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High-temperature high pressure synthesis of monoclinic Y2O3
摘要： In this work, synthesis of cubic Y2O3 by calcining yttrium based coordination polymer (Y-CP) which were obtained by microwave-assisted method was reported. Monoclinic Y2O3 was obtained by treating the cubic Y2O3 under high temperature high pressure (HTHP) on a large volume cubic multi-anvil high pressure apparatus. The effect of temperature on the preparation was studied. The morphology and crystal phase of all samples have been characterized by the scanning electron microscope (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) spectra. What more, the photoluminescence (PL) property of the Y2O3: Eu3+ sample was investigated. This method can be used to prepare other rare earth oxide with various phase.
关键词： Coordination polymer,luminescence,Y2O3,high temperature high pressure,Phase transformation
更新于2025-09-04 15:30:14
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O12:Ce scintillator
摘要： The light yield (LY) and decay kinetics of a single crystal scintillator of Gd3Al2Ga3O12(GAGG):Ce were measured for 0.662 MeV ??- and 5.48 MeV ??-rays between ?100 ?C and room temperature. As the temperature decreased, the LY increased by 20% for ??-rays, reaching its maximum at around ?70 ?C, and increased monotonously by 50% for ??-rays. Both the rise and decay times increased gradually. Furthermore, the results indicate that pulse shape discrimination is most effective at room temperature.
关键词： Pulse shape discrimination,Light yield,Temperature dependence,Scintillator,Gd3Al2Ga3O12(GAGG):Ce,Particle detector,Decay time
更新于2025-09-04 15:30:14
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Additive-Manufacturing of 3D Glass-Ceramics down to Nanoscale Resolution
摘要： Fabrication of a true-3D inorganic ceramic with resolution down to nanoscale (～ 100 nm) using sol-gel resist precursor is demonstrated. The method has an unrestricted free-form capability, control of the ?ll-factor, and high fabrication throughput. A systematic study of the proposed approach based on ultrafast laser 3D lithography of organic-inorganic hybrid sol-gel resin followed by a heat treatment enabled formation of inorganic amorphous and crystalline composites guided by the composition of the initial resin. The achieved resolution of 100 nm was obtained for 3D patterns of complex free-form architectures. Fabrication throughput of 50 × 103 voxels/s is achieved; voxel - a single volume element recorded by a single pulse exposure. A post-exposure thermal treatment was used to form a ceramic phase which composition and structure were dependent on the temperature and duration of the heat treatment as revealed by Raman micro-spectroscopy. The X-ray diffraction (XRD) showed a gradual emergence of the crystalline phases at higher temperatures with a signature of cristobalite SiO2, a high-temperature polymorph. Also, a tetragonal ZrO2 phase known for its high fracture strength was observed. This 3D nano-sintering technique is scalable from nanoscale to millimeter dimensions and opens a conceptually novel route for optical 3D nano-printing of various crystalline inorganic materials de?ned by an initial composition for diverse applications for microdevices designed to function in harsh physical and chemical environments and at high temperatures.
关键词： ultrafast 3D laser nanolithography,3D nanoscale optical printing,inorganic 3D structures,high-temperature glass-ceramic materials,calcination
更新于2025-09-04 15:30:14
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Gate voltage and temperature dependent Ti-graphene junction resistance toward straightforward p-n junction formation
摘要： High-quality metal-graphene contact is crucial for the fabrication of high-performance graphene transistors. Although Ti has been widely used as metal electrodes in graphene-based devices owing to its excellent adhesive capability, contact resistance (Rc) for Ti/graphene (Ti/Gr) is typically high and varies largely by three orders of magnitude from ～103 to 106 Ω μm. Here, we have systematically investigated the effects of gate voltage (VG) and temperature (T) on Rc in the Ti/Gr interface. Besides significant VG dependence, Rc in the n branch is always larger than that in the p branch, indicating a Ti induced n-doping in graphene. In addition, Rc exhibits an anomalous temperature dependence and drops significantly as the temperature decreases, reaching ～234 Ω μm at 20 K. Such Ti/Gr contact can adjust the Fermi energy of up to 0.15 eV and can also directly form a well-defined sharp p-n junction without extra gates or chemical doping. These findings pave the way to develop the next generation of graphene-based electronic and optoelectronic devices.
关键词： gate voltage,temperature dependence,Ti-graphene junction,p-n junction,graphene,contact resistance
更新于2025-09-04 15:30:14
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Efficient and Long-lived Room Temperature Organic Phosphorescence: Theoretical Descriptors for Molecular Designs
摘要： Room-temperature phosphorescence (RTP) with long afterglow from pure organic materials has attracted great attentions for their potential applications in biological imaging, digital encryption and optoelectronic device and so on. Organic materials have been long considered to be non-phosphorescence owing to the weak molecular spin-orbit coupling and highly sensitive to temperature. However, recently, some purely organic compounds can demonstrate highly efficient RTP with long afterglow upon aggregation while others fail. Namely, it remains a challenge to expound the underline mechanisms. In this study, we present the molecular descriptors to character the phosphorescence efficiency and lifetime. For prototypical RTP system consists of carbonyl group and π-conjugated segments, the excited states can be regarded as admixture of n→π* (with portion α) and π→π* (portion β). Starting from phosphorescent process and El-Sayed rule, we deduced that (i) the intersystem crossing (ISC) rate of S1→Tn is mostly governed by the modification of the product of α and β, and (ii) the ISC rate of T1→S0 is determined by the β value of T1. Thus, the descriptors (γ=α×β, β) can be employed to describe the RTP character of organic molecules. From hybrid quantum mechanics and molecular mechanics (QM/MM) calculations, we illustrated the relationships amongst the descriptors (γ, β), phosphorescent efficiency and lifetime, as well as spin-orbit coupling constants. We stressed that the large γ and β values are favorable to the strong and long-lived RTP in organic materials. Experiments have reported confirmations of these molecular design rules.
关键词： Organic materials,Molecular descriptors,Room-temperature phosphorescence,QM/MM calculations,Spin-orbit coupling
更新于2025-09-04 15:30:14
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[IEEE 2018 IEEE 7th World Conference on Photovoltaic Energy Conversion (WCPEC) (A Joint Conference of 45th IEEE PVSC, 28th PVSEC & 34th EU PVSEC) - Waikoloa Village, HI, USA (2018.6.10-2018.6.15)] 2018 IEEE 7th World Conference on Photovoltaic Energy Conversion (WCPEC) (A Joint Conference of 45th IEEE PVSC, 28th PVSEC & 34th EU PVSEC) - Reactive Silver Ink as a Novel Low-Temperature Metallization: Monitoring Corrosion
摘要： Reactive silver ink (RSI) forms low-resistivity (<5 μΩ?cm) metallization at temperatures below 100 °C –enabling lower resistive losses for thermally sensitive solar cells while drastically reducing Ag usage compared to other low-temperature Ag pastes. However, before adoption of the technology many reliability related questions must be addressed. Ag-based metallizations are susceptible to corrosion by acetic acid formed in encapsulated modules, resulting in increased resistive losses. Here we report on corrosion of three types of metallizations; high-firing-temperature Ag paste (HT Ag Paste), low-temperature Ag paste (LT Ag Paste), and RSI. We develop a method for exposing these metallizations to dilute acetic acid in concentrations comparable to those found in field- and damp heat-exposed modules. We find that HT Ag and RSI are quickly affected by acetic acid exposure after only 24 h. Interestingly, Raman spectroscopy suggests the formation of AgCl or AgCH3COO on HT Ag Paste, dissolution of AgCH3COO from RSI, and LT Ag Paste remains relatively unchanged throughout 2936 h of exposure to diluted acetic acid.
关键词： low temperature metallization,silver usage,metallization,silver,corrosion
更新于2025-09-04 15:30:14
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[Institution of Engineering and Technology 12th European Conference on Antennas and Propagation (EuCAP 2018) - London, UK (9-13 April 2018)] 12th European Conference on Antennas and Propagation (EuCAP 2018) - Predicting Mean Radiative Temperature at Millimeter Wavelengths in Continental Climate Areas
摘要： The aim of this work is to present a parametric model for the prediction of the down-welling mean radiative temperature (Tmr) in the microwave region. For the model set-up, the Sky Noise Eddington Model has been exploited to generate a synthetic clouds dataset driven by radiosounding observations. The core of the model, developed in continental climate areas, is the normalization of Tmr for the surface temperature (TS) of the geographic area of interest that makes the Tmr/TS model applicable in each site belonging to the considered climatic area. Retrieval of the predicted Tmr can be done by multiplying the Tmr/TS obtained from the parametric model at the considered attenuation value for the average TS. The model parameters depend on frequency and elevation angle within the range from 23.8 GHz to 49.5 GHz and from 90° to 5°, respectively. A preliminary verification of the model is accomplished, at 23.8 GHz and 31.4 GHz, exploiting Sun-tracking radiometric measurements available in Rome (NY, USA) with promising results: RMSE never exceeds 0.02 and 0.1 at 23.8 GHz and 31.4 GHz, respectively.
关键词： Mean radiative temperature,microwave radiometry,Atmospheric radio-propagation
更新于2025-09-04 15:30:14
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Imaging With 3-D Aperture Synthesis Radiometers
摘要： The spatial resolution is still a problem in passive microwave remote sensing, especially in low frequency. In recent years, the satellite formation flying has been proposed. Based on this technique, a large array is able to be synthesized in orbit to achieve higher spatial resolution. However, it is a big challenge for the control system to constrain all the satellites in a coplane in orbit. The 3-D array configuration is a good choice for a synthesized array based on satellite formation flying. In this paper, the complete formulation of visibility functions, including system imperfections, in a 3-D aperture synthesis radiometer (3-D ASR) is derived. The array factor of a 3-D ASR is defined. The reconstructed modified brightness temperature (BT) is a 3-D linear convolution of the modified BT and the array factor. Based on this relationship, the reconstruction method for a practical 3-D ASR is studied. The numerical results demonstrate that the reconstruction method is correct and stable. Finally, a discussion is given to analyze several existing methods that were proposed to reconstruct BT image for 3-D arrays in radio astronomy and earth observation. Compared with these existing methods, our imaging method is more suitable for earth observation based on the technique of satellites formation flying in low earth orbit. In addition, according to the derivations, some mature techniques that were developed for 2-D ASRs may be applied to 3-D ASRs.
关键词： visibility functions,image reconstruction,array factor,3-D aperture synthesis radiometers (3-D ASRs),modified brightness temperature (BT)
更新于2025-09-04 15:30:14
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Model for black silicon formation just from surface temperature non-uniformities
摘要： The scienti?c issue of this paper is the formation of the initial surface roughening during black silicon (b-Si) preparation by maskless SF6/O2 plasma texturing. In detail, the authors investigate a novel approach whether merely substrate temperature dependent surface mechanisms and plasma particle diffusion are suf?cient to theoretically obtain anisotropic etching. For that, a quasi-2D model is developed including the relevant mechanisms such as (i) etching, (ii) the deposition of the masking layer SiOxFy, (iii) plasma particle transport, and (iv) heat diffusion. Further on, a linear stability analysis is applied, ?rstly, to reveal theoretical conditions for anisotropic etching and, secondly, to qualitatively evaluate the impact of the model parameters on the texturing range. The evaluation shows that plasma particle diffusion along the surface is the main factor for nano-roughening. Additionally, the experimentally expected strong dependency of the texturing on the substrate temperature is con?rmed and other extracted dependencies can be correlated to experimental observations. With that, a novel model is introduced explaining the initial b-Si roughening without taking into account surface removal by directed ions.
关键词： surface roughening,anisotropic etching,black silicon,plasma texturing,temperature non-uniformities
更新于2025-09-04 15:30:14
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Temperature Effect on Optical and Electrical Properties of ZnO Films
摘要： Zinc oxide thin films were deposited on a glass substrate by Radio frequency magnetron sputtering. The effect of substrate temperature on the microstructure, optical and electrical properties was investigated. Crystal structure and surface morphology of the films were examined by X-ray diffraction and atomic force microscopy. XRD patterns and AFM images show that the crystallinity and grain size are increasing with the increase of substrate temperature. Electrical properties of the films were evaluated by Hall effect measurements. Experimental results indicate a decrease of film resistivity with the increase of substrate temperature. Zinc oxide films exhibit high transmittance of 84 % in the visible wavelength range 400-800 nm and is independent on the substrate temperature. Present work shows that the enhancement of the ZnO film performance with high transparency and low resistivity can be achieved by increasing the substrate temperature.
关键词： Resistivity,Zinc oxide film,Transmittance,Substrate temperature
更新于2025-09-04 15:30:14