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Sufferings allows you to learn more!
Hope to be better next time.
Title: Determining Fermi level by absorption quenching of monolayer graphene by charge transfer doping
Author : Subash Adhikari, David J. Perello, Chandan Biswas, Arunabha Ghosh, Nguyen Van Luan, Jihoon Park, Fei Yao, Slava V.Rotkin and Young Hee Lee
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 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(trifluoromethanesulfon)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. Measuring simple UV-Visible transmittance spectroscopy to obtain absorption quenching onset of graphene also allows detection of environmental and substrate effect via Fermi level shift. Our method opens up the practical implementation of this unique phenomenon of graphene in future optoelectronic devices.