Waxaan isticmaalnaa waqti-iyo xagal-xallinta sawir-qaadista sawir-qaadista (tr-ARPES) si aan u baarno wareejinta kharashka ultrafast ee qaab-dhismeedka epitaxial heterostructure oo ka samaysan monolayer WS2 iyo graphene. Heterostructure-kani waxa uu isku daraa faa'iidooyinka semiconductor-ka farqiga tooska ah oo leh isku xidhka lafdhabarta-orbit-ka xooggan iyo is-dhexgalka xoogga leh ee iftiinka-maaddada kuwa semimetal martigelinaya sidayaal aan badnayn oo leh dhaqdhaqaaq aad u sarreeya iyo cimri dherer dheer. Waxaan ogaanay in, ka dib markii sawir-qaadista ee resonance ee A-exciton ee WS2, godadka sawir-qaadista ayaa si degdeg ah ugu wareejiya lakabka graphene halka electrons-ka sawir-qaadista ay ku sii jiraan lakabka WS2. Xaaladda ku meel gaadhka ah ee kala qaybsan ee ka dhalatay kharashka waxa la ogaaday in uu cimrigiisu dhan yahay ~ 1 ps. Waxaan natiijooyinkayaga u nisbaynnay kala duwanaanshiyaha booska kala firdhisanaanta wejiga ee ay sababtay is-waafajinta qaraabada ee WS2 iyo xargaha graphene sida ay daaha ka qaaday ARPES-ga sare. Marka lagu daro kicinta indhaha ee la xushay, WS2/graphene heterostructure ee la baadhay ayaa laga yaabaa inay bixiso meel si hufan loogu durayo graphene.
Helitaanka waxyaabo badan oo kala duwan oo laba-geesood ah ayaa furay suurtogalnimada in la abuuro sheeko cusub ugu dambeyntii heterostructures khafiif ah oo leh hawlqabadyo cusub oo gebi ahaanba cusub oo ku saleysan baarista dielectric ee ku habboon iyo saameyno kala duwan oo u dhowaanshaha keenay (1-3). Aaladaha caddaynta-mabaadi'da codsiyada mustaqbalka ee berrinka elektiroonigga ah iyo optoelectronics ayaa la xaqiijiyay (4-6).
Halkan, waxaan diirada saareynaa qaab-dhismeedka epitaxial van der Waals heterostructures oo ka kooban monolayer WS2, semiconductor-ka tooska ah ee leh isku xirka wareegga-orbit-ka xooggan iyo kala qaybsanaan weyn oo qaab dhismeedka band ah oo ay ugu wacan tahay summetry rogasho (7), iyo monolayer graphene, semimetal oo leh qaab-dhismeedka koox-kooban iyo dhaq-dhaqaaq side aad u sarreeya (8), oo ku koray hydrogen-ka-joojiyay SiC(0001). Tilmaamaha ugu horreeya ee wareejinta kharashka ultrafast (9-15) iyo udhow-soo-dhoweynta saamaynta isku-xidhka-orbit-ka (16-18) waxay sameeyaan WS2 / graphene iyo heterostructures la mid ah oo ballanqaadaya musharraxiinta mustaqbalka optoelectronic (19) iyo optospintronic (20) codsiyada.
Waxaan dejinay inaan muujino dariiqyada nasashada ee lammaane-hole elektaroonig ah oo sawiran oo ku jira WS2/graphene oo leh waqti- iyo xagal-xalin sawir-qaadista sawir-qaadista (tr-ARPES). Ujeedadaas awgeed, waxaan ku faraxsanahay heterostructure-ka leh 2-eV garaaca garaaca wadnaha ee A-exciton ee WS2 (21, 12) oo ka saarnay sawir-qaadista garaaca wadnaha dib-u-dhigista ee 26-eV tamarta photon. Waxaan go'aamineynaa tamarta kinetic iyo xagasha qiiqa ee sawir-qaadayaasha iyadoo la adeegsanayo falanqeeye hemispherical sida shaqada dib u dhigista bamka-baaritaannada si loo helo dhaqdhaqaaqa-, tamarta-, iyo dhaqdhaqaaqa-waqtiga-xallinta dhaqdhaqaaqa sideyaasha. Xallinta tamarta iyo wakhtiga waa 240 meV iyo 200fs, siday u kala horreeyaan.
Natiijooyinkayagu waxay bixiyaan caddayn toos ah oo ku saabsan wareejinta kharashka ultrafast ee u dhexeeya lakabyada epitaxially ee isku xiran, xaqiijinta calaamadaha ugu horreeya ee ku salaysan dhammaan farsamooyinka indhaha ee qaab-dhismeedka heterostructures ee gacanta la mid ah oo leh isku dheelitirnaanta azimuthal ee lakabyada (9-15). Intaa waxaa dheer, waxaan tuseynaa in wareejinta qarashka ay tahay mid aan asmmetrical ahayn. Cabiraaddayadu waxay daaha ka qaadayaan xaalad ku meel gaadh ah oo kala sooc ah oo aan hore loo arag oo leh elektaroonno sawir leh iyo godad ku yaal WS2 iyo lakabka graphene, siday u kala horreeyaan, u nool ~ 1 ps. Waxaan u turjumeynaa natiijooyinkayaga marka loo eego kala duwanaanshaha booska kala firdhisanaanta marxaladda elektaroonigga ah iyo wareejinta daloolka oo ay sababtay isku-dheellitirka qaraabada ee WS2 iyo xargaha graphene sida ay shaaca ka qaaday ARPES-ga sare. Marka lagu daro firfircoonida indhaha ee lafdhabarta-iyo dooxada-doorashada (22-25) WS2/graphene heterostructures ayaa laga yaabaa inay bixiyaan madal cusub oo wax ku ool ah oo loogu talagalay cirbadeynta indhaha ee ultrafast ee graphene.
Jaantuska 1A wuxuu muujinayaa cabbirka ARPES-ka-sare ee lagu helay nalka helium ee qaab-dhismeedka kooxeed ee weheliya ΓK-jihada epitaxial WS2/graphene heterostructure. Koodhka Dirac waxaa la ogaaday inuu yahay dalool leh barta Dirac oo ku taal ~0.3 eV oo ka sarreysa awoodda kiimikaad ee dheellitirka. Sare ee band-split WS2 valence band waxaa la ogaaday inuu ~ 1.2 eV ka hooseeyo isku dheelitirnaanta awoodda kiimikada.
(A) Sawirka dheellitirka dheellitirka ah oo lagu cabbiray jihada ΓK oo leh nal helium ah oo aan dabada lahayn. (B) Photocurrent ee daahitaanka bamka-baaritaan taban oo lagu cabbiray p-polarized ultraviolet pulses oo ah 26-eV tamar sawireed. Khadadka cawlan iyo casaanka ah ee jajaban waxay calaamadiyaan booska profiles xariiqda loo isticmaalo in lagu soo saaro boosaska ugu sarreeya ee ku meel gaadhka ah ee Jaantuska. oo ah 2 mJ/cm2. Faa'iidada iyo khasaaraha photoelectrons waxaa lagu muujiyey casaan iyo buluug, siday u kala horreeyaan. Sanduuqyadu waxay muujinayaan aagga isdhexgalka ee raadadka bamka-baaritaannada ee lagu muujiyay sawirka 3.
Jaantuska 1B wuxuu muujinayaa sawirka tr-ARPES ee qaab dhismeedka kooxda ee u dhow WS2 iyo graphene K-dhibcaha oo lagu cabiray 100-fs garaaca shucaaca ultraviolet ee 26-eV ee daahitaanka bamka-baarida taban kahor imaatinka garaaca garaaca wadnaha. Halkan, kala-goynta laf-dhabarta lama xalliyo sababta oo ah hoos u dhaca muunadda iyo joogitaanka garaaca garaaca wadnaha ee 2-eV kaas oo sababa balaarinta muuqaalada muuqaalka. Jaantuska 1C waxa uu muujinayaa isbeddelada bamka-ku-abuuray ee sawir-qaadaha marka la eego shaxanka 1B ee dib u dhaca bamka-baadhista ee 200fs halkaas oo calaamada bamka-baaruhu gaadho ugu badnaan. Midabada casaanka iyo buluuga ah waxay muujinayaan faa'iidada iyo khasaaraha photoelectrons, siday u kala horreeyaan.
Si loo falanqeeyo dhaqdhaqaaqa qaniga ah si faahfaahsan, waxaanu marka hore go'aaminaynaa boosaska ugu sarreeya ee ku meel gaadhka ah ee kooxda WS2 valence band iyo graphene π-band ee ku teedsan xariiqyada xadhkaha goostay ee Jaantuska 1B sida si faahfaahsan loogu sharaxay agabka Dheeraadka ah. Waxaan ogaanay in band valence ee WS2 uu kor u kacayo 90 meV (Jaantus. 2A) iyo graphene π-band waxay hoos u dhacaysaa 50 meV (Jaantus. 2B). Cimriga jibbaarka ee isbeddelladan waxaa lagu ogaadaa inay tahay 1.2 ± 0.1 ps qeybta valence ee WS2 iyo 1.7 ± 0.3 ps ee graphene π-band. Isbedelladan ugu sarreeya waxay bixiyaan caddaynta ugu horreysa ee dallacaadda ku meel gaadhka ah ee labada lakab, halkaas oo kharash dheeraad ah oo togan (negative) ay kordho (yarayso) tamarta isku xidhka ee dawladaha elektaroonigga ah. Ogsoonow kor u kaca kooxda WS2 ee valence waxay mas'uul ka tahay calaamada bamka-baaritaanka caanka ah ee aagga lagu calaamadeeyay sanduuqa madow ee shaxanka 1C.
Beddelka booska ugu sarreeya ee WS2 valence band (A) iyo graphene π-band (B) oo ah shaqada dib u dhigista bamka-baarida oo ay weheliso jibbaarada ku habboon (khadadka dhumucda leh). Inta lagu jiro wakhtiga beddelka WS2 ee (A) waa 1.2 ± 0.1 ps. Inta lagu jiro wakhtiga wareegga graphene ee (B) waa 1.7 ± 0.3 ps.
Marka xigta, waxaan isku darsaneynaa calaamada bamka-baaritaanka meelaha lagu tilmaamay sanduuqyada midabada leh ee Jaantuska 1C waxaanan ku dhejineynaa tirooyinka natiijada sida shaqada dib u dhigista bamka-baaritaanka ee sawirka 3. Qalooca 1 ee sawirka 3 ayaa muujinaya dhaqdhaqaaqa dhaqdhaqaaqa qaadeyaal sawir leh oo u dhow xagga hoose ee band conduction ee lakabka WS2 oo leh cimrigooda 1.1 ± 0.1 ps oo laga helay jibbaar ku habboon xogta (eeg agabka Dheeraadka ah).
Raad raadadka bamka-baaraha sida shaqo dib u dhac ah oo la helay iyadoo la isku darayo sawirka hadda jira ee aagga lagu tilmaamay sanduuqyada ku yaal Jaantuska 1C. Xariiqyada qaro weyni waxay ku habboon yihiin xogta. Qalooca (1) Dadka sidaha ku meel gaadhka ah ee ku jira band conduction of WS2. Curve (2) Calaamada bamka-baarida ee π-band of graphene ee ka sarreeya awoodda kiimikaad ee dheellitirka. Curve (3) Calaamada bamka-baarida ee π-band of graphene ee ka hooseeya awoodda kiimikaad ee dheellitirka. Curve (4) Calaamada bamka-baarida saafiga ah ee ku dhex jirta qaybta valence ee WS2. Cimriyada nolosha waxaa lagu ogaadaa inay yihiin 1.2 ± 0.1 ps gudaha (1), 180 ± 20 fs (helitaan) iyo ~ 2 ps (khasaare) gudaha (2), iyo 1.8 ± 0.2 ps gudaha (3).
Qalloocyada 2 iyo 3 ee Jaantuska 3, waxaan ku tusinaa calaamada bamka-baaritaanka ee graphene π-band. Waxaan ogaanay in faa'iidada elektaroonigga ah ee ka sarreeya awoodda kiimikada ee dheellitirka (qallooca 2 ee Jaantuska. 3) ay leedahay nolol aad u gaaban (180 ± 20 fs) marka la barbardhigo luminta elektarooniga ee ka hooseeya awoodda kiimikada dheellitirka (1.8 ± 0.2 ps ee qalooca 3). Sawirka 3). Dheeraad ah, faa'iidada bilawga ah ee sawir-qaadaha ee qalooca 2 ee Jaantuska 3 waxaa la ogaaday in ay isu beddesho khasaare at = 400 fs oo leh cimrigiisu ~ 2 ps. Asymmetry-ga u dhexeeya faa'iidada iyo khasaaraha ayaa la ogaaday in ay ka maqan tahay calaamada bamka-baaritaannada ee graphene monolayer ee daahsoon (eeg fig. S5 ee agabka Dheeraadka ah), taas oo muujinaysa in asymmetry ay tahay natiijada isku-xidhka isku-xidhka WS2/graphene heterostructure. U fiirsashada faa'iidada muddada gaaban iyo khasaaraha cimriga dheer ee ka sarreeya iyo ka hooseeya awoodda kiimikaad ee dheellitirka, siday u kala horreeyaan, waxay muujinaysaa in elektaroonnada si hufan looga saaro lakabka graphene marka la sawiro heterostructure. Natiijadu waxay tahay, lakabka graphene wuxuu noqdaa mid si togan loo dallaco, kaas oo la jaan qaadaya kororka tamarta isku-xidhka ah ee π-band ee laga helo sawirka 2B. Hoos-u-dhaca π-band wuxuu ka saarayaa dabada tamarta sare ee dheellitirka Fermi-Dirac ee ka sarreeya awoodda kiimikada ee dheellitirka, taas oo qayb ahaan sharraxaysa isbeddelka calaamadda calaamadda bamka-baaritaannada ee qalooca 2 ee Jaantuska 3. Hoos ka tus in saamayntani ay sii xoojisay luminta ku-meel-gaadhka ah ee elektarooniga ee π-band.
Muuqaalkan waxa taageeraya calaamada bamka-barista saafiga ah ee band valence WS2 ee qalooca 4 ee Jaantuska 3. Xogtan waxa lagu helay iyada oo la isku daray tirinta goobta uu bixiyay sanduuqa madow ee Jaantuska. band valence ee dhammaan daahitaanka bamka-baaritaannada. Gudaha baararka qaladka tijaabada ah, waxaan u helin wax calaamad u ah joogitaanka godadka ku jira valence band ee WS2 dib u dhac kasta oo bamka-baaritaan ah. Tani waxay muujinaysaa in, ka dib sawir-qaadista, godadkan si degdeg ah ayaa dib loogu buuxinayaa miisaan waqti gaaban marka loo eego xallintayada ku meel gaarka ah.
Si aan u bixino caddaynta kama dambaysta ah ee mala-awaalkayaga kala-soocidda kharashka ultrafast ee WS2/graphene heterostructure, waxaanu go'aaminaynaa tirada godadka loo wareejiyay lakabka graphene sida si faahfaahsan loogu sharraxay agabka Dheeraadka ah. Marka la soo koobo, qaybinta elektarooniga ah ee ku meel gaadhka ah ee π-band waxaa lagu rakibay qaybinta Fermi-Dirac. Tirada godadka ayaa markaa laga xisaabiyay qiimayaasha ka dhashay awoodda kiimikada ku meel gaadhka ah iyo heerkulka elektiroonigga ah. Natiijadu waxay ku caddahay sawirka 4. Waxaan ogaanay in tirada guud ee ~ 5 × 1012 godadka / cm2 laga soo wareejiyay WS2 ilaa graphene oo leh nolol jibbaar ah 1.5 ± 0.2 ps.
Beddelka tirada godadka π-band sida shaqada dib u dhigista bamka-baarida oo ay weheliso taam jibbaarada oo dhalinaya cimri dhan 1.5 ± 0.2 ps.
Laga soo bilaabo natiijooyinka ku jira berdihii. 2 ilaa 4, sawirka soo socda ee microscopic ee wareejinta kharashka ultrafast ee WS2/graphene heterostructure ayaa soo baxaya (Jaantus. 5). Photoexcitation ee WS2/graphene heterostructure ee 2 eV ayaa inta badan ku badan A-exciton gudaha WS2 (Jaantus. 5A). Xamaasad dheeri ah oo elektaroonig ah oo ku taal guud ahaan barta Dirac ee graphene iyo sidoo kale inta u dhaxaysa WS2 iyo guutooyinka graphene ayaa ah kuwo tamar ahaan suurtagal ah laakiin aad u tayo yar. Daloollada sawir-qaadka leh ee ku dhex jira valence band ee WS2 waxaa dib u buuxiya elektaroonno ka soo jeeda graphene π-band oo cabbirkoodu gaaban yahay marka la barbardhigo xallintayada ku meel gaarka ah (Jaantus. 5A). Elektaroonada sawir-qaadka leh ee ku jira band conduction of WS2 waxay leeyihiin cimrigooda ~ 1 ps (Jaantus. 5B). Si kastaba ha ahaatee, waxay qaadataa ~2 ps in dib loo buuxiyo godadka graphene π-band (Jaantus. 5B). Tani waxay muujinaysaa in, marka laga reebo wareejinta tooska ah ee elektaroonigga ah ee u dhexeeya WS2 conduction band iyo graphene π-band, dariiqooyin nasasho oo dheeraad ah - oo laga yaabo in loo maro dawladaha cilladaysan (26) - waxay u baahan yihiin in la tixgeliyo si loo fahmo dhaqdhaqaaqa buuxa.
(A) Photoexcitation at resonance WS2 A-exciton at 2 eV duri elektarooniga band conduction ee WS2. Daloollada u dhigma ee ku dhex jira valence band ee WS2 waxaa isla markiiba dib u buuxiya elektaroonnada graphene π-band. (B) Sideyaasha sawir-qaadka leh ee ku jira band-ka-qaadista ee WS2 waxay haystaan cimrigooda 1 ps. Godadka graphene π-band waxay ku nool yihiin ~ 2 ps, taas oo muujinaysa muhiimada kanaalada fidinta dheeraadka ah ee lagu tilmaamay fallaadho jeexan. Khadadka madow ee ku jira (A) iyo (B) waxay muujinayaan isbeddellada band iyo isbeddelada awoodda kiimikada. (C) Xaaladda ku meel gaadhka ah, lakabka WS2 si xun ayaa loo dallacay halka lakabka graphene si togan loo dallacay. Xamaasad xul ah oo leh iftiin wareeg ah, elektaroonnada sawir-qaadista ee WS2 iyo godadka u dhigma ee graphene ayaa la filayaa inay muujiyaan kala-soocidda lafdhabarta.
Xaaladda ku meel gaadhka ah, elektaroonnada sawir-qabashada leh waxay ku nool yihiin qaybta korantada ee WS2 halka godadka sawir-qaadista ay ku yaalliin π-band of graphene (Jaantus. 5C). Tani waxay ka dhigan tahay in lakabka WS2 si xun loo dallacay oo lakabka graphene si togan loo dallacay. Tani waxay xisaabinaysaa isbeddelada ugu sarreeya ee ku-meel-gaadhka ah (Jaantus. 2), asymmetry ee calaamadda bamka-baaritaanka graphene (qalloocyada 2 iyo 3 ee shaxanka. 3), maqnaanshaha godadka qaybta valence ee WS2 (qallooca 4 Fig. 3) , iyo sidoo kale godadka dheeraadka ah ee graphene π-band (Jaantus 4). Cimrigu inta uu nool yahay gobolkan la kala soocay waa ~1 ps (qallooca 1 Jaantuska. 3).
Dawlado ku meel gaadh ah oo lacag la mid ah ayaa lagu arkay qaab-dhismeedyada heterostructures ee Van der Waals oo laga sameeyay laba kondhondhareer toos ah oo leh nooca II band alignment iyo bandgap jaranjaray (27-32). Ka dib sawir-qaadista, electrons iyo godadka ayaa la ogaaday in ay si degdeg ah ugu guuraan xagga hoose ee band conduction iyo xagga sare ee band valence, siday u kala horreeyaan, kuwaas oo ku yaala lakabyo kala duwan ee heterostructure (27-32).
Marka laga hadlayo WS2/graphene heterostructure, meesha ugu tamarta badan ee electrons iyo godadka labadaba waa heerka Fermi ee lakabka graphene ee macdan. Sidaa darteed, mid ayaa filan kara in labadaba elektaroonnada iyo godadka si degdeg ah ugu wareejiyaan graphene π-band. Si kastaba ha ahaatee, cabbiraadahayadu waxay si cad u muujinayaan in wareejinta daloolka (<200 fs) ay aad uga waxtar badan tahay wareejinta elektaroonigga ah (~ 1 ps). Waxa aanu tan u nisbaynaynaa isku xidhka tamarta tamarta ah ee WS2 iyo guutooyinka graphene sida lagu muujiyey Jaantuska 1A oo bixisa tiro balaadhan oo ah gobolada ugu dambeeya ee la heli karo ee wareejinta godka marka la barbar dhigo wareejinta elektarooniga ah sida dhawaan la filayo (14, 15). Xaaladdan xaadirka ah, iyada oo loo qaadanayo ~ 2 eV WS2 bandgap, barta graphene Dirac iyo awoodda kiimikaad ee dheellitirka ayaa ku yaal ~ 0.5 iyo ~ 0.2 eV oo ka sarreeya bartamaha WS2 bandgap, siday u kala horreeyaan, jebinta summaynta godka elektarooniga ah. Waxaan ogaanay in tirada gobolada kama dambaysta ah ee wareejinta daloolku ay ~ 6 jeer ka weyn tahay wareejinta elektaroonigga ah (eeg agabka Dheeraadka ah), taas oo ah sababta wareejinta daloolka loo filayo inay ka dhaqso badan tahay wareejinta elektaroonigga ah.
Si kastaba ha ahaatee, sawirka buuxa ee microscopic ee wareejinta kharashka ultrafast asymmetric ee la arkay waa, si kastaba ha ahaatee, waa inay sidoo kale tixgelisaa isku-dhafka u dhexeeya orbitals ee ka kooban shaqada wave A-exciton ee WS2 iyo graphene π-band, siday u kala horreeyaan, kala firdhisanaanta elektarooniga ah iyo elektarooniga-phonon Kanaalka oo ay ku jiraan caqabadaha ay soo rogeen xawaaraha, tamarta, lafdhabarta, iyo ilaalinta pseudospin, saameynta oscillations plasma (33), iyo sidoo kale doorka kicinta barakicinta ee suurtogalka ah ee dhawaaqa dhawaaqa isku xidhan ee dhexdhexaadin kara wareejinta dacwada (34, 35). Sidoo kale, waxaa laga yaabaa in la qiyaaso in heerka wareejinta kharashka ee la arkay uu ka kooban yahay xawaalad lacag-bixineed ama lammaane-dalool elektaroonig ah oo bilaash ah (eeg agabka Dheeraadka ah). Baaritaano aragtiyeed oo dheeri ah oo ka baxsan baaxadda warqadda hadda ayaa loo baahan yahay si loo caddeeyo arrimahan.
Marka la soo koobo, waxaan isticmaalnay tr-ARPES si aan u barano ultrafast interlayer charge transfer ee epitaxial WS2/graphene heterostructure. Waxaan ogaanay in, markii aan ku faraxsanahay resonance A-exciton of WS2 at 2 eV, godadka photoexcited si degdeg ah u wareejinta lakabka graphene halka electrons photoexcited ku sii jiraan lakabka WS2. Waxaan tan u nisbaynnay xaqiiqda ah in tirada gobollada kama dambaysta ah ee la heli karo ee wareejinta daloolku ay ka badan yihiin wareejinta elektaroonigga ah. Cimrigu inta uu nool yahay kharashka kala go'ay ee ku meel gaadhka ah waxaa la ogaaday inay tahay ~ 1 ps. Marka lagu daro kicinta indhaha ee la xushay iyadoo la adeegsanayo iftiin wareeg ah (22-25), wareejinta kharashka ultrafast ee la arkay waxaa laga yaabaa inay weheliso wareejinta wareegga. Xaaladdan oo kale, WS2 / graphene heterostructure ee la baadhay ayaa laga yaabaa in loo isticmaalo cirbadeynta indhaha ee wax ku oolka ah ee graphene taasoo keentay qalab cusub oo optospintronic ah.
Tusaalooyinka graphene ayaa lagu koray semiconducting ganacsi 6H-SiC(0001) wafers ka SiCrystal GmbH. Waferrada N-doped-ku waxay ahaayeen dhidibka oo ay si khaldan u jareen 0.5°. Substrate-ka SiC wuxuu ahaa haydarojiin-ku dhejiyay si meesha looga saaro xagashada oo loo helo barxad siman oo joogto ah. Dusha nadiifka ah ee atomically flat ee Si-terminated ayaa markaas la sawiray iyadoo la tirtiray muunada jawiga Ar ee 1300°C 8 daqiiqo (36). Sidan, waxaan ku helnay hal lakab oo kaarboon ah halkaas oo atom kasta oo kaarboon seddexaad uu sameeyay dammaanad isku xiran substrate-ka SiC (37). Lakabkaan ayaa markaa loo rogay gebi ahaanba sp2-hybridized kaasi oo xor ah oo taagan dalool-doped graphene iyada oo loo sii marayo isdhexgalka hydrogen (38). Tusaalooyinkan waxaa loo tixraacaa sida graphene/H-SiC(0001). Geedi socodka oo dhan waxa lagu fuliyay qolka kobaca ee sixirka madow ee Aixtron. Kobaca WS2 waxaa lagu sameeyay reactor-kulul caadi ah oo uumiga kiimikada cadaadiska hooseeya (39, 40) iyadoo la adeegsanayo budada WO3 iyo S oo leh saamiga tirada 1: 100 sida horudhacyada. Budada WO3 iyo S waxa lagu hayaa 900 iyo 200°C, siday u kala horreeyaan. Budada WO3 waxaa la dhigay meel u dhow substrate-ka. Argon waxaa loo isticmaalay sidii gaas side oo leh qulqulka 8 sccm. Cadaadiska reactor-ka waxaa lagu hayaa 0.5 mbar. Tijaabooyinku waxay ku sifoobeen mikroskoobyada elektarooniga ah ee labaad, mikroskoobyada xoogga atomigga, Raman, iyo sawir-qaadista sawir-qaadista, iyo sidoo kale kala-baxa tamarta-yar ee elektarooniga ah. Cabiraadahani waxay daaha ka qaadeen laba qaybood oo kala duwan oo WS2 hal-crystalline ah halkaas oo midkood ΓK- ama ΓK'-jihada uu la socdo ΓK-jihada lakabka graphene. Dhererka dhinaca Domainku wuu kala duwanaa inta u dhaxaysa 300 iyo 700 nm, iyo wadarta guud ee caymiska WS2 ayaa lagu qiyaasay ~40%, oo ku habboon falanqaynta ARPES.
Tijaabooyinka ARPES ee taagan waxaa lagu sameeyay falanqeeye hemispherical (SPECS PHOIBOS 150) iyadoo la adeegsanayo qalab isku xiran-nidaamka ogaanshaha ee ogaanshaha laba-geesoodka ah ee tamarta elektarooniga ah iyo xawaaraha. Unpolarized, monochromatic He Iα shucaaca (21.2 eV) ee qulqulka sare leh Isha dheecaanka leh (VG Scienta VUV5000) ayaa loo isticmaalay dhammaan tijaabooyinka sawir-qaadista. Tamarta iyo xallinta xagasha ee tijaabadeena waxay ka fiicnaayeen 30 meV iyo 0.3 ° (oo u dhiganta 0.01 Å-1), siday u kala horreeyaan. Dhammaan tijaabooyinka waxaa lagu sameeyay heerkulka qolka. ARPES waa farsamo xasaasi ah oo dusha sare leh. Si looga saaro sawir-qaadayaasha WS2 iyo lakabka graphene, muunado leh daboolka WS2 ee aan dhamaystirnayn ee ~ 40% ayaa la isticmaalay.
Habaynta tr-ARPES waxay ku salaysnayd 1-kHz Titanium:Sapphire amplifier (Isku xidhan Legend Elite Duo). 2 mJ ee awoodda wax soo saarka ayaa loo isticmaalay jiilka harmonics sare ee argon. Iftiinka ultraviolet ee ba'an ee ka dhashay wuxuu dhex maray monochromator grating oo soo saaraya garaaca 100-fs ee tamarta 26-eV ee photon. 8mJ ee awoodda wax-soo-saarka cod-weyneeye ayaa loo diray cod-weyneeye parametric optical (HE-TOPAS oo ka yimid beddelka iftiinka). Iftiinka ishaarka ee tamarta 1-eV ee tamarta photon ayaa inta jeer-laba jibaarmay beta barium borate crystal si loo helo garaaca bamka 2-eV. Cabiraadaha tr-ARPES waxaa lagu sameeyay falanqeeye hemispherical (SPECS PHOIBOS 100). Tamarta guud iyo xallinta ku meel gaadhka ah waxay ahayd 240 meV iyo 200fs, siday u kala horreeyaan.
Waxyaabaha dheeriga ah ee maqaalkan ayaa laga heli karaa http://advances.sciencemag.org/cgi/content/full/6/20/eaay0761/DC1
Kani waa maqaal gelitaan furan oo lagu qaybiyey shuruudaha Shatiga Hal-abuurka Caadiga ah -Shatiga Aan Ganacsiga ahayn, kaas oo oggolaanaya isticmaalka, qaybinta, iyo taranka meel kasta, ilaa inta isticmaalka natiijadu aanu ahayn faa'iido ganacsi oo ay bixiso shaqada asalka ah ee saxda ah soo xigtay.
FIIRO GAAR AH: Waxaan kaliya ku codsaneynaa cinwaankaaga iimaylka si qofka aad u soo jeedineyso bogga uu ogaado inaad rabtay inay arkaan, oo aysan ahayn boostada junk. Ma qabno ciwaan email ah
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Waxaa qoray Sven Aeschlimann, Antonio Rossi, Mariana Chávez-Cervantes, Razvan Krause, Benito Arnoldi, Benjamin Stadtmüller, Martin Aeschlimann, Stiven Forti, Filippo Fabbri, Camilla Coletti, Isabella Gierz
Waxaan daaha ka qaadaynaa kala soocida kharashka ultrafast ee WS2/graphene heterostructure oo suurtogal ah in ay suurtageliso cirbadeynta indhaha ee graphene.
Waxaa qoray Sven Aeschlimann, Antonio Rossi, Mariana Chávez-Cervantes, Razvan Krause, Benito Arnoldi, Benjamin Stadtmüller, Martin Aeschlimann, Stiven Forti, Filippo Fabbri, Camilla Coletti, Isabella Gierz
Waxaan daaha ka qaadaynaa kala soocida kharashka ultrafast ee WS2/graphene heterostructure oo suurtogal ah in ay suurtageliso cirbadeynta indhaha ee graphene.
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Waqtiga boostada: Meey-25-2020