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WO3/BiVO4 Type-II Heterojunction Arrays Decorated with Oxygen-deficient ZnO Passivation Layer: a Highly Efficient and Stable Photoanode
摘要： In present work, we report a ternary WO3/BiVO4/ZnO photoanode with boosted PEC efficiency and stability towards highly efficient water splitting. The type-II WO3/BiVO4 heterojunction arrays are firstly prepared by hydrothermal growth of WO3 nanoplate arrays onto the substrates of ?uorine-doped tin oxide (FTO) coated glasses, followed by spin-coating of BiVO4 layers onto the WO3 nanoplate surfaces. After that, thin ZnO layers are further introduced onto the WO3/BiVO4 heterojunction arrays via atomic layer deposition (ALD), leading to the construction of ternary WO3/BiVO4/ZnO photoanodes. It is verified that the ZnO thin layer in WO3/BiVO4/ZnO photoanode contains abundant oxygen vacancies, which could be acted as an effective passivation layer to enhance the charge separation and surface water oxidation kinetics of photogenerated carriers. The as-prepared WO3/BiVO4/ZnO photoanode produces a photocurrent of 2.96 mA cm-2 under simulated sunlight with an incident photon-to-current conversion e?ciency (IPCE) of ～72.8 % at 380 nm at a potential of 1.23 V vs. RHE without cocatalysts, both of which are comparable to the state-of-art WO3/BiVO4 counterparts. Moreover, the photocurrent of WO3/BiVO4/ZnO photoanode shows only 9 % decay after 6 h, suggesting its high photoelectrochemical (PEC) stability.
关键词： type-II heterojunction,WO3/BiVO4,nanoplate arrays,photoelectrochemistry,passivation layer
更新于2025-09-04 15:30:14
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AIP Conference Proceedings [Author(s) INTERNATIONAL CONFERENCE ON SUSTAINABLE ENGINEERING AND TECHNOLOGY (ICONSET 2018) - Karnataka, India (19–20 April 2018)] - Synthesis of heterojunction layers of graphene/MoS2 and its characterization
摘要： The synthesis of atomically thin layered MoS2/Graphene heterostructure is of great interest in optoelectronic devices because of their unique properties. Herein, we present a synthesis method to prepare heterostructure of MoS2/graphene using low pressure chemical vapor deposition. Atomic force microscopy, Raman spectra demonstrated that MoS2 film on graphene exhibited good thickness uniformity. This novel sensing structure based on a 2D heterostructure promises to provide a simple route to an essential sensing platform for wearable electronics.
关键词： Heterojunction layer,Characterization,MoS2,Application,Graphene
更新于2025-09-04 15:30:14
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Secure Communication in Non-Geostationary Orbit Satellite Systems: A Physical Layer Security Perspective
摘要： Satellite communication systems serve as an indispensable component of wireless heterogeneous networks in 5G era for providing various critical civil and military applications. However, due to the broadcast nature and full accessibility of wireless medium, such systems exist serious security threats. As an effort to address this issue, this paper, for the first time, investigates the secure communication in a non-geostationary orbit (NGSO) satellite system from a physical layer security perspective. Specifically, we focus on the downlink of an NGSO satellite which provides services to a fixed earth station and is wiretapped by a fixed eavesdropper. We first apply three types of orbiting models to characterize the movement state of the satellite. Based on the orbiting models, we then provide theoretical analysis for the secure communication performance of such a system. The expressions of two fundamental performance metrics, secrecy capacity and secrecy outage probability, are derived in closed-form for any system time. Finally, we conduct extensive simulations to validate our theoretical performance analysis and illustrate the security performance in a practical NGSO satellite communication system.
关键词： Non-geostationary orbit satellite system,physical layer security,performance evaluation
更新于2025-09-04 15:30:14
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Effect of Deposition Method on Valence Band Offsets of SiO <sub/>2</sub> and Al <sub/>2</sub> O <sub/>3</sub> on (Al <sub/>0.14</sub> Ga <sub/>0.86</sub> ) <sub/>2</sub> O <sub/>3</sub>
摘要： There are often variations in reported valence band offsets for dielectrics on semiconductors and some of the reasons documented include metal or carbon contamination, interfacial disorder, variations in dielectric composition, thermal conditions, strain, and surface termination effects. In this paper we show that there are differences of up to 1 eV in band alignments for the common gate dielectrics SiO2 and Al2O3 on single crystal (Al0.14Ga0.86)2O3, depending on whether they are deposited by sputtering or Atomic Layer Deposition. In the case of Al2O3, this changed the band alignment from nested (type I) to staggered gap (type II). The valence band offset at each heterointerface was measured using X-Ray Photoelectron Spectroscopy and was determined to be ?0.85 ± 0.15 eV for sputtered Al2O3 and 0.23 ± 0.04 eV for ALD Al2O3 on β-(Al0.14Ga0.86)2O3, while for SiO2 it was 0.6 ± 0.10 eV for sputtered and 1.6 ± 0.25 eV for ALD. These results are consistent with recent results showing that the surface of Ga2O3 and related alloys are susceptible to severe changes during exposure to energetic ion environments.
关键词： Al2O3,(Al0.14Ga0.86)2O3,SiO2,valence band offsets,Atomic Layer Deposition,X-Ray Photoelectron Spectroscopy,sputtering
更新于2025-09-04 15:30:14
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The Post Annealing to Control the Number of Layers of 2D MoS2 and SnS2
摘要： We have demonstrated that post annealing could control the layer thickness of 2D MoS2 and SnS2 films transferred on a SiO2/Si substrate by varying the annealing temperature and time. Atomic force microscopy and Raman spectroscopy characterizations revealed that higher annealing temperature and longer treatment time led to thinner films, lower residues and fewer impurities on the surface of 2D materials. In addition, a higher possibility to attain few-layers on both 2D films was achieved using post annealing. The multiple layers of pristine films having the thickness over 15 nm were reduced down to bi-layers after annealing. We observed that the moderate annealing temperature of 450 °C on led to effective layer-thinning compared to the films annealed at 340 °C. The post annealing at 450 °C produced very smooth few-layers (≤4 nm thickness, >1 μm size) of 2D MoS2 and SnS2. However, the 2D films decomposed or disappeared at temperature greater than 650 °C. In addition, process time also affected the number of layers and the sweet spot turned out to be 2 to 3 hours in our experiment.
关键词： Annealing,Mechanical Exfoliation,Layer-Thinning,2D Materials,SnS2,MoS2
更新于2025-09-04 15:30:14
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Effects of UV-C radiation on common dandelion and purple coneflower: First results
摘要： Ultraviolet-C (UV-C) light (100 ≤ λ ≤ 280 nm) is a ionizing radiation that can damage living organisms. An experiment was conducted on plants of common dandelion (Taraxacum officinale Weber, T. Densleonis Desf.) and purple coneflower [Echinacea purpurea, (L.) Moench] irradiated with UV-C at different exposition times, under controlled conditions and grown in self-produced characterized compost, to assess the effect of different doses UV-C radiation on some physiological parameters. Trials have been carried out using a black chamber equipped with an UV-C lamp in which plants were divided in four groups on the basis of UV-C irradiation period (10, 30, 60, and 120 min). Non-irradiated plants were kept as controls. Plant photosynthetic performance, chlorophyll content (SPAD) and some morphologic traits were recorded before, immediately after irradiations and 20 days weeks later. The effects on photosynthetic performances and chlorophyll contents (SPAD) were evaluated and compared with data obtained in similar experiments where tomato plants were irradiated at different times with UV-C light. In both species, SPAD values decreased as the irradiation period became longer. The two species showed different gas exchange dynamics, depending on the UV-C exposure time. Two months after the UV-C irradiation, plant dry weight measured at 120-min UV-C exposure was significantly lower than the control.
关键词： photosynthesis,dry matter,gas exchange,chlorophyll content,ozone layer.
更新于2025-09-04 15:30:14