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<i>In situ</i> topotactic fabrication of direct Z-scheme 2D/2D ZnO/Zn <sub/>x</sub> Cd <sub/>1?x</sub> S single crystal nanosheet heterojunction for efficient photocatalytic water splitting
摘要： Direct Z-scheme heterojunction can effectively enhance the photocatalytic activity due to its low carrier recombination rate and high redox ability. In this study, a 2D/2D ZnO/ZnxCd1?xS single crystal nanosheet heterojunction is synthesized in situ by topotactic sulfurization/oxidization pyrolysis of Zn/Cd/Al layer double hydroxides (LDHs). Its unique structure provides not only numerous intimate interfaces but also a direct Z-scheme junction. The in situ topotactic fabrication of ZnO by the oxidation process causes some Zn ions to dissolve out from the Zn0.67Cd0.33S solid solution nanosheets with increase in annealing temperature and time. The longer the time for oxidation, the more ZnO is obtained. The formation of ZnO yields 2D/2D ZnO/ZnxCd1?xS single crystal nanosheet heterojunction, which increases the visible light absorption and boosts the separation of photogenerated carriers. The ZnO/ZnxCd1?xS-4 single crystal nanosheet heterojunction presents the highest photocatalytic activity under visible light irradiation (38.93 mmol h?1 g?1), which is nearly 16.93 times higher than that of Zn0.67Cd0.33S-300, and an external quantum efficiency of 40.97% at λ = 420 nm. The proposed synthetic route for the construction of 2D/2D ZnO/ZnxCd1?xS single crystal nanosheet provides a direct Z-scheme structure with highly efficient photocatalytic hydrogen evolution activity.
关键词： 2D/2D ZnO/ZnxCd1?xS,photocatalytic water splitting,Zn/Cd/Al layer double hydroxides,Direct Z-scheme heterojunction,topotactic sulfurization/oxidization pyrolysis
更新于2025-09-04 15:30:14
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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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Nanorods Array of SnO2 Quantum Dots Interspersed Multiphase TiO2 Heterojunctions with Highly Photocatalytic Water Splitting and Self-Rechargeable Battery-Like Applications
摘要： Facing an ever-growing demand for sustainable and renewable power sources, it has detonated the development of novel materials for photocatalytic water splitting, but how to enhance the photocatalytic efficiency remains a core problem. Herein, we reported a conceptual effective and experimental confirmed strategy in SnO2 quantum dots (QD) interspersed multiphase (Rutile, Anatase) TiO2 nanorods arrays (SnO2/RA@TiO2 NRs) to immensely enhance the carrier separation for highly efficient water splitting by merging simultaneously the QD, multiphase, and heterojunction approaches. Under this synergistic effect, a doping ratio of 25% SnO2 QD interspersed into multiphase TiO2 NRs exhibited a superior optical adsorption and excellent photocurrent density (2.45 mA/cm2 at 1.0 V), giving rise to a largely enhanced incident light to current efficiency (IPCE) in the UV region (45~50 %). More importantly, this material-based device can act as power supply with a voltage of ~2.8 V after illumination, which can automatically self-recharging by reacting with oxygen vacancy and water molecule to realize reusing. The current study provide a new paradigm about heightening the carrier separation extent of QD interspersed multiphase heterojunctions, fabricate a new solar energy converting material/device, and achieve a highly photocatalytic water splitting/self-charging battery-like application.
关键词： Photocatalytic,Water splitting,Titanium Dioxide,Heterojunction
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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[IEEE 2018 IEEE BiCMOS and Compound Semiconductor Integrated Circuits and Technology Symposium (BCICTS) - San Diego, CA, USA (2018.10.15-2018.10.17)] 2018 IEEE BiCMOS and Compound Semiconductor Integrated Circuits and Technology Symposium (BCICTS) - 450 GHz <tex>$f_{\text{T}}$</tex> SiGe:C HBT Featuring an Implanted Collector in a 55-nm CMOS Node
摘要： This paper deals with the optimization of a Si/SiGe HBT featuring an implanted collector and a DPSA-SEG emitter-base architecture. Arsenic and phosphorous doping species are studied. On the one hand, both silicon defects and dopants profiles control are evaluated and on the other hand, hf performances are presented. Carbon-phosphorous co-implantation is also investigated and a state-of-the-art 450 GHz fT HBT compatible with 55-nm MOSFETs is demonstrated through a device layout study.
关键词： MOSFET,Implanted Collector,Heterojunction Bipolar Transistor (HBT),Silicon-Defects
更新于2025-09-04 15:30:14
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In <sub/>0.49</sub> Ga <sub/>0.51</sub> P/GaAs heterojunction bipolar transistors (HBTs) on 200 mm Si substrates: Effects of base thickness, base and sub-collector doping concentrations
摘要： We report performance of InGaP/GaAs heterojunction bipolar transistors (HBTs) fabricated on epitaxial films directly grown onto 200 mm silicon (Si) substrates using a thin 100% germanium (Ge) buffer layer. Both buffer layer and device layers were grown epitaxially using metalorganic chemical vapor deposition (MOCVD). With the assistance of numerical simulation, we were able to achieve high performance GaAs HBTs with DC current gain of ～100 through optimizing the base doping concentration (C-doped, ～ 1.9×1019/cm3), base layer thickness (～55 nm), and the sub-collector doping concentration (Te-doped, > 5×1018/cm3). The breakdown voltage at base (BV ceo) of higher than 9.43 V was realized with variation of < 3% across the 200 mm wafer. These results could enable applications such as power amplifiers for mobile phone handsets and monolithic integration of HBTs with standard Si-CMOS transistors on a common Si platform.
关键词： InGaP/GaAs heterojunction bipolar transistors,base doping concentrations,base thickness,Si substrates,HBTs,sub-collector doping concentrations
更新于2025-09-04 15:30:14