Electrical tuning of a quantum plasmonic resonance.

Surface plasmon (SP) excitations in metals facilitate confinement of light into deep-subwavelength volumes and can induce strong light-matter interaction. Generally, the SP resonances supported by noble metal nanostructures are explained well by classical models, at least until the nanostructure size is decreased to a few nanometres, approaching the Fermi wavelength λF of the electrons. Although there is a long history of reports on quantum size effects in the plasmonic response of nanometre-sized metal particles, systematic experimental studies have been hindered by inhomogeneous broadening in ensemble measurements, as well as imperfect control over size, shape, faceting, surface reconstructions, contamination, charging effects and surface roughness in single-particle measurements. In particular, observation of the quantum size effect in metallic films and its tuning with thickness has been challenging as they only confine carriers in one direction. Here, we show active tuning of quantum size effects in SP resonances supported by a 20-nm-thick metallic film of indium tin oxide (ITO), a plasmonic material serving as a low-carrier-density Drude metal. An ionic liquid (IL) is used to electrically gate and partially deplete the ITO layer. The experiment shows a controllable and reversible blue-shift in the SP resonance above a critical voltage. A quantum-mechanical model including the quantum size effect reproduces the experimental results, whereas a classical model only predicts a red shift.

[1]  W. M. Haynes.  CRC Handbook of Chemistry and Physics , 1990 .

[2]  Junghyun Park,et al.  Electro-optical modulation of a silicon waveguide with an "epsilon-near-zero" material. , 2013, Optics express.

[3]  Hongtao Yuan,et al.  Hydrogenation-induced surface polarity recognition and proton memory behavior at protic-ionic-liquid/oxide electric-double-layer interfaces. , 2010, Journal of the American Chemical Society.

[4]  P. Nordlander,et al.  Theory of Quantum Plasmon Resonances in Doped Semiconductor Nanocrystals , 2014 .

[5]  B. Hsieh,et al.  Work function of indium tin oxide transparent conductor measured by photoelectron spectroscopy , 1996 .

[6]  Arthur F. Hebard,et al.  Electric field gating with ionic liquids , 2007 .

[7]  K. Meiwes-Broer,et al.  Blue shift of the Mie plasma frequency in Ag clusters and particles. , 1993, Physical review. A, Atomic, molecular, and optical physics.

[8]  W. Halperin,et al.  Quantum size effects in metal particles , 1986 .

[9]  Nadine Gottschalk,et al.  Fundamentals Of Photonics , 2016 .

[10]  D. Kolb.  Reconstruction phenomena at metal-electrolyte interfaces , 1996 .

[11]  A. Jauho,et al.  Blueshift of the surface plasmon resonance in silver nanoparticles studied with EELS , 2012, 1210.2535.

[12]  Masashi Kawasaki,et al.  Electrostatic and electrochemical nature of liquid-gated electric-double-layer transistors based on oxide semiconductors. , 2010, Journal of the American Chemical Society.

[13]  Vladimir M. Shalaev,et al.  Searching for better plasmonic materials , 2009, 0911.2737.

[14]  S. Xiao,et al.  Field enhancement at metallic interfaces due to quantum confinement , 2010, 1012.0714.

[15]  Stefan A. Maier,et al.  Quantum Plasmonics , 2016, Proceedings of the IEEE.

[16]  Harry A. Atwater,et al.  Low-Loss Plasmonic Metamaterials , 2011, Science.

[17]  Jon-Paul Maria,et al.  Plasmonic phenomena in indium tin oxide and ITO-Au hybrid films. , 2009, Optics letters.

[18]  Joshua J. Goings,et al.  Theoretical Characterization of Conduction-Band Electrons in Photodoped and Aluminum-Doped Zinc Oxide (AZO) Quantum Dots , 2014 .

[19]  C. McConville,et al.  Nonparabolic coupled Poisson-Schrodinger solutions for quantized electron accumulation layers : Band bending, charge profile, and subbands at InN surfaces , 2008 .

[20]  P. Deymier,et al.  Size-dependent permittivity and intrinsic optical anisotropy of nanometric gold thin films: a density functional theory study. , 2013, Optics express.

[21]  G. Mahler,et al.  Plasmon Excitations in Thin Metal Films. Transition from Three‐Dimensional to Two‐Dimensional Behaviour , 1986 .

[22]  S. Bozhevolnyi,et al.  Optical diamagnetic polarizability of a mesoscopic metallic sphere : transverse self-field approach , 1993 .

[23]  Emil Prodan,et al.  Quantum description of the plasmon resonances of a nanoparticle dimer. , 2009, Nano letters.

[24]  D. M. Wood,et al.  Quantum size effects in the optical properties of small metallic particles , 1982 .

[25]  T. Klar,et al.  Voltage-induced adsorbate damping of single gold nanorod plasmons in aqueous solution. , 2012, Nano letters.

[26]  R. Kötz,et al.  Electron density effects in surface plasmon excitation on silver and gold electrodes , 1977 .

[27]  Hongtao Yuan,et al.  Discovery of superconductivity in KTaO₃ by electrostatic carrier doping. , 2011, Nature nanotechnology.

[28]  Valerio Pruneri,et al.  Mid-infrared plasmonic biosensing with graphene , 2015, Science.

[29]  M. D. Lukin,et al.  Quantum Plasmonic Circuits , 2012, IEEE Journal of Selected Topics in Quantum Electronics.

[30]  J. Maria,et al.  Conductive oxide thin films: Model systems for understanding and controlling surface plasmon resonance , 2009 .

[31]  R. Würschum,et al.  Electrically tunable resistance of a metal. , 2006, Physical review letters.

[32]  J. Dionne,et al.  Quantum plasmon resonances of individual metallic nanoparticles , 2012, Nature.

[33]  Hongxing Xu,et al.  Resonance shifts and spill-out effects in self-consistent hydrodynamic nanoplasmonics , 2014, Nature Communications.

[34]  H. Atwater,et al.  Unity-order index change in transparent conducting oxides at visible frequencies. , 2010, Nano letters (Print).

[35]  Biao Wu,et al.  Effects of quantum tunneling in metal nanogap on surface-enhanced Raman scattering , 2009, 0901.0607.

[36]  Junghyun Park,et al.  Quantification and impact of nonparabolicity of the conduction band of indium tin oxide on its plasmonic properties , 2014 .

[37]  Niket Thakkar,et al.  Charge-tunable quantum plasmons in colloidal semiconductor nanocrystals. , 2014, ACS nano.

[38]  T. Zeng,et al.  First-Principles Study and Model of Dielectric Functions of Silver Nanoparticles , 2010 .

[39]  P. M. Tomchuk,et al.  Optical absorption by small metallic particles , 1997 .

[40]  Junghyun Park,et al.  Electrically Tunable Epsilon-Near-Zero (ENZ) Metafilm Absorbers , 2015, Scientific Reports.

[41]  Paul Mulvaney,et al.  Electrochemical charging of single gold nanorods. , 2009, Journal of the American Chemical Society.

[42]  H. Gleiter,et al.  Nanocrystalline materials: a way to solids with tunable electronic structures and properties? , 2001 .

[43]  Paul Mulvaney,et al.  Drastic Surface Plasmon Mode Shifts in Gold Nanorods Due to Electron Charging , 2006 .

[44]  Jeffrey N. Anker,et al.  Biosensing with plasmonic nanosensors. , 2008, Nature materials.

[45]  R. T. Hill,et al.  Probing the Ultimate Limits of Plasmonic Enhancement , 2012, Science.

[46]  W. Cai,et al.  Plasmonics for extreme light concentration and manipulation. , 2010, Nature materials.

[47]  Paul Mulvaney,et al.  Influence of particle-substrate interaction on localized plasmon resonances. , 2010, Nano letters.

[48]  F. D. Abajo,et al.  Nonlocal Effects in the Plasmons of Strongly Interacting Nanoparticles, Dimers, and Waveguides , 2008, 0802.0040.

[49]  Jeremy J. Baumberg,et al.  Revealing the quantum regime in tunnelling plasmonics , 2012, Nature.

[50]  T. Nishi,et al.  Anomalous electronic structure of ionic liquids determined by soft x-ray emission spectroscopy: contributions from the cations and anions to the occupied electronic structure. , 2008, The Journal of chemical physics.