Abstract
Graphene doped by lithium atoms supports a strong Dirac plasmon, a weak acoustic plasmon and a strong interband plasmon Li(π + σ). Here we demonstrate that applying a positive or negative bias on the lithium-doped graphene causes the appearance (‘switching ON’) or disappearance (‘switching OFF’) of the Li(π + σ) plasmon and the ‘conversion’ of the Dirac plasmon into a strong acoustic plasmon. This has two important consequences: 1. bias-controlled UV optical activity of the Li-doped graphene and 2. bias-controlled position of the 2D plasmon centroid. These effects turn out to be very robust and independent of the details of the experimental setup, which means that they should be easily experimentally verified, and very attractive for potential applications.
Highlights
Experimental study of the crystal and electronic structure of single-layer graphene (SLG) on the Al2O31–5, SiO26–8, or SiC9–12 substrates obtained by chemical-vapor deposition (CVD) and/or exfoliation techniques is a widely explored methodology and becomes a routine
The plasmonic properties of the graphene epitaxial growth on metallic surfaces, such as Pt(111), Cu(111), or Ir(111) have been extensively studied[38,39,40,41], and it has been shown that the metallic surface abundantly donates electrons to the graphene π band so that it supports a strong Dirac plasmon (DP), which modifies under the influence of strong metallic screening and becomes an acoustic plasmon, which authors called ’sheet plasmon resonance’
We investigate the intensity of the 2D plasmons in lithium-doped graphenes LiCx; x = 2, 6 deposited on the Al2O3 surface, where special attention is paid to exploring how the additional hole or electron injection, achieved through electrostatic bias, influences the interplay between the intra-band DP and the intra-band acoustic plasmon (AP), and ’switches ON or OFF’ the interband Li(π + σ) plasmon
Summary
Experimental study of the crystal and electronic structure of single-layer graphene (SLG) on the Al2O31–5, SiO26–8, or SiC9–12 substrates obtained by chemical-vapor deposition (CVD) and/or exfoliation techniques is a widely explored methodology and becomes a routine. The plasmonic properties of doped graphene on Al2O3, SiO2, or SiC in infrared and THz frequency range (interesting for application) have been experimentally and theoretically widely explored[3,4,10,11,12,18,19,20] These experimental studies show that graphene, when doped by electron donors or acceptors, supports a collective electronic mode called the Dirac plasmon (DP), which can be exploited in many plasmonics applications[21,22,23,24,25,26,27,28,29,30]. The Dirac and acoustic plasmons in the lithium-doped and cesium-doped graphene on Ir (111) surfaces have been studied theoretically[46]
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