Plasmonic metamaterial

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A plasmonic metamaterial is a metamaterial that uses surface plasmons to achieve optical properties not seen in nature. Plasmons are produced from the interaction of light with metal-dielectric materials. Under specific conditions, the incident light couples with the surface plasmons to create self-sustaining, propagating electromagnetic waves known as surface plasmon polaritons (SPPs). Once launched, the SPPs ripple along the metal-dielectric interface. Compared with the incident light, the SPPs can be much shorter in wavelength. [1]

Contents

The properties stem from the unique structure of the metal-dielectric composites, with features smaller than the wavelength of light separated by subwavelength distances. Light hitting such a metamaterial is transformed into surface plasmon polaritons, which are shorter in wavelength than the incident light.

Plasmonic materials

Plasmonic materials are metals or metal-like [2] materials that exhibit negative real permittivity. Most common plasmonic materials are gold and silver. However, many other materials show metal-like optical properties in specific wavelength ranges. [3] Various research groups are experimenting with different approaches to make plasmonic materials that exhibit lower losses and tunable optical properties.

Negative index

Plasmonic metamaterials are realizations of materials first proposed by Victor Veselago, a Russian theoretical physicist, in 1967. Also known as left-handed or negative index materials, Veselago theorized that they would exhibit optical properties opposite to those of glass or air. In negative index materials energy is transported in a direction opposite to that of propagating wavefronts, rather than paralleling them, as is the case in positive index materials. [4] [5]

Normally, light traveling from, say, air into water bends upon passing through the normal (a plane perpendicular to the surface) and entering the water. In contrast, light reaching a negative index material through air would not cross the normal. Rather, it would bend the opposite way.

Negative refraction was first reported for microwave and infrared frequencies. A negative refractive index in the optical range was first demonstrated in 2005 by Shalaev et al. (at the telecom wavelength λ = 1.5 μm) [6] and by Brueck et al. (at λ = 2 μm) at nearly the same time. [7] In 2007, a collaboration between the California Institute of Technology, and the NIST reported narrow band, negative refraction of visible light in two dimensions. [4] [5]

To create this response, incident light couples with the undulating, gas-like charges (plasmons) normally on the surface of metals. This photon-plasmon interaction results in SPPs that generate intense, localized optical fields. The waves are confined to the interface between metal and insulator. This narrow channel serves as a transformative guide that, in effect, traps and compresses the wavelength of incoming light to a fraction of its original value. [5]

Nanomechanical systems incorporating metamaterials exhibit negative radiation pressure. [8]

Light falling on conventional materials, with a positive index of refraction, exerts a positive pressure, meaning that it can push an object away from the light source. In contrast, illuminating negative index metamaterials should generate a negative pressure that pulls an object toward light. [8]

Three-dimensional negative index

Computer simulations predict plasmonic metamaterials with a negative index in three dimensions. Potential fabrication methods include multilayer thin film deposition, focused ion beam milling and self-assembly. [8]

Gradient index

PMMs can be made with a gradient index (a material whose refractive index varies progressively across the length or area of the material). One such material involved depositing a thermoplastic, known as a PMMA, on a gold surface via electron beam lithography.

Hyperbolic

Hyperbolic metamaterials behave as a metal when light passes through it in one direction and like a dielectric when light passes in the perpendicular direction, called extreme anisotropy. The material's dispersion relation forms a hyperboloid. The associated wavelength can in principle be infinitely small. [9] Recently, hyperbolic metasurfaces in the visible region has been demonstrated with silver or gold nanostructures by lithographic techniques. [10] [11] The reported hyperbolic devices showed multiple functions for sensing and imaging, e.g., diffraction-free, negative refraction and enhanced plasmon resonance effects, enabled by their unique optical properties. [12] These specific properties are also highly required to fabricate integrated optical meta-circuits for the quantum information applications.

Isotropy

The first metamaterials created exhibit anisotropy in their effects on plasmons. I.e., they act only in one direction.

More recently, researchers used a novel self-folding technique to create a three-dimensional array of split-ring resonators that exhibits isotropy when rotated in any direction up to an incident angle of 40 degrees. Exposing strips of nickel and gold deposited on a polymer/silicon substrate to air allowed mechanical stresses to curl the strips into rings, forming the resonators. By arranging the strips at different angles to each other, 4-fold symmetry was achieved, which allowed the resonators to produce effects in multiple directions. [13] [14]

Materials

Silicon sandwich

Negative refraction for visible light was first produced in a sandwich-like construction with thin layers. An insulating sheet of silicon nitride was covered by a film of silver and underlain by another of gold. The critical dimension is the thickness of the layers, which summed to a fraction of the wavelength of blue and green light. By incorporating this metamaterial into integrated optics on an IC chip, negative refraction was demonstrated over blue and green frequencies. The collective result is a relatively significant response to light. [4] [5]

Graphene

Graphene also accommodates surface plasmons, [15] observed via near field infrared optical microscopy techniques [16] [17] and infrared spectroscopy. [18] Potential applications of graphene plasmonics involve terahertz to midinfrared frequencies, in devices such as optical modulators, photodetectors and biosensors. [19]

Superlattice

A hyperbolic metamaterial made from titanium nitride (metal) and aluminum scandium nitride (dielectric) have compatible crystal structures and can form a superlattice, a crystal that combines two (or more) materials. The material is compatible with existing CMOS technology (unlike traditional gold and silver), mechanically strong and thermally stable at higher temperatures. The material exhibits higher photonic densities of states than Au or Ag. [20] The material is an efficient light absorber. [21]

The material was created using epitaxy inside a vacuum chamber with a technique known as magnetron sputtering. The material featured ultra-thin and ultra-smooth layers with sharp interfaces. [21]

Possible applications include a "planar hyperlens" that could make optical microscopes able to see objects as small as DNA, advanced sensors, more efficient solar collectors, nano-resonators, quantum computing and diffraction free focusing and imaging. [21]

The material works across a broad spectrum from near-infrared to visible light. Near-infrared is essential for telecommunications and optical communications, and visible light is important for sensors, microscopes and efficient solid-state light sources. [21]

Applications

Microscopy

One potential application is microscopy beyond the diffraction limit. [4] Gradient index plasmonics were used to produce Luneburg and Eaton lenses that interact with surface plasmon polaritons rather than photons.

A theorized superlens could exceed the diffraction limit that prevents standard (positive-index) lenses from resolving objects smaller than one-half of the wavelength of visible light. Such a superlens would capture spatial information that is beyond the view of conventional optical microscopes. Several approaches to building such a microscope have been proposed. The subwavelength domain could be optical switches, modulators, photodetectors and directional light emitters. [22]

Biological and chemical sensing

Other proof-of-concept applications under review involve high sensitivity biological and chemical sensing. They may enable the development of optical sensors that exploit the confinement of surface plasmons within a certain type of Fabry-Perot nano-resonator. This tailored confinement allows efficient detection of specific bindings of target chemical or biological analytes using the spatial overlap between the optical resonator mode and the analyte ligands bound to the resonator cavity sidewalls. Structures are optimized using finite difference time domain electromagnetic simulations, fabricated using a combination of electron beam lithography and electroplating, and tested using both near-field and far-field optical microscopy and spectroscopy. [4]

Optical computing

Optical computing replaces electronic signals with light processing devices. [23]

In 2014 researchers announced a 200 nanometer, terahertz speed optical switch. The switch is made of a metamaterial consisting of nanoscale particles of vanadium dioxide (VO
2), a crystal that switches between an opaque, metallic phase and a transparent, semiconducting phase. The nanoparticles are deposited on a glass substrate and overlain by even smaller gold nanoparticles [24] that act as a plasmonic photocathode. [25]

Femtosecond laser pulses free electrons in the gold particles that jump into the VO
2 and cause a subpicosecond phase change. [24]

The device is compatible with current integrated circuit technology, silicon-based chips and high-K dielectrics materials. It operates in the visible and near-infrared region of the spectrum. It generates only 100 femtojoules/bit/operation, allowing the switches to be packed tightly. [24]

Photovoltaics

Gold group metals (Au, Ag and Cu) have been used as direct active materials in photovoltaics and solar cells. The materials act simultaneously as electron [26] and hole donor, [27] and thus can be sandwiched between electron and hole transport layers to make a photovoltaic cell. At present these photovoltaic cells allow powering smart sensors for the Internet of Things (IoT) platform. [28]

See also

Related Research Articles

<span class="mw-page-title-main">Plasmon</span> Quasiparticle of charge oscillations in condensed matter

In physics, a plasmon is a quantum of plasma oscillation. Just as light consists of photons, the plasma oscillation consists of plasmons. The plasmon can be considered as a quasiparticle since it arises from the quantization of plasma oscillations, just like phonons are quantizations of mechanical vibrations. Thus, plasmons are collective oscillations of the free electron gas density. For example, at optical frequencies, plasmons can couple with a photon to create another quasiparticle called a plasmon polariton.

<span class="mw-page-title-main">Metamaterial</span> Materials engineered to have properties that have not yet been found in nature

A metamaterial is any material engineered to have a property that is rarely observed in naturally occurring materials. They are made from assemblies of multiple elements fashioned from composite materials such as metals and plastics. These materials are usually arranged in repeating patterns, at scales that are smaller than the wavelengths of the phenomena they influence. Metamaterials derive their properties not from the properties of the base materials, but from their newly designed structures. Their precise shape, geometry, size, orientation and arrangement gives them their smart properties capable of manipulating electromagnetic waves: by blocking, absorbing, enhancing, or bending waves, to achieve benefits that go beyond what is possible with conventional materials.

<span class="mw-page-title-main">Surface plasmon resonance</span> Physical phenomenon of electron resonance

Surface plasmon resonance (SPR) is a phenomenon that occurs where electrons in a thin metal sheet become excited by light that is directed to the sheet with a particular angle of incidence, and then travel parallel to the sheet. Assuming a constant light source wavelength and that the metal sheet is thin, the angle of incidence that triggers SPR is related to the refractive index of the material and even a small change in the refractive index will cause SPR to not be observed. This makes SPR a possible technique for detecting particular substances (analytes) and SPR biosensors have been developed to detect various important biomarkers.

A superlens, or super lens, is a lens which uses metamaterials to go beyond the diffraction limit. The diffraction limit is a feature of conventional lenses and microscopes that limits the fineness of their resolution depending on the illumination wavelength and the numerical aperture NA of the objective lens. Many lens designs have been proposed that go beyond the diffraction limit in some way, but constraints and obstacles face each of them.

<span class="mw-page-title-main">Split-ring resonator</span> A resonator

A split-ring resonator (SRR) is an artificially produced structure common to metamaterials. Its purpose is to produce the desired magnetic susceptibility in various types of metamaterials up to 200 terahertz.

<span class="mw-page-title-main">Negative-index metamaterial</span> Material with a negative refractive index

Negative-index metamaterial or negative-index material (NIM) is a metamaterial whose refractive index for an electromagnetic wave has a negative value over some frequency range.

<span class="mw-page-title-main">Terahertz metamaterial</span>

A terahertz metamaterial is a class of composite metamaterials designed to interact at terahertz (THz) frequencies. The terahertz frequency range used in materials research is usually defined as 0.1 to 10 THz.

<span class="mw-page-title-main">Tunable metamaterial</span>

A tunable metamaterial is a metamaterial with a variable response to an incident electromagnetic wave. This includes remotely controlling how an incident electromagnetic wave interacts with a metamaterial. This translates into the capability to determine whether the EM wave is transmitted, reflected, or absorbed. In general, the lattice structure of the tunable metamaterial is adjustable in real time, making it possible to reconfigure a metamaterial device during operation. It encompasses developments beyond the bandwidth limitations in left-handed materials by constructing various types of metamaterials. The ongoing research in this domain includes electromagnetic materials that are very meta which mean good and has a band gap metamaterials (EBG), also known as photonic band gap (PBG), and negative refractive index material (NIM).

<span class="mw-page-title-main">Photonic metamaterial</span> Type of electromagnetic metamaterial

A photonic metamaterial (PM), also known as an optical metamaterial, is a type of electromagnetic metamaterial, that interacts with light, covering terahertz (THz), infrared (IR) or visible wavelengths. The materials employ a periodic, cellular structure.

A nonlinear metamaterial is an artificially constructed material that can exhibit properties not yet found in nature. Its response to electromagnetic radiation can be characterized by its permittivity and material permeability. The product of the permittivity and permeability results in the refractive index. Unlike natural materials, nonlinear metamaterials can produce a negative refractive index. These can also produce a more pronounced nonlinear response than naturally occurring materials.

A metamaterial absorber is a type of metamaterial intended to efficiently absorb electromagnetic radiation such as light. Furthermore, metamaterials are an advance in materials science. Hence, those metamaterials that are designed to be absorbers offer benefits over conventional absorbers such as further miniaturization, wider adaptability, and increased effectiveness. Intended applications for the metamaterial absorber include emitters, photodetectors, sensors, spatial light modulators, infrared camouflage, wireless communication, and use in solar photovoltaics and thermophotovoltaics.

A flat lens is a lens whose flat shape allows it to provide distortion-free imaging, potentially with arbitrarily-large apertures. The term is also used to refer to other lenses that provide a negative index of refraction. Flat lenses require a refractive index close to −1 over a broad angular range. In recent years, flat lenses based on metasurfaces were also demonstrated.

<span class="mw-page-title-main">Surface plasmon polariton</span> Electromagnetic waves that travel along an interface

Surface plasmon polaritons (SPPs) are electromagnetic waves that travel along a metal–dielectric or metal–air interface, practically in the infrared or visible-frequency. The term "surface plasmon polariton" explains that the wave involves both charge motion in the metal and electromagnetic waves in the air or dielectric ("polariton").

<span class="mw-page-title-main">Localized surface plasmon</span>

A localized surface plasmon (LSP) is the result of the confinement of a surface plasmon in a nanoparticle of size comparable to or smaller than the wavelength of light used to excite the plasmon. When a small spherical metallic nanoparticle is irradiated by light, the oscillating electric field causes the conduction electrons to oscillate coherently. When the electron cloud is displaced relative to its original position, a restoring force arises from Coulombic attraction between electrons and nuclei. This force causes the electron cloud to oscillate. The oscillation frequency is determined by the density of electrons, the effective electron mass, and the size and shape of the charge distribution. The LSP has two important effects: electric fields near the particle's surface are greatly enhanced and the particle's optical absorption has a maximum at the plasmon resonant frequency. Surface plasmon resonance can also be tuned based on the shape of the nanoparticle. The plasmon frequency can be related to the metal dielectric constant. The enhancement falls off quickly with distance from the surface and, for noble metal nanoparticles, the resonance occurs at visible wavelengths. Localized surface plasmon resonance creates brilliant colors in metal colloidal solutions.

<span class="mw-page-title-main">Hybrid plasmonic waveguide</span>

A hybrid plasmonic waveguide is an optical waveguide that achieves strong light confinement by coupling the light guided by a dielectric waveguide and a plasmonic waveguide. It is formed by separating a medium of high refractive index from a metal surface by a small gap.

<span class="mw-page-title-main">Plasmonics</span>

Plasmonics or nanoplasmonics refers to the generation, detection, and manipulation of signals at optical frequencies along metal-dielectric interfaces in the nanometer scale. Inspired by photonics, plasmonics follows the trend of miniaturizing optical devices, and finds applications in sensing, microscopy, optical communications, and bio-photonics.

<span class="mw-page-title-main">Electromagnetic metasurface</span>

An electromagnetic metasurface refers to a kind of artificial sheet material with sub-wavelength thickness. Metasurfaces can be either structured or unstructured with subwavelength-scaled patterns in the horizontal dimensions.

Graphene is a 2D nanosheet with atomic thin thickness in terms of 0.34 nm. Due to the ultrathin thickness, graphene showed many properties that are quite different from their bulk graphite counterparts. The most prominent advantages are known to be their high electron mobility and high mechanical strengths. Thus, it exhibits potential for applications in optics and electronics especially for the development of wearable devices as flexible substrates. More importantly, the optical absorption rate of graphene is 2.3% in the visible and near-infrared region. This broadband absorption characteristic also attracted great attention of the research community to exploit the graphene-based photodetectors/modulators.

<span class="mw-page-title-main">Ravindra Kumar Sinha (physicist)</span> Indian physicist and administrator

Prof. Ravindra Kumar Sinha is the Vice Chancellor of Gautam Buddha University, Greater Noida, Gautam Budh Nagar Under UP Government. He was the director of the CSIR-Central Scientific Instruments Organisation (CSIR-CSIO) Sector-30C, Chandigarh-160 030, India. He has been a Professor - Applied Physics, Dean-Academic [UG] & Chief Coordinator: TIFAC-Center of Relevance and Excellence in Fiber Optics and Optical Communication, Mission REACH Program, Technology Vision-2020, Govt. of India Delhi Technological University Bawana Road, Delhi-110042, India.

Spoof surface plasmons, also known as spoof surface plasmon polaritons and designer surface plasmons, are surface electromagnetic waves in microwave and terahertz regimes that propagate along planar interfaces with sign-changing permittivities. Spoof surface plasmons are a type of surface plasmon polariton, which ordinarily propagate along metal and dielectric interfaces in infrared and visible frequencies. Since surface plasmon polaritons cannot exist naturally in microwave and terahertz frequencies due to dispersion properties of metals, spoof surface plasmons necessitate the use of artificially-engineered metamaterials.

References

  1. ↑ Kuttge, M.; Vesseur, E.; Koenderink, A.; Lezec, H.; Atwater, H.; García De Abajo, F.; Polman, A. (2009). "Local density of states, spectrum, and far-field interference of surface plasmon polaritons probed by cathodoluminescence" (PDF). Physical Review B. 79 (11): 113405. Bibcode:2009PhRvB..79k3405K. doi:10.1103/PhysRevB.79.113405. hdl: 10261/54073 .
  2. ↑ West, P. R.; Ishii, S.; Naik, G. V.; Emani, N. K.; Shalaev, V. M.; Boltasseva, A. (2010). "Searching for better plasmonic materials". Laser & Photonics Reviews. 4 (6): 795–808. arXiv: 0911.2737 . Bibcode:2010LPRv....4..795W. doi:10.1002/lpor.200900055. S2CID   16887413.
  3. ↑ Boltasseva, A.; Atwater, H. A. (2011). "Low-Loss Plasmonic Metamaterials". Science. 331 (6015): 290–291. Bibcode:2011Sci...331..290B. doi:10.1126/science.1198258. PMID   21252335. S2CID   206530073.
  4. 1 2 3 4 5 NIST researchers, Nanofabrication Research Group (2009-08-20). "Three-Dimensional Plasmonic Metamaterials". National Institute of Science and Technology. Retrieved 2011-02-14.
  5. 1 2 3 4 Lezec, H. J.; Dionne, J. A.; Atwater, H. A. (2007). "Negative Refraction at Visible Frequencies" (PDF). Science. 316 (5823): 430–2. Bibcode:2007Sci...316..430L. CiteSeerX   10.1.1.422.9475 . doi:10.1126/science.1139266. PMID   17379773. S2CID   35189301.
  6. ↑ Shalaev, V. M.; Cai, W.; Chettiar, U. K.; Yuan, H.-K.; Sarychev, A. K.; Drachev, V. P.; Kildishev, A. V. (2005). "Negative index of refraction in optical metamaterials" (PDF). Optics Letters . 30 (24): 3356–8. arXiv: physics/0504091 . Bibcode:2005OptL...30.3356S. doi:10.1364/OL.30.003356. PMID   16389830. S2CID   14917741.
  7. ↑ Zhang, Shuang; Fan, Wenjun; Panoiu, N. C.; Malloy, K. J.; Osgood, R. M.; Brueck, S. R. J. (2005). "Experimental Demonstration of Near-Infrared Negative-Index Metamaterials" (PDF). Phys. Rev. Lett. 95 (13): 137404. arXiv: physics/0504208 . Bibcode:2005PhRvL..95m7404Z. doi:10.1103/PhysRevLett.95.137404. PMID   16197179. S2CID   15246675.
  8. 1 2 3 Lezec, Henri J.; Chau, Kenneth J. "Negative Radiation Pressure" (PDF). Retrieved 2011-02-14.{{cite journal}}: Cite journal requires |journal= (help)
  9. ↑ Hyperbolic metamaterials explained in 5 minutes on YouTube
  10. ↑ High, A.; et al. (2015). "Visible-frequency hyperbolic metasurface". Nature. 522 (7555): 192–196. Bibcode:2015Natur.522..192H. doi:10.1038/nature14477. PMID   26062510. S2CID   205243865.
  11. ↑ Jiang, L.; et al. (2017). "Multifunctional hyperbolic nanogroove metasurface for submolecular detection". Small. 13 (30): 1700600. doi:10.1002/smll.201700600. PMID   28597602.
  12. ↑ Takayama, O.; Lavrinenko, A. V. (2019). "Optics with hyperbolic materials" (PDF). Journal of the Optical Society of America B. 36 (8): F38–F48. doi:10.1364/JOSAB.36.000F38. S2CID   149698994.
  13. ↑ "How to create metamaterials that work in all directions | KurzweilAI". www.kurzweilai.net.
  14. ↑ Chen, Che-Chin; Ishikawa, Atsushi; Tang, Yu-Hsiang; Shiao, Ming-Hua; Tsai, Din Ping; Tanaka, Takuo (January 2015). "Uniaxial-isotropic Metamaterials by Three-Dimensional Split-Ring Resonators". Advanced Optical Materials. 3 (1): 44–48. doi:10.1002/adom.201400316. S2CID   94970778.
  15. ↑ Zeng, S.; et al. (2015). "Graphene-gold metasurface architectures for ultrasensitive plasmonic biosensing". Advanced Materials. 27 (40): 1–7. Bibcode:2015AdM....27.6163Z. doi:10.1002/adma.201501754. hdl: 10220/38683 . PMID   26349431. S2CID   205261271.
  16. ↑ Chen, J; Badioli, M; Alonso-González, P; Thongrattanasiri, S; Huth, F; Osmond, J; Spasenović, M; Centeno, A; Pesquera, A; Godignon, P; Elorza, AZ; Camara, N; García; de Abajo, FJ; Hillenbrand, R; Koppens, FH (2012). "Optical nano-imaging of gate-tunable graphene plasmons". Nature. 487 (7405): 77–81. arXiv: 1202.4996 . Bibcode:2012Natur.487...77C. doi:10.1038/nature11254. PMID   22722861. S2CID   4431470.
  17. ↑ Fei, Z.; Rodin, A. S.; Andreev, G. O.; Bao, W.; McLeod, A. S.; Wagner, M.; Zhang, L. M.; Zhao, Z.; Thiemens, M.; Dominguez, G.; Fogler, M. M.; Castro Neto, A. H.; Lau, C. N.; Keilmann, F.; Basov, D. N. (5 July 2012). "Gate-tuning of graphene plasmons revealed by infrared nano-imaging". Nature. 487 (7405): 82–5. arXiv: 1202.4993 . Bibcode:2012Natur.487...82F. doi:10.1038/nature11253. PMID   22722866. S2CID   4348703.
  18. ↑ Yan, Hugen; Low, Tony; Zhu, Wenjuan; Wu, Yanqing; Freitag, Marcus; Li, Xuesong; Guinea, Francisco; Avouris, Phaedon; Xia, Fengnian (2013). "Damping pathways of mid-infrared plasmons in graphene nanostructures". Nature Photonics. 7 (5): 394–399. arXiv: 1209.1984 . Bibcode:2013NaPho...7..394Y. doi:10.1038/nphoton.2013.57. S2CID   119225015.
  19. ↑ Low, T.; Avouris, P. (2014). "Graphene Plasmonics for Terahertz to Mid-Infrared Applications". ACS Nano. 8 (2): 1086–101. arXiv: 1403.2799 . Bibcode:2014arXiv1403.2799L. doi:10.1021/nn406627u. PMID   24484181. S2CID   8151572.
  20. ↑ Gururaj V. Naik; et al. (2014). "Epitaxial superlattices with titanium nitride as a plasmonic component for optical hyperbolic metamaterials". Proceedings of the National Academy of Sciences. 111 (21): 7546–7551. Bibcode:2014PNAS..111.7546N. doi: 10.1073/pnas.1319446111 . PMC   4040552 . PMID   24821762.
  21. 1 2 3 4 "'Hyperbolic metamaterials' closer to reality". KurzweilAI. May 15, 2014.
  22. ↑ Pacifici, Domenico; Lezec, Henri J.; Sweatlock, Luke A.; Walters, Robert J.; Atwater, Harry A. (2008). "Universal optical transmission features in periodic and quasiperiodic hole arrays" (PDF). Optics Express. 16 (12): 9222–38. Bibcode:2008OExpr..16.9222P. doi: 10.1364/OE.16.009222 . PMID   18545635.
  23. ↑ Yarris, Lynn (2009-08-20). "GRIN Plasmonics…" (Online news release). U.S. Department of Energy National Laboratory Operated by the University of California. Retrieved 2011-02-15.
  24. 1 2 3 "Nanoscale optical switch breaks miniaturization barrier". KurzweilAI. March 18, 2014. Retrieved 19 April 2015.
  25. ↑ Kannatassen Appavoo; et al. (2014). "Ultrafast Phase Transition via Catastrophic Phonon Collapse Driven by Plasmonic Hot-Electron Injection". Nano Letters. 14 (3): 1127–1133. Bibcode:2014NanoL..14.1127A. doi:10.1021/nl4044828. PMID   24484272.
  26. ↑ Sá, Jacinto; et al. (2013). "Direct observation of charge separation on Au localized surface plasmons". Energy & Environmental Science. 6 (12): 3584–3588. doi:10.1039/c3ee42731e.
  27. ↑ Tagliabue, Giulia (2020). "Ultrafast hot-hole injection modifies hot-electron dynamics in Au/P-GaN heterostructures". Nature Materials. 19 (12): 1312–1318. arXiv: 1810.04238 . Bibcode:2020NatMa..19.1312T. doi:10.1038/s41563-020-0737-1. PMID   32719510. S2CID   53121725.
  28. ↑ "Peafowl Solar Power | MAKING ENERGY BEAUTIFUL".

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