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High-Periphery GaN HEMT Modeling up to 65 GHz and 200°C
摘要： In this article, we report on the temperature-dependent GaN HEMT behavior. To evaluate the potentialities of this kind of active solid-state electronic device at its best, the experiments are performed at extreme operating conditions. As a case study, we consider a large 0.25-μm GaN HEMT with a gate periphery of 1.5 mm, providing a high dissipated power of 5.1 W. The tested semiconductor device is characterized by measuring scattering parameters at high frequencies up to 65 GHz and at high ambient temperature up to 200°C. To assess the impact of the thermal effects on high-frequency GaN HEMT performance, an equivalent circuit is analytically extracted and then used to determine the main RF figures of merit. The achieved experimental results show evidence that the increase of the temperature causes a significant degradation in device performance.
关键词： scattering parameter measurements,high-power,GaN HEMT,high-temperature,Active solid-state electronic device,millimeter-wave frequency
更新于2025-09-10 09:29:36
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Impact of Precise Control over Microstructure in Thiophene–Selenophene Copolymers
摘要： Controlling the sequence of repeat units in a synthetic polymer has been a long-standing topic of interest in chemistry. As methods to regulate sequence become more sophisticated, it is critical to consider how controlling the arrangement of repeat units along the polymer backbone impacts properties. In this work, thiophene?selenophene copolymers (statistical and periodic) were compared to elucidate the impact of periodicity on electronic properties and structural organization in conjugated macromolecules. Polymers were synthesized using catalyst-transfer polycondensation (CTP) enabling control over molecular weight and dispersity. The study revealed that optical bandgaps and redox potentials of periodic and statistical copolymers varied with composition in a predictable manner, regardless of monomer ordering along the chain. While the bandgaps of the two types of copolymers were indistinguishable, X-ray scattering revealed di?erences in solid-state packing. Both types of copolymers exhibited well-de?ned morphologies, but larger π-stacking distances and more orientational disorder were evident in the statistical systems. This indicates periodicity is an attribute that should be considered when synthesizing semiconducting materials.
关键词： solid-state packing,periodicity,electronic properties,thiophene?selenophene copolymers,catalyst-transfer polycondensation
更新于2025-09-10 09:29:36
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Precise Control of Localized Surface Plasmon Wavelengths Is Needed for Effective Enhancement of Triplet-Triplet Annihilation-Based Upconversion Emission
摘要： In this study, we demonstrate that the localized surface plasmon (LSP) resonance of metal nanoparticles, depending strictly on the generating wavelength of LSP resonance, can have both beneficial enhancement and harmful quenching effects on a triplet-triplet annihilation-based upconversion (TTA-UC) emission. When the LSP resonance band of anisotropic silver nanoprisms spectrally overlapped with the photoexcitation wavelength of a sensitizer and the fluorescence of an emitter, an increase in the photoexcitation efficiency and an acceleration of the radiative decay rate were respectively induced, resulting in an effective enhancement in the TTA-UC emission. Furthermore, the overlapping with the photoexcitation wavelength led to a significant decrease (93%) in the threshold light excitation intensity, which greatly enhances the figure-of-merit in TTA-UC systems. However, when the LSP resonance band overlapped with the phosphorescence band of the sensitizer, the TTA-UC emission was extremely quenched, accompanied by the enhanced phosphorescence and the decreased phosphorescence lifetime. These results suggest that the decrease in the TTA-UC emission is a result of the competition between the triplet-triplet energy transfer to the emitter and the LSP-induced nonradiative energy transfer to the silver nanoprisms from the triplet-excited sensitizer. This discovery of the conflicting effects of LSP resonance provides an important guideline: a precise adjustment of LSP resonance wavelengths is needed for the efficient enhancement of TTA-UC emission. This requirement is different from those of other fluorescence systems such as single downconverted fluorophores and lanthanide-based upconversion nanoparticles.
关键词： solid state,fluorescence,phosphorescence,silver nanoprisms,localized surface plasmon resonance,triplet-triplet annihilation,photon upconversion
更新于2025-09-10 09:29:36
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3.4: Room Temperature Dual Emission of Fluorescence and Phosphorescence in the Solid State
摘要： A white light emission comprised of fluorescence and phosphorescence was observed at room temperature in the solid state. The OLED device used the dual emission material was fabricated and showed white EL light.
关键词： Dual emission OLED device,White emission,Dual emission,Solid state
更新于2025-09-10 09:29:36
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[Nanostructure Science and Technology] Nanowire Electronics || Metal-Semiconductor Compound Contacts to Nanowire Transistors
摘要： Semiconductor nanowires [1–4] are promising building blocks for next-generation ultrascaled devices for electronic [5–7] and optoelectronic [8–10] applications. An important aspect for the development, maturity, and ef?ciency of these ultrascaled devices is the detailed understanding of and control over the phase transformation that accompanies the formation of their compound contacts for lithography-free self-aligned gate design [11, 12]. The term “compound” here refers to the formed phases that have ?xed stoichiometry between metal and semiconductor elements, to be distinguished from the broader “alloy” term for phases that may include nonstoichiometric or amorphous structure. This distinction is important because the formation of a low resistance, crystalline, and thermally stable compound contact is most preferred for realizing reliable functionality in ultrascaled semiconductor transistors. Usually, the phase of compound contact and its interfacial property with semiconductor nanowire (NW) can largely affect the band alignment and charge injection in NW channels. This demands the detailed studies of the metal-semiconductor solid-state reactions, including the formed compound phases, reaction kinetics, and their correlation to the device performances. In this book chapter, we provide a thorough discussion of these three topics.
关键词： metal-semiconductor solid-state reactions,compound contacts,reaction kinetics,phase transformation,Semiconductor nanowires,device performances
更新于2025-09-10 09:29:36
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Absorption and luminescence studies of Sm3+ ions activated in distinct phosphate glasses for reddish orange light applications
摘要： In the present work, we report the optical properties of Sm3+ ions doped glasses having chemical compositions (70-x) NH4H2PO4+15Na2O+15M2O + xSm2O3 (where x = 0.5 mol% and M = Li, Mg, Ca, Sr, Ba). Structural details are obtained from XRD, SEM, FTIR, Raman and solid-state 31P NMR spectra. Absorption (UV-NIR), emission and lifetime measurements have been performed and discussed using Judd-Ofelt theory. Various radiative parameters are calculated and discussed. Visible emissions from 4G5/2 excited state have been characterized and the experimental lifetimes of these levels have been compared with those obtained theoretically by using J-O approach. Quantum e?ciencies are reported. The CIE chromaticity co-ordinates of the present glass matrices con?rmed reddish-orange light emission. Hence the prepared samples can be treated as candidates for reddish orange light applications.
关键词： Photoluminescence,Phosphate glass,Absorption,FTIR,Emission cross-section,Solid state 31P NMR
更新于2025-09-10 09:29:36
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Design of Thermochromic Luminescent Dyes Based on the Bis(o-carborane)-Substituted Benzobithiophene Structure
摘要： To obtain solid-state emissive materials having stimuli-responsive luminescent chromic properties without phase transition, benzobithiophenes modified with two o-carborane units having various substituents in the adjacent phenyl ring in o-carborane were designed and synthesized. Their emission colors were strongly affected not only by the substituents at the para-position of the phenyl ring but also by molecular distribution in the solid state. In particular, the emission colors were changed by heating without crystal phase transition. It was proposed that their thermochromic properties were correlated not with isomerization but with the molecular motion at the distorted benzobithiophene moiety.
关键词： Thermochromic,Bis(o-carborane)-Substituted Benzobithiophene,Solid-State Emissive Materials,Stimuli-Responsive,Luminescent Dyes
更新于2025-09-10 09:29:36
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Encyclopedia of Spectroscopy and Spectrometry || Optical Spectroscopy of Rare-Earth Ions in the Solid State
摘要： The birth of optical spectroscopy as science can be considered from the time when in 1672 Isaac Newton published his famous paper describing the results of experiments where, using a glass prism, he decomposed a beam of sunlight into its optical spectral components ranging from blue to red. Since that time, scientists and engineers studied a broad range of phenomena associated with the interaction of light with matter, using the fact that light actually contains different spectral components. Within a field of optical spectroscopy, it is hard to underestimate the importance of optical spectroscopy of different optical centers in solid-state materials because of numerous scientific and industrial applications of such optical systems. These applications range from studying fundamental properties of impurity centers in solids, solid-state material properties, up-conversion devices, scintillators, and Faraday rotators to a creation of solid-state lasers.
关键词： rare-earth ions,Fu¨chtbauer–Ladenburg theory,optical spectroscopy,Judd–Ofelt theory,McCumber theory,electron–phonon coupling,Franck–Condon principle,solid state
更新于2025-09-10 09:29:36
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Solid-State Preparation, Structural Characterization, Physical Properties and Theoretical Studies of a Series of Novel Rare-earth Metal-Chalcogenides with Unprecedented Closed Cavities
摘要： Multinary rare-earth metal-chalcogenides have aroused great concern owing to their special structure characteristics and diverse physical functions. In this work, five novel rare-earth chalcogenides adopt the formula Cs2[RE8InS14] (where RE = Ho–Lu), has been obtained by the elementals mixture in CsCl flux at 1273 K. They are isotype and belong to the orthorhombic Cmca (no. 64) [a = 15.711(7)–15.385(2) ?, b = 22.232(2)–21.786(2) ?, c = 15.483(5)–15.244(2) ?, V = 5408.4(4)–5130.1(7) ?3 and Z = 8], exhibiting a dense 3D [RE8InS14] framework consisting of RES6 octahedron and discrete InS4 tetrahedron. The large closed-cavities Cs4@S26 are far apart embedded within the network along bc-plane, which is discovered for the first time. The band gaps from 2.45 to 2.72 eV for Cs2[RE8InS14] were deduced from the UV?Vis–NIR spectroscopy based on the Kubelka-Munk function. Magnetic test indicates that the Cs2[RE8InS14] (RE = Ho–Yb) compounds possess para-magnetism above 50K. In addition, the solid-state preparation, structural characterization, theoretical studies together with a structure–G/H ratio relationship (G = atomic number of guest metals; H = atomic number of host metals) are also presented.
关键词： crystal structure,solid-state reaction,magnetic properties,large closed cavities,rare-earth metal-chalcogenides
更新于2025-09-10 09:29:36
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Photoluminescence characteristics of Pr3+ doped PbGdB7O13 as a new red emitting phosphor
摘要： A red phosphor Pr3+ doped PbGdB7O13 was synthesized by high temperature solid state reaction. The effect of Pr3+ doped concentration on the luminescent properties of the phosphor was investigated. The emission spectrum includes an apex at about 607 nm, corresponding to the 3P0→3H6 transition of the Pr3+ ion activator. For PbGd1-xB7O13:xPr3+, the emission peak intensity first increases with the increase of Pr3+ concentration, and reaches the maximum when the Pr3+ concentration is 0.02, and then decreases with the increase of Pr3+ concentration. The CIE coordinates of the PbGdB7O13:0.02Pr3+ phosphor was calculated to be (0.6332, 0.3651), falling into the red color. Therefore, there is a potential application on display, indication or illumination.
关键词： Photoluminescence,High temperature solid state reaction,CIE,Borate
更新于2025-09-10 09:29:36