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This article investigated the effect of geometric structural parameters on flow patterns and pressure drops and gas–liquid mixing effects of gas–liquid mixing devices. The computational fluid dynamics software FLUENT was used to calculate the airflow inside the mixer of a compressed air–foam gas–liquid mixing device with different cone angles, foam flow rates, air inlet inclination angles, and pipeline diameters. The results obtained are the pressure distribution, the liquid volume fraction, and the liquid phase streamlines in the mixing device. The numerical simulation results showed that for a gas–liquid mixing device, the optimal inlet inclination angle was 60°–70°, and the mixing effect of an equal diameter mixer was better than that of a variable diameter mixer, but it would reduce the mixing efficiency of the air and foam. The optimal pipeline diameter of the conveying pipeline was 190 mm, and the optimal cone angle of the mixing device was 55°. [ABSTRACT FROM AUTHOR]

Wide bandgap β-Ga2O3 is an ideal candidate material with broad application prospects for power electronic components in the future. Aiming at the application requirements of β-Ga2O3 in space photoelectric devices, this work studies the influence of 40 MeV Si ion irradiation on the microstructure and optical properties of β-Ga2O3 epi-wafers. Raman spectroscopy analysis confirms that Si ion irradiation destroys the symmetric stretching mode of tetrahedral–octahedral chains in β-Ga2O3 epi-wafers, and the obtained experimental evidence of irradiation leads to the enhanced defect density of VO and VGa–VO from x-ray photoelectron spectroscopy. Combined with first-principles calculations, we conclude that most configurations of VO and VGa–VO are likely non-radiative, leading to quenching of experimental photoluminescence intensity. Unraveling optical degradation mechanism and predicting the optical application of β-Ga2O3 devices in the space environment by combining ground irradiation experiments with first-principles calculations still be one of the focuses of research in the future. [ABSTRACT FROM AUTHOR]

Indium phosphide is widely used in electronics and photovoltaic devices due to its high electro-optical conversion efficiency, high electron mobility, and good radiation resistance. Defects are the main limitation for the performance of InP devices. In this work, based on hybrid functional with finite size correction, electronic properties of intrinsic and H-related defects have been investigated in InP. We found that PIn defect is the most stable intrinsic defect with the lowest formation energy. Defect signals detected experimentally are defined by our calculated results. Experimentally observed electron traps with the energy level of EC −0.66 eV and EC −0.68 eV are ascribed to the transition level ɛ(−1/−2) and ɛ(−2/−3) of In vacancies. The hydrogenated vacancies in InP have been systematically reported in the present work. Formation energies of H-related defects indicate that hydrogen atoms prefer to bind to In vacancy than P vacancy. The formation energy of In vacancy decreases with the addition of H, while that of P vacancy increases. For hydrogenated In vacancies, it captures fewer electrons than bare In vacancies when the Fermi level is close to CBM. Especially for the VIn −3H structure, it is 0 charge state in all Fermi levels so that it will not tend to capture electron or hole. Our work is helpful to explain experimental phenomena and radiation-induced damages and improve the performance of InP devices. [ABSTRACT FROM AUTHOR]

Two-dimensional molybdenum disulfide (2D MoS2) has great application prospects in the field of optoelectronic devices. Defect engineering is an effective way to regulate the electronic and optical properties of 2D MoS2. However, defect controlling on 2D materials remains a major challenge. Fluorine, as the most electronegative element, may cause many interesting phenomena after doping in 2D materials. So far, there have been no reports on the effect of fluoride ion (F− ion) irradiation on 2D material properties. In this paper, the monolayer MoS2 (ML-MoS2) synthesized by the chemical vapor deposition method was taken as the research object, and defects with controllable densities were produced by 30 keV F− ion irradiation, in which the defects were dominated by S vacancies. Based on Raman, photoluminescence, and x-ray photoelectron spectroscopy, it is shown that the ion irradiation-induced defects significantly affect the optoelectronic properties of MoS2. We also observed the p-doping of ML-MoS2, which is attributed to the introduction of F− ions and the electron transfer from MoS2 to O2 at defect adsorption sites. This study reveals that 2D materials could be effectively doped or compensated using irradiation technology, potentially fabricating novel 2D electrical devices through defect engineering. [ABSTRACT FROM AUTHOR]

Uniaxial strain has been widely used as a powerful tool for investigating and controlling the properties of quantum materials. However, existing strain techniques have so far mostly been limited to use with bulk crystals. Although recent progress has been made in extending the application of strain to two-dimensional van der Waals (vdW) heterostructures, these techniques have been limited to optical characterization and extremely simple electrical device geometries. Here, we report a piezoelectric-based in situ uniaxial strain technique enabling simultaneous electrical transport and optical spectroscopy characterization of dual-gated vdW heterostructure devices. Critically, our technique remains compatible with vdW heterostructure devices of arbitrary complexity fabricated on conventional silicon/silicon dioxide wafer substrates. We demonstrate a large and continuously tunable strain of up to − 0.15% at millikelvin temperatures, with larger strain values also likely achievable. We quantify the strain transmission from the silicon wafer to the vdW heterostructure, and further demonstrate the ability of strain to modify the electronic properties of twisted bilayer graphene. Our technique provides a highly versatile new method for exploring the effect of uniaxial strain on both the electrical and optical properties of vdW heterostructures and can be easily extended to include additional characterization techniques. [ABSTRACT FROM AUTHOR]

Electron traps in AlGaN/GaN high electron mobility transistors were studied by combining theoretical and experimental methods. Energy levels about EC-0.9 eV due to irradiation are identified by deep-level transient spectroscopy (DLTS). Two electron traps, H1 (EC-0.63 eV) and H2 (EC-0.9 eV), were observed in the DLTS spectra. H1 was produced in device or material manufacturing, and H2 was caused by displacement damage. First, we reported that the signal peak of H2 can contribute from three defects labeled H2-1, H2-2, and H2-3 with energies EC-0.77 eV, EC-0.9 eV, and EC-0.98 eV, respectively. According to defect migration temperature and first principles calculation results, it is found that different configurations of di-nitrogen vacancy structures are the source of EC-0.77 eV and EC-0.9 eV signals. The defect of EC-0.98 eV is more stable at high temperatures, which may be related to gallium vacancy. [ABSTRACT FROM AUTHOR]

The advancement of acoustic metamaterials enables the highly efficient absorption of low-frequency noise with a subwavelength structure thickness, but the complexity of these structures often hinders their large-scale practical applications. Here, we propose a straightforward and compact acoustic metamaterial structure composed of Helmholtz resonators with side slits (HRSS) for low-frequency noise absorption. The introduction of side slits not only simplifies the overall structure but also allows for easy adjustment of acoustic characteristics. By adjusting the depth of the resonator within the slit across 25 distinct units, an absorption coefficient above 0.8 is realized from 470 to 930 Hz. This work demonstrates the extensive low-frequency sound absorption capability of HRSS, providing valuable insights into the design of future practical acoustic materials. [ABSTRACT FROM AUTHOR]

Transition metal dichalcogenides (TMDs) are regarded as a possible material platform for quantum information science and related device applications. In TMD monolayers, the dephasing time and inhomogeneity are crucial parameters for any quantum information application. In TMD heterostructures, coupling strength and interlayer exciton lifetimes are also parameters of interest. However, many demonstrations in TMDs can only be realized at specific spots on the sample, presenting a challenge to the scalability of these applications. Here, using multi-dimensional coherent imaging spectroscopy, we shed light on the underlying physics—including dephasing, inhomogeneity, and strain—for a MoSe2 monolayer and identify both promising and unfavorable areas for quantum information applications. We, furthermore, apply the same technique to a MoSe2/WSe2 heterostructure. Despite the notable presence of strain and dielectric environment changes, coherent and incoherent coupling and interlayer exciton lifetimes are mostly robust across the sample. This uniformity is despite a significantly inhomogeneous interlayer exciton photoluminescence distribution that suggests a bad sample for device applications. This robustness strengthens the case for TMDs as a next-generation material platform in quantum information science and beyond. [ABSTRACT FROM AUTHOR]

In this Letter, a bilayer elastic C6v structure is proposed and used to precisely manipulate two topological nontrivial valley pseudo-spin states. According to the theoretical simulation results, the two elastic pseudo-spin states have opposite valley polarizations along propagation directions. Owing to the interlayer polarization and mixing effects of the elastic valley pseudo-spin states in the bilayer elastic C6v structure, the transport and prohibition of elastic valley pseudo-spin states and even the tunneling between layers are flexibly manipulated. The transmission efficiency of elastic valley pseudo-spin states across layers reaches 93%, which has also been confirmed in experiments by the laser ultrasonic method. The in-depth exploration of valley pseudo-spin states with layer indices further expands and enriches the research of valley pseudo-spin states in the elastic environment and lays the foundation for the further design of elastic topological devices. [ABSTRACT FROM AUTHOR]

Early detection and monitoring of heavy load induced plastic deformation in the structure is crucial for timely intervention before cracking occurs and the material completely fails. Ultrasound can be used for detecting plastic deformation provided the mechanical modulus, which can be probed via changes in velocities. This work presents a measurement scheme that makes use of optically detected, laser-induced surface acoustic waves (SAWs) for remote, real-time, online monitoring of the wave velocity during the elastic–plastic transition occurring in an aluminum plate undergoing a uniaxial tensile test and a dynamic fatigue test. Monochromatic SAWs were photoacoustically generated in a wavelength-controlled way through a transient thermal grating based laser ultrasonics excitation scheme. The SAWs were detected by a home-built photorefractive interferometer. The results reveal both regions of acceleration and slowing down, indicating that the material first stiffens and then starts to form microcracks that make it behave effectively softer for propagating SAWs. [ABSTRACT FROM AUTHOR]