Spatially mapping work function changes and defect evolution in the fluorination of graphene

Bin Leong Ong, Sheau Wei Ong, Bo Liu, Chao Sung Lai, Harman Johll, Hway Chuan Kang, Eng Soon Tok

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

Abstract

When graphene supported on SiO2 is fluorinated, XPS reveals an increase in concentration of chemically-adsorbed fluorine (higher F/C ratio with C-CF, C-CF2, C-F and C-F2 but no C-F3) on the graphene surface with time. Raman ID/IG ratio, i.e. a measure of non-sp2to Sp2 bonding states, increases with time before showing a decrease suggesting a surface morphology change owing to C-F bonding followed by disordering of the π-electron system. AFM surface morphology scans reveal that defects (holes), which increases in size with time, are observed to form preferentially at the boundary of the graphene flakes. Synchronized Kelvin-Probe Force-Microscopy (KPFM) mapping of the graphene region surrounding these holes shows a higher work-function, φ, giving rise to a donut-shape contact potential difference (CPD) which increases from 4.9 ± 0.1 eV to 5.4 ± 0.1 eV with fluorination. Together with XPS and Raman results, the increase in φ can be attributed to the presence of a higher concentration of fluorine in the graphene region (C-F/C-F2 bonds) surrounding these holes. The formation of the hole-defects on graphene and its subsequent increase in size with fluorination is thus a result of aggregation of adsorbed fluorine and removal of carbon likely in the form of CF4 or C2F4.

Original languageEnglish
Title of host publication2019 IEEE 9th International Nanoelectronics Conferences, INEC 2019
PublisherInstitute of Electrical and Electronics Engineers Inc.
ISBN (Electronic)9781728112374
DOIs
StatePublished - Jul 2019
Event9th IEEE International Nanoelectronics Conferences, INEC 2019 - Kuching, Malaysia
Duration: 3 Jul 20195 Jul 2019

Publication series

Name2019 IEEE 9th International Nanoelectronics Conferences, INEC 2019

Conference

Conference9th IEEE International Nanoelectronics Conferences, INEC 2019
Country/TerritoryMalaysia
CityKuching
Period3/07/195/07/19

Keywords

  • Fluorinated-graphene
  • Kelvin-Probe Force Microscopy (KPFM)

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