TY - GEN
T1 - Spatially mapping work function changes and defect evolution in the fluorination of graphene
AU - Ong, Bin Leong
AU - Ong, Sheau Wei
AU - Liu, Bo
AU - Lai, Chao Sung
AU - Johll, Harman
AU - Kang, Hway Chuan
AU - Tok, Eng Soon
N1 - Publisher Copyright:
© 2019 IEEE.
PY - 2019/7
Y1 - 2019/7
N2 - 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.
AB - 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.
KW - Fluorinated-graphene
KW - Kelvin-Probe Force Microscopy (KPFM)
UR - http://www.scopus.com/inward/record.url?scp=85073880709&partnerID=8YFLogxK
U2 - 10.1109/INEC.2019.8853850
DO - 10.1109/INEC.2019.8853850
M3 - Conference contribution
AN - SCOPUS:85073880709
T3 - 2019 IEEE 9th International Nanoelectronics Conferences, INEC 2019
BT - 2019 IEEE 9th International Nanoelectronics Conferences, INEC 2019
PB - Institute of Electrical and Electronics Engineers Inc.
T2 - 9th IEEE International Nanoelectronics Conferences, INEC 2019
Y2 - 3 July 2019 through 5 July 2019
ER -