TY - JOUR

T1 - F4-TCNQ on Epitaxial Bi-Layer Graphene

T2 - Concentration- and Orientation-Dependent Charge Transfer at the Interface

AU - Chattopadhyay, Sudeshna

AU - Munya, Vikas

AU - Kumar, Ravinder

AU - Pal, Dipayan

AU - Bandyopadhyay, Sucheta

AU - Ghosh, Arpan

AU - Yogi, Priyanka

AU - Koch, Julian

AU - Pfnür, Herbert

N1 - Funding Information: We acknowledge support from the Deutsche Akademischer Austauschdienst (DAAD) who funded the project under the “A New Passage to India” program between Leibniz Universität Hannover and Indian Institute of Technology Indore. We would also like to acknowledge Project No. SR/FST/PSI/225/2016 under the FIST program of the DST, Government of India, for Raman characterization facility. This work is partially supported by the Science and Engineering Research Board (SERB), India Project No: CRG/2020/005595. V.M. is thankful to CSIR-UGC, New Delhi, under the UGC-Ref. No.: 1364/(CSIR-UGC NET JUNE 2018), and R.K. is thankful to DST-INDIA, New Delhi, under the Award No. IF190536 for providing the fellowships.

PY - 2022/12/27

Y1 - 2022/12/27

N2 - Bi-layer epitaxial graphene (BLG) on 6H-SiC(0001) (EG/SiC) was grown and modified by thermal deposition of the molecular electron acceptor tetrafluoro-tetra cyano quinodimethane (F4-TCNQ). The surface-modified system, F4-TCNQ/EG/SiC, was studied by X-ray photoelectron spectroscopy (XPS) and angle-resolved polarized Raman spectroscopy (ARPRS). XPS results indicate that bonding of deposited F4-TCNQ molecules depends on their concentration. Although bonding through the cyano groups is present at all concentrations, charge transfer from graphene to fluorine is evident only at sub-monolayer concentrations. The corresponding change in bond character is coupled with a change in molecular orientation. Raman spectroscopy not only provides results consistent with the findings from the XPS study but also reveals a significant degree of molecular stacking above the monolayer concentration. Thus, both the variation of the acceptor concentration and the number of graphene layers provide further handles to manipulate charge and doping that may be useful in device applications.

AB - Bi-layer epitaxial graphene (BLG) on 6H-SiC(0001) (EG/SiC) was grown and modified by thermal deposition of the molecular electron acceptor tetrafluoro-tetra cyano quinodimethane (F4-TCNQ). The surface-modified system, F4-TCNQ/EG/SiC, was studied by X-ray photoelectron spectroscopy (XPS) and angle-resolved polarized Raman spectroscopy (ARPRS). XPS results indicate that bonding of deposited F4-TCNQ molecules depends on their concentration. Although bonding through the cyano groups is present at all concentrations, charge transfer from graphene to fluorine is evident only at sub-monolayer concentrations. The corresponding change in bond character is coupled with a change in molecular orientation. Raman spectroscopy not only provides results consistent with the findings from the XPS study but also reveals a significant degree of molecular stacking above the monolayer concentration. Thus, both the variation of the acceptor concentration and the number of graphene layers provide further handles to manipulate charge and doping that may be useful in device applications.

UR - http://www.scopus.com/inward/record.url?scp=85143986089&partnerID=8YFLogxK

U2 - 10.1021/acs.langmuir.2c02676

DO - 10.1021/acs.langmuir.2c02676

M3 - Article

C2 - 36512752

AN - SCOPUS:85143986089

VL - 38

SP - 16067

EP - 16072

JO - LANGMUIR

JF - LANGMUIR

SN - 0743-7463

IS - 51

ER -