title: Determining the Fermi level by absorption quenching of monolayer graphene by charge transfer doping.
abstract: While optical properties of graphene in the visible region are solely defined by the frequency-independent fine structure constant, an onset of absorption has been observed in the infrared region due to Pauli blocking of interband transitions. Here, we report a complete absorption quenching in the infrared region by coating graphene with bis(trifluoromethanesulfonyl)amine (TFSA), an optically transparent p-type chemical dopant. The Fermi level downshift due to TFSA doping results in enhanced transmission in the infrared region proportional to the doping concentration. An absorption quenching onset method, developed in our work, to extract the Fermi level shift in pristine and doped graphene agrees with values extracted from Raman G-band and 2D-band shifts, Hall measurements and the binding energy shift observed in X-ray photo-electron spectroscopy. Performing simple UV-visible transmittance spectroscopy to obtain the absorption quenching onset of graphene also allows detection of environmental and substrate effects via Fermi level shift. Our method opens up the practical implementation of this unique phenomenon of graphene in future optoelectronic devices.
authors: Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS), Suwon 16419, Republic of Korea. leeyoung@skku.edu and Department of Energy Science, Department of Physics, Sungkyunkwan University, Suwon 16419, Republic of Korea.
authors: Subash
authors: S
authors: Adhikari
authors: Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS), Suwon 16419, Republic of Korea. leeyoung@skku.edu.
authors: David J
authors: DJ
authors: Perello
authors: Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS), Suwon 16419, Republic of Korea. leeyoung@skku.edu.
authors: Chandan
authors: C
authors: Biswas
authors: Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS), Suwon 16419, Republic of Korea. leeyoung@skku.edu.
authors: Arunabha
authors: A
authors: Ghosh
authors: Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS), Suwon 16419, Republic of Korea. leeyoung@skku.edu.
authors: Nguyen Van
authors: NV
authors: Luan
authors: Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS), Suwon 16419, Republic of Korea. leeyoung@skku.edu.
authors: Jihoon
authors: J
authors: Park
authors: Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS), Suwon 16419, Republic of Korea. leeyoung@skku.edu.
authors: Fei
authors: F
authors: Yao
authors: Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS), Suwon 16419, Republic of Korea. leeyoung@skku.edu and Department of Physics, Center for Advanced Materials and Nanotechnology, Lehigh University, PA 18015, USA.
authors: Slava V
authors: SV
authors: Rotkin
authors: Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS), Suwon 16419, Republic of Korea. leeyoung@skku.edu and Department of Energy Science, Department of Physics, Sungkyunkwan University, Suwon 16419, Republic of Korea.
authors: Young Hee
authors: YH
authors: Lee