| 1. |
- Dong, Yu, et al.
(author)
-
Observation of a Ubiquitous (π, π)-Type Nematic Superconducting Order in the Whole Superconducting Dome of Ultra-Thin BaFe2–xNixAs2 Single Crystals
- 2021
-
In: Chinese Physics Letters. - : Institute of Physics Publishing (IOPP). - 0256-307X .- 1741-3540. ; 38:9
-
Journal article (peer-reviewed)abstract
- In iron-based superconductors, the (0, pi) or (pi, 0) nematicity, which describes an electronic anisotropy with a four-fold symmetry breaking, is well established and believed to be important for understanding the superconducting mechanism. However, how exactly such a nematic order observed in the normal state can be related to the superconducting pairing is still elusive. Here, by performing angular-dependent in-plane magnetoresistivity using ultra-thin flakes in the steep superconducting transition region, we unveil a nematic superconducting order along the (pi, pi) direction in electron-doped BaFe2 - x Ni x As2 from under-doped to heavily overdoped regimes with x = 0.065-0.18. It shows superconducting gap maxima along the (pi, pi) direction rotated by 45 degrees from the nematicity along (0, pi) or (pi, 0) direction observed in the normal state. A similar (pi, pi)-type nematicity is also observed in the under-doped and optimally doped hole-type Ba1 - y K y Fe2As2, with y = 0.2-0.5. These results suggest that the (pi, pi) nematic superconducting order is a universal feature that needs to be taken into account in the superconducting pairing mechanism in iron-based superconductors.
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| 2. |
- Duan, Ningyuan, et al.
(author)
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Reduction of NiGe/n- and p-Ge Specific Contact Resistivity by Enhanced Dopant Segregation in the Presence of Carbon During Nickel Germanidation
- 2016
-
In: IEEE Transactions on Electron Devices. - : IEEE. - 0018-9383 .- 1557-9646. ; 63:11, s. 4546-4549
-
Journal article (peer-reviewed)abstract
- This brief explores the specific contact resistivity (rho(c)) of NiGe/n- and p-Ge contacts with and without carbon pregermanidation implantation. It is found that in the presence of carbon, not only the thermal stability of NiGe films is improved, but also the rho(c) of the NiGe/n- and p-Ge contacts is reduced remarkably due to enhanced phosphorus (P) and boron (B) dopant segregation (DS) at the NiGe/Ge interface after nickel germanidation. At 500 degrees C germanidation temperature, the.c values are reduced from 1.1 x 10(-4) Omega-cm(2) and 2.9 x 10(-5) Omega-cm(2) for NiGe/n- and p-Ge contacts without carbon to 7.3 x 10(-5) Omega-cm(2) and 1.4 x 10(-5) Omega-cm(2) for their counterparts with carbon, respectively.
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| 3. |
- Li, Junjie, et al.
(author)
-
A Novel Dry Selective Isotropic Atomic Layer Etching of SiGe for Manufacturing Vertical Nanowire Array with Diameter Less than 20 nm
- 2020
-
In: Materials. - : MDPI AG. - 1996-1944. ; 13:3
-
Journal article (peer-reviewed)abstract
- Semiconductor nanowires have great application prospects in field effect transistors and sensors. In this study, the process and challenges of manufacturing vertical SiGe/Si nanowire array by using the conventional lithography and novel dry atomic layer etching technology. The final results demonstrate that vertical nanowires with a diameter less than 20 nm can be obtained. The diameter of nanowires is adjustable with an accuracy error less than 0.3 nm. This technology provides a new way for advanced 3D transistors and sensors.
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| 4. |
- Guo, Pengzhi, et al.
(author)
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Twisted Alkylthiothien-2-yl Flanks and Extended Conjugation Length Synergistically Enhanced Photovoltaic Performance by Boosting Dielectric Constant and Carriers Kinetic Characteristics
- 2021
-
In: Macromolecular Chemistry and Physics. - : Wiley. - 1022-1352 .- 1521-3935. ; 222:12
-
Journal article (peer-reviewed)abstract
- Alternating conjugated polymers (CPs), derived from 2-ethylhexylthiothiophen-2-yl (TS) or 2-ethylhexylthiophen-2-yl (T) flanked dithieno[3,2-d:3,2-d ']benzo[1,2-b:4,5-b ']dithiophene (DTBDT) and diketopyrrolo-pyrrole (DPP) termed as PDTBDT-TS-DPP and PDTBDT-T-DPP, are prepared and characterized. It is found that the PDTBDT-TS-DPP not only exhibits slightly deepening the highest occupied molecular orbital energy levels, and similar absorption, etc., but also presents higher dielectric constant (epsilon(r)) of 6.7 at 1 kHz in contrast to 3.2 for PDTBDT-T-DPP, which are even higher than those of 4.3 and 3.0 for PBDT-TS-DPP/PBDT-T-DPP generated from TS and T flanked benzo[1,2-b:4,5-bMODIFIER LETTER PRIME]dithiophene and DPP. Beyond that, the power conversion efficiency of 8.17% for the inverted photovoltaic devices from DPP-based CPs, is achieved from PDTBDT-TS-DPP. The alkylthio side chains are used in the DTBDT of the larger twisting angles of TS flanks and longer conjugation length, synergistically contribute to the highest dipole moments, and then lead to the enhancement of epsilon(r), thus devoted the modification exciton dissociation and charge carriers kinetic characteristics. To the authors' knowledge, it is the first time to report that epsilon(r) of the CPs is connected with the twisting angle of flanks and conjugation length of the building blocks, besides the use of functional side chains and atoms.
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| 5. |
- Liu, Yi, et al.
(author)
-
Effect of fluorine atoms on optoelectronic, aggregation and dielectric constants of 2,1,3-benzothiadiazole-based alternating conjugated polymers
- 2021
-
In: Dyes and Pigments. - : Elsevier BV. - 0143-7208 .- 1873-3743. ; 193
-
Journal article (peer-reviewed)abstract
- Three 2,1,3-benzothiadiazole-based conjugated copolymers named PBDT-0F-BTs, PBDT-2F-BTs and PBDT-6F-FBTs, which were derived from 4,8-bis(4,5-dioctylthiophen-2-yl)benzo[1,2-b:4,5-b′]dithiophene and (3,4′-bis(2-hexyl- decyl)-2,2′-dithiophene-5-yl) substituted 2,1,3-benzothiadiazole and/or 5,6-difluoro- 2,1,3-benzothiadiazole derivatives with 2,2′-dithiophene and/or 3,3′-difluoro- 2,2′-dithiophene as π-linkers, were prepared and characterized. The copolymers PBDT-0F-BTs, PBDT-2F-BTs and PBDT-6F-FBTs exhibited the highest occupied molecular orbital (HOMO) and lowest unoccupied orbital (LUMO) energy levels of −5.38 eV/−3.57 eV, −5.45 eV/−3.65 eV and −5.55 eV/−3.78 eV, with the light response from 300 nm to 720–750 nm, alongside with the similar aggregation, except that the charge transporting mobilities were successively increased, and the dielectric constants were gradually improved from 3.3 to 4.8 to 5.9 at 1 KHz, while the fluorine atoms in the each repeat unit of polymers were varied from 0 to 2 and then up to 6, respectively. Beyond that, it has also been found that the power conversion efficiencies and exciton dissociation probability (P(E,T)) of the bulk heterojunction organic photovoltaic cells (BHJ-OPVs) from the blend films of polymers paired with Y6 (2,2'-((2Z,2'Z)-((12,13-bis(2-ethylhexyl)-3,9-diundecyl12,13-dihydro[1,2,5]thia- diazolo[3,4-e]thieno[2'',3'':4',5']thieno[2',3':4,5]pyrrolo[3,2-g]thieno[2',3':4,5]thieno[3,2-b]indole-2,10-diyl)bis(methanylylidene))bis(5,6-difluoro-3-oxo-2,3-dihydro-1H-ind-ene-2,1-diylidene))dimalononitrile), were varied from 7.83% and 85.9%, to 9.22% and 90.2% and then up to 12.34% and 91.4%. The results indicated that the continuous insertion of the fluorine atoms into the repeat units of the conjugated polymers would result in the consecutively deepening the HOMO energy levels, increase dielectric constants and charge mobilities, thus devote to the enhancement of the P(E,T) and the performance of the BHJ-OPVs.
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| 6. |
- Wang, Guilei, et al.
(author)
-
Growth of SiGe layers in source and drain regions for 10 nm node complementary metal-oxide semiconductor (CMOS)
- 2020
-
In: Journal of materials science. Materials in electronics. - : Springer Science and Business Media LLC. - 0957-4522 .- 1573-482X. ; 31, s. 26-33
-
Journal article (peer-reviewed)abstract
- In this study, the integration of Si 1−x Ge x (50% ≤ x ≤ 60%) selective epitaxy on source/drain regions in 10 nm node FinFET has been presented. One of the major process issues was the sensitivity of Si-fins’ shape to ex- and in-situ cleaning prior to epitaxy. For example, the sharpness of Si-fins could easily be damaged during the wafer washing. The results showed that a DHF dip before the normal cleaning, was essential to clean the Si-fins while in-situ annealing in range of 780–800 °C was needed to remove the native oxide for high epitaxial quality. Because of smallness of fins, the induced strain by SiGe could not be directly measured by X-ray beam in a typical XRD tool in the lab or even in a Synchrotron facility. Further analysis using nano-beam diffraction technique in high-resolution transmission electron microscope also failed to provide information about strain in the FinFET structure. Therefore, the induced strain by SiGe was simulated by technology computer-aided design program and the Ge content was measured by using energy dispersive spectroscopy. Simulation results showed 0.8, 1 and 1.3 GPa for Ge content of 40%, 50% and 60%, respectively. A kinetic gas model was also introduced to predict the SiGe profile on Si-fins with sharp triangular shape. The input parameters in the model includes growth temperature, partial pressure of the reactant gases and the exposed Si coverage in the chip area.
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| 7. |
- Wang, Guilei, et al.
(author)
-
Study of SiGe selective epitaxial process integration with high-k and metal gate for 16/14 nm nodes FinFET technology
- 2016
-
In: Microelectronic Engineering. - : Elsevier. - 0167-9317 .- 1873-5568. ; 163, s. 49-54
-
Journal article (peer-reviewed)abstract
- In this study, the process integration of SiGe selective epitaxy on source/drain regions, for 16/14 nm nodes FinFET with high-k & metal gate has been presented. Selectively grown Si1-xGex (0.35 <= x <= 0.40) with boron concentration of 1 x 10(20) cm(-3) was used to elevate the source/drain of the transistors. The epi-quality, layer profile and strain amount of the selectively grown SiGe layers were also investigated by means of various characterizations. A series of prebaking experiments were performed for temperatures ranging from 740 to 825 degrees C in order to in situ clean the Si fins prior to the epitaxy. The results showed that the thermal budget needs to be limited to 780-800 degrees C in order to avoid any damages to the shape of Si fins but to remove the native oxide effectively which is essential for high epitaxial quality. The Ge content in SiGe layers on Si fins was determined from the strain measured directly by reciprocal space mappings using synchrotron radiation. Atomic layer deposition technique was applied to fill the gate trench with W using WF6 and B2H6 precursors. By such an AID approach, decent growth rate, low resistivity and excellent gap filling capability of W in pretty high aspect-ratio gate trench was realized. The as-fabricated FinFETs demonstrated decent electrical characteristics.
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| 8. |
- Wang, Xiaolin, et al.
(author)
-
Comprehension of the Effect of a Hydroxyl Group in Ancillary Ligand on Phosphorescent Property for Heteroleptic Ir(III) Complexes : A Computational Study Using Quantitative Prediction
- 2017
-
In: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 56:15, s. 8986-8995
-
Journal article (peer-reviewed)abstract
- A new Ir(III) complex (dfpypya)(2)Ir(pic-OH) (2) is theoretically designed by introduction of a simple hydroxyl group into the ancillary ligand on the basis of (dfpypya)(2)Ir(pic) (1) with the aim to get the high efficiency and stable blue-emitting phosphors, where dfpypya is 3-methyl-6-(2',4'-difluoro-pyridinato)pyridazine, pic is picolinate, and pic OH is 3-hydroxypicolinic acid. The other configuration (dfpypya)(2)Ir(pic OH)' (3) is also investigated to compare with 2. The difference between 2 and 3 is whether the intramolecular hydrogen bond is formed in the (dfpypya)(2)Ir(pic OH). The quantum yield is determined by three different methods including the semiquantitative and quantitative methods. To quantitatively determine the quantum yield is still not an easy task to be completed. This work would provide some useful advices to select the suitable method to reliably evaluate the quantum yield. Complex 2 has larger quantum yield and more stability as compared with 1 and 3. The formation of intramolecular hydrogen bond would become a new method to design new phosphor with the desired properties.
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| 9. |
- Xiong, Wenjuan, et al.
(author)
-
SiNx films and membranes for photonic and MEMS applications
- 2020
-
In: Journal of materials science. Materials in electronics. - : Springer Science and Business Media LLC. - 0957-4522 .- 1573-482X. ; 31, s. 90-97
-
Journal article (peer-reviewed)abstract
- This work presents a novel process to form SiN x films and process for membranes with excellent mechanical properties for micro-electro-mechanical systems application as well as integration as IR waveguide for photonic application. The SiN x films were fabricated in SiNgen apparatus which is a single wafer chamber equipment compared to conventional low pressure chemical vapor deposition furnace process. The films showed low stress, good mechanical properties, but the synthesis also eradicates the issues of particle contamination. Through optimizing of the growth parameters and post annealing profile, low stress (40 Mpa) SiN x film could be finally deposited when annealing temperature rose up to 1150 °C. The stress relaxation is a result of more Si nano-crystalline which was formed during annealing, according to the FTIR results. The mechanical properties, Young’s modulus and hardness, were 210 Gpa and 20 Gpa respectively. For the waveguide application, a stack of three layers, SiO 2 /SiN x /SiO 2 was formed where the optimized layer thicknesses were used for minimum optical loss according to simulation feedback. After deposition of the first two layers in the stack, the samples were annealed in range of 900–1150 °C in order to release the stress. Chemical mechanical polish technique was applied to planarize the nitride layer prior to the oxide cladding layer. Such wafers can be used to bond to Si or Ge to manufacture advanced substrates.
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| 10. |
- Bao, Qinye, et al.
(author)
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Regular Energetics at Conjugated Electrolyte/Electrode Modifier for Organic Electronics and Their Implications of Design Rules
- 2015
-
In: Advanced Materials Interfaces. - : John Wiley & Sons. - 2196-7350. ; 2:12, s. 1-6
-
Journal article (peer-reviewed)abstract
- Regular energetics at a conjugated electrolyte/electrode modifier are found and controlled by equilibration of the Fermi level and an additional interface double dipole step induced by ionic functionality. Based on the results, design rules for conjugated electrolyte/electrode modifiers to achieve the smallest charge injection/exaction barrier and break through the current thickness limitation are proposed.
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| 11. |
- Cao, Kequan, et al.
(author)
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Constructing ZnTe Spherical Quantum Well for Efficient Light Emission
- 2024
-
In: Nano Letters. - 1530-6984. ; 24:17, s. 5238-5245
-
Journal article (peer-reviewed)abstract
- ZnTe colloidal semiconductor nanocrystals (NCs) have shown promise for light-emitting diodes (LEDs) and displays, because they are free from toxic heavy metals (Cd). However, so far, their low photoluminescence (PL) efficiency (∼30%) has hindered their applications. Herein, we devised a novel structure of ZnTe NCs with the configuration of ZnSe (core)/ZnTe (spherical quantum well, SQW)/ZnSe (shell). The inner layer ZnTe was grown at the surface of ZnSe core with avoiding using highly active and high-risk Zn sources. Due to the formation of coherently strained heterostructure which reduced the lattice mismatch, and the thermodynamic growth of ZnTe, the surface or interface defects were suppressed. A high PL efficiency of >60% was obtained for the green light-emitting ZnSe/ZnTe/ZnSe SQWs after ZnS outer layer passivation, which is the highest value for colloidal ZnTe-based NCs. This work paves the way for the development of novel semiconductor NCs for luminescent and display applications.
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| 12. |
- Chen, Anqi, et al.
(author)
-
Highly Sensitive Graphene Oxide-based Fabry-Perot Low-frequency Acoustic Sensor With Low-coherence Polarized Demodulation Using Three-step Phase-Shifting Arctan Algorithms
- 2024
-
In: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; In Press
-
Journal article (peer-reviewed)abstract
- Developing low-frequency acoustic senor with high sensitivity is crucial for diverse applications, ranging from seismic monitoring, military operations, to pipeline surveillance. Here, we have proposed a high-sensitivity graphene oxide (GO)-based Fabry-Perot low-frequency sensor, in which a 170 nm thick, large-area and uniformly GO film was prepared by a vacuum filtration method. To enhance the accuracy and stability of the sensor, a low-coherence interference system based on birefringent crystal blocks was designed utilizing a three-step phase-shifting arctangent algorithm. Our sensor exhibited a sensitivity of -93.48 dB re 1 rad/μPa at 6-60 Hz with a fluctuation of 0.6 dB. The minimum detectable pressure of the sensor was measured at 0.37 μPa/Hz1/2 @20 Hz with a signal to noise ratio of 135.41 dB. Overall, this sensor offers simplicity in preparation, high sensitivity, low detectable sound pressure, making it a significant asset for low-frequency acoustic applications.
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| 13. |
- Chen, Zhuoying, et al.
(author)
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Enhanced charge transport by incorporating additional thiophene units in the poly(fluorene-thienyl-benzothiadiazole) polymer
- 2011
-
In: Organic electronics. - : Elsevier. - 1566-1199 .- 1878-5530. ; 12:3, s. 461-471
-
Journal article (peer-reviewed)abstract
- We report a comparative study of optical properties, structure and morphology, field-effect transistor (FET) and solar cell performance between poly(4-(3,4-dihexyl-2,2-bithiophen-5-yl)-7-(5-(9,9-dioctyl-9H-fluoren-2-yl)-3,4-dihexyl-2,2-bithiophen-5-yl)benzo[c][1,2,5]-thiadiazole) (F8TTBTT), and its predecessor poly((9,9-dioctylfluorene)-2,7-diyl-alt[4,7-bis(3-hexylthien-5-yl)-2,1,3-benzothiadiazole]-2,2 -diyl) (F8TBT). Compared to F8TBT, F8TTBTT has two more thiophene units incorporated in its monomer structure. Such a modification leads to a reduced optical band gap, improved charge injection and significantly enhanced ambipolar field-effect mobilities reaching 5 x 10 (2) cm(2) V (1) s (1) for holes and 4 x 10 (3) cm(2) V (1) s (1) for electrons. The enhanced carrier mobilities are most likely a result of an increased backbone planarization and interchain interaction. As a consequence of ambipolar transport, light-emission was observed from the transistor channel during operation. The reduced band gap and improved charge transport make F8TTBTT an interesting candidate also for solar cell applications. Unoptimized solar cells based on F8TTBTT: PCBM blends were found to exhibit power conversion efficiency under AM 1.5 illumination of similar to 1.54%. (C) 2011 Published by Elsevier B.V.
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| 14. |
- Cheng, Yu, et al.
(author)
-
The Disk Population in a Distant Massive Protocluster
- 2022
-
In: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 940:2
-
Journal article (peer-reviewed)abstract
- The unprecedented angular resolution and sensitivity of the Atacama Large Millimeter/submillimeter Array make it possible to unveil disk populations in distant (>2 kpc), embedded young cluster environments. We have conducted an observation toward the central region of the massive protocluster G286.21+0.16 at 1.3 mm. With a spatial resolution of 23 mas and a sensitivity of 15 mu Jy beam(-1), we detect a total of 38 protostellar disks. These disks have dust masses ranging from about 53 to 1825 M (circle plus), assuming a dust temperature of 20 K. This sample is not closely associated with previously identified dense cores, as would be expected for disks around Class 0 protostars. Thus, we expect our sample, being flux-limited, to be mainly composed of Class I/flat-spectrum source disks, since these are typically more massive than Class II disks. Furthermore, we find that the distributions of disk masses and radii are statistically indistinguishable from those of the Class I/flat-spectrum objects in the Orion molecular cloud, indicating that similar processes are operating in G286.21+0.16 to regulate disk formation and evolution. The cluster center appears to host a massive protostellar system composed of three sources within 1200 au, including a potential binary with 600 au projected separation. Relative to this center, there is no evidence for widespread mass segregation in the disk population. We do find a tentative trend of increasing disk radius versus distance from the cluster center, which may point to the influence of dynamical interactions being stronger in the central regions.
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| 15. |
- Fan, Zhaozhong, et al.
(author)
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Oxygen-Bridged Indium-Nickel Atomic Pair as Dual-Metal Active Sites Enabling Synergistic Electrocatalytic CO2 Reduction
- 2023
-
In: Angewandte Chemie International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 62:7
-
Journal article (peer-reviewed)abstract
- Single-atom catalysts offer a promising pathway for electrochemical CO2 conversion. However, it is still a challenge to optimize the electrochemical performance of dual-atom catalysts. Here, an atomic indium-nickel dual-sites catalyst bridged by an axial oxygen atom (O-In-N6-Ni moiety) was anchored on nitrogenated carbon (InNi DS/NC). InNi DS/NC exhibits superior CO selectivity with Faradaic efficiency higher than 90 % over a wide potential range from −0.5 to −0.8 V versus reversible hydrogen electrode (vs. RHE). Moreover, an industrial CO partial current density up to 317.2 mA cm−2 is achieved at −1.0 V vs. RHE in a flow cell. In situ ATR-SEIRAS combined with theory calculations reveal that the synergistic effect of In-Ni dual-sites and O atom bridge not only reduces the reaction barrier for the formation of *COOH, but also retards the undesired hydrogen evolution reaction. This work provides a feasible strategy to construct dual-site catalysts towards energy conversion.
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| 16. |
- Feng, Chen, et al.
(author)
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Estimating E-Scooter Traffic Flow Using Big Data to Support Planning for Micromobility
- 2022
-
In: The Journal of urban technology. - : Informa UK Limited. - 1063-0732 .- 1466-1853. ; 29:2, s. 139-157
-
Journal article (peer-reviewed)abstract
- Dockless e-scooter sharing, as a new shared micromobility service, has quickly gained popularity in recent years. In this paper, we present a practical approach to estimating e-scooter flow patterns without knowing the actual routes taken by the e-scooter riders. Our method takes advantage of a huge open dataset that contains the origins and destinations of millions of trips. We show that our models can help cities better support the emerging shared micromobility service. The additional information generated in the modeling process can also be useful for a more refined analysis of e-scooter trips.
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| 17. |
- Guo, Xuewen, et al.
(author)
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Novel small-molecule zwitterionic electrolyte with ultralow work function as cathode modifier for inverted polymer solar cells
- 2018
-
In: Organic electronics. - : ELSEVIER SCIENCE BV. - 1566-1199 .- 1878-5530. ; 59, s. 15-20
-
Journal article (peer-reviewed)abstract
- Interfacial compatibility between the electrode and organic semiconductor plays a critical role in controlling the charge transport and hence efficiency of organic solar cell. Here, we introduce a novel small-molecule zwitterionic electrolyte (S1) combined with ZnO as electron transporting interlayer employed for the inverted PTB7:PC71BM bulk heterojunction solar cell. The resulting device with the S1/ZnO stacked interlayer achieves a high PCE of 8.59%, obtaining a 16.2% improvement over the control device performance of 7.4% without the S1 attributed to the significant increased short-circuit current density and fill factor. The interfacial properties are investigated. It is found that the S1/ZnO interlayer possess an ultralow work function of 3.6 eV, which originates from the interfacial double dipole step induced by the zwitterionic side chain electrostatic realignment at interface. The S1/ZnO interlayer exhibits the excellent charge extraction ability, suppresses the charge recombination loss and decreases the series resistance at the active layer/electrode contact.
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| 18. |
- Huang, Zheng, et al.
(author)
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Constructing type-II CuInSe2/CuInS2 core/shell quantum dots for high-performance photoelectrochemical cells
- 2024
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In: SCIENCE CHINA Materials. - 2095-8226. ; 67:1, s. 134-142
-
Journal article (peer-reviewed)abstract
- CuInSe2 (CISe) quantum dots (QDs) have shown promising applications in photoelectrochemical (PEC) cells due to their nontoxicity, high extinction coefficient, and wide optical absorption range; however, their low PEC performance prevents their applications due to insufficient charge carrier separation and severe charge recombination. Herein, CISe/CuInS2 (CISe/CIS) core/shell structured QDs are designed and constructed to promote charge separation and diminish interface defects. Afterward, the copper vacancy (VCu) state of CISe/CIS QDs is enriched by modulating the precursor molar ratios of In/Cu. Therefore, the radiative recombination of the conduction band edge electrons with the VCu localized holes becomes dominant and prolongs the carrier lifetime compared with intrinsic band-to-band recombination, thus promoting charge separation. Consequently, the VCu-rich CISe/CIS QD-based photoanode shows a high photocurrent density of 8.0 mA cm−2, which is one of the highest values reported for CISe QD-based PEC cells. This work provides an effective approach for promoting charge carrier separation and transfer through surface or intrinsic defect mediation for PEC applications of I–III–VI semiconductor nanocrystals.
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| 19. |
- Lan, Lei, et al.
(author)
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Medial ElasticsElastics: Efficient and Collision-Ready Deformation via Medial Axis Transform
- 2020
-
In: ACM Transactions on Graphics. - : Association for Computing Machinery (ACM). - 1557-7368 .- 0730-0301. ; 39:3
-
Journal article (peer-reviewed)abstract
- We propose a framework for the interactive simulation of nonlinear deformable objects. The primary feature of our system is the seamless integration of deformable simulation and collision culling, which are often independently handled in existing animation systems. The bridge connecting them is the medial axis transform (MAT), a high-fidelity volumetric approximation of complex 3D shapes. From the physics simulation perspective, MAT leads to an expressive and compact reduced nonlinear model. We employ a semireduced projective dynamics formulation, which well captures high-frequency local deformations of high-resolution models while retaining a low computation cost. Our key observation is that the most compelling (nonlinear) deformable effects are enabled by the local constraints projection, which should not be aggressively reduced, and only apply model reduction at the global stage. From the collision detection (CD)/collision culling (CC) perspective, MAT is geometrically versatile using linear-interpolated spheres (i.e., the so-called medial primitives (MPs)) to approximate the boundary of the input model. The intersection test between two MPs is formulated as a quadratically constrained quadratic program problem. We give an algorithm to solve this problem exactly, which returns the deepest penetration between a pair of intersecting MPs. When coupled with spatial hashing, collision (including self-collision) can be efficiently identified on the GPU within a few milliseconds even for massive simulations. We have tested our system on a variety of geometrically complex and high-resolution deformable objects, and our system produces convincing animations with all of the collisions/self-collisions well handled at an interactive rate.
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| 20. |
- Li, Xiaodong, et al.
(author)
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Critical role of the external bias in improving the performance of polymer solar cells with a small molecule electrolyte interlayer
- 2015
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In: Journal of Materials Chemistry A. - : Royal Society of Chemistry. - 2050-7488 .- 2050-7496. ; 3:2, s. 504-508
-
Journal article (peer-reviewed)abstract
- A small-molecule electrolyte based on the popular ethylene diamine tetraacetic acid (EDTA-N) is introduced as an efficient cathode interlayer in inverted polymer solar cells, helping to deliver power conversion efficiency over 9%. The strong dependence of device performance on the external bias suggests that the ion motion plays a critical role in improving the performance of devices with electrolyte interlayers.
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| 21. |
- Li, Xiaodong, et al.
(author)
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Disodium Edetate As a Promising Interfacial Material for Inverted Organic Solar Cells and the Device Performance Optimization
- 2014
-
In: ACS Applied Materials and Interfaces. - : American Chemical Society. - 1944-8244 .- 1944-8252. ; 6:23, s. 20569-20573
-
Journal article (peer-reviewed)abstract
- Disodium edetate (EDTA-Na), a popular hexadentate ligand in analytical chemistry, was successfully introduced in organic solar cells (OSCs) as cathode interfacial layer. The inverted OSCs with EDTA-Na showed superior performance both in power conversion efficiency and devices stability compared with conventional devices. Interestingly, we found that the performance of devices with EDTA-Na could be optimized through external bias treatment. After optimization, the efficiency of inverted OSCs with device structure of ITO/EDTA-Na/polymer thieno[3,4-b]thiophene/benzodithiophene (PTB7):PC71BM/MoO3/Al was significantly increased to 8.33% from an initial value of 6.75%. This work introduces a new class of interlayer materials, small molecule electrolytes, for organic solar cells.
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| 22. |
- Li, Xiaodong, et al.
(author)
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The effect of external electric field on the performance of perovskite solar cells
- 2015
-
In: Organic electronics. - : Elsevier. - 1566-1199 .- 1878-5530. ; 18, s. 107-112
-
Journal article (peer-reviewed)abstract
- Planar heterojunction perovskite solar cells were fabricated through a low temperature approach. We find that the device performance significantly depends on the external bias before and during measurements. By appropriate optimization of the bias conditions, we could achieve an 8-fold increase in the power conversion efficiency. The significant improvement in device performance might be caused by the ion motion in the perovskite under the external electric field.
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| 23. |
- Liu, Jinbiao, et al.
(author)
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Study of n-type doping in germanium by temperature based PF+ implantation
- 2020
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In: Journal of materials science. Materials in electronics. - : Springer Science and Business Media LLC. - 0957-4522 .- 1573-482X. ; 31, s. 161-166
-
Journal article (peer-reviewed)abstract
- Incorporation of P in germanium was studied by using PF+ molecular implantation in a range from room temperature to 400 °C. The presence of F acted as a barrier for P in-diffusion and resulted in higher activation of P at room temperature. In addition, it is found that when the implantation is performed at 400 °C, the residual defects are stable and the diffusion of P can be blocked during activation annealing. Therefore, the final junction depth could be well controlled by the implantation process itself. This method is meaningful for the shallow junction formation in sub 14-nm Ge-based FinFETs or high-performance photodetectors.
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| 24. |
- Luo, Jun, et al.
(author)
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Effects of carbon pre-silicidation implant into Si substrate on NiSi
- 2014
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In: Microelectronic Engineering. - : Elsevier BV. - 0167-9317 .- 1873-5568. ; 120, s. 178-181
-
Journal article (peer-reviewed)abstract
- In this work, the effects of carbon pre-silicidation implant into Si(1 0 0) substrate on NiSi were investigated. NiSi films with carbon pre-silicidation implant to different doses were characterized by means of sheet resistance measurements, X-ray diffraction, scanning electron microscopy (SEM), planar view transmission electron microscopy (TEM) and second ion mass spectroscopy (SIMS). The presence of C is found to indeed significantly improve the thermal stability of NiSi as well as tends to change the preferred orientations of polycrystalline NiSi. The homogeneously distributed C at NiSi grain boundaries and C peak at NiSi/Si interface is ascribed to the improved thermal stability of NiSi. More importantly, the dose of carbon pre-silicidation implant also plays a key role in the formation of NiSi, which is suggested not to exceed a critical value about 5 x 10(15) cm(-2) in practical application in accordance with the results achieved in this work. (C) 2013 Elsevier B.V. All rights reserved.
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| 25. |
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| 26. |
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| 27. |
- Luo, Jun, et al.
(author)
-
Variation of Schottky barrier height induced by dopant segregation monitored by contact resistivity measurements
- 2014
-
In: Microelectronic Engineering. - : Elsevier BV. - 0167-9317 .- 1873-5568. ; 120, s. 174-177
-
Journal article (peer-reviewed)abstract
- Change of contact resistivity (rho(c)) is monitored for evaluation of Schottky barrier height (SBH) variation induced by dopant segregation (DS). This method is particularly advantageous for metal-semiconductor contacts of small SBH, as it neither requires low-temperature measurement needed in current-voltage characterization of Schottky diodes nor is affected by reverse leakage current often troubling capacitance-voltage characterization. With PtSi contact to both n- and p-type diffusion regions, and the use of opposite or alike dopants implant into pre-formed PtSi films followed by drive-in anneal at different temperatures to induce DS at PtSi/Si interface, the formation of interfacial dipole is confirmed as the responsible cause for modification of effective SBHs thus the increase or decrease of rho(c). A tentative explanation for the change of contact resistivity based on interfacial dipole theory is provided in this work. Influences and interplay of interfacial dipole and space charge on effective SBH are also discussed. (C) 2013 Elsevier B.V. All rights reserved.
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| 28. |
- Miao, Junfeng, et al.
(author)
-
A blockchain-enabled privacy-preserving authentication management protocol for Internet of Medical Things
- 2024
-
In: Expert systems with applications. - Oxford : Elsevier. - 0957-4174 .- 1873-6793. ; 237, Part A
-
Journal article (peer-reviewed)abstract
- Over the last decade, with the increasing popularity and usage of the internet of things worldwide, Internet of Medical Things (IoMT) has emerged as a key technology of the modern era. IoMT uses Artificial Intelligence, 5G, big data, edge computing, and blockchain to provide users with electronic medical services. However, it may face several security threats and attacks over an insecure public network. Therefore, to protect sensitive medical data in IoMT, it is necessary to design a secure and efficient authentication protocol. In this study, we propose a privacy-preserving authentication management protocol based on blockchain. The protocol uses a blockchain to store identities and related parameters to assist communication entities in authentication. In addition, the protocol adopts a three-factor authentication method and introduces Chebyshev chaotic map to ensure the security of user login and authentication. Formal security proof and analysis using the random oracle model and Burrows-Abadi-Needham logic show that the proposed protocol is secure. Moreover, we use informal security analysis to demonstrate that the protocol can resist various security attacks. The functional comparison shows that the protocol has high security. Through performance analysis and comparison with other protocols, the proposed protocol can increase computation overhead, communication overhead, and storage overhead by up to 39.8%, 93.6%, and 86.7%,respectively. © 2023 Elsevier Ltd
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| 29. |
- Qin, Changliang, et al.
(author)
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Impact of pattern dependency of SiGe layers grown selectively in source/drain on the performance of 14 nm node FinFETs
- 2016
-
In: Solid-State Electronics. - : Elsevier. - 0038-1101 .- 1879-2405. ; 124, s. 10-15
-
Journal article (peer-reviewed)abstract
- A complete mapping of 14 nm FinFETs performance over 200 mm wafers was performed and the pattern dependency of SiGe selective growth was calculated using an empirical kinetic molecule model for the reactant precursors. The transistor structures were analyzed by conventional characterization tools and their performance was simulated by considering the process related variations. The applied model presents for the first time a powerful tool for transistor community to predict the SiGe profile and strain modulating over a processed wafer, independent of wafer size.
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| 30. |
- Qin, Changliang, et al.
(author)
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Process optimizations to recessed e-SiGe source/drain for performance enhancement in 22 nm all-last high-k/metal-gate pMOSFETs
- 2016
-
In: Solid-State Electronics. - : Elsevier. - 0038-1101 .- 1879-2405. ; 123, s. 38-43
-
Journal article (peer-reviewed)abstract
- In this paper, the technology of recessed embedded SiGe (e-SiGe) source/drain (S/D) module is optimized for the performance enhancement in 22 nm all-last high-k/metal-gate (HK/MG) pMOSFETs. Different Si recess-etch techniques were applied in S/D regions to increase the strain in the channel and subsequently, improve the performance of transistors. A new recess-etch method consists of a two-step etch method is proposed. This process is an initial anisotropic etch for the formation of shallow trench followed by a final isotropic etch. By introducing the definition of the upper edge distance (D) between the recessed S/D region and the channel region, the process advantage of the new approach is clearly presented. It decreases the value of D than those by conventional one-step isotropic or anisotropic etch of Si. Therefore, the series resistance is reduced and the channel strain is increased, which confirmed by the simulation results. The physical reason of D reducing is analyzed in brief. Applying this recess design, the implant conditions for S/D extension (SDE) are also optimized by using a two-step implantation of BF2 in SiGe layers. The overlap space between doping junction and channel region has great effect on the device's performance. The designed implantation profile decreases the overlap space while keeps a shallow junction depth for a controllable short channel effect. The channel resistance as well as the transfer ID-VG curves varying with different process conditions are demonstrated. It shows the drive current of the device with the optimized SDE implant condition and Si recess-etch process is obviously improved. The change trend of on-off current distributions extracted from a series of devices confirmed the conclusions. This study provides a useful guideline for developing high performance strained PMOS SiGe technology.
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| 31. |
- Wang, Chen, et al.
(author)
-
Identification of the Origin for Reconstructed Active Sites on Oxyhydroxide for Oxygen Evolution Reaction
- 2023
-
In: Advanced Materials. - : Wiley. - 0935-9648 .- 1521-4095. ; 35:6
-
Journal article (peer-reviewed)abstract
- The regulation of atomic and electronic structures of active sites plays an important role in the rational design of oxygen evolution reaction (OER) catalysts toward electrocatalytic hydrogen generation. However, the precise identification of the active sites for surface reconstruction behavior during OER remains elusive for water-alkali electrolysis. Herein, irreversible reconstruction behavior accompanied by copper dynamic evolution for cobalt iron layered double hydroxide (CoFe LDH) precatalyst to form CoFeCuOOH active species with high-valent Co species is reported, identifying the origin of reconstructed active sites through operando UV-Visible (UV–vis), in situ Raman, and X-ray absorption fine-structure (XAFS) spectroscopies. Density functional theory analysis rationalizes this typical electronic structure evolution causing the transfer of intramolecular electrons to form ligand holes, promoting the reconstruction of active sites. Specifically, unambiguous identification of active sites for CoFeCuOOH is explored by in situ 18O isotope-labeling differential electrochemical mass spectrometry (DEMS) and supported by theoretical calculation, confirming mechanism switch to oxygen-vacancy-site mechanism (OVSM) pathway on lattice oxygen. This work enables to elucidate the vital role of dynamic active-site generation and the representative contribution of OVSM pathway for efficient OER performance.
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| 32. |
- Wang, Guilei, et al.
(author)
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Integration of Highly Strained SiGe in Source and Drain with HK and MG for 22 nm Bulk PMOS Transistors
- 2017
-
In: Nanoscale Research Letters. - : Springer. - 1931-7573 .- 1556-276X. ; 12
-
Journal article (peer-reviewed)abstract
- In this study, the integration of SiGe selective epitaxy on source/drain regions and high-k and metal gate for 22 nm node bulk pMOS transistors has been presented. Selective Si1-xGex growth (0.35 <= x <= 0.40) with boron concentration of 1-3 x 10(20) cm(-3) was used to elevate the source/drain. The main focus was optimization of the growth parameters to improve the epitaxial quality where the high-resolution x-ray diffraction (HRXRD) and energy dispersive spectrometer (EDS) measurement data provided the key information about Ge profile in the transistor structure. The induced strain by SiGe layers was directly measured by x-ray on the array of transistors. In these measurements, the boron concentration was determined from the strain compensation of intrinsic and boron-doped SiGe layers. Finally, the characteristic of transistors were measured and discussed showing good device performance.
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| 33. |
- Wang, Guilei, et al.
(author)
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Integration of highly-strained SiGe materials in 14 nm and beyond nodes FinFET technology
- 2015
-
In: Solid-State Electronics. - : Elsevier BV. - 0038-1101 .- 1879-2405. ; 103, s. 222-228
-
Journal article (peer-reviewed)abstract
- SiGe has been widely used as stressors in source/drain (S/D) regions of Metal-Oxide-Semiconductor Field Effect Transistor (MOSFET) to enhance the channel mobility. In this study, selectively grown Si1-xGex (0.33 <= x <= 0.35) with boron concentration of 1 x 10(20) cm(-3) was used to elevate the S/D regions on bulk FinFETs in 14 nm technology node. The epitaxial quality of SiGe layers, SiGe profile and the strain amount of the SiGe layers were investigated. In order to in-situ clean the Si-fins before SiGe epitaxy, a series of prebaking experiments at temperature ranging from 740 to 825 degrees C were performed. The results showed that the thermal budget needs to be limited to 780-800 degrees C in order to avoid any damage to the shape of Si-fins but to remove the native oxide which is essential for high epitaxial quality. In this study, a kinetic gas niodel was also applied to predict the SiGe growth profile on Si-fins with trapezoidal shape. The input parameters for the model include growth temperature, partial pressures of reactant gases and the chip layout. By knowing the epitaxial profile, the strain to the Si-fins exerted by SiGe layers can be calculated. This is important in understanding the carrier transport in the FinFETs. The other benefit of the modeling is that it provides a cost-effective alternative for epitaxy process development as the SiGe profile can be readily predicted for any chip layout in advance.
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| 34. |
- Wang, Guilei, et al.
(author)
-
pMOSFETs Featuring ALD W Filling Metal Using SiH4 and B2H6 Precursors in 22 nm Node CMOS Technology
- 2017
-
In: Nanoscale Research Letters. - : SPRINGER. - 1931-7573 .- 1556-276X. ; 12
-
Journal article (peer-reviewed)abstract
- In this paper, pMOSFETs featuring atomic layer deposition (ALD) tungsten (W) using SiH4 and B2H6 precursors in 22 nm node CMOS technology were investigated. It is found that, in terms of threshold voltage, driving capability, carrier mobility, and the control of short-channel effects, the performance of devices featuring ALD W using SiH4 is superior to that of devices featuring ALD W using B2H6. This disparity in device performance results from different metal gate-induced strain from ALD W using SiH4 and B2H6 precursors, i.e. tensile stresses for SiH4 (similar to 2.4 GPa) and for B2H6 (similar to 0.9 GPa).
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| 35. |
- Yang, Huiqing, et al.
(author)
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Protic Quaternary Ammonium Ionic Liquids for Catalytic Conversion of CO2 into Cyclic Carbonates : A Combined Ab Initio and MD Study
- 2018
-
In: Industrial & Engineering Chemistry Research. - : AMER CHEMICAL SOC. - 0888-5885 .- 1520-5045. ; 57:21, s. 7121-7129
-
Journal article (peer-reviewed)abstract
- The mechanism of CO2 fixation catalyzed by protic hydroxyl-functionalized quaternary ammonium ionic liquids (ILs) is investigated by two different models, the Single-IL model and the Double-IL model. The relative sequence of catalytic activity calculated by the Single-IL model is contradictory with the experimental result. The situation is totally varied when the Double-IL model is utilized. In this system, ILs are not limited to the catalyst but solvent. The ILs are incorporated into the catalytic system to consider the solvent effect rather than by the existing solvent model. When the solvent effect is included, it is better to distinguish the catalytic activity of three ILs. According to the noncovalent interaction and the atoms in molecules analysis, the highest catalytic activity of tris(2-hydroxyethyl)ammonium bromide ([HTEA]Br) is attributed to its strongest nucleophilic attack and moderate hydrogen bond interaction between IL and reactant. It is necessary to consider the interaction between ILs to get a reliable result. Moreover, the solvent effect aroused by ILs should be carefully considered.
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| 36. |
- Yang, Tao, et al.
(author)
-
A survey of distributed optimization
- 2019
-
In: Annual Reviews in Control. - : PERGAMON-ELSEVIER SCIENCE LTD. - 1367-5788 .- 1872-9088. ; 47, s. 278-305
-
Research review (peer-reviewed)abstract
- In distributed optimization of multi-agent systems, agents cooperate to minimize a global function which is a sum of local objective functions. Motivated by applications including power systems, sensor networks, smart buildings, and smart manufacturing, various distributed optimization algorithms have been developed. In these algorithms, each agent performs local computation based on its own information and information received from its neighboring agents through the underlying communication network, so that the optimization problem can be solved in a distributed manner. This survey paper aims to offer a detailed overview of existing distributed optimization algorithms and their applications in power systems. More specifically, we first review discrete-time and continuous-time distributed optimization algorithms for undirected graphs. We then discuss how to extend these algorithms in various directions to handle more realistic scenarios. Finally, we focus on the application of distributed optimization in the optimal coordination of distributed energy resources.
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| 37. |
- Yao, Yao, et al.
(author)
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The effect of China's Clean Air Act on cognitive function in older adults : a population-based, quasi-experimental study
- 2022
-
In: Lancet Healthy Longevity. - 2666-7568. ; 3:2, s. e98-e108
-
Journal article (peer-reviewed)abstract
- Background Air pollution might accelerate cognitive ageing; it is unclear whether large-scale interventions, such as China's Clean Air Act (CCAA), can mitigate cognitive deterioration. We aimed to evaluate the effect of CCAA on changes in cognitive function in older adults.Methods In this population-based, quasi-experimental study, we did a difference-in-differences analysis of the data collected during the 2014 and 2018 waves of the Chinese Longitudinal Healthy Longevity Survey (CLHLS). The study design used a counterfactual analysis feature by dividing CLHLS participants into two groups. The intervention group included participants who lived in areas where the provincial government set a target of reducing particulate matter (PM) by at least 5% annually from 2014 onward, whereas the control group consisted of individuals who lived in areas without a PM reduction target. Global cognitive function was measured using the Mini-Mental State Examination (MMSE). We used fixed-effects models to examine the between-group differences in MMSE score changes before and after CCAA implementation. We associated longitudinal changes in MMSE scores with changes in concentrations of PM with a diameter of less than 2·5 μm (PM2·5) concentration and other regulated pollutants. We used alternative models and sensitivity analyses to evaluate the robustness of the results from the main models.Findings 2812 individuals participated in the 2014 and 2018 surveys (mean age 81·0 years [SD 9·3] in 2014; 1408 [50·1%] female and 1404 [49·9%] male). 2251 (80·0%) were included in the intervention group and 561 (20·0%) in the control group. After controlling for potential confounders, the intervention group had a significantly smaller decline in MMSE scores from 2014 to 2018 compared with the control group: the mean between-group difference was 2·45 points (95% CI 1·32–3·57). Interquartile increases in PM2·5 were associated with a significant MMSE score decline of 0·83 points (95% CI 0·24–1·42); similarly, increases in SO2 were also associated with a significant MMSE score decline of 0·80 points (0·32–1·29).Interpretation Implementing stringent clean air policies might mitigate the risk of air pollutant-associated cognitive ageing in older people.
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| 38. |
- Yu, Hanbo, et al.
(author)
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An X-Ray View of Two Infrared Dark Clouds G034.43+00.24 and G035.39-00.33
- 2020
-
In: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 905:1
-
Journal article (peer-reviewed)abstract
- We present a high spatial resolution Chandra X-ray study of two infrared dark clouds (IRDCs), G034.43+00.24 and G035.39-00.33, which are expected to be in the early phases of star cluster formation. We detect 112 and 209 valid X-ray point sources toward G034.43+00.24 and G035.39-00.33, respectively. We cross-match the X-ray point sources with the Two Micron All Sky Survey (2MASS), Galactic Legacy Infrared Midplane Survey Extraordinaire (GLIMPSE), and Wide-field Infrared Survey Explorer (WISE) catalogs and find 53% and 59% of the X-ray sources in G034.43+00.24 and in G035.39-00.33 have corresponding infrared counterparts, respectively. These sources are probable members of young massive clusters in formation, and using stellar isochrones we estimate that a population of 1-2 Myr old, intermediate- to high-mass young stellar objects (YSOs) exist in both IRDCs. Two and 10 Class II counterparts to X-ray sources were identified in G034.43+00.24 and in G035.39-00.33, respectively, which are located in or near dark filaments. The X-ray luminosity function (XLF) of G035.39-00.33 implies that the total mass consists of up to similar to 1700M of stars, using the XLF of the well-studied Orion Nebula Cluster as a calibrator. This corresponds to a star formation efficiency of at most 5%, indicating the system is still very much gas dominated and in an early stage of the star formation process. The population of G034.43+00.24 is less well determined due to the lower sensitivity of its observations.
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| 39. |
- Zhai, Panlong, et al.
(author)
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Engineering single-atomic ruthenium catalytic sites on defective nickel-iron layered double hydroxide for overall water splitting
- 2021
-
In: Nature Communications. - : Springer Nature. - 2041-1723. ; 12:1
-
Journal article (peer-reviewed)abstract
- Rational design of single atom catalyst is critical for efficient sustainable energy conversion. However, the atomic-level control of active sites is essential for electrocatalytic materials in alkaline electrolyte. Moreover, well-defined surface structures lead to in-depth understanding of catalytic mechanisms. Herein, we report a single-atomic-site ruthenium stabilized on defective nickel-iron layered double hydroxide nanosheets (Ru-1/D-NiFe LDH). Under precise regulation of local coordination environments of catalytically active sites and the existence of the defects, Ru-1/D-NiFe LDH delivers an ultralow overpotential of 18mV at 10mAcm(-2) for hydrogen evolution reaction, surpassing the commercial Pt/C catalyst. Density functional theory calculations reveal that Ru-1/D-NiFe LDH optimizes the adsorption energies of intermediates for hydrogen evolution reaction and promotes the O-O coupling at a Ru-O active site for oxygen evolution reaction. The Ru-1/D-NiFe LDH as an ideal model reveals superior water splitting performance with potential for the development of promising water-alkali electrocatalysts. Rational design of single atom catalyst is critical for efficient sustainable energy conversion. Single-atomic-site ruthenium stabilized on defective nickel-iron layered double hydroxide nanosheets achieve superior HER and OER performance in alkaline media.
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| 40. |
- Zhai, Panlong, et al.
(author)
-
Regulating electronic states of nitride/hydroxide to accelerate kinetics for oxygen evolution at large current density
- 2023
-
In: Nature Communications. - : Springer Nature. - 2041-1723. ; 14:1
-
Journal article (peer-reviewed)abstract
- Rational design efficient transition metal-based electrocatalysts for oxygen evolution reaction (OER) is critical for water splitting. However, industrial water-alkali electrolysis requires large current densities at low overpotentials, always limited by intrinsic activity. Herein, we report hierarchical bimetal nitride/hydroxide (NiMoN/NiFe LDH) array as model catalyst, regulating the electronic states and tracking the relationship of structure-activity. As-activated NiMoN/NiFe LDH exhibits the industrially required current density of 1000 mA cm(-2) at overpotential of 266 mV with 250 h stability for OER. Especially, in-situ electrochemical spectroscopic reveals that heterointerface facilitates dynamic structure evolution to optimize electronic structure. Operando electrochemical impedance spectroscopy implies accelerated OER kinetics and intermediate evolution due to fast charge transport. The OER mechanism is revealed by the combination of theoretical and experimental studies, indicating as-activated NiMoN/NiFe LDH follows lattice oxygen oxidation mechanism with accelerated kinetics. This work paves an avenue to develop efficient catalysts for industrial water electrolysis via tuning electronic states. Rational design of efficient electrocatalysts for oxygen evolution reaction is critical for water-alkali electrolysis. Here, the authors fabricate a NiMoN/NiFe layered double hydroxide and show the accelerated oxygen evolution kinetics are due to the heterointerface.
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| 41. |
- Zhang, Bo, et al.
(author)
-
Enriching Metal–Oxygen Species and Phosphate Modulating of Active Sites for Robust Electrocatalytical CO2 Reduction
- 2023
-
In: Advanced Materials. - : Wiley. - 0935-9648 .- 1521-4095. ; 35:46
-
Journal article (peer-reviewed)abstract
- Direct electrochemical reduction of CO2 (CO2RR) into value-added chemicals is a promising solution to reduce carbon emissions. The activity of CO2RR is influenced deeply by the reaction microenvironment and electronic properties of the catalysts. Herein, the surface PO43− anions are tuned to modulate the local microenvironment and the electronic properties of the indium-based catalyst with abundant metal–oxygen species enabling efficient electrochemical conversion of CO2 to HCOO−. Indium nanoparticles coupled with PO43− anions (PO43−-In NPs) achieve a high selectivity of HCOO− up to 91.4% at a low potential of −0.98 V versus reversible hydrogen electrode (versus RHE) and a high HCOO− partial current density of 279.3 mA cm−2 at −1.1 V versus RHE in the electrochemical flow cell. In situ and ex situ characterizations confirm the PO43− anions keep stable on the surface of indium during CO2RR, accelerating the generation of OCHO* intermediate. From density functional theory calculations, PO43− anions enrich the metal–oxygen species on the substrate to optimize the electronic structure of the catalysts and induce a local microenvironment with massive K+ ions on the interface, thus reducing the activation energy barrier of CO2RR.
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| 42. |
- Zhang, Xiaomeng, et al.
(author)
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Engineering Single-Atomic Ni-N-4-O Sites on Semiconductor Photoanodes for High-Performance Photoelectrochemical Water Splitting
- 2021
-
In: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 143:49, s. 20657-20669
-
Journal article (peer-reviewed)abstract
- Direct photoelectrochemical (PEC) water splitting is a promising solution for solar energy conversion; however, there is a pressing bottleneck to address the intrinsic charge transport for the enhancement of PEC performance. Herein, a versatile coupling strategy was developed to engineer atomically dispersed Ni-N-4 sites coordinated with an axial direction oxygen atom (Ni-N-4-O) incorporated between oxygen evolution cocatalyst (OEC) and semiconductor photoanode, boosting the photogenerated electron-hole separation and thus improving PEC activity. This state-ofthe-art OEC/Ni-N-4-O/BiVO4 photoanode exhibits a record high photo-current density of 6.0 mA cm(-2) at 1.23 V versus reversible hydrogen electrode (vs RHE), over approximately 3.97 times larger than that of BiVO4, achieving outstanding long-term photostability. From X- ray absorption fine structure analysis and density functional theory calculations, the enhanced PEC performance is attributed to the construction of single-atomic Ni-N-4-O moiety in OEC/BiVO4, facilitating the holes transfer, decreasing the free energy barriers, and accelerating the reaction kinetics. This work enables us to develop an effective pathway to design and fabricate efficient and stable photoanodes for feasible PEC water splitting application.
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| 43. |
- Zhang, Yanting, et al.
(author)
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Two-Dimensional Defective Boron-Doped Niobic Acid Nanosheets for Robust Nitrogen Photofixation
- 2021
-
In: ACS Nano. - : American Chemical Society (ACS). - 1936-0851 .- 1936-086X. ; 15:11, s. 17820-17830
-
Journal article (peer-reviewed)abstract
- Direct nitrogen photofixation is a feasible solution toward sustainable production of ammonia under mild conditions. However, the generation of active sites for solar-dirven nitrogen fixation not only limits the fundamental understanding of the relationship among light absorption, charge transfer, and catalytic efficiency but also influences the photocatalytic activity. Herein, we report two-dimensional boron-doped niobic acid nanosheets with oxygen vacancies (B-V-o-HNbO3 NSs) for efficient N-2 photofixation in the absence of any scavengers and cocatalysts. Impressively, B-V-o-HNbO3 NS as a model catalyst achieves the enhanced ammonia evolution rate of 170 mu mol g(cat)(-1) h(-1) in pure water under visible-light irradiation. The doublet coupling representing (NH4+)-N-15 in an isotopic labeling experiment and in situ infrared spectra confirm the reliable ammonia generation. The experimental analysis and density functional theory (DFT) calculations indicate that the strong synergy of boron dopant and oxygen vacancy regulates band structure of niobic acid, facilitates photogenerated charge transfer, reduces free energy barriers, accelerates reaction kinetics, and promotes the high rates of ammonia evolution. This work provides a general strategy to design active photocatalysts toward solar N-2 conversion.
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| 44. |
- Zheng, Qian, et al.
(author)
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Constructing InP/ZnSe Quantum Dots with Shell Gradient In3+ Doping for Photoelectrochemical Cells
- 2024
-
In: ACS Energy Letters. - 2380-8195. ; 9:5, s. 2358-2366
-
Journal article (peer-reviewed)abstract
- Environmentally friendly InP/ZnSe core/shell quantum dots (QDs) with high absorption coefficients and tunable band gaps have demonstrated great potential for photoelectrochemical (PEC) water splitting. However, the tightly bound excitonic feature by inherent type I band alignment tends to reduce the charge separation efficiency, limiting their PEC performance. Herein, we devised heterovalent In3+ gradient doping in the ZnSe shell of InP QD to construct core/shell structural InP/ZnSe-G-In QDs. The In3+ dopant increased the Fermi level of the ZnSe shell; thus continuous semiconductor homojunction and band bending were formed by gradient composition doping, which accelerates the exciton separation through the built-in electric field. As a result, the PEC cells based on such QDs exhibited high photocurrent density of 8.7 mA/cm2, demonstrating one of the highest values for the InP-based QDs PEC cells. This work provides an effective strategy for the application of type I band structure QDs in solar energy conversion.
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