Bi2Se3 is a topological insulator with metallic surface states residing in a large bulk bandgap. It is believed that Bi2Se3 gets additional n-type doping after exposure to atmosphere, thereby reducing the relative contribution of surface states in total conductivity. In this letter, transport measurements on Bi2Se3 nanoribbons provide additional evidence of such environmental doping process. Systematic surface composition analyses by X-ray photoelectron spectroscopy reveal fast formation and continuous growth of native oxide on Bi2Se3 under ambient conditions. In addition to n-type doping at the surface, such surface oxidation is likely the material origin of the degradation of topological surface states. Appropriate surface passivation or encapsulation may be required to probe topological surface states of Bi2Se3 by transport measurements.
Polyimides, due to their superior mechanical behavior at high temperatures, are used in a variety of applications that include aerospace, automobile and electronic packaging industries, as matrices for composites, as adhesives etc. In this paper, we extend our previous model in [S. Karra, K. R. Rajagopal, Modeling the non-linear viscoelastic response of high temperature polyimides, Mechanics of Materials, In press, doi:10.1016/j.mechmat.2010.09.006], to include oxidative degradation of these high temperature polyimides. Appropriate forms for the Helmholtz potential and the rate of dissipation …
Layered indium selenide (InSe), a new two-dimensional (2D) material with a hexagonal structure and semiconducting characteristic, is gaining increasing attention owing to its intriguing electronic properties. Here, by using first-principles calculations, we reveal that perfect InSe possesses a high chemical stability against oxidation, superior to MoS2. However, the presence of intrinsic Se vacancy (VSe) and light illumination can markedly affect the surface activity. In particular, the excess electrons associated with the exposed In atoms at the VSe site under illumination are able to remarka…
Nonylphenol ethoxylate (NPE 10) is a non ionic surfactant which is synthesized from alkylphenol ethoxylate. The accumulation of NPE-10 in wastewater will endanger the ecosystem as well as human being. At present, by an advancement of technology NPE 10 can be degraded indirectly by using an electrochemically treatment. Thus, this study aimed to evaluate the potential electrodegradation of NPE 10 by mediated electrochemical oxidation (MEO) using Ce(IV) ionic mediator. In addition, the influence of Ag(I) ionic catalyst in the performance of MEO for degradation of NPE 10 was also observed. The pot…
We present a theoretical study of degradation mechanisms for photoinduced oxidation in organic polymers in the condensed phase, using poly(3-hexylthiophene)(P3HT) as an example. Applying density functional theory with a hybrid density functional and periodic boundary conditions that account for steric effects and permit the modeling of interchain chemical reactions, we investigate reaction pathways that may lead to the oxidation of thiophene backbone as a critical step toward disrupting the polymer conjugation. We calculate energy barriers for reactions of the P3HT backbone with oxidizing agen…
Black phosphorus is a monoatomic semiconducting layered material that degrades exothermically in the presence of light and ambient contaminants. Its degradation dynamics remain largely unknown. Even before degradation, local-probe studies indicate non-negligible local curvature --through a non-constant height distribution-- due to the unavoidable presence of intrinsic defects. We establish that these intrinsic defects are photo-oxidation sites because they lower the chemisorption barrier of ideal black phosphorus (> 10 eV and out of visible-range light excitations) right into the visible and u…
The effect of isothermal pre-oxidation treatments on the \b{eta}-(Ni,Pt)Al + René N5 system degradation is here reported. The oxidation treatments were carried out from 900 (mostly θ-Al2O3 growing conditions) to 1200°C (mainly α-Al2O3 growing conditions) for 5 h, under a purified Ar-stream with a fixed pO2= 1 x 10-5 atm. Results are discussed based on the correlation between the structural, microstructural and chemical properties of the \b{eta}-(Ni,Pt)Al BC showing that pre-oxidation parameters have an important effect on the multi-elemental counter diffusion phenomena along BC. For instance, …
The corrosion, mechanical degradation and biological performance of cold-drawn WE43 Mg wires were analyzed as a function of thermo-mechanical processing and the presence of a protective oxide layer created by continuous plasma electrolytic oxidation (PEO). It was found that the corrosion properties of the non-surface-treated wire could be optimized by means of thermal treatment within certain limits, but the corrosion rate remained very high. Hence, strength and ductility of these wires vanished after 24 h of immersion in simulated body fluid at 37$^\circ$C and, as a result of that rather quic…
Lead sulfide (PbS) quantum dot (QD) photovoltaics have reached impressive efficiencies of 12%, making them particularly promising for future applications. Like many other types of emerging photovoltaic devices, their environmental instability remains the Achilles heel of this technology. In this work, we demonstrate that the degradation processes in PbS QDs which are exposed to oxygenated environments are tightly related to the choice of ligands, rather than their intrinsic properties. In particular, we demonstrate that while 1,2-ethanedithiol (EDT) ligands result in significant oxidation of P…
Black Phosphorus (BP) is an excellent material for post graphene era due to its layer dependent band gap, high mobility and high Ion/Ioff. However, its poor stability in ambient poses a great challenge in its practical and long-term usage. Optical visualization of oxidized BP is the key and foremost step for its successful passivation from the ambience. Here, we have done a systematic study of the oxidation of BP and developed a technique to optically identify the oxidation of BP using Liquid Crystal (LC). Interestingly we found that rapid oxidation of thin layers of BP makes them disappear an…
Black phosphorus (BP) has attracted significant interest as a monolayer or few-layer material with extraordinary electrical and optoelectronic properties. However, degradation in air and other environments is an unresolved issue that may limit future applications. In particular the role of different ambient species has remained controversial. Here, we report systematic experiments combined with ab-initio calculations that address the effects of oxygen and water in the degradation of BP. Our results show that BP rapidly degrades whenever oxygen is present, but is unaffected by deaerated (i.e., …
Introduction of interstitial dopants has opened a new pathway to optimize nanoparticle catalytic activity for, e.g., hydrogen evolution/oxidation and other reactions. Here, we discuss the stability of a property-enhancing dopant, B, introduced through controlled synthesis of an electrocatalyst Pd aerogel. We observe significant removal of B after the hydrogen evolution/oxidation reaction. Ab-initio calculations show that the high stability of sub-surface B in Pd is substantially reduced when H is ad/absorbed on the surface, favoring its departure from the host nanostructure. The destabilizatio…
The doping dependence of dry thermal oxidation rates in n-type 4H-SiC was investigated. The oxidation was performed in the temperature range 1000C to 1200C for samples with nitrogen doping in the range of 6.5e15/cm3 to 9.3e18/cm3, showing a clear doping dependence. Samples with higher doping concentrations displayed higher oxidation rates. The results were interpreted using a modified Deal-Grove model. Linear and parabolic rate constants and activation energies were extracted. Increasing nitrogen led to an increase in linear rate constant pre-exponential factor from 10-6m/s to 10-2m/s and the …
Microstructure characterization is of great value to understanding nuclear graphite's properties and irradiation behavior. However, graphite is soft and could be easily damaged during sample preparation. A three-step polishing method involving mechanical polishing, ion milling and rapid oxidation is proposed for graphite. Ion milling is adopted to remove the broken graphite pieces produced by mechanical polishing. Rapid oxidation is then adopted to remove irradiation-induced damage layer during ion milling. The Raman spectra show very low G peak width and ID/IG ratio after rapid oxidation, ind…
A chemical nanomachining process for the rapid, scalable production of nanostructure assemblies from silicon-on-insulator is demonstrated. The process is based on the spontaneous, local oxidation of Si induced by Au, which is selectively evaporated onto the Si surface. The Au-catalyzed oxide forms a pattern that serves as a robust mask for the underlying Si, enabling the use of simple wet chemistry to sculpt arrays of nanostructures of diverse shapes including rings, pillars, wires, and nanopores. The remarkable simplicity of this chemical nanomachining process makes it widely accessible as an…
Zn nanoclusters (NCs) are deposited by Low-energy cluster beam deposition technique. The mechanism of oxidation is studied by analysing their compositional and morphological evolution over a long span of time (three years) due to exposure to ambient atmosphere. It is concluded that the mechanism proceeds in two steps. In the first step, the shell of ZnO forms over Zn NCs rapidly up to certain limiting thickness: with in few days -- depending upon the size -- Zn NCs are converted to Zn-ZnO (core-shell), Zn-void-ZnO, or hollow ZnO type NCs. Bigger than ~15 nm become Zn-ZnO (core-shell) type: amo…
The diffusion of superoxide radical anions on the surface of TiO2 catalysts is theoretically considered as an important step in the kinetics of photocatalytic oxidation of toxic pollutants. A detailed analysis is performed to discriminate the effects of rotation, anion and adsorption bonds vibrations on the diffusion coefficient. A resonant dependence of the diffusivity on the lattice parameters of the TiO2 surface is discovered showing that the most rapid diffusion takes place when the lattice parameters are twice larger than the bond length of the superoxide radical anions. Whereas the rotat…
Our recent modelling works and corresponding numerical simulations realized to describe the UO2 oxidation processes confirm the theory showing that an applied mechanical strain can strongly affect the local oxygen diffusion in a stressed solid. This result allows us to assume that stress field, previously applied at the surface of a metallic sample on several microns, will delay the degradation during its oxidation. Considering this hypothesis, we implemented a FEM simulation code developed in our laboratory to numerically investigate some different stress fields applied on a sample sub-surfac…
In our work, a novel processing strategy for the continuous fabrication and surface modification of wires from Magnesium alloy WE43 by means of plasma-electrolytic oxidation (PEO) is presented. In the first step, wires with a strong basal texture and small grain size ($\approx$ 1 $μ$m) were manufactured by combined cold drawing and in-line stress-relief heat treatment steps that optimized the mechanical properties (in terms of strength and ductility) by means of annealing. In a second step, and to the best of our knowledge for the first time ever, the wires were continuously surface-modified w…
The recent discovery of excellent thermoelectric properties and topological surface states in SnTe-based compounds has attracted extensive attention in various research areas. Indium doped SnTe is of particular interest because, depending on the doping level, it can either generate resonant states in the bulk valence band leading to enhanced thermoelectric properties, or induce superconductivity that coexists with topological states. Here we report on the vapor deposition of In-doped SnTe nanowires and the study of their surface oxidation and thermoelectric properties. The nanowire growth is a…
The binary alloy of titanium-tungsten (TiW) is an established diffusion barrier in high-power semiconductor devices, owing to its ability to suppress the diffusion of copper from the metallisation scheme into the surrounding silicon substructure. However, little is known about the response of TiW to high temperature events or its behaviour when exposed to air. Here, a combined soft and hard X-ray photoelectron spectroscopy (XPS) characterisation approach is used to study the influence of post-deposition annealing and titanium concentration on the oxidation behaviour of a 300~nm-thick TiW film.…
Decoherence in superconducting qubits has long been attributed to two level systems arising from the surfaces and interfaces present in real devices. A recent significant step in reducing decoherence was the replacement of superconducting niobium by superconducting tantalum, resulting in a tripling of transmon qubit lifetimes (T1). One of these surface variables, the identity, thickness, and quality of the native surface oxide, is thought to play a major role as tantalum only has one oxide whereas niobium has several. Here we report the development of a thermodynamic metric to rank materials b…
Synergistic Effects of Phosphorus Doping and Oxygen Vacancies on Formaldehyde Oxidation over CeO$_2$(111): A First Principles Investigation
Université de Lorraine（洛林大学）；CNRS（法国国家科学研究中心）；LEMTA（材料力学与转化实验室）；Université de Monastir（莫纳斯特尔大学）；Faculté des Sciences de Monastir（莫纳斯特尔理学院）；Laboratoire de la matière condensée et nanosciences LR11ES40（凝聚态物质与纳米科学实验室 LR11ES40）；Laboratoire Lorrain de Chimie Moléculaire（洛林分子化学实验室）；Université Lyon 1（里昂第一大学）；IRCELYON（催化、材料和表面研究所）；UMR 5256（联合研究单位 5256）
Rapid and Highly Efficient Synergistic Sonophotocatalytic Degradation of Methyl Orange with CuDoped LaFeO3 Perovskite Nanoparticles
Cadi Ayyad University（卡迪·阿亚德国立大学）；University of Picardy Jules Verne（皮卡第儒勒·凡尔纳大学）；University of Lorraine, CNRS（洛林大学，法国国家科学研究中心）；University of Bordeaux（波尔多大学）；University Mohammed VI Polytechnic（穆罕默德六世理工大学）；Jožef Stefan Institute（约瑟夫·斯蒂芬研究所）
Oxygen-Pressure-Limited Recovery of the Hematite α-Fe$_2$O$_3$(0001) Surface from a Reduced Fe$_3$O$_4$(111)-Like Layer
CEITEC - Central European Institute of Technology, Brno University of Technology（中欧技术研究所，布尔诺理工大学）；Institute of Physical Engineering, Brno University of Technology（物理工程系，布尔诺理工大学）
Subgrain-resolved Analysis of Degradation in Cu Metallization via Scanning 3DXRD and Thermomechanical Modeling
KU Leuven（荷语鲁汶大学）；Fraunhofer - Institut für Keramische Technologien und Systeme（弗劳恩霍夫陶瓷技术与系统研究所）；KAI – Kompetenzzentrum Automobil- und Industrieelektronik GmbH（KAI汽车与工业电子能力中心有限公司）；European Synchrotron Radiation Facility（欧洲同步辐射装置）
In this work, hybridization of nonmetal nitrogen-doped carbon dots (NCQDs) with ZnO nanorods (NRs) is utilized towards better photocatalytic degradation of rhodamine B under ultraviolet (UV) irradiation. The structural characterization is confirmed by XRD, XPS, FTIR and HRTEM measurements, while, optical properties have been investigated using UV-visible absorbance spectroscopy and photoluminescence study. The dye degradation using ZnO NR is recorded as ~69%, while the performance of ZnO/NCQD climbs up to ~90%, after nine minutes of UV irradiation. Furthermore, the reusability test suggests be…
Rapid electron transport in the quantum well triggers many novel physical phenomena and becomes a critical point for the high-speed electronics. Here, we found electrical properties of the titanium oxide changed from semiconducting to metallic as the degree of oxidation decreased and Schottky quantum well was formed at the interface. We take the asymmetry interface electron scattering effect into consideration when studying the electrical transport properties of the multilayer thin films. A novel physical conductivity model for the multilayer thin films was developed. We found electron would b…
Thickness-dependent degradation and optical access in epitaxial 2H-MoTe2 protected by metallic capping layers
University of Lodz（罗兹大学）；University of Warsaw（华沙大学）；Military University of Technology（军事理工大学）；Polish Academy of Sciences, Institute of Physics（波兰科学院物理研究所）；Ensemble3 Centre of Excellence（卓越中心 Ensemble3）
Operando X-ray absorption spectroscopy (XAS) can probe the electrode-electrolyte interface with single-digit nanometer depth resolution and offers a wealth of insight into the evolution and Coulombic efficiency or degradation of prototype cells, provided that the spectra can be reliably interpreted in terms of local oxidation state, atomic coordination, and electronic structure aboutthe excited atoms. To this end, we explore fluorine K-edge XAS of mono- (Li, Na, K) and di-valent (Mg, Ca, Zn) fluoride salts from a theoretical standpoint and discover a surprising level of detailed electronic str…
