TY - JOUR
T1 - Modulating the charge-transfer enhancement in GERS using an electrical field under vacuum and an n/p-doping atmosphere
AU - Xu, Hua
AU - Chen, Yabin
AU - Xu, Weigao
AU - Zhang, Haoli
AU - Kong, Jing
AU - Dresselhaus, Mildred S.
AU - Zhang, Jin
PY - 2011/10/17
Y1 - 2011/10/17
N2 - The modulation of charger-transfer (CT) enhancement in graphene-enhanced Raman scattering (GERS) by an electric field under different atmospheres is reported. The GERS spectra of cobalt phthalocyanine (CoPc) molecules were collected by in situ Raman measurements under ambient air, vacuum, NH 3 atmosphere, and O 2 atmosphere, in which the Fermi level of graphene was modulated by an electrical field effect (EFE). The Raman scattering intensities of adsorbed molecules can be tuned to be stronger or weaker as the graphene Fermi level down-shifts or up-shifts under electrical field modulation. However, the Raman intensity modulation in GERS is seriously influenced by the hysteresis effect in graphene EFE, which makes the modulation ability small and shows strong gate voltage sweep rate dependence in ambient air. Fortunately, the hysteresis effect in graphene EFE can be decreased by performing the measurement under vacuum conditions, and thus the Raman modulation ability in GERS can be increased. Furthermore, compared with the vacuum condition, the Raman modulation ability shows an increase under an NH 3 atmosphere, while it shows a decrease under an O 2 atmosphere, which is due to the different Fermi level modulation region in different atmospheres. More interestingly, this Raman intensity modulation in GERS shows a hysteresis-like behavior that is the same as the graphene Fermi level modulation under the EFE in a different atmosphere. All these observations suggest that the Raman enhancement in GERS occurs through a charge-transfer (CT) enhancement mechanism and the CT process can be modulated by the graphene EFE. This technique will benefit the study of the basic properties of both graphene and chemical enhancement mechanism in surface-enhanced Raman spectroscopy (SERS). The modulation of charger-transfer (CT) enhancement in graphene-enhanced Raman scattering (GERS) by tuning the graphene Fermi level with an electric field in different atmospheres is presented. The Raman scattering intensities of molecules on graphene can be made strong or weak by applying an electric field, and the modulation behavior shows an obvious difference measured in ambient air, vacuum, NH 3(n-doping) atmosphere, and O 2(p-doping) atmosphere.
AB - The modulation of charger-transfer (CT) enhancement in graphene-enhanced Raman scattering (GERS) by an electric field under different atmospheres is reported. The GERS spectra of cobalt phthalocyanine (CoPc) molecules were collected by in situ Raman measurements under ambient air, vacuum, NH 3 atmosphere, and O 2 atmosphere, in which the Fermi level of graphene was modulated by an electrical field effect (EFE). The Raman scattering intensities of adsorbed molecules can be tuned to be stronger or weaker as the graphene Fermi level down-shifts or up-shifts under electrical field modulation. However, the Raman intensity modulation in GERS is seriously influenced by the hysteresis effect in graphene EFE, which makes the modulation ability small and shows strong gate voltage sweep rate dependence in ambient air. Fortunately, the hysteresis effect in graphene EFE can be decreased by performing the measurement under vacuum conditions, and thus the Raman modulation ability in GERS can be increased. Furthermore, compared with the vacuum condition, the Raman modulation ability shows an increase under an NH 3 atmosphere, while it shows a decrease under an O 2 atmosphere, which is due to the different Fermi level modulation region in different atmospheres. More interestingly, this Raman intensity modulation in GERS shows a hysteresis-like behavior that is the same as the graphene Fermi level modulation under the EFE in a different atmosphere. All these observations suggest that the Raman enhancement in GERS occurs through a charge-transfer (CT) enhancement mechanism and the CT process can be modulated by the graphene EFE. This technique will benefit the study of the basic properties of both graphene and chemical enhancement mechanism in surface-enhanced Raman spectroscopy (SERS). The modulation of charger-transfer (CT) enhancement in graphene-enhanced Raman scattering (GERS) by tuning the graphene Fermi level with an electric field in different atmospheres is presented. The Raman scattering intensities of molecules on graphene can be made strong or weak by applying an electric field, and the modulation behavior shows an obvious difference measured in ambient air, vacuum, NH 3(n-doping) atmosphere, and O 2(p-doping) atmosphere.
KW - Raman spectroscopy
KW - charge-transfer
KW - electric field modulation
KW - graphene
KW - mechanisms
UR - http://www.scopus.com/inward/record.url?scp=80054018921&partnerID=8YFLogxK
U2 - 10.1002/smll.201100546
DO - 10.1002/smll.201100546
M3 - Article
C2 - 21901822
AN - SCOPUS:80054018921
SN - 1613-6810
VL - 7
SP - 2945
EP - 2952
JO - Small
JF - Small
IS - 20
ER -