a gulu la valence la WS2 ndi graphene π-band pamizere yodutsa mu Mkuyu 1B monga momwe tafotokozera mwatsatanetsatane mu Supplementary Materials. Timapeza kuti WS2 valence gulu zisintha mmwamba ndi 90 meV (mkuyu. 2A) ndi graphene π-gulu masinthidwe pansi ndi 50 meV (mkuyu. 2B). Kutalika kwa moyo wa ma shift awa ndi 1.2 ± 0.1 ps kwa gulu la valence la WS2 ndi 1.7 ± 0.3 ps kwa graphene π-band. Kusintha kwapamwamba kumeneku kumapereka umboni woyamba wa kulipiritsa kwakanthawi kwa zigawo ziwiri, pomwe ndalama zowonjezera zabwino (zoyipa) zimachulukitsa (zimachepetsa) mphamvu zomangirira zamagawo amagetsi. Zindikirani kuti kukweza kwa gulu la valence la WS2 kumayang'anira chizindikiro chodziwika bwino cha mpope m'dera lomwe lalembedwa ndi bokosi lakuda mu Chithunzi 1C.
Kusintha kwapamwamba kwa gulu la valence la WS2 (A) ndi graphene π-band (B) ngati ntchito yochedwa pampu-probe limodzi ndi ma exponential fit (mizere yokhuthala). Nthawi yamoyo wa WS2 kusintha mu (A) ndi 1.2 ± 0.1 ps. Moyo wa kusintha kwa graphene mu (B) ndi 1.7 ± 0.3 ps.
Kenaka, timagwirizanitsa chizindikiro cha mpope-probe pamadera omwe amasonyezedwa ndi mabokosi amitundu mu Mkuyu 1C ndikukonzekera zowerengera zomwe zimatsatira ngati ntchito ya kuchedwa kwapope-probe mu Chithunzi 3. Mzere wa 1 mu Chithunzi 3 umasonyeza mphamvu za photoexcited zonyamulira pafupi ndi pansi pa conduction band ya WS2 wosanjikiza ndi moyo wa 1.1 ± 0.1 ps zopezedwa kuchokera exponential fit kwa deta (onani Supplementary Materials).
Kufufuza kwapampu ngati ntchito ya kuchedwa yomwe imapezeka mwa kuphatikiza chithunzithunzi pa malo omwe akuwonetsedwa ndi mabokosi a mkuyu 1C. Mizere yokhuthala imayenderana ndi ma data. Curve (1) Chiwerengero cha anthu onyamula anthu osakhalitsa mugulu la conduction la WS2. Mapindikira (2) Chizindikiro cha mpope-chofufuza cha π-gulu la graphene pamwamba pa mphamvu ya mankhwala. Mapindikira (3) Chizindikiro cha mpope-chofufuza cha π-gulu la graphene pansi pa mphamvu ya mankhwala. Curve (4) Chizindikiro cha Net pump-probe mu gulu la valence la WS2. Nthawi zamoyo zimapezeka kuti ndi 1.2 ± 0.1 ps mu (1), 180 ± 20 fs (kupindula) ndi ~ 2 ps (kutaya) mu (2), ndi 1.8 ± 0.2 ps mu (3).
Mu ma curve 2 ndi 3 a mkuyu 3, tikuwonetsa chizindikiro cha mpope-chofufuza cha graphene π-band. Timapeza kuti kupindula kwa ma electron pamwamba pa mphamvu ya mankhwala (curve 2 mu mkuyu 3) ili ndi moyo waufupi kwambiri (180 ± 20 fs) poyerekeza ndi kutayika kwa ma electron pansi pa mphamvu ya mankhwala (1.8 ± 0.2 ps mu curve 3) Chithunzi 3). Kuwonjezera apo, kupindula koyambirira kwa photocurrent mu curve 2 ya Mkuyu 3 imapezeka kuti iwonongeke pa t = 400 fs ndi moyo wa ~ 2 ps. The asymmetry pakati kupindula ndi kutayika kumapezeka kuti palibe pampu-probe chizindikiro cha monolayer graphene osavumbulidwa (onani mkuyu. S5 mu Zowonjezera Zowonjezera), kusonyeza kuti asymmetry ndi zotsatira za kugwirizana kwa interlayer mu WS2 / graphene heterostructure. Kuwona kupindula kwakanthawi kochepa ndi kutayika kwa moyo wautali pamwamba ndi pansi pa mphamvu ya mankhwala, motero, kumasonyeza kuti ma elekitironi amachotsedwa bwino pa graphene wosanjikiza pa photoexcitation ya heterostructure. Chotsatira chake, graphene wosanjikiza amakhala ndi mlandu wabwino, zomwe zimagwirizana ndi kuwonjezeka kwa mphamvu yomangiriza ya π-band yomwe imapezeka mu Mkuyu 2B. Kutsika kwa π-band kumachotsa mchira wamphamvu kwambiri wa kugawa kwa Fermi-Dirac kuchokera pamwamba pa mphamvu ya mankhwala, yomwe imalongosola pang'ono kusintha kwa chizindikiro cha mpope-probe mu curve 2 ya mkuyu 3. Tidzatero. onetsani pansipa kuti izi zimakulitsidwanso ndi kutayika kwakanthawi kwa ma electron mu π-band.
Chochitika ichi chimathandizidwa ndi chizindikiro cha mpope-probe cha WS2 valence band mu curve 4 ya mkuyu. gulu la valence nthawi zonse kuchedwa kwapampu-probe. M'mipiringidzo ya zolakwika zoyeserera, sitipeza chilichonse chosonyeza kukhalapo kwa mabowo mu gulu la valence la WS2 pakuchedwa kulikonse kwapampu. Izi zikuwonetsa kuti, pambuyo pa photoexcitation, mabowowa amadzadzidwanso mwachangu pakanthawi kochepa poyerekeza ndi kusintha kwathu kwakanthawi.
Kuti tipereke umboni womaliza wa lingaliro lathu la kupatukana kwachangu kwambiri mu WS2/graphene heterostructure, timazindikira kuchuluka kwa mabowo omwe amasamutsidwa ku graphene wosanjikiza monga tafotokozera mwatsatanetsatane mu Zowonjezera Zowonjezera. Mwachidule, kugawa kwakanthawi kwamagetsi kwa π-band kudapangidwa ndi Fermi-Dirac. Chiwerengero cha mabowo ndiye kuwerengedwa kuchokera ku zotsatira za zotsatira zosakhalitsa za mankhwala ndi kutentha kwamagetsi. Chotsatira chikuwonetsedwa mu Chithunzi 4. Timapeza kuti chiwerengero chonse cha ~ 5 × 1012 mabowo / cm2 amasamutsidwa kuchokera ku WS2 kupita ku graphene ndi nthawi yowonjezereka ya 1.5 ± 0.2 ps.
Kusintha kwa chiwerengero cha mabowo mu π-band ngati ntchito ya kuchedwa kwa mpope-probe pamodzi ndi exponential fit yopereka moyo wonse wa 1.5 ± 0.2 ps.
Kuchokera muzopeza mu Mkuyu. 2 mpaka 4, chithunzi chotsatira chaching'ono chotsatirachi cha ultrafast charge transfer mu WS2/graphene heterostructure imatuluka (mkuyu. 5). Photoexcitation wa WS2/graphene heterostructure pa 2 eV makamaka populates A-exciton mu WS2 (mkuyu. 5A). Zowonjezera pamagetsi pa Dirac point mu graphene komanso pakati pa WS2 ndi magulu a graphene ndizotheka mwamphamvu koma sizothandiza kwambiri. Mabowo a photoexcited mu gulu la valence la WS2 amadzazidwanso ndi ma elekitironi ochokera ku graphene π-gulu pa nthawi yochepa poyerekeza ndi kusamvana kwathu kwakanthawi (mkuyu 5A). Ma electron ochititsa chidwi mu gulu la conduction la WS2 ali ndi moyo wa ~ 1 ps (mkuyu 5B). Komabe, zimatengera ~ 2 ps kuti mudzazenso mabowo mu graphene π-band (Mkuyu 5B). Izi zikusonyeza kuti, pambali pa kusamutsidwa kwa elekitironi mwachindunji pakati pa WS2 conduction band ndi graphene π-band, njira zina zopumula—mwina kudzera m’maiko a chilema (26)—ziyenera kuganiziridwa kuti zimvetsetse mphamvu zonse.
(A) Photoexcitation pa resonance kwa WS2 A-exciton pa 2 eV jekeseni ma elekitironi mu conduction bandi ya WS2. Mabowo ofanana mu gulu la valence la WS2 amadzazidwanso nthawi yomweyo ndi ma elekitironi ochokera ku graphene π-band. (B) Onyamula zithunzi mu gulu la conduction la WS2 amakhala ndi moyo ~1 ps. Mabowo a graphene π-band amakhala ∼2 ps, kuwonetsa kufunikira kwa njira zowonjezera zobalalitsira zomwe zikuwonetsedwa ndi mivi yodutsa. Mizere yakuda mu (A) ndi (B) imasonyeza kusintha kwa magulu ndi kusintha kwa mphamvu za mankhwala. (C) M'malo osakhalitsa, wosanjikiza wa WS2 amayimbidwa molakwika pomwe graphene wosanjikiza ali ndi mlandu wabwino. Pachisangalalo chosankhika chokhala ndi kuwala kozungulira, ma electron osangalatsa mu WS2 ndi mabowo ofananira nawo mu graphene akuyembekezeka kuwonetsa polarization yosiyana.
Mu chikhalidwe chosakhalitsa, ma elekitironi photoexcited amakhala mu conduction gulu la WS2 pamene mabowo photoexcited zili mu π-gulu la graphene (mkuyu. 5C). Izi zikutanthauza kuti WS2 wosanjikiza ali ndi mlandu woyipa ndipo graphene wosanjikiza ali ndi mlandu wabwino. Izi zimatengera kusintha kwapang'onopang'ono kwapang'onopang'ono (mkuyu 2), asymmetry ya chizindikiro cha graphene pump-probe (ma curve 2 ndi 3 a mkuyu 3), kusowa kwa mabowo mu gulu la valence la WS2 (mapindikira 4 mkuyu. 3) , komanso mabowo owonjezera mu graphene π-band (mkuyu 4). Moyo wamtunduwu wolekanitsidwa ndi ndalama ndi ~ 1 ps (curve 1 Fig. 3).
Zofananira zosiyanitsidwa ndi zotengera zanthawi yayitali zawonedwa muzinthu zofananira za van der Waals zopangidwa kuchokera ku ma semiconductors awiri achindunji okhala ndi mtundu wachiwiri wa band ndi bandgap yoyenda (27-32). Pambuyo pa photoexcitation, ma electron ndi mabowo anapezeka kuti akuyenda mofulumira pansi pa gulu la conduction ndi pamwamba pa gulu la valence, motero, zomwe zili m'magulu osiyanasiyana a heterostructure (27-32).
Pankhani ya WS2 / graphene heterostructure wathu, ndi mphamvu yabwino malo ma elekitironi onse ndi mabowo ndi pa mlingo Fermi mu zitsulo wosanjikiza graphene. Chifukwa chake, wina angayembekezere kuti ma elekitironi ndi mabowo onse amasamutsira ku gulu la graphene π. Komabe, miyeso yathu imasonyeza bwino kuti kusamutsa dzenje (<200 fs) ndikothandiza kwambiri kuposa kusamutsa ma elekitironi (∼1 ps). Ife amati izi ndi wachibale amphamvu mayikidwe WS2 ndi magulu graphene monga kuwululidwa mkuyu. 1A kuti amapereka chiwerengero chokulirapo cha likupezeka mayiko omaliza kwa dzenje kutengerapo poyerekeza ndi ma elekitironi kutengerapo posachedwapa kuyembekezera ndi (14, 15). Pakali pano, kutengera ~2 eV WS2 bandgap, graphene Dirac point ndi equilibrium chemical potential zilipo ~ 0.5 ndi ~ 0.2 eV pamwamba pa pakati pa WS2 bandgap, motero, kuswa electron-bole symmetry. Timapeza kuti chiwerengero cha mayiko omaliza omwe akupezeka kuti asamutsire dzenje ndi ∼ kuwirikiza ka 6 kuposa kusamutsidwa kwa ma elekitironi (onani Zowonjezera Zowonjezera), chifukwa chake kusuntha kwa dzenje kuyenera kukhala kofulumira kuposa kusamutsa ma elekitironi.
Chithunzi chathunthu cha microscopic cha kusamutsidwa kwamphamvu kwambiri kwa asymmetric charge ayenera kuganiziranso kuphatikizika pakati pa orbitals omwe amapanga mawonekedwe a A-exciton wave mu WS2 ndi graphene π-band, motsatana, ma elekitironi-electron ndi electron-phonon kumwazikana. mayendedwe ophatikizika ndi zopinga zomwe zimaperekedwa ndi kuthamanga, mphamvu, kupota, ndi kusungidwa kwa pseudospin, kukopa kwa plasma oscillations (33), komanso gawo la chisangalalo chomwe chingathe kutsatiridwa ndi ma phonon oscillations omwe angayanjanitse kusamutsa kwa mtengo (34, 35) . Komanso, wina atha kuganiza ngati gawo losamutsira ndalama lomwe limawonedwa lili ndi ma excitons kapena ma electron-hole pairs (onani Zida Zowonjezera). Kufufuza kwina kwamalingaliro komwe kumapitilira zomwe zili patsamba lino ndikofunikira kuti kumveketse bwino nkhanizi.
Mwachidule, tagwiritsa ntchito tr-ARPES kuphunzira kusamutsidwa kwa ma charger othamanga kwambiri mu epitaxial WS2/graphene heterostructure. Tinapeza kuti, pamene anasangalala resonance kwa A-exciton wa WS2 pa 2 eV, ndi maenje photoexcited mofulumira kusamutsa mu graphene wosanjikiza pamene ma elekitironi photoexcited kukhalabe mu wosanjikiza WS2. Tidanena izi chifukwa chakuti kuchuluka kwa mayiko omaliza osinthira mabowo ndikokulirapo kuposa kusamutsa ma elekitironi. Nthawi ya moyo wanthawi yayitali yosiyanitsidwa ndi chiwongolero idapezeka ~ 1 ps. Kuphatikizika ndi kusangalatsa kwa ma spin-selective optical pogwiritsa ntchito kuwala kozungulira polarized (22-25), kusamutsa kwachangu kopitilira muyeso kumatha kutsagana ndi kusamutsa kwa spin. Pamenepa, kafukufuku wa WS2/graphene heterostructure atha kugwiritsidwa ntchito popanga jakisoni wowoneka bwino mu graphene zomwe zimapangitsa kuti pakhale zida zatsopano za optospintronic.
Zitsanzo za graphene zidakulitsidwa pazamalonda za semiconducting 6H-SiC(0001) kuchokera ku SiCrystal GmbH. Zophika za N-doped zinali pa axis ndi miscut pansi pa 0.5 °. Gawo laling'ono la SiC linali lopangidwa ndi haidrojeni kuti lichotse zipsera ndikupeza masitepe osalala. Malo oyera komanso osalala a atomiki a Si-terinated pamwamba pake adajambula pojambula chitsanzo mu Ar atmosphere pa 1300 ° C kwa 8 min (36). Mwanjira iyi, tidapeza gawo limodzi la kaboni pomwe atomu iliyonse yachitatu ya kaboni imapanga chomangira chogwirizana ndi gawo lapansi la SiC (37). Chosanjikizachi chinasinthidwa kukhala sp2-hybridized quasi free-standing hole-doped graphene kudzera pa hydrogen intercalation (38). Zitsanzozi zimatchedwa graphene/H-SiC(0001). Ntchito yonseyi idachitika mu chipinda chakukula cha Black Magic kuchokera ku Aixtron. Kukula kwa WS2 kunkachitika mu riyakitala yotentha yotentha ndi mpweya wochepa wa mankhwala (39, 40) pogwiritsa ntchito ufa wa WO3 ndi S wokhala ndi chiŵerengero cha 1:100 monga zoyambira. Mafuta a WO3 ndi S adasungidwa pa 900 ndi 200 ° C, motsatana. Ufa wa WO3 unayikidwa pafupi ndi gawo lapansi. Argon idagwiritsidwa ntchito ngati mpweya wonyamulira ndikuyenda kwa 8 sccm. Kupanikizika mu riyakitala kumasungidwa pa 0,5 mbar. Zitsanzozi zinali ndi ma electron microscopy yachiwiri, atomic force microscopy, Raman, ndi photoluminescence spectroscopy, komanso kuchepa kwa mphamvu yamagetsi yamagetsi. Miyezo iyi idawulula madera awiri osiyana a WS2 single-crystalline pomwe ΓK- kapena ΓK'-direction imagwirizana ndi ΓK-direction of the graphene layer. Utali wa mbali za Domain udasiyana pakati pa 300 ndi 700 nm, ndipo kufalikira kwa WS2 kunali pafupifupi ~ 40%, koyenera kuwunika kwa ARPES.
Kuyesera kosasunthika kwa ARPES kunkachitidwa ndi hemispherical analyzer (SPECS PHOIBOS 150) pogwiritsa ntchito makina ophatikizira opangira zida zowunikira kuti azindikire magawo awiri a mphamvu ya ma elekitironi ndi mphamvu. Unpolarized, monochromatic He Iα radiation (21.2 eV) ya high-flux He discharge source (VG Scienta VUV5000) idagwiritsidwa ntchito pazoyesera zonse za Photoemission. Mphamvu ndi kusintha kwa angular muzoyesera zathu zinali bwino kuposa 30 meV ndi 0.3 ° (zofanana ndi 0.01 Å−1), motsatira. Kuyesera konse kunachitika pa kutentha kwa chipinda. ARPES ndi njira yovutirapo kwambiri. Kutulutsa ma photoelectrons kuchokera ku WS2 ndi graphene wosanjikiza, zitsanzo zomwe zili ndi WS2 zosakwanira za ~ 40% zinagwiritsidwa ntchito.
Kukonzekera kwa tr-ARPES kudachokera pa 1-kHz Titanium:Sapphire amplifier (Coherent Legend Elite Duo). 2 mJ ya mphamvu yotulutsa idagwiritsidwa ntchito popanga ma harmonics apamwamba mu argon. Kuwala koopsa kwa ultraviolet komwe kunadutsa pa grating monochromator kumapanga 100-fs probe pulses pa 26-eV photon energy. 8mJ ya mphamvu yotulutsa amplifier idatumizidwa mu chowonjezera cha parametric amplifier (HE-TOPAS kuchokera ku Light Conversion). Mphamvu yamagetsi pa 1-eV photon mphamvu inali yowirikiza kawiri mu beta barium borate crystal kuti ipeze 2-eV pump pulses. Miyezo ya tr-ARPES idachitidwa ndi hemispherical analyzer (SPECS PHOIBOS 100). Mphamvu zonse ndi kusintha kwakanthawi kunali 240 meV ndi 200 fs, motsatana.
Zowonjezera za nkhaniyi zikupezeka pa http://advances.sciencemag.org/cgi/content/full/6/20/eaay0761/DC1
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ZINDIKIRANI: Timangopempha adilesi yanu ya imelo kuti munthu amene mukumupangira tsambalo adziwe kuti mumafuna kuti aliwone, komanso kuti si imelo yopanda pake. Sitijambula imelo iliyonse.
Funsoli ndi loyesa ngati ndinu mlendo kapena ayi komanso kupewa kutumiza sipamu zokha.
Ndi Sven Aeschlimann, Antonio Rossi, Mariana Chávez-Cervantes, Razvan Krause, Benito Arnoldi, Benjamin Stadtmüller, Martin Aeschlimann, Stiven Forti, Filippo Fabbri, Camilla Coletti, Isabella Gierz
Timawulula kupatukana kwachangu kwambiri mu WS2 / graphene heterostructure yomwe imathandizira jekeseni wa optical spin mu graphene.
Ndi Sven Aeschlimann, Antonio Rossi, Mariana Chávez-Cervantes, Razvan Krause, Benito Arnoldi, Benjamin Stadtmüller, Martin Aeschlimann, Stiven Forti, Filippo Fabbri, Camilla Coletti, Isabella Gierz
Timawulula kupatukana kwachangu kwambiri mu WS2 / graphene heterostructure yomwe imathandizira jekeseni wa optical spin mu graphene.
© 2020 American Association for the Advancement of Science. Maumwini onse ndi otetezedwa. AAAS ndi mnzake wa HINARI, AGORA, OARE, CHORUS, CLOCKSS, CrossRef ndi COUNTER.Science Advances ISSN 2375-2548.
Nthawi yotumiza: May-25-2020