Electrostatic discharge induced degradation of optical-electrical properties and defect evolution of GaAs-based oxide-confined VCSELs.

GaAs-based oxide-confined vertical-cavity surface-emitting lasers (VCSELs) exhibit relatively low resistance against reliability-related damage. In order to gain a deeper understanding of the degradation and failure mechanism in oxide-confined VCSELs caused by electrostatic discharge (ESD)-induced defect proliferation, we investigated the effects of ESD stress on the degradation of optical-electrical characteristics and the evolution of defects in VCSELs under human body model test condition. The degradation threshold values for forward and reverse ESD pulse amplitudes were estimated to be 200 V and -50 V, respectively. Notably, VCSELs demonstrated greater sensitivity to reverse bias ESD compared to forward bias ESD. Analysis of optical emission and microstructure provided evidence that the device failure is attributed to an increase in ESD current density, leading to the multiplication of dark line defects (DLDs) originating from the edge of the device's oxide aperture. The formation of defects occurred suddenly in discrete events within small regions, rather than progressing gradually and uniformly. These defects propagated and led to damage across the entire active region. We believe that our results would be meaningful for improving the reliability of VCSEL in the future.

Above 20†GHz high frequency operation of mid-infrared doughnut-shaped microcavity quantum cascade lasers.

Microresonator-based high-speed single-mode quantum cascade lasers are ideal candidates for on-chip optical data interconnection and high sensitivity gas sensing in the mid-infrared spectral range. In this paper, we propose a high frequency operation of single-mode doughnut-shaped microcavity quantum cascade laser at ∼4.6 µm. By leveraging compact micro-ring resonators and integrating with grounded coplanar waveguide transmission lines, we have greatly reduced the parasitics originating from both the device and wire bonding. In addition, a selective heat dissipation scheme was introduced to improve the thermal characteristics of the device by semi-insulating InP infill regrowth. The highest continuous wave operating temperature of the device reaches 288 K. A maximum -3 dB bandwidth of 11 GHz and a cut-off frequency exceeding 20 GHz in a microwave rectification technique are obtained. Benefiting from the notch at the short axis of the microcavity resonator, a highly customized far-field profile with an in-plane beam divergence angle of 2.4° is achieved.

Ultraviolet photodetector based on RbCu2I3microwire.

Copper-based halide perovskites have shown great potential in lighting and photodetection due to their excellent photoelectric properties, good stability and lead-free nature. However, as an important piece of copper-based perovskites, the synthesis and application of RbCu2I3have never been reported. Here, we demonstrate the synthesis of high-quality RbCu2I3microwires (MWs) by a fast-cooling hot saturated solution method. The prepared MWs exhibit an orthorhombic structure with a smooth surface. Optical measurements show the RbCu2I3MWs have a sharp ultraviolet absorption edge with 3.63 eV optical band gap and ultra-large stokes shift (300 nm) in photoluminescence. The subsequent photodetector based on a single RbCu2I3MW shows excellent ultraviolet detection performance. Under the 340 nm illumination, the device shows a specific detectivity of 5.0 × 109Jones and a responsivity of 380 mA·W-1. The synthesis method and physical properties of RbCu2I3could be a guide to the future optoelectronic application of the new material.

Controlling the morphology and wavelength of self-assembled coaxial GaAs/Ga(As)Sb/GaAs single quantum-well nanowires.

Antimonide-based ternary III-V nanowires (NWs) provide a tunable bandgap over a wide range, and the GaAsSb material system has prospective applications in the 1.3-1.55 µm spectral range of optical communications. In this paper, GaAs/Ga(As)Sb/GaAs single quantum well (SQW) NWs were grown on Si(111) substrates by molecular beam epitaxy (MBE). In addition, the morphologies and tunable wavelengths of the GaAs/Ga(As)Sb/GaAs SQWs were adjusted by interrupting the Ga droplets and changing the growth temperatures and V/III ratios. The four morphologies of the GaAs/Ga(As)Sb/GaAs SQW NWs were observed by scanning electron microscopy (SEM). The microscale lattice structure related to the incorporation of Sb in GaAs/Ga(As)Sb/GaAs SQWs was studied by Raman spectroscopy. The crystal quality of the GaAs/Ga(As)Sb/GaAs SQW NWs was researched by X-ray diffraction (XRD) and transmission electron microscopy (TEM). In addition, the optical properties of the GaAs/Ga(As)Sb/GaAs SQWs were investigated by photoluminescence (PL) spectroscopy. The PL spectra showed the peak emission wavelength range of ∼818 nm (GaAs) to ∼1628 nm (GaSb) at 10 K. This study provides an approach to enhance the effective control of the morphology, structure and wavelength of quantum well or core-shell NWs.

The response mechanism of microorganisms to the organic carbon-driven formation of black and odorous water.

The formation of black and odorous water is a complex process influenced by various factors such as organic matter and environmental conditions. However, there are limited studies on the role of microorganisms in water and sediment during the blackening and odorization process. In this study, we investigated the characteristics of black and odorous water formation by simulating organic carbon-driven black and odorous water through indoor experiments. The study revealed that the water turned black and odorous when DOC reached 50 mg/L and the microbial community structure in the water changed significantly during this process, with the relative abundance of Desulfobacterota increasing significantly and Desulfovibrio being the main dominant genus in Desulfobacterota. Additionally, we observed a notable decrease in the α-diversity of the microbial community in water and a considerable increase in microbial function of sulfur compounds respiration in water. In contrast, the sediment microbial community changed slightly, and the main functions of the sediment microbial community remained unchanged. The partial least squares path model (PLS-PM) suggested that organic carbon will drive the blackening and odorization process by affecting DO levels and microbial community structure and that the contribution of Desulfobacterota in water to the formation of black and odorous water was higher than that in sediment. Overall, our study provides insights into the characteristics of black and odorous water formation and suggests potential ways to prevent its formation by controlling DOC and inhibiting the growth of Desulfobacterota in water bodies.

Grain size distribution drives microbial communities vertically assemble in nascent lake sediments.

Sediment microbes are crucial for maintaining biogeochemical cycles in aquatic ecosystems, yet the influence of sediment geophysical structure on microbial communities remains unclear. In this study, we collected sediment cores from a nascent reservoir in its initial stage of deposition and utilized the multifractal model to comprehensively characterize the heterogeneity of sediment grain size and pore space. Our results demonstrate that both environmental physiochemistry and microbial community structures varied significantly with depth, with the grain size distribution (GSD) being the key driver of sediment microbial diversity, as revealed by the partial least squares path model (PLS-PM) method. GSD can potentially impact microbial communities and biomass by controlling pore space and organic matter. Overall, this study represents the first attempt to apply soil multifractal models into the integrated description of physical structure in sediment. Our findings provide valuable insights into the vertical distribution of microbial communities.

Effects of electrochemical intervention on the remediation of black-odorous water: insights into microbial community dynamics and functional shifts in sediments.

Black-odorous water is a severe environmental issue that has received continuous attention. The major purpose of the present study was to propose an economical, practical, and pollution-free treatment technology. In this study, the in situ remediation of black-odorous water was conducted by applying different voltages (2.5, 5, and 10 V) to improve oxidation conditions of the surface sediments. The study investigated the effects of voltage intervention on water quality, gas emissions, and microbial community dynamics in surface sediments during the remediation process. The results indicated that the voltage intervention can effectively increase the oxidation-reduction potential (ORP) of the surface sediments and inhibit the emissions of H2S, NH3, and CH4. Moreover, the relative abundances of typical methanogens (Methanosarcina and Methanolobus) and sulfate-reducing bacteria (Desulfovirga) decreased because of the increase in ORP after the voltage treatment. The microbial functions predicted by FAPROTAX also demonstrated the inhibition of methanogenesis and sulfate reduction functions. On the contrary, the total relative abundances of chemoheterotrophic microorganisms (e.g., Dechloromonas, Azospira, Azospirillum, and Pannonibacter) in the surface sediments increased significantly, which led to enhanced biochemical degradability of the black-odorous sediments as well as CO2 emissions.

Activated carbon modified with nano manganese dioxide triggered electron transport pathway changes for boosted anaerobic treatment of dyeing wastewater.

Herein, an expanded granular sludge bed (EGSB) reactor with activated carbon (AC)-nano manganese dioxide (MnO2) added was employed for azo dye wastewater treatment to investigate its effectiveness at decolorizing of azo dyes and removing COD. The results showed that the treatment of azo dye wastewater with the AC-MnO2 modified EGSB reactor gave an 83% average decolorization efficiency, which was more efficient than the pure AC modified EGSB reactor. Moreover, the COD removal and changes in the intermediate products were controlled by AC-MnO2. Additionally, there was a sharp increase in the sludge conductivity, while there was a significant decrease in the coenzyme F420 concentration with long-term operation. Moreover, electrochemical analysis showed that the addition of AC-MnO2 can enhance electron transfer in anaerobic system. The AC-MnO2 can act as redox mediator; in the presence of the Mn4+/Mn2+ cycle, accelerating the electron transfer between the microbial cells and dyes, thereby promoting the decolorization of azo dyes. This caused a decrease in the methanogenic activity. Furthermore, high-throughput sequencing showed that the relative abundances of Pseudomonas and Desulfovibrio were significantly high among the acidogenic bacteria community, while Methanobacterium and Methanosaeta had very low abundances from among the methanogenic archaea community.

Toward Unusual-High Hole Mobility of p-Channel Field-Effect-Transistors.

The relative low hole mobility of p-channel building block device challenges the continued miniaturization of modern electronic chips. Metal-semiconductor junction is always an efficient strategy to control the carrier concentration of channel semiconductor, benefiting the carrier mobility regulation of building block device. In this work, complementary metal oxide semiconductor (CMOS)-compatible metals are selected to deposit on the surface of the important p-channel building block of GaSb nanowire field-effect-transistors (NWFETs), demonstrating the efficient strategy of hole mobility enhancement by metal-semiconductor junction. When deposited with lower work function metal of Al, the peak hole mobility of GaSb NWFET can be enhanced to as high as ≈3372 cm2 V-1 s-1 , showing three times than the un-deposited one. The as-studied metal-semiconductor junction is also efficient for the hole mobility enhancement of other p-channel devices, such as GaAs NWFET, GaAs film FET, and WSe2 FET. With the enhanced mobility, the as-constructed CMOS inverter shows good invert characteristics, showing a relatively high gain of ≈18.1. All results may be regarded as important advances to the next-generation electronics.

Recurrent prosthetic valve dysfunction in a patient with idiopathic hypereosinophilic syndrome: A case report and literature review.

Idiopathic hypereosinophilic syndrome with cardiac involvement is characterized by endocardial fibrosis and thrombosis. Here, we report a case of mitral valve prosthetic dysfunction in a patient with idiopathic hypereosinophilic syndrome and review related cases in the literature. Valve replacement with a 27-mm St. Jude bioprosthetic mitral valve improved his symptoms and hypereosinophilia. A 4-year follow-up revealed that the prosthetic valve was intact without thrombosis. Because mechanical prosthesis implantation yields poor surgical outcomes, bioprosthesis is the preferred choice for patients with idiopathic hypereosinophilic syndrome. Medications for controlling eosinophilia may improve the long-term outcomes of valve replacement surgeries.

Enhancing Performance of a GaAs/AlGaAs/GaAs Nanowire Photodetector Based on the Two-Dimensional Electron-Hole Tube Structure.

Here, we design and engineer an axially asymmetric GaAs/AlGaAs/GaAs (G/A/G) nanowire (NW) photodetector that operates efficiently at room temperature. Based on the I-type band structure, the device can realize a two-dimensional electron-hole tube (2DEHT) structure for the substantial performance enhancement. The 2DEHT is observed to form at the interface on both sides of GaAs/AlGaAs barriers, which constructs effective pathways for both electron and hole transport in reducing the photocarrier recombination and enhancing the device photocurrent. In particular, the G/A/G NW photodetector exhibits a responsivity of 0.57 A/W and a detectivity of 1.83 × 1010 Jones, which are about 7 times higher than those of the pure GaAs NW device. The recombination probability has also been significantly suppressed from 81.8% to 13.2% with the utilization of the 2DEHT structure. All of these can evidently demonstrate the importance of the appropriate band structure design to promote photocarrier generation, separation, and collection for high-performance optoelectronic devices.

Influence of the depletion region in GaAs/AlGaAs quantum well nanowire photodetector.

In semiconductor nanowire (NW) photodetectors, the Schottky barrier formed by the contact between metal and semiconductor can act as a depletion layer. For NW structures with a smaller diameter, the depletion region is especially important to the carrier transport. We prepared a GaAs/AlGaAs quantum well NW photodetector with a two-dimensional electron-hole tube, in which the two-dimensional hole tube (2DHT) formed by the inner layer of GaAs and AlGaAs has the most important role in the regulation of carriers. By adjusting the bias voltage to vary the depth of the depletion region, we have confirmed the influence of the depletion region in a 2DHT. A significant inflection point was found in the responsivity-voltage curve at 1.5 V. By combining the depletion region and 2DHT, the responsivity of the fabricated device was increased by 18 times to 0.199 A W-1 and the detectivity is increased by 5 times to 5.8 × 1010 Jones, compared to the pure GaAs NW photodetector. Reasonable combination of depletion layer and 2DHT was proved to promote high-performance NW photodetector.

Ultrafast carrier relaxation dynamics of photoexcited GaAs and GaAs/AlGaAs nanowire array.

Femtosecond optical pump-probe spectroscopy is employed to elucidate the ultrafast carrier nonradiative relaxation dynamics of bare GaAs and a core-shell GaAs/AlGaAs semiconductor nanowire array. Different from the single nanowire conventionally used for the study of ultrafast dynamics, a simple spin coating and peeling off method was performed to prepare transparent organic films containing a vertical oriented nanowire array for transient absorption measurement. The transient experiment provides the direct observation of carrier thermalization, carrier cooling, thermal dissipation and band-gap energy evolutions along with the carrier relaxations. Carrier thermalization occurs within sub-0.5 ps and proceeds almost independently on the AlGaAs-coating, while the time constants of carrier cooling and thermal dissipation are increased by an order of magnitude due to the AlGaAs-coating effect. The concomitant band-gap evolutions in GaAs and GaAs/AlGaAs include an initial rapid red-shift in thermalization period, followed by a slow blue and/or red shift in carrier cooling, and then by an even slower blue shift in thermal dissipation. The evolution is explained by the competition of band-gap renormalization, plasma screening and band-filling. These findings are significant for understanding the basic physics of carrier scattering, and also for the development of flexible optoelectronic devices.

Pathogenicity of fowl adenovirus (FAdV) serotype 4 strain SDJN in Taizhou geese.

Hydropericardium hepatitis syndrome (HHS) is a fatal disease in chickens, mainly caused by fowl adenovirus serotype 4 (FAdV-4). Since June 2015, HHS has appeared in many provinces in China. The disease has spread from broilers to laying hens, breeders and Cherry Valley ducks, seriously endangering the health of the poultry industry in China. In July 2016, an infectious disease was noticed in a goose farm in Jinan, Shandong Province, China, and hydropericardium was the main finding in post mortem investigations. In the actual study, we isolated a FAdV-4 strain from the livers of naturally-infected goslings and designated it as SDJN. We first evaluated its pathogenicity by inoculating Taizhou geese at 10, 20, and 30 days of age with 10-7.15EID50/0.2 ml doses of the SDJN strain in 1 ml allantoic fluid via subcutaneous injection or oral infection. Clinical signs and pericardial effusion appeared in geese infected subcutaneously at 10 days of age, whereas 20- and 30-day-old geese were not susceptible to FAdV-4. The results of real-time PCR showed that the replication ability of FAdV-4 in geese correlated with the age. Furthermore, results from clinical chemistry showed that FAdV-4 damaged the liver and kidney in geese and the results paralleled viral load and gross lesions. Consequently, FAdV-4 was pathogenic in geese, and the pathogenicity was related to age and mode of infection. This study is the first experimental infection of FAdV-4 in geese, which will provide a basis for further understanding of the disease. RESEARCH HIGHLIGHTS Pathogenicity tests with a FAdV-4 were conducted in geese, which included data on clinical signs, gross pathology, histopathology, clinical chemistry and viral load. FAdV-4 could replicate in geese and HHS was successfully induced. Pathogenicity of FAdV-4 in geese was related to the age and routes of infection.

Analysis of the influence and mechanism of sulfur passivation on the dark current of a single GaAs nanowire photodetector.

Nanowire photodetectors, which have the advantages of fast response and high photoelectric conversion efficiency, can be widely applied in various industries. However, the rich surface states result in large dark current and can hinder the development of high-performance nanowire photodetectors. In this paper, the influence and mechanism of sulfur surface passivation on the dark current of a single GaAs nanowire photodetector have been studied. The dark current is significantly reduced by about 30 times after surface passivation. We confirm that the origin of the reduction of dark current is the decrease in the surface state density. As a result, a single GaAs nanowire photodetector with low dark current of 7.18 × 10-2 pA and high detectivity of 9.04 × 1012 cmHz0.5W-1 has been achieved. A simple and convenient way to realize high-performance GaAs-based photodetectors has been proposed.

Zn or O? An Atomic Level Comparison on Antibacterial Activities of Zinc Oxides.

For the first time, the influence of different types of atoms (Zn and O) on the antibacterial activities of nanosized ZnO was quantitatively evaluated with the aid of a 3D-printing-manufactured evaluation system. Two different outermost atomic layers were manufactured separately by using an ALD (atomic layer deposition) method. Interestingly, we found that each outermost atomic layer exhibited certain differences against gram-positive or gram-negative bacterial species. Zinc atoms as outermost layer (ZnO-Zn) showed a more pronounced antibacterial effect towards gram-negative E. coli (Escherichia coli), whereas oxygen atoms (ZnO-O) showed a stronger antibacterial activity against gram-positive S. aureus (Staphylococcus aureus). A possible antibacterial mechanism has been comprehensively discussed from different perspectives, including Zn(2+) concentrations, oxygen vacancies, photocatalytic activities and the DNA structural characteristics of different bacterial species.

[Optical Properties Investigation of p-Type ZnO Film Based on Doping by Diffusion].

The main purpose of this paper is to investigate the optical properties of p-type ZnO film based on P doping. ZnO film was grown by Atomic layer deposition (ALD) on InP subsrate in this experiment, and phosphorus diffused into ZnO lattice by annealing treatment at different temperature (500, 700 °C). The optical properties of samples were investigated by photoluminescence (PL) spectroscopy, which indicated that the annealing temperature is the important factor influencing the phosphorus diffusion doping. The low-temperature PL spectra of the sample which annealed at 700 °C for 1 h exhibited acceptor related emission peaks located at 3.351, 3.311, 3.246 and 3.177 eV, which were attributed to A °X, FA, DAP and DA-1LO, respectively. The acceptor binding energy is estimated to be about 122 meV, which is agreed with the theoretic values in phosphorus-doped ZnO films. In this paper, through thermal diffusion method to realize the p-type doped ZnO thin films, it solved the main problems which limited the development of ZnO based optoelectronic devices, and has an important significance for the development of the ZnO semiconductor materials and ZnO based photoelectric device.

[Effects of annealing temperature on the structure and optical properties of ZnMgO films prepared by atom layer deposition].

In the present paper, we report the research on the effects of annealing temperature on the crystal quality and optical properties of ZnMgO films deposited by atom layer deposition(ALD). ZnMgO films were prepared on quartz substrates by ALD and then some of the samples were treated in air ambient at different annealing temperature. The effects of annealing temperature on the crystal quality and optical properties of ZnMgO films were characterized by X-ray diffraction (XRD), photoluminescence (PL) and ultraviolet-visible (UV-Vis) absorption spectra. The XRD results showed that the crystal quality of ZnMgO films was significantly improved when the annealing temperature was 600 degrees C, meanwhile the intensity of(100) diffraction peak was the strongest. Combination of PL and UV-Vis absorption measurements showed that it can strongly promote the Mg content increasing in ZnMgO films and increase the band gap of films. So the results illustrate that suitable annealing temperature can effectively improve the crystal quality and optical properties of ZnMgO films.

[Preparation of MgxZn1-xO/Au/MgxZn1-xO multilayer transparent conductive film and studies of its photoelectric properties].

In the present paper, MgxZn1-xO and MgxZn1-xO/Au/MgxZn1-xO multilayer structures of transparent conductive film were prepared by the simple operation of sol-gel and RF magnetron sputtering method on quartz substrate respectively and then they were annealed. The surface, electrical, crystal and optical properties of the films at different annealing temperature were determined by UV-Vis spectrophotometer, X-ray diffraction, photoluminescence and Hall effect, respectively. The influence of annealing temperature on the films was also investigated. The testing results indicated that the films with good c-axis orientation presented hexagonal wurtzite structure. With increasing Mg components, the optical band gap of ZnO thin film increased gradually. There was an obvious blue shift phenomenon in PL spectrum and absorption spectrum line. But the electrical properties of the films declined. In MgxZn1-xO/Au/MgxZn1-xO multilayer structure of thin film samples, the existence of Au interlining led to the poor optical properties of thin film, and the light transmittance in the ultraviolet region was 60%. Compared with MgxZn1-xO film, the electrical properties of MgxZn1-xO/Au/MgxZn1-xO multilayer structure of transparent conductive film were improved, the resistivity and migration rate were significantly increased. In addition, high temperature annealing treatment could effectively improve the crystal quality of thin film and further improve the electrical characteristics of the samples. After the annealing treatment at 500 °C, migration rate of the film reached to 40.9 cm2 · 1 Vs(-1) while the resistivity was 0.0057 Ω · cm. Due to the rising of temperature, the crystal size increased from 25.1 to 32.4 nm to reduce the mobility of the film. Therefore, MgxZn1-xO/Au/MgxZn1-xO multilayer structure of transparent conductive film played an important role in promoting the ZnO transparent conductive film application in deep ultraviolet devices.

[Preparation of Mg(x)Zn(1-x)O nanofibers using PVP nanofibers as templates by atom layer deposition and their optical properties].

In the present paper, Mg(x)Zn(1-x)O nanofibers with different doping concentration were prepared by atom layer deposition (ALD) using polyvinyl pyrrolidone (PVP) nanofibers as template, which were synthesized by electrospinning. The influence of different Mg doping concentration on the structure and optical properties of composite nanofibers was investigated. The samples were characterized by field emission scanning electron microscopy (FESEM), ultraviolet visible (UV-Vis) absorption spectroscopy and photoluminescence (PL) spectra. The doping of Mg did not change the morphologies of ZnO nanofibers, the morphologies of all the samples were very similar while the diameter of Mg(x)Zn(1-x)O-PVP composite nanofibers became larger after doping. With the increase in the Mg doping concentration, the absorption edge shifted to larger energy side, revealing the band gap tenability of Mg(x)Zn(1-x)O nanofibers. Meanwhile, a significant blue shift of the UV emission peak from 377 to 362 nm was observed in PL spectra. Compared with ZnO-PVP composite nanofibers, the UV emission intensity of Mg(x)Zn(1-x)O-PVP composite nanofibers was much stronger. Component control Mg(x)Zn(1-x)O nanofibers can be synthesized by this method. The doping of Mg elements in ZnO can effectively improve the band gap of ZnO-PVP nanofibers and the intensity of UV emission.