AlGaInAs Multi-Quantum Well Lasers on Silicon-on-Insulator Photonic Integrated Circuits Based on InP-Seed-Bonding and Epitaxial Regrowth

The tremendous demand for low-cost, low-consumption and high-capacity optical transmitters in data centers challenges the current InP-photonics platform. The use of silicon (Si) photonics platform to fabricate photonic integrated circuits (PICs) is a promising approach for low-cost large-scale fabrication considering the CMOS-technology maturity and scalability. However, Si itself cannot provide an efficient emitting light source due to its indirect bandgap. Therefore, the integration of III-V semiconductors on Si wafers allows us to benefit from the III-V emitting properties combined with benefits offered by the Si photonics platform. Direct epitaxy of InP-based materials on 300 mm Si wafers is the most promising approach to reduce the costs. However, the differences between InP and Si in terms of lattice mismatch, thermal coefficients and polarity inducing defects are challenging issues to overcome. III-V/Si hetero-integration platform by wafer-bonding is the most mature integration scheme. However, no additional epitaxial regrowth steps are implemented after the bonding step. Considering the much larger epitaxial toolkit available in the conventional monolithic InP platform, where several epitaxial steps are often implemented, this represents a significant limitation. In this paper, we review an advanced integration scheme of AlGaInAs-based laser sources on Si wafers by bonding a thin InP seed on which further regrowth steps are implemented. A 3 µm-thick AlGaInAs-based MutiQuantum Wells (MQW) laser structure was grown onto on InP-SiO2/Si (InPoSi) wafer and compared to the same structure grown on InP wafer as a reference. The 400 ppm thermal strain on the structure grown on InPoSi, induced by the difference of coefficient of thermal expansion between InP and Si, was assessed at growth temperature. We also showed that this structure demonstrates laser performance similar to the ones obtained for the same structure grown on InP. Therefore, no material degradation was observed in spite of the thermal strain. Then, we developed the Selective Area Growth (SAG) technique to grow multi-wavelength laser sources from a single growth step on InPoSi. A 155 nm-wide spectral range from 1515 nm to 1670 nm was achieved. Furthermore, an AlGaInAs MQW-based laser source was successfully grown on InP-SOI wafers and efficiently coupled to Si-photonic DBR cavities. Altogether, the regrowth on InP-SOI wafers holds great promises to combine the best from the III-V monolithic platform combined with the possibilities offered by the Si photonics circuitry via efficient light-coupling.

Highly Sensitive Near-Infrared SERS Nanoprobes for in Vivo Imaging Using Gold-Assembled Silica Nanoparticles with Controllable Nanogaps

Backgroud: Surface-enhanced Raman scattering (SERS) imaging is widely exploited, given its advantages such as multiplex capacity, non-photobleaching property, and high sensitivity. Near-infrared (NIR) radiation is suitable for in vivo studies because it exhibits good tissue penetration capability. Results In this study, gold (Au)-assembled silica (SiO2) nanoparticles (SiO2@Au@Au NPs) as NIR SERS nanoprobes are synthesized by a seed-mediated growth method. SiO2@Au@Au NPs with six different sizes of Au NPs are prepared by controlling the concentration of the Au precursor in the growth step. Therefore, the surface plasmonic band of the nanogaps between Au NPs on the SiO2 surface could be controlled from 4.16 to 0.98 nm, thus generating SERS hotspots. SiO2@Au@Au NPs with a 0.98-nm gap shows high SERS signals after being subjected to an excitation wavelength of 785 nm (enhancement factor ~3.8 × 106). SiO2@Au@Au nanoprobes shows detectable in vivo SERS signals at a concentration of 16 µg/mL in a 7-mm-thick animal tissue specimen. SiO2@Au@Au NPs with 14 different Raman label compounds shows distinguishable SERS signals upon being subcutaneously injected into nude mice. Conclusion Through this study, it is highlighted that their potential for use in in vivo applications as multiplex nanoprobes.

Gypsum Supplies Calcium to Ultisol Soil and Its Effect on Pineapple Growth, Yield and Fruit Quality in Lower Single Bed under Climate Change Issue

A lower bed single row for pineapple cultivation could protect pineapple from soil erosion in rainy season and during drought, however, disease problem could arise due to water logging. Two experiments using a lower bed single row was done to understand the ability of gypsum providing soil calcium (Ca) available to pineapple plant, resistance to heart rot disease, and give better effect on crop growth and fruit quality of the pineapple in Ultisol soil. In the first trial, four level dosis of gypsum (0, 1.0, 1.5, 2.0 Mg ha-1) and dolomite 2 Mg ha-1 were applied by spreading and incorporated into the soil which have saturated with inoculums of Phytophthora nicotianae. In the second trial, gypsum treatments (0, 1.0, 1.5, 2.0, 2.5 Mg ha-1) were applied in the row between the single row beds as a basic fertilizer. The result showed that P. nicotianae attacked the pineapple plants in all treatments at 6 weeks after planting (WAP), and at 10 WAP, the mortality of dolomite treatment reached 63.8%, significantly different than that for gypsum treatments (3.3-14.3%). In the second experiment, gypsum increased plant weight significantly at 3 until 9 months after planting especially when it was applied 1.5-2.5 Mg ha-1. Fruit texture, total soluble solid (TSS), titratable acidity (TA) were not significant different among the treatment but all meet the standards for grades of canned pineapple. Result showed that soil applied gypsum before planting provides soil calcium and met the plant Ca requirement during a period of early and fast growth step and safe for heart rot disease.

Undulation of a moving fluid membrane pushed by filament growth

Biomembranes experience out-of-equilibrium conditions in living cells. Their undulation spectra are different from those in thermal equilibrium. Here, we report on the undulation of a fluid membrane pushed by the stepwise growth of filaments as in the leading edge of migrating cells, using three-dimensional Monte Carlo simulations. The undulations are largely modified from equilibrium behavior. When the tension is constrained, the low-wave-number modes are suppressed or enhanced at small or large growth step sizes, respectively, for high membrane surface tensions. In contrast, they are always suppressed for the tensionless membrane, wherein the wave-number range of the suppression depends on the step size. When the membrane area is constrained, in addition to these features, a specific mode is excited for zero and low surface tensions. The reduction of the undulation first induces membrane buckling at the lowest wave-number, and subsequently, other modes are excited, leading to a steady state.

Undulation of a moving fluid membrane pushed by filament growth

Biomembranes experience out-of-equilibrium conditions in living cells. Their undulation spectra are different from those in thermal equilibrium. Here, we report on the undulation of a fluid membrane pushed by the stepwise growth of filaments as in the leading edge of migrating cells, using three-dimensional Monte Carlo simulations. The undulations are largely modified from equilibrium behavior. When the tension is constrained, the low-wave-number modes are suppressed or enhanced at small or large growth step sizes, respectively, for high membrane surface tensions. In contrast, they are always suppressed for the tensionless membrane , wherein the wave-number range of the suppression depends on the step size. When the membrane area is constrained, in addition to these features, a specific mode is excited for zero and low surface tensions. The reduction of the undulation first induces membrane buckling at the lowest wave-number, and subsequently, other modes are excited, leading to a steady state.

Functionalization of Commercial Electrospun Veils with Zinc Oxide Nanostructures

The present research is focused on the synthesis of hexagonal ZnO wurtzite nanorods for the decoration of commercially available electrospun nylon nanofibers. The growth of ZnO was performed by a hydrothermal technique and for the first time on commercial electrospun veils. The growth step was optimized by adopting a procedure with the refresh of growing solution each hour of treatment (Method 1) and with the maintenance of a specific growth solution volume for the entire duration of the treatment (Method 2). The overall treatment time and volume of solution were also optimized by analyzing the morphology of ZnO nanostructures, the coverage degree, the thermal and mechanical stability of the obtained decorated electrospun nanofibers. In the optimal synthesis conditions (Method 2), hexagonal ZnO nanorods with a diameter and length of 53.5 nm ± 5.7 nm and 375.4 nm ± 37.8 nm, respectively, were obtained with a homogeneous and complete coverage of the veils. This easily scalable procedure did not damage the veils that could be potentially used as toughening elements in composites to prevent delamination onset and propagation. The presence of photoreactive species makes these materials ideal also as environmentally friendly photocatalysts for wastewater treatment. In this regard, photocatalytic tests were performed using methylene blue (MB) as model compound. Under UV light irradiation, the degradation of MB followed a first kinetic order data fitting and after 3 h of treatment a MB degradation of 91.0% ± 5.1% was achieved. The reusability of decorated veils was evaluated and a decrease in photocatalysis efficiency was detected after the third cycle of use.

A Deep Learning Based Dislocation Detection Method for Cylindrical Crystal Growth Process

For the single crystal furnace used in the photovoltaic industry, growth problems occur frequently due to dislocations during the shouldering and cylindrical growth steps of the Czochralski (CZ) crystal growth. Detecting the dislocation phenomenon in the cylindrical growth step is very important for entire automation of the CZ crystal furnace, since this process usually lasts for more than 48h. The irregular nature of different patterns of dislocation would impose a big challenge for a traditional machine vision-based detection method. As almost no publications have been dedicated to detecting this phenomenon, to address this issue, after analyzing the characteristics of the silicon ingot image of this process, this paper proposes a kind of deep learning-based dislocation detection method along with tracking strategy to simulate manual inspection. The model has a good detection effect whether there is occlusion or not, the experimental results show that the detection accuracy is 97.33%, and the inference speed is about 14.7 frames per second (FPS). It can achieve the purpose of reducing energy consumption and improving process automation by monitoring this process.

Mask-free three-dimensional epitaxial growth of III-nitrides

A novel catalyst-free and maskless growth approach is presented to form an ordered geometrical array of three-dimensional (3D) AlGaN/AlN microrods. The growth method is composed of a single growth step using metalorganic vapor phase epitaxy, achieving microstructures with homogeneous diameters, shapes and sizes over relatively large scale (on 2-in. wafer). The 3D AlGaN/AlN heterostructures are grown in a form of micro-sized columns elongated in one direction perpendicular to the substrate surface and with a hexagonal cross section. A careful examination of growth steps revealed that this technology allows to suppress coalescence and lateral overgrowth, promoting vertical 3D growth. Interestingly, two distinct morphologies can be obtained: honeycomb-like hexagonal arrangement perfectly packed and with twisted microrods layout, by controlling strain state in AlN buffer layers. Consequently, 3D AlGaN microrods on tensile-strained AlN templates show a 0° twisted morphology, while on compressive-strained templated a 30° twisted arrangement. Moreover, the optical and crystalline quality studies revealed that the top AlGaN layers of the examined 3D semiconductor structures are characterized by a low native point-defect concentration. These 3D AlGaN platforms can be applied for light emitting devices or sensing applications. Graphic abstract

Impact of deposition borehole geometry on mechanical spalling in nuclear waste repositories

<p>Predictions of rock spalling around deep-drilled boreholes and tunnels in underground geologic repositories in crystalline rocks remain a significant challenge, due to the heterogeneities present in the rock mass, uncertain stress fields, and the complex thermo-mechanical behaviour of the rock mass at elevated temperatures.</p><p>This study presents a three-dimensional numerical analysis of multiple fracture growth leading to spalling around a deposition borehole. The mechanical spalling due to stress amplification after drilling is simulated using a finite element-based discrete fracture growth simulator. Fractures are grown by computing stress intensity factors at each fracture tip, and the mesh is adapted to accommodate the changing fracture geometries at every growth step. The model is validated using the Äspö Pillar Stability Experiment (APSE), calibrated to simulate the drilling of a borehole in the Forsmark granite, and subjected to a far-field anisotropic triaxial stress, corresponding to the <em>in situ</em> stress model from Forsmark. The deposition tunnel is implicitly simulated by attaching the deposition borehole to a free domain boundary.</p><p>The effect of borehole geometry on the predicted spalling around a typical deposition borehole is studied. The cylindrical borehole is modified at the top to provide an access ramp for the spent fuel canisters, which can effectively improve the repository design by reducing the height of the deposition tunnel. Three cases are investigated, in which the borehole top is cylindrical, conical, and wedge-shaped, respectively. Numerical results show that spalling occurs in all cases, but the borehole geometry affects fracture nucleation and growth patterns. The enlargement of the borehole top induces higher stress concentrations at the borehole-tunnel junction, increasing the severity of spalling at the top of the borehole. The final spalled zone and the fractures-borehole interaction are illustrated for each stress and geometry scenario.</p>

Tuning oxygen vacancy and growth step for the high performance of Nd1+xBa2−xCu3Oy bulk cryomagnets

The Nd1+xBa2−xCu3Oy superconductor is considered to be one of the most promising materials in the REBaCu3Oy family owing to its excellent properties of high critical transition temperature (Tc) and high current density.