Active Control of Surface Plasmons in MXenes for Advanced Optoelectronics
AuthorsEl Demellawi, Jehad K.
AdvisorsAlshareef, Husam N.
ProgramMaterial Science and Engineering
KAUST DepartmentPhysical Science and Engineering (PSE) Division
Embargo End Date2021-12-31
Permanent link to this recordhttp://hdl.handle.net/10754/666285
MetadataShow full item record
Access RestrictionsAt the time of archiving, the student author of this dissertation opted to temporarily restrict access to it. The full text of this dissertation will become available to the public after the expiration of the embargo on 2021-12-31.
AbstractMXenes, a new class of two-dimensional (2D) materials, have recently demonstrated impressive optoelectronic properties associated with its ultrathin layered structure. Particularly, Ti3C2Tx, the most studied MXene by far, was shown to exhibit intense surface plasmons (SPs), i.e. collective oscillations of free charge carriers, when excited by electromagnetic waves. However, due to the lack of information about the spatial and energy variation of those SPs over individual MXene flakes, the potential use of MXenes in photonics and plasmonics is still marginally explored. Hence, the main objective of this dissertation is to shed the light upon the plasmonic behavior of MXenes at the nanoscale and extend their use beyond their typical electrochemical applications. To fulfill our objective, we first elucidated the underlying characteristics governing the plasmonic behavior of MXenes. Then, we revealed the existence of various tunable SP modes supported by different MXenes, i.e. Ti3C2Tx and Mo2CTx, and investigated their energy and spatial distribution over individual flakes. Further, we fabricated an array of MXene-based flexible photodetectors that only operate at the resonant frequency of the SPs supported by MXenes. We also unveiled the existence of tunable SPs supported by another 2D nanomaterial (i.e. MoO2) and juxtaposed its plasmonic behavior with that of MXenes, to underline the uniqueness of the latter. Noteworthy, as in the case of MXenes, this was the first progress made on studying specific SP modes supported by MoO2 nanostructures. In this part of the dissertation, we were able to identify and tailor multipolar SPs supported by MoO2 and illustrate their dependence on their bulk band structure. In the end, we show that, on the contrary, SPs in MXenes are mainly controlled by the surface band structure. To confirm this, we selectively altered the subsurface band structure of Ti3C2Tx and modulated its work function (from 4.37 to 4.81 eV) via charge transfer doping. Interestingly, thanks to the unchanged surface stoichiometry of Ti3C2Tx, the plasmonic behavior of Ti3C2Tx was not affected by its largely tuned electronic structure. Notably, the ability to attain MXenes with tunable work functions, yet without disrupting their plasmonic behavior, is appealing to many application fields.
CitationEl Demellawi, J. K. (2020). Active Control of Surface Plasmons in MXenes for Advanced Optoelectronics. <i>KAUST Research Repository</i>. https://doi.org/10.25781/KAUST-V4R90
Showing items related by title, author, creator and subject.
Plasmonic percolation: Plasmon-manifested dielectric-to-metal transitionChen, Huanjun; Wang, Feng; Li, Kun; Woo, Katchoi; Wang, Jianfang; Li, Quan; Sun, Ling Dong; Zhang, Xixiang; Lin, Haiqing; YAN, Chunhua (ACS Nano, American Chemical Society (ACS), 2012-07-11) [Article]Percolation generally refers to the phenomenon of abrupt variations in electrical, magnetic, or optical properties caused by gradual volume fraction changes of one component across a threshold in bicomponent systems. Percolation behaviors have usually been observed in macroscopic systems, with most studies devoted to electrical percolation. We report on our observation of plasmonic percolation in Au nanorod core-Pd shell nanostructures. When the Pd volume fraction in the shell consisting of palladium and water approaches the plasmonic percolation threshold, ∼70%, the plasmon of the nanostructure transits from red to blue shifts with respect to that of the unshelled Au nanorod. This plasmonic percolation behavior is also confirmed by the scattering measurements on the individual core-shell nanostructures. Quasistatic theory and numerical simulations show that the plasmonic percolation originates from a positive-to-negative transition in the real part of the dielectric function of the shell as the Pd volume fraction is increased. The observed plasmonic percolation is found to be independent of the metal type in the shell. Moreover, compared to the unshelled Au nanorods with similar plasmon wavelengths, the Au nanorod core-Pd shell nanostructures exhibit larger refractive index sensitivities, which is ascribed to the expulsion of the electric field intensity from the Au nanorod core by the adsorbed Pd nanoparticles. © 2012 American Chemical Society.
Active Molecular Plasmonics: Controlling Plasmon Resonances with Molecular SwitchesZheng, Yue Bing; Yang, Ying-Wei; Jensen, Lasse; Fang, Lei; Juluri, Bala Krishna; Flood, Amar H.; Weiss, Paul S.; Stoddart, J. Fraser; Huang, Tony Jun (Nano Letters, American Chemical Society (ACS), 2009-02-11) [Article]A gold nanodisk array, coated with bistable, redox-controllable rotaxane molecules, when exposed to chemical oxidants and reductants, undergoes switching of its plasmonic properties reversibly. By contrast, (i) bare gold nanodisks and (ii) disks coated with a redox-active, but mechanically inert, control compound do not display surface-plasmon-based switching. Along with calculations based on time-dependent density functional theory, these experimental observations suggest that the nanoscale movements within surface-bound “molecular machines” can be used as the active components in plasmonic devices.
Molecular active plasmonics: controlling plasmon resonances with molecular machinesZheng, Yue Bing; Yang, Ying-Wei; Jensen, Lasse; Fang, Lei; Juluri, Bala Krishna; Flood, Amar H.; Weiss, Paul S.; Stoddart, J. Fraser; Huang, Tony Jun (Plasmonics: Nanoimaging, Nanofabrication, and their Applications V, SPIE-Intl Soc Optical Eng, 2009-08-26) [Conference Paper]The paper studies the molecular-level active control of localized surface plasmon resonances (LSPRs) of Au nanodisk arrays with molecular machines. Two types of molecular machines - azobenzene and rotaxane - have been demonstrated to enable the reversible tuning of the LSPRs via the controlled mechanical movements. Azobenzene molecules have the property of trans-cis photoisomerization and enable the photo-induced nematic (N)-isotropic (I) phase transition of the liquid crystals (LCs) that contain the molecules as dopant. The phase transition of the azobenzene-doped LCs causes the refractive-index difference of the LCs, resulting in the reversible peak shift of the LSPRs of the embedded Au nanodisks due to the sensitivity of the LSPRs to the disks' surroundings' refractive index. Au nanodisk array, coated with rotaxanes, switches its LSPRs reversibly when it is exposed to chemical oxidants and reductants alternatively. The correlation between the peak shift of the LSPRs and the chemically driven mechanical movement of rotaxanes is supported by control experiments and a time-dependent density functional theory (TDDFT)-based, microscopic model.