Self-doping effect in confined copper selenide semiconducting quantum dots for efficient photoelectrocatalytic oxygen evolution

Self-doping can not only suppress the photogenerated charge recombination of semiconducting quantum dots by self-introducing trapping states within the bandgap, but also provide high-density catalytic active sites as the consequence of abundant non-saturated bonds associated with the defects. Here, we successfully prepared semiconducting copper selenide (CuSe) confined quantum dots with abundant vacancies and systematically investigated their photoelectrochemical characteristics. Photoluminescence characterizations reveal that the presence of vacancies reduces the emission intensity dramatically, indicating a low recombination rate of photogenerated charge carriers due to the self-introduced trapping states within the bandgap. In addition, the ultra-low charge transfer resistance measured by electrochemical impedance spectroscopy implies the efficient charge transfer of CuSe semiconducting quantum dots-based photoelectrocatalysts, which is guaranteed by the high conductivity of their confined structure as revealed by room-temperature electrical transport measurements. Such high conductivity and low photogenerated charge carriers recombination rate, combined with high-density active sites and confined structure, guaranteeing the remarkable photoelectrocatalytic performance and stability as manifested by photoelectrocatalysis characterizations. This work promotes the development of semiconducting quantum dots-based photoelectrocatalysis and demonstrates CuSe semiconducting quantum confined catalysts as an advanced photoelectrocatalysts for oxygen evolution reaction

Terahertz metamaterial absorber with switchable function between broadband and dual narrowband

In this paper, based on the tunability of vanadium dioxide and graphene, a simple and novel multifunctional terahertz metamaterial absorber is proposed that can dynamically switch functions and absorption spectra. The simulation results using the finite element method via Comsol Multiphysics show that the proposed design can achieve large broadband absorption, perfect dual narrowband absorption, and total reflection through controlling external conditions. The absorption intensity can be adjusted from 4.5% to 100% over the whole broadband operation range. A detailed absorption mechanism explanation is given with the help of impedance matching principles and the distribution of current and electric field, and the influence of graphene’s Fermi level and different incidence angles on absorption performance is evaluated. Our design not only functionally adds the part to be a reflector but also provides considerable improvements in absorption amplitude, bandwidth, and adjustment range when compared to previous works. In addition, its function switching and resonant frequencies are flexible in terms of tuning and have strong resistance to external temperature interference. Therefore, the proposed structure holds significant applications in the terahertz field, such as terahertz modulators, sensing, and optical switches

The Optimizing Effect of Nitrogen Flow Ratio on the Homoepitaxial Growth of 4H-SiC Layers

In this study, a 4H-SiC homoepitaxial layer was grown on a 150 mm 4° off-axis substrate using a horizontal hot-wall CVD reactor. The research aimed to investigate the impact of varying the C/Si ratio and temperature while also changing the N2 flow rate and N2 flow ratio on the growth rate (thickness), doping, surface roughness, and uniformity of the large-size 4H-SiC epitaxial layer. The results indicate that the growth rate and thickness uniformity of the film increases with an increase in the C/Si ratio. Additionally, adjusting the N2 flow rate in a timely manner based on the change in the C/Si ratio is crucial to achieving the best epitaxial layer doping concentration and uniformity. The study found that, as the temperature increases, the film thickness and thickness uniformity also increase. The maximum thickness recorded was 6.2 μm, while the minimum thickness uniformity was 1.44% at 1570 °C. Additionally, the surface roughness reached its lowest point at 0.81 nm at 1570 °C. To compensate for the difference in thickness and doping concentration caused by temperature distribution and uneven airflow, the N2 flow ratio was altered. In particular, at a growth temperature of 1570 °C, a N2 flow ratio of 1.78 can improve the uniformity of doping by 4.12%

Matrix-dependent Strain Distributions of Au and Ag Nanoparticles in a Metal-oxide-semiconductor-based Nonvolatile Memory Device

The matrix-dependent strain distributions of Au and Ag nanoparticles in a metal-oxide-semiconductor based nonvolatile memory device are investigated by finite element calculations. The simulation results clearly indicate that both Au and Ag nanoparticles incur compressive strain by high-k Al2O3 and conventional SiO2 dielectrics. The strain distribution of nanoparticles is closely related to the surrounding matrix. Nanoparticles embedded in different matrices experience different compressive stresses, which provide opportunities for tailoring the microstructure of Au and Ag nanoparticles. This opens up ways for exploring strain effects on physical properties and further tunes the charge storage properties of nanoparticles

High Uniformity 6-Inch InGaP Epitaxial Growth

The growth of 6-inch In0.485Ga0.515P has been examined in this study. The effects of growth temperature, the V/III ratio, and the H2 total flow on solid composition, growth rate, and crystal quality have been systematically investigated and discussed. Additionally, the effect of growth conditions on doping efficiency has been investigated. Finally, the relationship between electrical uniformity, optical uniformity, and the growth conditions of the 6-in epitaxial layer is discussed. At a growth temperature of 600 °C and a V/III of 250, a high uniformity 6-in InGaP epitaxial layer with an electrical uniformity of 0.33% and optical uniformity of 0.03% was produced. InGaP was grown by the metal-organic chemical vapor deposition method in an Aixtron 2800G4 reactor. High resolution X-ray diffraction (HRXRD), photoluminescence (PL), sheet resistance, electrochemical capacitance-voltage (ECV), and the Hall effect were used to characterize the characteristics of InGaP epitaxial layers

An Ultra-Low Bending Loss Negative Curvature Hollow Core Fiber With a Polygon Jacketing Layer

We design and simulate a new type of hollow-core antiresonant fiber with the polygon jacketing layer. Through numerical calculations, the confinement loss is approximately 0.003 dB/km at 1.45 μm and the bandwidth is ∼ 410 nm @ CL < 0.1 dB/km. We found that more nested tubes can be connected to the jacketing layer to avoid the generation of more cladding nodes. The nested tube cladding with the small size of air holes can effectively suppress the coupling between the fiber cladding and core modes even at extreme bending conditions. Ultra-low bending loss is achieved, and the bending loss is lower than ∼ 0.05 dB/km @ bend radius Rb = 3 cm at 1.50 μm

Ibrutinib versus bendamustine plus rituximab for first-line treatment of 65 or older patients with untreated chronic lymphocytic leukemia without del(17p)/TP53 mutation in China: a lifetime economic research study

Abstract Background The incidence and mortality rates of patients with chronic lymphocytic leukemia (CLL) in China have recently increased. This study performed a long-term economic evaluation of the first-line treatment strategies ibrutinib (IB) or bendamustine (BE) plus rituximab (RI) for previously untreated older patients with CLL without the del(17p)/TP53 mutation in China. Methods Based on clinical data from large, randomized trials, a Markov model including four disease states (event-free survival, treatment failure, post-treatment failure, and death) was used to estimate the incremental costs per quality adjusted-life year (QALY) gained from the first-line IB strategy versus the BE plus RI strategy over a 10-year period. All costs were adjusted to 2022 values based on the Chinese Consumer Price Index, and all costs and health outcomes were discounted at an annual rate of 5%. Sensitivity analysis was performed to confirm the robustness of base-case results. Results Compared to the first-line BE plus RI strategy, first-line IB treatment achieved 1.17 additional QALYs, but was accompanied by $88,046.78 (estimated in 2022 US dollars) in decremental costs per patient over 10 years. Thus, first-line treatment with IB appeared to have absolute dominance compared to the BE plus RI strategy. Sensitivity analysis confirmed the robustness of these results. Conclusions The first-line treatment with IB is absolutely cost-effective compared to the first-line BE plus RI treatment strategy for 65 or older patients with CLL without the del (17p)/TP53 mutation from the Chinese payer perspective. Therefore, it is strongly recommended that Chinese health authorities select the former strategy for these CLL patients