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Plasma bromination of HOPG surfaces: a NEXAFS and synchrotron XPS study

  • Br bonding on plasma brominated graphite surfaces has been studied by using Near Edge X-ray Absorption Fine Structure (NEXAFS) and X-ray Photoelectron Spectroscopy (XPS). Br2 and bromoform were used as plasma gases in an r.f. cw low pressure plasma process. Kr plasma had been used to study separately the physical and chemical plasma etching effects. At early steps of plasma bromination which lead to only small XPS Br surface concentration values a quick decay of aromaticity has been observed. At low Br surface concentration radical or even electrophilic addition of bromine onto sp2 carbon atoms is discussed as the dominating reaction pathway. At higher Br surface concentrations the inherent formation of sp3 defects in the graphene network by chemical etching processes promotes nucleophilic substitution of bromine at sp3 carbons as a competing reaction pathway. Both reaction pathways lead to C–Br species characterized by the same Br 3d XPS binding energy. However more than one Br 3dBr bonding on plasma brominated graphite surfaces has been studied by using Near Edge X-ray Absorption Fine Structure (NEXAFS) and X-ray Photoelectron Spectroscopy (XPS). Br2 and bromoform were used as plasma gases in an r.f. cw low pressure plasma process. Kr plasma had been used to study separately the physical and chemical plasma etching effects. At early steps of plasma bromination which lead to only small XPS Br surface concentration values a quick decay of aromaticity has been observed. At low Br surface concentration radical or even electrophilic addition of bromine onto sp2 carbon atoms is discussed as the dominating reaction pathway. At higher Br surface concentrations the inherent formation of sp3 defects in the graphene network by chemical etching processes promotes nucleophilic substitution of bromine at sp3 carbons as a competing reaction pathway. Both reaction pathways lead to C–Br species characterized by the same Br 3d XPS binding energy. However more than one Br 3d component in XP spectra has been found at lower Br2 plasma induced Br surface concentrations and complexation of bromine at HOPG is assumed as a third way of interaction with Br2 plasma.zeige mehrzeige weniger

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Metadaten
Autor*innen:Andreas Lippitz, Jörg Florian Friedrich, Wolfgang UngerORCiD
Dokumenttyp:Zeitschriftenartikel
Veröffentlichungsform:Verlagsliteratur
Sprache:Englisch
Titel des übergeordneten Werkes (Englisch):Surface science
Jahr der Erstveröffentlichung:2013
Verlag:Elsevier
Verlagsort:Amsterdam
Jahrgang/Band:611
Erste Seite:L1
Letzte Seite:L7
Freie Schlagwörter:Graphite; HOPG; Low pressure plasma; NEXAFS; Plasma bromination; XPS
DOI:10.1016/j.susc.2013.01.020
ISSN:0039-6028
Verfügbarkeit des Dokuments:Datei im Netzwerk der BAM verfügbar ("Closed Access")
Datum der Freischaltung:20.02.2016
Referierte Publikation:Ja
Datum der Eintragung als referierte Publikation:28.03.2013
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