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Hydrothermal synthesis and photocatalytic properties of CuGaO2/ZnO hexagonal platelet hybrids
摘要： Delafossite CuGaO2 as a p-type semiconductor is classified as a wide band-gap semiconductor owing to direct transitions on the high energy side. Solid state reaction and sol-gel synthesis are applicable as traditional methods for synthesizing delafossite CuGaO2. However, both synthesis methods require high temperatures, and the sol-gel method additionally requires a nitrogen gas atmosphere. In this study, hexagonal-platelet CuGaO2 is synthesized using a hydrothermal method, which can also be adapted to the synthesis of the CuGaO2/ZnO hybrids. As a result, it was found that the surface of platelet CuGaO2 particles could be used to create hybrids with n-type ZnO semiconductors. This paper also presents the optical band-gap energy and photocatalytic properties of hexagonal-platelet CuGaO2 and CuGaO2/ZnO hybrids.
关键词： photocatalytic properties,p-type semiconductor,Hydrothermal synthesis,optical bandgap,hexagonal platelet hybrid
更新于2025-09-23 15:22:29
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Polyacrylamide gel synthesis and photocatalytic performance of PbBiO2Br nanosheets
摘要： We designed and fabricated novel PbBiO2Br nanosheets via Polyacrylamide gel method. XRD, XPS, SEM, TEM and UV-vis absorption spectra were used to investigate the crystal microstructure, morphology, band-gap and optical properties of the as-prepared PbBiO2Br nanosheets. The photocatalytic performance and stability of PbBiO2Br nanosheets were evaluated by removing methylene blue (MB) aqueous solution (20 mg/L) under visible-light irradiation. Results showed that the PbBiO2Br was brick-like nanosheets with an average side size of about 80 nm and the absorption edge at about 500 nm, and exhibited an excellent photocatalytic performance under visible light irradiation. Moreover, the repeated cycle experimental results demonstrated that the PbBiO2Br nanosheets had a good chemical stability. Finally, the possible photocatalytic mechanism was proposed and discussed.
关键词： Semiconductor,PbBiO2Br,Polymers,Polyacrylamide gel,Photocatalysis
更新于2025-09-23 15:22:29
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Mixing Thermodynamics and Photocatalytic Properties of GaP-ZnS solid solutions
摘要： Preparation of solid solutions represents an effective means to improve the photocatalytic properties of semiconductor-based materials. Nevertheless, the effects of site-occupancy disorder on the functional properties of materials are difficult to predict and consequently many experimental trials may be required before achieving enhanced photocatalytic activity. Here, first-principles methods are employed to estimate the mixing free energy and the structural and electronic properties of (GaP)x(ZnS)1?x solid solutions. The method relies on a multi-configurational supercell approach that takes into account the configurational and vibrational contributions to the free energy. Phase competition among the zinc-blende and wurtzite polymorphs is also considered. Overall excellent agreement with the available experimental data is demonstrated, namely: 1) zinc-blende is energetically most favorable, 2) the solid solution energy band gap lies within the 2–3 eV range, and 3) the energy band gap of the solid solution is direct for compositions x ≤ 75%. It is found that at ambient conditions, (GaP)x(ZnS)1?x solid solutions with x ≈ 25%, 50% and 75% render promising hydrogen evolution photocatalysts for water splitting under visible light, owing to their favorable energy band gaps and band levels relative to vacuum.
关键词： multiconfigurational supercell approach,semiconductor solid solutions,density functional theory calculations,photocatalytic materials
更新于2025-09-23 15:22:29
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Dependence on hydrostatic pressure in two-dimensional triangular photonic crystals
摘要： The plane wave expansion method is used to calculate photonic band structures for transverse electric (TE) polarization, in a two-dimensional (2D) photonic crystal with a hexagonal lattice composed air holes with triangular cross sections embedded in a semiconductor (GaAs) background. This study focuses on the dependence of the GaAs dielectric constant on pressure and temperature. The air holes are isosceles triangles with fixed areas. We found that the width of the photonic band gap increases, when the internal angle of the triangle and the angle of rotation in the unit cell are increased at constant hydrostatic pressure values. The width of the photonic band gap remains unchanged when the hydrostatic pressure is increased at fixed internal and rotation angle values. In addition, when considering an H1 defect in the crystal, using the supercell technique, we find that the number of defective modes within the photonic band gap increases with the triangle rotation in the unit cell.
关键词： plane wave expansion method,hydrostatic pressure,defect mode,Photonic crystal,semiconductor
更新于2025-09-23 15:22:29
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Analysis of current transport mechanisms in sol-gel grown Si/ZnO heterojunction diodes in high temperature environment
摘要： This paper analyzes the electrical parameters of Si/ZnO heterojunction diodes in the wide temperature range, i.e. from room temperature (298 K) to 573 K to study the electrical performance of the diode in very high temperature environment. In this work, sol-gel derived nanostructured ZnO thin film was deposited directly on p-Si substrate using spin coating technique. Electrical parameters, such as rectification ratio, reverse saturation current, ideality factor, barrier height, series resistance and activation energy are derived from current-voltage characteristics of the device, measured using semiconductor parameter analyzer in the temperature range of 298 K–573 K for bias voltage of ± 5 V. The ideality factor, barrier height and series resistance is derived as 2.66, 0.789 eV and 3554 Ω respectively at 298 K, whereas at 573 K these are modified as 1.58, 1.15 eV and 801 Ω respectively. The above-mentioned results indicate the presence of spatial barrier height inhomogeneities (BHI) in high temperature environment. Hence, we have included the Gaussian distribution of spatial BHI in our analysis to calculate the effective Richardson constant (RC). Before inclusion of spatial BHI, RC was 4.026 × 10^{-6} Acm^{-2}K^{-2}. However, after inclusion of spatial BHI, RC is modified to 29.14 Acm^{-2}K^{-2}, which is nearer to the theoretical value (32 Acm^{-2}K^{-2}). Therefore, this study indicates that our as-fabricated Si/ZnO heterojunction diodes can sustain their electrical behaviour in very high temperature environment also and they are suitable for high temperature electronic and optoelectronic application.
关键词： Current-voltage characteristics,Richardson constant,Trap-assisted tunneling,Spatial barrier inhomogeneities,Heterojunction diode,Semiconductor thin film
更新于2025-09-23 15:22:29
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Model To Determine a Distinct Rate Constant for Carrier Multiplication from Experiments
摘要： Carrier multiplication (CM) is the process in which multiple electron?hole pairs are created upon absorption of a single photon in a semiconductor. CM by an initially hot charge carrier occurs in competition with cooling by phonon emission, with the respective rates determining the CM e?ciency. Up until now, CM rates have only been calculated theoretically. We show for the ?rst time how to extract a distinct CM rate constant from experimental data of the relaxation time of hot charge carriers and the yield of CM. We illustrate this method for PbSe quantum dots. Additionally, we provide a simpli?ed method using an estimated energy loss rate to estimate the CM rate constant just above the onset of CM, when detailed experimental data of the relaxation time is missing.
关键词： carrier multiplication,quantum yield,quantum dots,semiconductor,electron?hole pairs
更新于2025-09-23 15:22:29
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All-optical regenerative technique for width-tunable ultra-wideband signal generation
摘要： We demonstrate all-optical generation of width-tunable mono-cycle pulses for ultra-wideband communication. It has been shown that the width of the mono-cycle pulses can be tuned dynamically by simply varying the power of the optical signal. We also investigate the regenerative property of the nonlinear medium-based technique for the generation of mono-cycle pulses. For the purpose of comparison, ultra-wideband mono-cycle pulses are also generated through the optical delay line-based technique. It has been demonstrated through numerical simulations that the nonlinear medium-based technique is highly resilient to amplified spontaneous emission noise that is induced over the optical signal. Furthermore, we have shown that the highly nonlinear fiber-based nonlinear medium performs better than the semiconductor optical amplifier-based medium. Bit error rate measurements are taken for different values of optical signal-to-noise ratios in order to elaborate our work.
关键词： Gaussian mono-cycle pulses,Ultra-wideband over fiber,Semiconductor optical amplifier,Pulse width tuning,Highly nonlinear fiber
更新于2025-09-23 15:22:29
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N-Type Semiconducting Behavior of Copper Octafluorophthalocyanine in an Organic Field-Effect Transistor
摘要： Based on the crystal structure analysis, the overlap integral between the frontier molecular orbitals of adjacent F8CuPcs in the one-dimensional chain is estimated: the overlap integral between the lowest unoccupied molecular orbitals is 5.4 × 10?3, which is larger than that in a typical n-type semiconducing material F16CuPc (2.1 × 10?3), whereas that between the highest occupied molecular orbitals is 2.9 × 10?4. Contrary to previous studies in air, we found that an organic field-effect transistor (OFET) composed of F8CuPc essentially shows clear n-type semiconducting behavior in vacuum.
关键词： n-type semiconductor,OFET,copper octafluorophthalocyanine,organic semiconductor
更新于2025-09-23 15:21:21
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Nonlinear bifurcation diagrams of the current states of microcavity exciton-polaritons in the lattice
摘要： We study nonequilibrium properties of exciton-polaritons in an incoherently driven semiconductor microcavity with an embedded weak-contrast periodic lattice. Within the framework of mean-field theory, we describe nonlinear eigenstates of coherent exciton polaritons having the structure of Bloch waves and identify nonlinear current states at the boundaries of Brillouin zone. We demonstrate a profound modification of the eigenfrequency-momenta bifurcation diagrams of the condensate evoked by exciton-exciton interactions. The discussed phenomenon occurs for the states possessing high degree of symmetry, i.e. in particular, for the states lying at the centre or at the boundary of Brillouin zone.
关键词： exciton-polaritons,semiconductor microcavity,Bloch waves,nonlinear bifurcation,Brillouin zone
更新于2025-09-23 15:21:21
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Digital pulse timing with semiconductor gamma-ray detectors using a wavelet transform technique
摘要： Obtaining precise timing information from semiconductor gamma-ray detectors is of great interest for a variety of applications such as high-resolution positron emission tomography. However, pulse timing with these detectors through the common constant-fraction discrimination (CFD) method is strongly affected by the time-walk error that results from the inherent variations in the shape of the detectors’ pulses. This paper reports on the use of the wavelet transform for minimizing the time-walk error in digital CFD pulse timing with semiconductor gamma-ray detectors. The details of the method are described, and the experimental results with a 1 mm thick CdTe detector are shown. It is demonstrated that, by using the Haar wavelet transform of the digitized preampli?er pulses, the original tailed time spectrum of the detector with a time resolution of 8.22 ± 0.12 ns at full-width at half-maximum (FWHM) in the energy range of 300-550 keV improves to a symmetric time spectrum with a time resolution of 3.39 ± 0.02 ns (FWHM).
关键词： wavelet transform,time-walk error,CdTe detector,digital pulse timing,semiconductor gamma-ray detectors
更新于2025-09-23 15:21:21