Influence of a gold substrate on the optical properties of graphene

Abstract

Spectroscopic ellipsometry combined with measurements of electrical characteristics and Kelvin probe force microscopy have been employed to investigate the interaction between graphene and a gold substrate, and the consequent changes of graphene's complex refractive index on gold. A strong blue shift, as much as 350 meV, of the prominent absorption peak (exciton-shifted M-point Van Hove singularity in the ultraviolet range) of graphene has been observed, with respect to the peak position for the sample on an insulating substrate where this peak was observed at about 4.55 eV. The results show that an interaction between graphene and a gold substrate can be characterized through the change of graphene's optical properties. In addition, the effects that a water layer trapped between graphene and gold during the transfer process has on the charge transfer between graphene and the gold substrate have been investigated.

Hybrid nanostructures of metal/two-dimensional nanomaterials for plasmon-enhanced applications

“…Inserting a thin dielectric such as HfO 2 , Al 2 O 3 , or water between the graphene layer and the metal NPs is an efficient method to reduce the plasmon damping process on graphene. 282,283 Although the plasmonic resonance of metal NPs is tunable by simply placing the metal NPs and graphene together, i.e., the metal NPs are placed on top of graphene, the shift is too slight to attain adequate light modulation. Based on experimental studies of plasmons in NP dimers, the plasmonic resonance can also be tailored through a spacer component between the NPs.…”

“…In addition to the fact that the plasmonic resonance of metal nanomaterials can be tailored by 2D materials, the absorption peak of 2D materials can also be changed in the hybrid nanostructures of metal nanomaterials and 2D materials. 283 Theoretically, the plasmonic resonance-induced local fields with high electromagnetic energy near the interface of metal NPs and the medium modify the dielectric/optical properties of the medium. 311 The optical properties of graphene ( Fig.…”

Fresnel coefficients of a two-dimensional atomic crystal

“…This is due to a multiple-reflection effect that enhances the visibility of the atomically thin layer, where the optical properties of the 2D crystal play a fundamental role. Measurements of the optical dielectric functions of 2D crystals by spectroscopic ellipsometry have already been reported [15][16][17][18][19][20]. The interpretation of these results relies on a model of the monolayer treated as a homogeneous medium with an effective thickness [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20].…”

Optical Constants of Chemical Vapor Deposited Graphene for Photonic Applications

“…However, the measured dielectric functions show more than 20% differences, caused not only by the graphene production technique, the effect of the substrate, or the quality of graphene but also by the use of different ellipsometric models and respective initial assumptions. For instance, in the analysis of optical properties, one can take into account the adsorption of water [ 18 , 28 , 30 , 31 , 32 ] and polymer residues [ 18 , 19 ] on graphene used for the transfer of both CVD and exfoliated graphene. Therefore, despite extensive research efforts devoted to studying monolayer graphene’s optical response, optical constants’ choice remains challenging due to the lack of consensus in the field.…”