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Photochemical Doping and Tuning of the Work Function and Dirac Point in Graphene Using Photoacid and Photobase Generators
Author(s) -
Baltazar Jose,
Sojoudi Hossein,
Paniagua Sergio A.,
Zhang Siyuan,
Lawson Richard A.,
Marder Seth R.,
Graham Samuel,
Tolbert Laren M.,
Henderson Clifford L.
Publication year - 2014
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.201303796
Subject(s) - graphene , materials science , doping , ultraviolet , work function , dopant , optoelectronics , photochemistry , ionic bonding , nanotechnology , chemical engineering , ion , layer (electronics) , organic chemistry , chemistry , engineering
This work demonstrates that photochemical doping of CVD‐grown graphene can be easily achieved using photoacid (PAG) and photobase (PBG) generators such as triphenylsulfonium perfluoro‐1‐butanesufonate (TPS‐Nf) and 2‐nitrobenzyl N ‐cyclohexylcarbamate (NBC). The TPS‐Nf ionic onium salt photoacid generator does not noticeably dope or alter the electrical properties of graphene when coated onto the graphene surface, but is very effective at inducing p‐doping of graphene upon exposure of the PAG‐coated graphene sample. Likewise, the neutral NBC photobase generator does not significantly affect the electrical properties of graphene when coated, but upon exposure to ultraviolet light produces a free amine, which induces n‐doping of the graphene. Electrical measurements show that the doping concentration can be modulated by controlling the deep ultraviolet (DUV) light exposure dose delivered to the sample. The interaction between both dopants and graphene is also investigated. The photochemical doping process is able to tune the work function of the single‐layer graphene samples used in this work from 3.4 eV to 5.3 eV. Finally, a p–n junction is fabricated and analyzed, showing that it is possible to control the position of the two current minima (two Dirac points) in the ambipolar p–n junction.