Imperial College London

ProfessorStefanMaier

Faculty of Natural SciencesDepartment of Physics

Lee-Lucas Chair in Experimental Physics
 
 
 
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Contact

 

+44 (0)20 7594 6063s.maier Website CV

 
 
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Location

 

Huxley 903Huxley BuildingSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
to

786 results found

He C, Tang Z, Liu L, Maier SA, Wang X, Ren H, Pan Aet al., 2024, Nonlinear Boost of Optical Angular Momentum Selectivity by Hybrid Nanolaser Circuits., Nano Lett, Vol: 24, Pages: 1784-1791

Selective control of light is essential for optical science and technology, with numerous applications. However, optical selectivity in the angular momentum of light has been quite limited, remaining constant by increasing the incident light power on previous passive optical devices. Here, we demonstrate a nonlinear boost of optical selectivity in both the spin and orbital angular momentum of light through near-field selective excitation of single-mode nanolasers. Our designed hybrid nanolaser circuits consist of plasmonic metasurfaces and individually placed perovskite nanowires, enabling subwavelength focusing of angular-momentum-distinctive plasmonic fields and further selective excitation of nanolasers in nanowires. The optically selected nanolaser with a nonlinear increase of light emission greatly enhances the baseline optical selectivity offered by the metasurface from about 0.4 up to near unity. Our demonstrated hybrid nanophotonic platform may find important applications in all-optical logic gates and nanowire networks, ultrafast optical switches, nanophotonic detectors, and on-chip optical and quantum information processing.

Journal article

Li C, Wieduwilt T, Wendisch FJ, Márquez A, Menezes LDS, Maier SA, Schmidt MA, Ren Het al., 2024, Author Correction: Metafiber transforming arbitrarily structured light., Nat Commun, Vol: 15

Journal article

Lee S, Fan C, Movsesyan A, Bürger J, Wendisch FJ, de S Menezes L, Maier SA, Ren H, Liedl T, Besteiro LV, Govorov AO, Cortés Eet al., 2024, Unraveling the Chirality Transfer from Circularly Polarized Light to Single Plasmonic Nanoparticles., Angew Chem Int Ed Engl

Due to their broken symmetry, chiral plasmonic nanostructures have unique optical properties and numerous applications. However, there is still a lack of comprehension regarding how chirality transfer occurs between circularly polarized light (CPL) and these structures. Here, we thoroughly investigate the plasmon-assisted growth of chiral nanoparticles from achiral Au nanocubes (AuNCs) via CPL without the involvement of any chiral molecule stimulators. We identify the structural chirality of our synthesized chiral plasmonic nanostructures using circular differential scattering (CDS) spectroscopy, which is correlated with scanning electron microscopy imaging at both the single-particle and ensemble levels. Theoretical simulations, including hot-electron surface maps, reveal that the plasmon-induced chirality transfer is mediated by the asymmetric distribution of hot electrons on achiral AuNCs under CPL excitation. Furthermore, we shed light on how this plasmon-induced chirality transfer can also be utilized for chiral growth in bimetallic systems, such as Ag or Pd on AuNCs. The results presented here uncover fundamental aspects of chiral light-matter interaction and have implications for the future design and optimization of chiral sensors and chiral catalysis, among others.

Journal article

Ezendam S, Gargiulo J, Sousa-Castillo A, Lee JB, Nam YS, Maier SA, Cortés Eet al., 2024, Spatial Distributions of Single-Molecule Reactivity in Plasmonic Catalysis., ACS Nano, Vol: 18, Pages: 451-460

Plasmonic catalysts have the potential to accelerate and control chemical reactions with light by exploiting localized surface plasmon resonances. However, the mechanisms governing plasmonic catalysis are not simple to decouple. Several plasmon-derived phenomena, such as electromagnetic field enhancements, temperature, or the generation of charge carriers, can affect the reactivity of the system. These effects are convoluted with the inherent (nonplasmonic) catalytic properties of the metal surface. Disentangling these coexisting effects is challenging but is the key to rationally controlling reaction pathways and enhancing reaction rates. This study utilizes super-resolution fluorescence microscopy to examine the mechanisms of plasmonic catalysis at the single-particle level. The reduction reaction of resazurin to resorufin in the presence of Au nanorods coated with a porous silica shell is investigated in situ. This allows the determination of reaction rates with a single-molecule sensitivity and subparticle resolution. By variation of the irradiation wavelength, it is possible to examine two different regimes: photoexcitation of the reactant molecules and photoexcitation of the nanoparticle's plasmon resonance. In addition, the measured spatial distribution of reactivity allows differentiation between superficial and far-field effects. Our results indicate that the reduction of resazurin can occur through more than one reaction pathway, being most efficient when the reactant is photoexcited and is in contact with the Au surface. In addition, it was found that the spatial distribution of enhancements varies, depending on the underlying mechanism. These findings contribute to the fundamental understanding of plasmonic catalysis and the rational design of future plasmonic nanocatalysts.

Journal article

Córdova-Castro RM, van Dam B, Lauri A, Maier SA, Sapienza R, De Wilde Y, Izeddin I, Krachmalnicoff Vet al., 2024, Single-emitter super-resolved imaging of radiative decay rate enhancement in dielectric gap nanoantennas, Light: Science & Applications, Vol: 13, ISSN: 2095-5545

High refractive index dielectric nanoantennas strongly modify the decay rate via the Purcell effect through the design of radiative channels. Due to their dielectric nature, the field is mainly confined inside the nanostructure and in the gap, which is hard to probe with scanning probe techniques. Here we use single-molecule fluorescence lifetime imaging microscopy (smFLIM) to map the decay rate enhancement in dielectric GaP nanoantenna dimers with a median localization precision of 14 nm. We measure, in the gap of the nanoantenna, decay rates that are almost 30 times larger than on a glass substrate. By comparing experimental results with numerical simulations we show that this large enhancement is essentially radiative, contrary to the case of plasmonic nanoantennas, and therefore has great potential for applications such as quantum optics and biosensing.

Journal article

Lu W, Menezes LDS, Tittl A, Ren H, Maier SAet al., 2024, Active Huygens' metasurface based on in-situ grown conductive polymer, Pages: 39-49

Active metasurfaces provide unique advantages for on-demand light manipulation at a subwavelength scale for emerging visual applications of displays, holographic projectors, optical sensors, light detection and ranging (LiDAR). These applications put stringent requirements on switching speed, cycling duration, electro-optical controllability, modulation contrast, optical efficiency and operation voltages. However, previous demonstrations focus only on particular subsets of these key performance requirements for device implementation, while the other performance metrics have remained too low for any practical use. Here, we demonstrate an active Huygens' metasurface based on conductive polyaniline (PANI), which can be in-situ grown and optimized on the metasurface. We have achieved simultaneously on the active metasurface switching speed of 60 frame per second (fps), switching duration of more than 2000 switching cycles without noticeable degradation, hysteresis-free controllability over intermediate states, modulation contrast of over 1400 %, optical efficiency of 28 % and operation voltage range within 1 V. Such PANI-powered active metasurface design can be readily incorporated into other metasurface concepts to deliver high-reliability electrical control over its optical response, paving the way for compact and robust electro-optic metadevices.

Conference paper

Yu H, Xie Z, Li C, Li C, de S Menezes L, Maier SA, Ren Het al., 2023, Dispersion engineering of metalenses, Applied Physics Letters, Vol: 123, ISSN: 0003-6951

Optical dispersion, the variation of the speed of light with frequency in a material, presents significant challenges in modern optical systems, including chromatic aberration and pulse signal distortion. Traditional approaches to dispersion engineering of an optical lens system require the use of a set of sub-lenses of opposite dispersion properties, largely increasing the overall lens thickness. Ultrathin metasurfaces offer unprecedented control over optical wavefronts with advanced functionalities. Developing achromatic metalenses has thereby emerged as a timely research topic for metasurface research. This Perspective article provides a comprehensive overview of dispersion engineering methods in metalenses, including the use of 2D and 3D meta-atoms fabricated from planar lithography and 3D laser lithography methods, respectively. We compare key figures of merit of achromatic metalenses developed for different wavelength ranges and discuss recent inverse design of large-scale achromatic metalenses. We believe advanced machine learning methods as well as hybrid nanofabrication of diffractive metalenses, refractive lenses, and metamaterials-like spaceplates could offer promising avenues for overcoming current challenges and eventually push ultrathin achromatic optics to practical applications in optics-related fields.

Journal article

Li C, Jang J, Badloe T, Yang T, Kim J, Kim J, Nguyen M, Maier SA, Rho J, Ren H, Aharonovich Iet al., 2023, Arbitrarily structured quantum emission with a multifunctional metalens, eLight, Vol: 3, ISSN: 2097-1710

Structuring light emission from single-photon emitters (SPEs) in multiple degrees of freedom is of great importance for quantum information processing towards higher dimensions. However, traditional control of emission from quantum light sources relies on the use of multiple bulky optical elements or nanostructured resonators with limited functionalities, constraining the potential of multi-dimensional tailoring. Here we introduce the use of an ultrathin polarisation-beam-splitting metalens for the arbitrary structuring of quantum emission at room temperature. Owing to the complete and independent polarisation and phase control at the single meta-atom level, the designed metalens enables simultaneous mapping of quantum emission from ultra-bright defects in hexagonal boron nitride and imprinting of an arbitrary wavefront onto orthogonal polarisation states of the sources. The hybrid quantum metalens enables simultaneous manipulation of multiple degrees of freedom of a quantum light source, including directionality, polarisation, and orbital angular momentum. This could unleash the full potential of solid-state SPEs for their use as high-dimensional quantum sources for advanced quantum photonic applications.

Journal article

Márquez A, Li C, Beléndez A, Maier SA, Ren Het al., 2023, Information multiplexing from optical holography to multi-channel metaholography, Nanophotonics, Vol: 12, Pages: 4415-4440

Holography offers a vital platform for optical information storage and processing, which has a profound impact on many photonic applications, including 3D displays, LiDAR, optical encryption, and artificial intelligence. In this review, we provide a comprehensive overview of optical holography, moving from volume holography based on optically thick holograms to digital holography using ultrathin metasurface holograms in nanophotonics. We review the use of volume holograms for holographic multiplexing through the linear momentum selectivity and other approaches and highlight the emerging use of digital holograms that can be implemented by ultrathin metasurfaces. We will summarize the fabrication of different holographic recording media and digital holograms based on recent advances in flat meta-optics and nanotechnology. We highlight the rapidly developing field of metasurface holography, presenting the use of multi-functional metasurfaces for multiplexing holography in the use of polarization, wavelength, and incident angle of light. In the scope of holographic applications, we will focus on high bandwidth metasurface holograms that offer the strong sensitivity to the orbital angular momentum of light. At the end, we will provide a short summary of this review article and our perspectives on the future development of the vivid holography field.

Journal article

Boggiano HD, Ramallo JI, Nan L, Litwiller A, Cortés E, Maier SA, Grinblat G, Fuertes MC, Angelomé PC, Bragas AVet al., 2023, Optical Readout of the Mechanical Properties of Silica Mesoporous Thin Films Using Plasmonic Nanoantennas, ACS Photonics, Vol: 10, Pages: 3998-4005

In this work, we apply the recently developed frequency shift of nanoantennas (FRESA) technique to measure the Young’s modulus of thin mesoporous films at GHz frequencies as a function of porosity with local precision. The method measures changes in the mechanical oscillation frequency of optically excited plasmonic nanoantennas with modification of their surrounding medium. The values obtained range from 4 to 10 GPa for porosities extending from 35 to 4%, compatible with reports on films grown under similar conditions. We further find comparable results when using the well-established nanoindentation (NI) technique, validating the new method. By analysis of the nanoresonator’s quality factor, the measurement reveals an excellent interfacial adhesion of the films to the nanoantennas. Different from most other characterization techniques, FRESA provides elastic modulus determination at GHz frequencies, relevant for the operation of current devices. Furthermore, FRESA exhibits, in principle, no limitations in terms of film thickness, in contrast to the NI, which is strongly affected by the stiffness of the substrate for ultrathin films.

Journal article

Li C, Wieduwilt T, Wendisch FJ, Márquez A, Menezes LDS, Maier SA, Schmidt MA, Ren Het al., 2023, Metafiber transforming arbitrarily structured light., Nat Commun, Vol: 14

Structured light has proven useful for numerous photonic applications. However, the current use of structured light in optical fiber science and technology is severely limited by mode mixing or by the lack of optical elements that can be integrated onto fiber end-faces for wavefront engineering, and hence generation of structured light is still handled outside the fiber via bulky optics in free space. We report a metafiber platform capable of creating arbitrarily structured light on the hybrid-order Poincaré sphere. Polymeric metasurfaces, with unleashed height degree of freedom and a greatly expanded 3D meta-atom library, were 3D laser nanoprinted and interfaced with polarization-maintaining single-mode fibers. Multiple metasurfaces were interfaced on the fiber end-faces, transforming the fiber output into different structured-light fields, including cylindrical vector beams, circularly polarized vortex beams, and arbitrary vector field. Our work provides a paradigm for advancing optical fiber science and technology towards fiber-integrated light shaping, which may find important applications in fiber communications, fiber lasers and sensors, endoscopic imaging, fiber lithography, and lab-on-fiber technology.

Journal article

Ben-Jaber S, Glass D, Brick T, Maier SA, Parkin IP, Cortes E, Peveler WJ, Quesada-Cabrera Ret al., 2023, Photo-induced enhanced Raman spectroscopy as a probe for photocatalytic surfaces, PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES, Vol: 381, ISSN: 1364-503X

Journal article

Kühner L, Wendisch FJ, Antonov AA, Bürger J, Hüttenhofer L, de S Menezes L, Maier SA, Gorkunov MV, Kivshar Y, Tittl Aet al., 2023, Unlocking the out-of-plane dimension for photonic bound states in the continuum to achieve maximum optical chirality., Light Sci Appl, Vol: 12

The realization of lossless metasurfaces with true chirality crucially requires the fabrication of three-dimensional structures, constraining experimental feasibility and hampering practical implementations. Even though the three-dimensional assembly of metallic nanostructures has been demonstrated previously, the resulting plasmonic resonances suffer from high intrinsic and radiative losses. The concept of photonic bound states in the continuum (BICs) is instrumental for tailoring radiative losses in diverse geometries, especially when implemented using lossless dielectrics, but applications have so far been limited to planar structures. Here, we introduce a novel nanofabrication approach to unlock the height of individual resonators within all-dielectric metasurfaces as an accessible parameter for the efficient control of resonance features and nanophotonic functionalities. In particular, we realize out-of-plane symmetry breaking in quasi-BIC metasurfaces and leverage this design degree of freedom to demonstrate an optical all-dielectric quasi-BIC metasurface with maximum intrinsic chirality that responds selectively to light of a particular circular polarization depending on the structural handedness. Our experimental results not only open a new paradigm for all-dielectric BICs and chiral nanophotonics, but also promise advances in the realization of efficient generation of optical angular momentum, holographic metasurfaces, and parity-time symmetry-broken optical systems.

Journal article

Katzmarek DA, Mancini A, Maier SA, Iacopi Fet al., 2023, Direct synthesis of nanopatterned epitaxial graphene on silicon carbide, NANOTECHNOLOGY, Vol: 34, ISSN: 0957-4484

Journal article

Gryb D, Wendisch FJ, Aigner A, Goelz T, Tittl A, Menezes LDS, Maier SAet al., 2023, Two-Dimensional Chiral Metasurfaces Obtained by Geometrically Simple Meta-atom Rotations, NANO LETTERS, Vol: 23, Pages: 8891-8897, ISSN: 1530-6984

Journal article

Beddoe M, Goelz T, Barkey M, Bau E, Godejohann M, Maier SA, Keilmann F, Moldovan M, Prodan D, Ilie N, Tittl Aet al., 2023, Probing the micro- and nanoscopic properties of dental materials using infrared spectroscopy: A proof-of-principle study, ACTA BIOMATERIALIA, Vol: 168, Pages: 309-322, ISSN: 1742-7061

Journal article

Ezendam S, Nan L, Violi IL, Maier SA, Cortes E, Baffou G, Gargiulo Jet al., 2023, Anti Stokes Thermometry of Plasmonic Nanoparticle Arrays, ADVANCED OPTICAL MATERIALS, ISSN: 2195-1071

Journal article

Zhang Z, Liu P, Lu W, Bai P, Zhang B, Chen Z, Maier SA, Gómez Rivas J, Wang S, Li Xet al., 2023, High-Q collective Mie resonances in monocrystalline silicon nanoantenna arrays for the visible light, Fundamental Research, Vol: 3, Pages: 822-830, ISSN: 2096-9457

Dielectric optical antennas have emerged as a promising nanophotonic architecture for manipulating the propagation and localization of light. However, the optically induced Mie resonances in an isolated nanoantenna are normally with broad spectra and poor Q-factors, limiting their performances in sensing, lasing, and nonlinear optics. Here, we dramatically enhance the Q-factors of Mie resonances in silicon (Si) nanoparticles across the optical band by arranging the nanoparticles in a periodic lattice. We select monocrystalline Si with negligible material losses and develop a unique method to fabricate nanoparticle arrays on a quartz substrate. By extinction dispersion measurements and electromagnetic analysis, we can identify three types of collective Mie resonances with Q-factors ∼ 500 in the same nanocylinder arrays, including surface lattice resonances, bound states in the continuum, and quasi-guided modes. Our work paves the way for fundamental research in strong light-matter interactions and the design of highly efficient light-emitting metasurfaces.

Journal article

Wang J, Weber T, Aigner A, Maier SA, Tittl Aet al., 2023, Mirror-Coupled Plasmonic Bound States in the Continuum for Tunable Perfect Absorption, LASER & PHOTONICS REVIEWS, ISSN: 1863-8880

Journal article

Sortino L, Gülmüs M, Tilmann B, de S Menezes L, Maier SAet al., 2023, Radiative suppression of exciton-exciton annihilation in a two-dimensional semiconductor., Light Sci Appl, Vol: 12

Two-dimensional (2D) semiconductors possess strongly bound excitons, opening novel opportunities for engineering light-matter interaction at the nanoscale. However, their in-plane confinement leads to large non-radiative exciton-exciton annihilation (EEA) processes, setting a fundamental limit for their photonic applications. In this work, we demonstrate suppression of EEA via enhancement of light-matter interaction in hybrid 2D semiconductor-dielectric nanophotonic platforms, by coupling excitons in WS2 monolayers with optical Mie resonances in dielectric nanoantennas. The hybrid system reaches an intermediate light-matter coupling regime, with photoluminescence enhancement factors up to 102. Probing the exciton ultrafast dynamics reveal suppressed EEA for coupled excitons, even under high exciton densities >1012 cm-2. We extract EEA coefficients in the order of 10-3, compared to 10-2 for uncoupled monolayers, as well as a Purcell factor of 4.5. Our results highlight engineering the photonic environment as a route to achieve higher quantum efficiencies, for low-power hybrid devices, and larger exciton densities, towards strongly correlated excitonic phases in 2D semiconductors.

Journal article

Lin R, Chen H, Cui T, Zhang Z, Zhou Q, Nan L, Cheong W-C, Schroeck L, Ramm V, Ding Q, Liang X, Saris S, Wendisch FJ, Maier SA, Fischer RA, Zhu Y, Wang D, Cortes Eet al., 2023, Optimization of p-Type Cu<sub>2</sub>O Nanocube Photocatalysts Based on Electronic Effects, ACS CATALYSIS, Vol: 13, Pages: 11352-11361, ISSN: 2155-5435

Journal article

Ren H, Maier SA, 2023, Nanophotonic Materials for Twisted-Light Manipulation, ADVANCED MATERIALS, Vol: 35, ISSN: 0935-9648

Journal article

Zhang C, Huang B, Li H, Chen H, Yu T, Zhang B, Wang S, Liu C, Luo Y, Maier SA, Li Xet al., 2023, Plasmonic Nanoneedle Arrays with Enhanced Hot Electron Photodetection for Near-IR Imaging, ADVANCED FUNCTIONAL MATERIALS, ISSN: 1616-301X

Journal article

Lv J, Wu Y, Liu J, Gong Y, Si G, Hu G, Zhang Q, Zhang Y, Tang J-X, Fuhrer MSS, Chen H, Maier SAA, Qiu C-W, Ou Qet al., 2023, Hyperbolic polaritonic crystals with configurable low-symmetry Bloch modes, NATURE COMMUNICATIONS, Vol: 14

Journal article

Tirole R, Vezzoli S, Galiffi E, Robertson I, Maurice D, Tilmann B, Maier SA, Pendry JB, Sapienza Ret al., 2023, Double-slit time diffraction at optical frequencies, NATURE PHYSICS, Vol: 19, Pages: 999-+, ISSN: 1745-2473

Journal article

Gargiulo J, Herran M, Violi IL, Sousa-Castillo A, Martinez LP, Ezendam S, Barella M, Giesler H, Grzeschik R, Schluecker S, Maier SA, Stefani FD, Cortes Eet al., 2023, Impact of bimetallic interface design on heat generation in plasmonic Au/Pd nanostructures studied by single-particle thermometry, NATURE COMMUNICATIONS, Vol: 14

Journal article

Weber T, Kühner L, Sortino L, Ben Mhenni A, Wilson NP, Kühne J, Finley JJ, Maier SA, Tittl Aet al., 2023, Intrinsic strong light-matter coupling with self-hybridized bound states in the continuum in van der Waals metasurfaces., Nature Materials, Vol: 22, Pages: 970-976, ISSN: 1476-1122

Photonic bound states in the continuum (BICs) provide a standout platform for strong light-matter coupling with transition metal dichalcogenides (TMDCs) but have so far mostly been implemented as traditional all-dielectric metasurfaces with adjacent TMDC layers, incurring limitations related to strain, mode overlap and material integration. Here, we demonstrate intrinsic strong coupling in BIC-driven metasurfaces composed of nanostructured bulk tungsten disulfide (WS2) and exhibiting resonances with sharp, tailored linewidths and selective enhancement of light-matter interactions. Tuning of the BIC resonances across the exciton resonance in bulk WS2 is achieved by varying the metasurface unit cells, enabling strong coupling with an anticrossing pattern and a Rabi splitting of 116 meV. Crucially, the coupling strength itself can be controlled and is shown to be independent of material-intrinsic losses. Our self-hybridized metasurface platform can readily incorporate other TMDCs or excitonic materials to deliver fundamental insights and practical device concepts for polaritonic applications.

Journal article

Lin T, Yang T, Cai Y, Li J, Lu G, Chen S, Li Y, Guo L, Maier SA, Liu C, Huang Jet al., 2023, Transformation-optics-designed plasmonic singularities for efficient photocatalytic hydrogen evolution at metal/semiconductor interfaces, Nano Letters: a journal dedicated to nanoscience and nanotechnology, Vol: 23, Pages: 5288-5296, ISSN: 1530-6984

Inspired by transformation optics, we propose a new concept for plasmonic photocatalysis by creating a novel hybrid nanostructure with a plasmonic singularity. Our geometry enables broad and strong spectral light harvesting at the active site of a nearby semiconductor where the chemical reaction occurs. A proof-of-concept nanostructure comprising Cu2ZnSnS4 (CZTS) and Au-Au dimer (t-CZTS@Au-Au) is fabricated via a colloidal strategy combining templating and seeded growth. On the basis of numerical and experimental results of different related hybrid nanostructures, we show that both the sharpness of the singular feature and the relative position to the reactive site play a pivotal role in optimizing photocatalytic activity. Compared with bare CZTS, the hybrid nanostructure (t-CZTS@Au-Au) exhibits an enhancement of the photocatalytic hydrogen evolution rate by up to ∼9 times. The insights gained from this work might be beneficial for designing efficient composite plasmonic photocatalysts for diverse photocatalytic reactions.

Journal article

Doiron B, Li Y, Bower R, Mihai A, Dal Forno S, Fearn S, Hüttenhofer L, Cortés E, Cohen LF, Alford NM, Lischner J, Petrov P, Maier SA, Oulton RFet al., 2023, Optimizing hot electron harvesting at planar metal–semiconductor interfaces with titanium oxynitride thin films, ACS Applied Materials and Interfaces, Vol: 25, Pages: 30417-30426, ISSN: 1944-8244

Understanding metal-semiconductor interfaces is critical to the advancement of photocatalysis and sub-bandgap solar energy harvesting where electrons in the metal can be excited by sub-bandgap photons and extracted into the semiconductor. In this work, we compare the electron extraction efficiency across Au/TiO2 and titanium oxynitride (TiON)/TiO2-x interfaces, where in the latter case the spontaneously forming oxide layer (TiO2-x) creates a metal-semiconductor contact. Time-resolved pump-probe spectroscopy is used to study the electron recombination rates in both cases. Unlike the nanosecond recombination lifetimes in Au/TiO2, we find a bottleneck in the electron relaxation in the TiON system, which we explain using a trap-mediated recombination model. Using this model, we investigate the tunability of the relaxation dynamics with oxygen content in the parent film. The optimized film (TiO0.5N0.5) exhibits the highest carrier extraction efficiency (NFC ≈ 2.8 × 1019 m-3), slowest trapping, and an appreciable hot electron population reaching the surface oxide (NHE ≈ 1.6 × 1018 m-3). Our results demonstrate the productive role oxygen can play in enhancing electron harvesting and prolonging electron lifetimes, providing an optimized metal-semiconductor interface using only the native oxide of titanium oxynitride.

Journal article

Tilmann B, Huq T, Possmayer T, Dranczewski J, Nickel B, Zhang H, Krivitsky L, Kuznetsov AI, de S Menezes L, Vezzoli S, Sapienza R, Maier SAet al., 2023, Comparison of Harmonic Generation from Crystalline and Amorphous Gallium Phosphide Nanofilms, ADVANCED OPTICAL MATERIALS, ISSN: 2195-1071

Journal article

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