- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Effect of beam wobbling on laser welding of aluminum and magnesium alloy with nickel interlayer
摘要： The influence of conventional laser keyhole welding and beam wobbling was evaluated at two weld travel speeds and power settings. Fracture in linear lap welds would occur during specimen preparation due to the presence of Al-rich brittle fusion zone, unless one utilizes a circular laser wobbling path (at 1000 Hz). Wobbling provided better integrity due to the presence of a Mg-rich ductile fusion zone and a larger bonded width. It can be concluded that laser beam wobbling enhances joint quality by widening the joint area and mitigating formation of brittle secondary phases at the joint fusion zone.
关键词： Aluminum,Magnesium,Interlayer,Laser welding,Beam wobbling,Microstructure
更新于2025-11-28 14:24:20
-
2D Schottky Junction between Graphene Oxide and Transition-Metal Dichalcogenides: Photoresponsive Properties and Electrocatalytic Performance
摘要： 2D graphene is conductor and not a semiconductor. 2D transition—metal dichalcogenides (TMD) is a semiconductor and not a conductor. Preparing 2D composite material that simultaneously possesses both advantages of graphene and TMD has proven to be challenging. In this work, both 2D-WS2/2D-GO and 2D-MoS2/2D-GO composites with few layer thickness are synthesized. The electronic structure indicates a high content of Mo4+ 3d5/2 and W4+4f7/2 with lower binding energy in the 2D composite, which is ascribed to partial loss of surface sulfur atoms in 2D composites and the newly formed heteroatomic bond of CWS and CMoS. The Schottky junction between 2D-GO and 2D-TMD (2D G-T junction) is established and exhibits obvious photoelectric responses. Superior electrocatalytic properties of the two 2D-composites are attributable to the 2D Schottky Junction between 2D-TMDs and 2D-GO. Interlayer electronic coupling in 2D Schottky Junction (2D G-T junction) activates inert sites on the 2D surface of 2D-TMDs or GO. The power conversion efficiency of dye-sensitized solar cells (DSCs) based on 2D-WS2/2D-GO is 9.54% under standard solar illumination intensity (AM1.5, 100 mW cm?2). The value is one of the highest reported efficiencies for DSCs based on Pt-free counter electrodes. Finally, 2D-WS2/2D-GO composites exhibit excellent stability as counter electrode of DSCs.
关键词： photoresponse,interlayer electronic coupling,2D,electrocatalyst,graphene,transition-metal dichalcogenides,Schottky junction
更新于2025-09-23 15:23:52
-
Thickness-dependent bandgap of transition metal dichalcogenides dominated by interlayer van der Waals interaction
摘要： Based on a bandgap thermodynamic approach, the thickness-dependent bandgap of two-dimensional transition metal dichalcogenides is modeled without any adjustable parameter. An efficient expansion in bandgap upon lowering the thickness is predicted. The thickness-dependence of bandgap is believed originated from the interlayer van der Waals (vdW) interaction, while the surface effect is characterized by the difference in atomic thermal vibration between the surface and the interior. Due to the suppression role of the interlayer vdW interaction on the thermal vibration of interior chalcogen atoms, the surface effect is variable, which changes from monotonic increase for sulfides to decrease for tellurides. The role of the interlayer vdW interaction depends on the polarity of metal-chalcogen bonds. The model predictions agree with available experiment and simulation results.
关键词： Surface effect,Thickness-dependence,Bandgap,Interlayer van der Waals interaction,Thermodynamics
更新于2025-09-23 15:23:52
-
Short-Period Multilayer X-ray Mirrors for “Water” and “Carbon Windows” Wavelengths
摘要： This review paper summarizes and provides an overview of our recent studies related to two types of short-period multilayer X-ray mirrors, W/B4C and Co/C. It deals with the experimental observation of the layer intermixing effects and how they affect the X-ray mirror's optical performance. The paper presents also some examples of using the fabricated X-ray mirrors in focusing and imaging experiments at the working wavelengths 2.48 nm and 4.47 nm.
关键词： Thin Films,Interlayer Interaction,Metal-Carbon Compositions,Short-Period Multilayer Structures,X-ray Multilayer Mirrors,X-ray Optics
更新于2025-09-23 15:23:52
-
Probing interlayer excitons in a vertical van der Waals p-n junction using scanning probe microscopy technique
摘要： Two dimensional (2D) semiconductors feature exceptional optoelectronic properties controlled by strong confinement in one dimension. In this contribution, we studied interlayer excitons in a vertical p-n junction made of bilayer n-type MoS2 and few layers of p-type GaSe using current sensing atomic force microscopy (CSAFM). The p-n interface is prepared by mechanical exfoliation onto highly ordered pyrolytic graphite (HOPG). Thus the heterostructure creates an ideal layered system with HOPG serving as the bottom contact for the electrical characterization. Home-built Au tips are used as the top contact in CSAFM mode. During the basic diode characterization, the p-n interface shows strong rectification behavior with a rectification ratio of 104 at ±1 V. The I-V characteristics reveal pronounced photovoltaic effects with a fill factor of 0.55 by an excitation below the band gap. This phenomenon can be explained by the dissociation of interlayer excitons at the interface. The possibility of the interlayer exciton formation is indicated by density functional theory (DFT) calculations on this heterostructure: the valence band of GaSe and the conduction band of MoS2 contribute to an interface-specific state at an energy of about 1.5 eV. The proof of excitonic transitions to that state is provided by photoluminescence measurements at the p-n interface. Finally, photocurrent mapping at the interface under an excitation wavelength of 785 nm provides evidence of efficient extraction of such excitons. Our results demonstrate a pathway towards a two dimensional device for future optoelectronics and light harvesting assisted by interlayer excitons in a van der Waals heterostructure.
关键词： optoelectronics,van der Waals heterojunction,GaSe,density functional theory,MoS2,interlayer exciton,p-n junction
更新于2025-09-23 15:23:52
-
An Electrical Analysis of a Metal-Interlayer-Semiconductor Structure on High-Quality Si <sub/> 1? <i>x</i> </sub> Ge <sub/><i>x</i> </sub> Films for Non-Alloyed Ohmic Contact
摘要： In this paper, we have investigated the effect of a metal-interlayer-semiconductor (MIS) structure on intrinsic silicon-germanium (SiGe) film which is epitaxially grown by ultra-high vacuum chemical vapor deposition (UHV-CVD). Ultra-thin dielectric materials can alleviate Fermi-level pinning at the metal/Si1?xGex contact region by preventing penetration into the Si1?xGex of metal-induced gap states (MIGS) from the metal surface. The electrical properties which are the back-to-back current density and specific contact resistivity of the Ti/TiO2/Si1?xGex structure improve at the TiO2 interlayer thickness of 0.5 nm for all kinds of Si1?xGex film with various levels of germanium (Ge) concentration. The case of Si0.7Ge0.3 film, the specific contact resistivity of a Ti/TiO2(0.5 nm)/Si0.7Ge0.3 structure is reduced 80-fold compared to that of a Ti/Si0.7Ge0.3 structure. The effect of the MIS structure has been well demonstrated on Si1?xGex film, and as a result this structure is suggested as a novel source/drain (S/D) contact scheme for advanced Si1?xGex complementary metal-oxide-semiconductor (CMOS) technology.
关键词： Epitaxial Growth,Metal-Interlayer-Semiconductor,Source/Drain Contact,Silicon-Germanium,Fermi-Level Pinning,Specific Contact Resistivity
更新于2025-09-23 15:22:29
-
Characteristics of Al<sub>2</sub>O<sub>3</sub>/native oxide/n-GaN capacitors by post-metallization annealing
摘要： This work investigated characteristics of Al2O3/native oxide/n-GaN MOS capacitors by post-metallization annealing (PMA). A native oxide interlayer which composed of ε- and γ-Ga2O3 phases (Native oxide) and the reduced amount of one (Reduced) on n-GaN were prepared by cleaning only a sulfuric acid peroxide mixture (SPM) and both SPM and buffered hydrofluoric acid, respectively. The effect of trimethylaluminum precursor on removal of a native oxide layer was not observed during Al2O3 deposition using atomic layer deposition. An as-grown capacitor (Native oxide) exhibited a small flatband voltage (Vfb) hysteresis of ~30 mV and a large frequency dispersion, suggesting that the initial growth of the Al2O3 resulted in the formation of electrical defects on the GaN surface. Both the Vfb hysteresis and frequency dispersion were drastically improved by PMA of the device at 300°C. The positive fixed charge values (QIL) estimated from the relationships between capacitance equivalent thickness and Vfb were +6.1 × 10^12 and +0.4 - 1.0 × 10^12 cm^-2 for as-grown and PMA-processed capacitors in the PMA temperature range of 300 - 600°C, respectively. The interface state density (Dit) determined using a conductance method was also significantly reduced (by an order of magnitude) after PMA processing at 300°C. These trends in the QIL and Dit data were observed in both the Native oxide and Reduced capacitors, indicating that this interlayer does not greatly affect fixed charge generation at the Al2O3/native oxide and Al2O3/modefied native oxide interfaces. As a result, two types of treatments result in insignificant difference in the electrical properties of the capacitors.
关键词： flatband voltage,GaN,Al2O3 dielectric,ALD,fixed charge,native oxide interlayer
更新于2025-09-23 15:22:29
-
Nature of the excited states of layered systems and molecular excimers: Exciplex states and their dependence on structure
摘要： Weakly bound systems, like noble-gas dimers or two-dimensional layered materials (graphite, hexagonal boron nitride, or transition-metal dichalcogenides), exhibit excited electronic states of a particular nature. These so-called exciplex states combine on-site (or intralayer) and charge-transfer (or interlayer) configurations in a well-balanced way. We show by ab initio many-body perturbation theory that the energy and composition of the exciplex states depend sensitively on the bond length or interlayer distance of the material. When the constituents approach each other, the charge-transfer contribution increases and the excitation is redshifted to lower energy. If the system is excited into the exciplex state, then a covalent-like bond results. In consequence, noble-gas dimers form excimer complexes, while layered materials exhibit interlayer contraction.
关键词： charge-transfer excitations,many-body perturbation theory,interlayer contraction,exciplex states,layered systems
更新于2025-09-23 15:22:29
-
Improvement of the Laser-Welded Lap Joint of Dissimilar Mg Alloy and Cu by Incorporation of a Zn Interlayer
摘要： During pulsed laser welding of AZ 31B magnesium (Mg) alloy and T2 pure copper (Cu), Cu2Mg and Mg2Cu are generated, but the bonding ability of the two compounds is usually weak, resulting in low strength. In order to improve the joint of two dissimilar metals, a zinc interlayer was inserted between the Mg alloy and Cu, and the effects of the thickness of the Zn interlayer on the microstructure and properties of the joint were studied. The fused zone consisted of Cu2Mg and MgZn, and, according to first-principles calculation, in the same energy range, the area enclosed by the density of the state curve of MgZn was larger than that of Cu2Mg. Hence, the bonding ability of MgZn was better than that of Cu2Mg, and MgZn improved the strength of the welded joint. The most advantageous thickness of the Zn interlayer was 0.1 mm, and the shear strength was 48.15 MPa that was 161% higher than that of the directly welded Mg/Cu joint.
关键词： interlayer,first-principles calculation,magnesium alloy,laser welding,dissimilar metals
更新于2025-09-23 15:21:01
-
Organic Solar Cells Efficiency Enhanced by Perylene Mono-Imide Phosphorus Salt Cathode Interfacial Layer
摘要： The composite high-performance electrode is very important for excellent photoelectric device. Interfacial modification is the dominating method to optimize electrode properties. Two easy synthesized perylene-monoimide (PMI) derived organic phosphonium bromide salts were found interestingly valuable when they were applied as cathode interlayers (CIL) in bulk heterojunction (BHJ) organic solar cells (OSCs). Using the PBDB-T:ITIC blend as bulk-hererojunction active layer in inverted device structure, the power conversion efficiency (PCE) was greatly improvement from 9.49% of the referenced device which is without phosphonium CIL to PCE 10.42% with PMI-triphenyl-phosphonium bromide (PMI-TPP) and PCE 9.87% with PMI- trimethoxylphenylphosphonium bromide (PMI-TMOPP) as CIL. Moreover, the two organic phosphonium bromide salts were also investigated by traditional device structure, the PCE was of 4.21% for bare aluminium cathode referenced device contrasted to a moderate increased PCE of 5.18% with PMI-TPP CIL or PCE of 5.05% with PMI-TMOPP CIL. Therefore, organic phosphonium bromide salt PMI-TPP is a promising candidate of CIL material in OSCs.
关键词： cathode interlayer,organophosphorus,energy conversion,electron transfer,solar cell
更新于2025-09-23 15:21:01