Synthesis and intercalation of epitaxial graphene on iridium

doctoral thesis

• Title (croatian): Sinteza i interakcija epitaksijalnog grafena na iridiju
• Author: Marin Petrović
• Mentor: Marko Kralj (mentor)
• Committee member: Amir Hamzić (predsjednik povjerenstva)
• Committee member: Marko Kralj (član povjerenstva)
• Committee member: Thomas Michely (član povjerenstva); strani drzavljanin: Nije dostupno
• Committee member: Goranka Bilalbegović (član povjerenstva)
• Committee member: Hrvoje Buljan (član povjerenstva)
• Granter: University of Zagreb; Faculty of Science; (Department of Physics); Zagreb
• Defense date and country: 2014-10-10, Croatia
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Physics
• Universal decimal classification (UDC): 53 - Physics

Abstract

Epitaxial graphene on iridium (111) surface is considered to be one of the best systems for studying intrinsic properties of graphene due to the weak interaction with the substrate which is predominantly of the van der Waals character. In epitaxial systems, graphene’s properties can be modified or some new ones can be induced by the processes of intercalation of various atoms or molecules in between the graphene and the substrate. Therefore, a detailed understanding of the formation of such hybrid systems, from graphene synthesis to its intercalation, is crucial for their complete understanding. In this thesis, results relevant for the growth and intercalation of epitaxial graphene synthesized on Ir(111) are presented. By utilizing well-established procedures for graphene synthesis, samples with various graphene coverages are prepared in order to characterize the growth of graphene in detail. Different species (specifically, Cs, Li, Eu and O) are also deposited on such samples which results in the formation of new, hybrid (and most often intercalated) systems whose properties depend on the exact preparation parameters. In order to characterize the morphology, low energy electron microscopy (LEEM) and scanning tunneling microscopy (STM) are used while the electronic structure is investigated by means of angle-resolved photoemission spectroscopy (ARPES) and two-photon photoemission spectroscopy (2PPE). The growth of graphene is characterized on a microscopic level, focusing on small graphene islands and their interaction with iridium. For a complete graphene monolayer, a network of graphene wrinkles is studied. It is found that such network exhibits ordering on the micrometer scales dictated by the substrate. Occupied and unoccupied electronic structure in the vicinity of the Brillouin zone center is investigated via spectroscopic techniques establishing basic relations between the states located below and above the Fermi level. From the aspect of intercalation, Cs deposition on well defined graphene layer is studied and emerging spectroscopic and morphological features are characterized. By this, a novel mechanism of intercalation and the corresponding dynamics behind it are revealed. A competition between Coulomb and van der Waals interactions turns out to be crucial in such epitaxial systems. In addition, intercalation of Li, Eu and O are characterized with special emphasis on the electronic structure at the K point of the Brillouin zone which gives new insight on the influence of various intercalated layers on the surface states of iridium.

Abstract (croatian)

Epitaksijalni grafen na iridiju (111) se smatra jednim od najboljih sistema za proučavanje intrinzičnih svojstava grafena zbog slabog međudjelovanja s podlogom koje je dominantno van der Waals tipa. U epitaksijalnim sistemima, svojstva grafena se mogu mijenjati ili se čak mogu inducirati neka nova u procesima interkalacije različitih atoma ili molekula između grafena i podloge. Stoga je detaljno razumijevanje nastanka takvih hibridnih sistema, od sinteze grafena do njegove interkalacije, ključno za njihovo potpuno razumijevanje. U ovom radu su prezentirani rezultati relevantni za rast i interkalaciju epitaksijalnog grafena sintetiziranog na Ir(111). Korištenjem dobro utvrđenih postupaka za sintezu, pripremljeni su uzorci s različitim pokrivenostima iridijeve površine grafenom kako bi se detaljno okarakterizirao njegov rast. Na takve uzorke naneseni su drugi kemijski elementi (specifično, Cs, Li Eu i O) što je rezultiralo stvaranjem novih, hibridnih (i najčešće interkaliranih) sistema čija svojstva ovise o konkretnim parametrima pripreme. Za karakterizaciju morfologije se koriste nisko-energetska elektronska mikroskopija (LEEM) i pretražna tunelirajuća mikroskopija (STM) dok se elektronska struktura istražuje kutno-razlučivom fotoemisijskom spektroskopijom (ARPES) i dvo-fotonsko fotoemisijskom spektroskopijom (2PPE). Rast grafena je karakteriziran na mikroskopskom nivou sa posebnim fokusom na malene grafenske otoke i njihovo međudjelovanje s iridijem. Za cjeloviti grafenski sloj, istražena su svojstva mreže grafenskih nabora te je nađeno da takva mreža pokazuje uređenost na mikrometarskim skalama koja je određena s podlogom. Pomoću spektroskopskih tehnika je istražena popunjena i nepopunjena elektronska struktura u blizini centra Brillouinove zone čime su uspostavljene osnovne veze između stanja koja se nalaze ispod i iznad Fermijevog nivoa. S aspekta interkalacije, obavljena je spektroskopska i morfološka karakterizacija depozicije cezija na dobro definiran grafenski sloj. Pri tome je otkriven novi mehanizam interkalacije kao i odgovarajuća dinamika koja je vezana uz taj proces. Pokazuje se da je natjecanje između van der Waals i Coulomb međudjelovanja od ključne važnosti u epitaksijalnim sistemima. Dodatno, okarakterizirana je interkalacija litija, europija i kisika sa posebnim naglaskom na elektronsku strukturu u blizini K točke Brillouinove zone čime je dobiven novi uvid u utjecaj različitih interkaliranih slojeva na površinska stanja iridija.

• Keywords: epitaxial graphene; iridium; intercalation; temperature programmed growth; TPG; wrinkles; graphene islands; surface states; image-potential states
• Keywords (croatian): epitaksijalni grafen; iridij; interkalacija; temperaturno programirani rast; TPG; grafenski nabori; grafenski otoci; površinska stanja; stanja zrcalnog potencijala
• Language: english
• URN:NBN: urn:nbn:hr:217:680505
• Study programme: Title: Physics; Study programme type: university; Study level: postgraduate; Academic / professional title: doktor/doktorica znanosti, područje prirodnih znanosti, polje fizika (doktor/doktorica znanosti, područje prirodnih znanosti, polje fizika)
• Type of resource: Text
• Extent: 143 str.
• File origin: Born digital
• Access conditions: Open access
• Created on: 2017-08-23 07:49:02