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Oxygen-incorporated single-photon sources observed at the surface of silicon carbide crystals
摘要： The formation of high-brightness single-photon sources (SPSs) that emit single photons at room temperature was recently con?rmed in oxygen-annealed SiC semiconductors (surface SPSs.) However, the defect structure of surface SPSs remains unclear, which makes device fabrication and property control dif?cult. To verify the incorporation of oxygen in surface SPSs, we fabricated SPSs using stable 18O isotopes as oxidants. By comparing this to the case of natural oxygen annealing, we found that the SP emission spectra for the 18O sample tended to have shorter peak wavelengths, slightly narrower peak widths, and higher intensities. Thus, it appeared that, in the case of the 18O sample, the phonon sideband was located closer to the zero-phonon line and that oxygen was incorporated into the defects attributed to the surface SPS.
关键词： single-photon sources,single defect,silicon carbide,oxygen isotope,semiconductors,photoluminescence
更新于2025-09-09 09:28:46
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Crystal and Electronic Structure and Optical Properties of <i>AE</i> <sub/>2</sub> SiP <sub/>4</sub> ( <i>AE</i> = Sr, Eu, Ba) and Ba <sub/>4</sub> Si <sub/>3</sub> P <sub/>8</sub>
摘要： Three new compounds in the AE-Si-P (AE = Sr, Eu, Ba) systems are reported. Sr2SiP4 and Eu2SiP4, the first members of their respective ternary systems, are isostructural to previously reported Ba2SiP4 and crystallize in the noncentrosymmetric I4ˉ2d (no. 122) space group. Ba4Si3P8 crystallizes in the new structure type, in P21/c (no. 14) space group, mP-120 Pearson symbol, Wyckoff sequence e30. In the crystal structures of Sr2SiP4 and Eu2SiP4 all SiP4 tetrahedral building blocks are connected via formation of P–P bonds forming a three-dimensional framework. In the crystal structure of Ba4Si3P8, Si-P tetrahedral chains formed by corner-sharing, edge-sharing, and P–P bonds are surrounded by Ba cations. This results in a quasi-one-dimensional structure. Electronic structure calculations and UV/Vis measurements suggest that the AE2SiP4 (AE = Sr, Eu, Ba) are direct bandgap semiconductors with bandgaps of ca. 1.4 eV and have potential for thermoelectric applications.
关键词： Silicon,Barium,Ternary system,Semiconductors
更新于2025-09-09 09:28:46
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Structural, Optical, and Magnetic Properties of Hydrothermally Grown Fe-Doped ZnO Nanorod Arrays on Glass Substrate
摘要： In this paper, undoped and Fe-doped ZnO nanorod arrays were grown on glass substrate by a facile hydrothermal method. Structural, optical, and magnetic properties of the prepared nanorods were investigated. Structural investigation clearly showed that the prepared nanorods had single phase wurtzite structure without any secondary phases and the prepared undoped and Fe-doped nanorods were grown vertically. The optical characterization revealed that the optical band gap of ZnO nanorods was decreased by increasing the value of Fe concentration. Furthermore, the formation of diluted magnetic semiconductor nanorod arrays was verified. The origin of room temperature ferromagnetism is explained by the bound magnetic polaron concept.
关键词： Diluted magnetic semiconductors,Bound magnetic polaron,Nanorod arrays,Fe-doped ZnO
更新于2025-09-09 09:28:46
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Effects of polyvinylpyrrolidone on structural and optical properties of willemite semiconductor nanoparticles by polymer thermal treatment method
摘要： Willemite is an inorganic semiconductor material used for optoelectronic applications. The present study purposes a new polymer thermal treatment method involving calcination temperature to fabricate the willemite nanoparticles. The effects of polyvinylpyrrolidone (PVP) on the structural and optical properties of the material were thoroughly investigated. Thermogravimetric and its derivative confirmed the decomposition behavior of PVP. The minimum calcination temperature to decompose PVP was appraised at 740 °C. The FTIR and the Raman analyses confirmed the presence of organic source before the calcination process and the formation of the crystalline structure of the willemite nanoparticles after the heat treatment. The optimum PVP concentration in this study based on the FTIR results was found to be 40 g L-1. This is the minimum concentration at which the willemite nanoparticles remained pure with homogenous distribution. X-ray diffraction analysis of the PVP samples before calcination was confirmed to be amorphous, and upon calcination between 800 and 1000 °C, an a-willemite phase was obtained. The morphology and the average particle size were determined with FESEM and HR-TEM analysis. The average particle size is between 23.8 and 36.7 nm. The optical energy band was found to be increasing from 5.24 to 5.32 eV with the corresponding increase in PVP concentration from 20 to 50 g L-1. The findings in this study provides a new pathway to understand the effects of PVP concentrations on the structural and optical properties of willemite semiconductor nanoparticles as it may have key potential applications for future optoelectronic devices.
关键词： Willemite,Nanoparticles,Band gap,Calcination,Polyvinylpyrrolidone,Semiconductors
更新于2025-09-09 09:28:46
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Effects of barrier energy offset and gradient in extended wavelength infrared detectors
摘要： The extended wavelength infrared photodetectors are new class of III-V semiconductor heterojunction-based photodetectors that can detect incoming radiation with an energy significantly smaller than the minimum energy gap (Δ) at the heterojunction interface. Architecture of these photodetectors include a barrier-emitter-barrier epilayers sandwiched between highly doped ohmic top and bottom contact layers. An energy offset (????) between the barriers is necessary for the extended wavelength photodetection. In this work, we study the performance of extended wavelength infrared photodetectors with varying ???? and gradient of the potential barrier. Results indicate that the extended wavelength threshold varied slightly with varying both the gradient and offset. Spectral responsivity, however, increased with the increasing offset and decreased with increasing gradient.
关键词： Extended wavelength infrared photodetectors,III-V semiconductors,GaAs/AlGaAs heterostructures
更新于2025-09-09 09:28:46
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Degradation of GaN-on-GaN vertical diodes submitted to high current stress
摘要： GaN-on-GaN vertical devices are expected to ?nd wide application in power electronics, thanks to the high current densities, the low on-resistance and the high breakdown voltage. So far, only few papers on the reliability of GaN-on-GaN vertical devices have been published in the literature. This paper investigates the degradation of GaN-on-GaN pn diodes submitted to stress at high current density. The study was carried out by means of electrical characterization and electroluminescence (EL) measurements. We demonstrate that: (i) when submitted to stress at high current density, the devices show signi?cant changes in the electrical characteristics: an increase in on-resistance/turn-on voltage, an increase in the generation/recombination components, the creation of shunt-paths. (ii) the increase in on-resistance is strongly correlated to the decrease in the EL signal emitted by the diodes. (iii) the degradation kinetics have a square-root dependence on time, indicative of a di?usion process. The results are interpreted by considering that stress induces a di?usion of hydrogen from the highly-p-type doped surface towards the pn junction. This results in a decrease in hole concentration, due to the creation of MgeH bonds, and in a lower hole injection. As a consequence, on-resistance increases while EL signal shows a correlated decrease.
关键词： Wide band gap semiconductors,Bulk GaN substrates,Vertical diodes,pn junction,Di?usion,Gallium nitride,Hydrogen,Degradation
更新于2025-09-09 09:28:46
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Local, electronic and surface structure of multi–component Fe–doped CdTe(S) systems
摘要： Local structural and electronic properties around Fe in multi–component Cd0.99Fe0.01Te0.97S0.03 system were studied by means of X–ray absorption fine structure (XAFS). Composition of non–polar (110) surfaces of Cd0.97Fe0.03Te and Cd0.99Fe0.01Te0.97S0.03 systems and mechanism of their oxidation in ambient conditions were studied by Atomic Force Microscopy (AFM) and X–ray Photoelectron Spectroscopy (XPS). It has been found that Fe preferentially substitutes Cd, but due to much smaller covalent radius and preferences for paring with S, it causes local distortion of the host CdTe lattice. The distortion is confined to the Fe–immediate surrounding and the second and third coordination shell atoms are (inside experimental uncertainties) placed at distances expected in CdTe. Although local structure around Fe is well defined in the bulk of both samples, their near–surface region is completely depleted from Fe, and in case of Cd0.99Fe0.01Te0.97S0.03 somewhat enriched in S. Special attention is, therefore, paid to characterization of the near–surface region and evaluation of its composition and structure. To that end we have introduced a general standard–free algorithm for XPS data analysis of the two–layer surface structure (bulk, oxide layer, and the impurity layer). Results of the in–depth composition analysis revealed that despite different bulk composition and impurity layer thickness, underneath the topmost impurity layer lays approximately one monolayer of CdTeO3 which passivates the surface.
关键词： XAS,XPS,II–VI semiconductors,iron impurity,oxidation
更新于2025-09-09 09:28:46
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Surface induced charge transfer in CuxIn2-xS3 nanostructures and their enhanced photoelectronic and photocatalytic performance
摘要： Multi-functional semiconducting nanostructures are gaining popularity for application in photoelectronics, energy storage devices and also in industrial and environmental remediation functions. In this regard, CuxIn2-xS3 nanostructures were investigated in detail for their photoelectrical and photocatalytic performance. Their physico-chemical characteristics were at first studied using X-ray diffraction, Raman, UV–vis absorbance, X-ray photoelectron spectroscopy and high resolution electron microscopic tools. CuxIn2-xS3 based flip chip Schottky diodes were demonstrated to attest their improved conductivity and enhanced photoelectrical performance. The photo switching capabilities of a type II p-n CdTe/CuxIn2-xS3 heterojunction was also investigated. In both the device configurations, the current-voltage (I-V) characteristics revealed the forward current and rectification ratio to improve under lower threshold voltages. The time-dependent photoresponse characteristics affirmed the stability of diodes, augmenting the improved/effective separation of photo generated electron hole pairs under illumination. Additionally, the photocatalytic performances of CuxIn2-xS3 nanostructures were inferred under visible light conditions through effective remediation of methylene blue (MB) dye molecules. The obtained results infer the Cu interaction in tetragonal lattice of CuxIn2-xS3 to promote the surface induced charge transfer mechanism in respective nanostructures, thereby enhancing their photoelectronic and photocatalytic functionalities.
关键词： Nanostructures,Photodiodes,Semiconductors,Photocatalysis
更新于2025-09-09 09:28:46
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Applied Nanophotonics || Quantum confinement effects in semiconductors
摘要： Absorption and emission of light by atoms, molecules, and solids arise from electron transitions. Electron confinement phenomena in solids with restricted geometry like nanoparticles, nanorods, or nanoplatelets gives rise to the modification of optical absorption and emission spectra and transition probabilities in semiconductor nanostructures. These phenomena are direct consequences of the wave properties of electrons. In this chapter we describe size-dependent optical properties of semiconductor nanostructures related to quantum confinement.
关键词： optical absorption,semiconductors,nanostructures,emission spectra,Quantum confinement
更新于2025-09-09 09:28:46
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Prediction of Fundamental Properties of Semiconductors and Materials Exploration Using First-Principles Calculations
摘要： 昨今の資源?環境問題やエネルギー情勢を背景に，卓越した機能だけでなく，地球上に豊富に存在する元素により構成され，安価で高い環境調和性を示す新材料が望まれている．社会に役立つ「材料」へと昇華できる新物質を見いだすためには，的確に設計?探索の指針を立てることが重要であることは言うまでもない．そして次の関門が，いかに広い探索空間をカバーするか，その中からどのように有望な物質を絞り込むかである．最近では計算科学の進展とスーパーコンピュータの演算能力の向上により，第一原理計算等の計算科学手法を用いることで物質の安定性や特性を高精度かつ網羅的に予測できるようになってきた．これにデータ科学手法，更にはコンビナトリアル合成?評価等を連携させることで，新物質?新材料の開発を加速し，同時に膨大なデータの解析から設計?探索指針を得ようとする試みが世界各国で盛んになっている．いわゆる「マテリアルズ?インフォマティクス」によるアプローチである．
关键词： surfaces,point defects,interfaces,materials exploration,semiconductors,first-principles calculations
更新于2025-09-09 09:28:46