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Atomistic mechanisms of the initial oxidation of stepped Cu3Au(100)

Physical Review B 2022年第7期105卷 075422-075422页

作者： Yaguang Zhu Dongxiang Wu Chaoran Li Xiao Tong J. Anibal Boscoboinik Jerzy T. Sadowski Guangwen Zhou Department of Mechanical Engineering & Materials Science and Engineering Program State University of New York Binghamton New York 13902 USA Center for Functional Nanomaterials Brookhaven National Laboratory Upton New York 11973 USA

Alloy oxidation is complex and involves several critical processes that lack understanding on the atomic level. Here, we report an atomistic picture of the initial-stage oxidation of stepped Cu3Au(100) using a combination of surface science tools and modeling to illuminate the microscopic processes underlying oxygen-adsorption-induced structural and compositional changes. Pristine Cu3Au(100) consists of wide CuAu-terminated terraces and narrow Cu-terminated terraces separated by monatomic steps. Counterintuitive to the common expectations of the adsorbate-induced surface segregation of the more reactive alloy component, our observations demonstrate that the oxygen adsorption leads to the exfoliation of the outermost CuAu layer, thereby exposing the inner Cu plane to O attack. This occurs via the oxygen-assisted abstraction of Au and Cu atoms from step edges and CuAu terraces, which generates many Cu adatoms aggregating into Cu clusters and Au adatoms dissolving into the bulk. The oxygen adsorption onto fourfold hollow sites of the exposed Cu plane results in nucleation and growth of the c(2×2)−O superstructure, which can be fit well by the Johnson-Mehl-Avrami-Kolmogorov theory with a site-saturated nucleation mechanism.

关键词： Surface & interfacial phenomena Alloys Surfaces Density functional theory Ion beam analysis Scanning tunneling microscopy X-ray photoelectron spectroscopy

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Enhancing Pharmaceutical Wastewater Treatment: Ozone-Assisted Electrooxidation and Precision Optimization Via Response Surface Methodology

SSRN

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SSRN 2023年

作者： Phan, Huy N.Q. Leu, Jyh Hoang Nguyen, Vi N.D. Department of Materials Science and Engineering Feng Chia University Taichung40744 Taiwan Master’s Program of Green Energy Science and Technology Feng Chia University Taichung40744 Taiwan Department of Chemical Engineering Feng Chia University Taichung40744 Taiwan

In this study, the treatment of pharmaceutical wastewater was conducted using electrooxidation (EO) and ozone-assisted electrooxidation (EO/O3) with Pt-coated Ti electrodes (Pt/Ti). The removal of chemical oxygen demand (COD), color, and the UV absorption peak at 300 nm (UV300) was investigated in a batch mode reactor. Highly significant quadratic regression models for both processes were revealed through experimental design and optimization using the Box-Behnken Design (BBD) methodology. Current density, initial pH, and electrolysis time were assigned as independent variables for the statistical models. Under optimal conditions of 110.63 A m−2 current density and an initial pH of 4.5 for 477 minutes, stand-alone electrooxidation achieved the removal of 70.5% of COD, 81.25% color reduction, and a 40.01% decrease in UV300. In contrast, ozone-assisted electrooxidation performed even more effectively, with the removal of 84% for COD, 99.43% for color, and 49.63% for UV300. These results were obtained under optimal conditions of 150 A m−2 current density and an initial pH of 8.79 for 480 minutes. In addition, positive results in the kinetic study also gave this study an appeal. It was seen that ozone-assisted electrooxidation is an effective method for the pharmaceutical wastewater treatment. © 2023, The Authors. All rights reserved.

关键词： Ozone

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Effect of surface segregation on the oxidation resistance of Cu3Pt(100)

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Physical Review materials 2022年第2期6卷 025801-025801页

作者： Chaoran Li Yaguang Zhu Dongxiang Wu Jorge Anibal Boscoboinik Guangwen Zhou Department of Mechanical Engineering and Materials Science and Engineering Program State University of New York at Binghamton New York 13902 USA Center for Functional Nanomaterials Brookhaven National Laboratory Upton New York 11973 USA

Alloying element segregation often occurs under a reactive environment but its interplay with the subsequent surface oxidation of the alloy remains unclear. Using synchrotron-based ambient-pressure x-ray photoelectron spectroscopy, we dynamically monitor the surface segregation in Cu3Pt(100) in response to temperature and oxygen gas. Vacuum annealing leads to surface segregation of Cu along with the enrichment of Pt in the subsurface region. Upon switching to the O2 atmosphere, dissociative chemisorption of oxygen does not change the surface segregation profile from that under the vacuum annealing condition. A stepwise increase in the oxygen pressure results in the transformation pathway of Cu→Cu2O→CuO, in which the selective oxidation of Cu gives rise to further accumulation of Pt underneath the oxide/alloy interface that hinders the supply of Cu from the bulk to the oxide/alloy interface, thereby leading to the termination of the surface oxidation after the Cu2O→CuO conversion is completed. This differs from the transformation pathway of Cu→Cu2O→Cu2O/CuO for the oxidation of pure Cu and Cu-Au alloys, in which the oxidation of Cu continues and the Cu2O/CuO bilayer growth is constantly maintained. These key differences provide useful insight into alloy design for controlling the surface properties such as corrosion resistance and catalytic performance of Cu base alloys.

关键词： Surface & interfacial phenomena Alloys X-ray photoelectron spectroscopy

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Evolution of 14-connected Zr₆ Secondary Building Units through Postsynthetic Linker Incorporation (Jun, 10.1021/acsami.1c07701, 2021)

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ACS APPLIED materials & INTERFACES 2021年第33期13卷 40155-40155页

作者： Hurlock, Matthew J. Hao, Leiduan Kriegsman, Kyle W. Guo, Xiaofeng O'Keeffe, Michael Zhang, Qiang Department of Chemistry Washington State University Pullman Washington 99164 United States Department of Chemistry Materials Science and Engineering Program Washington State University Pullman Washington 99164 United States School of Molecular Sciences Arizona State University Tempe Arizona 85287 United States

Two new zirconium MOFs, WSU-6 and WSU-7, were synthesized through postsynthetic modifications. In both cases, linker insertion was conducted on a MOF consisting of eight-connected (8-c) Zr6cluster and four-connected (4-c) ETTC linker, WSU-5, which possesses the uncommon 4, 8-cscu-ctopology. The insertion of 1, 4-benzenedicarboxylate into the MOF formed the new 4, 12-cmjhtopology, WSU-6. Interestingly, when 2, 6-naphthalenedicarboxylate was inserted, WSU-7 can be formed, which possesses a new 4, 14-cjkztopology. WSU-7 contains very rare 14-c Zr6secondary building units (SBUs) and is the first MOF to have a Zr6SBUs with connectivity greater than 12. The three Zr-MOFs were structurally characterized, and the photoluminescence properties of the materials were also studied.

关键词： 14-connected Zr6 SBU luminescence metal−organic frameworks new topology postsynthetic ligand insertion

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Opto2P-FCM: A MEMS Based Miniature Two-Photon Microscope with Patterned Optogenetic Stimulation

Opto2P-FCM: A MEMS Based Miniature Two-Photon Microscope wit...

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Microscopy Histopathology and Analytics, Microscopy 2024 - Part of Optica Biophotonics Congress: Biomedical Optics

作者： Futia, Gregory L. Zohrabi, Mo McCullough, Connor Teel, Alec de Souza, Fabio Simoes Oroke, Ryan Bright, Victor M. Restrepo, Diego Gopinath, Juliet T. Gibson, Emily A. Department of Bioengineering University of Colorado Anschutz Medical Campus AuroraCO80045 United States Department of Cell and Developmental Biology University of Colorado Anschutz Medical Campus AuroraCO80045 United States Department of Electrical Computer and Energy Engineering University of Colorado BoulderCO80309 United States Department of Mechanical Engineering University of Colorado BoulderCO80309 United States Department of Physics University of Colorado BoulderCO80309 United States Materials Science and Engineering Program University of Colorado BoulderCO80309 United States

Miniaturized microscopes for monitoring neural activity are an indispensable tool for neuroscience research. We present a novel MEMS based miniature microscope with patterned optogenetic stimulation capabilities enabl... 详细信息

ISBN: (纸本)9781957171340

关键词： Microscopes

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On the origin of anomalous hysteresis in graphite/boron nitride transistors

arXiv

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arXiv 2024年

作者： Waters, Dacen Waleffe, Derek Thompson, Ellis Arreguin-Martinez, Esmeralda Fonseca, Jordan Poirier, Thomas Edgar, James H. Watanabe, Kenji Taniguchi, Takashi Xu, Xiaodong Cobden, David Yankowitz, Matthew Department of Physics University of Washington SeattleWA98195 United States Intelligence Community Postdoctoral Research Fellowship Program University of Washington SeattleWA98195 United States Department of Materials Science and Engineering University of Washington SeattleWA98195 United States Tim Taylor Department of Chemical Engineering Kansas State University Durland Hall ManhattanKS United States Research Center for Electronic and Optical Materials National Institute for Materials Science 1-1 Namiki Tsukuba305-0044 Japan Research Center for Materials Nanoarchitectonics National Institute for Materials Science 1-1 Namiki Tsukuba305-0044 Japan

Field-effect devices constructed by stacking flakes of van der Waals (vdW) materials, with hexagonal boron nitride (hBN) playing the role of gate dielectric, often exhibit virtually no hysteresis in their characteristics. This permits exquisitely detailed studies of diverse gate-voltage-tuned phenomena in vdW devices. Recently, however, a dramatic form of gate hysteresis, sometimes called the "gate doesn't work" (GDW) or "electron ratchet" effect, has been seen in certain individual vdW devices that seem otherwise unexceptional [1-10]. When it occurs, this hysteresis phenomenon is striking and robust, yet it is difficult to reliably reproduce between devices and, largely as a result, its origin remains disputed. Most devices where it has been seen have a bilayer graphene channel and nominal rotational alignment between the graphene and hBN, which has engendered explanations based on properties of bilayer graphene combined with moiré effects [1, 2, 6]. Here, we report our studies of the phenomenon observed in devices that have multilayer graphene channels. We find that the effect can occur in devices with graphite channels that have many more than two graphene layers, in which case it is unambiguously associated with just one surface of the graphite. It can also survive to room temperature, occur in the absence of intentional rotational alignment with hBN, persist when a monolayer of WSe2 is inserted between the graphene and hBN, and exhibit continuous relaxation on timescales of hours or longer. These observations impose strong constraints on the origin of this puzzling phenomenon, which has exciting potential applications if it can be mastered [4, 10, 11]. Copyright © 2024, The Authors. All rights reserved.

关键词： Van der Waals forces

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Layer-dependent optically induced spin polarization in InSe

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Physical Review B 2023年第11期107卷 115304-115304页

作者： Jovan Nelson Teodor K. Stanev Dmitry Lebedev Trevor LaMountain J. Tyler Gish Hongfei Zeng Hyeondeok Shin Olle Heinonen Kenji Watanabe Takashi Taniguchi Mark C. Hersam Nathaniel P. Stern Applied Physics Program Northwestern University Evanston Illinois 60208 USA Department of Physics and Astronomy Northwestern University Evanston Illinois 60208 USA Department of Material Science and Engineering Northwestern University Evanston Illinois 60208 USA Computational Science Division Argonne National Laboratory Lemont Illinois 60439 USA Material Science Division Argonne National Laboratory Lemont Illinois 60439 USA Research Center for Functional Materials National Institute for Materials Science 1-1 Namiki Tsukuba 305-0044 Japan International Center for Materials Nanoarchitectonics National Institute for Materials Science 1-1 Namiki Tsukuba 305-0044 Japan Department of Chemistry Northwestern University Evanston Illinois 60208 USA Department of Electrical Engineering and Computer Science Northwestern University Evanston Illinois 60208 USA

Optical control of spin in semiconductors has been pioneered using nanostructures of III-V and II-VI semiconductors, but the emergence of two-dimensional van der Waals materials offers an alternative low-dimensional platform for spintronic phenomena. Indium selenide (InSe), a group-III monochalcogenide van der Waals material, has shown promise for optoelectronics due to its high electron mobility, tunable direct band gap, and quantum transport. In addition to these confirmed properties, there are predictions of spin-dependent optical selection rules, suggesting the potential for all-optical excitation and control of spin in a two-dimensional layered material. Despite these predictions, layer-dependent optical spin phenomena in InSe have yet to be explored. Here, we present measurements of layer-dependent optical spin dynamics in few-layer and bulk InSe. Polarized photoluminescence reveals layer-dependent optical orientation of spin, thereby demonstrating the optical selection rules in few-layer InSe. Spin dynamics are also studied in many-layer InSe using time-resolved Kerr rotation spectroscopy. By applying out-of-plane and in-plane static magnetic fields for polarized emission measurements and Kerr measurements, respectively, the g factor for InSe was extracted. Further investigations are done by calculating precession values using a k·p model, which is supported by ab initio density functional theory. Comparison of predicted precession rates with experimental measurements highlights the importance of excitonic effects in InSe for understanding spin dynamics. Optical orientation of spin is an important prerequisite for optospintronic phenomena and devices, and these first demonstrations of layer-dependent optical excitation of spins in InSe lay the foundation for combining layer-dependent spin properties with advantageous electronic properties found in this material.

关键词： Magneto-optics Spin dynamics Chalcogenides Layered semiconductors Van der Waals systems Density functional theory Kerr effect Photoluminescence k dot p method

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Direct observation of structural phase transformations during continuous phosphorus deposition on Cu(111)

arXiv

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arXiv 2024年

作者： David, Jiří Jeřábek, František Procházka, Pavel Černý, Miroslav Ciobanu, Cristian V. Průša, Stanislav Šikola, Tomáš Kodambaka, Suneel Kolíbal, Miroslav Institute of Physical Engineering Brno University of Technology Technická 2 Brno616 69 Czech Republic CEITEC BUT. Brno University of Technology Purkyňova 123 Brno612 00 Czech Republic Department of Mechanical Engineering Materials Science Program Colorado School of Mines GoldenCO80401 United States Department of Materials Science and Engineering Virginia Polytechnic Institute State University BlacksburgVA24061 United States

Blue phosphorene - two-dimensional, hexagonal-structured, semiconducting phosphorus - has gained attention as it is considered easier to synthesize on metal surfaces than its allotrope, black phosphorene. Recent studies report different structures of phosphorene, for example, on Cu(111), but the underlying mechanisms of their formation are not known. Here, using a combination of in situ ultrahigh vacuum low-energy electron microscopy and in vacuo scanning tunneling microscopy, we determine the time-evolution of the surface structure and morphology during the deposition of phosphorus on single-crystalline Cu(111). We find that during early stages of deposition, phosphorus intermixes with Cu, resulting in copper phosphide structures. With increasing surface concentration of phosphorus, the phosphide phase disappears and a blue phosphorene layer forms, followed by self-assembly of highly ordered phosphorus clusters that eventually grow into multilayer islands. We attribute the unexpected transformation of stable phosphide to a phosphorene layer, and the previously unreported multilayer growth, to the presence of a large concentration of P2 dimers on the surface. Our results constitute direct evidence for a new growth mode leading to a phosphorene layer via an intermediary phase, which could underpin the growth of other 2D materials on strongly interacting substrates. © 2024, CC BY-SA.

关键词： Self assembly

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The effect of the addition of alumina on the viscosity, surface tension, and foaming efficiency of 2.5(CaO/SiO2)-xAl2O3-yFeO-MgO melts

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Ceramics International 2023年第13期49卷 21994-22003页

作者： Chang, Yu-En Lin, Chi-Ming Shen, Jyun-Ming Luo, Shao-Feng Yu, Kai-Wen Wu, Weite Department of Materials Science and Engineering National Chung Hsing University 145 Xingda Rd South Dist Taichung City40227 Taiwan WEI CHIH STEEL INDUSTRIAL CO. LTD No.123 Nanbu Guantian Dist. Tainan City720006 Taiwan Academy of Circular Economy Industrial and Intelligent Technology Program National Chung Hsing University No. 15 Guangming Rd. Nantou County 540 Taiwan

Viscosity and surface tension strongly influence the efficiency of slag foam in metallurgical processes. An excellent foaming slag preserves heat and lowers the cost of smelting in an electric furnace. In this study, we investigated the viscosity, surface tension, and foaming efficiency of a 2.5CaO/SiO2-xAl2O3-yFeO-MgO slag. We also investigated the different valence oxygen ions by X-ray photoelectron spectroscopy (XPS). The results showed that with a gradual increase in the content of Al2O3, the viscosity initially increased and then decreased, and the changes in surface tension followed a similar pattern. The change in viscosity was caused by the increase in the degree of polymerization of the slag, which was determined by the competitive relationship between polymerization and the reduction in the stability of the overall network structure. Adding a small amount of Al2O3 to the slag slightly increased the number of Al–O–Al structures, whereas adding a large amount of the Al2O3 led to the formation of low-strength Al–O–Si structures, which reduced the stability of the network structure, thus reducing the viscosity. Because the surface tension is related to the concentration of non-bridging oxygens (NBOs), when the NBO content increased, the instability of the surface structure caused an increase in energy, thus increasing the surface tension. In addition, the CaO–SiO2–5MgO-xAl2O3-yFeO five-element oxide in this study had the lowest surface tension at the same NBO concentration, which positively contributed to slag foaming. Finally, When the Al2O3 content in the system increased from 5.1 to 15.7 wt%, the foaming efficiency increased from 24.2 to 69.2 (minute‧centimeters), an increase of 286%. © 2023 Elsevier Ltd and Techna Group S.r.l.

关键词： Silica

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Concurrent weak localization and double Schottky barrier across a grain boundary in bicrystal SrTiO3

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Physical Review B 2023年第10期107卷 104401-104401页

作者： M. Egilmez S. El-Khatib F. Mustafa S. Ahmad A. Di Bernardo J. W. A. Robinson Department of Physics American University of Sharjah Sharjah PO Box 26666 United Arab Emirates Materials Science and Engineering Program American University of Sharjah Sharjah PO Box 26666 United Arab Emirates Department of Physics University of Konstanz 78457 Konstanz Germany Department of Materials Science & Metallurgy University of Cambridge Cambridge CB3 0FS United Kingdom

Stoichiometric SrTiO3 (STO) is a wide band-gap insulator in which oxygen deficiency generates a low-temperature metallic ferromagnetic state. Here, we report weak ferromagnetic-like and metallic transport in oxygen-deficient bicrystal of STO with a low-temperature electron mobility and surface carrier density of 2800cm2V−1s−1 and 3.500×1016cm−2, respectively. Moreover, we show that magnetotransport behavior in the bulk and across the grain boundary (GB) in STO single crystals are significantly different. In the bulk, our magnetotransport results agree with those reported in the literature. Importantly, low-temperature magnetotransport across the GB shows a disorder-induced metal-insulator transition, and it is modeled as a quasi–two-dimensional system below 10 K that accounts for weak localization (WL), supported by electron-electron, electron-phonon, and Hikami-Larkin-Nagaoka (HLN) quantum interference models. The HLN model accounts for realistic length scales: the dephasing length Lϕ, and the spin-orbit (SO) scattering length LSO, which are comparable to the electron mean-free path, resembling the surface-conducting nature across the GB. Our experimental work shows the importance of structural defects in the interpretation of magnetotransport in SrTiO3 and shows that WL is concurrent with a double Schottky barrier at the GB interface.

关键词： Charge Electrical conductivity Localization Magnetic interactions Magnetism

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