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Effects of two-photon absorption on pseudo-random bit sequence operating at high speed
摘要： The effect of two-photon absorption (TPA) on all-optical logic operation in quantum-dot semiconductor optical amplifier (QD-SOA) has been carried out. We model the rate equation with the TPA effect for the logic XOR gate, AND gate, and, for pseudo-random bit sequence (PRBS) generation. The simulated results indicate that the TPA induced pumping increases the output Q-factor (quality). The results show that the quality of the output depends on the input pulse width and the speed of operation. The PRBS system can operate at 250 and 320 Gb/s but an increase in pulse width decreases the output Q-factor.
关键词： quantum-dot semiconductor optical amplifier,pseudorandom bit sequence,optical logic,Q factor,Two-photon absorption
更新于2025-09-23 15:23:52
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Mechanically-controllable strong 2D ferroelectricity and optical properties of semiconducting BiN monolayer
摘要： Structural, electronic, ferroelectric, and optical properties of two-dimensional (2D) BiN monolayer material with phosphorene-like structure are studied in terms of the density functional theory and modern Berry phase method of ferroelectric calculation. Both phonon spectra, molecular dynamics simulations, and total energy comparison indicate that the BiN monolayer is a stable 2D ferroelectric with polarization as large as 580 pC/m, with ferroelectric polarization being sustainable up to 500 K. Further study shows that the polarization in the BiN monolayer can be easily switched from [100] to [010] direction over the bridging saddle phase by applying a tensile [010] stress of 2.54 N/m or compressive [100] stress of -1.18 N/m. This phase transition makes its lattice constants vary in a large range compared to other non-ferroelectric 2D materials. Moreover, through applying uniaxial tensile stress parallel to the polarization, one can fix the polarization and change the semiconductor energy gap, from direct to indirect one. The optical properties feature a very strong anisotropy in reflectivity below the photon energy of 4 eV. All these significant ferroelectric, mechanical, electronic, and optical properties make us believe that the 2D BiN monolayer can be used to make stretchable electronic devices and optical applications.
关键词： 2D material,optical property,monolayer,mechanical manipulation,2D ferroelectricity,2D semiconductor
更新于2025-09-23 15:23:52
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A review on photoelectrochemical hydrogen production systems: Challenges and future directions
摘要： Water photolysis is a fundamental concept in which solar-driven water splitting is utilized to generate renewable hydrogen fuel using semiconductor-based electrochemical systems. The engineering design principles for each system configuration, including single, dual/tandem photoelectrodes, tandem photoelectrochemical-photovoltaic, and multi-junction designs are reviewed. Modeling and numerical simulation of photoelectrochemical processes based on up-to-date multi-scale analysis are presented and discussed. In addition, the achievements made in semiconductor photoelectrode materials and the rational engineering methods needed to improve the solar to hydrogen efficiency are demonstrated. Furthermore, some key accomplishments in different aspects, such as electron-hole recombination, stability, photocorrosion, energy band gap, and photocurrent density are discussed. Moreover, key points on the challenges, opportunities and future directions towards commercialization of viable photoelectrochemical reactors are discussed.
关键词： Semiconductor materials,Photoelectrochemical process,Hydrogen production,Solar energy
更新于2025-09-23 15:23:52
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TiO2/Schwertmannite nanocomposites as superior co-catalysts in heterogeneous photo-Fenton process
摘要： The heterogeneous photo-Fenton reaction is an effective technique in combating organic contaminants for both soil and water remediation, and extensive studies have focused on enhancing its efficiency and reducing its costs. In this work, we developed novel photo-Fenton catalysts by simply milling commercially available TiO2 (P25) with Schwertmannite (Sh), a natural iron-oxyhydroxysulfate nanomineral. We expect that the photo-generated electrons from TiO2 could continuously migrate to Sh, which then could enhance the separation of electron-hole pairs on TiO2 and accelerate the reduction of Fe(III) to Fe(II) on Sh, leading to high degradation efficiency of the target organic contaminants. SEM and TEM results showed the distribution of TiO2 on Sh surface for the nanocomposites (TiO2/Sh). Under simulated sunlight irradiation, the much higher content of Fe(II) was determined on TiO2/Sh than on Sh via a common method in the iron ore, and the consumption of H2O2 and the production of ?OH were more significant in the TiO2/Sh system than those in the TiO2 and Sh systems. These results well support our hypothesis that the photo-generated electrons could migrate from TiO2 to Sh on the composites, and can also explain the much higher degradation efficiency of Rhodamine B (RhB) in the TiO2/Sh system. Besides, TiO2/Sh had lower Fe dissolution as compared with Sh, and retained high catalytic stability after four repeated cycles. Above merits of the TiO2/Sh composites, in combining with their simple synthesis method and low-cost property, indicated that they should have promising applications as heterogeneous photo-Fenton catalysts.
关键词： Advanced oxidation,Photo-Fenton reaction,Semiconductor,Schwertmannite
更新于2025-09-23 15:23:52
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Synthesis of Inorganic-Organic 2D CdSe Slab-Diamine Quantum Nets
摘要： Porous semiconductors attract great interest due to their unique structural characteristics of high surface area as well as their intrinsic optical and electronic properties. In this study, synthesis of inorganic–organic 2D CdSe slabs-diaminooctane (DAO) porous quantum net structures is demonstrated. It is found that the hybrid 2D CdSe-DAO lamellar structures are disintegrated into porous net structures, maintaining an ultrathin thickness of ≈1 nm in CdSe slabs. Furthermore, the CdSe slabs in quantum nets show the highly shifted excitonic transition in the absorption spectrum, demonstrating their strongly confined electronic structures. The possible formation mechanism of this porous structure is investigated with the control experiments of the synthesis using n-alkyldiamines with various hydrocarbon chain lengths and ligand exchange of DAO with oleylamine. It is suggested that a strong van der Waals interaction among long chain DAO may exert strong tensile stress on the CdSe slabs, eventually disintegrating slabs. The thermal decomposition of CdSe-DAO quantum nets is further studied to form well-defined CdSe nanorods. It is believed that the current CdSe-DAO quantum nets will offer a new type of porous semiconductors nanostructures under a strong quantum-confinement regime, which can be applied to various technological areas of catalysts, electronics, and optoelectronics.
关键词： quantum nets,porous materials,semiconductor nanocrystals,CdSe,2D materials
更新于2025-09-23 15:23:52
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Effect of plasma treatment on adhesion strength and moisture absorption characteristics between epoxy molding compound/silicon chip (EMC/chip) interface
摘要： Reliability of interface between two dissimilar materials becomes an important issue due to increasing demands of high-density integrated circuits. Most of failures of semiconductor package occur at the interface between two dissimilar materials in high temperature reflow process, thus, adhesion strength under high temperature should be investigated. In this study, an adhesion shear test jig was newly devised to measure the adhesion strength of epoxy molding compound/Si chip (EMC/chip) interface at high temperature (200 °C). In order to investigate the effect of plasma treatment on adhesion strength and moisture absorption characteristics, the number of plasma treatments was varied. Also, moisture absorption time was varied to observe the moisture uptake and degradation of adhesion strength with respect to plasma treatment number. Atomic force microscope (AFM) was analyzed to verify the surface roughness of silicon chip, and scanning electron microscopy (SEM) was used to observe cross-sectional fractured morphology after adhesion strength test. From this study, it was found that the plasma treatments affect much the adhesion strength and moisture uptake at the interface between the EMC/Chip interface.
关键词： Semiconductor package,Moisture absorption,Adhesion strength,Plasma treatment
更新于2025-09-23 15:23:52
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Thermal Fluctuations in the Phase Structure of the Excitonic Insulator Charge Density Wave State in the Extended Falicov–Kimball Model
摘要： Excitonic insulator (EI) instability accompanied by a charge density wave (CDW) state in the two-dimensional extended Falicov–Kimball model including electron–phonon interaction is investigated by applying the unrestricted Hartree–Fock approximation. Treating both the Coulomb attraction and the electron–phonon coupling on an equal footing, we have derived a set of self-consistent equations, which allows us to determine both the excitonic insulator order parameter and the lattice displacement. The phase structures show us that both the Coulomb interaction and the electron–phonon coupling act together in establishing the EI-CDW state, which typifies either a phononic-CDW or an excitonic-CDW state depending on the competition of the interactions. At a given low temperature, the EI-CDW state is found between two critical values of the Coulomb interaction. The window of the condensation state grows when increasing the electron–phonon coupling. Depending on the temperature and the Coulomb interaction the Bardeen–Cooper–Schrieffer–Bose–Einstein condensation (BCS–BEC) crossover of the EI-CDW state in the systems has been established. Under the effects of phonons, the BCS–BEC crossover deviates to a larger Coulomb interaction while the semimetal–semiconductor transition in the normal state remains.
关键词： semimetal–semiconductor transition,charge density wave,unrestricted Hartree–Fock approximation,Excitonic condensation
更新于2025-09-23 15:23:52
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Investigation of Structural and Elastic Stability, Electronic, Magnetic, Thermoelectric, Lattice-Dynamical and Thermodynamical Properties of Spin Gapless Semiconducting Heusler Alloy Zr2MnIn Using DFT Approach
摘要： In recent times, spin gapless semiconductors (SGS) have attracted much attention as a promising candidate for spintronics and thermoelectric applications due to their high carrier concentration and good thermoelectric figure of merit. In this paper, we have carried out a systematic theoretical investigation of the structural, elastic, thermal, electronic, magnetic, thermoelectric, lattice dynamical and thermodynamical properties of Zr2MnIn using density functional theory (DFT) based first principle calculations. The band structure calculation shows indirect band gap in a spin down channel and zero band gap in a spin up channel of valence and conduction bands confirming the spin gapless semiconducting nature of Zr2MnIn. The structural and dynamical stability of the antiferromagnetic phase of Zr2MnIn has also been investigated. Magnetization in Zr2MnIn originates due to the d state electrons of Zr atoms, which follows the Slater Pauling rule: Mt = Zt (cid:2) 18. Phonon dispersion curves exhibit real frequency of phonon modes throughout the Brillouin zone, which confirms the dynamical stability of the antiferromagnetic phase of Zr2MnIn. Thermodynamical properties including specific heat and Debye temperature have been calculated using phonon density of states. A higher value of the thermoelectric figure of merit 1.25, predicts that this alloy as good thermoelectric properties with better output efficiency.
关键词： Spin gapless semiconductor (SGS),magnetic moment,structural and elastic stability,thermoelectric and lattice dynamical properties,electronic structure
更新于2025-09-23 15:23:52
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Barrier height modification in Au/Ti/n-GaAs devices with a $$\hbox {HfO}_{2}$$HfO2 interfacial layer formed by atomic layer deposition
摘要： X-ray photoelectron spectroscopy has been carried out to characterize the surface of the hafnia (HfO2) thin films grown on n-GaAs wafer by atomic layer deposition, and the surface morphology of the HfO2 layer on GaAs has been analysed using atomic force microscopy. The barrier height (BH) values of 1.03 and 0.93 eV (300 K) for the Au/Ti/HfO2/n-GaAs structures with 3- and 5-nm HfO2 interfacial layers, respectively, have been obtained from the I–V characteristics of the devices, which are higher than the value of 0.77 eV (300 K) for the Au/Ti/n-GaAs diode fabricated by us. Therefore, it can be said that the HfO2 thin layer at the metal/GaAs interface can also be used for BH modification as a gate insulator in GaAs metal-oxide semiconductor (MOS) capacitors and MOS field-effect transistors. The ideality factor values have been calculated as 1.028 and 2.72 eV at 400 and 60 K; and as 1.04 and 2.58 eV at 400 and 60 K for the metal–insulating layer–semiconductor (MIS) devices with 3- and 5-nm interfacial layers, respectively. The bias-dependent BH values have been calculated for the devices by both Norde’s method and Gaussian distribution (GD) of BHs at each sample temperature. At 320 K, the (cid:2)b(V ) value at 0.70 V for a 3-nm MIS diode is about 1.08 eV from the (cid:2)b(V ) vs. V curve determined by the GD, and about 0.99 eV at 0.58 V for a 5-nm MIS diode. It has been seen that these bias-dependent BH values are in close agreement with those obtained by Norde’s method for the same bias voltage values.
关键词： metal–insulating layer–semiconductor (MIS) device,Barrier height modification and inhomogeneous,bias-dependent barrier height,temperature-dependent MIS diode parameters,atomic layer deposition (ALD)
更新于2025-09-23 15:23:52
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Electric field-induced toughening in GaN piezoelectric semiconductor ceramics
摘要： In this paper, the effect of an applied electric field on fracture toughness of polarized GaN piezoelectric semiconductor ceramics was studied by using experimental and numerical methods. The results show that fracture toughness increases by 22% under a field intensity of 0.83 kV cm?1, and with further increase of the electrical filed, fracture toughness remains unchanged. This is completely different from the fracture characteristics of traditional piezoelectric ceramics that is thought to decrease with an applied electric field. The reason for such a difference is attributed to the redistribution of free electrons. It is expected that this finding will be instructive to the reliability design of piezoelectric semiconductor structures and devices.
关键词： GaN,Electric field,Fracture toughness,Piezoelectric semiconductor ceramics,Toughening
更新于2025-09-23 15:23:52