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The role of oxygen doping on elemental intermixing at the PVD-CdS/Cu (InGa)Se <sub/>2</sub> heterojunction
摘要： Elemental intermixing at the CdS/CuIn1?xGaxSe2 (CIGS) heterojunction in thin‐film photovoltaic devices plays a crucial role in carrier separation and thus device efficiency. Using scanning transmission electron microcopy in combination with energy dispersive X‐ray mapping, we find that by controlling the oxygen in the sputtering gas during physical vapor deposition (PVD) of the CdS, we can tailor the degree of elemental intermixing. More oxygen suppresses Cu migration from the CIGS into the CdS, while facilitating Zn doping in the CdS from the ZnO transparent contact. Very high oxygen levels induce nanocrystallinity in the CdS, while moderate or no oxygen content can promote complete CdS epitaxy on the CIGS grains. Regions of cubic Cu2S phase were observed in the Cu‐rich CdCuS when no oxygen is included in the CdS deposition process. In the process‐of‐record sample (moderate O2) that exhibits the highest solar conversion efficiency, we observe a ~26‐nm‐thick Cu‐deficient CIGS surface counter‐doped with the highest Cd concentration among all of the samples. Cd movement into the CIGS was found to be less than 10 nm deep for samples with either high or zero O2. The results are consistent with the expectation that Cd doping of the CIGS surface and lack of Zn diffusion into the buffer both enhance device performance.
关键词： scanning transmission electron microscopy,Cu diffusion,Cu (In,Ga)Se2 photovoltaics,CdS structure,STEM‐EDS mapping
更新于2025-09-04 15:30:14
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Surfactant Free Hydrothermal Synthesis of Zn <sub/>2</sub> SnO <sub/>4</sub> Nanoparticles and Their Functional Properties
摘要： A simple, low temperature, cost effective, surfactant free and scalable synthesis of technologically important Zn2SnO4 (ZTO) nanoparticles with controllable size and shape has been developed. X-ray diffraction (XRD), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) of the synthesized ZTO nanoparticles revealed the formation of highly pure crystalline ZTO phase with the spinel-like structure. The Raman spectrum of the sample was dominated by the A1g vibration mode of pure ZTO phase. From UV–Vis absorption measurements, a band gap (Eg) of 3.78 eV was determined. The photocatalytic activity of the ZTO nanoparticles was evaluated for the photodegradation of methylene blue (MB) under UV-Vis light irradiation. The ZTO-assisted photocatalytic degradation of MB is complete in 25 minutes indicating good photocatalytic activity of ZTO. Mass spectrometric (MS) analysis of degradation intermediates isolated at regular time intervals reveals the presence of azure A, azure B and thionin which are demethylated products of the MB, indicating that the degradation is initiated by demethylation of the molecule.
关键词： Nanoparticles,Photocatalysis,Zn2SnO4,Transmission electron microscopy,Hydrothermal Synthesis
更新于2025-09-04 15:30:14
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286 nm monolithic multicomponent system
摘要： We present a 286 nm monolithic multicomponent system in which two identical multiple quantum well (MQW) diodes merge with a waveguide together on a single chip. The monolithic multicomponent system allows all existing standard fabrication processes and establishes an optical link between two MQW-diodes because of the simultaneous emission-detection phenomenon. One MQW-diode transcribes electronic information into an optical signal to be coupled into a waveguide. The guided light then propagates along the waveguide to the other MQW-diode that converts the optical signal into an electronic one. A spatial light transmission at 50 Mbps is demonstrated using non-return-to-zero on–off keying modulation.
关键词： monolithic multicomponent system,multiple quantum well diodes,286 nm,spatial light transmission,waveguide,simultaneous emission-detection phenomenon,optical link
更新于2025-09-04 15:30:14
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State Primary Standard GET 156-2015 of Units of Spectral Coefficients of Directional Transmission, Diffuse and Specular Reflections in the Wavelength Range from 0.2 to 20.0 μm
摘要： We present the composition of the State Primary Standard GET 156-2015 of units of the spectral coefficients of directional transmission, diffuse and specular reflections in the wavelength range from 0.2 to 20.0 μm. Metrological characteristics of the standard are given.
关键词： specular reflection,diffuse reflection,directional transmission,key comparisons,spectrophotometry,optical properties of materials
更新于2025-09-04 15:30:14
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[IEEE 2018 IEEE 7th Global Conference on Consumer Electronics (GCCE) - Nara, Japan (2018.10.9-2018.10.12)] 2018 IEEE 7th Global Conference on Consumer Electronics (GCCE) - Multiple Watermarking for Compressed Sensing with Robust Transmission Applications
摘要： Compressed sensing (CS) is a new research branch in multimedia compressing, which is famous for its superior performance. Due to its digital nature, it is easy to copy and distribute the compressed files in digital format, and the issues relating to digital rights management (DRM) applications would be in urgent need. We propose to hide multiple watermarks in compressed sensing coefficients. Color images consisting of three color planes with high correlations are selected for watermark embedding. Multiple watermarks are embedded into the CS coefficients corresponding to different color planes. With our method, watermarked images are suitable for transmitting over lossy channels, while the copyright of color images can be retained. Simulations have presented the effectiveness for the proposed algorithm.
关键词： color planes,compressed sensing,multiple watermarking,robust transmission
更新于2025-09-04 15:30:14
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Copper Cobalt Magnetic Ceramic Materials Characterization at Terahertz Frequencies
摘要： This study presents the complex index of refraction and the complex permittivity of a magnetic ceramic material made of copper, cobalt, and iron oxides. The index of refraction and the extinction coefficient of the CuCo-ferrite exhibit an almost frequency independent behavior and were averaged to n = 3.62 ± 0.05 and k = 0.06 ± 0.02, respectively, over the frequency range from 0.2 to 1 THz. The corresponding complex permittivity was ε’ = 13.12 ± 0.35 for the real part and ε’’ = 0.46 ± 0.15 for the imaginary one. The absorption coefficient and the transmittance of the CuCo-ferrite were also determined. The absorption coefficient exhibits a dip at ~0.35 THz, which corresponds to a peak in transmittance at this frequency. The impact of the observations on the potential realization of novel THz electronic devices is discussed.
关键词： Terahertz,Ferrites,Transmission,Permittivity,Refractivity
更新于2025-09-04 15:30:14
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Asymmetry of the Defect Structure of Semipolar GaN Grown on Si(001)
摘要： The defect structure of a thick (~15 μ m) semipolar gallium nitride (GaN) layer grown by hydride–chloride vapor phase epitaxy on a Si(001) substrate with buffer layers has been studied by transmission electron microscopy. The asymmetry of the defect structure of GaN epilayer has been revealed and analyzed. The influence of this asymmetry on the rate of decrease in the density of threading dislocations in the growing epitaxial layer is discussed.
关键词： transmission electron microscopy,semipolar GaN,threading dislocations,hydride–chloride vapor phase epitaxy,defect structure
更新于2025-09-04 15:30:14
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[IEEE 2018 IEEE Radio and Antenna Days of the Indian Ocean (RADIO) - Mauritius (2018.10.15-2018.10.18)] 2018 IEEE Radio and Antenna Days of the Indian Ocean (RADIO) - Five-Stub Directional Device with Substantially Reduced Overall Dimensions
摘要： In this paper, a compact design of a five-stub microstrip coupler with significantly reduced overall dimensions has been investigated. To reduce the size, an artificial transmission line was used, with equivalent characteristics at a central operating frequency of 1000 MHz and in its vicinity, with the characteristics of an even-wave-length segment. Using the program of electrodynamic modeling AWR DE, a standard and compact coupler design was simulated. Due to the fact that the artificial line is shorter and the protruding elements are located, so that to maximally use the free space of the coupler without crossing with neighboring conductive lines from other lines, it was possible to reduce the area of the traditional coupler by 70% in relation to the area of the standard design, while the reduction in the band of operating frequencies occurred by 10%.
关键词： five-stub coupler,microstrip coupler,AWR DE,miniaturization,artificial transmission line
更新于2025-09-04 15:30:14