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Amplification of the Zeroth Order Mode in Ultra-thin Layers
摘要： The ultra-thin limit regime is characterized by a structure which at least in one dimension is signi?cantly smaller than the incoming light wavelength. The absorption in this regime is characterized either by very weak absorption or by a broad peak attributed to the zeroth order Fabry-Perot mode. We show that this mode provides a 14.5% ultimate ef?ciency in a 25 nm GaAs slab on a gold substrate. GaAs in air achieves only a 5% for a 10 nm slab. Such an ampli?cation of the resonance absorption is attributed to the high losses of the substrate. For very high losses, the zeroth order mode transits from an over-damped regime to an under-damped one.
关键词： absorption,Solar cells,optical coating,quasinormal modes,optics
更新于2025-09-23 15:23:52
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Effect of Deposition Pressure, Nitrogen Content and Substrate Temperature on Optical and Mechanical Behavior of Nanocomposite Al-Si-N Hard Coatings for Solar Thermal Applications
摘要： Hard and optically transparent nanocomposite Al-Si-N thin films were deposited using DC magnetron sputtering at different process parameters. There was a significant effect of these parameters on the film properties affecting its mechanical and optical behavior. The nitrogen content or pressure, deposition pressure and substrate temperature strongly influence the phase formation which governs the hardness and optical transparency of the coating. Hardness was measured between 18 and 30 GPa. The band gap could be varied in the range of 3.8-4.2 eV by varying nitrogen pressures in the chamber during deposition. The films showed (0-80)% transparency in UV and visible region depending on the sputtering conditions.
关键词： mechanical behavior,optical coating,nanocomposite hard coatings
更新于2025-09-23 15:21:21
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High-Temperature Selective Emitter Design and Materials: Titanium Aluminum Nitride Alloys for Thermophotovoltaics
摘要： The efficiency of a thermophotovoltaic (TPV) system depends critically upon the spectral selectivity and stability of an emitter, which may operate most effectively at temperatures in excess of 1000 °C. We computationally design and experimentally demonstrate a novel selective emitter design based on multilayer nanostructures, robust to off-normal emission angles. A computational search of the material and temperature compatibility space of simple emitter designs motivates new material classes and identifies several promising multilayer nanostructure designs for both TPV absorber and emitter applications. One such structure, comprising a thin (<100 nm) tunable TixAl1?xN (TiAlN) absorber and refractory oxide Bragg reflector is grown on W metal foil. In agreement with simulations, the emitter achieves record spectral efficiency (43.4%) and power density (3.6 W/cm2) for an emitter with at least 1 h of high temperature (>800 °C) operation.
关键词： solar thermophotovoltaics,titanium aluminum nitride,selective emitters,optical coating,atomic layer deposition
更新于2025-09-11 14:15:04
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Enhanced Hybridization and Nanopatterning via Heated Liquid-Phase Infiltration into Self-Assembled Block Copolymer Thin Films
摘要： Organic-inorganic hybrids featuring tunable material properties can be readily generated by applying vapor- or liquid-phase infiltration (VPI or LPI) of inorganic materials into organic templates, with resulting properties controlled by type and quantity of infiltrated inorganics. While LPI offers more diverse choices of infiltratable elements, it tends to yield smaller infiltration amount than VPI, but the attempt to address the issue has been rarely reported. Here, we demonstrate facile temperature-enhanced LPI method to control and drastically increase the quantity and kinetics of Pt infiltration into self-assembled polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) block copolymer (BCP) thin films. By applying LPI at mildly elevated temperatures (40 – 80 °C), we showcase controllable optical functionality of hybrid BCP films along with conductive three-dimensional (3D) inorganic nanostructures. Structural analysis reveals enhanced metal loading into BCP matrix at higher LPI temperatures, suggesting multiple metal ion infiltration per monomer of P2VP. Combining temperature-enhanced LPI with hierarchical multilayer BCP self-assembly, we generate BCP-metal hybrid optical coatings featuring tunable antireflective properties as well as scalable conductive 3D Pt nanomesh structures. Enhanced material infiltration and control by temperature-enhanced LPI not only enables tunability of organic-inorganic hybrid nanostructure and properties but also expands the application of BCPs for generating uniquely functional inorganic nanostructures.
关键词： self-assembled block copolymers,hybrid thin film,optical coating,Pt nanomesh,Liquid-phase infiltration
更新于2025-09-11 14:15:04