WorldWideScience

Sample records for metal oxide interfaces

  1. High resolution electron microscopy of misfit dislocations at metal-oxide interfaces

    NARCIS (Netherlands)

    Groen, HB; Kooi, BJ; Vellinga, WP; De Hosson, JTM; Lejcek, P; Paidar,

    1999-01-01

    Misfit dislocations at metal-oxide interfaces are studied using HRTEM. By observing misfit dislocations the bonding across the metal-oxide interface can be studied. This is done for two cases, a parallel Cu-MgO {111} interface and tilted interfaces in Pd-ZnO and Ag-ZnO. From the Cu-MgO micrographs

  2. Ab Initio Thermodynamic Modeling of Electrified Metal-Oxide Interfaces

    DEFF Research Database (Denmark)

    Zeng, Zhenhua; Hansen, Martin Hangaard; Greeley, Jeff

    2015-01-01

    Solid oxide fuel cells are attractive devices in a sustainable energy context because of their fuel flexibility and potentially highly efficient conversion of chemical to electrical energy. The performance of the device is to a large extent determined by the atomic structure of the electrode...... the structural information can be used as a starting point for accurate calculations of the kinetics of fuel oxidation reactions, in particular the hydrogen oxidation reaction. More generally, we anticipate that the scheme will be a valuable theoretical tool to describe solid-solid interfaces. [Figure]...

  3. Hydrogen release at metal-oxide interfaces: A first principle study of hydrogenated Al/SiO{sub 2} interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Jianqiu, E-mail: jianqiu@vt.edu [Department of Mechanical Engineering, Virginia Tech, Goodwin Hall, 635 Prices Fork Road - MC 0238, Blacksburg, VA 24061 (United States); Tea, Eric; Li, Guanchen [Department of Mechanical Engineering, Virginia Tech, Goodwin Hall, 635 Prices Fork Road - MC 0238, Blacksburg, VA 24061 (United States); Hin, Celine [Department of Mechanical Engineering, Virginia Tech, Goodwin Hall, 635 Prices Fork Road - MC 0238, Blacksburg, VA 24061 (United States); Department of Material Science and Engineering, Virginia Tech, Goodwin Hall, 635 Prices Fork Road-MC 0238, Blacksburg, VA 24061 (United States)

    2017-06-01

    Highlights: • Hydrogen release process at the Al/SiO{sub 2} metal-oxide interface has been investigated. • A mathematical model that estimates the hydrogen release potential has been proposed. • Al atoms, Al−O bonds, and Si−Al bonds are the major hydrogen traps at the Al/SiO{sub 2} interface. • Hydrogen atoms are primarily release from Al−H and O−H bonds at the Al/SiO{sub 2} metal-oxide interface. - Abstract: The Anode Hydrogen Release (AHR) mechanism at interfaces is responsible for the generation of defects, that traps charge carriers and can induce dielectric breakdown in Metal-Oxide-Semiconductor Field Effect Transistors. The AHR has been extensively studied at Si/SiO{sub 2} interfaces but its characteristics at metal-silica interfaces remain unclear. In this study, we performed Density Functional Theory (DFT) calculations to study the hydrogen release mechanism at the typical Al/SiO{sub 2} metal-oxide interface. We found that interstitial hydrogen atoms can break interfacial Al−Si bonds, passivating a Si sp{sup 3} orbital. Interstitial hydrogen atoms can also break interfacial Al−O bonds, or be adsorbed at the interface on aluminum, forming stable Al−H−Al bridges. We showed that hydrogenated O−H, Si−H and Al−H bonds at the Al/SiO{sub 2} interfaces are polarized. The resulting bond dipole weakens the O−H and Si−H bonds, but strengthens the Al−H bond under the application of a positive bias at the metal gate. Our calculations indicate that Al−H bonds and O−H bonds are more important than Si−H bonds for the hydrogen release process.

  4. Angle-resolved photoemission spectroscopy studies of metallic surface and interface states of oxide insulators

    Science.gov (United States)

    Plumb, Nicholas C.; Radović, Milan

    2017-11-01

    Over the last decade, conducting states embedded in insulating transition metal oxides (TMOs) have served as gateways to discovering and probing surprising phenomena that can emerge in complex oxides, while also opening opportunities for engineering advanced devices. These states are commonly realized at thin film interfaces, such as the well-known case of LaAlO3 (LAO) grown on SrTiO3 (STO). In recent years, the use of angle-resolved photoemission spectroscopy (ARPES) to investigate the k-space electronic structure of such materials led to the discovery that metallic states can also be formed on the bare surfaces of certain TMOs. In this topical review, we report on recent studies of low-dimensional metallic states confined at insulating oxide surfaces and interfaces as seen from the perspective of ARPES, which provides a direct view of the occupied band structure. While offering a fairly broad survey of progress in the field, we draw particular attention to STO, whose surface is so far the best-studied, and whose electronic structure is probably of the most immediate interest, given the ubiquitous use of STO substrates as the basis for conducting oxide interfaces. The ARPES studies provide crucial insights into the electronic band structure, orbital character, dimensionality/confinement, spin structure, and collective excitations in STO surfaces and related oxide surface/interface systems. The obtained knowledge increases our understanding of these complex materials and gives new perspectives on how to manipulate their properties.

  5. Perpendicular magnetic anisotropy at transition metal/oxide interfaces and applications

    Science.gov (United States)

    Dieny, B.; Chshiev, M.

    2017-04-01

    Spin electronics is a rapidly expanding field stimulated by a strong synergy between breakthrough basic research discoveries and industrial applications in the fields of magnetic recording, magnetic field sensors, nonvolatile memories [magnetic random access memories (MRAM) and especially spin-transfer-torque MRAM (STT-MRAM)]. In addition to the discovery of several physical phenomena (giant magnetoresistance, tunnel magnetoresistance, spin-transfer torque, spin-orbit torque, spin Hall effect, spin Seebeck effect, etc.), outstanding progress has been made on the growth and nanopatterning of magnetic multilayered films and nanostructures in which these phenomena are observed. Magnetic anisotropy is usually observed in materials that have large spin-orbit interactions. However, in 2002 perpendicular magnetic anisotropy (PMA) was discovered to exist at magnetic metal/oxide interfaces [for instance Co (Fe )/alumina ]. Surprisingly, this PMA is observed in systems where spin-orbit interactions are quite weak, but its amplitude is remarkably large—comparable to that measured at Co /Pt interfaces, a reference for large interfacial anisotropy (anisotropy˜1.4 erg /cm2=1.4 mJ /m2 ). Actually, this PMA was found to be very common at magnetic metal/oxide interfaces since it has been observed with a large variety of amorphous or crystalline oxides, including AlOx, MgO, TaOx, HfOx, etc. This PMA is thought to be the result of electronic hybridization between the oxygen and the magnetic transition metal orbit across the interface, a hypothesis supported by ab initio calculations. Interest in this phenomenon was sparked in 2010 when it was demonstrated that the PMA at magnetic transition metal/oxide interfaces could be used to build out-of-plane magnetized magnetic tunnel junctions for STT-MRAM cells. In these systems, the PMA at the CoFeB /MgO interface can be used to simultaneously obtain good memory retention, thanks to the large PMA amplitude, and a low write current

  6. Determining the Chemical Composition of Corrosion Inhibitor/Metal Interfaces with XPS: Minimizing Post Immersion Oxidation.

    Science.gov (United States)

    Walczak, Monika S; Morales-Gil, Perla; Belashehr, Turia; Kousar, Kiran; Arellanes Lozada, Paulina; Lindsay, Robert

    2017-03-15

    An approach for acquiring more reliable X-ray photoelectron spectroscopy data from corrosion inhibitor/metal interfaces is described. More specifically, the focus is on metallic substrates immersed in acidic solutions containing organic corrosion inhibitors, as these systems can be particularly sensitive to oxidation following removal from solution. To minimize the likelihood of such degradation, samples are removed from solution within a glove box purged with inert gas, either N2 or Ar. The glove box is directly attached to the load-lock of the ultra-high vacuum X-ray photoelectron spectroscopy instrument, avoiding any exposure to the ambient laboratory atmosphere, and thus reducing the possibility of post immersion substrate oxidation. On this basis, one can be more certain that the X-ray photoelectron spectroscopy features observed are likely to be representative of the in situ submerged scenario, e.g. the oxidation state of the metal is not modified.

  7. Characterization of Interface State in Silicon Carbide Metal Oxide Semiconductor Capacitors

    Science.gov (United States)

    Kao, Wei-Chieh

    Silicon carbide (SiC) has always been considered as an excellent material for high temperature and high power devices. Since SiC is the only compound semiconductor whose native oxide is silicon dioxide (SiO2), it puts SiC in a unique position. Although SiC metal oxide semiconductor (MOS) technology has made significant progress in recent years, there are still a number of issues to be overcome before more commercial SiC devices can enter the market. The prevailing issues surrounding SiC MOSFET devices are the low channel mobility, the low quality of the oxide layer and the high interface state density at the SiC/SiO2 interface. Consequently, there is a need for research to be performed in order to have a better understanding of the factors causing the poor SiC/SiO2 interface properties. In this work, we investigated the generation lifetime in SiC materials by using the pulsed metal oxide semiconductor (MOS) capacitor method and measured the interface state density distribution at the SiC/SiO2 interface by using the conductance measurement and the high-low frequency capacitance technique. These measurement techniques have been performed on n-type and p-type SiC MOS capacitors. In the course of our investigation, we observed fast interface states at semiconductor-dielectric interfaces in SiC MOS capacitors that underwent three different interface passivation processes, such states were detected in the nitrided samples but not observed in PSG-passivated samples. This result indicate that the lack of fast states at PSG-passivated interface is one of the main reasons for higher channel mobility in PSG MOSFETs. In addition, the effect of mobile ions in the oxide on the response time of interface states has been investigated. In the last chapter we propose additional methods of investigation that can help elucidate the origin of the particular interface states, enabling a more complete understanding of the SiC/SiO2 material system.

  8. Metal oxide-graphene field-effect transistor: interface trap density extraction model

    Directory of Open Access Journals (Sweden)

    Faraz Najam

    2016-09-01

    Full Text Available A simple to implement model is presented to extract interface trap density of graphene field effect transistors. The presence of interface trap states detrimentally affects the device drain current–gate voltage relationship Ids–Vgs. At the moment, there is no analytical method available to extract the interface trap distribution of metal-oxide-graphene field effect transistor (MOGFET devices. The model presented here extracts the interface trap distribution of MOGFET devices making use of available experimental capacitance–gate voltage Ctot–Vgs data and a basic set of equations used to define the device physics of MOGFET devices. The model was used to extract the interface trap distribution of 2 experimental devices. Device parameters calculated using the extracted interface trap distribution from the model, including surface potential, interface trap charge and interface trap capacitance compared very well with their respective experimental counterparts. The model enables accurate calculation of the surface potential affected by trap charge. Other models ignore the effect of trap charge and only calculate the ideal surface potential. Such ideal surface potential when used in a surface potential based drain current model will result in an inaccurate prediction of the drain current. Accurate calculation of surface potential that can later be used in drain current model is highlighted as a major advantage of the model.

  9. A Universal Method to Engineer Metal Oxide-Metal-Carbon Interface for Highly Efficient Oxygen Reduction.

    Science.gov (United States)

    Lv, Lin; Zha, Dace; Ruan, Yunjun; Li, Zhishan; Ao, Xiang; Zheng, Jie; Jiang, Jianjun; Chen, Hao Ming; Chiang, Wei-Hung; Chen, Jun; Wang, Chundong

    2018-03-27

    Oxygen is the most abundant element in the Earth's crust. The oxygen reduction reaction (ORR) is also the most important reaction in life processes and energy converting/storage systems. Developing techniques toward high-efficiency ORR remains highly desired and a challenge. Here, we report a N-doped carbon (NC) encapsulated CeO 2 /Co interfacial hollow structure (CeO 2 -Co-NC) via a generalized strategy for largely increased oxygen species adsorption and improved ORR activities. First, the metallic Co nanoparticles not only provide high conductivity but also serve as electron donors to largely create oxygen vacancies in CeO 2 . Second, the outer carbon layer can effectively protect cobalt from oxidation and dissociation in alkaline media and as well imparts its higher ORR activity. In the meanwhile, the electronic interactions between CeO 2 and Co in the CeO 2 /Co interface are unveiled theoretically by density functional theory calculations to justify the increased oxygen absorption for ORR activity improvement. The reported CeO 2 -Co-NC hollow nanospheres not only exhibit decent ORR performance with a high onset potential (922 mV vs RHE), half-wave potential (797 mV vs RHE), and small Tafel slope (60 mV dec -1 ) comparable to those of the state-of-the-art Pt/C catalysts but also possess long-term stability with a negative shift of only 7 mV of the half-wave potential after 2000 cycles and strong tolerance against methanol. This work represents a solid step toward high-efficient oxygen reduction.

  10. Structural damage at the Si/SiO2 interface resulting from electron injection in metal-oxide-semiconductor devices

    Science.gov (United States)

    Mikawa, R. E.; Lenahan, P. M.

    1985-03-01

    With electron spin resonance, we have observed structural changes in metal-oxide-semiconductor structures resulting from the photoemisson of electrons from the silicon into the oxide. A trivalent silicon defect at the Si/SiO2 interface, termed Pb, is shown to be responsible for the interface states induced by electron injection. We find that these Pb centers are amphoteric interface state defects.

  11. Effects of the Molybdenum Oxide/Metal Anode Interfaces on Inverted Polymer Solar Cells

    International Nuclear Information System (INIS)

    Wu Jiang; Guo Xiao-Yang; Xie Zhi-Yuan

    2012-01-01

    Inverted polymer solar cells with molybdenum oxide (MoO 3 ) as an anode buffer layer and different metals (Al or Ag) as anodes are studied. It is found that the inverted cell with a top Ag anode demonstrates enhanced charge collection and higher power conversion efficiency (PCE) compared to the cell with a top Al anode. An 18% increment of PCE is obtained by replacing Al with Ag as the top anode. Further studies show that an interfacial dipole pointing from MoO 3 to Al is formed at MoO 3 /Al interfaces due to electron transfer from Al to MoO 3 while this phenomenon cannot be observed at MoO 3 /Ag interfaces. It is speculated that the electric field at the MoO 3 /Al interface would hinder hole extraction, and hence reduce the short-circuit current

  12. Improved interface properties of GaN-based metal-oxide-semiconductor devices with thin Ga-oxide interlayers

    Science.gov (United States)

    Yamada, Takahiro; Ito, Joyo; Asahara, Ryohei; Watanabe, Kenta; Nozaki, Mikito; Hosoi, Takuji; Shimura, Takayoshi; Watanabe, Heiji

    2017-06-01

    The impact of thin Ga-oxide (GaOx) interlayers on the electrical properties of GaN-based metal-oxide-semiconductor (MOS) devices was systematically investigated. Thin thermal oxides formed at around 900 °C were found to be beneficial for improving the electrical properties of insulator/GaN interfaces, despite the fact that thermal oxidation of GaN surfaces at high temperatures proceeds by means of grain growth. Consequently, well-behaved capacitance-voltage characteristics of SiO2/GaOx/n-GaN stacked MOS capacitors with an interface state density (Dit) as low as 1.7 × 1011 cm-2 eV-1 were demonstrated. Moreover, the Dit value was further reduced for the SiO2/GaOx/GaN capacitor with a 2-nm-thick sputter-deposited GaOx interlayer. These results clearly indicate the intrinsically superior nature of the oxide/GaN interfaces and provide plausible guiding principles for fabricating high-performance GaN-MOS devices with thin GaOx interlayers.

  13. Hard X-ray PhotoElectron Spectroscopy of transition metal oxides: Bulk compounds and device-ready metal-oxide interfaces

    International Nuclear Information System (INIS)

    Borgatti, F.; Torelli, P.; Panaccione, G.

    2016-01-01

    Highlights: • Hard X-ray PhotoElectron Spectroscopy (HAXPES) applied to buried interfaces of systems involving Transition Metal Oxides. • Enhanced contribution of the s states at high kinetic energies both for valence and core level spectra. • Sensitivity to chemical changes promoted by electric field across metal-oxide interfaces in resistive switching devices. - Abstract: Photoelectron spectroscopy is one of the most powerful tool to unravel the electronic structure of strongly correlated materials also thanks to the extremely large dynamic range in energy, coupled to high energy resolution that this form of spectroscopy covers. The kinetic energy range typically used for photoelectron experiments corresponds often to a strong surface sensitivity, and this turns out to be a disadvantage for the study of transition metal oxides, systems where structural and electronic reconstruction, different oxidation state, and electronic correlation may significantly vary at the surface. We report here selected Hard X-ray PhotoElectron Spectroscopy (HAXPES) results from transition metal oxides, and from buried interfaces, where we highlight some of the important features that such bulk sensitive technique brings in the analysis of electronic properties of the solids.

  14. Development of Efficient and Stable Inverted Bulk Heterojunction (BHJ) Solar Cells Using Different Metal Oxide Interfaces.

    Science.gov (United States)

    Litzov, Ivan; Brabec, Christoph J

    2013-12-10

    Solution-processed inverted bulk heterojunction (BHJ) solar cells have gained much more attention during the last decade, because of their significantly better environmental stability compared to the normal architecture BHJ solar cells. Transparent metal oxides (MeO x ) play an important role as the dominant class for solution-processed interface materials in this development, due to their excellent optical transparency, their relatively high electrical conductivity and their tunable work function. This article reviews the advantages and disadvantages of the most common synthesis methods used for the wet chemical preparation of the most relevant n -type- and p -type-like MeO x interface materials consisting of binary compounds A x B y . Their performance for applications as electron transport/extraction layers (ETL/EEL) and as hole transport/extraction layers (HTL/HEL) in inverted BHJ solar cells will be reviewed and discussed.

  15. Development of Efficient and Stable Inverted Bulk Heterojunction (BHJ Solar Cells Using Different Metal Oxide Interfaces

    Directory of Open Access Journals (Sweden)

    Ivan Litzov

    2013-12-01

    Full Text Available Solution-processed inverted bulk heterojunction (BHJ solar cells have gained much more attention during the last decade, because of their significantly better environmental stability compared to the normal architecture BHJ solar cells. Transparent metal oxides (MeOx play an important role as the dominant class for solution-processed interface materials in this development, due to their excellent optical transparency, their relatively high electrical conductivity and their tunable work function. This article reviews the advantages and disadvantages of the most common synthesis methods used for the wet chemical preparation of the most relevant n-type- and p-type-like MeOx interface materials consisting of binary compounds AxBy. Their performance for applications as electron transport/extraction layers (ETL/EEL and as hole transport/extraction layers (HTL/HEL in inverted BHJ solar cells will be reviewed and discussed.

  16. Microarray study of temperature-dependent sensitivity and selectivity of metal/oxide sensing interfaces

    Science.gov (United States)

    Tiffany, Jason; Cavicchi, Richard E.; Semancik, Stephen

    2001-02-01

    Conductometric gas microsensors offer the benefits of ppm-level sensitivity, real-time data, simple interfacing to electronics hardware, and low power consumption. The type of device we have been exploring consists of a sensor film deposited on a "microhotplate"- a 100 micron platform with built-in heating (to activate reactions on the sensing surface) and thermometry. We have been using combinatorial studies of 36-element arrays to characterize the relationship between sensor film composition, operating temperature, and response, as measured by the device's sensitivity and selectivity. Gases that have been tested on these arrays include methanol, ethanol, dichloromethane, propane, methane, acetone, benzene, hydrogen, and carbon monoxide, and are of interest in the management of environmental waste sites. These experiments compare tin oxide films modified by catalyst overlayers, and ultrathin metal seed layers. The seed layers are used as part of a chemical vapor deposition process that uses each array element's microheater to activate the deposition of SnO2, and control its microstructure. Low coverage (20 Ê) catalytic metals (Pd, Cu, Cr, In, Au) are deposited on the oxides by masked evaporation or sputtering. This presentation demonstrates the value of an array-based approach for developing film processing methods, measuring performance characteristics, and establishing reproducibility. It also illustrates how temperature-dependent response data for varied metal/oxide compositions can be used to tailor a microsensor array for a given application.

  17. Impact of process temperature on GaSb metal-oxide-semiconductor interface properties fabricated by ex-situ process

    Science.gov (United States)

    Yokoyama, Masafumi; Asakura, Yuji; Yokoyama, Haruki; Takenaka, Mitsuru; Takagi, Shinichi

    2014-06-01

    We have studied the impact of process temperature on interface properties of GaSb metal-oxide-semiconductor (MOS) structures fabricated by an ex-situ atomic-layer-deposition (ALD) process. We have found that the ALD temperature strongly affects the Al2O3/GaSb MOS interface properties. The Al2O3/GaSb MOS interfaces fabricated at the low ALD temperature of 150 °C have the minimum interface-trap density (Dit) of ˜4.5 × 1013 cm-2 eV-1. We have also found that the post-metalization annealing at temperature higher than 200 °C degrades the Al2O3/GaSb MOS interface properties. The low-temperature process is preferable in fabricating GaSb MOS interfaces in the ex-situ ALD process to avoid the high-temperature-induced degradations.

  18. Optical and electrical experiments at some transition-metal oxide foil-electrolyte interfaces

    International Nuclear Information System (INIS)

    Sari, S.O.; Ahlgren, W.L.

    1977-01-01

    Metal-oxide layers formed from transition-metal foils oxidized by heating in air have been examined for their photoelectrolytic response. The metals examined are Y, Ti, Zr, Hf, V, Nb, Ta, Mo, W, and Pt. Weak photoeffects are observed for oxide layers of all of these metals. Sizable light-dependent oxygen gas evolution rates are found in Ti and also in W oxides. The spectral dependence of the oxygen response in these compounds is investigated, and interpretation is given of these experiments

  19. Electron spin resonance study of interface states induced by electron injection in metal-oxide-semiconductor devices

    Science.gov (United States)

    Mikawa, R. E.; Lenahan, P. M.

    1986-03-01

    We find that electrons emitted from silicon into the oxide of metal-oxide-silicon devices generate amphoteric trivalent silicon (Pb center) defects at the Si/SiO2 interface. The Pb centers are generated in numbers approximately equal to that of the electron injection induced interface states. The effects of electron injection are similar to those of ionizing radiation to the extent that in both cases Pb centers are generated at the Si/SiO2 interface. However, the effects are not identical; ionizing radiation creates another trivalent silicon defect, termed E', in the oxide. We are unable to observe any E' generation in oxides subjected to electron injection. There appears to be a strong correlation between the number of trapped electrons and the electron injection induced Pb center interface states; this observation suggests that the trapping of electrons in the bulk of the oxides is in some way related to the creation of the Pb center interface state defects. We find that dry oxides subjected to a deuterium/nitrogen anneal exhibit less electron trapping than otherwise identical oxides which have been subjected to a hydrogen/nitrogen anneal. This observation is consistent with the idea that a hydrogen bond breaking event may be involved in electron capture.

  20. Quantization of Hall Resistance at the Metallic Interface between an Oxide Insulator and SrTiO3

    DEFF Research Database (Denmark)

    Trier, Felix; Prawiroatmodjo, Guenevere E. D. K.; Zhong, Zhicheng

    2016-01-01

    The two-dimensional metal forming at the interface between an oxide insulatorand SrTiO3 provides new opportunities for oxide electronics. However, the quantum Hall effect, one of the most fascinating effects of electrons confined in two dimensions, remains underexplored at these complex oxide...... heterointerfaces. Here, we report the experimental observation of quantized Hall resistance in a SrTiO3 heterointerface based on the modulation-doped amorphous-LaAlO3/SrTiO3 heterostructure, which exhibits both highelectron mobility exceeding 10, 000 cm2/V s and low carrier density on the order of ~1012 cm-2....... Along with unambiguous Shubnikov-de Haasoscillations, the spacing of the quantized Hall resistance suggests that the interface is comprised of a single quantum well with ten parallel conducting two-dimensional subbands. This provides new insight into the electronic structure of conducting oxide...

  1. Investigation of the Alkaline Electrochemical Interface and Development of Composite Metal/Metal-Oxides for Hydrogen and Oxygen Electrodes

    Science.gov (United States)

    Bates, Michael

    electrolyte. The HER kinetics of numerous binary & ternary Ni-alloys and composite Ni/metal-oxide/C samples were evaluated in aqueous 0.1 M KOH electrolyte. Furthermore a model of the double layer interface is proposed, which helps explain the observed ensemble effect in the presence of AEI. In Chapter 3, Ni-Fe and Ni-Fe-Co mixed-metal-oxide (MMO) films were investigated for oxygen evolution reaction (OER) activity in 0.1M KOH on high surface area Raney-Nickel supports. During investigations of MMO activity, aniline was identified as a useful "capping agent" for synthesis of high-surface area MMO-polyaniline (PANI) composite materials. A Ni-Fe-Co/PANI-Raney-Ni catalyst was developed which exhibits enhanced mass-activity compared to state-of-the-art Ni-Fe OER electrocatalysts reported to date. The morphology of the MMO catalyst film on PANI/Raney-Ni support provides excellent dispersion of active-sites and should maintain high active-site utilization for catalyst loading on gas-diffusion electrodes. In Chapter 4, the de-activation of reversible-hydrogen electrode catalysts was investigated and the development of a Pt-Ir-Nx/C catalyst is reported, which exhibits significantly increased stability in the HBr/Br 2 electrolyte. In contrast a Pt-Ir/C catalyst exhibited increased tolerance to high-voltage cycling and in particular showed recovery of electrocatalytic activity after reversible de-activation (presumably from bromide adsorption and subsequent oxidative bromide stripping). Under the harshest testing conditions of high-voltage cycling or exposure to Br2 the Pt-based catalyst showed a trend in stability: Pt < Pt-Ir < Pt-Ir-Nx. (Abstract shortened by UMI.).

  2. Hard X-ray photoemission spectroscopy of transition-metal oxide thin films and interfaces

    International Nuclear Information System (INIS)

    Wadati, H.; Fujimori, A.

    2013-01-01

    Highlights: •Photoemission spectroscopy is a powerful technique to study the electronic structures of transition-metal oxides. •Hard X-ray photoemission spectroscopy (HXPES) is a new type of photoemission spectroscopy which can probe bulk states. •HXPES is very suitable for studying oxide thin films such as the composition dependence and the film thickness dependence. -- Abstract: Photoemission spectroscopy is a powerful experimental technique to study the electronic structures of solids, especially of transition-metal oxides. Recently, hard X-ray photoemission spectroscopy (HXPES) has emerged as a more relevant experimental technique to obtain clear information about bulk states. Here, we describe how HXPES can be conveniently applied to study the interesting subjects on oxide thin films such as the composition dependence and the film thickness dependence of the electronic structures and the interfacial electronic structure of multilayers

  3. Environment-dependent photochromism of silver nanoparticles interfaced with metal-oxide films

    International Nuclear Information System (INIS)

    Fu, Shencheng; Sun, Shiyu; Zhang, Xintong; Zhang, Cen; Zhao, Xiaoning; Liu, Yichun

    2015-01-01

    Graphical abstract: - Highlights: • We prepared silver/mental-oxide nanocomposite films by physical sputtering technology to investigate the environment-dependent photo-dissolution of silver nanoparticles. • We built up an airtight and in situ monitorable system to measure photochromism of different films in various atmospheres. • Silver nanoparticles were found to be more easily photo-dissolved on the n-type metal oxide films compared with that on the p-type one, conductor and insulator. • Oxygen and humidity were verified to accelerate the photochromism of silver nanoparticles. - Abstract: Different metal-oxide films were fabricated by radio frequency magnetron sputtering. Further, a layer of silver nanoparticles (NPs) was deposited on the surface of the substrate by physical sputtering. Photochromism of the silver/metal-oxide nanocomposite films were investigated in situ under the irradiation of a linearly-polarized green laser beam (532 nm). Silver NPs were found to be easily photo-dissolved on the n-type metal-oxide films. By changing experimental conditions, it was also verified that both oxygen and humidity accelerate the photochromism of silver NPs. The corresponding micro-mechanism on charge separation and Ag + -ions mobility was also discussed. These results provided theoretical basis for the application of silver NPs in biological, chemical and medical areas.

  4. Impact of process temperature on GaSb metal-oxide-semiconductor interface properties fabricated by ex-situ process

    Energy Technology Data Exchange (ETDEWEB)

    Yokoyama, Masafumi, E-mail: yokoyama@mosfet.t.u-tokyo.ac.jp; Takenaka, Mitsuru; Takagi, Shinichi [Department of Electrical Engineering and Information Systems, The University of Tokyo, Yayoi 2-11-16, Bunkyo, Tokyo 113-0032 (Japan); JST-CREST, Yayoi 2-11-16, Bunkyo, Tokyo 113-0032 (Japan); Asakura, Yuji [Department of Electrical Engineering and Information Systems, The University of Tokyo, Yayoi 2-11-16, Bunkyo, Tokyo 113-0032 (Japan); Yokoyama, Haruki [NTT Photonics Laboratories, NTT Corporation, Atsugi 243-0198 (Japan)

    2014-06-30

    We have studied the impact of process temperature on interface properties of GaSb metal-oxide-semiconductor (MOS) structures fabricated by an ex-situ atomic-layer-deposition (ALD) process. We have found that the ALD temperature strongly affects the Al{sub 2}O{sub 3}/GaSb MOS interface properties. The Al{sub 2}O{sub 3}/GaSb MOS interfaces fabricated at the low ALD temperature of 150 °C have the minimum interface-trap density (D{sub it}) of ∼4.5 × 10{sup 13 }cm{sup −2} eV{sup −1}. We have also found that the post-metalization annealing at temperature higher than 200 °C degrades the Al{sub 2}O{sub 3}/GaSb MOS interface properties. The low-temperature process is preferable in fabricating GaSb MOS interfaces in the ex-situ ALD process to avoid the high-temperature-induced degradations.

  5. Hydride Microstructure at the Metal-Oxide Interface of Zircaloy-4 from H.B. Robinson Nuclear Reactor

    Energy Technology Data Exchange (ETDEWEB)

    Cinbiz, Mahmut N [ORNL; Edmondson, Philip D [ORNL; Terrani, Kurt A [ORNL

    2017-01-01

    This study investigates the hydride rim microstructure at the metal-oxide interface of Zircaloy-4 cladding segment removed from H.B. Robinson Nuclear Reactor by utilizing high resolution electron microscopy techniques with energy dispersive x-ray spectroscopy at Oak Ridge National Laboratory under the NSUF Rapid Turnout Experiment program. A complex stacking and orientation of hydride platelets has been observed below the sub-oxide layer. Furthermore, radial hydride platelets have been observed. EDS signals of both Fe and Cr has been reduced within hydrides whereas EDS signal of Sn is unaffected.

  6. Relating Random Telegraph Signal Noise in Metal Oxide Semiconductor Transistors to Interface Trap Energy Distribution

    NARCIS (Netherlands)

    van der Wel, A.P.; Klumperink, Eric A.M.; Hoekstra, E.; Nauta, Bram

    2005-01-01

    In this work, we study random telegraph signal (RTS) noise in metal-oxide-semiconductor field effect transistors when the device is periodically and rapidly cycled between an "on" and an "off" bias state. We derive the effective RTS time constants for this case using Shockley–Read–Hall statistics

  7. Modelling of multicomponent diffusion in a two-phase oxide-metal corium pool by a diffuse interface method

    International Nuclear Information System (INIS)

    Cardon, Clement

    2016-01-01

    This Ph.D. topic is focused on the modelling of stratification kinetics for an oxide-metal corium pool (U-O-Zr-steel system) in terms of multicomponent and multiphase diffusion. This work is part of a larger research effort for the development of a detailed corium pool modelling based on a CFD approach for thermal hydraulics. The overall goal is to improve the understanding of the involved phenomena and obtain closure laws for integral macroscopic models. The phase-field method coupled with an energy functional using the CALPHAD method appears to be relevant for this purpose. In a first part, we have developed a diffuse interface model in order to describe the diffusion process in the U-O system. This model has been coupled with a CALPHAD thermodynamic database and its parameterization has been developed with, in particular, an up-scaling procedure related to the interface thickness. Then, within the framework of a modelling for the U-O-Zr ternary system, we have proposed a generalization of the diffuse interface model through an assumption of local equilibrium for redox mechanisms. A particular attention was paid to the model analysis by 1D numerical simulations with a special focus on the steady state composition profiles. Finally we have applied this model to the U-O-Zr-Fe system. For that purpose, we have considered a configuration close to small-scale experimental tests of oxide-metal corium pool stratification. (author) [fr

  8. A Semi-Analytical Extraction Method for Interface and Bulk Density of States in Metal Oxide Thin-Film Transistors.

    Science.gov (United States)

    Chen, Weifeng; Wu, Weijing; Zhou, Lei; Xu, Miao; Wang, Lei; Ning, Honglong; Peng, Junbiao

    2018-03-11

    A semi-analytical extraction method of interface and bulk density of states (DOS) is proposed by using the low-frequency capacitance-voltage characteristics and current-voltage characteristics of indium zinc oxide thin-film transistors (IZO TFTs). In this work, an exponential potential distribution along the depth direction of the active layer is assumed and confirmed by numerical solution of Poisson's equation followed by device simulation. The interface DOS is obtained as a superposition of constant deep states and exponential tail states. Moreover, it is shown that the bulk DOS may be represented by the superposition of exponential deep states and exponential tail states. The extracted values of bulk DOS and interface DOS are further verified by comparing the measured transfer and output characteristics of IZO TFTs with the simulation results by a 2D device simulator ATLAS (Silvaco). As a result, the proposed extraction method may be useful for diagnosing and characterising metal oxide TFTs since it is fast to extract interface and bulk density of states (DOS) simultaneously.

  9. A Semi-Analytical Extraction Method for Interface and Bulk Density of States in Metal Oxide Thin-Film Transistors

    Directory of Open Access Journals (Sweden)

    Weifeng Chen

    2018-03-01

    Full Text Available A semi-analytical extraction method of interface and bulk density of states (DOS is proposed by using the low-frequency capacitance–voltage characteristics and current–voltage characteristics of indium zinc oxide thin-film transistors (IZO TFTs. In this work, an exponential potential distribution along the depth direction of the active layer is assumed and confirmed by numerical solution of Poisson’s equation followed by device simulation. The interface DOS is obtained as a superposition of constant deep states and exponential tail states. Moreover, it is shown that the bulk DOS may be represented by the superposition of exponential deep states and exponential tail states. The extracted values of bulk DOS and interface DOS are further verified by comparing the measured transfer and output characteristics of IZO TFTs with the simulation results by a 2D device simulator ATLAS (Silvaco. As a result, the proposed extraction method may be useful for diagnosing and characterising metal oxide TFTs since it is fast to extract interface and bulk density of states (DOS simultaneously.

  10. Nanoscale Chemical and Valence Evolution at the Metal/Oxide Interface: A Case Study of Ti/SrTiO 3

    KAUST Repository

    Li, Yangyang

    2016-06-27

    Metal/oxide interfaces are ubiquitous in a wide range of applications such as electronics, photovoltaics, memories, catalysis, and sensors. However, there have been few investigations dedicated to the nanoscale structural and chemical characteristics of these buried interfaces. In this work, the metal/oxide interface between Ti and SrTiO3 (STO) is examined as a prototypical system using high-resolution scanning transmission electron microscopy and electron energy loss spectroscopy. An atomic-thin Ti2O3-like layer at the Ti/STO interface prepared at room temperature is discovered, and first-principles calculations predict a metallic band structure of this 2D electron system. As a universal feature of such interfaces prepared at different temperatures, near the interface nanoscale oxygen-deficient domains and continuous modulation of Ti oxidation states are found. Overall, these results directly reveal complex chemical and valence evolutions at the metal/oxide interfaces, providing microscopic insights on such heterostructures. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

  11. Interplay between magnetic and dielectric phenomena at transition metal oxide interfaces

    International Nuclear Information System (INIS)

    Schumacher, Daniel

    2013-01-01

    The present work is concerned with the preparation, characterization and analysis of thin film heterostructures of perovskite oxide materials. Two different systems have been analyzed in detail: La 0.66 Sr 0.33 MnO 3 /SrTiO 3 (LSMO/STO) heterostructures have been investigated in order to understand the unusual occurrence of an exchange bias effect in multilayers of these two oxides. Monocrystalline LSMO single and LSMO/STO bilayers have been grown on STO by both High Oxygen Pressure Sputter Deposition (HSD) and Pulsed Laser Deposition. It was possible to reproduce the Exchange Bias effect in the samples grown by HSD by reducing the oxygen pressure during the layer growth. In fact, the size of the effect can be increased by further reduction of the oxygen pressure. The macroscopic sample analysis by X-ray Diffraction and Vibrating Sample Magnetometry suggests that the occurence of the Exchange Bias effect is linked to oxygen deficiencies in the LSMO layer. By combining X-ray Reflectometry, Polarized Neutron Reflectometry and X-ray Resonant magnetic Scattering (XRMS), the magnetic depth profile of the samples has been determined. By this, a region in LSMO at the interface to STO has been detected, where the magnetic moment is strongly suppressed. By putting together the results of the macroscopic sample analysis and the scattering experiments, an explanation for the occurence of the effect can be given: It is proposed, that a combination of strain and oxygen deficiencies shifts the LSMO at the interface in the antiferromagnetic phase of the LSMO strain vs. doping phase diagram. This interface region thus couples to the ferromagnetic part of the LSMO causing the Exchange Bias effect. The second heterostructure system under investigation in this work are bilayers of La 0.5 Sr 0.5 MnO 3 (LSMO) and BaTiO 3 (BTO). A possible dependence of the interface near magnetic structure of La 1-x Sr x MnO 3 having a doping level x close to the ferromagnetic-antiferromagnetic phase

  12. Interaction of Pd with α-Al2O3(0001): A case study of modeling the metal-oxide interface on complex substrates

    OpenAIRE

    Gomes, J. R. B.; Illas, Francesc; Cruz Hernández, Norge; Márquez Cruz, Antonio Marcial; Fernández Sanz, Javier

    2002-01-01

    The Pd/α-Al2O3(0001) interface at low Pd coverage has been studied by a variety of theoretical methods and models at this metal-oxide interface. All results are consistent and predict a noticeable interaction dominated by the metal polarization in response to the presence of the substrate. A significant contribution of the charge transfer from the transition metal to the surface is also observed. The periodic fully relaxed calculations show that the most favorable adsorption site for the inte...

  13. High concentration effects of neutral-potential-well interface traps on recombination dc current-voltage lineshape in metal-oxide-silicon transistors

    Science.gov (United States)

    Chen, Zuhui; Jie, Bin B.; Sah, Chih-Tang

    2008-11-01

    Steady-state Shockley-Read-Hall kinetics is employed to explore the high concentration effect of neutral-potential-well interface traps on the electron-hole recombination direct-current current-voltage (R-DCIV) properties in metal-oxide-silicon field-effect transistors. Extensive calculations include device parameter variations in neutral-trapping-potential-well electron interface-trap density NET (charge states 0 and -1), dopant impurity concentration PIM, oxide thickness Xox, forward source/drain junction bias VPN, and transistor temperature T. It shows significant distortion of the R-DCIV lineshape by the high concentrations of the interface traps. The result suggests that the lineshape distortion observed in past experiments, previously attributed to spatial variation in surface impurity concentration and energy distribution of interface traps in the silicon energy gap, can also arise from interface-trap concentration along surface channel region.

  14. Interface traps contribution on transport mechanisms under illumination in metal-oxide-semiconductor structures based on silicon nanocrystals

    Science.gov (United States)

    Chatbouri, S.; Troudi, M.; Kalboussi, A.; Souifi, A.

    2018-02-01

    The transport phenomena in metal-oxide-semiconductor (MOS) structures having silicon nanocrystals (Si-NCs) inside the dielectric layer have been investigated, in dark condition and under visible illumination. At first, using deep-level transient spectroscopy (DLTS), we find the presence of series electron traps having very close energy levels (comprised between 0.28 and 0.45 eV) for ours devices (with/without Si-NCs). And a single peak appears at low temperature only for MOS with Si-NCs related to Si-NCs DLTS response. In dark condition, the conduction mechanism is dominated by the thermionic fast emission/capture of charge carriers from the highly doped polysilicon layer to Si-substrate through interface trap states for MOS without Si-NCs. The tunneling of charge carriers from highly poly-Si to Si substrate trough the trapping/detrapping mechanism in the Si-NCs, at low temperature, contributed to the conduction mechanism for MOS with Si-NCs. The light effect on transport mechanisms has been investigated using current-voltage ( I- V), and high frequency capacitance-voltage ( C- V) methods. We have been marked the photoactive trap effect in inversion zone at room temperature in I- V characteristics, which confirm the contribution of photo-generated charge on the transport mechanisms from highly poly-Si to Si substrate trough the photo-trapping/detrapping mechanism in the Si-NCs and interfaces traps levels. These results have been confirmed by an increasing about 10 pF in capacity's values for the C- V characteristics of MOS with Si-NCs, in the inversion region for inverse high voltage applied under photoexcitation at low temperature. These results are helpful to understand the principle of charge transport in dark condition and under illumination, of MOS structures having Si-NCs in the SiO x = 1.5 oxide matrix.

  15. An Overview of Radiation-Induced Interface Traps in MOS (Metal-Oxide Semiconductor) Structures

    Science.gov (United States)

    1989-11-01

    continu- this hydrogen reached the interface it could ous-time-random-walk ( CTRW ) formalism break an Si-H bond producing H2 and a dan- developed by Montroll...al- Recently, Brown et al. applied CTRW analysis ready explained for the case of hole transport. to the H + transport, with very good results [711. 12

  16. Nanostructure-Directed Chemical Sensing: The IHSAB Principle and the Effect of Nitrogen and Sulfur Functionalization on Metal Oxide Decorated Interface Response

    Directory of Open Access Journals (Sweden)

    James L. Gole

    2013-08-01

    Full Text Available The response matrix, as metal oxide nanostructure decorated n-type semiconductor interfaces are modified in situ through direct amination and through treatment with organic sulfides and thiols, is demonstrated. Nanostructured TiO2, SnOx, NiO and CuxO (x = 1,2, in order of decreasing Lewis acidity, are deposited to a porous silicon interface to direct a dominant electron transduction process for reversible chemical sensing in the absence of significant chemical bond formation. The metal oxide sensing sites can be modified to decrease their Lewis acidity in a process appearing to substitute nitrogen or sulfur, providing a weak interaction to form the oxynitrides and oxysulfides. Treatment with triethylamine and diethyl sulfide decreases the Lewis acidity of the metal oxide sites. Treatment with acidic ethane thiol modifies the sensor response in an opposite sense, suggesting that there are thiol (SH groups present on the surface that provide a Brønsted acidity to the surface. The in situ modification of the metal oxides deposited to the interface changes the reversible interaction with the analytes, NH3 and NO. The observed change for either the more basic oxynitrides or oxysulfides or the apparent Brønsted acid sites produced from the interaction of the thiols do not represent a simple increase in surface basicity or acidity, but appear to involve a change in molecular electronic structure, which is well explained using the recently developed inverse hard and soft acids and bases (IHSAB model.

  17. Chemically abrupt interface between Ce oxide and Fe films

    International Nuclear Information System (INIS)

    Lee, H.G.; Lee, D.; Kim, S.; Kim, S.G.; Hwang, Chanyong

    2005-01-01

    A chemically abrupt Fe/Ce oxide interface can be formed by initial oxidation of an Fe film followed by deposition of Ce metal. Once a Ce oxide layer is formed on top of Fe, it acts a passivation barrier for oxygen diffusion. Further deposition of Ce metal followed by its oxidation preserve the abrupt interface between Ce oxide and Fe films. The Fe and Ce oxidation states have been monitored at each stage using X-ray photoelectron spectroscopy

  18. Study of Interface Charge Densities for ZrO2 and HfO2 Based Metal-Oxide-Semiconductor Devices

    Directory of Open Access Journals (Sweden)

    N. P. Maity

    2014-01-01

    Full Text Available A thickness-dependent interfacial distribution of oxide charges for thin metal oxide semiconductor (MOS structures using high-k materials ZrO2 and HfO2 has been methodically investigated. The interface charge densities are analyzed using capacitance-voltage (C-V method and also conductance (G-V method. It indicates that, by reducing the effective oxide thickness (EOT, the interface charge densities (Dit increases linearly. For the same EOT, Dit has been found for the materials to be of the order of 1012 cm−2 eV−1 and it is originated to be in good agreement with published fabrication results at p-type doping level of 1×1017 cm−3. Numerical calculations and solutions are performed by MATLAB and device simulation is done by ATLAS.

  19. Effects of buffered HF cleaning on metal-oxide-semiconductor interface properties of Al2O3/InAs/GaSb structures

    Science.gov (United States)

    Nishi, Koichi; Yokoyama, Masafumi; Yokoyama, Haruki; Hoshi, Takuya; Sugiyama, Hiroki; Takenaka, Mitsuru; Takagi, Shinichi

    2015-06-01

    We studied the impact of buffered HF (BHF) cleaning on the interface properties of Al2O3/InAs/GaSb metal-oxide-semiconductor (MOS) structures fabricated by the ex-situ surface cleaning process. The Al2O3/InAs/GaSb MOS structures fabricated with BHF cleaning exhibited lower Dit values than those fabricated with sulfur passivation. In addition, the Al2O3/InAs/GaSb MOS structures fabricated with BHF cleaning were robust with respect to the MOS field-effect transistor fabrication process by using W gate metal with PMA in the 250-300 °C range.

  20. Study of metallic interfaces

    International Nuclear Information System (INIS)

    Job, Bernard

    1973-01-01

    In the first part, the diffusion of the radiotracer 59 Fe along the artificially silver-iron interface has been investigated for 500 4 exp - 41200/RT. These values are compared with the values of surface and grain boundary diffusion of silver and iron. In the second part we have extended mass-transport methods (scratch smoothing and grain boundary grooving) to solid-solid interface. These methods lead to a value of Di* δ γi (Di* δ is the effective diffusion parameter and γi the interfacial energy). Knowing the value of γi = 4000 ergs /cm 2 from the equilibrium angle method we have deducted the value of Di*δ. (author) [fr

  1. The molecule-metal interface

    CERN Document Server

    Koch, Norbert; Wee, Andrew Thye Shen

    2013-01-01

    Reviewing recent progress in the fundamental understanding of the molecule-metal interface, this useful addition to the literature focuses on experimental studies and introduces the latest analytical techniques as applied to this interface.The first part covers basic theory and initial principle studies, while the second part introduces readers to photoemission, STM, and synchrotron techniques to examine the atomic structure of the interfaces. The third part presents photoelectron spectroscopy, high-resolution UV photoelectron spectroscopy and electron spin resonance to study the electroni

  2. Interface States and Trapping Effects in Al2O3- and ZrO2/InAlN/AlN/GaN Metal-Oxide-Semiconductor Heterostructures

    Science.gov (United States)

    Ťapajna, Milan; Kuzmík, Jan; Čičo, Karol; Pogany, Dionyz; Pozzovivo, Gianmauro; Strasser, Gottfried; Abermann, Stephan; Bertagnolli, Emmerich; Carlin, Jean-François; Grandjean, Nicolas; Fröhlich, Karol

    2009-09-01

    We investigate Al2O3- and ZrO2/InAlN/GaN metal-oxide-semiconductor heterostructures (MOS-H) using capacitance-time transients in the temperature range of 25-300 °C. A deep-level transient spectroscopy based analysis revealed the maximum interface state density distributions Dit(E) up to 3×1013 and 1×1013 eV-1 cm-2 for the Al2O3/InAlN and ZrO2/InAlN interface, respectively. The integral densities of interface states correlate well with the trapping-related gate-lag effect in corresponding InAlN/GaN MOS high electron mobility transistors (HEMTs). This explains the strongly reduced lag effect in ZrO2 MOS HEMTs. We assume hole trapping at oxide/InAlN interface to be a dominant effect responsible for the gate-lag effect in InAlN/GaN MOS HEMTs.

  3. Emergent Phenomena at Oxide Interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Hwang, H.Y.

    2012-02-16

    Transition metal oxides (TMOs) are an ideal arena for the study of electronic correlations because the s-electrons of the transition metal ions are removed and transferred to oxygen ions, and hence the strongly correlated d-electrons determine their physical properties such as electrical transport, magnetism, optical response, thermal conductivity, and superconductivity. These electron correlations prohibit the double occupancy of metal sites and induce a local entanglement of charge, spin, and orbital degrees of freedom. This gives rise to a variety of phenomena, e.g., Mott insulators, various charge/spin/orbital orderings, metal-insulator transitions, multiferroics, and superconductivity. In recent years, there has been a burst of activity to manipulate these phenomena, as well as create new ones, using oxide heterostructures. Most fundamental to understanding the physical properties of TMOs is the concept of symmetry of the order parameter. As Landau recognized, the essence of phase transitions is the change of the symmetry. For example, ferromagnetic ordering breaks the rotational symmetry in spin space, i.e., the ordered phase has lower symmetry than the Hamiltonian of the system. There are three most important symmetries to be considered here. (i) Spatial inversion (I), defined as r {yields} -r. In the case of an insulator, breaking this symmetry can lead to spontaneous electric polarization, i.e. ferroelectricity, or pyroelectricity once the point group belongs to polar group symmetry. (ii) Time-reversal symmetry (T) defined as t {yields} -t. In quantum mechanics, the time-evolution of the wave-function {Psi} is given by the phase factor e{sup -iEt/{h_bar}} with E being the energy, and hence time-reversal basically corresponds to taking the complex conjugate of the wave-function. Also the spin, which is induced by the 'spinning' of the particle, is reversed by time-reversal. Broken T-symmetry is most naturally associated with magnetism, since the

  4. Metal-Anion Pairing at Oxide/Water Interfaces: Theoretical and Experimental Investigations from the Nanoscale to the Macroscale

    Energy Technology Data Exchange (ETDEWEB)

    Allen, Heather [The Ohio State Univ., Columbus, OH (United States)

    2016-11-14

    We combine the use of several techniques including bulk adsorption experiments, X-ray absorption, infrared, total internal reflection Raman, and vibrational sum frequencygeneration (XAS, IR, TIR-Raman, VSFG) spectroscopies, and molecular modeling to investigate ion adsorption at mineral surfaces. XAS and TIR-Raman provides data on how the metal binds to the surface (e.g., monodentate, bidentate), IR provides data on bulk anion adsorption at mineral surfaces from aqueous solutions, and VSFG provides surface specific data on anion adsorption at the mineral surface as well as impact of adsorbed metal-anion pairs on water structure at the mineral surface. Molecular modeling is used to guide spectroscopic data interpretation by providing information on water structure around ions in solution and the structure of metal-anion complexes in aqueous solutions. In addition, molecular modeling is used to provide insight into water structure at mineral surfaces, the surface sites involved in ion adsorption, and the distribution of ion pairs between aqueous solution and the mineral surface. Our studies have focused on systems involving alkaline earth metal (Mg2+, Ca2+, Sr2+, Ba2+) and heavy metal (Co2+, Cd2+) cations. The anions we have selected for studyinclude Cl-, NO3-, ClO4-, SO42-, SeO32-, and SeO42-. Ion adsorption and the potential formation ofternary complexes on silica (quartz, amorphous silica), alumina (corundum and gibbsite), and ferric iron oxides (goethite and hematite) are under investigation.

  5. Mesoporous metal oxides and processes for preparation thereof

    Energy Technology Data Exchange (ETDEWEB)

    Suib, Steven L.; Poyraz, Altug Suleyman

    2018-03-06

    A process for preparing a mesoporous metal oxide, i.e., transition metal oxide. Lanthanide metal oxide, a post-transition metal oxide and metalloid oxide. The process comprises providing an acidic mixture comprising a metal precursor, an interface modifier, a hydrotropic ion precursor, and a surfactant; and heating the acidic mixture at a temperature and for a period of time sufficient to form the mesoporous metal oxide. A mesoporous metal oxide prepared by the above process. A method of controlling nano-sized wall crystallinity and mesoporosity in mesoporous metal oxides. The method comprises providing an acidic mixture comprising a metal precursor, an interface modifier, a hydrotropic ion precursor, and a surfactant; and heating the acidic mixture at a temperature and for a period of time sufficient to control nano-sized wall crystallinity and mesoporosity in the mesoporous metal oxides. Mesoporous metal oxides and a method of tuning structural properties of mesoporous metal oxides.

  6. Semiconductor growth on an oxide using a metallic surfactant and interface studies for potential gate stacks from first principles

    Energy Technology Data Exchange (ETDEWEB)

    Reyes Huamantinco, Andrei

    2008-05-09

    In this work the epitaxial growth of germanium on SrHfO{sub 3}(001), and the La{sub 2}Hf{sub 2}O{sub 7}/Si(001) and SrTiO{sub 3}/GaAs(001) interfaces were studied theoretically using the Projector-Augmented Wave (PAW) method. The PAW method is based on Density Functional Theory and it is implemented in the Car-Parrinello Ab-Initio Molecular Dynamics. The goal of the germanium growth on SrHfO{sub 3}(001) is to form a germanium film with low density of defects and smooth morphology, to be used as channel in a transistor. The feasibility of using a third material to achieve germanium layer-by-layer growth was investigated. The formation of an ordered strontium film on a SrO-terminated oxide substrate, to be used as template for germanium overgrowth, was studied. Deposition of germanium on the strontium 1ML template results in wetting and thus a change of the growth mode to layer-by-layer. The germanium surface is then passivated and a germanium compound is initially formed with strontium at the surface and interface. The interfacial structure and valence band offsets of the La{sub 2}Hf{sub 2}O{sub 7}/Si(001) crystalline system were studied. The SrTiO{sub 3}/GaAs(001) crystalline interfaces with unpinned Fermi level were investigated. (orig.)

  7. Identification of Fixed and Interface Trap Charges in Hot-Carrier Stressed Metal Oxide Semiconductor Field Effect Transistors (MOSFET's) through Ultraviolet Light Anneal and Gate Capacitance Measurements

    Science.gov (United States)

    Ling, C.

    1995-01-01

    Fixed and interface trap charges in hot-carrier degraded metal oxide semiconductor field effect transistors (MOSFET's) can be distinguished by ultraviolet light (λ=253.7 nm) annealing, and observing the resultant changes in the gate-to-drain capacitance. Trapped electrons anneal readily, resulting in large changes in the gate capacitance and the threshold voltage. This suggests a trap level below the conduction band edge of SiO2 that is smaller than the photon energy (4.9 eV). In contrast, trapped holes and interface traps do not anneal, or anneal insignificantly even after prolonged irradiation. This is consistent with a much deeper hole trap level in SiO2, generally reported.

  8. Metal oxide nanorod arrays on monolithic substrates

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Pu-Xian; Guo, Yanbing; Ren, Zheng

    2018-01-02

    A metal oxide nanorod array structure according to embodiments disclosed herein includes a monolithic substrate having a surface and multiple channels, an interface layer bonded to the surface of the substrate, and a metal oxide nanorod array coupled to the substrate surface via the interface layer. The metal oxide can include ceria, zinc oxide, tin oxide, alumina, zirconia, cobalt oxide, and gallium oxide. The substrate can include a glass substrate, a plastic substrate, a silicon substrate, a ceramic monolith, and a stainless steel monolith. The ceramic can include cordierite, alumina, tin oxide, and titania. The nanorod array structure can include a perovskite shell, such as a lanthanum-based transition metal oxide, or a metal oxide shell, such as ceria, zinc oxide, tin oxide, alumina, zirconia, cobalt oxide, and gallium oxide, or a coating of metal particles, such as platinum, gold, palladium, rhodium, and ruthenium, over each metal oxide nanorod. Structures can be bonded to the surface of a substrate and resist erosion if exposed to high velocity flow rates.

  9. Determination of bulk and interface density of states in metal oxide semiconductor thin-film transistors by using capacitance-voltage characteristics

    Science.gov (United States)

    Wei, Xixiong; Deng, Wanling; Fang, Jielin; Ma, Xiaoyu; Huang, Junkai

    2017-10-01

    A physical-based straightforward extraction technique for interface and bulk density of states in metal oxide semiconductor thin film transistors (TFTs) is proposed by using the capacitance-voltage (C-V) characteristics. The interface trap density distribution with energy has been extracted from the analysis of capacitance-voltage characteristics. Using the obtained interface state distribution, the bulk trap density has been determined. With this method, for the interface trap density, it is found that deep state density nearing the mid-gap is approximately constant and tail states density increases exponentially with energy; for the bulk trap density, it is a superposition of exponential deep states and exponential tail states. The validity of the extraction is verified by comparisons with the measured current-voltage (I-V) characteristics and the simulation results by the technology computer-aided design (TCAD) model. This extraction method uses non-numerical iteration which is simple, fast and accurate. Therefore, it is very useful for TFT device characterization.

  10. Interfaces and nanostructures of oxide octahedral frameworks

    Directory of Open Access Journals (Sweden)

    Felip eSandiumenge

    2014-08-01

    Full Text Available In the past decade, the rich physics exhibited by solid interfaces combining octahedral framework structures of transition metal oxides has fascinated the materials science community. However, the behavior of these materials still elude the current understanding of classical semiconductor and metal epitaxy. The reason for that is rooted in the surprising versatility of linked coordination units to adapt to a dissimilar substrate and the strong sensitivity of correlated oxides to external perturbations. The confluence of atomic control in oxide thin film epitaxy, state of the art high spatial resolution characterization techniques, and electronic structure computations, has allowed in recent years to obtain first insights on the underlying microscopic mechanisms governing the epitaxy of these fascinating materials. Here, we shortly review these mechanisms and highlight their potential in the design of novel nanostructures with enhanced functionalities.

  11. Monolithic metal oxide transistors.

    Science.gov (United States)

    Choi, Yongsuk; Park, Won-Yeong; Kang, Moon Sung; Yi, Gi-Ra; Lee, Jun-Young; Kim, Yong-Hoon; Cho, Jeong Ho

    2015-04-28

    We devised a simple transparent metal oxide thin film transistor architecture composed of only two component materials, an amorphous metal oxide and ion gel gate dielectric, which could be entirely assembled using room-temperature processes on a plastic substrate. The geometry cleverly takes advantage of the unique characteristics of the two components. An oxide layer is metallized upon exposure to plasma, leading to the formation of a monolithic source-channel-drain oxide layer, and the ion gel gate dielectric is used to gate the transistor channel effectively at low voltages through a coplanar gate. We confirmed that the method is generally applicable to a variety of sol-gel-processed amorphous metal oxides, including indium oxide, indium zinc oxide, and indium gallium zinc oxide. An inverter NOT logic device was assembled using the resulting devices as a proof of concept demonstration of the applicability of the devices to logic circuits. The favorable characteristics of these devices, including (i) the simplicity of the device structure with only two components, (ii) the benign fabrication processes at room temperature, (iii) the low-voltage operation under 2 V, and (iv) the excellent and stable electrical performances, together support the application of these devices to low-cost portable gadgets, i.e., cheap electronics.

  12. Electronic Structure at Oxide Interfaces

    Science.gov (United States)

    2014-06-01

    electronic properties of rnio 3 (r = pr, nd, eu, ho and y) perovskites studied by resonant soft x-ray magnetic powder diffraction. Journal of Physics...artificially nanostructured materials based on transition metal oxides, thereby enabling the design of materials with desired correlated electron properties ... properties . The means of achieving this goal is the implementation and development of the hybrid methodology of density functional theory and

  13. Temperature dependent current-voltage characteristics of Au/n-Si Schottky barrier diodes and the effect of transition metal oxides as an interface layer

    Science.gov (United States)

    Mahato, Somnath; Puigdollers, Joaquim

    2018-02-01

    Temperature dependent current-voltage (I‒V) characteristics of Au/n-type silicon (n-Si) Schottky barrier diodes have been investigated. Three transition metal oxides (TMO) are used as an interface layer between gold and silicon. The basic Schottky diode parameters such as ideality factor (n), barrier height (ϕb 0) and series resistance (Rs) are calculated and successfully explained by the thermionic emission (TE) theory. It has been found that ideality factor decreased and barrier height increased with increased of temperature. The conventional Richardson plot of ln(I0/T2) vs. 1000/T is determined the activation energy (Ea) and Richardson constant (A*). Whereas value of 'A*' is much smaller than the known theoretical value of n-type Si. The temperature dependent I-V characteristics obtained the mean value of barrier height (ϕb 0 bar) and standard deviation (σs) from the linear plot of ϕap vs. 1000/T. From the modified Richardson plot of ln(I0/T2) ˗ (qσ)2/2(kT)2 vs. 1000/T gives Richardson constant and homogeneous barrier height of Schottky diodes. Main observation in this present work is the barrier height and ideality factor shows a considerable change but the series resistance value exhibits negligible change due to TMO as an interface layer.

  14. Fabrication and Evaluation of One-Axis Oriented Lead Zirconate Titanate Films Using Metal-Oxide Nanosheet Interface Layer

    Science.gov (United States)

    Minemura, Yoshiki; Nagasaka, Kohei; Kiguchi, Takanori; Konno, Toyohiko J.; Funakubo, Hiroshi; Uchida, Hiroshi

    2013-09-01

    Nanosheet Ca2Nb3O20 (ns-CN) layers with pseudo-perovskite-type crystal configuration were applied on the surface of polycrystalline metal substrates to achieve preferential crystal orientation of Pb(Zr,Ti)O3 (PZT) films for the purpose of enhanced ferroelectricity comparable to that of epitaxial thin films. PZT films with tetragonal symmetry (Zr/Ti=0.40:0.60) were fabricated by chemical solution deposition (CSD) on ns-CN-buffered Inconel 625 and SUS 316L substrates, while ns-CN was applied on the the substrates by dip-coating. The preferential crystal growth on the ns-CN layer can be achieved by favorable lattice matching between (001)/(100)PZT and (001)ns-CN planes. The degree of (001) orientation was increased for PZT films on ns-CN/Inconel 625 and ns-CN/SUS 316L substrates, whereas randomly-oriented PZT films with a lower degree of (001) orientation were grown on bare and Inconel 625 films. Enhanced remanent polarization of 60 µC/cm2 was confirmed for the PZT films on ns-CN/metal substrates, ascribed to the preferential alignment of the polar [001] axis normal to the substrate surface, although it also suffered from higher coercive field above 500 kV/cm caused by PZT/metal interfacial reaction.

  15. Sulfur-H{sub z}(CH{sub x}){sub y}(z = 0,1) functionalized metal oxide nanostructure decorated interfaces: Evidence of Lewis base and Brönsted acid sites – Influence on chemical sensing

    Energy Technology Data Exchange (ETDEWEB)

    Laminack, William; Baker, Caitlin [Department of Physics, Georgia Institute of Technology, Atlanta, GA 30332 (United States); Gole, James, E-mail: james.gole@physics.gatech.edu [Department of Physics, Georgia Institute of Technology, Atlanta, GA 30332 (United States); Department of Mechanical Engineering, Georgia Tech, Atlanta, GA 30332 (United States)

    2015-06-15

    Nanostructure metal oxide decorated n-type extrinsic porous silicon (PS) semiconductor interfaces are modified through in-situ interaction with acidic ethane and butane thiols (EtSH, BuSH) and basic diethyl sulfide (Et{sub 2}S). Highly sensitive conductometric sensor evaluations and X-ray Photoelectron Spectroscopy demonstrate the effect of sulfur group functionalization modifying the acidity of the metal oxides and their interaction with NH{sub 3}. SEM micrographs demonstrate that the sulfur treated particles are less than 30 nm in size. EDAX studies confirm the chemical composition of the modified nanoparticles and suggest the surface interaction of the sulfides and thiols. The acidic thiols can form Brönsted acidic sites enhancing the acidity of the metal oxides, thus broadening the initial metal oxide acidity range. The sulfides interact to lower the Lewis acidity of nanostructured metal oxide sites. Conductometric response matrices with NH{sub 3} at room temperature, corresponding to the thiol and sulfide treated nanostructures of the metal oxides TiO{sub 2}, SnO{sub x}, Ni{sub x}O, Cu{sub x}O, and Au{sub x}O (x >> 1) are evaluated for a dominant electron transduction process forming the basis for reversible chemical sensing in the absence of chemical bond formation. Treatment with the acidic thiols enhances the metal center acidity. It is suggested that the thiols can interact to increase the Brönsted acidity of the doped metal oxide surface if they maintain SH bonds. This process may account for the shift in Lewis acidity as the Brönsted acid sites counter the decrease in Lewis acidity resulting from the interaction of S-(CH{sub x}){sub y} groups. In contrast, treatment with basic Et{sub 2}S decreases the Lewis acidity of the metal oxide sites, enhancing the basicity of the decorated interface. XPS measurements indicate a change in binding energy (BE) of the metal and oxygen centers. The observed changes in conductometric response do not represent a

  16. Novel transport phenomena at complex oxide interfaces

    NARCIS (Netherlands)

    Hilgenkamp, H.

    2013-01-01

    Novel electronic and magnetic phases are being observed at interfaces between insulating, non-magnetic oxide compounds, with the most notable example being the interface between SrTiO3 and LaAlO3. The basic properties of these interfaces will be discussed, as well as prospects for applications and

  17. Correlation of Chemisorption and Electronic Effects for Metal Oxide Interfaces: Transducing Principles for Temperature Programmed Gas Microsensors. Final Report

    International Nuclear Information System (INIS)

    Semancik, S.; Cavicchi, R. E.; DeVoe, D. L.; McAvoy, T. J.

    2001-01-01

    This Final Report describes efforts and results for a 3-year DoE/OST-EMSP project centered at NIST. The multidisciplinary project investigated scientific and technical concepts critical for developing tunable, MEMS-based, gas and vapor microsensors that could be applied for monitoring the types of multiple analytes (and differing backgrounds) encountered at DoE waste sites. Micromachined ''microhotplate'' arrays were used as platforms for fabricating conductometric sensor prototypes, and as microscale research tools. Efficient microarray techniques were developed for locally depositing and then performance evaluating thin oxide films, in order to correlate gas sensing characteristics with properties including composition, microstructure, thickness and surface modification. This approach produced temperature-dependent databases on the sensitivities of sensing materials to varied analytes (in air) which enable application-specific tuning of microsensor arrays. Mechanistic studies on adsorb ate transient phenomena were conducted to better understand the ways in which rapid temperature programming schedules can be used to produce unique response signatures and increase information density in microsensor signals. Chemometric and neural network analyses were also employed in our studies for recognition and quantification of target analytes

  18. Oxidation by metal salts

    International Nuclear Information System (INIS)

    Makhon'kov, D.I.; Cheprakov, A.V.; Rodkin, M.A.; Mil'chenko, A.Yu.; Beletskaya, I.P.

    1986-01-01

    Oxidation of toluene and para-substituted toluenes containing electron acceptor groups: p-toluic acid, p-methyltoluylate and p-nitrotoluene by ammonium cerium (4) nitrate and ammonium cerium (4) sulfate in aqueous solutions of trifluoroacetic acid in the presence of chlorides and bromides of alkali metals is studied. The rate and selectivity of oxidative halogenation in side chain and/or aromatic ring under the conditions studied depend both on the nature of substrate and halogenide-ion and on the reaction conditions and ligand surrounding of cerium (4) atom

  19. Interface state density of SiO2/p-type 4H-SiC ( 0001 ), ( 11 2 ¯ 0 ), ( 1 1 ¯ 00 ) metal-oxide-semiconductor structures characterized by low-temperature subthreshold slopes

    Science.gov (United States)

    Kobayashi, Takuma; Nakazawa, Seiya; Okuda, Takafumi; Suda, Jun; Kimoto, Tsunenobu

    2016-04-01

    Interface properties of heavily Al-doped 4H-SiC ( 0001 ) (Si-face), ( 11 2 ¯ 0 ) (a-face), and ( 1 1 ¯ 00 ) (m-face) metal-oxide-semiconductor (MOS) structures were characterized from the low-temperature gate characteristics of metal-oxide-semiconductor field-effect transistors (MOSFETs). From low-temperature subthreshold slopes, interface state density (Dit) at very shallow energy levels (ET) near the conduction band edge (Ec) was evaluated. We discovered that the Dit near Ec (Ec - 0.01 eV MOS structures with higher Al doping density for every crystal face (Si-, a-, and m-face). Linear correlation is observed between the channel mobility and Dit near Ec, and we concluded that the mobility drop observed in heavily doped MOSFETs is mainly caused by the increase of Dit near Ec.

  20. Ceramic-Metal Interfaces in Multilayer Actuators

    DEFF Research Database (Denmark)

    Engell, John; Pedersen, Henrik Guldberg; Andersen, Bjørn

    1996-01-01

    Multilayer actuators consist of a number of piezoelectric or electrostrictive ceramic layers, separated by thin metal electrodes. Thus, the ceramic-metal interface plays an even more important role than for bulk piezoceramics. The performance and durability of the actuator depends closely...

  1. Mesoporous Transition Metal Oxides for Supercapacitors

    Directory of Open Access Journals (Sweden)

    Yan Wang

    2015-10-01

    Full Text Available Recently, transition metal oxides, such as ruthenium oxide (RuO2, manganese dioxide (MnO2, nickel oxides (NiO and cobalt oxide (Co3O4, have been widely investigated as electrode materials for pseudo-capacitors. In particular, these metal oxides with mesoporous structures have become very hot nanomaterials in the field of supercapacitors owing to their large specific surface areas and suitable pore size distributions. The high specific capacities of these mesoporous metal oxides are resulted from the effective contacts between electrode materials and electrolytes as well as fast transportation of ions and electrons in the bulk of electrode and at the interface of electrode and electrolyte. During the past decade, many achievements on mesoporous transition metal oxides have been made. In this mini-review, we select several typical nanomaterials, such as RuO2, MnO2, NiO, Co3O4 and nickel cobaltite (NiCo2O4, and briefly summarize the recent research progress of these mesoporous transition metal oxides-based electrodes in the field of supercapacitors.

  2. Oxidation-Mediated Fingering in Liquid Metals

    Science.gov (United States)

    Eaker, Collin B.; Hight, David C.; O'Regan, John D.; Dickey, Michael D.; Daniels, Karen E.

    2017-10-01

    We identify and characterize a new class of fingering instabilities in liquid metals; these instabilities are unexpected due to the large interfacial tension of metals. Electrochemical oxidation lowers the effective interfacial tension of a gallium-based liquid metal alloy to values approaching zero, thereby inducing drastic shape changes, including the formation of fractals. The measured fractal dimension (D =1.3 ±0.05 ) places the instability in a different universality class than other fingering instabilities. By characterizing changes in morphology and dynamics as a function of droplet volume and applied electric potential, we identify the three main forces involved in this process: interfacial tension, gravity, and oxidative stress. Importantly, we find that electrochemical oxidation can generate compressive interfacial forces that oppose the tensile forces at a liquid interface. The surface oxide layer ultimately provides a physical and electrochemical barrier that halts the instabilities at larger positive potentials. Controlling the competition between interfacial tension and oxidative (compressive) stresses at the interface is important for the development of reconfigurable electronic, electromagnetic, and optical devices that take advantage of the metallic properties of liquid metals.

  3. Quantitative characterization of interface traps in Al2O3/AlGaN/GaN metal-oxide-semiconductor high-electron-mobility transistors by dynamic capacitance dispersion technique

    Science.gov (United States)

    Ma, Xiao-Hua; Zhu, Jie-Jie; Liao, Xue-Yang; Yue, Tong; Chen, Wei-Wei; Hao, Yue

    2013-07-01

    In this letter, the interface traps of Al2O3/AlGaN/GaN metal-oxide-semiconductor high-electron-mobility transistors (MOS-HEMTs) were characterized quantitatively by dynamic capacitance dispersion technique. An analysis of Al2O3/AlGaN interface states demonstrated deep traps in the range of 0.53 eV-1.16 eV below the conduction band, with trap density nearly constant and two orders of magnitude smaller than that at AlGaN surface due to the use of atomic layer deposition-grown Al2O3 insulator. As much as 2.23 × 1013 eV-1 cm-2 fast traps with time constant smaller than 0.3 μs were observed at AlGaN/GaN interface of MOS-HEMTs, which was consistent with the qualitative prediction from pulsed I-V test.

  4. Design and control of interface reaction between Al-based dielectrics and AlGaN layer in AlGaN/GaN metal-oxide-semiconductor structures

    Science.gov (United States)

    Watanabe, Kenta; Nozaki, Mikito; Yamada, Takahiro; Nakazawa, Satoshi; Anda, Yoshiharu; Ishida, Masahiro; Ueda, Tetsuzo; Yoshigoe, Akitaka; Hosoi, Takuji; Shimura, Takayoshi; Watanabe, Heiji

    2017-07-01

    Important clues for achieving well-behaved AlGaN/GaN metal-oxide-semiconductor (MOS) devices with Al-based gate dielectrics were systematically investigated on the basis of electrical and physical characterizations. We found that low-temperature deposition of alumina insulators on AlGaN surfaces is crucial to improve the interface quality, thermal stability, and variability of MOS devices by suppressing Ga diffusion into the gate oxides. Moreover, aluminum oxynitride grown in a reactive nitric atmosphere was proven to expand the optimal process window that would improve the interface quality and to enhance immunity against charge injection into the gate dielectrics. The results constitute common guidelines for achieving high-performance and reliable AlGaN/GaN MOS devices.

  5. First-principles study of fission product (Xe, Cs, Sr) incorporation and segregation in alkaline earth metal oxides, HfO(2), and the MgO-HfO(2) interface.

    Science.gov (United States)

    Liu, Xiang-Yang; Uberuaga, Blas P; Sickafus, Kurt E

    2009-01-28

    In order to close the nuclear fuel cycle, advanced concepts for separating out fission products are necessary. One approach is to use a dispersion fuel form in which a fissile core is surrounded by an inert matrix that captures and immobilizes the fission products from the core. If this inert matrix can be easily separated from the fuel, via e.g. solution chemistry, the fission products can be separated from the fissile material. We examine a surrogate dispersion fuel composition, in which hafnia (HfO(2)) is a surrogate for the fissile core and alkaline earth metal oxides are used as the inert matrix. The questions of fission product incorporation in these oxides and possible segregation behavior at interfaces are considered. Density functional theory based calculations for fission product elements (Xe, Sr, and Cs) in these oxides are carried out. We find smaller incorporation energy in hafnia than in MgO for Cs and Sr, and Xe if variation of charge state is allowed. We also find that this trend is reversed or reduced for alkaline earth metal oxides with large cation sizes. Model interfacial calculations show a strong tendency of segregation from bulk MgO to MgO-HfO(2) interfaces.

  6. In between matters, interfaces in complex oxides

    NARCIS (Netherlands)

    van Zalk, M.

    2009-01-01

    Complex oxides are emerging as a versatile class of materials, exhibiting a wide variety of properties. In recent years, it has become increasingly clear that the properties of complex-oxide interfaces can differ considerably from those of the bulk. This opens up the possibility of tuning and

  7. In Between Matters : Interfaces in Complex Oxides

    NARCIS (Netherlands)

    van Zalk, M.

    2009-01-01

    Complex oxides are emerging as a versatile class of materials, exhibiting a wide variety of properties. In recent years, it has become increasingly clear that the properties of complex-oxide interfaces can differ considerably from those of the bulk. This opens up the possibility of tuning and

  8. Confined Catalysis in the g-C3N4/Pt(111) Interface: Feasible Molecule Intercalation, Tunable Molecule-Metal Interaction, and Enhanced Reaction Activity of CO Oxidation.

    Science.gov (United States)

    Wang, Shujiao; Feng, Yingxin; Yu, Ming'an; Wan, Qiang; Lin, Sen

    2017-09-27

    The deposition of a two-dimensional (2D) atomic nanosheet on a metal surface has been considered as a new route for tuning the molecule-metal interaction and surface reactivity in terms of the confinement effect. In this work, we use first-principles calculations to systematically explore a novel nanospace constructed by placing a 2D graphitic carbon nitride (g-C 3 N 4 ) nanosheet over a Pt(111) surface. The confined catalytic activity in this nanospace is investigated using CO oxidation as a model reaction. With the inherent triangular pores in the g-C 3 N 4 overlayer being taken advantage of, molecules such as CO and O 2 can diffuse to adsorb on the Pt(111) surface underneath the g-C 3 N 4 overlayer. Moreover, the mechanism of intercalation is also elucidated, and the results reveal that the energy barrier depends mainly on the properties of the molecule and the channel. Importantly, the molecule-catalyst interaction can be tuned by the g-C 3 N 4 overlayer, considerably reducing the adsorption energy of CO on Pt(111) and leading to enhanced reactivity in CO oxidation. This work will provide important insight for constructing a promising nanoreactor in which the following is observed: The molecule intercalation is facile; the molecule-metal interaction is efficiently tuned; the metal-catalyzed reaction is promoted.

  9. Spin-Orbitronics at Transition Metal Interfaces

    KAUST Repository

    Manchon, Aurelien

    2017-11-09

    The presence of large spin–orbit interaction at transition metal interfaces enables the emergence of a variety of fascinating phenomena that have been at the forefront of spintronics research in the past 10 years. The objective of the present chapter is to offer a review of these various effects from a theoretical perspective, with a particular focus on spin transport, chiral magnetism, and their interplay. After a brief description of the orbital hybridization scheme at transition metal interfaces, we address the impact of spin–orbit coupling on the interfacial magnetic configuration, through the celebrated Dzyaloshinskii–Moriya interaction. We then discuss the physics of spin transport and subsequent torques occurring at these interfaces. We particularly address the spin Hall, spin swapping, and inverse spin-galvanic effects. Finally, the interplay between flowing charges and chiral magnetic textures and their induced dynamics are presented. We conclude this chapter by proposing some perspectives on promising research directions.

  10. Surface Embedded Metal Oxide Sensors (SEMOS)

    DEFF Research Database (Denmark)

    Jespersen, Jesper Lebæk; Talat Ali, Syed; Pleth Nielsen, Lars

    is the second and main part of the project. The main challenges in developing metal oxide sensors are proper choice of the material, sensor location and fabrication technique due to lifetime and cross sensitivity issues in harsh environment where the problems like de-bonding or some kind of diffusion......SEMOS is a joint project between Aalborg University, Danish Technological Institute and Danish Technical University in which micro temperature sensors and metal oxide-based gas sensors are developed and tested in a simulated fuel cell environment as well as in actual working fuel cells. Initially...... complex and sensors are not easily implemented in the construction. Hence sensor interface and sensor position must therefore be chosen carefully in order to make the sensors as non-intrusive as possible. Metal Oxide Sensors (MOX) for measuring H2, O2 and CO concentration in a fuel cell environment...

  11. Conducting metal oxide and metal nitride nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    DiSalvo, Jr., Francis J.; Subban, Chinmayee V.

    2017-12-26

    Conducting metal oxide and nitride nanoparticles that can be used in fuel cell applications. The metal oxide nanoparticles are comprised of for example, titanium, niobium, tantalum, tungsten and combinations thereof. The metal nitride nanoparticles are comprised of, for example, titanium, niobium, tantalum, tungsten, zirconium, and combinations thereof. The nanoparticles can be sintered to provide conducting porous agglomerates of the nanoparticles which can be used as a catalyst support in fuel cell applications. Further, platinum nanoparticles, for example, can be deposited on the agglomerates to provide a material that can be used as both an anode and a cathode catalyst support in a fuel cell.

  12. Extraction of carrier mobility and interface trap density in InGaAs metal oxide semiconductor structures using gated Hall method

    Science.gov (United States)

    Chidambaram, Thenappan

    III-V semiconductors are potential candidates to replace Si as a channel material in next generation CMOS integrated circuits owing to their superior carrier mobilities. Low density of states (DOS) and typically high interface and border trap densities (Dit) in high mobility group III-V semiconductors provide difficulties in quantification of Dit near the conduction band edge. The trap response above the threshold voltage of a MOSFET can be very fast, and conventional Dit extraction methods, based on capacitance/conductance response (CV methods) of MOS capacitors at frequencies properties of III-V interfaces is an ambiguity of determination of electron density in the MOSFET channel. Traditional evaluation of carrier density by integration of the C-V curve, gives incorrect values for D it and mobility. Here we employ gated Hall method to quantify the D it spectrum at the high-K oxide/III-V semiconductor interface for buried and surface channel devices using Hall measurement and capacitance-voltage data. Determination of electron density directly from Hall measurements allows for obtaining true mobility values.

  13. Interface/border trap characterization of Al{sub 2}O{sub 3}/AlN/GaN metal-oxide-semiconductor structures with an AlN interfacial layer

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Shenghou; Yang, Shu; Tang, Zhikai; Jiang, Qimeng; Liu, Cheng; Chen, Kevin J., E-mail: eekjchen@ust.hk [Department of Electronic and Computer Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon (Hong Kong); Wang, Maojun [Institute of Microelectronics, Peking University, Beijing 100871 (China); Shen, Bo [School of Physics, Peking University, Beijing 100871 (China)

    2015-02-02

    We report the interface characterization of Al{sub 2}O{sub 3}/AlN/GaN MOS (metal-oxide-semiconductor) structures with an AlN interfacial layer. A thin monocrystal-like interfacial layer (AlN) is formed at the Al{sub 2}O{sub 3}/GaN to effectively block oxygen from the GaN surface and prevent the formation of detrimental Ga-O bonds. The suppression of Ga-O bonds is validated by X-ray photoelectron spectroscopy of the critical interface. Frequency-dispersion in C-V characteristics has been significantly reduced, owing to improved interface quality. Furthermore, using the conventional conductance method suitable for extracting the interface trap density D{sub it} in MOS structures, D{sub it} in the device with AlN was determined to be in the range of 10{sup 11}–10{sup 12 }eV{sup −1 }cm{sup −2}, showing one order of magnitude lower than that without AlN. Border traps near the gate-dielectric/GaN interface were identified and shown to be suppressed by the AlN interfacial layer as well.

  14. Nanotoxicology of Metal Oxide Nanoparticles

    Directory of Open Access Journals (Sweden)

    Amedea B. Seabra

    2015-06-01

    Full Text Available This review discusses recent advances in the synthesis, characterization and toxicity of metal oxide nanoparticles obtained mainly through biogenic (green processes. The in vitro and in vivo toxicities of these oxides are discussed including a consideration of the factors important for safe use of these nanomaterials. The toxicities of different metal oxide nanoparticles are compared. The importance of biogenic synthesized metal oxide nanoparticles has been increasing in recent years; however, more studies aimed at better characterizing the potent toxicity of these nanoparticles are still necessary for nanosafely considerations and environmental perspectives. In this context, this review aims to inspire new research in the design of green approaches to obtain metal oxide nanoparticles for biomedical and technological applications and to highlight the critical need to fully investigate the nanotoxicity of these particles.

  15. Direct bonding of metals to ceramics: Interface investigations

    Science.gov (United States)

    Curicuta, Victor

    There is a growing interest in metal/ceramic bonding for a wide range of applications from electronic packaging to biomedical implants. In this research work, results are reported for direct bonding of copper to ceramic (e.g., Al2O3 and ZrO) in a furnace under inert atmosphere (e.g., N2 and Ar2). Other, metals such as Cu, Ni, SS-316 were directly bonded to ceramics (e.g., α- Al2O3, sapphire) using laser heating (e.g., 247 nm and 10.6 μm wavelengths) in the presence of N2 atmosphere. Cu flakes have bean bonded to industrial alumina ceramic and sapphire in the presence of methyl, ethyl and isopropyl alcohols using a CO2 laser. All these experiments were performed by heating the metal or metal-organic media member for a sufficient time in order to create a metal-metal oxide eutectic melt at the interface with the ceramic substrate. Thermal wave imaging (TWI) was used to investigate the bonding at the metal/ceramic interface. It was found that the method of direct bonding of metals to ceramics using lasers performed better than the furnace. The properties of the copper bonded layer on alumina ceramic was investigated using scanning electron microscopy (SEM). Also, the elemental distribution at the metal/ceramic interface was analyzed, using energy dispersive x-ray spectroscopy (EDS). With the help of x-ray diffraction (XRD), the phase present at the copper/industrial alumina ceramic interface was determined to be CuAl2O4. This was different from the CuAlO2 phase found at the copper/sapphire interface for the furnace bonding case. Transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM) was also used to investigate the aspects of metal/ceramic interfaces. It was found that the samples processed by furnace heating and by laser beam heating have a diffused transition interface. The electron diffraction patterns revealed the phase present at the interface (Cu/ /alpha- Al2O3) to be a cubic one, with the CuAl2O4 crystallographic

  16. Thin film hydrous metal oxide catalysts

    Science.gov (United States)

    Dosch, Robert G.; Stephens, Howard P.

    1995-01-01

    Thin film (metal oxide catalysts are prepared by 1) synthesis of a hydrous metal oxide, 2) deposition of the hydrous metal oxide upon an inert support surface, 3) ion exchange with catalytically active metals, and 4) activating the hydrous metal oxide catalysts.

  17. A red metallic oxide photocatalyst

    Science.gov (United States)

    Xu, Xiaoxiang; Randorn, Chamnan; Efstathiou, Paraskevi; Irvine, John T. S.

    2012-07-01

    Light absorption across the bandgap in semiconductors is exploited in many important applications such as photovoltaics, light emitting diodes and photocatalytic conversion. Metals differ from semiconductors in that there is no energy gap separating occupied and unoccupied levels; however, it is still possible to excite electrons between bands. This is evidenced by materials with metallic properties that are also strongly coloured. An important question is whether such coloured metals could be used in light harvesting or similar applications. The high conductivity of a metal would preclude sufficient electric field being available to separate photocarriers; however, the high carrier mobility in a metal might also facilitate kinetic charge separation. Here we clearly demonstrate for the first time the use of a red metallic oxide, Sr1-xNbO3 as an effective photocatalyst. The material has been used under visible light to photocatalyse the oxidation of methylene blue and both the oxidation and reduction of water assisted by appropriate sacrificial elements.

  18. Dynamic Stabilization of Metal Oxide–Water Interfaces

    Energy Technology Data Exchange (ETDEWEB)

    McBriarty, Martin E.; von Rudorff, Guido Falk; Stubbs, Joanne; Eng, Peter; Blumberger, Jochen; Rosso, Kevin M.

    2017-02-08

    Metal oxide growth, dissolution, and redox reactivity depend on the structure and dynamics at the interface with aqueous solution. We present the most definitive analysis to date of the hydrated naturally abundant r-cut (11$\\bar{0}$2) termination of the iron oxide hematite (α-Fe2O3). In situ synchrotron X-ray scattering analysis reveals a ridged lateral arrangement of adsorbed water molecules hydrogen bonded to terminal aquo groups. Large-scale hybrid-functional density functional theory-based molecular dynamics (DFT-MD) simulations show how this structure is dynamically stabilized by picosecond exchange between aquo groups and adsorbed water, even under nominally dry conditions. Surface pKa prediction based on bond valence analysis suggests that water exchange may influence the proton transfer reactions associated with acid/base reactivity at the interface. Our findings rectify inconsistencies between existing models and may be extended to resolving more complex electrochemical phenomena at metal oxide-water interfaces.

  19. Dynamic Stabilization of Metal Oxide–Water Interfaces

    Energy Technology Data Exchange (ETDEWEB)

    McBriarty, Martin E.; von Rudorff, Guido Falk; Stubbs, Joanne E.; Eng, Peter J.; Blumberger, Jochen; Rosso, Kevin M.

    2017-02-08

    The interaction of water with metal oxide surfaces plays a crucial role in the catalytic and geochemical behavior of metal oxides. In a vast majority of studies, the interfacial structure is assumed to arise from a relatively static lowest energy configuration of atoms, even at room temperature. Using hematite (α-Fe2O3) as a model oxide, we show through a direct comparison of in situ synchrotron X-ray scattering with density functional theory-based molecular dynamics simulations that the structure of the (1102) termination is dynamically stabilized by picosecond water exchange. Simulations show frequent exchanges between terminal aquo groups and adsorbed water in locations and with partial residence times consistent with experimentally determined atomic sites and fractional occupancies. Frequent water exchange occurs even for an ultrathin adsorbed water film persisting on the surface under a dry atmosphere. The resulting time-averaged interfacial structure consists of a ridged lateral arrangement of adsorbed water molecules hydrogen bonded to terminal aquo groups. Surface pKa prediction based on bond valence analysis suggests that water exchange will influence the proton-transfer reactions underlying the acid/base reactivity at the interface. Our findings provide important new insights for understanding complex interfacial chemical processes at metal oxide–water interfaces.

  20. Structural characterization of water-metal interfaces

    Science.gov (United States)

    Ryczko, Kevin; Tamblyn, Isaac

    2017-08-01

    We analyze and compare the structural, dynamical, and electronic properties of liquid water next to prototypical metals including Pt, graphite, and graphene. Our results are built on Born-Oppenheimer molecular dynamics (BOMD) generated using density functional theory (DFT) which explicitly include van der Waals (vdW) interactions within a first principles approach. All calculations reported use large simulation cells, allowing for an accurate treatment of the water-electrode interfaces. We have included vdW interactions through the use of the optB86b-vdW exchange correlation functional. Comparisons with the Perdew-Burke-Ernzerhof (PBE) exchange correlation functional are also shown. We find an initial peak, due to chemisorption, in the density profile of the liquid water-Pt interface not seen in the liquid water-graphite interface, liquid water-graphene interface, nor interfaces studied previously. To further investigate this chemisorption peak, we also report differences in the electronic structure of single water molecules on both Pt and graphite surfaces. We find that a covalent bond forms between the single water molecule and the Pt surface but not between the single water molecule and the graphite surface. We also discuss the effects that defects and dopants in the graphite and graphene surfaces have on the structure and dynamics of liquid water.

  1. Ceria-based model catalysts: fundamental studies on the importance of the metal-ceria interface in CO oxidation, the water-gas shift, CO2hydrogenation, and methane and alcohol reforming.

    Science.gov (United States)

    Rodriguez, José A; Grinter, David C; Liu, Zongyuan; Palomino, Robert M; Senanayake, Sanjaya D

    2017-04-03

    Model metal/ceria and ceria/metal catalysts have been shown to be excellent systems for studying fundamental phenomena linked to the operation of technical catalysts. In the last fifteen years, many combinations of well-defined systems involving different kinds of metals and ceria have been prepared and characterized using the modern techniques of surface science. So far most of the catalytic studies have been centered on a few reactions: CO oxidation, the hydrogenation of CO 2 , and the production of hydrogen through the water-gas shift reaction and the reforming of methane or alcohols. Using model catalysts it has been possible to examine in detail correlations between the structural, electronic and catalytic properties of ceria-metal interfaces. In situ techniques (X-ray photoelectron spectroscopy, X-ray absorption spectroscopy, infrared spectroscopy, scanning tunneling microscopy) have been combined to study the morphological changes under reaction conditions and investigate the evolution of active phases involved in the cleavage of C-O, C-H and C-C bonds. Several studies with model ceria catalysts have shown the importance of strong metal-support interactions. In general, a substantial body of knowledge has been acquired and concepts have been developed for a more rational approach to the design of novel technical catalysts containing ceria.

  2. Defect Engineering and Interface Phenomena in Tin Oxide

    KAUST Repository

    Albar, Arwa

    2017-04-05

    The advance in transparent electronics requires high-performance transparent conducting oxide materials. The microscopic properties of these materials are sensitive to the presence of defects and interfaces and thus fundamental understanding is required for materials engineering. In this thesis, first principles density functional theory is used to investigate the possibility of tuning the structural, electronic and magnetic properties of tin oxide by means of defects and interfaces. Our aim is to reveal unique properties and the parameters to control them as well as to explain the origin of unique phenomena in oxide materials. The stability of native defect in tin monoxide (SnO) under strain is investigated using formation energy calculations. We find that the conductivity (which is controlled by native defects) can be switched from p-type to either n-type or undoped semiconducting by means of applied pressure. We then target inducing magnetism in SnO by 3d transition metal doping. We propose that V doping is efficient to realize spin polarization at high temperature. We discuss different tin oxide interfaces. Metallic states are found to form at the SnO/SnO2 interface with electronic properties that depend on the interface terminations. The origin of these states is explained in terms of charge transfer caused by chemical bonding and band alignment. For the SnO/SnO2 heterostructure, we observe the formation of a two dimensional hole gas at the interface, which is surprising as it cannot be explained by the standard polar catastrophe model. Thus, we propose a charge density discontinuity model to explain our results. The model can be generalized to other polar-polar interfaces. Motivated by technological applications, the electronic and structural properties of the MgO (100)/SnO2 (110) interface are investigated. Depending on the interface termination, we observe the formation of a two dimensional electron gas or spin polarized hole gas. Aiming to identify further

  3. METAL OXIDE NANOPARTICLES

    Energy Technology Data Exchange (ETDEWEB)

    FERNANDEZ-GARCIA,M.; RODGRIGUEZ, J.A.

    2007-10-01

    This chapter covers the fundamental science, synthesis, characterization, physicochemical properties and applications of oxide nanomaterials. Explains fundamental aspects that determine the growth and behavior of these systems, briefly examines synthetic procedures using bottom-up and top-down fabrication technologies, discusses the sophisticated experimental techniques and state of the art theory results used to characterize the physico-chemical properties of oxide solids and describe the current knowledge concerning key oxide materials with important technological applications.

  4. Synthesis of vertically aligned metal oxide nanostructures

    KAUST Repository

    Roqan, Iman S.

    2016-03-03

    Metal oxide nanostructure and methods of making metal oxide nanostructures are provided. The metal oxide nanostructures can be 1 -dimensional nanostructures such as nanowires, nanofibers, or nanotubes. The metal oxide nanostructures can be doped or undoped metal oxides. The metal oxide nanostructures can be deposited onto a variety of substrates. The deposition can be performed without high pressures and without the need for seed catalysts on the substrate. The deposition can be performed by laser ablation of a target including a metal oxide and, optionally, a dopant. In some embodiments zinc oxide nanostructures are deposited onto a substrate by pulsed laser deposition of a zinc oxide target using an excimer laser emitting UV radiation. The zinc oxide nanostructure can be doped with a rare earth metal such as gadolinium. The metal oxide nanostructures can be used in many devices including light-emitting diodes and solar cells.

  5. Mesoporous metal oxide graphene nanocomposite materials

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Jun; Aksay, Ilhan A.; Kou, Rong; Wang, Donghai

    2016-05-24

    A nanocomposite material formed of graphene and a mesoporous metal oxide having a demonstrated specific capacity of more than 200 F/g with particular utility when employed in supercapacitor applications. A method for making these nanocomposite materials by first forming a mixture of graphene, a surfactant, and a metal oxide precursor, precipitating the metal oxide precursor with the surfactant from the mixture to form a mesoporous metal oxide. The mesoporous metal oxide is then deposited onto a surface of the graphene.

  6. On the origin of interface states at oxide/III-nitride heterojunction interfaces

    Science.gov (United States)

    Matys, M.; Adamowicz, B.; Domanowska, A.; Michalewicz, A.; Stoklas, R.; Akazawa, M.; Yatabe, Z.; Hashizume, T.

    2016-12-01

    The energy spectrum of interface state density, Dit(E), was determined at oxide/III-N heterojunction interfaces in the entire band gap, using two complementary photo-electric methods: (i) photo-assisted capacitance-voltage technique for the states distributed near the midgap and the conduction band (CB) and (ii) light intensity dependent photo-capacitance method for the states close to the valence band (VB). In addition, the Auger electron spectroscopy profiling was applied for the characterization of chemical composition of the interface region with the emphasis on carbon impurities, which can be responsible for the interface state creation. The studies were performed for the AlGaN/GaN metal-insulator-semiconductor heterostructures (MISH) with Al2O3 and SiO2 dielectric films and AlxGa1-x layers with x varying from 0.15 to 0.4 as well as for an Al2O3/InAlN/GaN MISH structure. For all structures, it was found that: (i) Dit(E) is an U-shaped continuum increasing from the midgap towards the CB and VB edges and (ii) interface states near the VB exhibit donor-like character. Furthermore, Dit(E) for SiO2/AlxGa1-x/GaN structures increased with rising x. It was also revealed that carbon impurities are not present in the oxide/III-N interface region, which indicates that probably the interface states are not related to carbon, as previously reported. Finally, it was proven that the obtained Dit(E) spectrum can be well fitted using a formula predicted by the disorder induced gap state model. This is an indication that the interface states at oxide/III-N interfaces can originate from the structural disorder of the interfacial region. Furthermore, at the oxide/barrier interface we revealed the presence of the positive fixed charge (QF) which is not related to Dit(E) and which almost compensates the negative polarization charge ( Qp o l - ).

  7. Impact of La2O3 interfacial layers on InGaAs metal-oxide-semiconductor interface properties in Al2O3/La2O3/InGaAs gate stacks deposited by atomic-layer-deposition

    Science.gov (United States)

    Chang, C.-Y.; Ichikawa, O.; Osada, T.; Hata, M.; Yamada, H.; Takenaka, M.; Takagi, S.

    2015-08-01

    We examine the electrical properties of atomic layer deposition (ALD) La2O3/InGaAs and Al2O3/La2O3/InGaAs metal-oxide-semiconductor (MOS) capacitors. It is found that the thick ALD La2O3/InGaAs interface provides low interface state density (Dit) with the minimum value of ˜3 × 1011 cm-2 eV-1, which is attributable to the excellent La2O3 passivation effect for InGaAs surfaces. It is observed, on the other hand, that there are a large amount of slow traps and border traps in La2O3. In order to simultaneously satisfy low Dit and small hysteresis, the effectiveness of Al2O3/La2O3/InGaAs gate stacks with ultrathin La2O3 interfacial layers is in addition evaluated. The reduction of the La2O3 thickness to 0.4 nm in Al2O3/La2O3/InGaAs gate stacks leads to the decrease in hysteresis. On the other hand, Dit of the Al2O3/La2O3/InGaAs interfaces becomes higher than that of the La2O3/InGaAs ones, attributable to the diffusion of Al2O3 through La2O3 into InGaAs and resulting modification of the La2O3/InGaAs interface structure. As a result of the effective passivation effect of La2O3 on InGaAs, however, the Al2O3/10 cycle (0.4 nm) La2O3/InGaAs gate stacks can realize still lower Dit with maintaining small hysteresis and low leakage current than the conventional Al2O3/InGaAs MOS interfaces.

  8. Methods for synthesizing metal oxide nanowires

    Science.gov (United States)

    Sunkara, Mahendra Kumar; Kumar, Vivekanand; Kim, Jeong H.; Clark, Ezra Lee

    2016-08-09

    A method of synthesizing a metal oxide nanowire includes the steps of: combining an amount of a transition metal or a transition metal oxide with an amount of an alkali metal compound to produce a mixture; activating a plasma discharge reactor to create a plasma discharge; exposing the mixture to the plasma discharge for a first predetermined time period such that transition metal oxide nanowires are formed; contacting the transition metal oxide nanowires with an acid solution such that an alkali metal ion is exchanged for a hydrogen ion on each of the transition metal oxide nanowires; and exposing the transition metal oxide nanowires to the plasma discharge for a second predetermined time period to thermally anneal the transition metal oxide nanowires. Transition metal oxide nanowires produced using the synthesis methods described herein are also provided.

  9. Dynamical behaviour of the resistive switching in ceramic YBCO/metal interfaces

    International Nuclear Information System (INIS)

    Acha, C

    2011-01-01

    Studies related to the dynamics of resistive switching (RS) in ceramic YBCO/metal interfaces were performed. The change in interface resistance during the application of square pulses and its current-voltage (I-V) characteristics were measured. The obtained non-linear current dependence of the differential resistance can be very well reproduced by modelling the electrical behaviour of the interface with simple circuit elements. The RS produces defined changes in the parameters of the circuit model that reveal the particular dynamics of the mechanism beneath the resistance change in complex oxide/metal interfaces.

  10. The 2016 oxide electronic materials and oxide interfaces roadmap

    DEFF Research Database (Denmark)

    Lorenz, M.; Rao, M. S. Ramachandra; Venkatesan, T.

    2016-01-01

    , spintronics, thermoelectrics, piezoelectrics, power harvesting, hydrogen storage and environmental waste management. Synthesis and fabrication of these materials, as well as processing into particular device structures to suit a specific application is still a challenge. Further, characterization......Oxide electronic materials provide a plethora of possible applications and offer ample opportunity for scientists to probe into some of the exciting and intriguing phenomena exhibited by oxide systems and oxide interfaces. In addition to the already diverse spectrum of properties, the nanoscale...... form of oxides provides a new dimension of hitherto unknown phenomena due to the increased surface-to-volume ratio. Oxide electronic materials are becoming increasingly important in a wide range of applications including transparent electronics, optoelectronics, magnetoelectronics, photonics...

  11. High-mobility two-dimensional electron gases at oxide interfaces: Origins and opportunities

    DEFF Research Database (Denmark)

    Chen, Yunzhong; Pryds, Nini; Sun, Ji-Rong

    2013-01-01

    Our recent experimental work on metallic and insulating interfaces controlled by interfacial redox reactions in SrTiO3-based heterostructures is reviewed along with a more general background of two-dimensional electron gas (2DEG) at oxide interfaces. Due to the presence of oxygen vacancies at the...

  12. Oxide Interfaces: emergent structure and dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Clarke, Roy [Univ. of Michigan, Ann Arbor, MI (United States)

    2016-08-16

    This Final Report describes the scientific accomplishments that have been achieved with support from grant DE-FG02-06ER46273 during the period 6/1/2012– 5/31/2016. The overall goals of this program were focused on the behavior of epitaxial oxide heterostructures at atomic length scales (Ångstroms), and correspondingly short time-scales (fs -ns). The results contributed fundamentally to one of the currently most active frontiers in condensed matter physics research, namely to better understand the intricate relationship between charge, lattice, orbital and spin degrees of freedom that are exhibited by complex oxide heterostructures. The findings also contributed towards an important technological goal which was to achieve a better basic understanding of structural and electronic correlations so that the unusual properties of complex oxides can be exploited for energy-critical applications. Specific research directions included: probing the microscopic behavior of epitaxial interfaces and buried layers; novel materials structures that emerge from ionic and electronic reconfiguration at epitaxial interfaces; ultrahigh-resolution mapping of the atomic structure of heterointerfaces using synchrotron-based x-ray surface scattering, including direct methods of phase retrieval; using ultrafast lasers to study the effects of transient strain on coherent manipulation of multi-ferroic order parameters; and investigating structural ordering and relaxation processes in real-time.

  13. Multifunctional phosphonic acid self-assembled monolayers on metal oxides as dielectrics, interface modification layers and semiconductors for low-voltage high-performance organic field-effect transistors.

    Science.gov (United States)

    Ma, Hong; Acton, Orb; Hutchins, Daniel O; Cernetic, Nathan; Jen, Alex K-Y

    2012-11-07

    Insulating and semiconducting molecular phosphonic acid (PA) self-assembled monolayers (SAMs) have been developed for applications in organic field-effect transistors (OFETs) for low-power, low-cost flexible electronics. Multifunctional SAMs on ultrathin metal oxides, such as hafnium oxide and aluminum oxide, are shown to enable (1) low-voltage (sub 2 V) OFETs through dielectric and interface engineering on rigid and plastic substrates, (2) simultaneous one-component modification of source-drain and dielectric surfaces in bottom-contact OFETs, and (3) SAM-FETs based on molecular monolayer semiconductors. The combination of excellent dielectric and interfacial properties results in high-performance OFETs with low-subthreshold slopes down to 75 mV dec(-1), high I(on)/I(off) ratios of 10(5)-10(7), contact resistance down to 700 Ω cm, charge carrier mobilities of 0.1-4.6 cm(2) V(-1) s(-1), and general applicability to solution-processed and vacuum-deposited n-type and p-type organic and polymer semiconductors.

  14. Preparation of uniform nanoparticles of ultra-high purity metal oxides, mixed metal oxides, metals, and metal alloys

    Science.gov (United States)

    Woodfield, Brian F.; Liu, Shengfeng; Boerio-Goates, Juliana; Liu, Qingyuan; Smith, Stacey Janel

    2012-07-03

    In preferred embodiments, metal nanoparticles, mixed-metal (alloy) nanoparticles, metal oxide nanoparticles and mixed-metal oxide nanoparticles are provided. According to embodiments, the nanoparticles may possess narrow size distributions and high purities. In certain preferred embodiments, methods of preparing metal nanoparticles, mixed-metal nanoparticles, metal oxide nanoparticles and mixed-metal nanoparticles are provided. These methods may provide tight control of particle size, size distribution, and oxidation state. Other preferred embodiments relate to a precursor material that may be used to form nanoparticles. In addition, products prepared from such nanoparticles are disclosed.

  15. High-temperature catalytic reforming of n-hexane over supported and core-shell Pt nanoparticle catalysts: role of oxide-metal interface and thermal stability.

    Science.gov (United States)

    An, Kwangjin; Zhang, Qiao; Alayoglu, Selim; Musselwhite, Nathan; Shin, Jae-Youn; Somorjai, Gabor A

    2014-08-13

    Designing catalysts with high thermal stability and resistance to deactivation while simultaneously maintaining their catalytic activity and selectivity is of key importance in high-temperature reforming reactions. We prepared Pt nanoparticle catalysts supported on either mesoporous SiO2 or TiO2. Sandwich-type Pt core@shell catalysts (SiO2@Pt@SiO2 and SiO2@Pt@TiO2) were also synthesized from Pt nanoparticles deposited on SiO2 spheres, which were encapsulated by either mesoporous SiO2 or TiO2 shells. n-Hexane reforming was carried out over these four catalysts at 240-500 °C with a hexane/H2 ratio of 1:5 to investigate thermal stability and the role of the support. For the production of high-octane gasoline, branched C6 isomers are more highly desired than other cyclic, aromatic, and cracking products. Over Pt/TiO2 catalyst, production of 2-methylpentane and 3-methylpentane via isomerization was increased selectively up to 420 °C by charge transfer at Pt-TiO2 interfaces, as compared to Pt/SiO2. When thermal stability was compared between supported catalysts and sandwich-type core@shell catalysts, the Pt/SiO2 catalyst suffered sintering above 400 °C, whereas the SiO2@Pt@SiO2 catalyst preserved the Pt nanoparticle size and shape up to 500 °C. The SiO2@Pt@TiO2 catalyst led to Pt nanoparticle sintering due to incomplete protection of the TiO2 shells during the reaction at 500 °C. Interestingly, over the Pt/TiO2 catalyst, the average size of Pt nanoparticles was maintained even after 500 °C without sintering. In situ ambient pressure X-ray photoelectron spectroscopy demonstrated that the Pt/TiO2 catalyst did not exhibit TiO2 overgrowth on the Pt surface or deactivation by Pt sintering up to 600 °C. The extraordinarily high stability of the Pt/TiO2 catalyst promoted high reaction rates (2.0 μmol · g(-1) · s(-1)), which was 8 times greater than other catalysts and high isomer selectivity (53.0% of C6 isomers at 440 °C). By the strong metal-support interaction

  16. Fundamentals of metal oxide catalysis

    Science.gov (United States)

    Nair, Hari

    The properties of metal oxide catalysts and hence, catalytic activity are highly dependent on the composition and structure of these oxides. This dissertation has 3 parts -- all directed towards understanding relationships between structure, composition and activity in metal oxide catalysts. The first part of this dissertation focuses on supported metal oxide catalysts of tungsten, vanadium and molybdenum. Mechanisms are proposed for ethanol oxidative dehydrogenation which is used to probe the acidity and reducibility of these oxide catalysts. These studies are then used to develop a novel method to quantify active redox sites and determine the nature of the active site on these catalysts -- our results show that the intrinsic redox turn-over frequency is independent of the nature of the metal oxide and its loading and that the actual rate obtained over an oxide is only a function of the number of removable oxygen atoms linking the metal to the support. The extension of Ultraviolet-visible Diffuse Reflectance Spectroscopy (UV-vis DRS) to the study of active oxide domains in binary oxide catalysts is demonstrated for distinguishing between interacting and non-interacting domains in binary MoO x-WOx catalysts on alumina. We show also how the rigorous analysis of pre-edge features, absorption white-line intensity and the full width at half maximum of the white-line in X-ray Absorption Spectra provide determinants for metal atom coordination and domain size in supported metal oxide catalysts. The second part of this work looks at effects of structure variations on the activity of polyoxometalate catalysts that are promising for the production of Methacrylic Acid from Isobutane. The use of these catalysts is limited by structural changes that impact their performance -- an "activation" period is required before the catalysts become active for methacrylic acid production and structural changes also lead to degradation of the catalyst, which are also seen during thermal

  17. The 2016 oxide electronic materials and oxide interfaces roadmap

    International Nuclear Information System (INIS)

    Lorenz, M; Grundmann, M; Ramachandra Rao, M S; Mukherjee, J; Priyadarshini, M; Venkatesan, T; Fortunato, E; Barquinha, P; Branquinho, R; Salgueiro, D; Martins, R; Carlos, E; Liu, A; Shan, F K; Boschker, H; DasGupta, N; Rogers, D J; Teherani, F H; Sandana, E V; Bove, P

    2016-01-01

    Oxide electronic materials provide a plethora of possible applications and offer ample opportunity for scientists to probe into some of the exciting and intriguing phenomena exhibited by oxide systems and oxide interfaces. In addition to the already diverse spectrum of properties, the nanoscale form of oxides provides a new dimension of hitherto unknown phenomena due to the increased surface-to-volume ratio. Oxide electronic materials are becoming increasingly important in a wide range of applications including transparent electronics, optoelectronics, magnetoelectronics, photonics, spintronics, thermoelectrics, piezoelectrics, power harvesting, hydrogen storage and environmental waste management. Synthesis and fabrication of these materials, as well as processing into particular device structures to suit a specific application is still a challenge. Further, characterization of these materials to understand the tunability of their properties and the novel properties that evolve due to their nanostructured nature is another facet of the challenge. The research related to the oxide electronic field is at an impressionable stage, and this has motivated us to contribute with a roadmap on ‘oxide electronic materials and oxide interfaces’. This roadmap envisages the potential applications of oxide materials in cutting edge technologies and focuses on the necessary advances required to implement these materials, including both conventional and novel techniques for the synthesis, characterization, processing and fabrication of nanostructured oxides and oxide-based devices. The contents of this roadmap will highlight the functional and correlated properties of oxides in bulk, nano, thin film, multilayer and heterostructure forms, as well as the theoretical considerations behind both present and future applications in many technologically important areas as pointed out by Venkatesan. The contributions in this roadmap span several thematic groups which are represented by

  18. From Two-Phase to Three-Phase: The New Electrochemical Interface by Oxide Electrocatalysts

    Science.gov (United States)

    Xu, Zhichuan J.

    2018-03-01

    Electrochemical reactions typically occur at the interface between a solid electrode and a liquid electrolyte. The charge exchange behaviour between these two phases determines the kinetics of electrochemical reactions. In the past few years, significant advances have been made in the development of metal oxide electrocatalysts for fuel cell and electrolyser reactions. However, considerable gaps remain in the fundamental understanding of the charge transfer pathways and the interaction between the metal oxides and the conducting substrate on which they are located. In particular, the electrochemical interfaces of metal oxides are significantly different from the traditional (metal) ones, where only a conductive solid electrode and a liquid electrolyte are considered. Oxides are insulating and have to be combined with carbon as a conductive mediator. This electrode configuration results in a three-phase electrochemical interface, consisting of the insulating oxide, the conductive carbon, and the liquid electrolyte. To date, the mechanistic insights into this kind of non-traditional electrochemical interface remain unclear. Consequently conventional electrochemistry concepts, established on classical electrode materials and their two-phase interfaces, are facing challenges when employed for explaining these new electrode materials. [Figure not available: see fulltext.

  19. Electronic and chemical structure of metal-silicon interfaces

    Science.gov (United States)

    Grunthaner, P. J.; Grunthaner, F. J.

    1984-01-01

    This paper reviews our current understanding of the near-noble metal silicides and the interfaces formed with Si(100). Using X-ray photoemission spectroscopy, we compare the chemical composition and electronic structure of the room temperature metal-silicon and reacted silicide-silicon interfaces. The relationship between the interfacial chemistry and the Schottky barrier heights for this class of metals on silicon is explored.

  20. Thermal annealing effects on the interface state density of metal-oxide-semiconductor capacitors with electron cyclotron resonance plasma enhanced chemical vapor deposition Silicon dioxide

    Energy Technology Data Exchange (ETDEWEB)

    Maiolo, L. [Istituto di Fotonica e Nanotecnologie (IFN), CNR, Via Cineto Romano 42, 00156 Rome (Italy)], E-mail: lmaiolo@ifn.cnr.it; Pecora, A.; Cuscuna, M.; Fortunato, G. [Istituto di Fotonica e Nanotecnologie (IFN), CNR, Via Cineto Romano 42, 00156 Rome (Italy)

    2007-07-16

    Silicon dioxide films (SiO{sub 2}), deposited at room temperature by electron cyclotron resonance (ECR) plasma reactor from a gas phase combination of O{sub 2}, SiH{sub 4} and He, present excellent structural and electrical properties. However, when fabricating field effect devices it is also crucial to minimize the defect density at the semiconductor/insulator interface. We show that the interface state density, investigated in Al/SiO{sub 2}/Si MOS capacitors, can be substantially reduced performing post-deposition annealing. In particular we studied the effects of annealing temperature and time in different gas ambient: vacuum, nitrogen and forming gas (5% H{sub 2} + N{sub 2}). We found that interface state passivation mainly occurs when thermal annealing is performed after Al-contact deposition and that it is quite insensitive to the annealing atmosphere. The present results clearly suggest that the hydrogen passivation mechanism is driven by the H-containing species present in the film and a possible mechanism to explain the results is proposed.

  1. Thermal annealing effects on the interface state density of metal-oxide-semiconductor capacitors with electron cyclotron resonance plasma enhanced chemical vapor deposition Silicon dioxide

    International Nuclear Information System (INIS)

    Maiolo, L.; Pecora, A.; Cuscuna, M.; Fortunato, G.

    2007-01-01

    Silicon dioxide films (SiO 2 ), deposited at room temperature by electron cyclotron resonance (ECR) plasma reactor from a gas phase combination of O 2 , SiH 4 and He, present excellent structural and electrical properties. However, when fabricating field effect devices it is also crucial to minimize the defect density at the semiconductor/insulator interface. We show that the interface state density, investigated in Al/SiO 2 /Si MOS capacitors, can be substantially reduced performing post-deposition annealing. In particular we studied the effects of annealing temperature and time in different gas ambient: vacuum, nitrogen and forming gas (5% H 2 + N 2 ). We found that interface state passivation mainly occurs when thermal annealing is performed after Al-contact deposition and that it is quite insensitive to the annealing atmosphere. The present results clearly suggest that the hydrogen passivation mechanism is driven by the H-containing species present in the film and a possible mechanism to explain the results is proposed

  2. Tuning the conductivity threshold and carrier density of two-dimensional electron gas at oxide interfaces through interface engineering

    Directory of Open Access Journals (Sweden)

    H. J. Harsan Ma

    2015-08-01

    Full Text Available The two-dimensional electron gas (2DEG formed at the perovskite oxides heterostructures is of great interest because of its potential applications in oxides electronics and nanoscale multifunctional devices. A canonical example is the 2DEG at the interface between a polar oxide LaAlO3 (LAO and non-polar SrTiO3 (STO. Here, the LAO polar oxide can be regarded as the modulating or doping layer and is expected to define the electronic properties of 2DEG at the LAO/STO interface. However, to practically implement the 2DEG in electronics and device design, desired properties such as tunable 2D carrier density are necessary. Here, we report the tuning of conductivity threshold, carrier density and electronic properties of 2DEG in LAO/STO heterostructures by insertion of a La0.5Sr0.5TiO3 (LSTO layer of varying thicknesses, and thus modulating the amount of polarization of the oxide over layers. Our experimental result shows an enhancement of carrier density up to a value of about five times higher than that observed at the LAO/STO interface. A complete thickness dependent metal-insulator phase diagram is obtained by varying the thickness of LAO and LSTO providing an estimate for the critical thickness needed for the metallic phase. The observations are discussed in terms of electronic reconstruction induced by polar oxides.

  3. Making A Noble-Metal-On-Metal-Oxide Catalyst

    Science.gov (United States)

    Miller, Irvin M.; Davis, Patricia P.; Upchurch, Billy T.

    1989-01-01

    Catalyst exhibits superior performance in oxidation of CO in CO2 lasers. Two-step process developed for preparing platinum- or palladium-on-tin-oxide catalyst for recombination of CO and O2, decomposition products that occur in high-voltage discharge region of closed-cycle CO2 laser. Process also applicable to other noble-metal/metal-oxide combinations.

  4. Direct plutonium oxide reduction/electrorefining interface program

    International Nuclear Information System (INIS)

    Baldwin, C.E.; Berry, J.W.; Giebel, R.E.; Long, J.L.; Moser, W.S.; Navratil, J.D.; Tibbitts, S.F.

    1986-01-01

    Research test work and production data evaluation were performed by the Direct Oxide Reduction (DOR)/Electrorefining (ER) Interface Task Team to determine the cause for poor efficiency and yields during ER of DOR metal product. Production data and preliminary test results provided a working hypothesis. Extremely high loadings of impurities (whatever their exact source and identity) in the DOR product metal may lead to failure of the metal to become a molten anode at ER operating temperatures. Moderate impurity levels permit attainment of a molten anode, but lead to low yields because of premature anode solidification. The test results did not conclusively prove the hypothesis or identify specific mechanisms, but were qualitatively supportive. By stirring the molten anode metal pool, as well as the molten salt phase, generally good ER runs were obtained with both DOR and non-DOR feeds. These limited preliminary results suggest that anode stirring decreases the sensitivity of the ER process to DOR-related impurities. Suggested corrective measures included: (1) minimizing impurities in DOR feed to ER and (2) continued evaluation of anode stirring along with run termination by back-EMF measurements. 1 ref., 3 figs., 13 tabs

  5. Nanostructured transition metal oxides useful for water oxidation catalysis

    Science.gov (United States)

    Frei, Heinz M; Jiao, Feng

    2013-12-24

    The present invention provides for a composition comprising a nanostructured transition metal oxide capable of oxidizing two H.sub.2O molecules to obtain four protons. In some embodiments of the invention, the composition further comprises a porous matrix wherein the nanocluster of the transition metal oxide is embedded on and/or in the porous matrix.

  6. Method for producing metal oxide nanoparticles

    Science.gov (United States)

    Phillips, Jonathan [Santa Fe, NM; Mendoza, Daniel [Santa Fe, NM; Chen, Chun-Ku [Albuquerque, NM

    2008-04-15

    Method for producing metal oxide nanoparticles. The method includes generating an aerosol of solid metallic microparticles, generating plasma with a plasma hot zone at a temperature sufficiently high to vaporize the microparticles into metal vapor, and directing the aerosol into the hot zone of the plasma. The microparticles vaporize in the hot zone into metal vapor. The metal vapor is directed away from the hot zone and into the cooler plasma afterglow where it oxidizes, cools and condenses to form solid metal oxide nanoparticles.

  7. Engineering magnetism at functional oxides interfaces: manganites and beyond.

    Science.gov (United States)

    Yi, Di; Lu, Nianpeng; Chen, Xuegang; Shen, Shengchun; Yu, Pu

    2017-11-08

    The family of transition metal oxides (TMOs) is a large class of magnetic materials that has been intensively studied due to the rich physics involved as well as the promising potential applications in next generation electronic devices. In TMOs, the spin, charge, orbital and lattice are strongly coupled, and significant advances have been achieved to engineer the magnetism by different routes that manipulate these degrees of freedom. The family of manganites is a model system of strongly correlated magnetic TMOs. In this review, using manganites thin films and the heterostructures in conjunction with other TMOs as model systems, we review the recent progress of engineering magnetism in TMOs. We first discuss the role of the lattice that includes the epitaxial strain and the interface structural coupling. Then we look into the role of charge, focusing on the interface charge modulation. Having demonstrated the static effects, we continue to review the research on dynamical control of magnetism by electric field. Next, we review recent advances in heterostructures comprised of high T c cuprate superconductors and manganites. Following that, we discuss the emergent magnetic phenomena at interfaces between 3d TMOs and 5d TMOs with strong spin-orbit coupling. Finally, we provide our outlook for prospective future directions.

  8. Metal Detector By Using PIC Microcontroller Interfacing With PC

    Directory of Open Access Journals (Sweden)

    Yin Min Theint

    2015-06-01

    Full Text Available Abstract This system proposes metal detector by using PIC microcontroller interfacing with PC. The system uses PIC microcontroller as the main controller whether the detected metal is ferrous metal or non-ferrous metal. Among various types of metal sensors and various types of metal detecting technologies concentric type induction coil sensor and VLF very low frequency metal detecting technology are used in this system. This system consists of two configurations Hardware configuration and Software configuration. The hardware components include induction coil sensors which senses the frequency changes of metal a PIC microcontroller personal computer PC buzzer light emitting diode LED and webcam. The software configuration includes a program controller interface. PIC MikroCprogramming language is used to implement the control system. This control system is based on the PIC 16F887 microcontroller.This system is mainly used in mining and high security places such as airport plaza shopping mall and governmental buildings.

  9. Nanoparticular metal oxide/anatase catalysts

    DEFF Research Database (Denmark)

    2010-01-01

    the catalyst metai oxide is co-precipitated with the carrier metal oxide, which crystallization seeds are removed by combustion in a final calcining step. The present invention also concerns processes wherein the nanoparticular metal oxide catalysts of the invention are used, such as SCR (deNOx) reactions...

  10. A Subnanoscale Investigation of Sb Segregation at MnO/Ag Ceramic/Metal Interfaces

    NARCIS (Netherlands)

    Sebastian, Jason T.; Assaban, Albert; Seidman, David N.; Kooi, Bart J.; Hosson, Jeff Th.M. De

    2001-01-01

    We have studied Sb segregation at MnO/Ag(Sb) ceramic/metal heterophase interfaces employing three-dimensional atom-probe (3DAP) microscopy. Specimens are prepared by the internal oxidation of Ag(Mn) alloys, leading to the formation of nanometer-size MnO precipitates within a Ag(Mn) matrix. Sb is

  11. Method of physical vapor deposition of metal oxides on semiconductors

    Science.gov (United States)

    Norton, David P.

    2001-01-01

    A process for growing a metal oxide thin film upon a semiconductor surface with a physical vapor deposition technique in a high-vacuum environment and a structure formed with the process involves the steps of heating the semiconductor surface and introducing hydrogen gas into the high-vacuum environment to develop conditions at the semiconductor surface which are favorable for growing the desired metal oxide upon the semiconductor surface yet is unfavorable for the formation of any native oxides upon the semiconductor. More specifically, the temperature of the semiconductor surface and the ratio of hydrogen partial pressure to water pressure within the vacuum environment are high enough to render the formation of native oxides on the semiconductor surface thermodynamically unstable yet are not so high that the formation of the desired metal oxide on the semiconductor surface is thermodynamically unstable. Having established these conditions, constituent atoms of the metal oxide to be deposited upon the semiconductor surface are directed toward the surface of the semiconductor by a physical vapor deposition technique so that the atoms come to rest upon the semiconductor surface as a thin film of metal oxide with no native oxide at the semiconductor surface/thin film interface. An example of a structure formed by this method includes an epitaxial thin film of (001)-oriented CeO.sub.2 overlying a substrate of (001) Ge.

  12. Atomistic calculations of interface elastic properties in noncoherent metallic bilayers

    International Nuclear Information System (INIS)

    Mi Changwen; Jun, Sukky; Kouris, Demitris A.; Kim, Sung Youb

    2008-01-01

    The paper describes theoretical and computational studies associated with the interface elastic properties of noncoherent metallic bicrystals. Analytical forms of interface energy, interface stresses, and interface elastic constants are derived in terms of interatomic potential functions. Embedded-atom method potentials are then incorporated into the model to compute these excess thermodynamics variables, using energy minimization in a parallel computing environment. The proposed model is validated by calculating surface thermodynamic variables and comparing them with preexisting data. Next, the interface elastic properties of several fcc-fcc bicrystals are computed. The excess energies and stresses of interfaces are smaller than those on free surfaces of the same crystal orientations. In addition, no negative values of interface stresses are observed. Current results can be applied to various heterogeneous materials where interfaces assume a prominent role in the systems' mechanical behavior

  13. Aerobic Oxidations of Light Alkanes over Solid Metal Oxide Catalysts.

    Science.gov (United States)

    Grant, Joseph T; Venegas, Juan M; McDermott, William P; Hermans, Ive

    2017-11-07

    Heterogeneous metal oxide catalysts are widely studied for the aerobic oxidations of C 1 -C 4 alkanes to form olefins and oxygenates. In this review, we outline the properties of supported metal oxides, mixed-metal oxides, and zeolites and detail their most common applications as catalysts for partial oxidations of light alkanes. By doing this we establish similarities between different classes of metal oxides and identify common themes in reaction mechanisms and research strategies for catalyst improvement. For example, almost all partial alkane oxidations, regardless of the metal oxide, follow Mars-van Krevelen reaction kinetics, which utilize lattice oxygen atoms to reoxidize the reduced metal centers while the gaseous O 2 reactant replenishes these lattice oxygen vacancies. Many of the most-promising metal oxide catalysts include V 5+ surface species as a necessary constituent to convert the alkane. Transformations involving sequential oxidation steps (i.e., propane to acrylic acid) require specific reaction sites for each oxidation step and benefit from site isolation provided by spectator species. These themes, and others, are discussed in the text.

  14. Metal Oxide Solubility and Molten Salt Corrosion.

    Science.gov (United States)

    1982-03-29

    soluble oxides that relations like eq. (3) are significant. The oxides of several metal oxides have been found to be amphoteric , i.e., their solution...METAL OXIDE SOLUBILITY AND MOLTEN SALT CORROSION.(U) MAR 82 K H STERN UNCLASSI E DL R L-4772NL EL .2. MICROCOPY RESOLUTION TEST CHART NATIONAL BURALU...METAL OXIDE SOLUBILITY AND MOLTEN SALT Interim report on a continuing CORROSION NRL problem. S. PERFORMING a4. REPORT NUMlER 7. AuTtwORr) S. CONTRACT OR

  15. Metal oxides for optoelectronic applications

    Science.gov (United States)

    Yu, Xinge; Marks, Tobin J.; Facchetti, Antonio

    2016-04-01

    Metal oxides (MOs) are the most abundant materials in the Earth's crust and are ingredients in traditional ceramics. MO semiconductors are strikingly different from conventional inorganic semiconductors such as silicon and III-V compounds with respect to materials design concepts, electronic structure, charge transport mechanisms, defect states, thin-film processing and optoelectronic properties, thereby enabling both conventional and completely new functions. Recently, remarkable advances in MO semiconductors for electronics have been achieved, including the discovery and characterization of new transparent conducting oxides, realization of p-type along with traditional n-type MO semiconductors for transistors, p-n junctions and complementary circuits, formulations for printing MO electronics and, most importantly, commercialization of amorphous oxide semiconductors for flat panel displays. This Review surveys the uniqueness and universality of MOs versus other unconventional electronic materials in terms of materials chemistry and physics, electronic characteristics, thin-film fabrication strategies and selected applications in thin-film transistors, solar cells, diodes and memories.

  16. Interface magnetism of 3d transition metals

    DEFF Research Database (Denmark)

    Niklasson, A. M. N.; Johansson, B.; Skriver, Hans Lomholt

    1999-01-01

    The layered resolved magnetic spin moments of the magnetic 3d bilayer interfaces Fe/V bcc, Fe/Co bcc, Fe/Cu bcc, Co/V bcc, Co/Ni fee, Co/Cu fee, Ni/V fee, Ni/Cr fcc, Ni/Cu fee and the magnetic surfaces Fe bcc, Co bcc, Co fee, and Ni fee are calculated for the (001), (011), and (111) orientations...... by means of a first-principles Green's function method. It is shown how the magnetic profiles around the bilayer interfaces and surfaces directly can be used to predict the magnetization of more complex systems such as magnetic multilayers and clusters. Furthermore, it is shown how the magnetic interface...... moments can be estimated from data of the corresponding binary bulk alloys. The behavior of interface magnetism can thus be traced back to the understanding of magnetism in bulk alloys. [:S0163-1829(99)04005-9]....

  17. Vacancy induced metallicity at the CaHfO3/SrTiO3 interface

    KAUST Repository

    Nazir, Safdar

    2011-03-31

    Density functional theory is used to study the electronic properties of the oxide heterointerfaceCaHfO3/SrTiO3. Structural relaxation is carried out with and without O vacancies. As compared to related interfaces, strongly reduced octahedral distortions are found. Stoichiometric interfaces between the wide band gap insulatorsCaHfO3 and SrTiO3 turn out to exhibit an insulating state. However, interface metallicity is introduced by O vacancies, in agreement with experiment. The reduced octahedral distortions and necessity of O deficiency indicate a less complicated mechanism for the creation of the interfacial electron gas.

  18. Reduction of Metal Oxide to Metal using Ionic Liquids

    Energy Technology Data Exchange (ETDEWEB)

    Dr. Ramana Reddy

    2012-04-12

    A novel pathway for the high efficiency production of metal from metal oxide means of electrolysis in ionic liquids at low temperature was investigated. The main emphasis was to eliminate the use of carbon and high temperature application in the reduction of metal oxides to metals. The emphasis of this research was to produce metals such as Zn, and Pb that are normally produced by the application of very high temperatures. The reduction of zinc oxide to zinc and lead oxide to lead were investigated. This study involved three steps in accomplishing the final goal of reduction of metal oxide to metal using ionic liquids: 1) Dissolution of metal oxide in an ionic liquid, 2) Determination of reduction potential using cyclic voltammetry (CV) and 3) Reduction of the dissolved metal oxide. Ionic liquids provide additional advantage by offering a wide potential range for the deposition. In each and every step of the process, more than one process variable has been examined. Experimental results for electrochemical extraction of Zn from ZnO and Pb from PbO using eutectic mixtures of Urea ((NH2)2CO) and Choline chloride (HOC2H4N(CH3)3+Cl-) or (ChCl) in a molar ratio 2:1, varying voltage and temperatures were carried out. Fourier Transform Infra-Red (FTIR) spectroscopy studies of ionic liquids with and without metal oxide additions were conducted. FTIR and induction coupled plasma spectroscopy (ICPS) was used in the characterization of the metal oxide dissolved ionic liquid. Electrochemical experiments were conducted using EG&G potentiostat/galvanostat with three electrode cell systems. Cyclic voltammetry was used in the determination of reduction potentials for the deposition of metals. Chronoamperometric experiments were carried out in the potential range of -0.6V to -1.9V for lead and -1.4V to -1.9V for zinc. The deposits were characterized using XRD and SEM-EDS for phase, morphological and elemental analysis. The results showed that pure metal was deposited on the cathode

  19. The comparison of gamma-radiation and electrical stress influences on oxide and interface defects in power VDMOSFET

    Directory of Open Access Journals (Sweden)

    Đorić-Veljković Snežana M.

    2013-01-01

    Full Text Available The behaviour of oxide and interface defects in n-channel power vertical double-diffused metal-oxide-semiconductor field-effect transistors, firstly degraded by the gamma-irradiation and electric field and subsequently recovered and annealed, is presented. By analyzing the transfer characteristic shifts, the changes of threshold voltage and underlying changes of gate oxide and interface trap densities during the stress (recovery, annealing of investigated devices, it is shown that these two types of stress influence differently on the gate oxide and the SiO2-Si interface. [Projekat Ministarstva nauke Republike Srbije, br. OI171026

  20. Two-dimensional transition metal dichalcogenides: interface and defect engineering.

    Science.gov (United States)

    Hu, Zehua; Wu, Zhangting; Han, Cheng; He, Jun; Ni, Zhenhua; Chen, Wei

    2018-03-06

    Two-dimensional (2D) transition metal dichalcogenides (TMDCs) have been considered as promising candidates for next generation nanoelectronics. Because of their atomically-thin structure and high surface to volume ratio, the interfaces involved in TMDC-based devices play a predominant role in determining the device performance, such as charge injection/collection at the metal/TMDC interface, and charge carrier trapping at the dielectric/TMDC interface. On the other hand, the crystalline structures of TMDCs are enriched by a variety of intrinsic defects, including vacancies, adatoms, grain boundaries, and substitutional impurities. Customized design and engineering of the interfaces and defects provides an effective way to modulate the properties of TMDCs and finally enhance the device performance. Herein, we summarize and highlight recent advances and state-of-the-art investigations on the interface and defect engineering of TMDCs and their corresponding applications in electronic and optoelectronic devices. Various interface engineering approaches for TMDCs are overviewed, including surface charge transfer doping, TMDC/metal contact engineering, and TMDC/dielectric interface engineering. Subsequently, different types of structural defects in TMDCs are introduced. Defect engineering strategies utilized to modulate the optical and electronic properties of TMDCs, as well as the developed high-performance and functional devices are summarized. Finally, we highlight the challenges and opportunities for interface and defect engineering in TMDC materials for electronics and optoelectronics.

  1. Metal-semiconductor interface in extreme temperature conditions

    International Nuclear Information System (INIS)

    Bulat, L.P.; Erofeeva, I.A.; Vorobiev, Yu.V.; Gonzalez-Hernandez, J.

    2008-01-01

    We present an investigation of electrons' and phonons' temperatures in the volume of a semiconductor (or metal) sample and at the interface between metal and semiconductor. Two types of mismatch between electrons' and phonons' temperatures take place: at metal-semiconductor interfaces and in the volume of the sample. The temperature mismatch leads to nonlinear terms in expressions for heat and electricity transport. The nonlinear effects should be taken into consideration in the study of electrical and heat transport in composites and in electronic chips

  2. Pulsed laser deposition: metal versus oxide ablation

    NARCIS (Netherlands)

    Doeswijk, L.M.; Rijnders, Augustinus J.H.M.; Blank, David H.A.

    2004-01-01

    We present experimental results of pulsed laser interaction with metal (Ni, Fe, Nb) and oxide (TiO2, SrTiO3, BaTiO3) targets. The influence of the laser fluence and the number of laser pulses on the resulting target morphology are discussed. Although different responses for metal and oxide targets

  3. Nanocomposite of graphene and metal oxide materials

    Science.gov (United States)

    Liu, Jun; Aksay, Ilhan A.; Choi, Daiwon; Wang, Donghai; Yang, Zhenguo

    2012-09-04

    Nanocomposite materials comprising a metal oxide bonded to at least one graphene material. The nanocomposite materials exhibit a specific capacity of at least twice that of the metal oxide material without the graphene at a charge/discharge rate greater than about 10C.

  4. Nanocomposite of graphene and metal oxide materials

    Science.gov (United States)

    Liu, Jun; Aksay, Ilhan A.; Choi, Daiwon; Wang, Donghai; Yang, Zhenguo

    2013-10-15

    Nanocomposite materials comprising a metal oxide bonded to at least one graphene material. The nanocomposite materials exhibit a specific capacity of at least twice that of the metal oxide material without the graphene at a charge/discharge rate greater than about 10 C.

  5. Self-sustained cycle of hydrolysis and etching at solution/solid interfaces: a general strategy to prepare metal oxide micro-/nanostructured arrays for high-performance electrodes.

    Science.gov (United States)

    Zhang, Yingmeng; Zhang, Weixin; Yang, Zeheng; Gu, Heyun; Zhu, Qing; Yang, Shihe; Li, Mei

    2015-03-23

    Assembling micro-/nanostructured arrays on conducting substrates allows the integration of multiple functionalities into modern electronic devices. Herein, a novel self-sustained cycle of hydrolysis and etching (SCHE) is exploited to selectively synthesize an extensive series of metal oxide micro-/nanostructured arrays on a wide range of metal substrates, establishing the generality and efficacy of the strategy. To demonstrate the potential application of this method, the as-prepared NiO porous nanobelt array was directly used as the anode for lithium-ion batteries, exhibiting excellent capacity and rate capability. Conclusively, the SCHE strategy offers a systematic approach to design metal oxide micro-/nanostructured arrays on metal substrates, which are valuable not only for lithium-ion batteries but also for other energy conversion and storage systems and electronic devices at large. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Methods of producing adsorption media including a metal oxide

    Science.gov (United States)

    Mann, Nicholas R; Tranter, Troy J

    2014-03-04

    Methods of producing a metal oxide are disclosed. The method comprises dissolving a metal salt in a reaction solvent to form a metal salt/reaction solvent solution. The metal salt is converted to a metal oxide and a caustic solution is added to the metal oxide/reaction solvent solution to adjust the pH of the metal oxide/reaction solvent solution to less than approximately 7.0. The metal oxide is precipitated and recovered. A method of producing adsorption media including the metal oxide is also disclosed, as is a precursor of an active component including particles of a metal oxide.

  7. High-mobility two-dimensional electron gases at oxide interfaces: Origin and opportunities

    International Nuclear Information System (INIS)

    Chen Yun-Zhong; Pryds Nini; Linderoth Søren; Sun Ji-Rong; Shen Bao-Gen

    2013-01-01

    Our recent experimental work on metallic and insulating interfaces controlled by interfacial redox reactions in SrTiO 3 -based heterostructures is reviewed along with a more general background of two-dimensional electron gas (2DEG) at oxide interfaces. Due to the presence of oxygen vacancies at the SrTiO 3 surface, metallic conduction can be created at room temperature in perovskite-type interfaces when the overlayer oxide ABO 3 has Al, Ti, Zr, or Hf elements at the B sites. Furthermore, relying on interface-stabilized oxygen vacancies, we have created a new type of 2DEG at the heterointerface between SrTiO 3 and a spinel γ-Al 2 O 3 epitaxial film with compatible oxygen ion sublattices. This 2DEG exhibits an electron mobility exceeding 100000 cm 2 V −1 s −1 , more than one order of magnitude higher than those of hitherto investigated perovskite-type interfaces. Our findings pave the way for the design of high-mobility all-oxide electronic devices and open a route toward the studies of mesoscopic physics with complex oxides. (topical review - magnetism, magnetic materials, and interdisciplinary research)

  8. Metal ion binding to iron oxides

    NARCIS (Netherlands)

    Hiemstra, T.; Riemsdijk, van W.H.; Benedetti, M.F.; Ponthieu, M.

    2006-01-01

    The biogeochemistry of trace elements (TE) is largely dependent upon their interaction with heterogeneous ligands including metal oxides and hydrous oxides of iron. The modeling of TE interactions with iron oxides has been pursued using a variety of chemical models. The objective of this work is to

  9. Effect of hydrogen on the integrity of aluminium–oxide interface at elevated temperatures

    KAUST Repository

    Li, Meng

    2017-02-20

    Hydrogen can facilitate the detachment of protective oxide layer off metals and alloys. The degradation is usually exacerbated at elevated temperatures in many industrial applications; however, its origin remains poorly understood. Here by heating hydrogenated aluminium inside an environmental transmission electron microscope, we show that hydrogen exposure of just a few minutes can greatly degrade the high temperature integrity of metal–oxide interface. Moreover, there exists a critical temperature of ∼150 °C, above which the growth of cavities at the metal–oxide interface reverses to shrinkage, followed by the formation of a few giant cavities. Vacancy supersaturation, activation of a long-range diffusion pathway along the detached interface and the dissociation of hydrogen-vacancy complexes are critical factors affecting this behaviour. These results enrich the understanding of hydrogen-induced interfacial failure at elevated temperatures.

  10. PREPARATION OF METAL OXIDE POWDERS FROM METAL LOADED VERSATIC ACID

    OpenAIRE

    KAKIHATA, Takayuki; USAMI, Kensuke; YAMAMOTO, Hideki; SHIBATA, Junji

    1998-01-01

    A production process for metal oxide powders was developed using a solvent extraction method. Versatic Acid 10 and D2EHPA solutions containing copper, zinc and nickel were used for a precipitation-stripping process, where oxalic acid was added to the solution as a precipitation reagent.Copper, zinc and nickel oxalates were easily formed in an aqueous phase, and 99.9% of precipitation was obtained for each metal during this process. These metal oxalates were easily converted to metal oxides by...

  11. Mismatch of dielectric constants at the interface of nanometer metal ...

    Indian Academy of Sciences (India)

    Abstract. The comparison of the inversion electron density between a nanometer metal-oxide- semiconductor (MOS) device with high-K gate dielectric and a SiO2 MOS device with the same equivalent oxide thickness has been discussed. A fully self-consistent solution of the coupled. Schrödinger–Poisson equations ...

  12. Catalytic dehydrogenation of light alkanes on metals and metal oxides

    NARCIS (Netherlands)

    Sattler, Jesper J H B|info:eu-repo/dai/nl/328235601; Ruiz-Martinez, Javier|info:eu-repo/dai/nl/341386405; Santillan-Jimenez, Eduardo|info:eu-repo/dai/nl/323171958; Weckhuysen, Bert M.|info:eu-repo/dai/nl/285484397

    2014-01-01

    A study is conducted to demonstrate catalytic dehydrogenation of light alkanes on metals and metal oxides. The study provides a complete overview of the materials used to catalyze this reaction, as dehydrogenation for the production of light olefins has become extremely relevant. Relevant factors,

  13. Metal oxide nanostructures as gas sensing devices

    CERN Document Server

    Eranna, G

    2016-01-01

    Metal Oxide Nanostructures as Gas Sensing Devices explores the development of an integrated micro gas sensor that is based on advanced metal oxide nanostructures and is compatible with modern semiconductor fabrication technology. This sensor can then be used to create a compact, low-power, handheld device for analyzing air ambience. The book first covers current gas sensing tools and discusses the necessity for miniaturized sensors. It then focuses on the materials, devices, and techniques used for gas sensing applications, such as resistance and capacitance variations. The author addresses the issues of sensitivity, concentration, and temperature dependency as well as the response and recovery times crucial for sensors. He also presents techniques for synthesizing different metal oxides, particularly those with nanodimensional structures. The text goes on to highlight the gas sensing properties of many nanostructured metal oxides, from aluminum and cerium to iron and titanium to zinc and zirconium. The final...

  14. Field enhancement at metallic interfaces due to quantum confinement

    DEFF Research Database (Denmark)

    Öztürk, Fatih; Xiao, Sanshui; Yan, Min

    2011-01-01

    We point out an apparently overlooked consequence of the boundary conditions obeyed by the electric displacement vector at air-metal interfaces: the continuity of the normal component combined with the quantum mechanical penetration of the electron gas in the air implies the existence of a surface...

  15. Surfing liquid metal droplet on the same metal bath via electrolyte interface

    Science.gov (United States)

    Zhao, Xi; Tang, Jianbo; Liu, Jing

    2017-09-01

    We report a phenomenon that when exerting an electric field gradient across a liquid metal/electrolyte interface, a droplet of the same liquid metal can persistently surf on the interface without coalescence. A thin layer of the intermediate solution, which separates the droplet from direct metallic contacting and provides levitating force, is responsible for such surfing effect. The electric resistance of this solution film is measured, and the film thickness is further theoretically calculated. The fact that the levitating state can be switched on and off via a controlled manner paves the way for reliably manipulating liquid metal droplets or devices.

  16. Electrochemical analysis of metal oxides

    Czech Academy of Sciences Publication Activity Database

    Grygar, Tomáš; Bezdička, Petr; Hradil, David; Pikna, L.

    90-91, - (2003), s. 45-50 ISSN 1012-0394 Institutional research plan: CEZ:AV0Z4032918 Keywords : powder electroanalysis * Fe oxides * Mn oxides Subject RIV: CA - Inorganic Chemistry Impact factor: 0.687, year: 2003

  17. Thin film metal-oxides

    CERN Document Server

    Ramanathan, Shriram

    2009-01-01

    Presents an account of the fundamental structure-property relations in oxide thin films. This title discusses the functional properties of thin film oxides in the context of applications in the electronics and renewable energy technologies.

  18. Interface reconstruction and dislocation networks for a metal/alumina interface: an atomistic approach

    International Nuclear Information System (INIS)

    Long, Y; Chen, N X

    2008-01-01

    Misfit dislocation is an important component of the semi-coherent interface. Usually, it forms a dislocation network as the strain concentration area on an interface and makes the other part coherent. This is the regular case, but there are also some exceptions. In this work, we show that the Ni/(Al 2 O 3 ) Al interface has a reconstruction at the first monolayer of the metal side, which works as a transition layer between Ni and Al 2 O 3 lattices. Under these conditions, the misfit dislocation cannot be confirmed by drawing a Burgers circuit because the interface is incoherent. However, due to the lattice misfit, there are areas of strain concentration and areas without strain distributed on the interface plane. So, for describing this strain distribution, we again use the concept of a dislocation network but redefine it as the separate line between these two parts. As a result, we find that the dislocation network appears when the metal part is thicker than 12.4 A, and it shrinks as the metal film grows, resulting in an ultimate structure with a mesh size of 28.1 A

  19. Hidden Interface Driven Exchange Coupling in Oxide Heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Aiping [Center for Integrated Nanotechnologies (CINT), Los Alamos National Laboratory, Los Alamos NM 87545 USA; Wang, Qiang [Materials Science Division, Argonne National Laboratory, Argonne IL 60439 USA; Department of Physics and Astronomy, West Virginia University, Morgantown WV 26506 USA; Fitzsimmons, Michael R. [Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge TN 37831 USA; Department of Physics and Astronomy, University of Tennessee, Knoxville TN 37996 USA; Enriquez, Erik [Center for Integrated Nanotechnologies (CINT), Los Alamos National Laboratory, Los Alamos NM 87545 USA; Weigand, Marcus [Center for Integrated Nanotechnologies (CINT), Los Alamos National Laboratory, Los Alamos NM 87545 USA; Harrell, Zach [Center for Integrated Nanotechnologies (CINT), Los Alamos National Laboratory, Los Alamos NM 87545 USA; McFarland, Brian [Center for Integrated Nanotechnologies (CINT), Los Alamos National Laboratory, Los Alamos NM 87545 USA; Lü, Xujie [Center for Integrated Nanotechnologies (CINT), Los Alamos National Laboratory, Los Alamos NM 87545 USA; Dowden, Paul [Center for Integrated Nanotechnologies (CINT), Los Alamos National Laboratory, Los Alamos NM 87545 USA; MacManus-Driscoll, Judith L. [Department of Materials Science, University of Cambridge, Cambridge CB3 OFS UK; Yarotski, Dmitry [Center for Integrated Nanotechnologies (CINT), Los Alamos National Laboratory, Los Alamos NM 87545 USA; Jia, Quanxi [Center for Integrated Nanotechnologies (CINT), Los Alamos National Laboratory, Los Alamos NM 87545 USA; Department of Materials Design and Innovation, University at Buffalo - The State University of New York, Buffalo NY 14260 USA

    2017-05-02

    A variety of emergent phenomena have been enabled by interface engineering in complex oxides. The existence of an intrinsic interfacial layer has often been found at oxide heterointerfaces. However, the role of such an interlayerin controlling functionalities is not fully explored. Here, we report the control of the exchange bias (EB) in single-phase manganite thin films with nominallyuniform chemical composition across the interfaces. The sign of EB depends on the magnitude of the cooling field. A pinned layer, confirmed by polarized neutron reflectometry, provides the source of unidirectional anisotropy. The origin of the exchange bias coupling is discussed in terms of magnetic interactions between the interfacial ferromagnetically reduced layer and the bulk ferromagnetic region. The sign of EB is related to the frustration of antiferromagnetic coupling between the ferromagnetic region and the pinned layer. Our results shed new light on using oxide interfaces to design functional spintronic devices.

  20. Graphene composites containing chemically bonded metal oxides

    Indian Academy of Sciences (India)

    Abstract. Composites of graphene involving chemically bonded nano films of metal oxides have been prepared by reacting graphene containing surface oxygen functionalities with metal halide vapours followed by exposure to water vapour. The composites have been characterized by electron microscopy, atomic force ...

  1. Graphene composites containing chemically bonded metal oxides

    Indian Academy of Sciences (India)

    Composites of graphene involving chemically bonded nano films of metal oxides have been prepared by reacting graphene containing surface oxygen functionalities with metal halide vapours followed by exposure to water vapour. The composites have been characterized by electron microscopy, atomic force microscopy ...

  2. Correlating the interface resistance and surface adhesion of the Li metal-solid electrolyte interface

    Science.gov (United States)

    Wang, Michael; Sakamoto, Jeff

    2018-02-01

    Solid electrolytes could enable stable cycling of metallic Li anodes, which can offer drastic increases to the capacity of Li-ion batteries. However, little is known about the mechanics of the Li-solid electrolyte interface. This study combines electrochemical and mechanical characterization to correlate interface kinetics with adhesive strength. Cubic garnet with the Li6·25Al0·25La3Zr2O12 (LLZO) formulation was selected as a model solid electrolyte based on its high conductivity and stability against Li metal. Symmetric Li-LLZO cells were tested using electrochemical impedance spectroscopy to determine the interfacial resistance, Rint, and the adhesive strength of the Li-LLZO interface, σadh, was measured using a unique tensile test in an inert atmosphere. It was determined that the Rint is directly correlated to the adhesive strength of Li on LLZO. At the highest Rint in this study, 330 k·cm2 the σadh was 1.1 kPa and at the lowest Rint in this study, 7 ·cm2, σadh was 8 MPa. Furthermore, by optimizing the surface chemistry the wettability of LLZO was enhanced resulting in σadh exceeding the ultimate tensile strength of Li metal. The relationship demonstrated provides a deeper understanding of the mechanical properties of the Li-electrolyte interface, which will play an important role in the design of batteries employing metallic Li anodes.

  3. The mechanism of electroforming of metal oxide memristive switches

    Science.gov (United States)

    Joshua Yang, J.; Miao, Feng; Pickett, Matthew D.; Ohlberg, Douglas A. A.; Stewart, Duncan R.; Lau, Chun Ning; Williams, R. Stanley

    2009-05-01

    Metal and semiconductor oxides are ubiquitous electronic materials. Normally insulating, oxides can change behavior under high electric fields—through 'electroforming' or 'breakdown'—critically affecting CMOS (complementary metal-oxide-semiconductor) logic, DRAM (dynamic random access memory) and flash memory, and tunnel barrier oxides. An initial irreversible electroforming process has been invariably required for obtaining metal oxide resistance switches, which may open urgently needed new avenues for advanced computer memory and logic circuits including ultra-dense non-volatile random access memory (NVRAM) and adaptive neuromorphic logic circuits. This electrical switching arises from the coupled motion of electrons and ions within the oxide material, as one of the first recognized examples of a memristor (memory-resistor) device, the fourth fundamental passive circuit element originally predicted in 1971 by Chua. A lack of device repeatability has limited technological implementation of oxide switches, however. Here we explain the nature of the oxide electroforming as an electro-reduction and vacancy creation process caused by high electric fields and enhanced by electrical Joule heating with direct experimental evidence. Oxygen vacancies are created and drift towards the cathode, forming localized conducting channels in the oxide. Simultaneously, O2- ions drift towards the anode where they evolve O2 gas, causing physical deformation of the junction. The problematic gas eruption and physical deformation are mitigated by shrinking to the nanoscale and controlling the electroforming voltage polarity. Better yet, electroforming problems can be largely eliminated by engineering the device structure to remove 'bulk' oxide effects in favor of interface-controlled electronic switching.

  4. Perovskite oxide heteroepitaxy; strain and interface engineering

    NARCIS (Netherlands)

    Boschker, J.A.

    2011-01-01

    Perovskite oxides are naturally suitable for heteroepitaxy. The new functionality of the heterostructures can be attributed to two fundamental effects in heteroepitaxy. At first the crystal structure of the layers is changed, due to the matching of the in-plane lattice constants to those of the

  5. Oxide interfaces with enhanced ion conductivity

    NARCIS (Netherlands)

    Leon, C.; Santamaria, J.; Boukamp, Bernard A.

    2013-01-01

    The new field of nano-ionics is expected to yield large improvements in the performance of oxide-based energy generation and storage devices based on exploiting size effects in ion conducting materials. The search for novel materials with enhanced ionic conductivity for application in energy devices

  6. Oxidation behaviour of metallic glass foams

    Energy Technology Data Exchange (ETDEWEB)

    Barnard, B.R. [Department of Materials Science and Engineering, 434 Dougherty Hall, University of Tennessee, Knoxville, TN 37996-2200 (United States)], E-mail: bbarnard@utk.edu; Liaw, P.K. [Department of Materials Science and Engineering, 434 Dougherty Hall, University of Tennessee, Knoxville, TN 37996-2200 (United States); Demetriou, M.D.; Johnson, W.L. [Department of Materials Science, Keck Laboratory, California Institute of Technology, Pasadena, CA 91125 (United States)

    2008-08-15

    In this study, the effects of porosity on the oxidation behaviour of bulk-metallic glasses were investigated. Porous Pd- and Fe-based bulk-metallic glass (BMG) foams and Metglas ribbons were studied. Oxidizing experiments were conducted at 70 deg. C, and around 80 deg. C below glass-transition temperatures, (T{sub g}s). Scanning-electron microscopy/energy-dispersive spectroscopy (SEM/EDS) studies revealed little evidence of oxidation at 70 deg. C. Specimens exhibited greater oxidation at T{sub g} - 80 deg. C. Oxides were copper-based for Pd-based foams, Fe-, Cr-, and Mo-based for Fe-based foams, and Co-based with borosilicates likely for the Metglas. Pd-based foams demonstrated the best oxidation resistance, followed by Metglas ribbons, followed by Fe-based foams.

  7. Refraction-reflection of electrons at lateral metallic interfaces

    Science.gov (United States)

    Kher-Elden, M. A.; El-Fattah, Z. M. Abd; Yassin, O.; El-Okr, M. M.

    2017-11-01

    Electron boundary element method (EBEM) has been employed to simulate electron refraction at the lateral interface between two homogenous metals featuring surface states characterized by isotropic constant energy surfaces. A decent agreement was achieved between the real-space EBEM simulations and the wave-space analysis obtained from electron plane wave expansion (EPWE) method. Calculations were performed for three different electron energies, being -0.05, -0.15, and -0.25 eV, where the reference energy is set to -0.4 eV, i.e., the band minimum of the Cu(111) surface state. For an interface separating two metals with the same effective mass (0.41 me) and a potential difference of 0.2 eV, we demonstrate that electrons with the first two energies exhibit refraction at the interface, following the Snell's law, and total internal reflections occur beyond energy-dependent critical angles, whereas for the third electron energy, a total internal reflection occurs at all incident angles. These findings were used to simulate optical elements such as convex lenses and possible guiding through perfect electron mirrors, in contrast to Bragg-based guiding. Given the varieties of possible means of manipulating the dispersion parameters via surface adsorbates and thin-film growth, the degree of electron refraction-reflection at metallic interfaces could be precisely tuned.

  8. High-energy photoemission studies of oxide interfaces

    Science.gov (United States)

    Claessen, Ralph

    2015-03-01

    The interfaces of complex oxide heterostructures can host novel quantum phases not existing in the bulk of the constituents, with the high-mobility 2D electron system (2DES) in LaAlO3/SrTiO3 (LAO/STO) representing a prominent example. Despite extensive research the origin of the 2DES and its unusual properties - including the supposed coexistence of superconductivity and ferromagnetism - are still a matter of intense debate. Photoelectron spectroscopy, recently extended into the soft (SX-ARPES) and hard (HAXPES) X-ray regime, is a powerful method to provide detailed insight into the electronic structure of these heterostructures and, in particular, of the buried interface. This includes the identification of the orbital character of the 2DES as well as the determination of vital band structure information, such as band alignment, band bending, and even k-resolved band dispersions and Fermi surface topology. Moreover, resonant photoemission at the Ti L-edge reveals the existence of two different species of Ti 3d states, localized and itinerant, which can be distinguished and identified by their different resonance behavior. The role of oxygen vacancies is studied by controlled in-situ oxidation, which allows us to vary the composition from fully stoichiometric to strongly O-deficient. By comparison to free STO surfaces we can thus demonstrate that the metallicity of the heteointerfaces is intrinsic, i . e . it persists even in the absence of O defects. I will discuss our photoemission results on LAO/STO heterostructures in both (100) and (111) orientation as well as on the related system γ-Al2O3/STO(100), which also hosts a 2DES with an even higher mobility. Work in collaboration with J. Mannhart (MPI-FKF, Stuttgart), N. Pryds (TU Denmark), G. Rijnders (U Twente), S. Suga (U Osaka), M. Giorgoi (BESSY, HZB), W. Drube (DESY Photon Science), V.N. Strocov (Swiss Light Source), J. Denlinger (Advanced Light Source, LBNL), and T.-L. Lee (Diamond Light Source). Support by

  9. Metal Oxides as Efficient Charge Transporters in Perovskite Solar Cells

    KAUST Repository

    Haque, Mohammed

    2017-07-10

    Over the past few years, hybrid halide perovskites have emerged as a highly promising class of materials for photovoltaic technology, and the power conversion efficiency of perovskite solar cells (PSCs) has accelerated at an unprecedented pace, reaching a record value of over 22%. In the context of PSC research, wide-bandgap semiconducting metal oxides have been extensively studied because of their exceptional performance for injection and extraction of photo-generated carriers. In this comprehensive review, we focus on the synthesis and applications of metal oxides as electron and hole transporters in efficient PSCs with both mesoporous and planar architectures. Metal oxides and their doped variants with proper energy band alignment with halide perovskites, in the form of nanostructured layers and compact thin films, can not only assist with charge transport but also improve the stability of PSCs under ambient conditions. Strategies for the implementation of metal oxides with tailored compositions and structures, and for the engineering of their interfaces with perovskites will be critical for the future development and commercialization of PSCs.

  10. Oxide-Graphene Interfaces for Graphene Spintronics

    Science.gov (United States)

    Stuart, Sean Clayton

    Graphene's high carrier mobility and low spin-orbit scattering allow for efficient spin transport, which has been demonstrated by several publications over useful length scales. Spintronic devices require an oxide tunneling barrier to allow for efficient spin injection from a magnetic contact and can employ magnetic oxide gates for spin manipulation. This thesis concerns the production and characterization of oxide films for graphene based spintronics. Pulsed laser deposition (PLD) was used to grow thin, uniform MgO films on graphene of suitable quality for tunneling barriers. This was an important result, improving on previous deposition techniques significantly. Progress toward more sophisticated spintronic devices requires controllable manipulation of spin polarized charge carriers. We have identified Cr 2O3 as a material whose magnetoelectric properties would enable voltage controlled switching of the exchange interaction. Magnetoelectric Cr2O3 filmswere produced by PLD. These films were characterized by x-ray diffraction, photoelectron spectroscopy and atomic force microscopy (AFM). The magnetoelectric properties of Cr2O 3 were characterized by a novel combination of electrostatic (EFM) and magnetic force microscopy (MFM). Magnetoelectric annealing was used to produce varying sized magnetoelectric domains imaged by MFM. A local electric field was applied with a conducting AFM tip, and the local switching of the polarization and magnetization produced by the applied field was measured.

  11. Organic/metal interfaces. Electronic and structural properties

    Energy Technology Data Exchange (ETDEWEB)

    Duhm, Steffen

    2008-07-17

    This work addresses several important topics of the field of organic electronics. The focus lies on organic/metal interfaces, which exist in all organic electronic devices. Physical properties of such interfaces are crucial for device performance. Four main topics have been covered: (i) the impact of molecular orientation on the energy levels, (ii) energy level tuning with strong electron acceptors, (iii) the role of thermodynamic equilibrium at organic/ organic homo-interfaces and (iv) the correlation of interfacial electronic structure and bonding distance. To address these issues a broad experimental approach was necessary: mainly ultraviolet photoelectron spectroscopy was used, supported by X-ray photoelectron spectroscopy, metastable atom electron spectroscopy, X-ray diffraction and X-ray standing waves, to examine vacuum sublimed thin films of conjugated organic molecules (COMs) in ultrahigh vacuum. (i) A novel approach is presented to explain the phenomenon that the ionization energy in molecular assemblies is orientation dependent. It is demonstrated that this is due to a macroscopic impact of intramolecular dipoles on the ionization energy in molecular assemblies. Furthermore, the correlation of molecular orientation and conformation has been studied in detail for COMs on various substrates. (ii) A new approach was developed to tune hole injection barriers ({delta}{sub h}) at organic/metal interfaces by adsorbing a (sub-) monolayer of an organic electron acceptor on the metal electrode. Charge transfer from the metal to the acceptor leads to a chemisorbed layer, which reduces {delta}{sub h} to the COM overlayer. This concept was tested with three acceptors and a lowering of {delta}{sub h} of up to 1.2 eV could be observed. (iii) A transition from vacuum-level alignment to molecular level pinning at the homo-interface between a lying monolayer and standing multilayers of a COM was observed, which depended on the amount of a pre-deposited acceptor. The

  12. PLUTONIUM METAL: OXIDATION CONSIDERATIONS AND APPROACH

    Energy Technology Data Exchange (ETDEWEB)

    Estochen, E.

    2013-03-20

    Plutonium is arguably the most unique of all metals when considered in the combined context of metallurgical, chemical, and nuclear behavior. Much of the research in understanding behavior and characteristics of plutonium materials has its genesis in work associated with nuclear weapons systems. However, with the advent of applications in fuel materials, the focus in plutonium science has been more towards nuclear fuel applications, as well as long term storage and disposition. The focus of discussion included herein is related to preparing plutonium materials to meet goals consistent with non-proliferation. More specifically, the emphasis is on the treatment of legacy plutonium, in primarily metallic form, and safe handling, packaging, and transport to meet non-proliferation goals of safe/secure storage. Elevated temperature oxidation of plutonium metal is the treatment of choice, due to extensive experiential data related to the method, as the oxide form of plutonium is one of only a few compounds that is relatively simple to produce, and stable over a large temperature range. Despite the simplicity of the steps required to oxidize plutonium metal, it is important to understand the behavior of plutonium to ensure that oxidation is conducted in a safe and effective manner. It is important to understand the effect of changes in environmental variables on the oxidation characteristics of plutonium. The primary purpose of this report is to present a brief summary of information related to plutonium metal attributes, behavior, methods for conversion to oxide, and the ancillary considerations related to processing and facility safety. The information provided is based on data available in the public domain and from experience in oxidation of such materials at various facilities in the United States. The report is provided as a general reference for implementation of a simple and safe plutonium metal oxidation technique.

  13. Method of making spherical metallic oxide and metallic carbide particles

    International Nuclear Information System (INIS)

    Zimmer, E.

    1976-01-01

    A method is described for making spherical metallic oxide and metallic carbide particles, especially particles consisting of fuel or breeder material such as oxide or carbide compounds of uranium, plutonium, thorium and the like with a diameter of from 0.1 to 1.5 millimeters, according to which an aqueous solution of a metallic nitrate or a metallic chloride or a mixture of metallic nitrates or metallic chlorides in which the metallic ions and anions are in a stoichiometric ratio to each other, is added dropwise to an organic phase. The method is characterized primarily in that the drops formed from the aqueous solution after congealing are washed in an aqueous solution containing ammonia and from 0.001 percent to 0.1 percent of a non-ionic surface active agent, especially an ethylene oxide condensate, enveloping the particles and preventing them from clumping during the following drying step. The hardened particles are dried in an air current having a temperature of from 150 to 300 0 C and an atmospheric moisture content corresponding to the degree of saturation of the air at a temperature of about from 20 to 50 0 C, and sintered at about 1300 0 C

  14. Conductance of perovskite oxide thin films and interfaces

    NARCIS (Netherlands)

    Mubeen Dildar, Ishrat

    2013-01-01

    This thesis deals with the properties of doped perovskite manganites in the form of thin films, and with interfaces between insulating perovskites. The first question we investigate has to do with the strong reduction of the metal-insulator (MI) transition temperature when the films are strained.In

  15. The Role of the Interface in Refractory Metal Alloy Composites

    Science.gov (United States)

    Grobstein, Toni; Yun, Hee M.

    1991-01-01

    Creep-rupture and tensile tests have been used to evaluate thoriated W-wire reinforced Nb-1 percent Zr alloy matrix composites fabricated via arc-spray monotape technique. A significant creep strength enhancement was observed over the unreinforced matrix alloy while matrix integrity was maintained; the fiber/matrix interface phase is noted to be a strong and ductile W/Nb alloy, which is formed due to the mutual solubility of the constituent metals. High strength, toughness, and thermal stability are demonstrated by this material system, which is also resistant to liquid alkali metal corrosion.

  16. Interface strength and degradation of adhesively bonded porous aluminum oxides

    DEFF Research Database (Denmark)

    T. Abrahami, Shoshan; M. M. de Kok, John; Gudla, Visweswara Chakravarthy

    2017-01-01

    environmental and health regulations. Replacing this traditional process in a high-demandingand high-risk industry such as aircraft construction requires an in-depth understanding of the underlying adhesion and degradationmechanisms at the oxide/resin interface resulting from alternative processes...

  17. Science at the interface : grain boundaries in nanocrystalline metals.

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez, Mark Andrew; Follstaedt, David Martin; Knapp, James Arthur; Brewer, Luke N.; Holm, Elizabeth Ann; Foiles, Stephen Martin; Hattar, Khalid M.; Clark, Blythe B.; Olmsted, David L.; Medlin, Douglas L.

    2009-09-01

    Interfaces are a critical determinant of the full range of materials properties, especially at the nanoscale. Computational and experimental methods developed a comprehensive understanding of nanograin evolution based on a fundamental understanding of internal interfaces in nanocrystalline nickel. It has recently been shown that nanocrystals with a bi-modal grain-size distribution possess a unique combination of high-strength, ductility and wear-resistance. We performed a combined experimental and theoretical investigation of the structure and motion of internal interfaces in nanograined metal and the resulting grain evolution. The properties of grain boundaries are computed for an unprecedented range of boundaries. The presence of roughening transitions in grain boundaries is explored and related to dramatic changes in boundary mobility. Experimental observations show that abnormal grain growth in nanograined materials is unlike conventional scale material in both the level of defects and the formation of unfavored phases. Molecular dynamics simulations address the origins of some of these phenomena.

  18. Temperature dependence of contact resistance at metal/MWNT interface

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Sang-Eui; Moon, Kyoung-Seok; Sohn, Yoonchul, E-mail: yoonchul.son@samsung.com [Materials Research Center, Samsung Advanced Institute of Technology, Samsung Electronics, Suwon 443-803 (Korea, Republic of)

    2016-07-11

    Although contact resistance of carbon nanotube (CNT) is one of the most important factors for practical application of electronic devices, a study regarding temperature dependence on contact resistance of CNTs with metal electrodes has not been found. Here, we report an investigation of contact resistance at multiwalled nanotube (MWNT)/Ag interface as a function of temperature, using MWNT/polydimethylsiloxane (PDMS) composite. Electrical resistance of MWNT/PDMS composite revealed negative temperature coefficient (NTC). Excluding the contact resistance with Ag electrode, the NTC effect became less pronounced, showing lower intrinsic resistivity with the activation energy of 0.019 eV. Activation energy of the contact resistance of MWNT/Ag interface was determined to be 0.04 eV, two times larger than that of MWNT-MWNT network. The increase in the thermal fluctuation assisted electron tunneling is attributed to conductivity enhancement at both MWNT/MWNT and MWNT/Ag interfaces with increasing temperature.

  19. Schottky barriers at metal-finite semiconducting carbon nanotube interfaces

    OpenAIRE

    Xue, Yongqiang; Ratner, Mark A.

    2003-01-01

    Electronic properties of metal-finite semiconducting carbon nanotube interfaces are studied as a function of the nanotube length using a self-consistent tight-binding theory. We find that the shape of the potential barrier depends on the long-range tail of the charge transfer, leading to an injection barrier thickness comparable to half of the nanotube length until the nanotube reaches the bulk limit. The conductance of the nanotube junction shows a transition from tunneling to thermally-acti...

  20. Nanopowder Metal Oxide for Photoluminescent Gas Sensing

    Science.gov (United States)

    Zhyrovetsky, V. M.; Popovych, D. I.; Savka, S. S.; Serednytski, A. S.

    2017-02-01

    Gas sensing properties of metal oxide nanopowders (ZnO, TiO2, WO3, SnO2) with average diameters of 40-60 nm were analyzed by room-temperature photoluminescence spectroscopy. The influence of gas environment (O2, N2, H2, CO, CO2) on the emission intensity was investigated for metal oxide nanopowders with surface doped by impurities (Pt, Ag, Au, Sn, Ni or Cu). Established physicochemical regularities of modification of surface electronic states of initial and doped nanopowders during gas adsorption. The nature of metal oxide nanopowder gas-sensing properties (adsorption capacity, sensitivity, selectivity) has been established and the design and optimal materials for the construction of the multi-component sensing matrix have been selected.

  1. Nanopowder Metal Oxide for Photoluminescent Gas Sensing

    Directory of Open Access Journals (Sweden)

    V. M. Zhyrovetsky

    2017-02-01

    Full Text Available Abstract Gas sensing properties of metal oxide nanopowders (ZnO, TiO2, WO3, SnO2 with average diameters of 40–60 nm were analyzed by room-temperature photoluminescence spectroscopy. The influence of gas environment (O2, N2, H2, CO, CO2 on the emission intensity was investigated for metal oxide nanopowders with surface doped by impurities (Pt, Ag, Au, Sn, Ni or Cu. Established physicochemical regularities of modification of surface electronic states of initial and doped nanopowders during gas adsorption. The nature of metal oxide nanopowder gas-sensing properties (adsorption capacity, sensitivity, selectivity has been established and the design and optimal materials for the construction of the multi-component sensing matrix have been selected.

  2. The Interfacial Thermal Conductance of Epitaxial Metal-Semiconductor Interfaces

    Science.gov (United States)

    Ye, Ning

    Understanding heat transport at nanometer and sub-nanometer lengthscales is critical to solving a wide range of technological challenges related to thermal management and energy conversion. In particular, finite Interfacial Thermal Conductance (ITC) often dominates transport whenever multiple interfaces are closely spaced together or when heat originates from sources that are highly confined by interfaces. Examples of the former include superlattices, thin films, quantum cascade lasers, and high density nanocomposites. Examples of the latter include FinFET transistors, phase-change memory, and the plasmonic transducer of a heat-assisted magnetic recording head. An understanding of the physics of such interfaces is still lacking, in part because experimental investigations to-date have not bothered to carefully control the structure of interfaces studied, and also because the most advanced theories have not been compared to the most robust experimental data. This thesis aims to resolve this by investigating ITC between a range of clean and structurally well-characterized metal-semiconductor interfaces using the Time-Domain Thermoreflectance (TDTR) experimental technique, and by providing theoretical/computational comparisons to the experimental data where possible. By studying the interfaces between a variety of materials systems, each with unique aspects to their tunability, I have been able to answer a number of outstanding questions regarding the importance of interfacial quality (epitaxial/non-epitaxial interfaces), semiconductor doping, matching of acoustic and optical phonon band structure, and the role of phonon transport mechanisms apart from direct elastic transmission on ITC. In particular, we are able to comment on the suitability of the diffuse mismatch model (DMM) to describe the transport across epitaxial interfaces. To accomplish this goal, I studied interfacial thermal transport across CoSi2, TiSi2, NiSi and PtSi - Si(100) and Si(111), (silicides

  3. Electronic doping of transition metal oxide perovskites

    Energy Technology Data Exchange (ETDEWEB)

    Cammarata, Antonio, E-mail: cammaant@fel.cvut.cz [Department of Control Engineering, Czech Technical University in Prague, Technicka 2, 16627 Prague 6 (Czech Republic); Rondinelli, James M. [Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208 (United States)

    2016-05-23

    CaFeO{sub 3} is a prototypical negative charge transfer oxide that undergoes electronic metal-insulator transition concomitant with a dilation and contraction of nearly rigid octahedra. Altering the charge neutrality of the bulk system destroys the electronic transition, while the structure is significantly modified at high charge content. Using density functional theory simulations, we predict an alternative avenue to modulate the structure and the electronic transition in CaFeO{sub 3}. Charge distribution can be modulated using strain-rotation coupling and thin film engineering strategies, proposing themselves as a promising avenue for fine tuning electronic features in transition metal-oxide perovskites.

  4. Recent Advances in Antimicrobial Hydrogels Containing Metal Ions and Metals/Metal Oxide Nanoparticles

    Directory of Open Access Journals (Sweden)

    Fazli Wahid

    2017-11-01

    Full Text Available Recently, the rapid emergence of antibiotic-resistant pathogens has caused a serious health problem. Scientists respond to the threat by developing new antimicrobial materials to prevent or control infections caused by these pathogens. Polymer-based nanocomposite hydrogels are versatile materials as an alternative to conventional antimicrobial agents. Cross-linking of polymeric materials by metal ions or the combination of polymeric hydrogels with nanoparticles (metals and metal oxide is a simple and effective approach for obtaining a multicomponent system with diverse functionalities. Several metals and metal oxides such as silver (Ag, gold (Au, zinc oxide (ZnO, copper oxide (CuO, titanium dioxide (TiO2 and magnesium oxide (MgO have been loaded into hydrogels for antimicrobial applications. The incorporation of metals and metal oxide nanoparticles into hydrogels not only enhances the antimicrobial activity of hydrogels, but also improve their mechanical characteristics. Herein, we summarize recent advances in hydrogels containing metal ions, metals and metal oxide nanoparticles with potential antimicrobial properties.

  5. Metal oxide/polyaniline nanocomposites

    Indian Academy of Sciences (India)

    Nanocomposites of iron oxide with conducting polymer in the form of powders of varying compositions have been studied to understand the effects of particle size, cluster size and magnetic inter-particle interactions. The sizes of the nanoparticles were estimated to be ∼ 10–20 nm from the X-ray diffraction (XRD) and the ...

  6. Metal oxide electrocatalysts for alternative energy technologies

    Science.gov (United States)

    Pacquette, Adele Lawren

    This dissertation focuses on the development of metal oxide electrocatalysts with varying applications for alternative energy technologies. Interest in utilizing clean, renewable and sustainable sources of energy for powering the planet in the future has received much attention. This will address the growing concern of the need to reduce our dependence on fossil fuels. The facile synthesis of metal oxides from earth abundant metals was explored in this work. The electrocatalysts can be incorporated into photoelectrochemical devices, fuel cells, and other energy storage devices. The first section addresses the utilization of semiconductors that can harness solar energy for water splitting to generate hydrogen. An oxysulfide was studied in order to combine the advantageous properties of the stability of metal oxides and the visible light absorbance of metal chalcogenides. Bi 2O2S was synthesized under facile hydrothermal conditions. The band gap of Bi2O2S was smaller than that of its oxide counterpart, Bi2O3. Light absorption by Bi 2O2S was extended to the visible region (>600 nm) in comparison to Bi2O3. The formation of a composite with In 2O3 was formed in order to create a UV irradiation protective coating of the Bi2O2S. The Bi2O2S/In 2O3 composite coupled with a dye CrTPP(Cl) and cocatalysts Pt and Co3O4 was utilized for water splitting under light irradiation to generate hydrogen and oxygen. The second section focuses on improving the stability and light absorption of semiconductors by changing the shapes and morphologies. One of the limitations of semiconductor materials is that recombination of electron-hole pairs occur within the bulk of the materials instead of migration to the surface. Three-dimensional shapes, such as nanorods, can prevent this recombination in comparison to spherical particles. Hierarchical structures, such as dendrites, cubes, and multipods, were synthesized under hydrothermal conditions, in order to reduce recombination and improve

  7. In situ observation of Ag-Cu-Ti liquid alloy/solid oxide interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Durov, O.V. [Frantsevich Institute for Problems of Materials Science of NASU, 3 Krzhyzhanovsky Street, Kiev 142, 03680 (Ukraine)], E-mail: avdu@ukr.net; Krasovskyy, V.P. [Frantsevich Institute for Problems of Materials Science of NASU, 3 Krzhyzhanovsky Street, Kiev 142, 03680 (Ukraine)

    2008-11-15

    In situ investigation methods are a very interesting means for understanding high-temperature interface processes. A method of direct observation of the interactions between transparent materials (Al{sub 2}O{sub 3}, SiO{sub 2}, CaF{sub 2}) and metal melts was elaborated. For the Ag-36.65 at.%Cu-8.15 at.%Ti/sapphire system, the formation of a dark compound at the interface was observed to occur at high temperature. This result does not confirm the conclusion of a neutron spectroscopy study which indicated that titanium oxides form at the interface only during solidification of the alloy. Interactions of the same alloy with SiO{sub 2} and CaF{sub 2} were also considered.

  8. Effect of grain alignment on interface trap density of thermally oxidized aligned-crystalline silicon films

    Science.gov (United States)

    Choi, Woong; Lee, Jung-Kun; Findikoglu, Alp T.

    2006-12-01

    The authors report studies of the effect of grain alignment on interface trap density of thermally oxidized aligned-crystalline silicon (ACSi) films by means of capacitance-voltage (C-V) measurements. C-V curves were measured on metal-oxide-semiconductor (MOS) capacitors fabricated on ⟨001⟩-oriented ACSi films on polycrystalline substrates. From high-frequency C-V curves, the authors calculated a decrease of interface trap density from 2×1012to1×1011cm-2eV-1 as the grain mosaic spread in ACSi films improved from 13.7° to 6.5°. These results demonstrate the effectiveness of grain alignment as a process technique to achieve significantly enhanced performance in small-grained (⩽1μm ) polycrystalline Si MOS-type devices.

  9. Dislocation and Structural Studies at Metal-Metallic Glass Interface at Low Temperature

    Science.gov (United States)

    Gupta, Pradeep; Yedla, Natraj

    2017-12-01

    In this paper, molecular dynamics (MD) simulation deformation studies on the Al (metal)-Cu50Zr50 (metallic glass) model interface is carried out based on cohesive zone model. The interface is subjected to mode-I loading at a strain rate of 109 s-1 and temperature of 100 K. The dislocations reactions and evolution of dislocation densities during the deformation have been investigated. Atomic interactions between Al, Cu and Zr atoms are modeled using EAM (embedded atom method) potential, and a timestep of 0.002 ps is used for performing the MD simulations. A circular crack and rectangular notch are introduced at the interface to investigate the effect on the deformation behavior and fracture. Further, scale size effect is also investigated. The structural changes and evolution of dislocation density are also examined. It is found that the dominant deformation mechanism is by Shockley partial dislocation nucleation. Amorphization is observed in the Al regions close to the interface and occurs at a lower strain in the presence of a crack. The total dislocation density is found to be maximum after the first yield in both the perfect and defect interface models and is highest in the case of perfect interface with a density of 6.31 × 1017 m-2. In the perfect and circular crack defect interface models, it is observed that the fraction of Shockley partial dislocation density decreases, whereas that of strain rod dislocations increases with increase in strain.

  10. Improved description of metal oxide stability

    DEFF Research Database (Denmark)

    Jauho, Thomas Stenbæk; Olsen, Thomas; Bligaard, Thomas

    2015-01-01

    transition-metal oxides. The mean absolute error relative to experiments is 0.21 eV and 0.38 eV per oxygen atom for rAPBE and RPA, respectively, and thus the rAPBE method greatly improves the description of metal-oxygen bonds across a wide range of oxides. The failure of the RPA can be partly attributed......The renormalized adiabatic PBE (rAPBE) method has recently been shown to comprise a significant improvement over the random phase approximation (RPA) for total energy calculations of simple solids and molecules. Here we consider the formation energies of 19 group I and II metal oxides and a few...... to the lack of error cancellation between the correlation energy of the oxide on the one hand and the bulk metal and oxygen molecule on the other hand, which are all separately predicted much too negative by the RPA. We ascribe the improved performance of the rAPBE to its significantly better description...

  11. Metal Oxide Vertical Graphene Hybrid Supercapacitors

    Science.gov (United States)

    Meyyappan, Meyya (Inventor)

    2018-01-01

    A metal oxide vertical graphene hybrid supercapacitor is provided. The supercapacitor includes a pair of collectors facing each other, and vertical graphene electrode material grown directly on each of the pair of collectors without catalyst or binders. A separator may separate the vertical graphene electrode materials.

  12. The Interface Between Chemical and Oxide Materials in the DSPEC

    Science.gov (United States)

    Meyer, Thomas; Alibabaei, Leila; Sherman, Benjamin; Sheridan, Matthew; Ashford, Dennis; Lapides, Alex; Brennaman, Kyle; Nayak, Animesh; Roy, Subhangi

    Significant challenges exist for both chemical and oxide materials in the Dye Sensitized Photoelectrosynthesis Cell (DSPEC) for water oxidation or CO2 reduction. They arise from light absorption, the energetics of electron or hole injection, the accumulation of multiple redox equivalents at catalysts for water oxidation or water/CO2 reduction in competition with back electron transfer, and sustained, long term performance. These challenges are being met by the use of a variety of chromophores (metal complexes, organic dyes, porphyrins), broad application of nanoparticle mesoscopic oxide films, atomic layer deposition (ALD) to prepare core/shell and stabilizing overlayer structures, and recent advances in the molecular catalysis of water oxidation and CO2 reduction. UNC EFRC Center for Solar Fuels, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number DE-SC0001011.

  13. SPECIATION OF HEAVY METALS AT WATER-SEDIMENT INTERFACE

    Directory of Open Access Journals (Sweden)

    Chiara Ferronato

    2013-09-01

    Full Text Available The objective of the study was to understand the equilibrium relationship between the heavy metals concentrations in superficial water and pore water. At  water-sediment interface, the equilibrium rapidly changed and it is influenced by chemico-physical parameters of aquatic ecosystems. The hydraulic safety of Bologna plain (North Italy depends on network of artificial canals and they are related with natural rivers of Reno basin (Reno river and its tributaries. The natural and artificial water courses flowed in agricultural, urban and industrial land. The heavy metals concentration in water and sediment discriminated the human pressure on the land and their spatial distribution in sediment could predict the hazard of pollution in aquatic ecosystems. We compared the heavy metals concentrations in pore water and superficial water determined in natural rivers and artificial canals, and more pollution in artificial canals than natural rivers was found. Furthermore, the coefficient of partition (log Kd between water and sediments was calculated to evaluate the bioavailability of heavy metals adsorbed on the sediments. The heavy metals extracted in deionised water at equilibrium after 16 h showed higher concentrations than those determined directly on water samples.

  14. Theory of the Spin Galvanic Effect at Oxide Interfaces

    Science.gov (United States)

    Seibold, Götz; Caprara, Sergio; Grilli, Marco; Raimondi, Roberto

    2017-12-01

    The spin galvanic effect (SGE) describes the conversion of a nonequilibrium spin polarization into a transverse charge current. Recent experiments have demonstrated a large conversion efficiency for the two-dimensional electron gas formed at the interface between two insulating oxides, LaAlO3 and SrTiO3 . Here, we analyze the SGE for oxide interfaces within a three-band model for the Ti t2 g orbitals which displays an interesting variety of effective spin-orbit couplings in the individual bands that contribute differently to the spin-charge conversion. Our analytical approach is supplemented by a numerical treatment where we also investigate the influence of disorder and temperature, which turns out to be crucial to providing an appropriate description of the experimental data.

  15. The Influence of Ceramic and Metallic Substrates on the Oxidation Behavior of Gold ABA

    Energy Technology Data Exchange (ETDEWEB)

    Weil, K. Scott; Rice, Joseph P.

    2004-12-31

    Two commercial ceramic-to-metal braze alloys, Nioro ABA and Gold ABA, were exposure tested in high-temperature air to evaluate their oxidation behavior, microstructural stability, and materials compatibility for potential application in sealing the ceramic and metal components of a solid-state oxygen separation device. Oxidation studies were conducted on the as-received braze alloy foils, on wetting samples prepared using yttria-stabilized zirconia (YSZ) and stainless steel substrates, and on brazed YSZ/stainless steel joints. It was found that the introduction of the YSZ and/or the stainless steel can significantly modify the inherent oxidation characteristics of these brazes due to accelerated oxygen transport along the braze/ceramic interface and/or diffusion of oxidizable species from the metal substrate into the braze during joining and subsequent segregation and oxidation of these species at the braze/ceramic interface.

  16. Emergent magnetism at transition-metal-nanocarbon interfaces.

    Science.gov (United States)

    Al Ma'Mari, Fatma; Rogers, Matthew; Alghamdi, Shoug; Moorsom, Timothy; Lee, Stephen; Prokscha, Thomas; Luetkens, Hubertus; Valvidares, Manuel; Teobaldi, Gilberto; Flokstra, Machiel; Stewart, Rhea; Gargiani, Pierluigi; Ali, Mannan; Burnell, Gavin; Hickey, B J; Cespedes, Oscar

    2017-05-30

    Charge transfer at metallo-molecular interfaces may be used to design multifunctional hybrids with an emergent magnetization that may offer an eco-friendly and tunable alternative to conventional magnets and devices. Here, we investigate the origin of the magnetism arising at these interfaces by using different techniques to probe 3d and 5d metal films such as Sc, Mn, Cu, and Pt in contact with fullerenes and rf-sputtered carbon layers. These systems exhibit small anisotropy and coercivity together with a high Curie point. Low-energy muon spin spectroscopy in Cu and Sc-C 60 multilayers show a quick spin depolarization and oscillations attributed to nonuniform local magnetic fields close to the metallo-carbon interface. The hybridization state of the carbon layers plays a crucial role, and we observe an increased magnetization as sp 3 orbitals are annealed into sp 2 -π graphitic states in sputtered carbon/copper multilayers. X-ray magnetic circular dichroism (XMCD) measurements at the carbon K edge of C 60 layers in contact with Sc films show spin polarization in the lowest unoccupied molecular orbital (LUMO) and higher π*-molecular levels, whereas the dichroism in the σ*-resonances is small or nonexistent. These results support the idea of an interaction mediated via charge transfer from the metal and dz -π hybridization. Thin-film carbon-based magnets may allow for the manipulation of spin ordering at metallic surfaces using electrooptical signals, with potential applications in computing, sensors, and other multifunctional magnetic devices.

  17. SPP propagation in nonlinear glass-metal interface

    KAUST Repository

    Sagor, Rakibul Hasan

    2011-12-01

    The non-linear propagation of Surface-Plasmon-Polaritons (SPP) in single interface of metal and chalcogenide glass (ChG) is considered. A time domain simulation algorithm is developed using the Finite Difference Time Domain (FDTD) method. The general polarization algorithm incorporated in the auxiliary differential equation (ADE) is used to model frequency-dependent dispersion relation and third-order nonlinearity of ChG. The main objective is to observe the nonlinear behavior of SPP propagation and study the dynamics of the whole structure. © 2011 IEEE.

  18. Charge Transfer and Catalysis at the Metal Support Interface

    Energy Technology Data Exchange (ETDEWEB)

    Baker, Lawrence Robert [Univ. of California, Berkeley, CA (United States)

    2012-07-31

    Kinetic, electronic, and spectroscopic characterization of model Pt–support systems are used to demonstrate the relationship between charge transfer and catalytic activity and selectivity. The results show that charge flow controls the activity and selectivity of supported metal catalysts. This dissertation builds on extensive existing knowledge of metal–support interactions in heterogeneous catalysis. The results show the prominent role of charge transfer at catalytic interfaces to determine catalytic activity and selectivity. Further, this research demonstrates the possibility of selectively driving catalytic chemistry by controlling charge flow and presents solid-state devices and doped supports as novel methods for obtaining electronic control over catalytic reaction kinetics.

  19. Charge transport in metal oxide nanocrystal-based materials

    OpenAIRE

    Runnerstrom, Evan Lars

    2016-01-01

    There is probably no class of materials more varied, more widely used, or more ubiquitous than metal oxides. Depending on their composition, metal oxides can exhibit almost any number of properties. Of particular interest are the ways in which charge is transported in metal oxides: devices such as displays, touch screens, and smart windows rely on the ability of certain metal oxides to conduct electricity while maintaining visible transparency. Smart windows, fuel cells, and other electrochem...

  20. Local Oxidation Nanolithography on Metallic Transition Metal Dichalcogenides Surfaces

    Directory of Open Access Journals (Sweden)

    Elena Pinilla-Cienfuegos

    2016-09-01

    Full Text Available The integration of atomically-thin layers of two dimensional (2D materials in nanodevices demands for precise techniques at the nanoscale permitting their local modification, structuration or resettlement. Here, we present the use of Local Oxidation Nanolithography (LON performed with an Atomic Force Microscope (AFM for the patterning of nanometric motifs on different metallic Transition Metal Dichalcogenides (TMDCs. We show the results of a systematic study of the parameters that affect the LON process as well as the use of two different modes of lithographic operation: dynamic and static. The application of this kind of lithography in different types of TMDCs demonstrates the versatility of the LON for the creation of accurate and reproducible nanopatterns in exfoliated 2D-crystals and reveals the influence of the chemical composition and crystalline structure of the systems on the morphology of the resultant oxide motifs.

  1. Metal and Metal Oxide Interactions and Their Catalytic Consequences for Oxygen Reduction Reaction

    Energy Technology Data Exchange (ETDEWEB)

    Jia, Qingying; Ghoshal, Shraboni; Li, Jingkun; Liang, Wentao; Meng, Guangnan [ULVAC Technologies, Inc., 401; Che, Haiying [Shanghai; Zhang, Shiming [Shanghai; Ma, Zi-Feng [Shanghai; Mukerjee, Sanjeev

    2017-06-01

    Many industrial catalysts are composed of metal particles supported on metal oxides (MMO). It is known that the catalytic activity of MMO materials is governed by metal and metal oxide interactions (MMOI), but how to optimize MMO systems via manipulation of MMOI remains unclear, due primarily to the ambiguous nature of MMOI. Herein, we develop a Pt/NbOx/C system with tunable structural and electronic properties via a modified arc plasma deposition method. We unravel the nature of MMOI by characterizing this system under reactive conditions utilizing combined electrochemical, microscopy, and in situ spectroscopy. We show that Pt interacts with the Nb in unsaturated NbOx owing to the oxygen deficiency in the MMO interface, whereas Pt interacts with the O in nearly saturated NbOx, and further interacts with Nb when the oxygen atoms penetrate into the Pt cluster at elevated potentials. While the Pt–Nb interactions do not benefit the inherent activity of Pt toward oxygen reduction reaction (ORR), the Pt–O interactions improve the ORR activity by shortening the Pt–Pt bond distance. Pt donates electrons to NbOx in both Pt–Nb and Pt–O cases. The resultant electron efficiency stabilizes low-coordinated Pt sites, hereby stabilizing small Pt particles. This determines the two characteristic features of MMO systems: dispersion of small metal particles and high catalytic durability. These findings contribute to our understandings of MMO catalytic systems.

  2. Preparation of oxide materials from metal alkoxides

    International Nuclear Information System (INIS)

    Turevskaya, E.P.; Turova, N.Ya.; Yanovskaya, M.I.

    2000-01-01

    The results of studies on the sol-gel technologies on the basis of alkoxides are presented. The synthesis and properties of titanates zirconates, niobates, tantalates, vanadates and solid solutions on the basis of Mo, W and Bi oxides, iron oxides and high-temperature superconductors are presented. The most important aspects, determining the choice of optimal conditions for preparation of oxides of concrete compositions with required properties are pointed out. Accomplishment of the whole chain of studies made it possible to synthesize a broad range of metal alkoxides and study their properties and also carry out large-scale studies on preparation of various oxides and materials on the basis thereof, using the source base of the sol-gel method [ru

  3. 40 CFR 721.5549 - Lithiated metal oxide.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Lithiated metal oxide. 721.5549... Substances § 721.5549 Lithiated metal oxide. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as lithiated metal oxide (LiNiO2) (PMN P-96-19...

  4. 40 CFR 721.4610 - Mixed metal oxides (generic).

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Mixed metal oxides (generic). 721.4610... Substances § 721.4610 Mixed metal oxides (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as mixed metal oxides (PMN P-98-0002...

  5. Polymorphism Control in Nanostructured Metal Oxides

    Science.gov (United States)

    Sood, Shantanu

    Polymorphic phase transformations are common to all nanocrystalline binary metal oxides. The polymorphic nature of such metal oxides makes available a large number of phases with differing crystal structures, each stable under certain conditions of temperature, pressure, and/or particle size. These different crystal structures translate to unique physical and chemical properties for each structural class of polymorphs. Thus predicting when polymorphic phase transitions are likely to occur becomes important to the synthesis of stable functional materials with desired properties. Theoretical calculations using a heuristic approach have resulted in an accurate estimation of the critical particle size predicting metastable to stable phase transitions. This formula is applied to different case studies: for anatase to rutile titania; gamma-Alumina to alpha-Alumina; and tetragonal to monoclinic zirconia. The theoretical values calculated have been seen to be very close to the experimental results from the literature. Manifestation of the effect of phase transitions in nanostructured metal oxides was provided in the study of metastable to stable phase transitions in WO3. Nanowires of tungsten trioxide have been synthesized in-situ inside an electron microscope. Such structure of tungsten trioxide result due to a metastable to stable phase transformation, from the cubic to the monoclinic phase. The transformation is massive and complete. The structures formed are unique one-dimensional nanowires. Such a method can be scaled inside any equipment equipped with an electron gun, for example lithography systems either using STEM or E-beam lithography. Another study on nanowire formation in binary metal oxides involved the synthesis of stable orthorhombic MoO3 by means of blend electrospinning. Both a traditional single jet electrospinning set up and a novel high-throughput process to get high aspect ratio nanowires. The latter is a jet-controlled and flow controlled

  6. Interface failure and adhesion measured by focused ion beam cutting of metal-polymer interfaces

    Science.gov (United States)

    Cordill, M. J.; Schmidegg, K.; Dehm, G.

    2011-08-01

    New developments in flexible electronics require metal films to adhere to polymer substrates. Measuring the interfacial adhesion of these systems is challenging, requiring the formulation of new techniques and models. A strategy to measure the adhesion of Cr-polyethylene terephthalate (PET) interfaces using tensile straining and buckle formation is presented in this article. Focused ion beam cross-sectioning of the buckles reveals that the polymer substrate can locally fail, which may lead to an overestimate of adhesion. Cr-PET adhesion energy of 9.4 ± 1.6 J/m2 is determined with the present approach.

  7. Ultrafast studies of electron dynamics at metal-dielectric interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Ge, Nien-Hui [Univ. of California, Berkeley, CA (United States)

    1998-10-01

    Femtosecond time- and angle-resolved two-photon photoemission spectroscopy has been used to study fundamental aspects of excited electron dynamics at metal-dielectric interfaces, including layer-by-layer evolution of electronic structure and two-dimensional electron localization. On bare Ag(111), the lifetimes of image states are dominated by their position with respect to the projected bulk band structure. The n = 2 state has a shorter lifetime than the n = 1 state due to degeneracy with the bulk conduction band. As the parallel momentum of the n = 1 image electron increases, the lifetime decreases. With decreasing temperatures, the n = 1 image electrons, with zero or nonzero parallel momentum, all become longer lived. Adsorption of one to three layers of n-heptane results in an approximately exponential increase in lifetime as a function of layer thickness. This results from the formation of a tunneling barrier through which the interfacial electrons must decay, consistent with the repulsive bulk electron affinity of n-alkanes. The lifetimes of the higher quantum states indicate that the presence of the monolayer significantly reduces coupling of the image states to the bulk band structure. These results are compared with predictions of a dielectric continuum model. The study of electron lateral motion shows that optical excitation creates interfacial electrons in quasifree states for motion parallel to the n-heptane/Ag(111) interface. These initially delocalized electrons decay into a localized state within a few hundred femtoseconds. The localized electrons then decay back to the metal by tunneling through the adlayer potential barrier. The localization time depends strongly on the electron's initial parallel momentum and exhibits a non-Arrhenius temperature dependence. The experimental findings are consistent with a 2-D self-trapping process in which electrons become localized by interacting with the topmost plane of the alkane layer. The energy

  8. Interfacing 2D Semiconductors with Functional Oxides: Fundamentals, Properties, and Applications

    Directory of Open Access Journals (Sweden)

    Zhiquan Yuan

    2017-08-01

    Full Text Available Two-dimensional semiconductors, such as transition-metal dichalcogenides (TMDs and black phosphorous (BP, have found various potential applications in electronic and opto-electronic devices. However, several problems including low carrier mobility and low photoluminescence efficiencies still limit the performance of these devices. Interfacing 2D semiconductors with functional oxides provides a way to address the problems by overcoming the intrinsic limitations of 2D semiconductors and offering them multiple functionalities with various mechanisms. In this review, we first focus on the physical effects of various types of functional oxides on 2D semiconductors, mostly on MoS2 and BP as they are the intensively studied 2D semiconductors. Insulating, semiconducting, conventional piezoelectric, strongly correlated, and magnetic oxides are discussed. Then we introduce the applications of these 2D semiconductors/functional oxides systems in field-effect devices, nonvolatile memory, and photosensing. Finally, we discuss the perspectives and challenges within this research field. Our review provides a comprehensive understanding of 2D semiconductors/functional oxide heterostructures, and could inspire novel ideas in interface engineering to improve the performance of 2D semiconductor devices.

  9. Physical chemistry of the interface between oxide and aqueous solution

    International Nuclear Information System (INIS)

    Jolivet, J.P.

    1997-01-01

    The behavior and properties of small oxide particles in aqueous suspension are dominated by the physico-chemistry of their surface. It is electrostatically charged and strongly solvated. The origin of the surface charge is discussed through the MUSIC model [Hiemstra 1996], allowing to estimate the acid-base behavior of surface oxygen atoms. The stability of aqueous dispersions of particles is analysed following the DLVO model, with a special attention on the hydration layers allowing the peptization of flocs. Different adsorption mechanisms of metal cations are presented in terms of coordination chemistry (outer- and inner-sphere complexes) emphasizing the coordinating ability of the surface towards metal complexes in solution. The anion adsorption is also studied in relation with some interesting consequences on spinel iron oxide nano-particles. (author)

  10. Magnetic Interactions in Transition-Metal Oxides

    OpenAIRE

    Solovyev, I. V.

    2003-01-01

    This a review article, which presents a general framework for the analysis of interatomic magnetic interactions in the spin-density-functional theory, which is based on the magnetic force theorem, make a link with the models for transition-metal oxides, and gives several examples of how this strategy can be used for the analysis of magnetic properties of colossal-magnetoresistive perovskite manganites, double perovskite and pyrochlore compounds.

  11. Metal-dielectric interfaces in gigascale electronics thermal and electrical stability

    CERN Document Server

    He, Ming

    2012-01-01

    Metal-dielectric interfaces are ubiquitous in modern electronics. As advanced gigascale electronic devices continue to shrink, the stability of these interfaces is becoming an increasingly important issue that has a profound impact on the operational reliability of these devices. In this book, the authors present the basic science underlying  the thermal and electrical stability of metal-dielectric interfaces and its relationship to the operation of advanced interconnect systems in gigascale electronics. Interface phenomena, including chemical reactions between metals and dielectrics, metallic-atom diffusion, and ion drift, are discussed based on fundamental physical and chemical principles. Schematic diagrams are provided throughout the book to illustrate  interface phenomena and the principles that govern them. Metal-Dielectric Interfaces in Gigascale Electronics  provides a unifying approach to the diverse and sometimes contradictory test results that are reported in the literature on metal-dielectric i...

  12. A dual enzyme functionalized nanostructured thulium oxide based interface for biomedical application.

    Science.gov (United States)

    Singh, Jay; Roychoudhury, Appan; Srivastava, Manish; Solanki, Pratima R; Lee, Dong Won; Lee, Seung Hee; Malhotra, B D

    2014-01-21

    In this paper, we present results of the studies related to fabrication of a rare earth metal oxide based efficient biosensor using an interface based on hydrothermally prepared nanostructured thulium oxide (n-Tm2O3). A colloidal solution of prepared nanorods has been electrophoretically deposited (EPD) onto an indium-tin-oxide (ITO) glass substrate. The n-Tm2O3 nanorods are found to provide improved sensing characteristics to the electrode interface in terms of electroactive surface area, diffusion coefficient, charge transfer rate constant and electron transfer kinetics. The structural and morphological studies of n-Tm2O3 nanorods have been carried out by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopic techniques. This interfacial platform has been used for fabrication of a total cholesterol biosensor by immobilizing cholesterol esterase (ChEt) and cholesterol oxidase (ChOx) onto a Tm2O3 nanostructured surface. The results of response studies of the fabricated ChEt-ChOx/n-Tm2O3/ITO bioelectrode show a broad linear range of 8-400 mg dL(-1), detection limit of 19.78 mg (dL cm(-2))(-1), and high sensitivity of 0.9245 μA (mg per dL cm(-2))(-1) with a response time of 40 s. Further, this bioelectrode has been utilized for estimation of total cholesterol with negligible interference (3%) from analytes present in human serum samples. The utilization of this n-Tm2O3 modified electrode for enzyme-based biosensor analysis offers an efficient strategy and a novel interface for application of the rare earth metal oxide materials in the field of electrochemical sensors and bioelectronic devices.

  13. Thermal oxidation of Zr–Cu–Al–Ni amorphous metal thin films

    Energy Technology Data Exchange (ETDEWEB)

    Oleksak, R.P.; Hostetler, E.B.; Flynn, B.T. [School of Chemical, Biological and Environmental Engineering, Oregon State University, Corvallis, OR 97331 (United States); McGlone, J.M.; Landau, N.P.; Wager, J.F. [School of Electrical Engineering and Computer Science, Oregon State University, Corvallis, OR 97331 (United States); Stickle, W.F. [Hewlett-Packard Company, Corvallis, OR 97333 (United States); Herman, G.S., E-mail: greg.herman@oregonstate.edu [School of Chemical, Biological and Environmental Engineering, Oregon State University, Corvallis, OR 97331 (United States)

    2015-11-30

    The initial stages of thermal oxidation for Zr–Cu–Al–Ni amorphous metal thin films were investigated using X-ray photoelectron spectroscopy, transmission electron microscopy and energy dispersive X-ray spectroscopy. The as-deposited films had oxygen incorporated during sputter deposition, which helped to stabilize the amorphous phase. After annealing in air at 300 °C for short times (5 min) this oxygen was found to segregate to the surface or buried interface. Annealing at 300 °C for longer times leads to significant composition variation in both vertical and lateral directions, and formation of a surface oxide layer that consists primarily of Zr and Al oxides. Surface oxide formation was initially limited by back-diffusion of Cu and Ni (< 30 min), and then by outward diffusion of Zr (> 30 min). The oxidation properties are largely consistent with previous observations of Zr–Cu–Al–Ni metallic glasses, however some discrepancies were observed which could be explained by the unique sample geometry of the amorphous metal thin films. - Highlights: • Thermal oxidation of amorphous Zr–Cu–Al–Ni thin films was investigated. • Significant short-range inhomogeneities were observed in the amorphous films. • An accumulation of Cu and Ni occurs at the oxide/metal interface. • Diffusion of Zr was found to limit oxide film growth.

  14. Catalysed electrolytic metal oxide dissolution processes

    International Nuclear Information System (INIS)

    Machuron-Mandard, X.

    1994-01-01

    The hydrometallurgical processes designed for recovering valuable metals from mineral ores as well as industrial wastes usually require preliminary dissolution of inorganic compounds in aqueous media before extraction and purification steps. Unfortunately, most of the minerals concerned hardly or slowly dissolve in acidic or basic solutions. Metallic oxides, sulfides and silicates are among the materials most difficult to dissolve in aqueous solutions. They are also among the main minerals containing valuable metals. The redox properties of such materials sometimes permit to improve their dissolution by adding oxidizing or reducing species to the leaching solution, which leads to an increase in the dissolution rate. Moreover, limited amounts of redox promoters are required if the redox agent is regenerated continuously thanks to an electrochemical device. Nuclear applications of such concepts have been suggested since the dissolution of many actinide compounds (e.g., UO 2 , AmO 2 , PuC, PuN,...) is mainly based on redox reactions. In the 1980s, improvements of the plutonium dioxide dissolution process have been proposed on the basis of oxidation-reduction principles, which led a few years later to the design of industrial facilities (e.g., at Marcoule or at the french reprocessing plant of La Hague). General concepts and well-established results obtained in France at the Atomic Energy Commission (''Commissariat a l'Energie Atomique'') will be presented and will illustrate applications to industrial as well as analytical problems. (author)

  15. An investigation of the oxidized Ni/InAs interface

    Energy Technology Data Exchange (ETDEWEB)

    Venter, A., E-mail: andre.venter@nmmu.ac.z [Department of Physics, Nelson Mandela Metropolitan University, PO Box 77000, Port Elizabeth 6031 (South Africa); Botha, J.R. [Department of Physics, Nelson Mandela Metropolitan University, PO Box 77000, Port Elizabeth 6031 (South Africa); Swart, H.C. [Department of Physics, University of the Free State, PO Box 339, Bloemfontein 9300 (South Africa); Naidoo, S.; Olivier, E.J. [Department of Physics, Nelson Mandela Metropolitan University, PO Box 77000, Port Elizabeth 6031 (South Africa)

    2009-12-01

    Ni was resistively deposited onto bulk InAs and subsequently oxidized in an O{sub 2} atmosphere. The anneal temperature and time were 450 deg. C and 2.5 h, respectively. X-ray diffraction of the oxidized Ni/InAs sample revealed the formation of In{sub 3}Ni{sub 2} and In{sub 2}O{sub 3} on the front suggesting inter diffusion of In, Ni and O. NiO was not detected by X-ray diffraction. In a preliminary study, using glass as a substrate, NiO readily formed when using these oxidation parameters. Conductivity measurements of the oxidized Ni/InAs surface revealed a conducting front and insulating rear surface while TEM of the Ni/InAs interface revealed an intermediate amorphous diffusion zone between the 'oxidized' Ni layer and the bulk InAs. A closer investigation of the intermediate layer supports the X-ray diffraction results, suggesting compound formation due to diffusion of oxygen and nickel into the substrate, and out-diffusion of In and As from the bulk of the sample. AES was used to further elucidate these results.

  16. Hydrous metal oxide catalysts for oxidation of hydrocarbons

    Energy Technology Data Exchange (ETDEWEB)

    Miller, J.E.; Dosch, R.G.; McLaughlin, L.I. [Sandia National Labs., Albuquerque, NM (United States). Process Research Dept.

    1993-07-01

    This report describes work performed at Sandia under a CRADA with Shell Development of Houston, Texas aimed at developing hydrous metal oxide (HMO) catalysts for oxidation of hydrocarbons. Autoxidation as well as selective oxidation of 1-octene was studied in the presence of HMO catalysts based on known oxidation catalysts. The desired reactions were the conversion of olefin to epoxides, alcohols, and ketones, HMOs seem to inhibit autoxidation reactions, perhaps by reacting with peroxides or radicals. Attempts to use HMOs and metal loaded HMOs as epoxidation catalysts were unsuccessful, although their utility for this reaction was not entirely ruled out. Likewise, alcohol formation from olefins in the presence of HMO catalysts was not achieved. However, this work led to the discovery that acidified HMOs can lead to carbocation reactions of hydrocarbons such as cracking. An HMO catalyst containing Rh and Cu that promotes the reaction of {alpha}-olefins with oxygen to form methyl ketones was identified. Although the activity of the catalyst is relatively low and isomerization reactions of the olefin simultaneously occur, results indicate that these problems may be addressed by eliminating mass transfer limitations. Other suggestions for improving the catalyst are also made. 57 refs.

  17. Metallic Interface Emerging at Magnetic Domain Wall of Antiferromagnetic Insulator: Fate of Extinct Weyl Electrons

    Directory of Open Access Journals (Sweden)

    Youhei Yamaji

    2014-05-01

    Full Text Available Topological insulators, in contrast to ordinary semiconductors, accompany protected metallic surfaces described by Dirac-type fermions. Here, we theoretically show that another emergent two-dimensional metal embedded in the bulk insulator is realized at a magnetic domain wall. The domain wall has long been studied as an ingredient of both old-fashioned and leading-edge spintronics. The domain wall here, as an interface of seemingly trivial antiferromagnetic insulators, emergently realizes a functional interface preserved by zero modes with robust two-dimensional Fermi surfaces, where pyrochlore iridium oxides proposed to host the condensed-matter realization of Weyl fermions offer such examples at low temperatures. The existence of in-gap states that are pinned at domain walls, theoretically resembling spin or charge solitons in polyacetylene, and protected as the edges of hidden one-dimensional weak Chern insulators characterized by a zero-dimensional class-A topological invariant, solves experimental puzzles observed in R_{2}Ir_{2}O_{7} with rare-earth elements R. The domain wall realizes a novel quantum confinement of electrons and embosses a net uniform magnetization that enables magnetic control of electronic interface transports beyond the semiconductor paradigm.

  18. Understanding oxide interfaces: From microscopic imaging to electronic phases

    Science.gov (United States)

    Ilani, Shahal

    2014-03-01

    In the last decade, the advent of complex oxide interfaces has unleashed a wealth of new possibilities to create materials with unexpected functionalities. A notable example is the two-dimensional electron system formed at the interface between LaAlO3 and SrTiO3 (LAO/STO), which exhibits ferromagnetism, superconductivity, and a wide range of unique magneto-transport properties. A key challenge is to find the microscopic mechanisms that underlie these emergent phenomena. While there is a growing understanding that these phenomena might reflect rich structures at the micro-scale, experimental progress toward microscopic imaging of this system has been so far rather limited due to the buried nature of its interface. In this talk I will discuss our experiments that study this system on microscopic and macroscopic scales. Using a newly-developed nanotube-based scanning electrometer we image on the nanoscale the electrostatics and mechanics of this buried interface. We reveal the dynamics of structural domains in STO, their role in generating the contested anomalous piezoelectricity of this substrate, and their direct effects on the physics of the interface electrons. Using macroscopic magneto-transport experiments we demonstrate that a universal Lifshitz transition between the population of d-orbitals with different symmetries underlies many of the transport phenomena observed to date. We further show that the interactions between the itinerant electrons and localized spins leads to an unusual, gate-tunable magnetic phase diagram. These measurements highlight the unique physical settings that can be realized within this new class of low dimensional systems.

  19. Interface between Sr2RuO4 and Ru-metal inclusion: Implications for its superconductivity

    Science.gov (United States)

    Ghosh, Soham S.; Xin, Yan; Mao, Zhiqiang; Manousakis, Efstratios

    2017-11-01

    Under various conditions of the growth process, when the presumably unconventional superconductor Sr2RuO4 (SRO) contains microinclusions of Ru metal, the superconducting critical temperature increases significantly. An atomic resolution high-angle annular-dark-field scanning transmission electron microscopy study shows a sharp interface geometry which allows crystals of SRO and of Ru metal to grow side by side by forming a commensurate superlattice structure at the interface. In an attempt to shed light on why this happens, we investigated the atomic structure and electronic properties of the interface between the oxide and the metal microinclusions using density functional theory calculations. Our results support the observed structure, indicating that it is energetically favored over other types of Ru-metal/SRO interfaces. We find that t2 g-eg orbital mixing occurs at the interface with significantly enhanced magnetic moments. Based on our findings, we argue that an inclusion-mediated interlayer coupling reduces phase fluctuations of the superconducting order parameter, which could explain the observed enhancement of the superconducting critical temperature in SRO samples containing microinclusions.

  20. Selective propene oxidation on mixed metal oxide catalysts

    International Nuclear Information System (INIS)

    James, David William

    2002-01-01

    Selective catalytic oxidation processes represent a large segment of the modern chemical industry and a major application of these is the selective partial oxidation of propene to produce acrolein. Mixed metal oxide catalysts are particularly effective in promoting this reaction, and the two primary candidates for the industrial process are based on iron antimonate and bismuth molybdate. Some debate exists in the literature regarding the operation of these materials and the roles of their catalytic components. In particular, iron antimonate catalysts containing excess antimony are known to be highly selective towards acrolein, and a variety of proposals for the enhanced selectivity of such materials have been given. The aim of this work was to provide a direct comparison between the behaviour of bismuth molybdate and iron antimonate catalysts, with additional emphasis being placed on the component single oxide phases of the latter. Studies were also extended to other antimonate-based catalysts, including cobalt antimonate and vanadium antimonate. Reactivity measurements were made using a continuous flow microreactor, which was used in conjunction with a variety of characterisation techniques to determine relationships between the catalytic behaviour and the properties of the materials. The ratio of Fe/Sb in the iron antimonate catalyst affects the reactivity of the system under steady state conditions, with additional iron beyond the stoichiometric value being detrimental to the acrolein selectivity, while extra antimony provides a means of enhancing the selectivity by decreasing acrolein combustion. Studies on the single antimony oxides of iron antimonate have shown a similarity between the reactivity of 'Sb 2 O 5 ' and FeSbO 4 , and a significant difference between these and the Sb 2 O 3 and Sb 2 O 4 phases, implying that the mixed oxide catalyst has a surface mainly comprised of Sb 5+ . The lack of reactivity of Sb 2 O 4 implies a similarity of the surface with

  1. Approach to Multifunctional Device Platform with Epitaxial Graphene on Transition Metal Oxide (Postprint)

    Science.gov (United States)

    2015-09-23

    layers, respectively. 15. SUBJECT TERMS Heterostructures, two-dimensional materials, van der Waals interaction , 2D graphene, metal oxide (TiO2...sample holder with a 10.6 μ m CO2 IR laser . The laser output power was adjusted until the target temperature was reached. The temperature of the sample... Laser Deposited Transition- Metal Carbides for Field-Emission Cathode Coatings. ACS Appl. Mater. Interfaces 5, 9241–9246 (2013). 13. Swift, G. A

  2. Noncollinear magnetism in surfaces and interfaces of transition metals

    Energy Technology Data Exchange (ETDEWEB)

    Tan, Huahai

    2009-09-15

    Noncollinear (NC) magnetism is common in nature, especially when there exist geometrical frustration and chemical imparity in the system. In this work we studied the NC magnetism and the response to external magnetic fields in surfaces and interfaces of transition metals by using an semi-empirical tight-binding (TB) method that parameterized to the ab initio TB-LMTO calculations. We implemented this method to study two systems. The first one is the system of 6 Mn monolayers on Fe(001) substrate. Due to the complex structure and magnetic properties of Mn, we found 23 collinear magnetic configurations but only one NC configuration. The collinear ground state has a layered antiferromagnetic (AFM) coupling which agrees with previous experiments and calculations. In the NC configuration the local AFM coupling in the Mn layers is preserved, but the surface is 90 degree coupled to the substrate. Similar to the experiment in CdCr{sub 2}O{sub 4}, we obtained a collinear plateau in the NC evolution of the average magnetic moment in Mn slab under external magnetic fields. Another is the system of a Cr monolayer on a stepped Fe(001) substrate. As expected, the local AFM coupling in the interface of Cr and Fe are preserved. However, the edge Cr atoms is about 90 coupled to their nearest Fe neighbors. We also simulated the procedure of adding more Cr coverages gradually to a Cr bilayer coverage. As coverages increase, the magnetic moments in the Cr interface reduce, and the collinear plateau becomes wider as coverages increase. However, the saturation fields in both the two systems are extremely high, around 10 kT.We expect that when the effect of temperature is taken into account, and in some proper systems, the saturation fields could be largely reduced to the scale that can be implemented in experiment, and our study may shed light on information storage devices with ultrahigh storage density. (orig.)

  3. Study of the interactions between alumina and metallic ion in solution at the liquid/oxide interface during catalysts synthesis; Etude des interactions alumine/ion metallique en solution a l`interface oxyde/liquide lors de la preparation des catalyseurs

    Energy Technology Data Exchange (ETDEWEB)

    Mertens de Wilmars, D.

    1998-01-15

    This work concerns the formation of compounds including metal and Al(III) ions during impregnation of gamma alumina with a solution of the metal precursor. Formation of Li/Al hydroxy-carbonate (Li/Al HDC) on alumina during impregnation by a neutral or basic solution containing Li{sup +} is established. Zeta potential measurements are used to determine the ratio overlay of the alumina by HDC Li/Al. By this technique, residual positive charges are observed on HDC Li/Al surface. The formation of two different compounds including Mo(VI) and Al(III) ions during impregnation of alumina with molybdate or hepta-molybdate solution is reported here for the first time. The use of sodium molybdate solution as impregnation precursor leads to the formation of hydroxy-molybdo-luminate, while the ammonium hepta-molybdate solution forms ammonium hexa-molybdo-aluminate by contact with alumina.Dissolution kinetics of alumina in aqueous solution in absence or in presence of metal ions (Li{sup +}, K{sup +}, Zn{sup 2+}, MoO{sub 4}{sup 2-}, Mo{sub 7}O{sub 24}{sup 6-}) are investigated at different pH. Results show that the support is not inert in aqueous solution, even at neutral pH (near ZPC). The homogeneous nucleation of Li/Al HDC observed for Li/Al{sub 2}O{sub 3} system evidence the permeability of the solid/solution interface: diffusion processus through the interface is more important than previously reported. A dissolution-precipitation mechanism is proposed to account for the formation of Al(III)-containing compounds on alumina surface. Alumina dissolves when contacted with aqueous solution. When Al(III) ions concentration in solution is bigger than the sur-saturation needed for heterogenous nucleation of the Al(III) containing compounds, this one precipitates. This mechanism agrees with all our results. (author) 169 refs.

  4. Zinc adsorption effects on arsenite oxidation kinetics at the birnessite-water interface

    Science.gov (United States)

    Power, L.E.; Arai, Y.; Sparks, D.L.

    2005-01-01

    Arsenite is more toxic and mobile than As(V) in soil and sediment environments, and thus it is advantageous to explore factors that enhance oxidation of As(III) to As(V). Previous studies showed that manganese oxides, such as birnessite (??-MnO2), directly oxidized As(III). However, these studies did not explore the role that cation adsorption has on As(III) oxidation. Accordingly, the effects of adsorbed and nonadsorbed Zn on arsenite (As(III)) oxidation kinetics at the birnessite-water interface were investigated using batch adsorption experiments (0.1 g L-1; pH 4.5 and 6.0; I = 0.01 M NaCl). Divalent Zn adsorption on synthetic ??-MnO 2 in the absence of As(III) increased with increasing pH and caused positive shifts in electrophoretic mobility values at pH 4-6, indirectly suggesting inner-sphere Zn adsorption mechanisms. Arsenite was readily oxidized on birnessite in the absence of Zn. The initial As(III) oxidation rate constant decreased with increasing pH from 4.5 to 6.0 and initial As(III) concentrations from 100 to 300 ??M. Similar pH and initial As(III) concentration effects were observed in systems when Zn was present (i.e., presorbed Zn prior to As(III) addition and simultaneously added Zn-As(III) systems), but As(III) oxidation reactions were suppressed compared to the respective control systems. The suppression was more pronounced when Zn was presorbed on the ??-MnO 2 surfaces as opposed to added simultaneously with As(III). This study provides further understanding of As(III) oxidation reactions on manganese oxide surfaces under environmentally applicable conditions where metals compete for reactive sites.

  5. The competing oxide and sub-oxide formation in metal-oxide molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Vogt, Patrick; Bierwagen, Oliver [Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5-7, D-10117 Berlin (Germany)

    2015-02-23

    The hetero-epitaxial growth of the n-type semiconducting oxides β-Ga{sub 2}O{sub 3}, In{sub 2}O{sub 3}, and SnO{sub 2} on c- and r-plane sapphire was performed by plasma-assisted molecular beam epitaxy. The growth-rate and desorbing flux from the substrate were measured in-situ under various oxygen to metal ratios by laser reflectometry and quadrupole mass spectrometry, respectively. These measurements clarified the role of volatile sub-oxide formation (Ga{sub 2}O, In{sub 2}O, and SnO) during growth, the sub-oxide stoichiometry, and the efficiency of oxide formation for the three oxides. As a result, the formation of the sub-oxides decreased the growth-rate under metal-rich growth conditions and resulted in etching of the oxide film by supplying only metal flux. The flux ratio for the exclusive formation of the sub-oxide (e.g., the p-type semiconductor SnO) was determined, and the efficiency of oxide formation was found to be the highest for SnO{sub 2}, somewhat lower for In{sub 2}O{sub 3}, and the lowest for Ga{sub 2}O{sub 3}. Our findings can be generalized to further oxides that possess related sub-oxides.

  6. Graphene-metal interaction and its effect on the interface stability under ambient conditions

    Energy Technology Data Exchange (ETDEWEB)

    Dong, Aiyi; Fu, Qiang, E-mail: qfu@dicp.ac.cn; Wei, Mingming; Bao, Xinhe

    2017-08-01

    Highlights: • Graphene (Gr)/transition metal (TM: Fe, Co, Pt, and Au) interfaces form through TM intercalation at Gr/Ru(0001) surface. • Graphene-metal interaction strength follows the order of Ru ≈ Fe ≈ Co > Pt > Au. • Oxygen intercalation occurs at Gr/Fe, Gr/Co, Gr/Pt, and Gr/Ru interfaces but not at Gr/Au interface in air around 100 °C. - Abstract: Interaction between graphene (Gr) and metal plays an important role in physics and chemistry of graphene/metal interfaces. In this work, well-defined interfaces between graphene and transition metals (TMs) including Fe, Co, Pt, and Au were prepared through TM intercalation on Gr/Ru(0001) surface. The Gr-metal interaction was investigated using X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy. We found that graphene interacts most strongly with Ru, Fe and Co and most weakly with Au, following the order of Ru ≈ Fe ≈ Co > Pt > Au. The Gr/Fe, Gr/Co, Gr/Pt, and Gr/Ru interfaces can be readily intercalated by oxygen when exposed to air and illuminated by an infrared lamp. In contrast, oxygen intercalation does not happen at the Gr/Au interface under the same condition. It is suggested that both Gr-metal interaction and oxygen adsorption on the underlying metal surface are critical in the oxygen intercalation and the Gr/metal interface stability.

  7. Electrochromic device containing metal oxide nanoparticles and ultraviolet blocking material

    Energy Technology Data Exchange (ETDEWEB)

    Garcia, Guillermo; Koo, Bonil; Gregoratto, Ivano; Basu, Sourav; Rosen, Evelyn; Holt, Jason; Thomsen, Scott

    2017-10-17

    An electrochromic device includes a nanostructured transition metal oxide bronze layer that includes one or more transition metal oxide and one or more dopant. The electrochromic device also includes nanoparticles containing one or more transparent conducting oxide (TCO), a solid state electrolyte, a counter electrode, and at least one protective layer to prevent degradation of the one or more nanostructured transition metal oxide bronze. The nanostructured transition metal oxide bronze selectively modulates transmittance of near-infrared (NIR) and visible radiation as a function of an applied voltage to the device.

  8. Self-assembled monolayers on metal oxides : applications in nanotechnology

    NARCIS (Netherlands)

    Yildirim, O.

    2010-01-01

    The thesis describes the use of phosph(on)ate-based self-assembled monolayers (SAMs) to modify and pattern metal oxides. Metal oxides have interesting electronic and magnetic properties such as insulating, semiconducting, metallic, ferromagnetic etc. and SAMs can tailor the surface properties. FePt

  9. Modular "click" chemistry for electrochemically and photoelectrochemically active molecular interfaces to tin oxide surfaces.

    Science.gov (United States)

    Benson, Michelle C; Ruther, Rose E; Gerken, James B; Rigsby, Matthew L; Bishop, Lee M; Tan, Yizheng; Stahl, Shannon S; Hamers, Robert J

    2011-08-01

    We demonstrate the use of "click" chemistry to form electrochemically and photoelectrochemically active molecular interfaces to SnO(2) nanoparticle thin films. By using photochemical grafting to link a short-chain alcohol to the surface followed by conversion to a surface azide group, we enable use of the Cu(I)-catalyzed azide-alkyne [3 + 2] cycloaddition (CuAAC) reaction, a form of "click" chemistry, on metal oxide surfaces. Results are shown with three model compounds to test the surface chemistry and subsequent ability to achieve electrochemical and photoelectrochemical charge transfer. Surface-tethered ferrocene groups exhibit good electron-transfer characteristics with thermal rates estimated at >1000 s(-1). Time-resolved surface photovoltage measurements using a ruthenium terpyridyl coordination compound demonstrate photoelectron charge transfer on time scales of nanoseconds or less, limited by the laser pulse width. The results demonstrate that the CuAAC "click" reaction can be used to form electrochemically and photoelectrochemically active molecular interfaces to SnO(2) and other metal oxide semiconductors.

  10. Tin etching from metallic and oxidized scandium thin films

    NARCIS (Netherlands)

    Pachecka, Malgorzata; Lee, Christopher James; Sturm, J.M.; Bijkerk, Frederik

    The role of oxide on Sn adhesion to Sc surfaces was studied with in-situ ellipsometry, X-ray photoelectron spectroscopy and secondary electron microscopy. Sn etching with hydrogen radicals was performed on metallic Sc, metallic Sc with a native oxide, and a fully oxidized Sc layer. The results show

  11. Growth and sacrificial oxidation of transition metal nanolayers

    NARCIS (Netherlands)

    T. Tsarfati,; Zoethout, E.; van de Kruijs, R.; F. Bijkerk,

    2009-01-01

    Growth and oxidation of Au, Pt, Pd, Rh, Cu, Ru, Ni and Co layers of 0.3-4.3 nm thickness on Mo have been investigated with ARPES and AFM. Co and Ni layers oxidize while the Mo remains metallic. For nobler metals, the on top O and oxidation state of subsurface Mo increase, suggesting sacrificial e(-)

  12. Growth and sacrificial oxidation of transition metal nanolayers

    NARCIS (Netherlands)

    Tsarfati, T.; Tsarfati, Tim; Zoethout, E.; Zoethout, E.; van de Kruijs, Robbert Wilhelmus Elisabeth; Bijkerk, Frederik

    2009-01-01

    Growth and oxidation of Au, Pt, Pd, Rh, Cu, Ru, Ni and Co layers of 0.3–4.3 nm thickness on Mo have been investigated with ARPES and AFM. Co and Ni layers oxidize while the Mo remains metallic. For nobler metals, the on top O and oxidation state of subsurface Mo increase, suggesting sacrificial e−

  13. Competitive sorption of Ni and Zn at the aluminum oxide/water interface: an XAFS study.

    Science.gov (United States)

    Gou, Wenxian; Siebecker, Matthew G; Wang, Zimeng; Li, Wei

    2018-03-27

    Trace metals (e.g. Ni, Zn) leached from industrial and agricultural processes are often simultaneously present in contaminated soils and sediments. Their mobility, bioavailability, and ecotoxicity are affected by sorption and cosorption at mineral/solution interfaces. Cosorption of trace metals has been investigated at the macroscopic level, but there is not a clear understanding of the molecular-scale cosorption processes due to lack of spectroscopic information. In this study, Ni and Zn cosorption to aluminum oxides (γ-Al 2 O 3 ) in binary-sorbate systems were compared to their sorption in single-sorbate systems as a function of pH using both macroscopic batch experiments and synchrotron-based X-ray absorption fine structure spectroscopy. At pH 6.0, Ni and Zn were sorbed as inner-sphere surface complexes and competed for the limited number of reactive sites on γ-Al 2 O 3 . In binary-sorbate systems, Ni had no effect on Zn sorption, owning to its lower affinity for the metal oxide surface. In contrast, Zn had a higher affinity for the metal oxide surface and reduced Ni sorption. At pH 7.5, Ni and Zn were sorbed as mixed-metal surface precipitates, including Ni-Al layered double hydroxides (LDHs), Zn-Al LDHs, and likely Ni-Zn-Al layered triple/ternary hydroxides. Additionally, at pH 7.5, Ni and Zn do not exhibit competitive sorption effects in the binary system. Taken together, these results indicated that pH critically influenced the reaction products, and provides a crucial scientific basis to understand the potential mobility, bioavailability, and ecotoxicity of Ni and Zn in natural and contaminated geochemical environments.

  14. Experimental demonstration of the universal energy level alignment rule at oxide/organic semiconductor interfaces

    Science.gov (United States)

    Chai, L.; White, R. T.; Greiner, M. T.; Lu, Z. H.

    2014-01-01

    In this work, our experimental demonstration of the universal energy level alignment rule at oxide/organic semiconductor interfaces is reported. Photoemission spectroscopy is used to show the three different regimes of the energy level alignment: the lowest unoccupied molecular orbital (LUMO) is pinned to the substrate Fermi level at the extreme low end of work functions; the energy offset of the highest occupied molecular orbital (HOMO) follows the Schottky-Mott rule; the HOMO is pinned to the substrate Fermi level at the extreme high end of work functions. To demonstrate this, fullerene C60 was deposited on eight different types of transition-metal oxides, ZrO2,TiO2, NiO, Co3O4, CuO, V2O5,MoO3, and WO3, followed by in situ ultraviolet photoemission spectroscopy.

  15. Direct Probing of the Dielectric Scavenging-Layer Interface in Oxide Filamentary-Based Valence Change Memory.

    Science.gov (United States)

    Celano, Umberto; Op de Beeck, Jonathan; Clima, Sergiu; Luebben, Michael; Koenraad, Paul M; Goux, Ludovic; Valov, Ilia; Vandervorst, Wilfried

    2017-03-29

    A great improvement in valence change memory performance has been recently achieved by adding another metallic layer to the simple metal-insulator-metal (MIM) structure. This metal layer is often referred to as oxygen exchange layer (OEL) and is introduced between one of the electrodes and the oxide. The OEL is believed to induce a distributed reservoir of defects at the metal-insulator interface thus providing an unlimited availability of building blocks for the conductive filament (CF). However, its role remains elusive and controversial owing to the difficulties to probe the interface between the OEL and the CF. Here, using Scalpel SPM we probe multiple functions of the OEL which have not yet been directly measured, for two popular VCMs material systems: Hf/HfO 2 and Ta/Ta 2 O 5 . We locate and characterize in three-dimensions the volume containing the oxygen exchange layer and the CF with nanometer lateral resolution. We demonstrate that the OEL induces a thermodynamic barrier for the CF and estimate the minimum thickness of the OEL/oxide interface to guarantee the proper switching operations is ca. 3 nm. Our experimental observations are combined to first-principles thermodynamics and defect kinetics to elucidate the role of the OEL for device optimization.

  16. Metallic oxide switches using thick film technology

    Science.gov (United States)

    Patel, D. N.; Williams, L., Jr.

    1974-01-01

    Metallic oxide thick film switches were processed on alumina substrates using thick film technology. Vanadium pentoxide in powder form was mixed with other oxides e.g., barium, strontium copper and glass frit, ground to a fine powder. Pastes and screen printable inks were made using commercial conductive vehicles and appropriate thinners. Some switching devices were processed by conventional screen printing and firing of the inks and commercial cermet conductor terminals on 96% alumina substrates while others were made by applying small beads or dots of the pastes between platinum wires. Static, and dynamic volt-ampere, and pulse tests indicate that the switching and self-oscillatory characteristics of these devices could make them useful in memory element, oscillator, and automatic control applications.

  17. Metal oxide membranes for gas separation

    Science.gov (United States)

    Anderson, Marc A.; Webster, Elizabeth T.; Xu, Qunyin

    1994-01-01

    A method for permformation of a microporous ceramic membrane onto a porous support includes placing a colloidal suspension of metal oxide particles on one side of the porous support and exposing the other side of the porous support to a drying stream of gas or a reactive gas stream so that the particles are deposited on the drying side of the support as a gel. The gel so deposited can be sintered to form a supported ceramic membrane having mean pore sizes less than 30 Angstroms and useful for ultrafiltration, reverse osmosis, or gas separation.

  18. Magnetic correlations in doped transition metal oxides

    International Nuclear Information System (INIS)

    The authors review recent reactor- and spallation-source-based neutron scattering experiments on the magnetic fluctuations and order in a variety of doped transition metal oxides. In particular, data are shown for the NiO chain compound, Y 2-x Ca x BaNiO 5 , the two-dimensional cuprate superconductors La 2-x Sr x CuO 4 and YBa 2 Cu 3 O 6+x , and the classical three-dimensional ''Mott-Hubbard'' system V 2-y O 3

  19. Impacts of oxidants in atomic layer deposition method on Al2O3/GaN interface properties

    Science.gov (United States)

    Taoka, Noriyuki; Kubo, Toshiharu; Yamada, Toshikazu; Egawa, Takashi; Shimizu, Mitsuaki

    2018-01-01

    The electrical interface properties of GaN metal-oxide-semiconductor (MOS) capacitors with an Al2O3 gate insulator formed by atomic layer deposition method using three kinds of oxidants were investigated by the capacitance-voltage technique, Terman method, and conductance method. We found that O3 and the alternate supply of H2O and O3 (AS-HO) are effective for reducing the interface trap density (D it) at the energy range of 0.15 to 0.30 eV taking from the conduction band minimum. On the other hand, we found that surface potential fluctuation (σs) induced by interface charges for the AS-HO oxidant is much larger than that for a Si MOS capacitor with a SiO2 layer formed by chemical vapor deposition despite the small D it values for the AS-HO oxidant compared with the Si MOS capacitor. This means that the total charged center density including the fixed charge density, charged slow trap density, and charged interface trap density for the GaN MOS capacitor is higher than that for the Si MOS capacitor. Therefore, σs has to be reduced to improve the performances and reliability of GaN devices with the Al2O3/GaN interfaces.

  20. Energy level alignment in metal/oxide/semiconductor and organic dye/oxide systems

    Science.gov (United States)

    Bersch, Eric

    The alignment between the energy levels of the constituent materials of metal-oxide-semiconductor field effect transistors (MOSFET's) and dye sensitized solar cell (DSSC's) is a key property that is critical to the functions of these devices. We have measured the energy level alignment (band offsets) for metal/oxide/semiconductor (MOS) systems with high-kappa gate oxides and metal gates, and for organic dye/oxide systems. The combination of UV photoemission spectroscopy (UPS) and inverse photoemission spectroscopy (IPS) in the same vacuum system was used to measure both the occupied and unoccupied density of states (DOS), respectively, of these materials systems. Additional soft X-ray photoemission spectroscopy (SXPS) measurements were made of both the valence bands and core levels of the high-kappa systems. The combination of the UPS, IPS and SXPS measurements were used to determine the band offsets between the high-kappa oxides and the Si substrates of thin film oxide/Si samples. To find the metal-oxide band offsets, thin metal layers were sequentially deposited on the oxide surfaces, followed by spectroscopic measurements. These measurements, combined with the measurements from the clean oxide surfaces, were used to find the metal-oxide band offsets. Metal-oxide band offset values were also calculated by the Interface Gap State (IGS) model. We compared the experimental metal-oxide conduction band offset (CBO) values with those calculated using the IGS model, and found that they tended to agree well for Ru/oxide and Ti/oxide systems, but not as well for Al/oxide systems. Through core level spectroscopy, we correlated observations of the composition of the metallic layers with the trends in agreement between the experimental and IGS CBO values, which led to the conclusion that the IGS model gives accurate values for the CBO for systems with chemically abrupt interfaces. Core level spectroscopy of the MOS systems also showed that Al and Ti overlayers reduced the

  1. Enhanced Emission by Accumulated Charges at Organic/Metal Interfaces Generated during the Reverse Bias of Organic Light Emitting Diodes

    Directory of Open Access Journals (Sweden)

    Soichiro Nozoe

    2017-10-01

    Full Text Available A high frequency rectangular alternating voltage was applied to organic light emitting diodes (OLEDs with the structure ITO/TPD/Alq3/Al and ITO/CoPc/Alq3/Al, where ITO is indium-tin-oxide, TPD is 4,4′-bis[N-phenyl-N-(m-tolylamino]biphenyl, CoPc is cobalt phthalocyanine, and Alq3 is Tris(8-quinolinolatoaluminum, and the effect on emission of the reverse bias was examined. The results reveal that the emission intensity under an alternating reverse-forward bias is greater than that under an alternating zero-forward bias. The difference in the emission intensity (∆I increased both for decreasing frequency and increasing voltage level of the reverse bias. In particular, the change in emission intensity was proportional to the voltage level of the reverse bias given the same frequency. To understand ΔI, this paper proposes a model in which an OLED works as a capacitor under reverse bias, where positive and negative charges accumulate on the metal/organic interfaces. In this model, the emission enhancement that occurs during the alternating reverse-forward bias is rationalized as a result of the charge accumulation at the organic/metal interfaces during the reverse bias, which possibly modulates the vacuum level shifts at the organic/metal interfaces to reduce both the hole injection barrier at the organic/ITO interface and the electron injection barrier at the organic/Al interface under forward bias.

  2. Adhesion energy in the metal/oxide system for the case of high-temperature oxidation of nickel-based superalloys

    Science.gov (United States)

    Moskvichev, V. V.; Sukhodoeva, N. V.; Fedorova, E. N.; Popov, A. S.

    2017-10-01

    The microstructure of the oxide layer is studied and the adhesion energy of the metal/oxide interface is determined after high-temperature isothermal oxidation ( T = 1150°C) of a single-crystal commercial René N5 nickel alloy. Experiments upon heating and rapid cooling are performed to initiate failure of the oxide layer. The elastic energy of the metal/oxide interface is determined using the model of circular buckling followed by edge delamination. Calculations are conducted for a homogeneous alumina layer and with allowance for the multilayer structure that forms at the initial stages of alloy oxidation. The adhesion energy is 72 and 27 J/m2 for these cases, respectively.

  3. Electronic properties of semiconductor surfaces and metal/semiconductor interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Tallarida, M.

    2005-05-15

    This thesis reports investigations of the electronic properties of a semiconductor surface (silicon carbide), a reactive metal/semiconductor interface (manganese/silicon) and a non-reactive metal/semiconductor interface (aluminum-magnesium alloy/silicon). The (2 x 1) reconstruction of the 6H-SiC(0001) surface has been obtained by cleaving the sample along the (0001) direction. This reconstruction has not been observed up to now for this compound, and has been compared with those of similar elemental semiconductors of the fourth group of the periodic table. This comparison has been carried out by making use of photoemission spectroscopy, analyzing the core level shifts of both Si 2p and C 1s core levels in terms of charge transfer between atoms of both elements and in different chemical environments. From this comparison, a difference between the reconstruction on the Si-terminated and the C-terminated surface was established, due to the ionic nature of the Si-C bond. The growth of manganese films on Si(111) in the 1-5 ML thickness range has been studied by means of LEED, STM and photoemission spectroscopy. By the complementary use of these surface science techniques, two different phases have been observed for two thickness regimes (<1 ML and >1 ML), which exhibit a different electronic character. The two reconstructions, the (1 x 1)-phase and the ({radical}3 x {radical}3)R30 -phase, are due to silicide formation, as observed in core level spectroscopy. The growth proceeds via island formation in the monolayer regime, while the thicker films show flat layers interrupted by deep holes. On the basis of STM investigations, this growth mode has been attributed to strain due to lattice mismatch between the substrate and the silicide. Co-deposition of Al and Mg onto a Si(111) substrate at low temperature (100K) resulted in the formation of thin alloy films. By varying the relative content of both elements, the thin films exhibited different electronic properties

  4. Thin films of metal oxides on metal single crystals: Structure and growth by scanning tunneling microscopy

    International Nuclear Information System (INIS)

    Galloway, H.C.

    1995-12-01

    Detailed studies of the growth and structure of thin films of metal oxides grown on metal single crystal surfaces using Scanning Tunneling Microscopy (STM) are presented. The oxide overlayer systems studied are iron oxide and titanium oxide on the Pt(III) surface. The complexity of the metal oxides and large lattice mismatches often lead to surface structures with large unit cells. These are particularly suited to a local real space technique such as scanning tunneling microscopy. In particular, the symmetry that is directly observed with the STM elucidates the relationship of the oxide overlayers to the substrate as well as distinguishing, the structures of different oxides

  5. Metal Oxide Nanosensors Using Polymeric Membranes, Enzymes and Antibody Receptors as Ion and Molecular Recognition Elements

    Directory of Open Access Journals (Sweden)

    Magnus Willander

    2014-05-01

    Full Text Available The concept of recognition and biofunctionality has attracted increasing interest in the fields of chemistry and material sciences. Advances in the field of nanotechnology for the synthesis of desired metal oxide nanostructures have provided a solid platform for the integration of nanoelectronic devices. These nanoelectronics-based devices have the ability to recognize molecular species of living organisms, and they have created the possibility for advanced chemical sensing functionalities with low limits of detection in the nanomolar range. In this review, various metal oxides, such as ZnO-, CuO-, and NiO-based nanosensors, are described using different methods (receptors of functionalization for molecular and ion recognition. These functionalized metal oxide surfaces with a specific receptor involve either a complex formation between the receptor and the analyte or an electrostatic interaction during the chemical sensing of analytes. Metal oxide nanostructures are considered revolutionary nanomaterials that have a specific surface for the immobilization of biomolecules with much needed orientation, good conformation and enhanced biological activity which further improve the sensing properties of nanosensors. Metal oxide nanostructures are associated with certain unique optical, electrical and molecular characteristics in addition to unique functionalities and surface charge features which shows attractive platforms for interfacing biorecognition elements with effective transducing properties for signal amplification. There is a great opportunity in the near future for metal oxide nanostructure-based miniaturization and the development of engineering sensor devices.

  6. Nanotoxicity: oxidative stress mediated toxicity of metal and metal oxide nanoparticles.

    Science.gov (United States)

    Sarkar, Abhijit; Ghosh, Manoranjan; Sil, Parames Chandra

    2014-01-01

    Metal and metal oxide nanoparticles are often used as industrial catalysts or to improve product's functional properties. Recent advanced nanotechnology have been expected to be used in various fields, ranging from sensors, environmental remediation to biomedicine, medical biology and imaging, etc. However, the growing use of nanoparticles has led to their release into environment and increased levels of these particles at nearby sites or the surroundings of their manufacturing factories become obvious. The toxicity of metal and metal oxide nanoparticles on humans, animals, and certainly to the environment has become a major concern to our community. However, controversies still remain with respect to the toxic effects and the mechanisms of these nanoparticles. The scientific community now feels that an understanding of the toxic effects is necessary to handle these nanoparticles and their use. A new discipline, named nanotoxicology, has therefore been developed that basically refers to the study of the interactions of nanoparticles with biological systems and also measures the toxicity level related to human health. Nanoparticles usually generate reactive oxygen species to a greater extent than micro-sized particles resulting in increased pro-inflammatory reactions and oxidative stress via intracellular signaling pathways. In this review, we mainly focus on the routes of exposure of some metal and metal oxide nanoparticles and how these nanoparticles affect us or broadly the cells of our organs. We would also like to discuss the responsible mechanism(s) of the nanoparticle-induced reactive oxygen species mediated organ pathophysiology. A brief introduction of the characterization and application of these nanoparticles has also been included in the article.

  7. Investigations of the electronic, magnetic and crystalline structure of perovskite oxides and an oxide-oxide interface

    International Nuclear Information System (INIS)

    Raisch, Christoph Werner

    2013-01-01

    The mineral perovskite CaTiO 3 lends its name to the class of compounds with composition ABX 3 , which have the same type of crystal structure known as the perovskite structure. Here, A and B are cations while X is typically a halogen or oxygen anion. The bigger cation A and the X anions form a cubic close packing AX 3 with the smaller B cation occupying one quarter of the octahedral sites. The underlying work deals with three classes of perovskite oxides, the ''titanates'', the ''cuprates'' and the ''manganites'', where the central B cations are Ti, Cu and Mn respectively, each class with very characteristic properties. Strontium titanate, STO, like so many oxides is an insulator, yet paraelectric and diamagnetic. It gained special interest as a commercially available, high quality substrate for the growth of hightemperature superconductors and other oxide thin films. The huge class of perovskite cuprates is most famous for members like YBCO, the well-known high-temperature superconductor. Finally, the doped, mixed-valent perovskite manganites LXMO (here X = Sr, Ca, Ce) have to be mentioned. They appeared on the screen of experimental and theoretical physicists in the 1950s when ferromagnetism and magnetoresistance were discovered in these compounds, leading to the theory of double exchange. In the mid-1990s they further increased their importance, following the description of the Jahn-Teller polaron and the discovery of the colossal magnetoresistance phenomenom. They may be derived from an insulator, LaMnO 3 , but the doping allows the control of electric and magnetic properties over a wide range, i.e. from insulating behavior to metallic conductivity or from diamagnet to ferromagnet. Further notable effects are found when electric or magnetic fields are applied, including spin polarization and the related effect of colossal magnetoresistance. These substances may be approximated as consisting of

  8. Surface Preparation and Deposited Gate Oxides for Gallium Nitride Based Metal Oxide Semiconductor Devices

    Science.gov (United States)

    Long, Rathnait D.; McIntyre, Paul C.

    2012-01-01

    The literature on polar Gallium Nitride (GaN) surfaces, surface treatments and gate dielectrics relevant to metal oxide semiconductor devices is reviewed. The significance of the GaN growth technique and growth parameters on the properties of GaN epilayers, the ability to modify GaN surface properties using in situ and ex situ processes and progress on the understanding and performance of GaN metal oxide semiconductor (MOS) devices are presented and discussed. Although a reasonably consistent picture is emerging from focused studies on issues covered in each of these topics, future research can achieve a better understanding of the critical oxide-semiconductor interface by probing the connections between these topics. The challenges in analyzing defect concentrations and energies in GaN MOS gate stacks are discussed. Promising gate dielectric deposition techniques such as atomic layer deposition, which is already accepted by the semiconductor industry for silicon CMOS device fabrication, coupled with more advanced physical and electrical characterization methods will likely accelerate the pace of learning required to develop future GaN-based MOS technology.

  9. Oxidation of vanadium metal in oxygen plasma and their characterizations

    Directory of Open Access Journals (Sweden)

    Rabindar Kumar Sharma

    2015-09-01

    Full Text Available In this report, the role of oxygen plasma on oxidation of vanadium (V metal and the volatilization of its oxides has been studied as a function of source (V metal strip temperature (Tss and oxygen partial pressure (PO2. The presence of O2-plasma not only enhances the oxidation rate but also ficilitates in transport of oxide molecules from metal to substrate, as confirmed by the simultanous deposition of oxide film onto substrate. Both the oxidized metal strips and oxide films deposited on substrates are characterized separately. The structural and vibrational results evidence the presence of two different oxide phases (i.e. orthorhombic V2O5 and monocilinic V O2 in oxide layers formed on V metal strips, whereas the oxide films deposited on substrates exhibit only orthorhombic phase (i.e. V2O5. The decrease in peak intensities recorded from heated V metal strips on increasing Tss points out the increment in the rate of oxide volatilization, which also confirms by the oxide layer thickness measurements. The SEM results show the noticeable surface changes on V-strips as the function of Tss and PO2 and their optimum values are recorded to be 500   ˚ C and 7.5 × 10−2 Torr, respectively to deposit maximum thick oxide film on substrate. The formation of microcracks on oxidized V-strips, those responsible to countinue oxidation is also confirmed by SEM results. The compositional study of oxide layers formed on V-strips, corroborates their pureness and further assures about the existence of mixed oxide phases. The effect of oxygen partial pressure on oxidation of V-metal has also been discussed in the present report. All the results are well in agreement to each other.

  10. Oxidation of vanadium metal in oxygen plasma and their characterizations

    Science.gov (United States)

    Sharma, Rabindar Kumar; Singh, Megha; Kumar, Prabhat; Reddy, G. B.

    2015-09-01

    In this report, the role of oxygen plasma on oxidation of vanadium (V) metal and the volatilization of its oxides has been studied as a function of source (V metal strip) temperature (Tss) and oxygen partial pressure (PO2). The presence of O2-plasma not only enhances the oxidation rate but also ficilitates in transport of oxide molecules from metal to substrate, as confirmed by the simultanous deposition of oxide film onto substrate. Both the oxidized metal strips and oxide films deposited on substrates are characterized separately. The structural and vibrational results evidence the presence of two different oxide phases (i.e. orthorhombic V2O5 and monocilinic V O2) in oxide layers formed on V metal strips, whereas the oxide films deposited on substrates exhibit only orthorhombic phase (i.e. V2O5). The decrease in peak intensities recorded from heated V metal strips on increasing Tss points out the increment in the rate of oxide volatilization, which also confirms by the oxide layer thickness measurements. The SEM results show the noticeable surface changes on V-strips as the function of Tss and PO2 and their optimum values are recorded to be 500 ˚ C and 7.5 × 10-2 Torr, respectively to deposit maximum thick oxide film on substrate. The formation of microcracks on oxidized V-strips, those responsible to countinue oxidation is also confirmed by SEM results. The compositional study of oxide layers formed on V-strips, corroborates their pureness and further assures about the existence of mixed oxide phases. The effect of oxygen partial pressure on oxidation of V-metal has also been discussed in the present report. All the results are well in agreement to each other.

  11. An improved method of preparation of nanoparticular metal oxide catalysts

    DEFF Research Database (Denmark)

    2014-01-01

    The present invention concerns an improved method of preparation of nanoparticular vanadium oxide/anatase titania catalysts having a narrow particle size distribution. In particular, the invention concerns preparation of nanoparticular vanadium oxide/anatase titania catalyst precursors comprising...... combustible crystallization seeds upon which the catalyst metal oxide is coprecipitated with the carrier metal oxide, which crystallization seeds are removed by combustion in a final calcining step....

  12. Sol-Gel/Hydrothermal Synthesis of Mixed Metal Oxide

    African Journals Online (AJOL)

    Mixed metal oxides of titanium and zinc nanocomposites were prepared through sol-gel method under hydrothermal condition ... Keywords: Nanocomposites, Titanium dioxide, Zinc oxide, Particle sizes, Optical property, X-Ray Diffraction. ABSTRACT. 321 ... doping with other semiconductors like zinc oxide, aluminium oxide ...

  13. k-asymmetric spin splitting at the interface between transition metal ferromagnets and heavy metals

    KAUST Repository

    Grytsiuk, Sergii

    2016-05-23

    We systematically investigate the spin-orbit coupling-induced band splitting originating from inversion symmetry breaking at the interface between a Co monolayer and 4d (Tc, Ru, Rh, Pd, and Ag) or 5d (Re, Os, Ir, Pt, and Au) transition metals. In spite of the complex band structure of these systems, the odd-in-k spin splitting of the bands displays striking similarities with the much simpler Rashba spin-orbit coupling picture. We establish a clear connection between the overall strength of the odd-in-k spin splitting of the bands and the charge transfer between the d orbitals at the interface. Furthermore, we show that the spin splitting of the Fermi surface scales with the induced orbital moment, weighted by the spin-orbit coupling.

  14. Biexciton Dissociation Efficiency at Quantum Dot-Oxide Interfaces

    Science.gov (United States)

    Bonn, Mischa; Wang, Hai; Canovas, Enrique

    Harvesting multiexcitons populating semiconductor quantum dots (generated by carrier multiplication, CM) has been proposed as a path towards higher efficiencies in photovoltaic devices. Although CM efficiency has been widely interrogated in colloidal QD solutions, less focus has been placed on the physics regarding biexciton collection at electrodes. We investigate interfacial biexciton transfer dynamics from PbS quantum dots directly nucleated onto mesoporous SnO2 films as a function of impinging photon flux and photon energy. A priori, this system seems very well-suited for achieving efficient biexciton dissociation, as the ultrafast QD-to-oxide transfer rate for 800nm excitation is substantially faster than Auger relaxation. Remarkably, the biexciton dissociation efficiency is below the detection efficiency, i.e. essentially zero. This seemingly counterintuitive result can be understood by noting that efficient hot electron transfer at the QD-oxide interface can compete with CM within the QDs. Hot electron transfer is observed to occur on sub-100 fs timescales, nulling the CM efficiency. Implications of these results for solar energy conversion are discussed.

  15. Toward garnet electrolyte–based Li metal batteries: An ultrathin, highly effective, artificial solid-state electrolyte/metallic Li interface

    Science.gov (United States)

    Fu, Kun (Kelvin); Gong, Yunhui; Liu, Boyang; Zhu, Yizhou; Xu, Shaomao; Yao, Yonggang; Luo, Wei; Wang, Chengwei; Lacey, Steven D.; Dai, Jiaqi; Chen, Yanan; Mo, Yifei; Wachsman, Eric; Hu, Liangbing

    2017-01-01

    Solid-state batteries are a promising option toward high energy and power densities due to the use of lithium (Li) metal as an anode. Among all solid electrolyte materials ranging from sulfides to oxides and oxynitrides, cubic garnet–type Li7La3Zr2O12 (LLZO) ceramic electrolytes are superior candidates because of their high ionic conductivity (10−3 to 10−4 S/cm) and good stability against Li metal. However, garnet solid electrolytes generally have poor contact with Li metal, which causes high resistance and uneven current distribution at the interface. To address this challenge, we demonstrate a strategy to engineer the garnet solid electrolyte and the Li metal interface by forming an intermediary Li-metal alloy, which changes the wettability of the garnet surface (lithiophobic to lithiophilic) and reduces the interface resistance by more than an order of magnitude: 950 ohm·cm2 for the pristine garnet/Li and 75 ohm·cm2 for the surface-engineered garnet/Li. Li7La2.75Ca0.25Zr1.75Nb0.25O12 (LLCZN) was selected as the solid-state electrolyte (SSE) in this work because of its low sintering temperature, stabilized cubic garnet phase, and high ionic conductivity. This low area-specific resistance enables a solid-state garnet SSE/Li metal configuration and promotes the development of a hybrid electrolyte system. The hybrid system uses the improved solid-state garnet SSE Li metal anode and a thin liquid electrolyte cathode interfacial layer. This work provides new ways to address the garnet SSE wetting issue against Li and get more stable cell performances based on the hybrid electrolyte system for Li-ion, Li-sulfur, and Li-oxygen batteries toward the next generation of Li metal batteries. PMID:28435874

  16. Metal Oxide Nanoparticle Photoresists for EUV Patterning

    KAUST Repository

    Jiang, Jing

    2014-01-01

    © 2014SPST. Previous studies of methacrylate based nanoparticle have demonstrated the excellent pattern forming capability of these hybrid materials when used as photoresists under 13.5 nm EUV exposure. HfO2 and ZrO2 methacrylate resists have achieved high resolution (∼22 nm) at a very high EUV sensitivity (4.2 mJ/cm2). Further investigations into the patterning process suggests a ligand displacement mechanism, wherein, any combination of a metal oxide with the correct ligand could generate patterns in the presence of the suitable photoactive compound. The current investigation extends this study by developing new nanoparticle compositions with transdimethylacrylic acid and o-toluic acid ligands. This study describes their synthesis and patterning performance under 248 nm KrF laser (DUV) and also under 13.5 nm EUV exposures (dimethylacrylate nanoparticles) for the new resist compositions.

  17. Origin of interface states and oxide charges generated by ionizing radiation

    International Nuclear Information System (INIS)

    Sah, C.T.

    1976-01-01

    The randomly located trivalent silicon atoms are shown to account for the thermally generated interface states at the SiO 2 -Si interface. The interface state density is greatly reduced in water containing ambients at low temperatures (450 0 C) by forming trivalent silicon hydroxide bonds. Interface states are regenerated when the /triple bond/Si-OH bonds are broken by ionizing radiation and the OH ions are drifted away. In the bulk of the oxide film, the trivalent silicon and the interstitial oxygen donor centers are shown to be responsible for the heat and radiation generated positive space charge build-up (oxide charge) in thermally grown silicon oxide

  18. Segregation of boron implanted into silicon on angular configurations of silicon/silicon dioxide oxidation interface

    CERN Document Server

    Tarnavskij, G A; Obrekht, M S

    2001-01-01

    One studies segregation of boron implanted into silicon when a wave (interface) of oxidation moves within it. There are four types of angular configurations of SiO sub 2 /Si oxidation interface, that is: direct and reverse shoulders, trench type cavities and a square. By means of computer-aided simulation one obtained and analyzed complex patterns of B concentration distribution within Si, SiO sub 2 domains and at SiO sub 2 /Si interface for all types of angular configurations of the oxidation interface

  19. Preventing Oxide Adhesion of Liquid Metal Alloys to Enable Actuation in Microfluidic Systems

    Science.gov (United States)

    Joshipura, Ishan; Johnson, Alexander; Ayers, Hudson; Dickey, Michael

    This work explores the wetting behavior of an oxide-coated liquid metal, eutectic alloy of gallium and indium (`EGaIn'), which remains a liquid at room temperature. Liquid metals uniquely combine fluidity with metallic properties. Combined, these properties enable soft, stretchable, and shape reconfigurable electronics with `softer than skin' interfaces. Ga forms spontaneously a thin surface oxide that alters its wetting behavior and makes it difficult to move across surfaces without leaving residue behind. We examine the effects of surface roughness (i.e., Cassie-Baxter state) and lubrication to minimize adhesion of Ga oxide to surfaces. Lubricated surfaces create a `slip-layer' of liquid between the metal and surface that also inhibits wetting. This slip layer allows the metal to move reversibly through microchannels by preventing adhesion of the oxide. The metal may be pumped or moved by using low voltages or pneumatic actuation. Optical microscopy confirms the importance of the slip-layer, which enables non-stick motion of the metal through capillaries. Finally, electrochemical impedance spectroscopy characterizes the electrohydrodynanic motion of EGaIn in capillary systems.

  20. Synthesis and characterization of metal oxide nanorod brushes

    Indian Academy of Sciences (India)

    WINTEC

    ducing chromium ions during the synthesis of alumina rods. Keywords. Metal oxide nanorods; nanorod brushes; alumina nanorods; MoO3 nanorods; ZnO nanorods; ruby nanorods. 1. Introduction. Synthesis of one-dimensional metal oxide nanostructures is getting enormous attention in recent years due to their potential ...

  1. Recent Development in Metal Oxides and Related Materials

    Indian Academy of Sciences (India)

    Unknown

    Recent Development in Metal Oxides and. Related Materials. FOREWORD. This special issue of the Journal of Chemical Sciences contains a col- lection of articles contributed by the participants of Recent Development in Metal Oxides ... energy transfer, nano particle synthesis, magnetic transport properties of rare earth ...

  2. A novel parameter estimation method for metal oxide surge arrester ...

    Indian Academy of Sciences (India)

    with experimental results. Keywords. Metal oxide surge arrester models; PSO; ACO; parameter estimation;. EMTP. 1. Introduction. Metal oxide (MO) surge arresters are widely used as protective devices against switching and lightning over-voltages in power systems. The proper nonlinear voltage-current characteristics,. ∗.

  3. Stabilization of electrocatalytic metal nanoparticles at metal-metal oxide-graphene triple junction points.

    Science.gov (United States)

    Kou, Rong; Shao, Yuyan; Mei, Donghai; Nie, Zimin; Wang, Donghai; Wang, Chongmin; Viswanathan, Vilayanur V; Park, Sehkyu; Aksay, Ilhan A; Lin, Yuehe; Wang, Yong; Liu, Jun

    2011-03-02

    Carbon-supported precious metal catalysts are widely used in heterogeneous catalysis and electrocatalysis, and enhancement of catalyst dispersion and stability by controlling the interfacial structure is highly desired. Here we report a new method to deposit metal oxides and metal nanoparticles on graphene and form stable metal-metal oxide-graphene triple junctions for electrocatalysis applications. We first synthesize indium tin oxide (ITO) nanocrystals directly on functionalized graphene sheets, forming an ITO-graphene hybrid. Platinum nanoparticles are then deposited, forming a unique triple-junction structure (Pt-ITO-graphene). Our experimental work and periodic density functional theory (DFT) calculations show that the supported Pt nanoparticles are more stable at the Pt-ITO-graphene triple junctions. Furthermore, DFT calculations suggest that the defects and functional groups on graphene also play an important role in stabilizing the catalysts. These new catalyst materials were tested for oxygen reduction for potential applications in polymer electrolyte membrane fuel cells, and they exhibited greatly enhanced stability and activity.

  4. Laboratory studies of refractory metal oxide smokes

    International Nuclear Information System (INIS)

    Nuth, J.A.; Nelson, R.N.; Donn, B.

    1989-01-01

    Studies of the properties of refractory metal oxide smokes condensed from a gas containing various combinations of SiH4, Fe(CO)5, Al(CH3)3, TiCl4, O2 and N2O in a hydrogen carrier stream at 500 K greater than T greater than 1500 K were performed. Ultraviolet, visible and infrared spectra of pure, amorphous SiO(x), FeO(x), AlO(x) and TiO(x) smokes are discussed, as well as the spectra of various co-condensed amorphous oxides, such as FE(x)SiO(y) or Fe(x)AlO(y). Preliminary studies of the changes induced in the infrared spectra of iron-containing oxide smokes by vacuum thermal annealing suggest that such materials become increasingly opaque in the near infrared with increased processing: hydration may have the opposite effect. More work on the processing of these materials is required to confirm such a trend: this work is currently in progress. Preliminary studies of the ultraviolet spectra of amorphous Si2O3 and MgSiO(x) smokes revealed no interesting features in the region from 200 to 300 nm. Studies of the ultraviolet spectra of both amorphous, hydrated and annealed SiO(x), TiO(x), AlO(x) and FeO(x) smokes are currently in progress. Finally, data on the oxygen isotopic composition of the smokes produced in the experiments are presented, which indicate that the oxygen becomes isotopically fractionated during grain condensation. Oxygen in the grains is as much as 3 percent per amu lighter than the oxygen in the original gas stream. The authors are currently conducting experiments to understand the mechanism by which fractionation occurs

  5. On the origin of metallic conductivity at the interface of LaAlO3/SrTiO3

    DEFF Research Database (Denmark)

    Chen, Yunzhong; Christensen, Dennis; Trier, Felix

    2012-01-01

    To determine the origin of the quasi-two-dimensional electron gas formed at the interface between the two complex oxides of LaAlO3 (LAO) and SrTiO3 (STO), various amorphous films of LAO, La2O3, Al2O3, and La7/8Sr1/8MnO3 (LSMO), were deposited on TiO2-terminated (0 0 1) STO substrates by pulsed...... laser deposition at room temperature. Metallic interfaces are observed when the over-layers are amorphous LAO, La2O3, or Al2O3, while insulating interfaces are observed when the over-layer is LSMO. The interfacial conductivity of these SrTiO3-based hetero-structures shows strong dependence on both film...

  6. Influence of metal lattice vacancies on the oxidation of high temperature materials

    International Nuclear Information System (INIS)

    Gibbs, G.B.; Hales, R.

    1977-01-01

    When an oxide scale grows on a metal by the outward diffusion of cations, it is anticipated theoretically that lattice vacancies will be injected into the metal substrate. There is a large body of evidence supporting this proposition including electron microscope observations on the climb of secondary defects, the optical microscopy of voids, and some tracer diffusion effects. The influence of a vacancy supersaturation on the kinetics of oxidation is considered in detail and an analogy is drawn between the effect of vacancy concentrations and variations in oxygen potential on scale growth rates. However, for most practical situations the effects are shown to be small. Injected lattice vacancies are annihilated at various internal sinks such as the scale/metal interface or defects within the matrix. Factors which determine where vacancies are likely to be annihilated are discussed. Vacancy annihilation produces dimensional changes in the metal substrate which favour the eventual breakdown of the scale/metal interface and loss of scale adhesion. Thus a compact scale growing by the outward diffusion of vacancies has inherent long-term instability. Previously compact scale overlying an interfacial void is able to dissociate to produce microchannels which allow gas access to the underlying metal. this does not necessarily result in a loss of corrosion protection; an inner layer of oxide can form at a parabolic rate in the vacancy condensation zone made available by the outward diffusion of cations. Oxidation by CO 2 , H 2 0 and CO-CO 2 mixtures is discussed, and the preferential oxidation of one metal in an alloy. (author)

  7. High-Pressure Thermodynamic Properties of f-electron Metals, Transition Metal Oxides, and Half-Metallic Magnets

    International Nuclear Information System (INIS)

    Richard T. Scalettar; Warren E. Pickett

    2005-01-01

    This project involves research into the thermodynamic properties of f-electron metals, transition metal oxides, and half-metallic magnets at high pressure. These materials are ones in which the changing importance of electron-electron interactions as the distance between atoms is varied can tune the system through phase transitions from localized to delocalized electrons, from screened to unscreened magnetic moments, and from normal metal to one in which only a single spin specie can conduct. Three main thrusts are being pursued: (1) Mott transitions in transition metal oxides, (2) magnetism in half-metallic compounds, and (3) large volume-collapse transitions in f-band metals

  8. High-Pressure Thermodynamic Properties of f-electron Metals, Transition Metal Oxides, and Half-Metallic Magnets

    Energy Technology Data Exchange (ETDEWEB)

    Scalettar, Richard T.; Pickett, Warren E.

    2004-07-01

    This project involves research into the thermodynamic properties of f-electron metals, transition metal oxides, and half-metallic magnets at high pressure. These materials are ones in which the changing importance of electron-electron interactions as the distance between atoms is varied can tune the system through phase transitions from localized to delocalized electrons, from screened to unscreened magnetic moments, and from normal metal to one in which only a single spin specie can conduct. Three main thrusts are being pursued: (1) Mott transitions in transition metal oxides, (2) magnetism in half-metallic compounds, and (3) large volume-collapse transitions in f-band metals.

  9. High-Pressure Thermodynamic Properties of f-electron Metals, Transition Metal Oxides, and Half-Metallic Magnets

    Energy Technology Data Exchange (ETDEWEB)

    Richard T. Scalettar; Warren E. Pickett

    2005-08-02

    This project involves research into the thermodynamic properties of f-electron metals, transition metal oxides, and half-metallic magnets at high pressure. These materials are ones in which the changing importance of electron-electron interactions as the distance between atoms is varied can tune the system through phase transitions from localized to delocalized electrons, from screened to unscreened magnetic moments, and from normal metal to one in which only a single spin specie can conduct. Three main thrusts are being pursued: (i) Mott transitions in transition metal oxides, (ii) magnetism in half-metallic compounds, and (iii) large volume-collapse transitions in f-band metals.

  10. Miscibility and oxidation rate of the simulated metallic spent fuel

    Energy Technology Data Exchange (ETDEWEB)

    You, K. S.; Joo, J. S.; Shin, Y. J.; Oh, S. C. [KAERI, Taejon (Korea, Republic of)

    1999-10-01

    The simulated metallic spent fuel was fabricated by using Uranium, Neodymium and Palladium in order to study the miscibility of Neodymium and Palladium with Uranium. For analysis of long-term safty on the metallized spent fuel, the simulated metallic spent fuel was oxidized under pure oxygen environment at 183{approx}250 deg C. From the results, the oxidation rate correlation and activation energy were obtained.

  11. Synthesis, Characterization, and Ultrafast Dynamics of Metal, Metal Oxide, and Semiconductor Nanomaterials

    OpenAIRE

    Wheeler, Damon Andreas

    2013-01-01

    SYNTHESIS, CHARACTERIZATION, AND ULTRAFAST DYNAMICS OF METAL, METAL OXIDE, AND SEMICONDUCTOR NANOMATERIALSABSTRACTThe optical properties of each of the three main classes of inorganic nanomaterials, metals, metal oxides, and semiconductors differ greatly due to the intrinsically different nature of the materials. These optical properties are among the most fascinating and useful aspects of nanomaterials with applications spanning cancer treatment, sensors, lasers, and solar cells. One techn...

  12. Growth of aluminum oxide on silicon carbide with an atomically sharp interface

    DEFF Research Database (Denmark)

    Silva, Ana Gomes; Pedersen, Kjeld; Li, Zheshen

    2017-01-01

    The development of SiC wafers with properties suitable for electronic device fabrication is now well established commercially. A critical issue for developing metal-oxide-semiconductor field effect transistor devices of SiC is the choice of dielectric materials for surface passivation and insulat......The development of SiC wafers with properties suitable for electronic device fabrication is now well established commercially. A critical issue for developing metal-oxide-semiconductor field effect transistor devices of SiC is the choice of dielectric materials for surface passivation...... this system up to around 600 °C (all in ultrahigh vacuum). This converts all the SiO2 into a uniform layer of Al2O3 with an atomically sharp interface between the Al2O3 and the Si surface. In the present work, the same procedures are applied to form Al2O3 on a SiC film grown on top of Si (111). The results...

  13. Model potential for the description of metal/organic interface states

    Science.gov (United States)

    Armbrust, Nico; Schiller, Frederik; Güdde, Jens; Höfer, Ulrich

    2017-01-01

    We present an analytical one-dimensional model potential for the description of electronic interface states that form at the interface between a metal surface and flat-lying adlayers of π-conjugated organic molecules. The model utilizes graphene as a universal representation of these organic adlayers. It predicts the energy position of the interface state as well as the overlap of its wave function with the bulk metal without free fitting parameters. We show that the energy of the interface state depends systematically on the bond distance between the carbon backbone of the adayers and the metal. The general applicability and robustness of the model is demonstrated by a comparison of the calculated energies with numerous experimental results for a number of flat-lying organic molecules on different closed-packed metal surfaces that cover a large range of bond distances. PMID:28425444

  14. Catalysis using hydrous metal oxide ion exchanges

    Science.gov (United States)

    Dosch, Robert G.; Stephens, Howard P.; Stohl, Frances V.

    1985-01-01

    In a process which is catalyzed by a catalyst comprising an active metal on a carrier, said metal being active as a catalyst for the process, an improvement is provided wherein the catalyst is a hydrous, alkali metal or alkaline earth metal titanate, zirconate, niobate or tantalate wherein alkali or alkaline earth metal cations have been exchanged with a catalytically effective amount of cations of said metal.

  15. Surface modes at metallic an photonic crystal interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Dai, Weitao [Iowa State Univ., Ames, IA (United States)

    2009-01-01

    A surface mode is an electromagnetic field distribution bounded at a surface. It decays exponentially with the distance from the surface on both sides of the surface and propagates at the surface. The surface mode exists at a metal-dielectric interface as surface plasmon (1) or at a photonic crystal surface terminated properly (34; 35; 36). Besides its prominent near-filed properties, it can connect structures at its propagation surface and results in far-field effects. Extraordinary transmission (EOT) and beaming are two examples and they are the subjects I am studying in this thesis. EOT means the transmission through holes in an opaque screen can be much larger than the geometrical optics limitation. Based on our everyday experience about shadows, the transmission equals the filling ratio of the holes in geometrical optics. The conventional diffraction theory also proved that the transmission through a subwavelength circular hole in an infinitely thin perfect electric conductor (PEC) film converges to zero when the hole's dimension is much smaller than the wavelength (40). Recently it is discovered that the transmission can be much larger than the the filling ratio of the holes at some special wavelengths (41). This cannot be explained by conventional theories, so it is called extraordinary transmission. It is generally believed that surface plasmons play an important role (43; 44) in the EOT through a periodic subwavelength hole array in a metallic film. The common theories in literatures are based on these arguments. The surface plasmons cannot be excited by incident plane waves directly because of momentum mismatch. The periodicity of the hole arrays will provide addition momentum. When the momentum-matching condition of surface plasmons is satisfied, the surface plasmons will be excited. Then these surface plasmons will collect the energy along the input surface and carry them to the holes. So the transmission can be bigger than the filling ratio. Based

  16. Metal-support interactions in systems palladium deposited on oxidized tungsten surfaces

    Czech Academy of Sciences Publication Activity Database

    Plšek, Jan; Jirka, Ivan; Nikolajenko, Vladimír; Knor, Zlatko

    2006-01-01

    Roč. 600, č. 18 (2006), s. 3943-3949 ISSN 0039-6028 R&D Projects: GA ČR GA202/05/0244 Institutional research plan: CEZ:AV0Z40400503 Keywords : field emission microscopy * thermal desorption spectroscopy * synchrotron radiation photoelectron spectroscopy * growth * metal-oxide interfaces Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.880, year: 2006

  17. Preparation and characterization of several transition metal oxides

    International Nuclear Information System (INIS)

    Wold, A.; Dwight, K.

    1989-01-01

    The structure-property relationships of several conducting transition metal oxides, as well as their preparative methods, are presented in this paper. The importance of preparing homogeneous phases with precisely known stoichiometry is emphasized. A comparison is also made of the various techniques used to prepare both polycrystalline and single crystal samples. For transition metal oxides, the metallic properties are discussed either in terms of metal-metal distances which are short enough to result in metallic behavior, or in terms of the formation of a π* conduction band resulting from covalent metal-oxygen interactions. Metallic behavior is observed when the conduction bands are populated with either electrons or holes. The concentration of these carriers can be affected by either cation or anion substitutions. The discussion in this presentation will be limited to the elements Re, Ti, V, Cr, Mo, and Cu

  18. Metallic Nanocomposites as Next-Generation Thermal Interface Materials

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Xuhui [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Narumanchi, Sreekant V [National Renewable Energy Laboratory (NREL), Golden, CO (United States); King, Charles C [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Nagabandi, Nirup [Texas A& M University; Oh, Jun Kyun [Texas A& M University; Akbulut, Mustafa [Texas A& M University; Yegin, Cengiz [Texas A& M University

    2017-07-27

    Thermal interface materials (TIMs) are an integral and important part of thermal management in electronic devices. The electronic devices are becoming more compact and powerful. This increase in power processed or passing through the devices leads to higher heat fluxes and makes it a challenge to maintain temperatures at the optimal level during operation. Herein, we report a free standing nanocomposite TIM in which boron nitride nanosheets (BNNS) are uniformly dispersed in copper matrices via an organic linker, thiosemicarbazide. Integration of these metal-organic-inorganic nanocomposites was made possible by a novel electrodeposition technique where the functionalized BNNS (f-BNNS) experience the Brownian motion and reach the cathode through diffusion, while the nucleation and growth of the copper on the cathode occurs via the electrochemical reduction. Once the f-BNNS bearing carbonothioyl/thiol groups on the terminal edges come into the contact with copper crystals, the chemisorption reaction takes place. We performed thermal, mechanical, and structural characterization of these nanocomposites using scanning electron microcopy (SEM), diffusive laser flash (DLF) analysis, phase-sensitive transient thermoreflectence (PSTTR), and nanoindentation. The nanocomposites exhibited a thermal conductivity ranging from 211 W/mK to 277 W/mK at a filler mass loading of 0-12 wt.percent. The nanocomposites also have about 4 times lower hardness as compared to copper, with values ranging from 0.27 GPa to 0.41 GPa. The structural characterization studies showed that most of the BNNS are localized at grain boundaries - which enable efficient thermal transport while making the material soft. PSTTR measurements revealed that the synergistic combinations of these properties yielded contact resistances on the order of 0.10 to 0.13 mm2K/W, and the total thermal resistance of 0.38 to 0.56 mm2K/W at bondline thicknesses of 30-50 um. The coefficient of thermal expansion (CTE) of the

  19. Metallic Nanocomposites as Next-Generation Thermal Interface Materials: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Xuhui [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Narumanchi, Sreekant V [National Renewable Energy Laboratory (NREL), Golden, CO (United States); King, Charles C [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Nagabandi, Nirup [Texas A& M University; Oh, Jun K. [Texas A& M University; Akbulut, Mustafa [Texas A& M University; Yegin, Cengiz [Texas A& M University

    2017-09-14

    Thermal interface materials (TIMs) are an integral and important part of thermal management in electronic devices. The electronic devices are becoming more compact and powerful. This increase in power processed or passing through the devices leads to higher heat fluxes and makes it a challenge to maintain temperatures at the optimal level during operation. Herein, we report a free standing nanocomposite TIM in which boron nitride nanosheets (BNNS) are uniformly dispersed in copper matrices via an organic linker, thiosemicarbazide. Integration of these metal-organic-inorganic nanocomposites was made possible by a novel electrodeposition technique where the functionalized BNNS (f-BNNS) experience the Brownian motion and reach the cathode through diffusion, while the nucleation and growth of the copper on the cathode occurs via the electrochemical reduction. Once the f-BNNS bearing carbonothioyl/thiol groups on the terminal edges come into the contact with copper crystals, the chemisorption reaction takes place. We performed thermal, mechanical, and structural characterization of these nanocomposites using scanning electron microcopy (SEM), diffusive laser flash (DLF) analysis, phase-sensitive transient thermoreflectence (PSTTR), and nanoindentation. The nanocomposites exhibited a thermal conductivity ranging from 211 W/mK to 277 W/mK at a filler mass loading of 0-12 wt.percent. The nanocomposites also have about 4 times lower hardness as compared to copper, with values ranging from 0.27 GPa to 0.41 GPa. The structural characterization studies showed that most of the BNNS are localized at grain boundaries - which enable efficient thermal transport while making the material soft. PSTTR measurements revealed that the synergistic combinations of these properties yielded contact resistances on the order of 0.10 to 0.13 mm2K/W, and the total thermal resistance of 0.38 to 0.56 mm2K/W at bondline thicknesses of 30-50 um. The coefficient of thermal expansion (CTE) of the

  20. Adhesion and failure analysis of metal-polymer interface in flexible printed circuits boards

    Science.gov (United States)

    Park, Sanghee; Kim, Ye Chan; Choi, Kisuk; Chae, Heeyop; Suhr, Jonghwan; Nam, Jae-Do

    2017-12-01

    As device miniaturization in microelectronics is currently requested in the development of high performance device, which usually include highly-integrated metal-polyimide multilayer structures. A redistribution layer (RDL) process is currently emerging as one of the most advance fabrication techniques for on-chip interconnect and packaging. One of the major issues in this process is the poor adhesion of the metal-polyimide interfaces particularly in flexible circuit boards due to the flexibility and bendability of devices. In this study, low pressure O2 plasma treatment was investigated to improve the adhesion of metal-polyimide interfaces, using inductively coupled plasma (ICP) treatment. We identified that the adhesion of metal-polyimide interfaces was greatly improved by the surface roughness control providing 46.1 MPa of shear force in the ball shear test after O2 plasma treatment, compared 14.2 MPa without O2 plasma treatment. It was seemingly due to the fact that the adhesion in metal-polyimide interfaces was improved by a chemical conversion of C=O to C-O bonds and by a ring opening reaction of imide groups, which was confirmed with FT-IR analysis. In the finite element numerical analysis of metal-polyimide interfaces, the O2 plasma treated interface showed that the in-plane stress distribution and the vertical directional deformation agreed well with real failure modes in flexible circuits manufacturing.

  1. Method for converting uranium oxides to uranium metal

    International Nuclear Information System (INIS)

    Duerksen, W.K.

    1988-01-01

    A method for converting uranium oxide to uranium metal is described comprising the steps of heating uranium oxide in the presence of a reducing agent to a temperature sufficient to reduce the uranium oxide to uranium metal and form a heterogeneous mixture of a uranium metal product and oxide by-products, heating the mixture in a hydrogen atmosphere at a temperature sufficient to convert uranium metal in the mixture to uranium hydride, cooling the resulting uranium hydride-containing mixture to a temperature sufficient to produce a ferromagnetic transition in the uranium hydride, magnetically separating the cooled uranium hydride from the mixture, and thereafter heating the separated uranium hydride in an inert atmosphere to a temperature sufficient to convert the uranium hydride to uranium metal

  2. A dual enzyme functionalized nanostructured thulium oxide based interface for biomedical application

    Science.gov (United States)

    Singh, Jay; Roychoudhury, Appan; Srivastava, Manish; Solanki, Pratima R.; Lee, Dong Won; Lee, Seung Hee; Malhotra, B. D.

    2013-12-01

    In this paper, we present results of the studies related to fabrication of a rare earth metal oxide based efficient biosensor using an interface based on hydrothermally prepared nanostructured thulium oxide (n-Tm2O3). A colloidal solution of prepared nanorods has been electrophoretically deposited (EPD) onto an indium-tin-oxide (ITO) glass substrate. The n-Tm2O3 nanorods are found to provide improved sensing characteristics to the electrode interface in terms of electroactive surface area, diffusion coefficient, charge transfer rate constant and electron transfer kinetics. The structural and morphological studies of n-Tm2O3 nanorods have been carried out by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopic techniques. This interfacial platform has been used for fabrication of a total cholesterol biosensor by immobilizing cholesterol esterase (ChEt) and cholesterol oxidase (ChOx) onto a Tm2O3 nanostructured surface. The results of response studies of the fabricated ChEt-ChOx/n-Tm2O3/ITO bioelectrode show a broad linear range of 8-400 mg dL-1, detection limit of 19.78 mg (dL cm-2)-1, and high sensitivity of 0.9245 μA (mg per dL cm-2)-1 with a response time of 40 s. Further, this bioelectrode has been utilized for estimation of total cholesterol with negligible interference (3%) from analytes present in human serum samples. The utilization of this n-Tm2O3 modified electrode for enzyme-based biosensor analysis offers an efficient strategy and a novel interface for application of the rare earth metal oxide materials in the field of electrochemical sensors and bioelectronic devices.In this paper, we present results of the studies related to fabrication of a rare earth metal oxide based efficient biosensor using an interface based on hydrothermally prepared nanostructured thulium oxide (n-Tm2O3). A colloidal solution of prepared

  3. Synaptic plasticity and oscillation at zinc tin oxide/silver oxide interfaces

    Science.gov (United States)

    Murdoch, Billy J.; McCulloch, Dougal G.; Partridge, James G.

    2017-02-01

    Short-term plasticity, long-term potentiation, and pulse interval dependent plasticity learning/memory functions have been observed in junctions between amorphous zinc-tin-oxide and silver-oxide. The same junctions exhibited current-controlled negative differential resistance and when connected in an appropriate circuit, they behaved as relaxation oscillators. These oscillators produced voltage pulses suitable for device programming. Transmission electron microscopy, energy dispersive X-ray spectroscopy, and electrical measurements suggest that the characteristics of these junctions arise from Ag+/O- electromigration across a highly resistive interface layer. With memory/learning functions and programming spikes provided in a single device structure, arrays of similar devices could be used to form transistor-free neuromorphic circuits.

  4. Bulk oxide traps and border traps in metal endash oxide endash semiconductor capacitors

    International Nuclear Information System (INIS)

    Fleetwood, D.M.; Winokur, P.S.; Riewe, L.C.; Reber, R.A. Jr.

    1998-01-01

    Thermally stimulated current (TSC) and capacitance endash voltage measurements are combined via a newly developed analysis technique to estimate positive and negative oxide-trap charge densities for metal endash oxide endash semiconductor (MOS) capacitors exposed to ionizing radiation or subjected to high-field stress. Significantly greater hole trapping than electron trapping is observed in 3% borosilicate glass (BSG) insulators. Two prominent TSC peaks are observed in these BSG films. A high-temperature peak near 250 degree C is attributed to the E γ ' defect, which is a trivalent Si center in SiO 2 associated with an O vacancy. A lower temperature positive charge center near 100 degree C in these films is likely to be impurity related. The higher temperature E γ ' peak is also observed in 10, 17, and 98 nm thermal oxides. A much weaker secondary peak is observed near ∼60 degree C in some devices, which likely is due to metastably trapped holes in the bulk of the SiO 2 . Negative charge densities in these thermal oxides are primarily associated with electrons in border traps, which do not contribute to TSC, as opposed to bulk electron traps, which can contribute to TSC. Ratios of electron to hole trap densities in the thermal oxides range from ∼30% for radiation exposure to greater than 80% for high-field stress. It is suggested that the large densities of border traps associated with trapped holes in these devices may be due to high space-charge induced electric fields near the Si/SiO 2 interface. In some instances, border traps can reduce near-interfacial electric fields by local compensation of trapped positive charge. This may provide a natural explanation for the large densities of border traps often observed in irradiated or electrically stressed MOS capacitors. copyright 1998 American Institute of Physics

  5. Method and apparatus for the production of metal oxide powder

    Science.gov (United States)

    Harris, Michael T.; Scott, Timothy C.; Byers, Charles H.

    1992-01-01

    The present invention provides a method for preparing metal oxide powder. A first solution, which is substantially organic, is prepared. A second solution, which is an aqueous solution substantially immiscible in the first solution, is prepared and delivered as drops to the first solution. The drops of the second solution are atomized by a pulsed electric field forming micro-drops of the second solution. Reagents in the first solution diffuse into and react with reactants in the micro-drops of the second solution forming metal hydroxide or oxalate particles. The metal hydroxide or metal oxalate particles are then recovered and dried to produce the metal oxide powder. An apparatus for preparing a metal oxide powder is also disclosed.

  6. Photocatalysis of Modified Transition Metal Oxide Surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Batzill, Matthias

    2018-02-28

    The goal of this project has been to establish a cause-effect relationship for photocatalytic activity variations of different structures of the same material; and furthermore gain fundamental understanding on modification of photocatalysts by compositional or surface modifications. The reasoning is that gaining atomic scale understanding of how surface and bulk modifications alter the photo reactivity will lead to design principles for next generation photocatalysts. As a prototypical photocatalyst the research focused on TiO2 synthesized in well-defined single crystalline form to enable fundamental characterizations.We have obtained results in the following areas: (a) Preparation of epitaxial anataseTiO2 samples by pulsed laser deposition. (b) Comparison of hydrogen diffusion on different crystallographic surface. (c) Determining the stability of the TiO2(011)-2x1 reconstruction upon interactions with adsorbates. (d) Characterization of adsorption and (thermal and photo) reaction of molecules with nitro-endgroups, (e) Exploring the possibility of modifying planar model photocatalyst surfaces with graphene to enable fundamental studies on reported enhanced photocatalytic activities of graphene modified transition metal oxides, (f) gained fundamental understanding on the role of crystallographic polymorphs of the same material for their photocatalytic activities.

  7. Effect of CO on surface oxidation of uranium metal

    International Nuclear Information System (INIS)

    Wang, X.; Fu, Y.; Xie, R.

    1997-01-01

    The surface reactions of uranium metal with carbon monoxide at 25 and 200 deg C have been studied by X-ray photoelectron spectroscopy (XPS);respectively. Adsorption of carbon monoxide on the surface layer of uranium metal leads to partial reduction of surface oxide and results in U4f photoelectron peak shifting to the lower binding energy. The content of oxygen in the surface oxide is decreased and O1s/O4f ratio decreases with increasing the exposure of carbon monoxide. The investigation indicates the surface layer of uranium metal has resistance to further oxidation in the atmosphere of carbon monoxide. (author)

  8. Fabrication of Arrays of Metal and Metal Oxide Nanotubes by Shadow Evaporation

    NARCIS (Netherlands)

    Dickey, Michael D.; Weiss, Emily A.; Smythe, Elizabeth J.; Chiechi, Ryan C.; Capasso, Federico; Whitesides, George M.

    2008-01-01

    This paper describes a simple technique for fabricating uniform arrays of metal and metal oxide nanotubes with controlled heights and diameters. The technique involves depositing material onto an anodized aluminum oxide (AAO) membrane template using a collimated electron beam evaporation source. The

  9. Bubble separation at the interface between a liquid metal and a liquid slag

    Science.gov (United States)

    Chevrier, Vincent F.

    Due to more specific consumer demand, most steel manufacturers are developing techniques to produce quality steels by limiting the number of defects in the final product. There are several aspects to be considered when producing "clean steels", and this research project will focus on one of them: inclusion and bubble separation. Large inclusions (solid or liquid) and gas bubbles have to be removed from the liquid metal before casting, and separation occurs mostly at the slag-metal interface. The objective of this study to develop a fundamental understanding of bubble separation at the slag-metal interface by looking at the chemical engineering literature on separation and coalescence, and by studying experimentally bubble separation at a liquid-liquid interface, first using a water-oil system and then with a metal-slag system. The literature review and the water modeling experiments have shown that four separate steps need to be considered when studying the removal of a buoyant phase particle at a liquid-liquid interface: the transport to the interface, the separation at the interface (film drainage), the film rupture and the removal from the interface. The major factors influencing the rest-time of an argon bubble at an oil-water interface are determined experimentally. The high temperature apparatus permits direct visualization of bubble behavior in metal and slag. The separation of argon bubbles at the slag-metal interface exhibits a behavior similar to what is observed in water modeling: the bubbles impact the interface and rest there for some time before coalescing. A methodology of studying the separation of solid and liquid inclusions is also established using two complementary techniques: x-ray fluoroscopy and confocal scanning electron microscopy. This experimental study showed that inclusions and bubbles do not separate immediately upon reaching the slag-metal interface but can rest in the metal phase for long periods of time before separating. Enhancing

  10. Systematic study of metal-insulator-metal diodes with a native oxide

    KAUST Repository

    Donchev, E.

    2014-10-07

    © 2014 SPIE. In this paper, a systematic analysis of native oxides within a Metal-Insulator-Metal (MIM) diode is carried out, with the goal of determining their practicality for incorporation into a nanoscale Rectenna (Rectifying Antenna). The requirement of having a sub-10nm oxide scale is met by using the native oxide, which forms on most metals exposed to an oxygen containing environment. This, therefore, provides a simplified MIM fabrication process as the complex, controlled oxide deposition step is omitted. We shall present the results of an investigation into the current-voltage characteristics of various MIM combinations that incorporate a native oxide, in order to establish whether the native oxide is of sufficient quality for good diode operation. The thin native oxide layers are formed by room temperature oxidation of the first metal layer, deposited by magnetron sputtering. This is done in-situ, within the deposition chamber before depositing the second metal electrode. Using these structures, we study the established trend where the bigger the difference in metal workfunctions, the better the rectification properties of MIM structures, and hence the selection of the second metal is key to controlling the device\\'s rectifying properties. We show how leakage current paths through the non-optimised native oxide control the net current-voltage response of the MIM devices. Furthermore, we will present the so-called diode figures of merit (asymmetry, non-linearity and responsivity) for each of the best performing structures.

  11. Metal-core@metal oxide-shell nanomaterials for gas-sensing applications: a review

    International Nuclear Information System (INIS)

    Mirzaei, A.; Janghorban, K.; Hashemi, B.; Neri, G.

    2015-01-01

    With an ever-increasing number of applications in many advanced fields, gas sensors are becoming indispensable devices in our daily life. Among different types of gas sensors, conductometric metal oxide semiconductor (MOS) gas sensors are found to be the most appealing for advanced applications in the automotive, biomedical, environmental, and safety sectors because of the their high sensitivity, reduced size, and low cost. To improve their sensing characteristics, new metal oxide-based nanostructures have thus been proposed in recent years as sensing materials. In this review, we extensively review gas-sensing properties of core@ shell nanocomposites in which metals as the core and metal oxides as the shell structure, both of nanometer sizes, are assembled into a single metal@metal oxide core–shell. These nanostructures not only combine the properties of both noble metals and metal oxides, but also bring unique synergetic functions in comparison with single-component materials. Up-dated achievements in the synthesis and characterization of metal@metal oxide core–shell nanostructures as well as their use in MOS sensors are here reported with the main objective of providing an overview about their gas-sensing properties

  12. Metal-core@metal oxide-shell nanomaterials for gas-sensing applications: a review

    Science.gov (United States)

    Mirzaei, A.; Janghorban, K.; Hashemi, B.; Neri, G.

    2015-09-01

    With an ever-increasing number of applications in many advanced fields, gas sensors are becoming indispensable devices in our daily life. Among different types of gas sensors, conductometric metal oxide semiconductor (MOS) gas sensors are found to be the most appealing for advanced applications in the automotive, biomedical, environmental, and safety sectors because of the their high sensitivity, reduced size, and low cost. To improve their sensing characteristics, new metal oxide-based nanostructures have thus been proposed in recent years as sensing materials. In this review, we extensively review gas-sensing properties of core@ shell nanocomposites in which metals as the core and metal oxides as the shell structure, both of nanometer sizes, are assembled into a single metal@metal oxide core-shell. These nanostructures not only combine the properties of both noble metals and metal oxides, but also bring unique synergetic functions in comparison with single-component materials. Up-dated achievements in the synthesis and characterization of metal@metal oxide core-shell nanostructures as well as their use in MOS sensors are here reported with the main objective of providing an overview about their gas-sensing properties.

  13. Effect of weak metallic contamination on silicon epitaxial layer and gate oxide integrity

    Energy Technology Data Exchange (ETDEWEB)

    Mello, D.; Coccorese, C.; Ferlito, E.; Sciuto, G.; Ricciari, R.; Barbarino, P.; Astuto, M. [STMicroelectronics, Physics Lab. Stradale primosole, 50 I-95121 Catania (Italy)

    2011-08-15

    The detection of metallic contaminants in microelectronics devices is one of the main issues in production line. In fact they could diffuse rapidly into the silicon bulk and establishing energy states into the silicon energy-band gap. The presence of trace of metals on the silicon surface can also degrade the gate oxide integrity, cause structural defect in silicon epitaxial layers or anomalies in silicon/gate oxide interface. Usually in semiconductor manufacturing superficial metallic contamination is monitored using Total X-ray Reflection Fluorescence spectroscopy (TXRF) and performing specific electrical measurements on dedicated capacitor. In this work a weak contamination, undetected by TXRF analysis, was revealed by Transmission Electron Microscopy (TEM) observing lattice damaging and Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS) detecting an anomalous Na distribution in depth profile. (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  14. Effect of high-energy electrons on the interface states of thin oxides MOS structures

    CERN Document Server

    Kaschieva, S

    2002-01-01

    The influence of high-energy electron irradiation on thermal simulated current (TSC) characteristics of n-type MOS structures with different oxide thickness has been investigated. Three groups of MOS samples with oxide thickness of 9, 28 and 56 nm are irradiated with 12 MeV electrons. It is shown that the interface traps in silicon band gap created by electron irradiation depend on the oxide thickness of the samples. The electron irradiation introduces only two kinds of defects in the structures with ultrathin oxide thickness (9 nm) at the Si-SiO sub 2 interface, while in the samples with thicker oxides (28 and 56 nm), it generates four kinds of defects. The total concentration of radiation induces defects at the Si-SiO sub 2 interface also depends on the oxide thickness of the samples

  15. A general approach to mesoporous metal oxide microspheres loaded with noble metal nanoparticles

    KAUST Repository

    Jin, Zhao

    2012-04-26

    Catalytic microspheres: A general approach is demonstrated for the facile preparation of mesoporous metal oxide microspheres loaded with noble metal nanoparticles (see TEM image in the picture). Among 18 oxide/noble metal catalysts, TiO 2/0.1 mol Pd microspheres showed the highest turnover frequency in NaBH 4 reduction of 4-nitrophenol (see picture). Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Tin etching from metallic and oxidized scandium thin films

    Directory of Open Access Journals (Sweden)

    M. Pachecka

    2017-08-01

    Full Text Available The role of oxide on Sn adhesion to Sc surfaces was studied with in-situ ellipsometry, X-ray photoelectron spectroscopy and secondary electron microscopy. Sn etching with hydrogen radicals was performed on metallic Sc, metallic Sc with a native oxide, and a fully oxidized Sc layer. The results show that Sn adsorbs rather weakly to a non-oxidized Sc surface, and is etched relatively easily by atomic hydrogen. In contrast, the presence of native oxide on Sc allows Sn to adsorb more strongly to the surface, slowing the etching. Furthermore, thinner layers of scandium oxide result in weaker Sn adsorption, indicating that the layer beneath the oxide plays a significant role in determining the adsorption strength. Unexpectedly, for Sn on Sc2O3, and, to a lesser extent, for Sn on Sc, the etch rate shows a variation over time, which is explained by surface restructuring, temperature change, and hydrogen adsorption saturation.

  17. Study of the tunnelling initiated leakage current through the carbon nanotube embedded gate oxide in metal oxide semiconductor structures

    International Nuclear Information System (INIS)

    Chakraborty, Gargi; Sarkar, C K; Lu, X B; Dai, J Y

    2008-01-01

    The tunnelling currents through the gate dielectric partly embedded with semiconducting single-wall carbon nanotubes in a silicon metal-oxide-semiconductor (MOS) structure have been investigated. The application of the gate voltage to such an MOS device results in the band bending at the interface of the partly embedded oxide dielectric and the surface of the silicon, initiating tunnelling through the gate oxide responsible for the gate leakage current whenever the thickness of the oxide is scaled. A model for silicon MOS structures, where carbon nanotubes are confined in a narrow layer embedded in the gate dielectric, is proposed to investigate the direct and the Fowler-Nordheim (FN) tunnelling currents of such systems. The idea of embedding such elements in the gate oxide is to assess the possibility for charge storage for memory device applications. Comparing the FN tunnelling onset voltage between the pure gate oxide and the gate oxide embedded with carbon nanotubes, it is found that the onset voltage decreases with the introduction of the nanotubes. The direct tunnelling current has also been studied at very low gate bias, for the thin oxide MOS structure which plays an important role in scaling down the MOS transistors. The FN tunnelling current has also been studied with varying nanotube diameter

  18. Study of the tunnelling initiated leakage current through the carbon nanotube embedded gate oxide in metal oxide semiconductor structures.

    Science.gov (United States)

    Chakraborty, Gargi; Sarkar, C K; Lu, X B; Dai, J Y

    2008-06-25

    The tunnelling currents through the gate dielectric partly embedded with semiconducting single-wall carbon nanotubes in a silicon metal-oxide-semiconductor (MOS) structure have been investigated. The application of the gate voltage to such an MOS device results in the band bending at the interface of the partly embedded oxide dielectric and the surface of the silicon, initiating tunnelling through the gate oxide responsible for the gate leakage current whenever the thickness of the oxide is scaled. A model for silicon MOS structures, where carbon nanotubes are confined in a narrow layer embedded in the gate dielectric, is proposed to investigate the direct and the Fowler-Nordheim (FN) tunnelling currents of such systems. The idea of embedding such elements in the gate oxide is to assess the possibility for charge storage for memory device applications. Comparing the FN tunnelling onset voltage between the pure gate oxide and the gate oxide embedded with carbon nanotubes, it is found that the onset voltage decreases with the introduction of the nanotubes. The direct tunnelling current has also been studied at very low gate bias, for the thin oxide MOS structure which plays an important role in scaling down the MOS transistors. The FN tunnelling current has also been studied with varying nanotube diameter.

  19. Displacement method and apparatus for reducing passivated metal powders and metal oxides

    Science.gov (United States)

    Morrell,; Jonathan S. , Ripley; Edward, B [Knoxville, TN

    2009-05-05

    A method of reducing target metal oxides and passivated metals to their metallic state. A reduction reaction is used, often combined with a flux agent to enhance separation of the reaction products. Thermal energy in the form of conventional furnace, infrared, or microwave heating may be applied in combination with the reduction reaction.

  20. Aging of trivalent metal hydroxide/oxide gels in divalent metal salt ...

    Indian Academy of Sciences (India)

    Unknown

    Aging of trivalent metal hydroxide/oxide gels in divalent metal salt solutions: Mechanism of formation of layered double hydroxides (LDHs). A V RADHA and P ..... This situation promotes coprecipitation of the two metal hydroxides, by virtue of which the titrations yield the. Zn–Al LDH. The LDHs isolated before and after ...

  1. Fabrication and characterization of metal oxide nanowire sensors.

    Science.gov (United States)

    Shen, Guozhen

    2008-01-01

    Trace detection of chemicals and biological species like industrial gases, proteins, drug molecules, and chemical warfare agents, is an important issue to human health and safety. Central to this issue is the development of high sensitivity, high selectivity, high stability and rapid detection chemical and bio-sensors. With special geometry and chemical and physical properties, one-dimensional (1-D) metal oxide nanostructures have become the promising candidates for chemical and biosensing applications in recent years. Here, we intend to provide an overview on this interesting and important field. In the first part, the patents for rational synthesis of 1-D metal oxide nanostructures on a large scale will be introduced. The patents on chemical and biosensors built on 1-D metal oxide nanostructures are then introduced in the second part. Finally, we provide a review of the recent development of electronic nose systems using 1-D metal oxide nanostructures, which show great potential for the improvement of sensing abilities.

  2. Plutonium metal and oxide container weld development and qualification

    International Nuclear Information System (INIS)

    Fernandez, R.; Horrell, D.R.; Hoth, C.W.; Pierce, S.W.; Rink, N.A.; Rivera, Y.M.; Sandoval, V.D.

    1996-01-01

    Welds were qualified for a container system to be used for long-term storage of plutonium metal and oxide. Inner and outer containers are formed of standard tubing with stamped end pieces gas-tungsten-arc (GTA) welded onto both ends. The weld qualification identified GTA parameters to produce a robust weld that meets the requirements of the Department of Energy standard DOE-STD-3013-94, ''Criteria for the Safe Storage of Plutonium Metals and Oxides.''

  3. Heavy metal removal from water/wastewater by nanosized metal oxides: a review.

    Science.gov (United States)

    Hua, Ming; Zhang, Shujuan; Pan, Bingcai; Zhang, Weiming; Lv, Lu; Zhang, Quanxing

    2012-04-15

    Nanosized metal oxides (NMOs), including nanosized ferric oxides, manganese oxides, aluminum oxides, titanium oxides, magnesium oxides and cerium oxides, provide high surface area and specific affinity for heavy metal adsorption from aqueous systems. To date, it has become a hot topic to develop new technologies to synthesize NMOs, to evaluate their removal of heavy metals under varying experimental conditions, to reveal the underlying mechanism responsible for metal removal based on modern analytical techniques (XAS, ATR-FT-IR, NMR, etc.) or mathematical models, and to develop metal oxide-based materials of better applicability for practical use (such as granular oxides or composite materials). The present review mainly focuses on NMOs' preparation, their physicochemical properties, adsorption characteristics and mechanism, as well as their application in heavy metal removal. In addition, porous host supported NMOs are particularly concerned because of their great advantages for practical application as compared to the original NMOs. Also, some magnetic NMOs were included due to their unique separation performance. Copyright © 2011 Elsevier B.V. All rights reserved.

  4. Process for Making a Noble Metal on Tin Oxide Catalyst

    Science.gov (United States)

    Davis, Patricia; Miller, Irvin; Upchurch, Billy

    2010-01-01

    To produce a noble metal-on-metal oxide catalyst on an inert, high-surface-area support material (that functions as a catalyst at approximately room temperature using chloride-free reagents), for use in a carbon dioxide laser, requires two steps: First, a commercially available, inert, high-surface-area support material (silica spheres) is coated with a thin layer of metal oxide, a monolayer equivalent. Very beneficial results have been obtained using nitric acid as an oxidizing agent because it leaves no residue. It is also helpful if the spheres are first deaerated by boiling in water to allow the entire surface to be coated. A metal, such as tin, is then dissolved in the oxidizing agent/support material mixture to yield, in the case of tin, metastannic acid. Although tin has proven especially beneficial for use in a closed-cycle CO2 laser, in general any metal with two valence states, such as most transition metals and antimony, may be used. The metastannic acid will be adsorbed onto the high-surface-area spheres, coating them. Any excess oxidizing agent is then evaporated, and the resulting metastannic acid-coated spheres are dried and calcined, whereby the metastannic acid becomes tin(IV) oxide. The second step is accomplished by preparing an aqueous mixture of the tin(IV) oxide-coated spheres, and a soluble, chloride-free salt of at least one catalyst metal. The catalyst metal may be selected from the group consisting of platinum, palladium, ruthenium, gold, and rhodium, or other platinum group metals. Extremely beneficial results have been obtained using chloride-free salts of platinum, palladium, or a combination thereof, such as tetraammineplatinum (II) hydroxide ([Pt(NH3)4] (OH)2), or tetraammine palladium nitrate ([Pd(NH3)4](NO3)2).

  5. Metallization of uranium oxide powders by lithium reduction

    International Nuclear Information System (INIS)

    Kim, I. S.; Seo, J. S.; Oh, S. C.; Hong, S. S.; Lee, W. K.

    2002-01-01

    Laboratory scale experiments on the reduction of uranium oxide powders into metal by lithium were performed in order to determine the equipment setup and optimum operation conditions. The method of filtration using the porous magnesia filter was introduced to recover uranium metal powders produced. Based on the laboratory scale experimental results, mock-up scale (20 kg U/batch) metallizer was designed and made. The applicability to the metallization process was estimated with respect to the thermal stability of the porous magnesia filter in the high temperature molten salt, the filtration of the fine uranium metal powders, and the operability of the equipment

  6. Photodegradation of phenanthrene on metal oxides and fly ashes

    Energy Technology Data Exchange (ETDEWEB)

    Guesten, H.; Bozicevic, Z.; Klasinc, L.

    1984-10-01

    The photodegradation of phenanthrene adsorbed on the surface of metal oxides, sea sand and fly ashes is investigated in a rotating bed photoreactor emitting simulated solar light. Metal oxides (SiO/sub 2/, Al/sub 2/O/sub 3/, SnO/sub 2/, MgO), which do not absorb the simulated solar light, give rise to a very slow photodegradation of the adsorbed phenanthrene. Metal oxides (TiO/sub 2/, ZnO, Fe/sub 2/O/sub 3/), which exhibit semiconduction properties, induce a very rapid photodegradation. The two modifications of TiO/sub 2/, rutile and anatase, show different activities in causing the photodegradation of phenanthrene. While in the class of non-solar light absorbing metal oxides the adsorbed phenanthrene is degraded only by direct excitation to its electronic states, photons of band-gap energy in semiconducting metal oxides excite electron-hole pairs at the surface. The quantum yield of the photodegradation of phenanthrene adsorbed on a fly ash of the mullite-quartz of glass type lies between the quantum yields of the two classes of metal oxides investigated. Surprisingly, however, phenanthrene and the very photolabile anthracene are extremely resistant to photodegradation when adsorbed on a fly ash of the spinel type with pig iron content and magnetic properties.

  7. Meso-/Nanoporous Semiconducting Metal Oxides for Gas Sensor Applications

    Directory of Open Access Journals (Sweden)

    Nguyen Duc Hoa

    2015-01-01

    Full Text Available Development and/or design of new materials and/or structures for effective gas sensor applications with fast response and high sensitivity, selectivity, and stability are very important issues in the gas sensor technology. This critical review introduces our recent progress in the development of meso-/nanoporous semiconducting metal oxides and their applications to gas sensors. First, the basic concepts of resistive gas sensors and the recent synthesis of meso-/nanoporous metal oxides for gas sensor applications are introduced. The advantages of meso-/nanoporous metal oxides are also presented, taking into account the crystallinity and ordered/disordered porous structures. Second, the synthesis methods of meso-/nanoporous metal oxides including the soft-template, hard-template, and temple-free methods are introduced, in which the advantages and disadvantages of each synthetic method are figured out. Third, the applications of meso-/nanoporous metal oxides as gas sensors are presented. The gas nanosensors are designed based on meso-/nanoporous metal oxides for effective detection of toxic gases. The sensitivity, selectivity, and stability of the meso-/nanoporous gas nanosensors are also discussed. Finally, some conclusions and an outlook are presented.

  8. Oxide-supported metal clusters: models for heterogeneous catalysts

    International Nuclear Information System (INIS)

    Santra, A K; Goodman, D W

    2003-01-01

    Understanding the size-dependent electronic, structural and chemical properties of metal clusters on oxide supports is an important aspect of heterogeneous catalysis. Recently model oxide-supported metal catalysts have been prepared by vapour deposition of catalytically relevant metals onto ultra-thin oxide films grown on a refractory metal substrate. Reactivity and spectroscopic/microscopic studies have shown that these ultra-thin oxide films are excellent models for the corresponding bulk oxides, yet are sufficiently electrically conductive for use with various modern surface probes including scanning tunnelling microscopy (STM). Measurements on metal clusters have revealed a metal to nonmetal transition as well as changes in the crystal and electronic structures (including lattice parameters, band width, band splitting and core-level binding energy shifts) as a function of cluster size. Size-dependent catalytic reactivity studies have been carried out for several important reactions, and time-dependent catalytic deactivation has been shown to arise from sintering of metal particles under elevated gas pressures and/or reactor temperatures. In situ STM methodologies have been developed to follow the growth and sintering kinetics on a cluster-by-cluster basis. Although several critical issues have been addressed by several groups worldwide, much more remains to be done. This article highlights some of these accomplishments and summarizes the challenges that lie ahead. (topical review)

  9. METAL-CERAMIC INTERFACES PRODUCED BY LASER MELT INJECTION PROCESSING

    NARCIS (Netherlands)

    DEHOSSON, JTM; VANDENBURG, M; Burg, M. van den

    1995-01-01

    This paper concentrates on the mechanical performance of various ceramic coatings of Cr2O3 on steel (SAF2205), as produced by CO2 laser processing. It is concluded that a firmly bonded coating of Cr2O3 on steel could be produced by high power laser processing. The actual interface strength of a

  10. Photoinduced electron transfer from semiconductor quantum dots to metal oxide nanoparticles.

    Science.gov (United States)

    Tvrdy, Kevin; Frantsuzov, Pavel A; Kamat, Prashant V

    2011-01-04

    Quantum dot-metal oxide junctions are an integral part of next-generation solar cells, light emitting diodes, and nanostructured electronic arrays. Here we present a comprehensive examination of electron transfer at these junctions, using a series of CdSe quantum dot donors (sizes 2.8, 3.3, 4.0, and 4.2 nm in diameter) and metal oxide nanoparticle acceptors (SnO(2), TiO(2), and ZnO). Apparent electron transfer rate constants showed strong dependence on change in system free energy, exhibiting a sharp rise at small driving forces followed by a modest rise further away from the characteristic reorganization energy. The observed trend mimics the predicted behavior of electron transfer from a single quantum state to a continuum of electron accepting states, such as those present in the conduction band of a metal oxide nanoparticle. In contrast with dye-sensitized metal oxide electron transfer studies, our systems did not exhibit unthermalized hot-electron injection due to relatively large ratios of electron cooling rate to electron transfer rate. To investigate the implications of these findings in photovoltaic cells, quantum dot-metal oxide working electrodes were constructed in an identical fashion to the films used for the electron transfer portion of the study. Interestingly, the films which exhibited the fastest electron transfer rates (SnO(2)) were not the same as those which showed the highest photocurrent (TiO(2)). These findings suggest that, in addition to electron transfer at the quantum dot-metal oxide interface, other electron transfer reactions play key roles in the determination of overall device efficiency.

  11. Thermal oxidation and electrical properties of silicon carbide metal-oxide-semiconductor structures

    Science.gov (United States)

    Singh, N.; Rys, A.

    1993-02-01

    The fabrication of metal-oxide-semiconductor (MOS) capacitors on n-type, Si-face 6H-SiC is described for both wet and dry oxidation processes, and the effect of thermal oxidation conditions on the electrical properties of MOS capacitors are investigated. The values of the oxide thickness were obtained as a function of the oxidation time at various oxidation temperatures (which were kept between 1150 and 1250 C). It was found that samples prepared by both dry and wet oxidation showed accumulation, depletion, and inversion regions under illumination, while inversion did not occur under dark conditions. The C-V characteristics of oxidized samples were improved after the oxidized samples were annealed in argon for 30 min. The relation between the oxide thickness and the oxidation time could be expressed by parabolic law, which is also used for thermal oxidation of Si.

  12. Electrochemical activity of heavy metal oxides in the process of ...

    Indian Academy of Sciences (India)

    Unknown

    2002-02-02

    Feb 2, 2002 ... Abstract. The influence of heavy metal oxides on the chloride induced corrosion of steel reinforcement in concrete was studied. Significant inhibition and stimulation of chloride induced corrosion have been observed. Basicity and acidity of the relevant metal ions, and their ability to form complexes are ...

  13. Electrochemical activity of heavy metal oxides in the process of ...

    Indian Academy of Sciences (India)

    Unknown

    2002-02-02

    Feb 2, 2002 ... The influence of heavy metal oxides on the chloride induced corrosion of steel reinforcement in concrete was studied. ... Basicity and acidity of the relevant metal ions, and their ability to form complexes are considered as the main factors of the .... niobium, tantalum, protactinium, and uranium. However,.

  14. Back to the metal age: battle for metals at the host-pathogen interface during urinary tract infection.

    Science.gov (United States)

    Subashchandrabose, Sargurunathan; Mobley, Harry L T

    2015-06-01

    Urinary tract infection (UTI) represents one of the most common bacterial infections in humans and uropathogenic E. coli (UPEC) is the major causative agent of UTI in people. Research on UPEC and other bacterial pathogens causing UTI has now identified the critical role of metal transport systems in the pathogenesis of UTI. Here we review the major effectors of metal transport in bacteria and host proteins that impair metal acquisition by bacterial pathogens. In particular, we describe the studies that identified iron, zinc and nickel import and copper export as key virulence and fitness determinants during UTI. Various metal transport systems and mechanisms that govern the expression of metal transport systems are also presented here. Specific examples from UPEC and other uropathogens, when available, are presented to depict the battle for metals at the host-pathogen interface during UTI.

  15. Preparation of novel polymer–metal oxide nanocomposites with ...

    Indian Academy of Sciences (India)

    Administrator

    Abstract. This article deals with preparation of nanocomposite which comprised of nanophase separated structure of polymer chains and metal oxide. By grafting poly(hydroxyethyl methacrylate), poly(HEMA) on the surface of titanium which is covered by passive titanium oxide by atom transfer radical polymerization.

  16. Advancing metal-oxide-semiconductor theory: Steady-state nonequilibrium conditions

    Science.gov (United States)

    Passlack, M.; Hong, M.; Schubert, E. F.; Zydzik, G. J.; Mannaerts, J. P.; Hobson, W. S.; Harris, T. D.

    1997-06-01

    This article investigates steady-state nonequilibrium conditions in metal-oxide-semiconductor (MOS) capacitors. Steady-state nonequilibrium conditions are of significant interest due to the advent of wide-gap semiconductors in the arena of MOS (or metal-insulator-semiconductor) devices and due to the scaling of oxide thickness in Si technology. Two major classes of steady-state nonequilibrium conditions were studied both experimentally and theoretically: (i) steady-state deep depletion and (ii) steady-state low level optical generation. It is found that the identification and subsequent understanding of steady-state nonequilibrium conditions is of significant importance for correct interpretation of electrical measurements such as capacitance-voltage and conductance-voltage measurements. Basic implications of steady-state nonequilibrium conditions were derived for both MOS capacitors with low interfaces state density Dit and for oxide semiconductor interfaces with a pinned Fermi level. Further, a photoluminescence power spectroscopy technique is investigated as a complementary tool for direct-gap semiconductors to study Dit and to monitor the interface quality during device fabrication.

  17. Corrosion at the Polymer-Metal Interface in Artificial Seawater Solutions

    Directory of Open Access Journals (Sweden)

    Amelia M. Anderson-Wile

    2012-01-01

    Full Text Available Polymer components for liquid sealing applications are employed in a variety of potentially corrosive environments, such as seawater. Frequently, corrosion of the metal is found at or adjacent to the rubber-metal interface rather than at a noncontact area. The corrosion of different metal alloys (titanium, bronze, nickel, aluminum, 316 stainless steel, and 4130 steel in combination with rubber O-rings (Buna-N and EPDM of varying internal diameters and cross-sectional shapes in seawater over a period of four years is described herein. The corrosion of some metals (i.e., 4130 stainless steel was found to be accelerated through interaction with Buna-N rubber O-rings. Theories to account for corrosion at the polymer-metal interface, especially with respect to polymer composition and O-ring size and shape, are discussed.

  18. Charge transport in metal oxide nanocrystal-based materials

    Science.gov (United States)

    Runnerstrom, Evan Lars

    There is probably no class of materials more varied, more widely used, or more ubiquitous than metal oxides. Depending on their composition, metal oxides can exhibit almost any number of properties. Of particular interest are the ways in which charge is transported in metal oxides: devices such as displays, touch screens, and smart windows rely on the ability of certain metal oxides to conduct electricity while maintaining visible transparency. Smart windows, fuel cells, and other electrochemical devices additionally rely on efficient transport of ionic charge in and around metal oxides. Colloidal synthesis has enabled metal oxide nanocrystals to emerge as a relatively new but highly tunable class of materials. Certain metal oxide nanocrystals, particularly highly doped metal oxides, have been enjoying rapid development in the last decade. As in myriad other materials systems, structure dictates the properties of metal oxide nanocrystals, but a full understanding of how nanocrystal synthesis, the processing of nanocrystal-based materials, and the structure of nanocrystals relate to the resulting properties of nanocrystal-based materials is still nascent. Gaining a fundamental understanding of and control over these structure-property relationships is crucial to developing a holistic understanding of metal oxide nanocrystals. The unique ability to tune metal oxide nanocrystals by changing composition through the introduction of dopants or by changing size and shape affords a way to study the interplay between structure, processing, and properties. This overall goal of this work is to chemically synthesize colloidal metal oxide nanocrystals, process them into useful materials, characterize charge transport in materials based on colloidal metal oxide nanocrystals, and develop ways to manipulate charge transport. In particular, this dissertation characterizes how the charge transport properties of metal oxide nanocrystal-based materials depend on their processing and

  19. Study of the interface stability of the metal (Mo, Ni, Pd/HfO2/AlN/InGaAs MOS devices

    Directory of Open Access Journals (Sweden)

    Huy Binh Do

    2017-08-01

    Full Text Available The degeneration of the metal/HfO2 interfaces for Mo, Ni, and Pd gate metals was studied in this paper. An unstable PdOx interfacial layer formed at the Pd/HfO2 interface, inducing the oxygen segregation for the Pd/HfO2/InGaAs metal oxide capacitor (MOSCAP. The low dissociation energy for the Pd-O bond was the reason for oxygen segregation. The PdOx layer contains O2− and OH− ions which are mobile during thermal annealing and electrical stress test. The phenomenon was not observed for the (Mo, Ni/HfO2/InGaAs MOSCAPs. The results provide the guidance for choosing the proper metal electrode for the InGaAs based MOSFET.

  20. Heterogeneous Partial (ammOxidation and Oxidative Dehydrogenation Catalysis on Mixed Metal Oxides

    Directory of Open Access Journals (Sweden)

    Jacques C. Védrine

    2016-01-01

    Full Text Available This paper presents an overview of heterogeneous partial (ammoxidation and oxidative dehydrogenation (ODH of hydrocarbons. The review has been voluntarily restricted to metal oxide-type catalysts, as the partial oxidation field is very broad and the number of catalysts is quite high. The main factors of solid catalysts for such reactions, designated by Grasselli as the “seven pillars”, and playing a determining role in catalytic properties, are considered to be, namely: isolation of active sites (known to be composed of ensembles of atoms, Me–O bond strength, crystalline structure, redox features, phase cooperation, multi-functionality and the nature of the surface oxygen species. Other important features and physical and chemical properties of solid catalysts, more or less related to the seven pillars, are also emphasized, including reaction sensitivity to metal oxide structure, epitaxial contact between an active phase and a second phase or its support, synergy effect between several phases, acid-base aspects, electron transfer ability, catalyst preparation and activation and reaction atmospheres, etc. Some examples are presented to illustrate the importance of these key factors. They include light alkanes (C1–C4 oxidation, ethane oxidation to ethylene and acetic acid on MoVTe(SbNb-O and Nb doped NiO, propene oxidation to acrolein on BiMoCoFe-O systems, propane (ammoxidation to (acrylonitrile acrylic acid on MoVTe(SbNb-O mixed oxides, butane oxidation to maleic anhydride on VPO: (VO2P2O7-based catalyst, and isobutyric acid ODH to methacrylic acid on Fe hydroxyl phosphates. It is shown that active sites are composed of ensembles of atoms whose size and chemical composition depend on the reactants to be transformed (their chemical and size features and the reaction mechanism, often of Mars and van Krevelen type. An important aspect is the fact that surface composition and surface crystalline structure vary with reaction on stream until

  1. Interface Enthalpy-Entropy Competition in Nanoscale Metal Hydrides

    Directory of Open Access Journals (Sweden)

    Nicola Patelli

    2018-01-01

    Full Text Available We analyzed the effect of the interfacial free energy on the thermodynamics of hydrogen sorption in nano-scaled materials. When the enthalpy and entropy terms are the same for all interfaces, as in an isotropic bi-phasic system, one obtains a compensation temperature, which does not depend on the system size nor on the relative phase abundance. The situation is different and more complex in a system with three or more phases, where the interfaces have different enthalpy and entropy. We also consider the possible effect of elastic strains on the stability of the hydride phase and on hysteresis. We compare a simple model with experimental data obtained on two different systems: (1 bi-phasic nanocomposites where ultrafine TiH2 crystallite are dispersed within a Mg nanoparticle and (2 Mg nanodots encapsulated by different phases.

  2. Trends in Metal Oxide Stability for Nanorods, Nanotubes, and Surfaces

    DEFF Research Database (Denmark)

    Mowbray, Duncan; Martinez, Jose Ignacio; Vallejo, Federico Calle

    2011-01-01

    ,2) nanorods, (3,3) nanotubes, and the (110) and (100) surfaces. These formation energies can be described semiquantitatively (mean absolute error ≈ 0.12 eV) by the fraction of metal−oxygen bonds broken and the metal d-band and p-band centers in the bulk metal oxide.......The formation energies of nanostructures play an important role in determining their properties, including their catalytic activity. For the case of 15 different rutile and 8 different perovskite metal oxides, we used density functional theory (DFT) to calculate the formation energies of (2...

  3. Nanostructured Metal Oxides for Stoichiometric Degradation of Chemical Warfare Agents.

    Science.gov (United States)

    Štengl, Václav; Henych, Jiří; Janoš, Pavel; Skoumal, Miroslav

    2016-01-01

    Metal oxides have very important applications in many areas of chemistry, physics and materials science; their properties are dependent on the method of preparation, the morphology and texture. Nanostructured metal oxides can exhibit unique characteristics unlike those of the bulk form depending on their morphology, with a high density of edges, corners and defect surfaces. In recent years, methods have been developed for the preparation of metal oxide powders with tunable control of the primary particle size as well as of a secondary particle size: the size of agglomerates of crystallites. One of the many ways to take advantage of unique properties of nanostructured oxide materials is stoichiometric degradation of chemical warfare agents (CWAs) and volatile organic compounds (VOC) pollutants on their surfaces.

  4. Ordering phenomena in transition-metal-oxide heterostructures

    International Nuclear Information System (INIS)

    Frano Pereira, Alex Manuel

    2014-01-01

    wave (CDW) order in single crystals of superconducting YBa 2 Cu 3 O 6+δ (YBCO). With accumulating evidence of a Fermi surface reconstruction suggesting an underlying ordered ground state in underdoped YBCO, diffraction evidence of a CDW was found in YBCO 6.6 single crystals during this PhD project. A thorough study of the energy, temperature, external magnetic field, and doping dependence was done to characterize the details of this ordered state. Together with results obtained on samples doped with non-magnetic Zn impurities, which locally slow the magnetic fluctuations, a competition between the CDW, the spin density wave, and superconducting phase is proposed. Finally, the study extended to investigate the emergence of CDW in SLs comprising fully oxygenated YBCO, a doping level where CDW order eludes single crystals, and half-metallic La 2/3 Ca 1/3 MnO 3 (LCMO). Our main finding is that the order originates at the YBCO interface due a charge transfer of electrons from LCMO. The temperature and magnetic field dependencies of the peak suggest a static, saturated phase in stark contrast to the single crystals' fluctuating order. Thus, this result demonstrates how oxide interfaces can act to nucleate metastable electronic phase transitions.

  5. Suppression of Octahedral Tilts and Associated Changes in Electronic Properties at Epitaxial Oxide Heterostructure Interfaces

    NARCIS (Netherlands)

    Borisevich, A.Y.; Chang, H.J.; Huijben, Mark; Oxley, M.P.; Okamoto, S.; Niranjan, M.K.; Burton, J.D.; Tsymbal, E.Y.; Chu, Y.H.; Yu, P.; Ramesh, R.; Kalinin, S.V.; Pennycook, S.J.

    2010-01-01

    Epitaxial oxide interfaces with broken translational symmetry have emerged as a central paradigm behind the novel behaviors of oxide superlattices. Here, we use scanning transmission electron microscopy to demonstrate a direct, quantitative unit-cell-by-unit-cell mapping of lattice parameters and

  6. Methods of assessing the effects of interface oxide growth in Magnox and AGR plant

    International Nuclear Information System (INIS)

    McLauchlin, I.R.; Wootton, M.R.; Morgan, J.D.; Watson, L.H.

    1986-09-01

    Growth of oxide at interfaces between structural steel components in CO 2 cooled reactors can deform fastenings such as bolts and welds. The mechanical response of joint members to oxide growth is discussed, and methods of assessment are outlined which contribute to procedures for ensuring continued structural integrity. (author)

  7. Application of a mixed metal oxide catalyst to a metallic substrate

    Science.gov (United States)

    Sevener, Kathleen M. (Inventor); Lohner, Kevin A. (Inventor); Mays, Jeffrey A. (Inventor); Wisner, Daniel L. (Inventor)

    2009-01-01

    A method for applying a mixed metal oxide catalyst to a metallic substrate for the creation of a robust, high temperature catalyst system for use in decomposing propellants, particularly hydrogen peroxide propellants, for use in propulsion systems. The method begins by forming a prepared substrate material consisting of a metallic inner substrate and a bound layer of a noble metal intermediate. Alternatively, a bound ceramic coating, or frit, may be introduced between the metallic inner substrate and noble metal intermediate when the metallic substrate is oxidation resistant. A high-activity catalyst slurry is applied to the surface of the prepared substrate and dried to remove the organic solvent. The catalyst layer is then heat treated to bind the catalyst layer to the surface. The bound catalyst layer is then activated using an activation treatment and calcinations to form the high-activity catalyst system.

  8. Reactivity of surface of metal oxide particles: from adsorption of ions to deposition of colloidal particles

    International Nuclear Information System (INIS)

    Lefevre, Gregory

    2010-01-01

    In this Accreditation to supervise research (HDR), the author proposes an overview of his research works in the field of chemistry. These works more particularly addressed the understanding of the surface reactivity of metal oxide particles and its implication on sorption and adherence processes. In a first part, he addresses the study of surface acidity-alkalinity: measurement of surface reactivity by acid-base titration, stability of metal oxides in suspension, effect of morphology on oxide-hydroxide reactivity. The second part addresses the study of sorption: reactivity of iron oxides with selenium species, sorption of sulphate ions on magnetite, attenuated total reflection infrared spectroscopy (ATR-IR). Adherence effects are addressed in the third part: development of an experimental device to study adherence in massive substrates, deposition of particles under turbulent flow. The last part presents a research project on the effect of temperature on ion sorption at solids/solutions interfaces, and on the adherence of metal oxide particles. The author gives his detailed curriculum, and indicates his various publications, teaching activities, research and administrative responsibilities

  9. Is Neurotoxicity of Metallic Nanoparticles the Cascades of Oxidative Stress?

    Science.gov (United States)

    Song, Bin; Zhang, YanLi; Liu, Jia; Feng, XiaoLi; Zhou, Ting; Shao, LongQuan

    2016-06-01

    With the rapid development of nanotechnology, metallic (metal or metal oxide) nanoparticles (NPs) are widely used in many fields such as cosmetics, the food and building industries, and bio-medical instruments. Widespread applications of metallic NP-based products increase the health risk associated with human exposures. Studies revealed that the brain, a critical organ that consumes substantial amounts of oxygen, is a primary target of metallic NPs once they are absorbed into the body. Oxidative stress (OS), apoptosis, and the inflammatory response are believed to be the main mechanisms underlying the neurotoxicity of metallic NPs. Other studies have disclosed that antioxidant pretreatment or co-treatment can reverse the neurotoxicity of metallic NPs by decreasing the level of reactive oxygen species, up-regulating the activities of antioxidant enzymes, decreasing the proportion of apoptotic cells, and suppressing the inflammatory response. These findings suggest that the neurotoxicity of metallic NPs might involve a cascade of events following NP-induced OS. However, additional research is needed to determine whether NP-induced OS plays a central role in the neurotoxicity of metallic NPs, to develop a comprehensive understanding of the correlations among neurotoxic mechanisms and to improve the bio-safety of metallic NP-based products.

  10. Nanostructure analysis of friction welded Pd-Ni-P/Pd-Cu-Ni-P metallic glass interface

    International Nuclear Information System (INIS)

    Ohkubo, T.; Shoji, S.; Kawamura, Y.; Hono, K.

    2005-01-01

    Friction welded Pd 40 Ni 40 P 20 /Pd 40 Cu 30 Ni 10 P 20 metallic glass interface has been characterized by energy filtering transmission electron microscopy. The interface is fully amorphous with a gradual compositional change of Cu and Ni in the range of 30 nm. By annealing above T g , the interdiffusion of Cu and Ni progressed in the supercooled liquid region, and the crystallization occurred from the Pd 40 Ni 40 P 20 glass

  11. Molecule-induced interface states dominate charge transport in Si-alkyl-metal junctions

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Lam H; Gergel-Hackett, Nadine; Zangmeister, Christopher D; Hacker, Christina A; Richter, Curt A; Kushmerick, James G [National Institute of Standards and Technology, Gaithersburg, MD 20899 (United States)], E-mail: james.kushmerick@nist.gov

    2008-09-17

    Semiconductor-molecule-metal junctions consisting of alkanethiol monolayers self-assembled on both p{sup +} and n{sup -} type highly doped Si(111) wires contacted with a 10 {mu}m Au wire in a crossed-wire geometry are examined. Low temperature transport measurements reveal that molecule-induced semiconductor interface states control charge transport across these systems. Inelastic electron tunneling spectroscopy also highlights the strong contribution of the induced interface states to the observed charge transport.

  12. Molecule-induced interface states dominate charge transport in Si-alkyl-metal junctions.

    Science.gov (United States)

    Yu, Lam H; Gergel-Hackett, Nadine; Zangmeister, Christopher D; Hacker, Christina A; Richter, Curt A; Kushmerick, James G

    2008-09-17

    Semiconductor-molecule-metal junctions consisting of alkanethiol monolayers self-assembled on both p(+) and n(-) type highly doped Si(111) wires contacted with a 10 µm Au wire in a crossed-wire geometry are examined. Low temperature transport measurements reveal that molecule-induced semiconductor interface states control charge transport across these systems. Inelastic electron tunneling spectroscopy also highlights the strong contribution of the induced interface states to the observed charge transport.

  13. Shape-controlled syntheses of metal oxide nanoparticles by the introduction of rare-earth metals.

    Science.gov (United States)

    Song, Hyo-Won; Kim, Na-Young; Park, Ji-Eun; Ko, Jae-Hyeon; Hickey, Robert J; Kim, Yong-Hyun; Park, So-Jung

    2017-02-23

    Here, we report the size- and shape-controlled synthesis of metal oxide nanoparticles through the introduction of rare-earth metals. The addition of gadolinium oleate in the synthesis of iron oxide nanoparticles induced sphere-to-cube shape changes of nanoparticles and generated iron oxide nanocubes coated with gadolinium. Based on experimental investigations and density functional theory (DFT) calculations, we attribute the shape change to the facet-selective binding of undecomposed gadolinium oleates. While many previous studies on the shape-controlled syntheses of nanoparticles rely on the stabilization of specific crystal facets by anionic surfactants or their decomposition products, this study shows that the interaction between growing transition metal oxide nanoparticles and rare-earth metal complexes can be used as a robust new mechanism for shape-controlled syntheses. Indeed, we demonstrated that this approach was applicable to other transition metal oxide nanoparticles (i.e., manganese oxide and manganese ferrite) and rare earth metals (i.e., gadolinium, europium, and cerium). This study also demonstrates that the nature of metal-ligand bonding can play an important role in the shape control of nanoparticles.

  14. Heterogeneous Metal Catalysts for Oxidation Reactions

    Directory of Open Access Journals (Sweden)

    Md. Eaqub Ali

    2014-01-01

    Full Text Available Oxidation reactions may be considered as the heart of chemical synthesis. However, the indiscriminate uses of harsh and corrosive chemicals in this endeavor are threating to the ecosystems, public health, and terrestrial, aquatic, and aerial flora and fauna. Heterogeneous catalysts with various supports are brought to the spotlight because of their excellent capabilities to accelerate the rate of chemical reactions with low cost. They also minimize the use of chemicals in industries and thus are friendly and green to the environment. However, heterogeneous oxidation catalysis are not comprehensively presented in literature. In this short review, we clearly depicted the current state of catalytic oxidation reactions in chemical industries with specific emphasis on heterogeneous catalysts. We outlined here both the synthesis and applications of important oxidation catalysts. We believe it would serve as a reference guide for the selection of oxidation catalysts for both industries and academics.

  15. Gas phase deposition of oxide and metal-oxide coatings on fuel particles

    International Nuclear Information System (INIS)

    Patokin, A.P.; Khrebtov, V.L.; Shirokov, B.M.

    2008-01-01

    Production processes and properties of oxide (Al 2 O 3 , ZrO 2 ) and metal-oxide (Mo-Al 2 O 3 , Mo-ZrO 2 , W-Al 2 O 3 , W-ZrO 2 ) coatings on molybdenum substrates and uranium dioxide fuel particles were investigated. It is shown that the main factors that have an effect on the deposition rate, density, microstructure and other properties of coatings are the deposition temperature, the ratio of H 2 and CO 2 flow rates, the total reactor pressure and the ratio of partial pressures of corresponding metal chlorides during formation of metal-oxide coatings

  16. Interface structure and mechanics between graphene and metal substrates: a first-principles study

    International Nuclear Information System (INIS)

    Xu Zhiping; Buehler, Markus J

    2010-01-01

    Graphene is a fascinating material not only for technological applications, but also as a test bed for fundamental insights into condensed matter physics due to its unique two-dimensional structure. One of the most intriguing issues is the understanding of the properties of graphene and various substrate materials. In particular, the interfaces between graphene and metal substrates are of critical importance in applications of graphene in integrated electronics, as thermal materials, and in electromechanical devices. Here we investigate the structure and mechanical interactions at a graphene-metal interface through density functional theory (DFT)-based calculations. We focus on copper (111) and nickel (111) surfaces adhered to a monolayer of graphene, and find that their cohesive energy, strength and electronic structure correlate directly with their atomic geometry. Due to the strong coupling between open d-orbitals, the nickel-graphene interface has a much stronger cohesive energy with graphene than copper. We also find that the interface cohesive energy profile features a well-and-shoulder shape that cannot be captured by simple pair-wise models such as the Lennard-Jones potential. Our results provide a detailed understanding of the interfacial properties of graphene-metal systems, and help to predict the performance of graphene-based nanoelectronics and nanocomposites. The availability of structural and energetic data of graphene-metal interfaces could also be useful for the development of empirical force fields for molecular dynamics simulations.

  17. Methods of making metal oxide nanostructures and methods of controlling morphology of same

    Science.gov (United States)

    Wong, Stanislaus S; Hongjun, Zhou

    2012-11-27

    The present invention includes a method of producing a crystalline metal oxide nanostructure. The method comprises providing a metal salt solution and providing a basic solution; placing a porous membrane between the metal salt solution and the basic solution, wherein metal cations of the metal salt solution and hydroxide ions of the basic solution react, thereby producing a crystalline metal oxide nanostructure.

  18. Research Update: Interfacing ultrasmall metal nanoclusters with biological systems

    Science.gov (United States)

    Shang, Li; Nienhaus, G. Ulrich

    2017-05-01

    Metal nanoclusters (NCs), a new type of nanomaterial with unique physicochemical properties, show great potential in many biomedical applications. Understanding their behavior in the complex biological environment is critical not only for designing highly efficient NC-based nanomedicines but also for elucidating the biological impact (e.g., toxicity) of these emerging nanomaterials. In this review, we give an overview of recent progress in exploring interactions of metal NCs with biological systems, including protein adsorption onto NCs, NC interactions with cells, and also the in vivo behavior of NCs. We also discuss the biological responses to the interactions, key parameters defining the interactions, and current challenges in the exploration of NCs in the complex biological environment.

  19. FIB/SEM and SEM/EDS microstructural analysis of metal-ceramic and zirconia-ceramic interfaces.

    Science.gov (United States)

    Massimi, F; Merlati, G; Sebastiani, M; Battaini, P; Menghini, P; Bemporad, E

    2012-01-10

    Recently introduced FIB/SEM analysis in microscopy seems to provide a high-resolution characterization of the samples by 3D (FIB) cross-sectioning and (SEM) high resolution imaging. The aim of this study was to apply the FIB/SEM and SEM/EDS analysis to the interfaces of a metal-ceramic vs. two zirconia-ceramic systems. Plate samples of three different prosthetic systems were prepared in the dental lab following the manufacturers' instructions, where metal-ceramic was the result of a ceramic veneering (porcelain-fused-to-metal) and the two zirconia-ceramic systems were produced by the dedicated CAD-CAM procedures of the zirconia cores (both with final sintering) and then veneered by layered or heat pressed ceramics. In a FIB/SEM equipment (also called DualBeam), a thin layer of platinum (1 μm) was deposited on samples surface crossing the interfaces, in order to protect them during milling. Then, increasingly deeper trenches were milled by a focused ion beam, first using a relatively higher and later using a lower ion current (from 9 nA to 0.28 nA, 30KV). Finally, FEG-SEM (5KV) micrographs (1000-50,000X) were acquired. In a SEM the analysis of the morphology and internal microstructure was performed by 13KV secondary and backscattered electrons signals (in all the samples). The compositional maps were then performed by EDS probe only in the metal-ceramic system (20kV). Despite the presence of many voids in all the ceramic layers, it was possible to identify: (1) the grain structures of the metallic and zirconia substrates, (2) the thin oxide layer at the metal-ceramic interface and its interactions with the first ceramic layer (wash technique), (3) the roughness of the two different zirconia cores and their interactions with the ceramic interface, where the presence of zirconia grains in the ceramic layer was reported in two system possibly due to sandblasting before ceramic firing.

  20. Intercalation of metals and silicon at the interface of epitaxial graphene and its substrates

    International Nuclear Information System (INIS)

    Huang Li; Xu Wen-Yan; Que Yan-De; Mao Jin-Hai; Meng Lei; Pan Li-Da; Li Geng; Wang Ye-Liang; Du Shi-Xuan; Gao Hong-Jun; Liu Yun-Qi

    2013-01-01

    Intercalations of metals and silicon between epitaxial graphene and its substrates are reviewed. For metal intercalation, seven different metals have been successfully intercalated at the interface of graphene/Ru(0001) and form different intercalated structures. Meanwhile, graphene maintains its original high quality after the intercalation and shows features of weakened interaction with the substrate. For silicon intercalation, two systems, graphene on Ru(0001) and on Ir(111), have been investigated. In both cases, graphene preserves its high quality and regains its original superlative properties after the silicon intercalation. More importantly, we demonstrate that thicker silicon layers can be intercalated at the interface, which allows the atomic control of the distance between graphene and the metal substrates. These results show the great potential of the intercalation method as a non-damaging approach to decouple epitaxial graphene from its substrates and even form a dielectric layer for future electronic applications. (topical review - low-dimensional nanostructures and devices)

  1. Topological properties and functionalities in oxide thin films and interfaces

    Science.gov (United States)

    Uchida, Masaki; Kawasaki, Masashi

    2018-04-01

    As symbolized by the Nobel Prize in Physics 2016, ‘topology’ has been recognized as an essential standpoint to understand and control the physics of condensed matter. This concept may be spreading even into application areas such as novel electronics. In this trend, there has been reported a number of studies for oxide films and heterostructures with topologically non-trivial electronic or magnetic states. In this review, we overview the trends of new topological properties and functionalities in oxide materials by sorting out a number of examples. The technological advances in oxide film growth achieved over the last few decades are now opening the door for harnessing novel topological properties.

  2. Metal Acetylacetonates as General Precursors for the Synthesis of Early Transition Metal Oxide Nanomaterials

    OpenAIRE

    Willis, Amanda L.; Chen, Zhuoying; He, Jiaqing; Zhu, Yimei; Turro, Nicholas J.; O'Brien, Stephen

    2007-01-01

    A versatile, convenient, and nontoxic solvothermal method for the synthesis of nanocrystalline iron, chromium, and manganese oxides is described. This method employs the reactions of metal acetylacetonate precursors and oxygen-containing solvents in a reaction to prepare metal oxide nanoparticles. Characterization of these nanocrystalline materials was carried out employing transmission electron microscopy (TEM), high-resolution TEM (HRTEM), X-ray diffraction (XRD), and elemental analysis.

  3. Metal Acetylacetonates as General Precursors for the Synthesis of Early Transition Metal Oxide Nanomaterials

    Directory of Open Access Journals (Sweden)

    Amanda L. Willis

    2007-01-01

    Full Text Available A versatile, convenient, and nontoxic solvothermal method for the synthesis of nanocrystalline iron, chromium, and manganese oxides is described. This method employs the reactions of metal acetylacetonate precursors and oxygen-containing solvents in a reaction to prepare metal oxide nanoparticles. Characterization of these nanocrystalline materials was carried out employing transmission electron microscopy (TEM, high-resolution TEM (HRTEM, X-ray diffraction (XRD, and elemental analysis.

  4. An alternative pathway for marine nitrous oxide production at oxic-anoxic interfaces from coupled biotic-abiotic reactions

    Science.gov (United States)

    Glass, J. B.; Stanton, C. L.; Ochoa, H.; Haslun, J. A.; Gandhi, H.; Taillefert, M.; Dichristina, T. J.; Stewart, F. J.; Klotz, M. G.; Ostrom, N. E.

    2016-02-01

    Marine emissions of nitrous oxide (N2O), a potent greenhouse gas, comprise approximately a third of global sources. Recent evidence suggests that the dominant source of N2O in seawater is the activity of ammonia-oxidizing Thaumarchaeota that lack characterized N2O-generating enzymes. Nitrous oxide may arise from a novel enzyme and/or abiotic reactions between nitrification intermediates, hydroxylamine (NH2OH) and nitric oxide (NO), and redox-active metals in seawater. Isotopic site preference, or difference in δ15N between the two nitrogen atoms in N2O, has been used as tracer for microbial N2O production pathways (-10 to 0‰ for nitrifier-denitrification and denitrification vs. 30-37‰ for nitrification via NH2OH oxidation). Seawater N2O site preference falls in between these two characterized end members, suggesting simultaneous production via a combination of both microbial pathways or via a novel mechanism with intermediate site preference. Here we show significant N2O production in abiotic experiments after addition of iron to seawater containing NH2OH and NO. The N2O produced from chemical reduction of NO by Fe(II) had a site preference of 16‰ whereas N2O produced from abiotic NH2OH oxidation had a site preference of 31‰. We propose that coupled biotic-abiotic N2O production pathways could contribute significant sources of N2O at marine oxic-anoxic interfaces.

  5. Chemistry of layered d-metal pnictide oxides and their potential as candidates for new superconductors

    International Nuclear Information System (INIS)

    Ozawa, Tadashi C; Kauzlarich, Susan M

    2008-01-01

    Layered d-metal pnictide oxides are a unique class of compounds which consist of characteristic d-metal pnictide layers and metal oxide layers. More than 100 of these layered compounds, including the recently discovered Fe-based superconducting pnictide oxides, can be classified into nine structure types. These structure types and the chemical and physical properties of the characteristic d-metal pnictide layers and metal oxide layers of the layered d-metal pnictide oxides are reviewed and discussed. Furthermore, possible approaches to design new superconductors based on these layered d-metal pnictide oxides are proposed. (topical review)

  6. Advances in metal-induced oxidative stress and human disease

    International Nuclear Information System (INIS)

    Jomova, Klaudia; Valko, Marian

    2011-01-01

    Detailed studies in the past two decades have shown that redox active metals like iron (Fe), copper (Cu), chromium (Cr), cobalt (Co) and other metals undergo redox cycling reactions and possess the ability to produce reactive radicals such as superoxide anion radical and nitric oxide in biological systems. Disruption of metal ion homeostasis may lead to oxidative stress, a state where increased formation of reactive oxygen species (ROS) overwhelms body antioxidant protection and subsequently induces DNA damage, lipid peroxidation, protein modification and other effects, all symptomatic for numerous diseases, involving cancer, cardiovascular disease, diabetes, atherosclerosis, neurological disorders (Alzheimer's disease, Parkinson's disease), chronic inflammation and others. The underlying mechanism of action for all these metals involves formation of the superoxide radical, hydroxyl radical (mainly via Fenton reaction) and other ROS, finally producing mutagenic and carcinogenic malondialdehyde (MDA), 4-hydroxynonenal (HNE) and other exocyclic DNA adducts. On the other hand, the redox inactive metals, such as cadmium (Cd), arsenic (As) and lead (Pb) show their toxic effects via bonding to sulphydryl groups of proteins and depletion of glutathione. Interestingly, for arsenic an alternative mechanism of action based on the formation of hydrogen peroxide under physiological conditions has been proposed. A special position among metals is occupied by the redox inert metal zinc (Zn). Zn is an essential component of numerous proteins involved in the defense against oxidative stress. It has been shown, that depletion of Zn may enhance DNA damage via impairments of DNA repair mechanisms. In addition, Zn has an impact on the immune system and possesses neuroprotective properties. The mechanism of metal-induced formation of free radicals is tightly influenced by the action of cellular antioxidants. Many low-molecular weight antioxidants (ascorbic acid (vitamin C), alpha

  7. A comparison in activity between transition-metal oxides and transition metals

    Science.gov (United States)

    Vojvodic, Aleksandra; Studt, Felix; Abild-Pedersen, Frank; Bligaard, Thomas; Nørskov, Jens

    2012-02-01

    Transition-metal oxides are widely used materials in catalysis as substrates and promoters, but also as the active catalyst materials themselves. We compare the reactivity of transition-metal oxides with the one of transition metals. The comparison is exemplified for the ammonia synthesis reaction. First we show that there exist characteristic Brønsted-Evans Polanyi (BEP) relations (linear relations between transition state and dissociation energies) for dissociation of molecules on transition-metal oxides in the rutile and perovskite structure. It is well-known that the (211) metal surface is several orders of magnitude more reactive than the (111) metal surface due to the lower BEP line for the 211 facet. We find that both rutiles and perovskites follow BEP relations that are lower than the one of the 211 facet. Second we utilize the established BEP relations together with calculated adsorption energetics in a micro-kinetic model to obtain a volcano plot for the catalytic activity. We find that oxides have a higher turn over frequency as compared with metals. Hence, oxides intrinsically have a great advantage in terms of catalytic activity which opens up for catalyst design.

  8. Controlling interfacial properties in supported metal oxide catalysts through metal–organic framework templating

    Energy Technology Data Exchange (ETDEWEB)

    Abney, Carter W. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Chemical Sciences Division; Patterson, Jacob T. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Chemical Sciences Division; Gilhula, James C. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Chemical Sciences Division; Wang, Li [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Chemical Sciences Division; Hensley, Dale K. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Center for Nanophase Materials Science (CNMS); Chen, Jihua [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Center for Nanophase Materials Science (CNMS); Foo, Guo Shiou [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Chemical Sciences Division; Wu, Zili [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Chemical Sciences Division; Dai, Sheng [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Chemical Sciences Division; Univ. of Tennessee, Knoxville, TN (United States). Dept. of Chemistry

    2017-06-08

    Precise control over the chemical structure of hard-matter materials is a grand challenge of basic science and a prerequisite for the development of advanced catalyst systems. In this work we report the application of a sacrificial metal-organic framework (MOF) template for the synthesis of a porous supported metal oxide catalyst, demonstrating proof-of-concept for a highly generalizable approach to the preparation new catalyst materials. Application of 2,2’-bipyridine-5,5’-dicarboxylic acid as the organic strut in the Ce MOF precursor results in chelation of Cu2+ and affords isolation of the metal oxide precursor. Following pyrolysis of the template, homogeneously dispersed CuO nanoparticles are formed in the resulting porous CeO2 support. By partially substituting non-chelating 1,1’-biphenyl-4,4’-dicarboxylic acid, the Cu2+ loading and dispersion can be finely tuned, allowing precise control over the CuO/CeO2 interface in the final catalyst system. Characterization by x-ray diffraction, x-ray absorption fine structure spectroscopy, and in situ IR spectroscopy/mass spectrometry confirm control over interface formation to be a function of template composition, constituting the first report of a MOF template being used to control interfacial properties in a supported metal oxide. Using CO oxidation as a model reaction, the system with the greatest number of interfaces possessed the lowest activation energy and better activity under differential conditions, but required higher temperature for catalytic onset and displayed inferior efficiency at 100 °C than systems with higher Cu-loading. This finding is attributable to greater CO adsorption in the more heavily-loaded systems, and indicates catalyst performance for these supported oxide systems to be a function of at least two parameters: size of adsorption site and extent of interface. In conclusion, optimization of catalyst materials thus requires precise control

  9. CO-oxidation catalysts: Low-temperature CO oxidation over Noble-Metal Reducible Oxide (NMRO) catalysts

    Science.gov (United States)

    Herz, Richard K.

    1990-01-01

    Oxidation of CO to CO2 is an important reaction technologically and environmentally and a complex and interesting reaction scientifically. In most cases, the reaction is carried out in order to remove CO as an environmental hazard. A major application of heterogeneous catalysts is catalytic oxidation of CO in the exhaust of combustion devices. The reaction over catalysts in exhaust gas is fast and often mass-transfer-limited since exhaust gases are hot and O2/CO ratios are high. The main challenges to catalyst designers are to control thermal sintering and chemical poisoning of the active materials. The effect of the noble metal on the oxide is discussed, followed by the effect of the oxide on the noble metal, the interaction of the noble metal and oxide to form unique catalytic sites, and the possible ways in which the CO oxidation reaction is catalyzed by the NMRO materials.

  10. Polymer-supported metals and metal oxide nanoparticles: synthesis, characterization, and applications

    International Nuclear Information System (INIS)

    Sarkar, Sudipta; Guibal, E.; Quignard, F.; SenGupta, A. K.

    2012-01-01

    Metal and metal oxide nanoparticles exhibit unique properties in regard to sorption behaviors, magnetic activity, chemical reduction, ligand sequestration among others. To this end, attempts are being continuously made to take advantage of them in multitude of applications including separation, catalysis, environmental remediation, sensing, biomedical applications and others. However, metal and metal oxide nanoparticles lack chemical stability and mechanical strength. They exhibit extremely high pressure drop or head loss in fixed-bed column operation and are not suitable for any flow-through systems. Also, nanoparticles tend to aggregate; this phenomenon reduces their high surface area to volume ratio and subsequently reduces effectiveness. By appropriately dispersing metal and metal oxide nanoparticles into synthetic and naturally occurring polymers, many of the shortcomings can be overcome without compromising the parent properties of the nanoparticles. Furthermore, the appropriate choice of the polymer host with specific functional groups may even lead to the enhancement of the properties of nanoparticles. The synthesis of hybrid materials involves two broad pathways: dispersing the nanoparticles (i) within pre-formed or commercially available polymers; and (ii) during the polymerization process. This review presents a broad coverage of nanoparticles and polymeric/biopolymeric host materials and the resulting properties of the hybrid composites. In addition, the review discusses the role of the Donnan membrane effect exerted by the host functionalized polymer in harnessing the desirable properties of metal and metal oxide nanoparticles for intended applications.

  11. Behavior of ceramic particles at the solid-liquid metal interface in metal matrix composites

    Science.gov (United States)

    Stefanescu, D. M.; Dhindaw, B. K.; Kacar, S. A.; Moitra, A.

    1988-01-01

    Directional solidification results were obtained in order to investigate particle behavior at the solid-liquid interface in Al-2 pct Mg (cellular interface) and Al-6.1 pct Ni (eutectic interface) alloys. It is found that particles can be entrapped in the solid if adequate solidification rates and temperature gradients are used. Model results showed critical velocity values slightly higher than those obtained experimentally.

  12. Interfacing BiVO4with Reduced Graphene Oxide for Enhanced Photoactivity: A Tale of Facet Dependence of Electron Shuttling.

    Science.gov (United States)

    Tan, Hui Ling; Tahini, Hassan A; Wen, Xiaoming; Wong, Roong Jien; Tan, Xin; Iwase, Akihide; Kudo, Akihiko; Amal, Rose; Smith, Sean C; Ng, Yun Hau

    2016-10-01

    Efficient interfacial charge transfer is essential in graphene-based semiconductors to realize their superior photoactivity. However, little is known about the factors (for example, semiconductor morphology) governing the charge interaction. Here, it is demonstrated that the electron transfer efficacy in reduced graphene oxide-bismuth oxide (RGO/BiVO 4 ) composite is improved as the relative exposure extent of {010}/{110} facets on BiVO 4 increases, indicated by the greater extent of photocurrent enhancement. The dependence of charge transfer ability on the exposure degree of {010} relative to {110} is revealed to arise due to the difference in electronic structures of the graphene/BiVO 4 {010} and graphene/BiVO 4 {110} interfaces, as evidenced by the density functional theory calculations. The former interface is found to be metallic with higher binding energy and smaller Schottky barrier than that of the latter semiconducting interface. The facet-dependent charge interaction elucidated in this study provides new aspect for design of graphene-based semiconductor photocatalyst useful in manifold applications. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Fabrication of Metal and Metal Oxide Nanoparticles by Algae and their Toxic Effects

    OpenAIRE

    Siddiqi, Khwaja Salahuddin; Husen, Azamal

    2016-01-01

    Of all the aquatic organisms, algae are a good source of biomolecules. Since algae contain pigments, proteins, carbohydrates, fats, nucleic acids and secondary metabolites such as alkaloids, some aromatic compounds, macrolides, peptides and terpenes, they act as reducing agents to produce nanoparticles from metal salts without producing any toxic by-product. Once the algal biomolecules are identified, the nanoparticles of desired shape or size may be fabricated. The metal and metal oxide nano...

  14. Preventing Bacterial Infections using Metal Oxides Nanocoatings on Bone Implant

    Science.gov (United States)

    Duceac, L. D.; Straticiuc, S.; Hanganu, E.; Stafie, L.; Calin, G.; Gavrilescu, S. L.

    2017-06-01

    Nowadays bone implant removal is caused by infection that occurs around it possibly acquired after surgery or during hospitalization. The purpose of this study was to reveal some metal oxides applied as coatings on bone implant thus limiting the usual antibiotics-resistant bacteria colonization. Therefore ZnO, TiO2 and CuO were synthesized and structurally and morphologically analized in order to use them as an alternative antimicrobial agents deposited on bone implant. XRD, SEM, and FTIR characterization techniques were used to identify structure and texture of these nanoscaled metal oxides. These metal oxides nanocoatings on implant surface play a big role in preventing bacterial infection and reducing surgical complications.

  15. Water Oxidation Mechanisms of Metal Oxide Catalysts by Vibrational Spectroscopy of Transient Intermediates

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Miao [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Chemical Sciences Division; Univ. of California, Berkeley, CA (United States); Frei, Heinz [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Molecular Biophysics and Integrated Bioimaging Division; Univ. of California, Berkeley, CA (United States)

    2017-02-22

    Water oxidation is an essential reaction of an artificial photosystem for solar fuel generation because it provides electrons needed to reduce carbon dioxide or protons to a fuel. Earth-abundant metal oxides are among the most attractive catalytic materials for this reaction because of their robustness and scalability, but their efficiency poses a challenge. Knowledge of catalytic surface intermediates gained by vibrational spectroscopy under reaction conditions plays a key role in uncovering kinetic bottlenecks and provides a basis for catalyst design improvements. Recent dynamic infrared and Raman studies reveal the molecular identity of transient surface intermediates of water oxidation on metal oxides. In conclusion, combined with ultrafast infrared observations of how charges are delivered to active sites of the metal oxide catalyst and drive the multielectron reaction, spectroscopic advances are poised to play a key role in accelerating progress toward improved catalysts for artificial photosynthesis.

  16. Highly Sensitive Sensors Based on Metal-Oxide Nanocolumns for Fire Detection

    Directory of Open Access Journals (Sweden)

    Kwangjae Lee

    2017-02-01

    Full Text Available A fire detector is the most important component in a fire alarm system. Herein, we present the feasibility of a highly sensitive and rapid response gas sensor based on metal oxides as a high performance fire detector. The glancing angle deposition (GLAD technique is used to make the highly porous structure such as nanocolumns (NCs of various metal oxides for enhancing the gas-sensing performance. To measure the fire detection, the interface circuitry for our sensors (NiO, SnO2, WO3 and In2O3 NCs is designed. When all the sensors with various metal-oxide NCs are exposed to fire environment, they entirely react with the target gases emitted from Poly(vinyl chlorides (PVC decomposed at high temperature. Before the emission of smoke from the PVC (a hot-plate temperature of 200 °C, the resistances of the metal-oxide NCs are abruptly changed and SnO2 NCs show the highest response of 2.1. However, a commercial smoke detector did not inform any warning. Interestingly, although the NiO NCs are a p-type semiconductor, they show the highest response of 577.1 after the emission of smoke from the PVC (a hot-plate temperature of 350 °C. The response time of SnO2 NCs is much faster than that of a commercial smoke detector at the hot-plate temperature of 350 °C. In addition, we investigated the selectivity of our sensors by analyzing the responses of all sensors. Our results show the high potential of a gas sensor based on metal-oxide NCs for early fire detection.

  17. Highly Sensitive Sensors Based on Metal-Oxide Nanocolumns for Fire Detection.

    Science.gov (United States)

    Lee, Kwangjae; Shim, Young-Seok; Song, Young Geun; Han, Soo Deok; Lee, Youn-Sung; Kang, Chong-Yun

    2017-02-07

    A fire detector is the most important component in a fire alarm system. Herein, we present the feasibility of a highly sensitive and rapid response gas sensor based on metal oxides as a high performance fire detector. The glancing angle deposition (GLAD) technique is used to make the highly porous structure such as nanocolumns (NCs) of various metal oxides for enhancing the gas-sensing performance. To measure the fire detection, the interface circuitry for our sensors (NiO, SnO₂, WO₃ and In₂O₃ NCs) is designed. When all the sensors with various metal-oxide NCs are exposed to fire environment, they entirely react with the target gases emitted from Poly(vinyl chlorides) (PVC) decomposed at high temperature. Before the emission of smoke from the PVC (a hot-plate temperature of 200 °C), the resistances of the metal-oxide NCs are abruptly changed and SnO₂ NCs show the highest response of 2.1. However, a commercial smoke detector did not inform any warning. Interestingly, although the NiO NCs are a p -type semiconductor, they show the highest response of 577.1 after the emission of smoke from the PVC (a hot-plate temperature of 350 °C). The response time of SnO₂ NCs is much faster than that of a commercial smoke detector at the hot-plate temperature of 350 °C. In addition, we investigated the selectivity of our sensors by analyzing the responses of all sensors. Our results show the high potential of a gas sensor based on metal-oxide NCs for early fire detection.

  18. Designing porous metallic glass compact enclosed with surface iron oxides

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Jae Young; Park, Hae Jin; Hong, Sung Hwan; Kim, Jeong Tae; Kim, Young Seok; Park, Jun-Young; Lee, Naesung [Hybrid Materials Center (HMC), Faculty of Nanotechnology and Advanced Materials Engineering, Sejong University, 209 Neungdong-ro, Gwangjin-gu, Seoul 143-747 (Korea, Republic of); Seo, Yongho [Graphene Research Institute (GRI) & HMC, Faculty of Nanotechnology and Advanced Materials Engineering, Sejong University, 209 Neungdong-ro, Gwangjin-gu, Seoul 143-747 (Korea, Republic of); Park, Jin Man, E-mail: jinman_park@hotmail.com [Global Technology Center, Samsung Electronics Co., Ltd, 129 Samsung-ro, Yeongtong-gu, Suwon-si, Gyeonggi-do 443-742 (Korea, Republic of); Kim, Ki Buem, E-mail: kbkim@sejong.ac.kr [Hybrid Materials Center (HMC), Faculty of Nanotechnology and Advanced Materials Engineering, Sejong University, 209 Neungdong-ro, Gwangjin-gu, Seoul 143-747 (Korea, Republic of)

    2015-06-25

    Highlights: • Porous metallic glass compact was developed using electro-discharge sintering process. • Uniform PMGC can only be achieved when low electrical input energy was applied. • Functional iron-oxides were formed on the surface of PMGCs by hydrothermal technique. - Abstract: Porous metallic glass compact (PMGC) using electro-discharge sintering (EDS) process of gas atomized Zr{sub 41.2}Ti{sub 13.8}Cu{sub 12.5}Ni{sub 10}Be{sub 22.5} metallic glass powder was developed. The formation of uniform PMGC can only be achieved when low electrical input energy was applied. Functional iron-oxides were formed on the surface of PMGCs by hydrothermal technique. This finding suggests that PMGC can be applied in the new area such as catalyst via hydrothermal technique and offer a promising guideline for using the metallic glasses as a potential functional application.

  19. Microfabricated gas sensor systems with sensitive nanocrystalline metal-oxide films

    International Nuclear Information System (INIS)

    Graf, M.; Gurlo, A.; Barsan, N.; Weimar, U.; Hierlemann, A.

    2006-01-01

    This article gives an overview on recent developments in metal-oxide-based gas sensor systems, in particular on nanocrystalline oxide materials deposited on modern, state-of-the-art sensor platforms fabricated in microtechnology. First, metal-oxide-based gas sensors are introduced, and the underlying principles and fundamentals of the gas sensing process are laid out. In the second part, the different deposition methods, such as evaporation, sputtering, sol-gel techniques, aerosol methods, and screen-printing, and their applicability to micro-scale substrates are discussed in terms of their deposition precision, the achievable layer thickness, as well as with regard to the possibility to use pre-processed materials. In the third part, microsensor platforms and, in particular, semiconductor- and microelectronics-based sensor platforms, which have been fabricated in, e.g., standard CMOS-technology (CMOS: complementary metal-oxide semiconductor), are briefly reviewed. The use of such microfabricated sensor platforms inevitably imposes constraints, such as temperature limits, on the applied nanomaterial processing and deposition methods. These limitations are discussed and work-arounds are described. Additionally, monolithic sensor systems are presented that combine microtransducers or microhotplates, which are coated with nanomaterials, with the necessary control and driving electronics on a single chip. The most advanced of such systems are standalone units that can be directly connected to a computer via a digital interface

  20. Conditioning of Si-interfaces by wet-chemical oxidation: Electronic interface properties study by surface photovoltage measurements

    Science.gov (United States)

    Angermann, Heike

    2014-09-01

    The field-modulated surface photovoltage (SPV) method, a very surface sensitive technique, was utilized to determine electronic interface properties on wet-chemically oxidized and etched silicon (Si) interfaces. The influence of preparation-induced surface micro-roughness and un-stoichiometric oxides on the resulting the surface charge, energetic distribution Dit(E), and density Dit,min of rechargeable states was studied by simultaneous, spectroscopic ellipsometry (SE) measurements on polished Si(111) and Si(100) substrates. Based on previous findings and new research, a study of conventional and newly developed wet-chemical oxidation methods was established, correlating the interactions between involved oxidizing and etching solutions and the initial substrate morphology to the final surface conditioning. It is shown, which sequences of wet-chemical oxidation and oxide removal, have to be combined in order to achieve atomically smooth, hydrogen terminated surfaces, as well as ultra-thin oxide layers with low densities of rechargeable states on flat, saw damage etched, and textured Si substrates, as commonly applied in silicon device and solar cell manufacturing. These conventional strategies for wet-chemical pre-treatment are mainly based on concentrated solutions. Therefore, special attention was put on the development of more environmentally acceptable processes, utilizing e.g. hot pure water with low contents of oxygen or hydrochloric acid, and of ozone, working at ambient temperatures. According to our results, these methods could be a high quality and low cost alternative to current approaches with liquid chemicals for the preparation of hydrophobic Si substrate surfaces and ultra-thin passivating oxide layers. As demonstrated for selected examples, the effect of optimized wet-chemical pre-treatments can be preserved during subsequent soft plasma enhanced chemical vapor depositions of Si oxides (SiOx), or amorphous materials such as Si (a-Si:H), Si nitride (a

  1. High temperature oxidation of metals: vacancy injection and consequences on the mechanical properties

    International Nuclear Information System (INIS)

    Perusin, S.

    2004-11-01

    The aim of this work is to account for the effects of the high temperature oxidation of metals on their microstructure and their mechanical properties. 'Model' materials like pure nickel, pure iron and the Ni-20Cr alloy are studied. Nickel foils have been oxidised at 1000 C on one side only in laboratory air, the other side being protected from oxidation by a reducing atmosphere. After the oxidation treatment, the unoxidized face was carefully examined by using an Atomic Force Microscope (AFM). Grain boundaries grooves were characterised and their depth were compared to the ones obtained on the same sample heat treated in the reducing atmosphere during the same time. They are found to be much deeper in the case of the single side oxidised samples. It is shown that this additional grooving is directly linked to the growth of the oxide scale on the opposite side and that it can be explained by the diffusion of the vacancies produced at the oxide scale - metal interface, across the entire sample through grain boundaries. Moreover, the comparison between single side oxidised samples and samples oxidised on both sides points out that voids in grain boundaries are only observed in this latter case proving the vacancies condensation in the metal when the two faces are oxidised. The role of the carbon content and the sample's geometry on this phenomenon is examined in detail. The diffusion of vacancies is coupled with the transport of oxygen so that a mechanism of oxygen transport by vacancies is suggested. The tensile tests realised at room temperature on nickel foils (bamboo microstructure) show that the oxide scale can constitute a barrier to the emergence of dislocations at the metal surface. Finally, the Ni-20Cr alloy is tested in tensile and creep tests between 25 and 825 C in oxidising or reducing atmospheres. (author)

  2. Structure of the Buried Metal-Molecule Interface in Organic Thin Film Devices

    DEFF Research Database (Denmark)

    Hansen, Christian Rein; Sørensen, Thomas Just; Glyvradal, Magni

    2009-01-01

    . By comparison of XR data for the five-layer Pb2+ arachidate LB film before and after vapor deposition of the Ti/Al top electrode, a detailed account of the structural damage to the organic film at the buried metal-molecule interface is obtained. We find that the organized structure of the two topmost LB layers...

  3. Investigation of buried metal-organic interface with photoelectron spectroscopy (PES)

    Energy Technology Data Exchange (ETDEWEB)

    Vrdoljak, Pavo; Schoell, Achim; Reinert, Friedrich [Universitaet Wuerzburg, Experimentelle Physik II, 97074 Wuerzburg (Germany); Umbach, Eberhard [Forschungszentrum Karlsruhe, 76021 Karlsruhe (Germany)

    2008-07-01

    Metal-organic interfaces are of crucial importance for electronic devices since they influence the layer morphology, the electronic structure at contacts, and the charge carrier transport. Various investigations have addressed this issue from the viewpoint of surface science, applying model systems with thin organic films on flat (single crystalline or amorphous) metal substrates. The contacts in electronic devices, however, can be very different. This is mainly due to the morphological roughness of the interface in case of a metal top contact deposited on an organic layer and the possible influence on the electronic structure. In case of real contacts also interdiffusion has to be taken into account. However, surface sensitive techniques such as photoelectron spectroscopy (PES) and atomic force microscopy (AFM) can not immediately access the buried interface. To tackle this problem we have applied and optimised a lift-off technique which allows the removal of the metal top-contact in the UHV and analyse the interface between the contact and the organic film. We present first PES and AFM results of Au contacts deposited on PTCDA layers.

  4. Renormalization of Molecular Quasiparticle Levels at Metal-Molecule Interfaces: Trends across Binding Regimes

    DEFF Research Database (Denmark)

    Thygesen, Kristian Sommer; Rubio, Angel

    2009-01-01

    When an electron or a hole is added into an orbital of an adsorbed molecule the substrate electrons will rearrange in order to screen the added charge. This polarization effect reduces the electron addition and removal energies of the adsorbed molecule relative to those of the free molecule. Usin......) polarization of the metal (image charge formation) and (ii) polarization of the molecule via charge transfer across the interface. The importance of (i) and (ii) is found to increase with the metal density of states at the Fermi level and metal-molecule coupling strength, respectively....

  5. Large Lateral Photovoltaic Effect in Metal-(Oxide-Semiconductor Structures

    Directory of Open Access Journals (Sweden)

    Chongqi Yu

    2010-11-01

    Full Text Available The lateral photovoltaic effect (LPE can be used in position-sensitive detectors to detect very small displacements due to its output of lateral photovoltage changing linearly with light spot position. In this review, we will summarize some of our recent works regarding LPE in metal-semiconductor and metal-oxide-semiconductor structures, and give a theoretical model of LPE in these two structures.

  6. Large lateral photovoltaic effect in metal-(oxide-) semiconductor structures.

    Science.gov (United States)

    Yu, Chongqi; Wang, Hui

    2010-01-01

    The lateral photovoltaic effect (LPE) can be used in position-sensitive detectors to detect very small displacements due to its output of lateral photovoltage changing linearly with light spot position. In this review, we will summarize some of our recent works regarding LPE in metal-semiconductor and metal-oxide-semiconductor structures, and give a theoretical model of LPE in these two structures.

  7. Combustion Kinetics of Metal Oxide and Halide Radicals.

    Science.gov (United States)

    1985-01-04

    often not obeyed. Particularly for exothermic and slightly endothermic reactions, order of magnitude errors can be made by extrap - 1olations based on the...schematic of the HTFFR, high-temperature fast-flow reactor , method we are using to generate the metallic radicals and measure their oxidation kinetics...TEMPERATURE INTERVALS. TECHNIQUE High-Temperature Fast-Flow Reactor FURNACE REACTION LENGTH-REACTION TIME SNA- LASER FLUORESCENCE OXIDANTIo CO2 METAL IN

  8. New Digital Metal-Oxide (MOx) Sensor Platform.

    Science.gov (United States)

    Rüffer, Daniel; Hoehne, Felix; Bühler, Johannes

    2018-03-31

    The application of metal oxide gas sensors in Internet of Things (IoT) devices and mobile platforms like wearables and mobile phones offers new opportunities for sensing applications. Metal-oxide (MOx) sensors are promising candidates for such applications, thanks to the scientific progresses achieved in recent years. For the widespread application of MOx sensors, viable commercial offerings are required. In this publication, the authors show that with the new Sensirion Gas Platform (SGP) a milestone in the commercial application of MOx technology has been reached. The architecture of the new platform and its performance in selected applications are presented.

  9. Metal Oxide Nano structures: Synthesis, Properties, and Applications

    International Nuclear Information System (INIS)

    Xu, L. H.; Patil, D. S.; Yang, J.; Xiao, J.

    2015-01-01

    In recent years, nano structured materials have attracted wide attention due to their fascinating optical and electrical properties, which make these materials potentially suitable for applications in electronics, optics, photonics, and sensors. Some metal oxides show a wide variety of morphologies such as nano wires, nano rods, nano tubes, nano rings, and nano belts. Synthesis and investigation of these metal-oxide nano structures are beneficial not only for understanding the fundamental phenomena in low dimensional systems, but also for developing new-generation nano devices with high performance.

  10. Microwave-assisted route for synthesis of nanosized metal oxides

    Directory of Open Access Journals (Sweden)

    Arunkumar Lagashetty et al

    2007-01-01

    Full Text Available Microwave-assisted route for the synthesis of nanomaterials has gained importance in the field of synthetic technology because of its faster, cleaner and cost effectiveness than the other conventional and wet chemical methods for the preparation of metal oxide nanoparticles. In the present work, synthesis of metal oxide nanoparticles viz., γ-Fe2O3, NiO, ZnO, CuO and Co-γ-Fe2O3 were carried out by microwave-assisted route through the thermal decomposition of their respective metal oxalate precursors employing polyvinyl alcohol as a fuel. The metal oxide nanoparticles are then characterized for their size and γ to α (in γ-Fe2O3 transition and structure by employing powder X-ray diffraction (XRD pattern, high-temperature X-ray diffraction (HTXRD pattern and Fourier transform infrared (FT-IR spectral studies. The morphology of the samples ranged from nanorods to irregular-shaped particles for different metal oxide samples on the basis of scanning electron microscopy and transmission electron microscopy images. Frequency-dependent dielectric study of the ferrite samples (γ-Fe2O3 and Co-Fe2O3 showed a similar behaviour, where the dielectric constant decreased rapidly with increase in frequency. Possible explanation for this behaviour is given.

  11. Global DNA methylation and oxidative stress biomarkers in workers exposed to metal oxide nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Liou, Saou-Hsing; Wu, Wei-Te; Liao, Hui-Yi [National Institute of Environmental Health Sciences, National Health Research Institutes, Zhunan, Miaoli County, Taiwan (China); Chen, Chao-Yu; Tsai, Cheng-Yen; Jung, Wei-Ting [Department of Chemistry, Fu Jen Catholic University, New Taipei City, Taiwan (China); Lee, Hui-Ling, E-mail: huilinglee3573@gmail.com [Department of Chemistry, Fu Jen Catholic University, New Taipei City, Taiwan (China)

    2017-06-05

    Highlights: • Global methylation and oxidative DNA damage levels in nanomaterial handling workers were assessed. • 8-isoprostane in exhaled breath condensate of workers exposed to nanoparticles was higher. • 8-OHdG was negatively correlated with global methylation. • Exposure to metal oxide nanoparticles may lead to global methylation and DNA oxidative damage. - Abstract: This is the first study to assess global methylation, oxidative DNA damage, and lipid peroxidation in workers with occupational exposure to metal oxide nanomaterials (NMs). Urinary and white blood cell (WBC) 8-hydroxydeoxyguanosine (8-OHdG), and exhaled breath condensate (EBC) 8-isoprostane were measured as oxidative stress biomarkers. WBC global methylation was measured as an epigenetic alteration. Exposure to TiO{sub 2}, SiO{sub 2,} and indium tin oxide (ITO) resulted in significantly higher oxidative biomarkers such as urinary 8-OHdG and EBC 8-isoprostane. However, significantly higher WBC 8-OHdG and lower global methylation were only observed in ITO handling workers. Significant positive correlations were noted between WBC and urinary 8-OHdG (Spearman correlation r = 0.256, p = 0.003). Furthermore, a significant negative correlation was found between WBC 8-OHdG and global methylation (r = −0.272, p = 0.002). These results suggest that exposure to metal oxide NMs may lead to global methylation, DNA oxidative damage, and lipid peroxidation.

  12. Metal Phosphate-Supported Pt Catalysts for CO Oxidation

    Science.gov (United States)

    Qian, Xiaoshuang; Qin, Hongmei; Meng, Tao; Lin, Yi; Ma, Zhen

    2014-01-01

    Oxides (such as SiO2, TiO2, ZrO2, Al2O3, Fe2O3, CeO2) have often been used to prepare supported Pt catalysts for CO oxidation and other reactions, whereas metal phosphate-supported Pt catalysts for CO oxidation were rarely reported. Metal phosphates are a family of metal salts with high thermal stability and acid-base properties. Hydroxyapatite (Ca10(PO4)6(OH)2, denoted as Ca-P-O here) also has rich hydroxyls. Here we report a series of metal phosphate-supported Pt (Pt/M-P-O, M = Mg, Al, Ca, Fe, Co, Zn, La) catalysts for CO oxidation. Pt/Ca-P-O shows the highest activity. Relevant characterization was conducted using N2 adsorption-desorption, inductively coupled plasma (ICP) atomic emission spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), CO2 temperature-programmed desorption (CO2-TPD), X-ray photoelectron spectroscopy (XPS), and H2 temperature-programmed reduction (H2-TPR). This work furnishes a new catalyst system for CO oxidation and other possible reactions. PMID:28788293

  13. Sonochemical water splitting in the presence of powdered metal oxides.

    Science.gov (United States)

    Morosini, Vincent; Chave, Tony; Virot, Matthieu; Moisy, Philippe; Nikitenko, Sergey I

    2016-03-01

    Kinetics of hydrogen formation was explored as a new chemical dosimeter allowing probing the sonochemical activity of argon-saturated water in the presence of micro- and nano-sized metal oxide particles exhibiting catalytic properties (ThO2, ZrO2, and TiO2). It was shown that the conventional sonochemical dosimeter based on H2O2 formation is hardly applicable in such systems due to catalytic degradation of H2O2 at oxide surface. The study of H2 generation revealed that at low-frequency ultrasound (20 kHz) the sonochemical water splitting is greatly improved for all studied metal oxides. The highest efficiency is observed for relatively large micrometric particles of ThO2 which is assigned to ultrasonically-driven particle fragmentation accompanied by mechanochemical water molecule splitting. The nanosized metal oxides do not exhibit particle size reduction under ultrasonic treatment but nevertheless yield higher quantities of H2. The enhancement of sonochemical water splitting in this case is most probably resulting from better bubble nucleation in heterogeneous systems. At high-frequency ultrasound (362 kHz), the effect of metal oxide particles results in a combination of nucleation and ultrasound attenuation. In contrast to 20 kHz, micrometric particles slowdown the sonolysis of water at 362 kHz due to stronger attenuation of ultrasonic waves while smaller particles show a relatively weak and various directional effects. Copyright © 2015 Elsevier B.V. All rights reserved.

  14. Metal Phosphate-Supported Pt Catalysts for CO Oxidation

    Directory of Open Access Journals (Sweden)

    Xiaoshuang Qian

    2014-12-01

    Full Text Available Oxides (such as SiO2, TiO2, ZrO2, Al2O3, Fe2O3, CeO2 have often been used to prepare supported Pt catalysts for CO oxidation and other reactions, whereas metal phosphate-supported Pt catalysts for CO oxidation were rarely reported. Metal phosphates are a family of metal salts with high thermal stability and acid-base properties. Hydroxyapatite (Ca10(PO46(OH2, denoted as Ca-P-O here also has rich hydroxyls. Here we report a series of metal phosphate-supported Pt (Pt/M-P-O, M = Mg, Al, Ca, Fe, Co, Zn, La catalysts for CO oxidation. Pt/Ca-P-O shows the highest activity. Relevant characterization was conducted using N2 adsorption-desorption, inductively coupled plasma (ICP atomic emission spectroscopy, X-ray diffraction (XRD, transmission electron microscopy (TEM, CO2 temperature-programmed desorption (CO2-TPD, X-ray photoelectron spectroscopy (XPS, and H2 temperature-programmed reduction (H2-TPR. This work furnishes a new catalyst system for CO oxidation and other possible reactions.

  15. Oxygen partial pressure: a key to alloying and discovery in metal oxide--metal eutectic systems

    International Nuclear Information System (INIS)

    Holder, J.D.; Clark, G.W.; Oliver, B.F.

    1978-01-01

    Control of oxygen partial pressure is essential in the directional solidification of oxide--metal eutectic composites by techniques involving gas-solid and gas-liquid interactions. The existence of end components in the eutectic composite is Po 2 sensitive as are melt stoichiometry, solid phase compositions, and vapor losses due to oxidation-volatilization. Simple criteria are postulated which can aid the experimentalist in selecting the proper gas mixture for oxide--metal eutectic composite growth. The Cr 2 O 3 --Mo--Cr systems was used to verify certain aspects of the proposed criteria

  16. Modified Poisson solver for the simulation of the silicon-oxide interface in semiconductor detectors

    Energy Technology Data Exchange (ETDEWEB)

    Castoldi, A. E-mail: andrea.castoldi@polimi.it; Rehak, P.; Gatti, E.; Guazzoni, C.; De Geronimo, G

    2000-01-11

    We present a modified Poisson solver for depleted semiconductor detectors that takes into account the effects of possible accumulation of mobile charge at the silicon-oxide interfaces. The solver is based on a physical model that closely approximates the correct boundary condition at the silicon-oxide interface. The model assumes that the silicon-oxide interface is divided into an equipotential region, where the electron layer is located, and a fully depleted region. The actual extension and potential of the electron layer region are approximated with the desired accuracy by an iterative procedure. This model has been implemented in 2- and 3-D Poisson solvers. The comparison with a 2-D drift-diffusion simulator has shown the accuracy of the proposed method. The modified Poisson solver has shown to be useful in giving accurate solutions to 3-D design problems at high CPU speed.

  17. Modified Poisson solver for the simulation of the silicon-oxide interface in semiconductor detectors

    CERN Document Server

    Castoldi, A; Gatti, E; Guazzoni, C; De Geronimo, G

    2000-01-01

    We present a modified Poisson solver for depleted semiconductor detectors that takes into account the effects of possible accumulation of mobile charge at the silicon-oxide interfaces. The solver is based on a physical model that closely approximates the correct boundary condition at the silicon-oxide interface. The model assumes that the silicon-oxide interface is divided into an equipotential region, where the electron layer is located, and a fully depleted region. The actual extension and potential of the electron layer region are approximated with the desired accuracy by an iterative procedure. This model has been implemented in 2- and 3-D Poisson solvers. The comparison with a 2-D drift-diffusion simulator has shown the accuracy of the proposed method. The modified Poisson solver has shown to be useful in giving accurate solutions to 3-D design problems at high CPU speed.

  18. Sputter-Deposited Oxides for Interface Passivation of CdTe Photovoltaics

    Energy Technology Data Exchange (ETDEWEB)

    Kephart, Jason M.; Kindvall, Anna; Williams, Desiree; Kuciauskas, Darius; Dippo, Pat; Munshi, Amit; Sampath, W. S.

    2018-03-01

    Commercial CdTe PV modules have polycrystalline thin films deposited on glass, and devices made in this format have exceeded 22% efficiency. Devices made by the authors with a magnesium zinc oxide window layer and tellurium back contact have achieved efficiency over 18%, but these cells still suffer from an open-circuit voltage far below ideal values. Oxide passivation layers made by sputter deposition have the potential to increase voltage by reducing interface recombination. CdTe devices with these passivation layers were studied with photoluminescence (PL) emission spectroscopy and time-resolved photoluminescence (TRPL) to detect an increase in minority carrier lifetime. Because these oxide materials exhibit barriers to carrier collection, micropatterning was used to expose small point contacts while still allowing interface passivation. TRPL decay lifetimes have been greatly enhanced for thin polycrystalline absorber films with interface passivation. Device performance was measured and current collection was mapped spatially by light-beam-induced current.

  19. Platinum redispersion on metal oxides in low temperature fuel cells

    DEFF Research Database (Denmark)

    Tripkovic, Vladimir; Cerri, Isotta; Nagami, Tetsuo

    2013-01-01

    We have analyzed the aptitude of several metal oxide supports (TiO2, SnO2, NbO2, ZrO2, SiO2, Ta2O5 and Nb2O5) to redisperse platinum under electrochemical conditions pertinent to the Proton Exchange Membrane Fuel Cell (PEMFC) cathode. The redispersion on oxide supports in air has been studied in ...

  20. Comparative metal oxide nanoparticle toxicity using embryonic zebrafish

    OpenAIRE

    Wehmas, Leah C.; Anders, Catherine; Chess, Jordan; Punnoose, Alex; Pereira, Cliff B.; Greenwood, Juliet A.; Tanguay, Robert L.

    2015-01-01

    Engineered metal oxide nanoparticles (MO NPs) are finding increasing utility in the medical field as anticancer agents. Before validation of in vivo anticancer efficacy can occur, a better understanding of whole-animal toxicity is required. We compared the toxicity of seven widely used semiconductor MO NPs made from zinc oxide (ZnO), titanium dioxide, cerium dioxide and tin dioxide prepared in pure water and in synthetic seawater using a five-day embryonic zebrafish assay. We hypothesized tha...

  1. Improved adhesion of metal oxide layer

    DEFF Research Database (Denmark)

    2012-01-01

    The present invention relates to: a method of preparing a coating ink for forming a zinc oxide layer, which method comprises the steps of: a) mixing zinc acetate and AlOH (OAc)2 in water or methanol and b) filtering out solids; a coating ink comprising zinc acetate and AlOH (OAc)2 in aqueous or m...

  2. Graphene composites containing chemically bonded metal oxides

    Indian Academy of Sciences (India)

    (figure 7). We have also been able to bond Al2O3 to graphene by using AlCl3 as the reactant. The oxide film was amor- phous after calcination at 600. ◦. C. We have prepared chemically bonded magnetic Fe3O4 nanoparticles to graphene by functionalizing Fe3O4 by amine, then reacting it with graphene functionalized with.

  3. Virtual half-metallicity at the CoS2/FeS2 interface induced by strain

    KAUST Repository

    Nazir, Safdar

    2013-01-01

    Spin polarized ab initio calculations based on density functional theory are performed to investigate the electronic and magnetic properties of the interface between the ferromagnetic metal CoS2 and the nonmagnetic semiconductor FeS2. Relaxation of the interface structure is taken into account by atomic force minimization. We find that both Co and Fe are close to half-metallicity at the interface. Tensile strain is shown to strongly enhance the spin polarization so that a virtually half-metallic interface can be achieved, for comparably moderate strain. © 2012 The Royal Society of Chemistry.

  4. Application of metal oxide refractories for melting and casting reactive metals

    International Nuclear Information System (INIS)

    Jessen, N.C. Jr.; Holcombe, C.E. Jr.; Townsend, A.B.

    1979-01-01

    Extensive investigations have been conducted to develop metal oxide refractories for containment of molten uranium and uranium alloys. Since uranium and uranium alloys are readily susceptable to the formation of complex oxides, carbides, nitrides, intermetallic compounds, and suboxide reactions, severe problems exist for the production of quality castings. These contamination reactions are dependent on temperature, pressure, and molten metal interfacial reactions. The need for high purity metals to meet specification repeatedly has resulted in the development of improved metal oxide refractories and sophisticated furnace controls. Applications of Y 2 O 3 for use as a crucible and mold coating, precision molds and cores, and high temperature castable ceramics are discussed. Experimental results on melt impurity levels, thermal controls during melting, surface interactions and casting quality are presented

  5. Flexible Metal Oxide/Graphene Oxide Hybrid Neuromorphic Devices on Flexible Conducting Graphene Substrates

    OpenAIRE

    Wan, Chang Jin; Wang, Wei; Zhu, Li Qiang; Liu, Yang Hui; Feng, Ping; Liu, Zhao Ping; Shi, Yi; Wan, Qing

    2016-01-01

    Flexible metal oxide/graphene oxide hybrid multi-gate neuron transistors were fabricated on flexible graphene substrates. Dendritic integrations in both spatial and temporal modes were successfully emulated, and spatiotemporal correlated logics were obtained. A proof-of-principle visual system model for emulating lobula giant motion detector neuron was investigated. Our results are of great interest for flexible neuromorphic cognitive systems.

  6. Interface strength and degradation of adhesively bonded porous aluminum oxides

    NARCIS (Netherlands)

    Abrahami, S.T.; de Kok, John M.M.; Gudla, Visweswara C.; Ambat, Rajan; Terryn, H.A.; Mol, J.M.C.

    2017-01-01

    For more than six decades, chromic acid anodizing has been the main step in the surface treatment of aluminum for adhesively bonded aircraft structures. Soon this process, known for producing a readily adherent oxide with an excellent corrosion resistance, will be banned by strict international

  7. Time resolved study of hydroxyl radical oxidation of oleic acid at the air-water interface

    Science.gov (United States)

    Zhang, Xinxing; Barraza, Kevin M.; Upton, Kathleen T.; Beauchamp, J. L.

    2017-09-01

    The ubiquity of oleic acid (OA) renders it a poster child for laboratory investigations of environmental oxidation chemistry. In the current study, mechanistic details of the oxidation of OA by hydroxyl radicals at the air-water interface are investigated using field-induced droplet ionization mass spectrometry (FIDI-MS). Products from OH oxidation of both unsaturated and saturated carbon atoms are identified, and mechanisms for both types of oxidation processes are proposed. Uptake of oxygen in the interfacial layer increases linearly with time, consistent with Langmuir-Hinshelwood reaction kinetics. These results provide fundamental knowledge relating to OH initiated degradation of fatty acids in atmospheric aerosols.

  8. Infrared Spectroscopy as Molecular Probe of the Macroscopic Metal-Liquid Interface

    Directory of Open Access Journals (Sweden)

    Johannes Kiefer

    2017-11-01

    Full Text Available Metal-liquid interfaces are of the utmost importance in a number of scientific areas, including electrochemistry and catalysis. However, complicated analytical methods and sample preparation are usually required to study the interfacial phenomena. We propose an infrared spectroscopic approach that enables investigating the molecular interactions at the interface, but needing only minimal or no sample preparation. For this purpose, the internal reflection element (IRE is wetted with a solution as first step. Second, a small plate of the metal of interest is put on top and pressed onto the IRE. The tiny amount of liquid that is remaining between the IRE and the metal is sufficient to produce an IR spectrum with good signal to noise ratio, from which information about molecular interactions, such as hydrogen bonding, can be deduced. Proof-of-concept experiments were carried out with aqueous salt and acid solutions and an aluminum plate.

  9. Visible light sensitive cupric oxide metal-semiconductor-metal photodetectors

    Science.gov (United States)

    Raghavendra, P. V.; Bhat, J. S.; Deshpande, N. G.

    2018-01-01

    The visible light response of Ag-CuO-Ag metal-semiconductor-metal (MSM) photodetector is presented. Electron beam deposited CuO thin films consisted of tightly packed nanocrystallites in monoclinic phase. The observed red-shifts in indirect band-gap from 1.09 eV to 0.99 eV and direct band-gap from 2.92 eV to 2.87 eV, with annealing temperature, is attributed to the weak quantum confinement effect. CuO thin films annealed at 500 °C have a p-type conductivity of 4.33 × 10-2 (ohm-cm)-1 and mobility of 13.2 cm2/V-s. Significant responsivities of 0.33 mA/W and 0.59 mA/W for blue and red lights, respectively, in Ag-CuO-Ag photodetector are illustrative for using it as visible light sensor.

  10. Nanoscale investigation of the interface situation of plated nickel and thermally formed nickel silicide for silicon solar cell metallization

    Science.gov (United States)

    Mondon, A.; Wang, D.; Zuschlag, A.; Bartsch, J.; Glatthaar, M.; Glunz, S. W.

    2014-12-01

    In the context of nickel silicide formation from plated nickel layers for solar cell metallization, there are several open questions regarding contact adhesion and electrical properties. Nanoscale characterization by transmission electron microscopy has been employed to support these investigations. Interfacial oxides and silicide phases were investigated on differently prepared samples by different analytical methods associated with transmission electron microscopy analysis. Processing variations included the pre-treatment of samples before nickel plating, the used plating solution and the thermal budget for the nickel-silicon solid-state reaction. It was shown that interface oxides of only few nm thickness on both silicon and nickel silicide are present on the samples, depending on the chosen process sequence, which have been shown to play an important role in adhesion of nickel on silicide in an earlier publication. From sample pretreatment variations, conclusions about the role of an interfacial oxide in silicide formation and its influence on phase formation were drawn. Such an oxide layer hinders silicide formation except for pinhole sites. This reduces the availability of Ni and causes a silicide with low Ni content to form. Without an interfacial oxide a continuous nickel silicide of greater depth, polycrystalline modification and expected phase according to thermal budget is formed. Information about the nature of silicide growth on typical solar cell surfaces could be obtained from silicide phase and geometric observations, which were supported by FIB tomography. The theory of isotropic NiSi growth and orientation dependent NiSi2 growth was derived. By this, a very well performing low-cost metallization for silicon solar cells has been brought an important step closer to industrial introduction.

  11. All-alkoxide synthesis of strontium-containing metal oxides

    Science.gov (United States)

    Boyle, Timothy J.

    2001-01-01

    A method for making strontium-containing metal-oxide ceramic thin films from a precursor liquid by mixing a strontium neo-pentoxide dissolved in an amine solvent and at least one metal alkoxide dissolved in a solvent, said at least one metal alkoxide selected from the group consisting of alkoxides of calcium, barium, bismuth, cadmium, lead, titanium, tantalum, hafnium, tungsten, niobium, zirconium, yttrium, lanthanum, antimony, chromium and thallium, depositing a thin film of the precursor liquid on a substrate, and heating the thin film in the presence of oxygen at between 550 and 700.degree. C.

  12. Emerging interface dipole versus screening effect in copolymer/metal nano-layered systems

    Energy Technology Data Exchange (ETDEWEB)

    Torrisi, V., E-mail: v.torrisi@unict.it [Laboratory for Molecular Surfaces and Nanotechnology (LAMSUN), Department of Chemical Sciences, University of Catania, Viale A. Doria 6, 95125, Catania (Italy); Ruffino, F. [Dipartimento di Fisica ed Astronomia-Università di Catania, via S. Sofia 64, 95123 Catania (Italy); MATIS IMM-CNR, via S. Sofia 64, 95123 Catania (Italy); Liscio, A. [Istituto per la Sintesi e la Fotoreattività CNR, via Gobetti 101, 40129, Bologna (Italy); Grimaldi, M.G. [Dipartimento di Fisica ed Astronomia-Università di Catania, via S. Sofia 64, 95123 Catania (Italy); MATIS IMM-CNR, via S. Sofia 64, 95123 Catania (Italy); Marletta, G. [Laboratory for Molecular Surfaces and Nanotechnology (LAMSUN), Department of Chemical Sciences, University of Catania, Viale A. Doria 6, 95125, Catania (Italy)

    2015-12-30

    Graphical abstract: - Highlights: • Gold/copolymer multilayered thin films are prepared. • Mapping of the multilayers surface potential are performed by Kelvin Probe Force Microscopy. • Surface potential is controlled by the thickness and the surface coverage of the gold layer. • The work function of the gold layer is influenced by the underlying copolymer layer. - Abstract: Despite to the importance on the charge carrier injection and transport at organic/metal interface, there is yet an incomplete estimation of the various contribution to the overall dipole. This work shows how the mapping of the surface potential performed by Kelvin Probe Force Microscopy (KPFM) allows the direct observation of the interface dipole within an organic/metal multilayered structure. Moreover, we show how the sub-surface sensitivity of the KPFM depends on the thickness and surface coverage of the metallic layer. This paper proposes a way to control the surface potential of the exposed layer of an hybrid layered system by controlling the interface dipole at the organic/metal interface as a function of the nanometer scale thickness and the surface coverage of the metallic layer. We obtained a layered system constituted by repeated sequence of a copolymer film, poly(n-butylacrylate)-b-polyacrilic acid, and Au layer. We compared the results obtained by means of scanning probe microscopy technique with the results of the KPFM technique, that allows us to obtain high-contrast images of the underlying layer of copolymer behind a typical threshold, on the nanoscale, of the thickness of the metal layer. We considered the effect of the morphology of the gold layer on the covered area at different thicknesses by using the scanning electron microscopy technique. This finding represents a step forward towards the using of dynamic atomic force microscopy based characterization to explore the electrical properties of the sub-surface states of layered nanohybrid, that is a critical point for

  13. Precipitation of Niobium Boride Phases at the Base Metal/Weld Metal Interface in Dissimilar Weld Joints

    Science.gov (United States)

    Výrostková, Anna; Kepič, Ján; Homolová, Viera; Falat, Ladislav

    2015-07-01

    In this work, the analysis of failure mechanism in the heat affected zone is described in dissimilar weld joints between advanced martensitic steel T92 and Ni-base weld metal. The joints were treated with two different post-weld heat treatments and tested. For the creep, tensile, and Charpy impact tests, the samples with interfacially located notch were used. Moreover long term aging at 625 °C was applied before the tensile and notch toughness tests. Decohesion fractures ran along carbides at the T92 BM/WM interfaces in case of the modified PWHT, whereas type IV cracking was the prevailing failure mechanism after the classical PWHT in the creep test. In the notch tensile and Charpy impact tests, with the notch at T92 base metal/weld metal interface, fractures ran along the interface with a hard phase on the fracture surface along with the ductile dimple and brittle quasi-cleavage fracture. The phase identified as niobium boride (either NbB and/or Nb3B2) was produced during welding at the end of the solidification process. It was found in the welds regardless of the post-weld heat treatment and long-term aging.

  14. A comparison of ionizing radiation and high field stress effects in n-channel power vertical double-diffused metal-oxide-semiconductor field-effect transistors

    International Nuclear Information System (INIS)

    Park, Mun-Soo; Na, Inmook; Wie, Chu R.

    2005-01-01

    n-channel power vertical double-diffused metal-oxide-semiconductor field-effect-transistor (VDMOSFET) devices were subjected to a high electric field stress or to a x-ray radiation. The current-voltage and capacitance-voltage measurements show that the channel-side interface and the drain-side interface are affected differently in the case of high electric field stress, whereas the interfaces are nearly uniformly affected in the case of x-ray radiation. This paper also shows that for the gated diode structure of VDMOSFET, the direct-current current-voltage technique measures only the drain-side interface; the subthreshold current-voltage technique measures only the channel-side interface; and the capacitance-voltage technique measures both interfaces simultaneously and clearly distinguishes the two interfaces. The capacitance-voltage technique is suggested to be a good quantitative method to examine both interface regions by a single measurement

  15. Single sheet metal oxides and hydroxides

    DEFF Research Database (Denmark)

    Huang, Lizhi

    The synthesis of layered double hydroxides (LDHs) provides a relatively easy and traditional way to build versatile chemical compounds with a rough control of the bulk structure. The delamination of LDHs to form their single host layers (2D nanosheets) and the capability to reassemble them offer ......) Delamination of the LDHs structure (oxGRC12) with the formation of single sheet iron (hydr)oxide (SSI). (3) Assembly of the new 2D nanosheets layer by layer to achieve desired functionalities....

  16. Oxidation kinetics of reaction products formed in uranium metal corrosion

    International Nuclear Information System (INIS)

    Totemeier, T. C.

    1998-01-01

    The oxidation behavior of uranium metal ZPPR fuel corrosion products in environments of Ar-4%O 2 and Ar-20%O 2 were studied using thermo-gravimetric analysis (TGA). These tests were performed to extend earlier work in this area specifically, to assess plate-to-plate variations in corrosion product properties and the effect of oxygen concentration on oxidation behavior. The corrosion products from two relatively severely corroded plates were similar, while the products from a relatively intact plate were not reactive. Oxygen concentration strongly affected the burning rate of reactive products, but had little effect on low-temperature oxidation rates

  17. Oxidation of limonene catalyzed by Metal(Salen) complexes

    OpenAIRE

    Lima, L. F.; Corraza, M. L.; Cardozo-Filho, L.; Márquez-Alvarez, H.; Antunes, O. A. C.

    2006-01-01

    The compound R-(+)limonene is available and cheap than its oxidized products. Consequently, the selective oxidation of R(+)limonene has attracted attention as a promising process for the production of compounds with a higher market value, such as cis/trans-1,2-limoneneoxide, cis/trans-carveol and/or carvone. One of the these processes, described in the recent literature, is submission of R-(+)limonene to an oxidation reaction catalyzed by neutral or cationic Metal(Salen) complexes, in the pre...

  18. Carbon monoxide oxidation over three different states of copper: Development of a model metal oxide catalyst

    Energy Technology Data Exchange (ETDEWEB)

    Jernigan, Glenn Geoffrey [California Univ., Berkeley, CA (United States). Dept. of Chemistry

    1994-10-01

    Carbon monoxide oxidation was performed over the three different oxidation states of copper -- metallic (Cu), copper (I) oxide (Cu2O), and copper (II) oxide (CuO) as a test case for developing a model metal oxide catalyst amenable to study by the methods of modern surface science and catalysis. Copper was deposited and oxidized on oxidized supports of aluminum, silicon, molybdenum, tantalum, stainless steel, and iron as well as on graphite. The catalytic activity was found to decrease with increasing oxidation state (Cu > Cu2O > CuO) and the activation energy increased with increasing oxidation state (Cu, 9 kcal/mol < Cu2O, 14 kcal/mol < CuO, 17 kcal/mol). Reaction mechanisms were determined for the different oxidation states. Lastly, NO reduction by CO was studied. A Cu and CuO catalyst were exposed to an equal mixture of CO and NO at 300--350 C to observe the production of N2 and CO2. At the end of each reaction, the catalyst was found to be Cu2O. There is a need to study the kinetics of this reaction over the different oxidation states of copper.

  19. Unipolar resistive switching in metal oxide/organic semiconductor non-volatile memories as a critical phenomenon

    International Nuclear Information System (INIS)

    Bory, Benjamin F.; Meskers, Stefan C. J.; Rocha, Paulo R. F.; Gomes, Henrique L.; Leeuw, Dago M. de

    2015-01-01

    Diodes incorporating a bilayer of an organic semiconductor and a wide bandgap metal oxide can show unipolar, non-volatile memory behavior after electroforming. The prolonged bias voltage stress induces defects in the metal oxide with an areal density exceeding 10 17  m −2 . We explain the electrical bistability by the coexistence of two thermodynamically stable phases at the interface between an organic semiconductor and metal oxide. One phase contains mainly ionized defects and has a low work function, while the other phase has mainly neutral defects and a high work function. In the diodes, domains of the phase with a low work function constitute current filaments. The phase composition and critical temperature are derived from a 2D Ising model as a function of chemical potential. The model predicts filamentary conduction exhibiting a negative differential resistance and nonvolatile memory behavior. The model is expected to be generally applicable to any bilayer system that shows unipolar resistive switching

  20. Carbothermic Reduction Reactions at the Metal-Slag Interface in Ti-Bearing Slag from a Blast Furnace

    Science.gov (United States)

    Wang, Yao-Zu; Zhang, Jian-Liang; Liu, Zheng-Jian; Du, Cheng-Bo

    2017-11-01

    Carbothermic reduction reactions at the metal-slag interface and the mechanisms of iron loss during the smelting of vanadium-bearing titanomagnetite in a blast furnace are still not clear as a result of the limited ability to observe the high-temperature zone of a blast furnace. The chemical composition of a Ti-bearing slag was determined by x-ray fluorescence and x-ray diffraction. The interfaces were characterized by scanning electron microscopy coupled with energy-dispersive x-ray spectroscopy. The interfacial chemical reactions were deduced based on the characterization results and on the thermodynamic calculations performed using Factsage 6.4. The results indicated that the forms of iron in the slag were iron droplets wetted by Ti(C x , N1- x ), mechanically separated by iron and iron oxide. The different forms possessed unique characteristics and were formed by different mechanisms. Iron droplets wetted by Ti(C x , N1- x ) were generated through a series of interfacial reactions between TiO2 in the slag and [C] and [N] in the metal. Iron droplets without attached Ti(C x , N1- x ) were mainly located on the edges of pores and were attributed to the reduction of Fe x O in the slag. Insufficient reduction of iron-bearing minerals made it difficult for iron droplets to aggregate and separate from the slag, which created an Fe x O-enriched zone.

  1. Interface States Densities Effect at SiO2/ Polysilicon and SiO2/ Monosilicon Surfaces on N-polysilicon /Oxide/ P-Monosilicon Capacitance

    Directory of Open Access Journals (Sweden)

    H. Dib

    2014-05-01

    Full Text Available the interface states have a very significant role in the components containing MOS structures. In this paper we study the interface states densities effect at SiO2/ N-polysilicon and SiO2/ P- monosilicon surfaces on metal/polysilicon /oxide/ monosilicon capacitance. The numerical solution of poisson's equation and the determination of the charge variation in the structure induced by application of external bias (Vg allow simulating the capacitance-voltage MSPOS characteristics. The results show that the interface states at SiO2/ polysilicon and SiO2/ monosilicon surfaces translate the CT (V curve about positive voltage and cause the increase of the minimum value of capacitance. The effect of interface states on C (V curves is neglected for the polysilicon doping concentration in order to 1019 cm-3. For this doping level, the C (V curves are identical to the C (V of the monocristalline MOS structure.

  2. Electrochemical activity of heavy metal oxides in the process of ...

    Indian Academy of Sciences (India)

    Alloys and Steels Volume 25 Issue 5 October 2002 pp 371-373 ... The influence of heavy metal oxides on the chloride induced corrosion of steel reinforcement in concrete was studied. ... Institute of Construction and Architecture of the Slovak Academy of Sciences, Dúbravská cesta 9, 842 20 Bratislava, Slovak Republic ...

  3. Metal complexes of substituted Gable porphyrins as oxidation catalysts

    Science.gov (United States)

    Lyons, James E.; Ellis, Jr., Paul E.; Wagner, Richard W.

    1996-01-01

    Transition metal complexes of Gable porphyrins having two porphyrin rings connected through a linking group, and having on the porphyrin rings electron-withdrawing groups, such as halogen, nitro or cyano. These complexes are useful as catalysts for the oxidation of organic compounds, e.g. alkanes.

  4. Metal-free oxidative coupling of thiols to disulfides using ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Chemical Sciences; Volume 123; Issue 4. Metal-free oxidative coupling of thiols to disulfides using guanidinium nitrate or nitro urea in the presence of silica sulfuric acid. Arash Ghorbani-Choghamarani Mohsen Nikoorazm Hamid Goudarziafshar Alireza Shokr Hosein Almasi. Volume 123 Issue 4 ...

  5. Nanostructured Metal Oxides for Stoichiometric Degradation of Chemical Warfare Agents

    Czech Academy of Sciences Publication Activity Database

    Štengl, Václav; Henych, Jiří; Janos, P.; Skoumal, M.

    2016-01-01

    Roč. 236, č. 2016 (2016), s. 239-258 ISSN 0179-5953 R&D Projects: GA ČR(CZ) GAP106/12/1116 Institutional support: RVO:61388980 Keywords : chemical warfare agent * metal nanoparticle * unique surface-chemistry * mesoporous manganese oxide Subject RIV: CA - Inorganic Chemistry Impact factor: 3.930, year: 2016

  6. A novel parameter estimation method for metal oxide surge arrester ...

    Indian Academy of Sciences (India)

    Accurate modelling and exact determination of Metal Oxide (MO) surge arrester parameters are very important for arrester allocation, insulation coordination studies and systems reliability calculations. In this paper, a new technique, which is the combination of Adaptive Particle Swarm Optimization (APSO) and Ant Colony ...

  7. Metal oxide blended ZSM-5 nanocomposites as ethanol sensors

    Indian Academy of Sciences (India)

    Nano-ZSM-5 is synthesized without organic template via microwave-assisted hydrothermal technique. The synthesized nano-ZSM-5 zeolite is blended with metal oxides (ZnO and TiO 2 ) to have novel composites as ethanol sensors. The composites are characterized by X-ray diffraction (XRD) and Fourier transform infrared ...

  8. Anti-Oxidative, Metal Chelating and Radical Scavenging Effects of ...

    African Journals Online (AJOL)

    Purpose: To evaluate protein hydrolysates and membrane ultrafiltration fractions of blue-spotted stingray for metal chelating and radical scavenging activities, as well as protection against oxidative protein damage. Methods: Stingray protein isolates were hydrolysed with alcalase, papain and trypsin for 3 h. Alcalase.

  9. Metal oxide/polyaniline nanocomposites: Cluster size and ...

    Indian Academy of Sciences (India)

    Wintec

    report preliminary results on the magnetic properties of self standing sheets prepared using γ-Fe2O3 and. NiFe2O4 nanoparticles and conducting polymers. Keywords. Metal oxide/polyaniline nanocomposites; structural properties; magnetic properties. 1. Introduction. The diverse properties of magnetic nanoparticle systems.

  10. Single-photon imaging in complementary metal oxide semiconductor processes

    NARCIS (Netherlands)

    Charbon, E.

    2014-01-01

    This paper describes the basics of single-photon counting in complementary metal oxide semiconductors, through single-photon avalanche diodes (SPADs), and the making of miniaturized pixels with photon-counting capability based on SPADs. Some applications, which may take advantage of SPAD image

  11. A review of liquid metal anode solid oxide fuel cells

    Directory of Open Access Journals (Sweden)

    ALIYA TOLEUOVA

    2013-06-01

    Full Text Available This review discusses recent advances in a solid oxide fuel cell (SOFC variant that uses liquid metal electrodes (anodes with the advantage of greater fuel tolerance and the ability to operate on solid fuel. Key features of the approach are discussed along with the technological and research challenges that need to be overcome for scale-up and commercialisation.

  12. Metal oxide blended ZSM-5 nanocomposites as ethanol sensors

    Indian Academy of Sciences (India)

    ges quality monitoring, environmental monitoring, indoor air quality and breath analysis [16]. It is due to the great demand in diverse fields, that the search for new ethanol sensor mate- rials is still needed. Literature survey reveals the sparseness in research based on metal oxide blended zeolite gas sensors. Hence in this ...

  13. Actinomycetes-mediated biogenic synthesis of metal and metal oxide nanoparticles: progress and challenges.

    Science.gov (United States)

    Manimaran, M; Kannabiran, K

    2017-06-01

    Actinomycetes-mediated biogenic synthesis of metal nanoparticles and their antimicrobial activities are well documented. Actinomycetes facilitate both intracellular and extracellular metal nanoparticles synthesis and are efficient candidates for the production of polydispersed, stable and ultra-small size metal nanoparticles. Secondary metabolites and new chemical entities derived from Actinomycetes have not been extensively studied for the synthesis of metal/metal oxide nanoparticles. The present review focuses on biogenic synthesis of metal nanoparticles from Actinomycetes and the scope for exploring Actinomycetes-derived compounds (enzymes, organics acids and bioactive compounds) as metal and metal oxide reducing agents for the synthesis of desired nanoparticles. This review also focuses on challenges faced in the applications of nanoparticles and the methods to synthesize biogenic metal nanoparticles with desired physiochemical properties such as ultra-small size, large surface to mass ratio, high reactivity etc. Methods to evade their toxicity and unique interactions with biological systems to improve their chance as an alternative therapeutic agent in medical and pharmaceutical industry are also discussed. © 2017 The Society for Applied Microbiology.

  14. Metal oxide semiconductor thin-film transistors for flexible electronics

    Science.gov (United States)

    Petti, Luisa; Münzenrieder, Niko; Vogt, Christian; Faber, Hendrik; Büthe, Lars; Cantarella, Giuseppe; Bottacchi, Francesca; Anthopoulos, Thomas D.; Tröster, Gerhard

    2016-06-01

    The field of flexible electronics has rapidly expanded over the last decades, pioneering novel applications, such as wearable and textile integrated devices, seamless and embedded patch-like systems, soft electronic skins, as well as imperceptible and transient implants. The possibility to revolutionize our daily life with such disruptive appliances has fueled the quest for electronic devices which yield good electrical and mechanical performance and are at the same time light-weight, transparent, conformable, stretchable, and even biodegradable. Flexible metal oxide semiconductor thin-film transistors (TFTs) can fulfill all these requirements and are therefore considered the most promising technology for tomorrow's electronics. This review reflects the establishment of flexible metal oxide semiconductor TFTs, from the development of single devices, large-area circuits, up to entirely integrated systems. First, an introduction on metal oxide semiconductor TFTs is given, where the history of the field is revisited, the TFT configurations and operating principles are presented, and the main issues and technological challenges faced in the area are analyzed. Then, the recent advances achieved for flexible n-type metal oxide semiconductor TFTs manufactured by physical vapor deposition methods and solution-processing techniques are summarized. In particular, the ability of flexible metal oxide semiconductor TFTs to combine low temperature fabrication, high carrier mobility, large frequency operation, extreme mechanical bendability, together with transparency, conformability, stretchability, and water dissolubility is shown. Afterward, a detailed analysis of the most promising metal oxide semiconducting materials developed to realize the state-of-the-art flexible p-type TFTs is given. Next, the recent progresses obtained for flexible metal oxide semiconductor-based electronic circuits, realized with both unipolar and complementary technology, are reported. In particular

  15. Metal oxide semiconductor thin-film transistors for flexible electronics

    Energy Technology Data Exchange (ETDEWEB)

    Petti, Luisa; Vogt, Christian; Büthe, Lars; Cantarella, Giuseppe; Tröster, Gerhard [Electronics Laboratory, Swiss Federal Institute of Technology, Zürich (Switzerland); Münzenrieder, Niko [Electronics Laboratory, Swiss Federal Institute of Technology, Zürich (Switzerland); Sensor Technology Research Centre, University of Sussex, Falmer (United Kingdom); Faber, Hendrik; Bottacchi, Francesca; Anthopoulos, Thomas D. [Department of Physics and Centre for Plastic Electronics, Imperial College London, London (United Kingdom)

    2016-06-15

    The field of flexible electronics has rapidly expanded over the last decades, pioneering novel applications, such as wearable and textile integrated devices, seamless and embedded patch-like systems, soft electronic skins, as well as imperceptible and transient implants. The possibility to revolutionize our daily life with such disruptive appliances has fueled the quest for electronic devices which yield good electrical and mechanical performance and are at the same time light-weight, transparent, conformable, stretchable, and even biodegradable. Flexible metal oxide semiconductor thin-film transistors (TFTs) can fulfill all these requirements and are therefore considered the most promising technology for tomorrow's electronics. This review reflects the establishment of flexible metal oxide semiconductor TFTs, from the development of single devices, large-area circuits, up to entirely integrated systems. First, an introduction on metal oxide semiconductor TFTs is given, where the history of the field is revisited, the TFT configurations and operating principles are presented, and the main issues and technological challenges faced in the area are analyzed. Then, the recent advances achieved for flexible n-type metal oxide semiconductor TFTs manufactured by physical vapor deposition methods and solution-processing techniques are summarized. In particular, the ability of flexible metal oxide semiconductor TFTs to combine low temperature fabrication, high carrier mobility, large frequency operation, extreme mechanical bendability, together with transparency, conformability, stretchability, and water dissolubility is shown. Afterward, a detailed analysis of the most promising metal oxide semiconducting materials developed to realize the state-of-the-art flexible p-type TFTs is given. Next, the recent progresses obtained for flexible metal oxide semiconductor-based electronic circuits, realized with both unipolar and complementary technology, are reported. In

  16. Radiation effects in metal-oxide-semiconductor capacitors

    International Nuclear Information System (INIS)

    Collins, J.L.

    1987-01-01

    The effects of various radiations on commercially made Al-SiO 2 -Si Capacitors (MOSCs) have been investigated. Intrinsic dielectric breakdown in MOSCs has been shown to be a two-stage process dominated by charge injection in a pre-breakdown stage; this is associated with localised high-field injection of carriers from the semiconductor substrate to interfacial and bulk charge traps which, it is proposed, leads to the formation of conducting channels through the dielectric with breakdown occurring as a result of the dissipation of the conduction band energy. A study of radiation-induced dielectric breakdown has revealed the possibility of anomalous hot-electron injection to an excess of bulk oxide traps in the ionization channel produced by very heavily ionizing radiation, which leads to intrinsic breakdown in high-field stressed devices. This is interpreted in terms of a modified model for radiation-induced dielectric breakdown based upon the primary dependence of breakdown on charge injection rather than high-field mechanisms. A detailed investigation of charge trapping and interface state generation due to various radiations has revealed evidence of neutron induced interface states, and the generation of positive oxide charge in devices due to all the radiations tested. The greater the linear energy transfer of the radiation, the greater the magnitude of charge trapped in the oxide and the number of interface states generated. This is interpreted in terms of Si-H and Si-OH bond-breaking at the Si-SiO 2 interface which is enhanced by charge carrier transfer to the interface and by anomalous charge injection to compensate for the excess of charge carriers created by the radiation. (author)

  17. Toward a Quantitative Understanding of the Electric Field in Thermal Metal Oxidation and a Self-Consistent Wagner Theory.

    Science.gov (United States)

    Cheng, Tian-Le; Wen, You-Hai

    2014-07-03

    The electric field in the growing oxide film is important to the kinetics and mechanism of metal oxidation. However, understanding of the essential characteristics of the electric field during oxidation remains insufficient. A special-case analytical model is presented that provides a unified understanding for the electric field from the viewpoints of kinetics and thermodynamics. More general cases are studied by computer simulations that show similar characteristics in the electric field. In particular, simulations indicate that in many situations, the electrostatic potential drop across the bulk oxide is limited to ∼kBT/e, which means that the total electrostatic potential drop across the oxide film, if on the order of 1 V by rough estimation, should have contributions mostly from the electrified interfaces. Finally, regarding the Gibbs-Duhem relation, the commonly used isobaric assumption for the diffusing species is refuted. The results contained herein also provide a self-consistent understanding of Wagner's oxidation theory.

  18. Platinum redispersion on metal oxides in low temperature fuel cells.

    Science.gov (United States)

    Tripković, Vladimir; Cerri, Isotta; Nagami, Tetsuo; Bligaard, Thomas; Rossmeisl, Jan

    2013-03-07

    We have analyzed the aptitude of several metal oxide supports (TiO(2), SnO(2), NbO(2), ZrO(2), SiO(2), Ta(2)O(5) and Nb(2)O(5)) to redisperse platinum under electrochemical conditions pertinent to the Proton Exchange Membrane Fuel Cell (PEMFC) cathode. The redispersion on oxide supports in air has been studied in detail; however, due to different operating conditions it is not straightforward to link the chemical and the electrochemical environment. The largest differences reflect in (1) the oxidation state of the surface (the oxygen species coverage), (2) temperature and (3) the possibility of platinum dissolution at high potentials and the interference of redispersion with normal working potential of the PEMFC cathode. We have calculated the PtO(x) (x = 0, 1, 2) adsorption energies on different metal oxides' surface terminations as well as inside the metal oxides' bulk, and we have concluded that NbO(2) might be a good support for platinum redispersion at PEMFC cathodes.

  19. Adhesive, abrasive and oxidative wear in ion-implanted metals

    International Nuclear Information System (INIS)

    Dearnaley, G.

    1985-01-01

    Ion implantation is increasingly being used to provide wear resistance in metals and cemented tungsten carbides. Field trials and laboratory tests indicate that the best performance is achieved in mild abrasive wear. This can be understood in terms of the classification of wear modes (adhesive, abrasive, oxidative etc.) introduced by Burwell. Surface hardening and work hardenability are the major properties to be enhanced by ion implantation. The implantation of nitrogen or dual implants of metallic and interstitial species are effective. Recently developed techniques of ion-beam-enhanced deposition of coatings can further improve wear resistance by lessening adhesion and oxidation. In order to support such hard coatings, ion implantation of nitrogen can be used as a preliminary treatment. There is thus emerging a versatile group of related hard vacuum treatments involving intense beams of nitrogen ions for the purpose of tailoring metal surfaces to resist wear. (Auth.)

  20. Electrocatalytic Applications of Graphene–Metal Oxide Nanohybrid Materials

    DEFF Research Database (Denmark)

    Halder, Arnab; Zhang, Minwei; Chi, Qijin

    2016-01-01

    of cutting-edge developments in graphene–metal oxide nanohybrid materials, with the recently reported results from worldwide research groups. This chapter is presented first with an introduction, followed by synthetic meth‐ ods and structural characterization of nanocomposites, an emphasis......Development of state-of-the-art electrocatalysts using commercially available precursors with low cost is an essential step in the advancement of next-generation electrochemical energy storage/conversion systems. In this regard, noble metal-free and graphene-sup‐ ported nanocomposites...... of graphenebased composite materials, graphene–metal oxide nanohybrids hold great promise to‐ ward engineering efficient electrocatalysts and have attracted increasing interest in both scientific communities and industrial partners around the world. The goal of this chapter is primarily set on an overview...

  1. Phonon Contribution to Thermal Boundary Conductance at Metal Interfaces Using Embedded Atom Method Simulations

    Science.gov (United States)

    Salaway, R. N.; Hopkins, P. E.; Norris, P. M.; Stevens, R. J.

    2008-12-01

    The phonon contribution to the thermal boundary conductance (TBC) at metal-metal interfaces is difficult to study experimentally, and it is typically considered negligible. In this study, molecular dynamics simulations (MDS), employing an embedded atom method (EAM) potential, are performed to study the phonon contribution to thermal transport across an Al-Cu interface. The embedded atom method provides a realistic model of atomic behavior in metals, while suppressing the effect on conduction electrons. In this way, measurements on the phonon system may be observed that would otherwise be dominated by the electron contribution in experimental methods. The relative phonon contribution to the TBC is calculated by comparing EAM results to previous experimental results which include both electron and phonon contributions. It is seen from the data that the relative phonon contribution increases with decreasing temperature, possibly accounting for more than half the overall TBC at temperatures below 100 K. These results suggest that neglect of interfacial phonon transport may not be a valid assumption at low temperatures, and may have implications in the future development of TBC models for metal interfaces.

  2. Influence of semiconductor/metal interface geometry in an EMR sensor

    KAUST Repository

    Sun, Jian

    2013-02-01

    The extraordinary magnetoresistance (EMR) is well known to be strongly dependent on geometric parameters. While the influence of the aspect ratios of the metal and semiconductor areas has been thoroughly investigated, the geometry of the semiconductor/metal interface has been neglected so far. However, from a fabrication point of view, this part plays a crucial role. In this paper, the performance of a bar-type hybrid EMR sensor is investigated by means of finite element method and experiments with respect to the hybrid interface geometry. A 3-D model has been developed, which simulates the EMR effect in case of fields in different directions. The semiconductor/metal interface has been investigated in terms of different layer thicknesses and overlaps. The results show that those parameters can cause a change in the output sensitivity of 2%-10%. In order to maintain a high sensitivity and keep the fabrication relatively simple and at low cost, a device with a thin metal shunt having a large overlap on the top of the semiconductor bar would provide the best solution. © 2001-2012 IEEE.

  3. Magnetotransport investigations of the two-dimensional metallic state in silicon metal-oxid-semiconductor structures

    International Nuclear Information System (INIS)

    Prinz, A.

    2002-03-01

    For more than two decades it was the predominant view among the physical community that the every two-dimensional (2D) disordered electron system becomes insulating as the temperature approaches the absolute zero temperature (0 Kelvin or -273.15 o C). Two-dimensional means that the movement of the charge carriers is confined in one direction by a potential so that the carriers can move freely only perpendicular to the confinement. The most famous physical realization of a 2D system is the silicon metal-oxide-semiconductor field effect transistor (Si-MOSFET). It is one of the basic elements of most electronic devices in our daily life. The working principle is very simple. Charges are attracted to the semiconductor-oxide interface by an electric field applied between the metallic gate and the semiconductor, so that a 2D conductive channel is formed. The charge density can be adjusted by the voltage from zero up to 10 13 cm -2 . In 1994 Kravchenko and coworkers made a very important discovery. They studied high mobility Si-MOSFETs and found that for densities below a certain critical value, nc, the resistivity increases as the temperature is decreased below 2 K, whereas for densities above $n c $ the resistivity decreases unexpectedly. The transition from insulating to metallic behavior, known as metal-insulator transition (MIT), was obviously a contradiction to the commonly accepted theories which predict insulating behavior for any density. The insulating behavior is a consequence of the wave properties of electrons which leads to interference in disordered media and thus to enhanced backscattering. In the subsequent years, experimental studies were performed on a variety of 2D systems, which qualitatively showed a similar behavior. All the investigated samples had one thing in common. The interaction energy between the carriers was considerable higher than their mean kinetic energy due to their movement in the 2D plane. Since the electron-electron interaction was

  4. Atomic Scale Chemical and Structural Characterization of Ceramic Oxide Heterostructure Interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Singh, R. K.

    2003-04-16

    The research plan was divided into three tasks: (a) growth of oxide heterostructures for interface engineering using standard thin film deposition techniques, (b) atomic level characterization of oxide heterostructure using such techniques as STEM-2 combined with AFM/STM and conventional high-resolution microscopy (HRTEM), and (c) property measurements of aspects important to oxide heterostructures using standard characterization methods, including dielectric properties and dynamic cathodoluminescence measurements. Each of these topics were further classified on the basis of type of oxide heterostructure. Type I oxide heterostructures consisted of active dielectric layers, including the materials Ba{sub x}Sr{sub 1-x}TiO{sub 3} (BST), Y{sub 2}O{sub 3} and ZrO{sub 2}. Type II heterostructures consisted of ferroelectric active layers such as lanthanum manganate and Type III heterostructures consist of phosphor oxide active layers such as Eu-doped Y{sub 2}O{sub 3}.

  5. Analysis of the Metals in Soil-Water Interface in a Manganese Mine

    Directory of Open Access Journals (Sweden)

    Bozhi Ren

    2015-01-01

    Full Text Available In order to reveal the influence of the metals of soil-water interface in a manganese mine (Xiangtan, China, on local water environment, there are six kinds of metals (Mn, Ni, Cu, Zn, Cd, and Pb characterized by measuring their concentration, correlation, source, and special distribution using principal component analysis, single factor, and Nemero comprehensive pollution index. The results showed that the corresponding average concentration was 0.3358, 0.045, 0.0105, 0.0148, 0.0067, and 0.0389 mg/L. The logarithmic concentration of Mn, Zn, and Pb was normal distribution. The correlation coefficients (between Mn and Pb, Mn and Zn, Mn and Ni, Cu and Zn, Cu and Pb, and Zn and Cd were found to range from 0.5 to 0.6, and those between Cu and Ni and Cu and Cd were below 0.3. It was found that Zn and Mn pollution were caused primarily by ore mining, mineral waste transportation, tailing slag, and smelting plants, while Cu and Ni mainly originate from the mining industry activities and the traffic transportation in the mining area. In addition, the Cd was considered to be produced primarily from the agricultural or anthropogenic activities. The pollution indexes indicated that metal pollution degree was different in soil-water interface streams as listed in increasing order of pollution level as Zn > Ni > Cu > Pb > Mn > Cd. For all of the pollution of the soil-water interface streams, there was moderate metal pollution but along the eastern mine area the pollution seemed to get more serious. There was only a small amount of soil-water interface streams not contaminated by the metals.

  6. Nanoscale investigation of the interface situation of plated nickel and thermally formed nickel silicide for silicon solar cell metallization

    Energy Technology Data Exchange (ETDEWEB)

    Mondon, A., E-mail: andrew.mondon@ise.fraunhofer.de [Fraunhofer ISE, Heidenhofst. 2, D-79110 Freiburg (Germany); Wang, D. [Karlsruhe Nano Micro Facility (KNMF), H.-von-Helmholz-Platz 1, D-76344 Eggenstein-Leopoldshafen (Germany); Zuschlag, A. [Universität Konstanz FB Physik, Jacob-Burckhardt-Str. 27, D-78464 Konstanz (Germany); Bartsch, J.; Glatthaar, M.; Glunz, S.W. [Fraunhofer ISE, Heidenhofst. 2, D-79110 Freiburg (Germany)

    2014-12-30

    Highlights: • Adhesion of metallization of fully plated nickel–copper contacts on silicon solar cells can be achieved by formation of nickel silicide at the cost of degraded cell performance. • Understanding of silicide growth mechanisms and controlled growth may lead to high performance together with excellent adhesion. • Silicide formation is well known from CMOS production from PVD-Ni on flat surfaces. Yet the deposition methods and therefore layer characteristics and the surface topography are different for plated metallization. • TEM analysis is performed for differently processed samples. • A nickel silicide growth model is created for plated Ni on textured silicon solar cells. - Abstract: In the context of nickel silicide formation from plated nickel layers for solar cell metallization, there are several open questions regarding contact adhesion and electrical properties. Nanoscale characterization by transmission electron microscopy has been employed to support these investigations. Interfacial oxides and silicide phases were investigated on differently prepared samples by different analytical methods associated with transmission electron microscopy analysis. Processing variations included the pre-treatment of samples before nickel plating, the used plating solution and the thermal budget for the nickel–silicon solid-state reaction. It was shown that interface oxides of only few nm thickness on both silicon and nickel silicide are present on the samples, depending on the chosen process sequence, which have been shown to play an important role in adhesion of nickel on silicide in an earlier publication. From sample pretreatment variations, conclusions about the role of an interfacial oxide in silicide formation and its influence on phase formation were drawn. Such an oxide layer hinders silicide formation except for pinhole sites. This reduces the availability of Ni and causes a silicide with low Ni content to form. Without an interfacial oxide

  7. Interface Trap Density Reduction for Al2O3/GaN (0001) Interfaces by Oxidizing Surface Preparation prior to Atomic Layer Deposition.

    Science.gov (United States)

    Zhernokletov, Dmitry M; Negara, Muhammad A; Long, Rathnait D; Aloni, Shaul; Nordlund, Dennis; McIntyre, Paul C

    2015-06-17

    We correlate interfacial defect state densities with the chemical composition of the Al2O3/GaN interface in metal-oxide-semiconductor (MOS) structures using synchrotron photoelectron emission spectroscopy (PES), cathodoluminescence and high-temperature capacitance-voltage measurements. The influence of the wet chemical pretreatments involving (1) HCl+HF etching or (2) NH4OH(aq) exposure prior to atomic layer deposition (ALD) of Al2O3 were investigated on n-type GaN (0001) substrates. Prior to ALD, PES analysis of the NH4OH(aq) treated surface shows a greater Ga2O3 component compared to either HCl+HF treated or as-received surfaces. The lowest surface concentration of oxygen species is detected on the acid etched surface, whereas the NH4OH treated sample reveals the lowest carbon surface concentration. Both surface pretreatments improve electrical characteristics of MOS capacitors compared to untreated samples by reducing the Al2O3/GaN interface state density. The lowest interfacial trap density at energies in the upper band gap is detected for samples pretreated with NH4OH. These results are consistent with cathodoluminescence data indicating that the NH4OH treated samples show the strongest band edge emission compared to as-received and acid etched samples. PES results indicate that the combination of reduced carbon contamination while maintaining a Ga2O3 interfacial layer by NH4OH(aq) exposure prior to ALD results in fewer interface traps after Al2O3 deposition on the GaN substrate.

  8. Volatile organometallic complexes suitable for use in chemical vapor depositions on metal oxide films

    Science.gov (United States)

    Giolando, Dean M.

    2003-09-30

    Novel ligated compounds of tin, titanium, and zinc are useful as metal oxide CVD precursor compounds without the detriments of extreme reactivity yet maintaining the ability to produce high quality metal oxide coating by contact with heated substrates.

  9. The electrochemical transfer reactions and the structure of the iron|oxide layer|electrolyte interface

    International Nuclear Information System (INIS)

    Petrović, Željka; Metikoš-Huković, Mirjana; Babić, Ranko

    2012-01-01

    The thickness, barrier (protecting) and semiconducting properties of the potentiostatically formed oxide films on the pure iron electrode in an aqueous borate buffer solution were investigated by electrochemical quartz crystal nanobalance (EQCN), electrochemical impedance spectroscopy (EIS), and Mott–Schottky (MS) analysis. The thicknesses of the prepassive Fe(II)hydroxide layer (up to monolayer) nucleated on the bare iron surface and the passive Fe(II)/Fe(III) layer (up to 2 nm), deposited on the top of the first one, were determined using in situ gravimetry. Electronic properties of iron prepassive and passive films as well as ionic and electronic transfer reactions at the film|solution interface were discussed on the basis of a band structure model of the surface oxide film and the potential distribution at the interface. The anodic oxide film formation and cathodic decomposition are coupled processes and their reversible inter-conversion is mediated by the availability of free charge carriers on the electrode|solution interface. The structure of the reversible double layer at the iron oxide|solution interface was discussed based on the concept of the specific adsorption of the imidazolium cation on the negatively charged electrode surface at pH > pH pzc .

  10. Interface engineering for oxide electronics: tuning electronic properties by atomically controlled growth

    NARCIS (Netherlands)

    Huijben, Mark

    2006-01-01

    The main aim of this thesis is to develop a controlled growth with atomic precision for the realization of artificial perovskite structures, to exploit the exceptional physical properties of complex oxide materials such as high-temperature superconductors and conducting interfaces between band

  11. Single photon sources in 4H-SiC metal-oxide-semiconductor field-effect transistors

    Science.gov (United States)

    Abe, Y.; Umeda, T.; Okamoto, M.; Kosugi, R.; Harada, S.; Haruyama, M.; Kada, W.; Hanaizumi, O.; Onoda, S.; Ohshima, T.

    2018-01-01

    We present single photon sources (SPSs) embedded in 4H-SiC metal-oxide-semiconductor field-effect transistors (MOSFETs). They are formed in the SiC/SiO2 interface regions of wet-oxidation C-face 4H-SiC MOSFETs and were not found in other C-face and Si-face MOSFETs. Their bright room-temperature photoluminescence (PL) was observed in the range from 550 to 750 nm and revealed variable multi-peak structures as well as variable peak shifts. We characterized a wide variety of their PL spectra as the inevitable variation of local atomic structures at the interface. Their polarization dependence indicates that they are formed at the SiC side of the interface. We also demonstrate that it is possible to switch on/off the SPSs by a bias voltage of the MOSFET.

  12. Evaporation induced wrinkling of graphene oxide at the nanoparticle interface.

    Science.gov (United States)

    Wang, Feng; Liu, Juewen

    2015-01-21

    With the thickness of only a single atomic layer, graphene displays many interesting surface properties. A general observation is that wrinkles are formed on graphene oxide (GO) when it is dried in the presence of adsorbed inorganic nanoparticles. In this case, evaporation induced wrinkling is not an elastic deformation but is permanent. Understanding the nanoscale force of wrinkle formation is important for device fabrication and sensing. Herein, we employ surface functionalized gold nanoparticles (AuNPs) as a model system. All tested AuNPs induced wrinkling, including those capped by DNA, polymers and proteins. The size of AuNPs is less important compared to the properties of solvent. Wrinkle formation is attributed to drying related capillary force acting on the GO surface, and a quantitative equation is derived. After drying, the adsorption affinity between GO and AuNPs is increased due to the increased contact area.

  13. Evaporation induced wrinkling of graphene oxide at the nanoparticle interface

    Science.gov (United States)

    Wang, Feng; Liu, Juewen

    2014-12-01

    With the thickness of only a single atomic layer, graphene displays many interesting surface properties. A general observation is that wrinkles are formed on graphene oxide (GO) when it is dried in the presence of adsorbed inorganic nanoparticles. In this case, evaporation induced wrinkling is not an elastic deformation but is permanent. Understanding the nanoscale force of wrinkle formation is important for device fabrication and sensing. Herein, we employ surface functionalized gold nanoparticles (AuNPs) as a model system. All tested AuNPs induced wrinkling, including those capped by DNA, polymers and proteins. The size of AuNPs is less important compared to the properties of solvent. Wrinkle formation is attributed to drying related capillary force acting on the GO surface, and a quantitative equation is derived. After drying, the adsorption affinity between GO and AuNPs is increased due to the increased contact area.With the thickness of only a single atomic layer, graphene displays many interesting surface properties. A general observation is that wrinkles are formed on graphene oxide (GO) when it is dried in the presence of adsorbed inorganic nanoparticles. In this case, evaporation induced wrinkling is not an elastic deformation but is permanent. Understanding the nanoscale force of wrinkle formation is important for device fabrication and sensing. Herein, we employ surface functionalized gold nanoparticles (AuNPs) as a model system. All tested AuNPs induced wrinkling, including those capped by DNA, polymers and proteins. The size of AuNPs is less important compared to the properties of solvent. Wrinkle formation is attributed to drying related capillary force acting on the GO surface, and a quantitative equation is derived. After drying, the adsorption affinity between GO and AuNPs is increased due to the increased contact area. Electronic supplementary information (ESI) available: Methods. See DOI: 10.1039/c4nr05832a

  14. Impact of wet-oxidized Al2O3/AlGaN interface on AlGaN/GaN 2-DEGs

    Science.gov (United States)

    Meer, Mudassar; Majety, Sridhar; Takhar, Kuldeep; Ganguly, Swaroop; Saha, Dipankar

    2017-04-01

    We investigated the impact of wet-oxidation of AlGaN in an AlGaN/GaN heterostructure by selectively probing the metal/AlGaN interface. The two-dimensional electron gas (2-DEG) characteristics show improved mobility with increasing oxidation time and Al2O3 thickness. The change is attributed to an interplay of the interface trap density (D it) and the oxide thickness. D it is found to reduce progressively for thicker gate oxides as determined by selectively probing the Al2O3/AlGaN interface and employing frequency dependent capacitance and conductance spectroscopy on these devices. The energies of the interface traps are found to be in the range of 0.35-0.45 eV below the conduction band edge. The D it is found to reduce from 2 × 1013 cm-2 eV-1 for 2.3 nm of Al2O3 to 5 × 1012 cm-2 eV-1 for 16 nm of Al2O3. Contrary to the earlier reports of increased 2-DEG electron density, the primary advantage is found to be a reduction in Dit leading to an increased electron mobility from 1730 to 2800 cm2V-1s-1.

  15. Quantum State-Resolved Collision Dynamics of Nitric Oxide at Ionic Liquid and Molten Metal Surfaces

    Science.gov (United States)

    Zutz, Amelia Marie

    Detailed molecular scale interactions at the gas-liquid interface are explored with quantum state-to-state resolved scattering of a jet-cooled beam of NO(2pi1/2; N = 0) from ionic liquid and molten metal surfaces. The scattered distributions are probed via laser-induced fluorescence methods, which yield rotational and spin-orbit state populations that elucidate the dynamics of energy transfer at the gas-liquid interface. These collision dynamics are explored as a function of incident collision energy, surface temperature, scattering angle, and liquid identity, all of which are found to substantially affect the degree of rotational, electronic and vibrational excitation of NO via collisions at the liquid surface. Rotational distributions observed reveal two distinct scattering pathways, (i) molecules that trap, thermalize and eventually desorb from the surface (trapping-desorption, TD), and (ii) those that undergo prompt recoil (impulsive scattering, IS) prior to complete equilibration with the liquid surface. Thermally desorbing NO molecules are found to have rotational temperatures close to, but slightly cooler than the surface temperature, indicative of rotational dependent sticking probabilities on liquid surfaces. Nitric oxide is a radical with multiple low-lying electronic states that serves as an ideal candidate for exploring nonadiabatic state-changing collision dynamics at the gas-liquid interface, which induce significant excitation from ground (2pi1/2) to excited (2pi 3/2) spin-orbit states. Molecular beam scattering of supersonically cooled NO from hot molten metals (Ga and Au, Ts = 300 - 1400 K) is also explored, which provide preliminary evidence for vibrational excitation of NO mediated by thermally populated electron-hole pairs in the hot, conducting liquid metals. The results highlight the presence of electronically nonadiabatic effects and build toward a more complete characterization of energy transfer dynamics at gas-liquid interfaces.

  16. Interface detection in poly-ethylene terephthalate-metal laminates using variable energy positron annihilation

    International Nuclear Information System (INIS)

    Escobar Galindo, R.; Schut, H.; Veen, A. van; Rastogi, R.; Vellinga, W.P.; Meijer, H.E.H.

    2005-01-01

    Thin coatings of poly-ethylene terephthalate (PET) on metal ('laminates') have been studied with a variable energy positron annihilation technique. A correlation between PET crystallinity and the positron annihilation parameter S related to the free volume in the polymer is found. It is shown that buried interfaces in these systems may be detected provided the S parameter of the polymer coating is lower than that of the substrate and higher than that of the surface. Also it is found that large positron diffusion lengths in the substrate favour interface detection. Further, changes in S parameter of PET-metal laminates were measured during uniaxial deformation and shown to be in qualitative accordance with a very simple model description that accounts for changes in free volume in PET during plastic deformation as well as the area fraction of cracks occurring in the PET

  17. Flicker Noise as a Probe of Electronic Interaction at Metal-Single Molecule Interfaces.

    Science.gov (United States)

    Adak, Olgun; Rosenthal, Ethan; Meisner, Jeffery; Andrade, Erick F; Pasupathy, Abhay N; Nuckolls, Colin; Hybertsen, Mark S; Venkataraman, Latha

    2015-06-10

    Charge transport properties of metal-molecule interfaces depend strongly on the character of molecule-electrode interactions. Although through-bond coupled systems have attracted the most attention, through-space coupling is important in molecular systems when, for example, through-bond coupling is suppressed due to quantum interference effects. To date, a probe that clearly distinguishes these two types of coupling has not yet been demonstrated. Here, we investigate the origin of flicker noise in single molecule junctions and demonstrate how the character of the molecule-electrode coupling influences the flicker noise behavior of single molecule junctions. Importantly, we find that flicker noise shows a power law dependence on conductance in all junctions studied with an exponent that can distinguish through-space and through-bond coupling. Our results provide a new and powerful tool for probing and understanding coupling at the metal-molecule interface.

  18. Insertion compounds of transition-metal and uranium oxides

    International Nuclear Information System (INIS)

    Chippindale, A.M.; Dickens, P.G.; Powell, A.V.

    1991-01-01

    Several transition-metal and actinide oxides, in which the metal occurs in a high oxidation state, have open covalent structures and are capable of incorporating alkali and other electropositive metals under mild conditions to form insertion compounds A x MO n . These are solids which have several features in common: Over a range of compositions, A x MO n exists as one or more stable or metastable phases in which the structure of the parent oxide MO n is largely retained and the insertion element A is accommodated interstitially. Insertion is accompanied by a redox process A=A i . + e - M in which M is reduced and the electronic properties of the parent oxide change to those typical of a mixed-valence compound. The insertion process xA + MO n = A x MO n can be reversed, at least to some extent, by chemical or electrochemical reaction, with retention of structure (topotactic reaction). This review concentrates on methods of synthesis, characterisation, crystal structure and thermochemistry of these insertion compounds. It updates and extends previous work. (author)

  19. Chemically synthesized metal-oxide-metal segmented nanowires with high ferroelectric response

    Energy Technology Data Exchange (ETDEWEB)

    Herderick, Edward D; Padture, Nitin P [Department of Materials Science and Engineering, Center for Emergent Materials, Ohio State University, Columbus, OH 43210 (United States); Polomoff, Nicholas A; Huey, Bryan D, E-mail: padture.1@osu.edu [Department of Chemical, Materials, and Biomolecular Engineering, Institute of Materials Science, University of Connecticut, Storrs, CT 06269 (United States)

    2010-08-20

    A chemical synthesis method is presented for the fabrication of high-definition segmented metal-oxide-metal (MOM) nanowires in two different ferroelectric oxide systems: Au-BaTiO{sub 3}-Au and Au-PbTiO{sub 3}-Au. This method entails electrodeposition of segmented nanowires of Au-TiO{sub 2}-Au inside anodic aluminum oxide (AAO) templates, followed by topotactic hydrothermal conversion of the TiO{sub 2} segments into BaTiO{sub 3} or PbTiO{sub 3} segments. Two-terminal devices from individual MOM nanowires are fabricated, and their ferroelectric properties are measured directly, without the aid of scanning probe microscopy (SPM) methods. The MOM nanowire architecture provides high-quality end-on electrical contacts to the oxide segments, and allows direct measurement of properties of nanoscale volume, strain-free oxide segments. Unusually high ferroelectric responses, for chemically synthesized oxides, in these MOM nanowires are reported, and are attributed to the lack of residual strain in the oxides. The ability to measure directly the active properties of nanoscale volume, strain-free oxides afforded by the MOM nanowire architecture has important implications for fundamental studies of not only ferroelectric nanostructures but also nanostructures in the emerging field of multiferroics.

  20. First-Principles Study of Structure Property Relationships of Monolayer (Hydroxy)Oxide-Metal Bifunctional Electrocatalysts

    DEFF Research Database (Denmark)

    Zeng, Zhenhua; Kubal, Joseph; Greeley, Jeffrey Philip

    2015-01-01

    In the present study, on the basis of detailed density functional theory (DFT) calculations, and using Ni hydroxy(oxide) films on Pt(111) and Au(111) electrodes as model systems, we describe a detailed structural and electrocatalytic analysis of hydrogen evolution (HER) at three-phase boundaries...... of information that is inaccessible by purely experimental means, and these structures, in turn, strongly suggest that a bifunctional reaction mechanism for alkaline HER will be operative at the interface between the films, the metal substrates, and the surrounding aqueous medium. This bifunctionality produces...... important changes in the calculated barriers of key elementary reaction steps, including water activation and dissociation, as compared to traditional monofunctional Pt surfaces. The successful identification of the structures of thin metal films and three-phase boundary catalysts is not only an important...

  1. First-Principles Study of Structure Property Relationships of Monolayer (Hydroxy)Oxide-Metal Bifunctional Electrocatalysts

    DEFF Research Database (Denmark)

    Zeng, Zhenhua; Kubal, Joseph; Greeley, Jeffrey Philip

    2015-01-01

    under alkaline electrochemical conditions. We demonstrate that the structure and oxidation state of the films can be systematically tuned by changing the applied electrode potential and/or the nature of substrates. Structural features determined from the theoretical calculations provide a wealth...... of information that is inaccessible by purely experimental means, and these structures, in turn, strongly suggest that a bifunctional reaction mechanism for alkaline HER will be operative at the interface between the films, the metal substrates, and the surrounding aqueous medium. This bifunctionality produces...... important changes in the calculated barriers of key elementary reaction steps, including water activation and dissociation, as compared to traditional monofunctional Pt surfaces. The successful identification of the structures of thin metal films and three-phase boundary catalysts is not only an important...

  2. Anomalous positive flatband voltage shifts in metal gate stacks containing rare-earth oxide capping layers

    KAUST Repository

    Caraveo-Frescas, J. A.

    2012-03-09

    It is shown that the well-known negative flatband voltage (VFB) shift, induced by rare-earth oxide capping in metal gate stacks, can be completely reversed in the absence of the silicon overlayer. Using TaN metal gates and Gd2O3-doped dielectric, we measure a ∼350 mV negative shift with the Si overlayer present and a ∼110 mV positive shift with the Si overlayer removed. This effect is correlated to a positive change in the average electrostatic potential at the TaN/dielectric interface which originates from an interfacial dipole. The dipole is created by the replacement of interfacial oxygen atoms in the HfO2 lattice with nitrogen atoms from TaN.

  3. Band structure engineering and vacancy induced metallicity at the GaAs-AlAs interface

    KAUST Repository

    Upadhyay Kahaly, M.

    2011-09-20

    We study the epitaxial GaAs-AlAs interface of wide gap materials by full-potential density functional theory. AlAsthin films on a GaAs substrate and GaAsthin films on an AlAs substrate show different trends for the electronic band gap with increasing film thickness. In both cases, we find an insulating state at the interface and a negligible charge transfer even after relaxation. Differences in the valence and conduction band edges suggest that the energy band discontinuities depend on the growth sequence. Introduction of As vacancies near the interface induces metallicity, which opens great potential for GaAs-AlAs heterostructures in modern electronics.

  4. 40 CFR 721.5315 - Nickel, cobalt mixed metal oxide (generic).

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Nickel, cobalt mixed metal oxide... Specific Chemical Substances § 721.5315 Nickel, cobalt mixed metal oxide (generic). (a) Chemical substance... nickel, cobalt mixed metal oxide. (PMN P-02-90) is subject to reporting under this section for the...

  5. Conductive transition metal oxide nanostructured electrochromic material and optical switching devices constructed thereof

    Energy Technology Data Exchange (ETDEWEB)

    Mattox, Tracy M.; Koo, Bonil; Garcia, Guillermo; Milliron, Delia J.; Trizio, Luca De; Dahlman, Clayton

    2017-10-10

    An electrochromic device includes a nanostructured transition metal oxide bronze layer that includes one or more transition metal oxide and one or more dopant, a solid state electrolyte, and a counter electrode. The nanostructured transition metal oxide bronze selectively modulates transmittance of near-infrared (NIR) spectrum and visible spectrum radiation as a function of an applied voltage to the device.

  6. The nature of transition-metal-oxide surfaces

    Science.gov (United States)

    Henrich, V. E.

    The surfaces of the 3d-transition-metal oxides form a rich and important system in which to study the effects of atomic geometry, ligand coordination and d-orbital population on surface electronic structure and chemisorption. This article considers the properties of those surfaces in terms of the types of surface structures that can exist, including steps and point defects, and their relation to the experimental data that is available for well characterized, single-crystal surfaces. The electronic structure of nearly perfect surfaces is very similar to that of the bulk for many of the oxides that have been studied; atoms at step sites also appear to have properties similar to those of atoms on terraces. Point defects are often associated with surfaces 0 vacancies and attendant transfer of electrons to adjacent metal cations. Those cations are poorly screened from each other, and the excess charge is presumably shared between two or more cations having reduced ligand coordination. Point defects are generally more active for chemisorption than are perfect surfaces, however for Ti 2O 3 and V 2O 3, whose cations have 3d 1 and 3d 2 electronic configurations respectively, the cleaved (047) surface is more active than are surfaces having a high density of defects. The chemisorption behavior of both nearly perfect and defect surfaces of 3d-transition-metal oxides varies widely from one material to another, and it is suggestive to correlate this with cation d-orbital population. However, too few oxides have yet been studied to draw any firm conclusions. Additional theoretical work on perfect surfaces, defects and chemisorption is also necessary in order to gain a more complete understanding of transition-metal-oxide surfaces.

  7. Dependence of capacitance of metal-molten salt interface on local density profiles near electrode

    International Nuclear Information System (INIS)

    Ballone, P.; Pastore, G.; Tosi, M.P.; Painter, K.R.; Grout, P.J.; March, N.H.

    1983-09-01

    The mean spherical approximation applied to a metal-molten salt interface is generalized to take further account of the local density profiles near the electrode. The temperature dependence of the differential capacitance is shown to arise, in large measure from such local structure. However, the hard wall assumption for the electrode is retained and this must be kept in mind in comparing our model results with experiment. (author)

  8. Interface properties of SiO2/n-GaN metal-insulator-semiconductor structures

    OpenAIRE

    Yoshitaka, Nakano; Takashi, Jimbo

    2002-01-01

    Electrical characterization of SiO2/n-GaN metal-insulator-semiconductor structures fabricated on sapphire substrates was performed by using high-frequency pulsed capacitance-voltage and capacitance-transient techniques. Fast and slow capacitance transients are clearly seen after applying reverse voltages, reflecting thermal emissions of carriers from the SiO2/GaN interface. The temperature dependence of the capacitance-voltage characteristics shows capacitance saturation in deep depletion (>1...

  9. The effects of soluble salts at the metal/paint interface: advances in knowledge

    OpenAIRE

    Fuente, Daniel de la; Chico, Belén; Morcillo, Manuel

    2006-01-01

    The presence of soluble salts (particularly sulphates and chlorides) at the metal/paint interface is known to have a detrimental effect on the integrity of most paint systems. Though this is a long-standing problem, it has recently come to receive greater attention from the protective coatings industry. International Standards Organization (ISO) has for some time been trying to develop a standard about guidance levels for water-soluble salt contamination before the application of paints and r...

  10. Electromigration Related Effects At Metal-Metal Interfaces: Application To Railguns

    National Research Council Canada - National Science Library

    Cleveland, Jr, William B

    2007-01-01

    This thesis had 2 objectives. The first purpose of this thesis was to develop an experimental procedure to study electric current induced flow of liquid metal, similar to that found at the armature-rail contact due to local...

  11. Interface Characterization of Metals and Metal-nitrides to Phase Change Materials

    NARCIS (Netherlands)

    Roy, Deepu; Gravesteijn, Dirk J; Wolters, Robertus A.M.

    2011-01-01

    We have investigated the interfacial contact properties of the CMOS compatible electrode materials W, TiW, Ta, TaN and TiN to doped-Sb2Te phase change material (PCM). This interface is characterized both in the amorphous and in the crystalline state of the doped-Sb2Te. The electrical nature of the

  12. Charge separation technique for metal-oxide-silicon capacitors in the presence of hydrogen deactivated dopants

    International Nuclear Information System (INIS)

    Witczak, Steven C.; Winokur, Peter S.; Lacoe, Ronald C.; Mayer, Donald C.

    2000-01-01

    An improved charge separation technique for metal-oxide-silicon (MOS) capacitors is presented which accounts for the deactivation of substrate dopants by hydrogen at elevated irradiation temperatures or small irradiation biases. Using high-frequency capacitance-voltage measurements, radiation-induced inversion voltage shifts are separated into components due to oxide trapped charge, interface traps, and deactivated dopants, where the latter is computed from a reduction in Si capacitance. In the limit of no radiation-induced dopant deactivation, this approach reduces to the standard midgap charge separation technique used widely for the analysis of room-temperature irradiations. The technique is demonstrated on a p-type MOS capacitor irradiated with 60 Co γ rays at 100 degree sign C and zero bias, where the dopant deactivation is significant.(c) 2000 American Institute of Physics

  13. Influence of uranium hydride oxidation on uranium metal behaviour

    International Nuclear Information System (INIS)

    Patel, N.; Hambley, D.; Clarke, S.A.; Simpson, K.

    2013-01-01

    This work addresses concerns that the rapid, exothermic oxidation of active uranium hydride in air could stimulate an exothermic reaction (burning) involving any adjacent uranium metal, so as to increase the potential hazard arising from a hydride reaction. The effect of the thermal reaction of active uranium hydride, especially in contact with uranium metal, does not increase in proportion with hydride mass, particularly when considering large quantities of hydride. Whether uranium metal continues to burn in the long term is a function of the uranium metal and its surroundings. The source of the initial heat input to the uranium, if sufficient to cause ignition, is not important. Sustained burning of uranium requires the rate of heat generation to be sufficient to offset the total rate of heat loss so as to maintain an elevated temperature. For dense uranium, this is very difficult to achieve in naturally occurring circumstances. Areas of the uranium surface can lose heat but not generate heat. Heat can be lost by conduction, through contact with other materials, and by convection and radiation, e.g. from areas where the uranium surface is covered with a layer of oxidised material, such as burned-out hydride or from fuel cladding. These rates of heat loss are highly significant in relation to the rate of heat generation by sustained oxidation of uranium in air. Finite volume modelling has been used to examine the behaviour of a magnesium-clad uranium metal fuel element within a bottle surrounded by other un-bottled fuel elements. In the event that the bottle is breached, suddenly, in air, it can be concluded that the bulk uranium metal oxidation reaction will not reach a self-sustaining level and the mass of uranium oxidised will likely to be small in relation to mass of uranium hydride oxidised. (authors)

  14. Energy level alignment and electron transport through metal/organic contacts. From interfaces to molecular electronics

    Energy Technology Data Exchange (ETDEWEB)

    Abad, Enrique

    2013-07-01

    A new calculational approach to describing metal/organic interfaces. A valuable step towards a better understanding of molecular electronics. Nominated as an outstanding contribution by the Autonomous University of Madrid. In recent years, ever more electronic devices have started to exploit the advantages of organic semiconductors. The work reported in this thesis focuses on analyzing theoretically the energy level alignment of different metal/organic interfaces, necessary to tailor devices with good performance. Traditional methods based on density functional theory (DFT), are not appropriate for analyzing them because they underestimate the organic energy gap and fail to correctly describe the van der Waals forces. Since the size of these systems prohibits the use of more accurate methods, corrections to those DFT drawbacks are desirable. In this work a combination of a standard DFT calculation with the inclusion of the charging energy (U) of the molecule, calculated from first principles, is presented. Regarding the dispersion forces, incorrect long range interaction is substituted by a van der Waals potential. With these corrections, the C60, benzene, pentacene, TTF and TCNQ/Au(111) interfaces are analyzed, both for single molecules and for a monolayer. The results validate the induced density of interface states model.

  15. Water absorption in thermally grown oxides on SiC and Si: Bulk oxide and interface properties

    Science.gov (United States)

    Liu, Gang; Xu, Can; Yakshinskiy, Boris; Wielunski, Leszek; Gustafsson, Torgny; Bloch, Joseph; Dhar, Sarit; Feldman, Leonard C.

    2014-11-01

    We combine nuclear reaction analysis and electrical measurements to study the effect of water exposure (D2O) on the n-type 4H-SiC carbon face (000 1 ¯ ) MOS system and to compare to standard silicon based structures. We find that: (1) The bulk of the oxides on Si and SiC behave essentially the same with respect to deuterium accumulation; (2) there is a significant difference in accumulation of deuterium at the semiconductor/dielectric interface, the SiC C-face structure absorbs an order of magnitude more D than pure Si; (3) standard interface passivation schemes such as NO annealing greatly reduce the interfacial D accumulation; and (4) the effective interfacial charge after D2O exposure is proportional to the total D amount at the interface.

  16. Separation of effects of oxide-trapped charge and interface-trapped charge on mobility in irradiated power MOSFETs

    International Nuclear Information System (INIS)

    Zupac, D.; Galloway, K.F.; Khosropour, P.; Anderson, S.R.; Schrimpf, R.D.

    1993-01-01

    An effective approach to separating the effects of oxide-trapped charge and interface-trapped charge on mobility degradation in irradiated MOSFETs is demonstrated. It is based on analyzing mobility data sets which have different functional relationships between the radiation-induced-oxide-trapped charge and interface-trapped charge. Separation of effects of oxide-trapped charge and interface-trapped charge is possible only if these two trapped charge components are not linearly dependent. A significant contribution of oxide-trapped charge to mobility degradation is demonstrated and quantified

  17. PHENOL OXIDATION USING NATURAL ZEOLITE SUPPORTED METAL ION CATALYST

    Directory of Open Access Journals (Sweden)

    Sri Wardhani

    2010-06-01

    Full Text Available Phenol which contained in waste water has to be reduced and it could be done by oxygen oxidation.  In order to increase the rate of reaction it was needed a catalyst. In this research the capability of various catalysts, namely zeolite-Zn(II, zeolite-Cu(II and zeolite-Co(IIin oxidation of phenol has been investigated. The aim of this research was to study the type of metal ion catalyst towards the percentage of oxidated phenol. The oxidation process were carried out in an aqueous phenol of 100 ppm with oxygen flow rate of 200 mL/min. in the presence of catalysts with 0.2M of initial impregnation concentration. The capabilities of catalysts were performed by calculating the activation energy and it was done at two different temperatures, i.e. 70 and 90 oC. The percentage of oxidated phenol was determinated by measuring its concentration using UV-VIS spectrophotometer. In addition, the impregnated metal was calculated by measuring the ion concentration remains in the filtrate solution and it was determined using Atomic Absorption Spectrophotometer. The results showed that metal ion types affected the catalytic activity. The order of phenol oxidationactivity decreased as Co(II > Cu(II > Zn(II. The surface characteristics of catalysts were supported by pore volume and pore diameter i.e 0.009 cm3/g and 16.59 Å for Zn(II whereas specific surface area was 10.32 m2/g for Zn(II, 0.004 cm3/g and 24.37 Å for Cu(II whereas specific surface area was 3.57 m2/g for Cu(II, 0.001 cm3/g and 19.63 Å for Co(II whereas specific surface area was 10.26m2/g for Co(II.   Keywords: phenol,natural zeolite, catalyst, oxidation

  18. Surface stress and large-scale self-organization at organic-metal interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Pollinger, Florian

    2009-01-22

    The role of elastic interactions, particularly for the self-organized formation of periodically faceted interfaces, was investigated in this thesis for archetype organic-metal interfaces. The cantilever bending technique was applied to study the change of surface stress upon formation of the interface between 3,4,9,10-perylene-tetracarboxylic-dianhydride (PTCDA) and Ag(111). The main focus of this work was on the investigation of the formation of the long-range ordered, self-organized faceted PTCDA/Ag(10 8 7) interface. Reciprocal space maps of this interface were recorded both by spot profile analysis low energy electron diffraction (SPA-LEED) and low energy electron microscopy (LEEM) in selected area LEED mode. Complementary to the reciprocal data, also microscopic real-space LEEM data were used to characterize the morphology of this interface. Six different facet faces ((111), (532), (743), (954), (13 9 5), and (542)) were observed for the preparation path of molecular adsorption on the substrate kept at 550 K. Facet-sensitive dark-field LEEM localized these facets to grow in homogeneous areas of microscopic extensions. The temperature-dependence of the interface formation was studied in a range between 418 K and 612 K in order to learn more about the kinetics of the process. Additional steeper facets of 27 inclination with respect to the (111) surface were observed in the low temperature regime. Furthermore, using facet-sensitive dark-field LEEM, spatial and size distributions of specific facets were studied for the different temperatures. Moreover, the facet dimensions were statistically analyzed. The total island size of the facets follows an exponential distribution, indicating a random growth mode in absence of any mutual facet interactions. While the length distribution of the facets also follows an exponential distribution, the width distribution is peaked, reflecting the high degree of lateral order. This anisotropy is temperature-dependent and occurs

  19. Ceria doped mixed metal oxide nanoparticles as oxidation catalysts: Synthesis and their characterization

    OpenAIRE

    Sultana, S.S.P.; Kishore, D.H.V.; Kuniyil, Mufsir; Khan, Mujeeb; Alwarthan, Abdulrahman; Prasad, K.R.S.; Labis, Joselito P.; Adil, S.F.

    2015-01-01

    Mixed metal nanoparticles (NPs) have attracted significant attention as catalysts for various organic transformations. In this study, we have demonstrated the preparation of nickel–manganese mixed metal oxide NPs doped with X% nano cerium oxide (X = 1, 3, 5 mol%) by a facile co-precipitation technique using surfactant and surfactant free methodologies. The as-synthesized materials were calcined at different temperatures (300 °C, 400 °C, and 500 °C), and were characterized using various spectr...

  20. Initial Processes of Atomic Layer Deposition of Al2O3 on InGaAs: Interface Formation Mechanisms and Impact on Metal-Insulator-Semiconductor Device Performance

    Directory of Open Access Journals (Sweden)

    Shinichi Takagi

    2012-03-01

    Full Text Available Interface-formation processes in atomic layer deposition (ALD of Al2O3 on InGaAs surfaces were investigated using on-line Auger electron spectroscopy. Al2O3 ALD was carried out by repeating a cycle of Al(CH33 (trimethylaluminum, TMA adsorption and oxidation by H2O. The first two ALD cycles increased the Al KLL signal, whereas they did not increase the O KLL signal. Al2O3 bulk-film growth started from the third cycle. These observations indicated that the Al2O3/InGaAs interface was formed by reduction of the surface oxides with TMA. In order to investigate the effect of surface-oxide reduction on metal-insulator-semiconductor (MIS properties, capacitors and field-effect transistors (FETs were fabricated by changing the TMA dosage during the interface formation stage. The frequency dispersion of the capacitance-voltage characteristics was reduced by employing a high TMA dosage. The high TMA dosage, however, induced fixed negative charges at the MIS interface and degraded channel mobility.

  1. Reliable energy level alignment at physisorbed molecule-metal interfaces from density functional theory.

    Science.gov (United States)

    Egger, David A; Liu, Zhen-Fei; Neaton, Jeffrey B; Kronik, Leeor

    2015-04-08

    A key quantity for molecule-metal interfaces is the energy level alignment of molecular electronic states with the metallic Fermi level. We develop and apply an efficient theoretical method, based on density functional theory (DFT) that can yield quantitatively accurate energy level alignment information for physisorbed metal-molecule interfaces. The method builds on the "DFT+Σ" approach, grounded in many-body perturbation theory, which introduces an approximate electron self-energy that corrects the level alignment obtained from conventional DFT for missing exchange and correlation effects associated with the gas-phase molecule and substrate polarization. Here, we extend the DFT+Σ approach in two important ways: first, we employ optimally tuned range-separated hybrid functionals to compute the gas-phase term, rather than rely on GW or total energy differences as in prior work; second, we use a nonclassical DFT-determined image-charge plane of the metallic surface to compute the substrate polarization term, rather than the classical DFT-derived image plane used previously. We validate this new approach by a detailed comparison with experimental and theoretical reference data for several prototypical molecule-metal interfaces, where excellent agreement with experiment is achieved: benzene on graphite (0001), and 1,4-benzenediamine, Cu-phthalocyanine, and 3,4,9,10-perylene-tetracarboxylic-dianhydride on Au(111). In particular, we show that the method correctly captures level alignment trends across chemical systems and that it retains its accuracy even for molecules for which conventional DFT suffers from severe self-interaction errors.

  2. Ball lightning from atmospheric discharges via metal nanosphere oxidation: from soils, wood or metals.

    Science.gov (United States)

    Abrahamson, John

    2002-01-15

    The slow (diffusion-limited) oxidation of metal nanoparticles has previously been proposed as the mechanism for ball lightning energy release, and argued to be the result of a normal lightning strike on soil. Here this basic model of networked nanoparticles is detailed further, and extended to lightning strikes on metal structures, and also to the action of other storm-related discharges or man-made discharges. The basic model predicted the important properties of "average" observed ball lightning, and the extension in this paper also covers high-energy examples of ball lightning. Laboratory checks of the theory are described, and predictions given of what conditions are necessary for observing ball lightning in the laboratory. Key requirements of the model are a sheltered region near the strike foot and starting materials which can generate a metal vapour under intensive heating, including soil, wood or a metal structure. The evolution of hydrocarbons (often plastics) along with metal vapour can ensure the local survival of the metal vapour even in an oxidizing atmosphere. Subsequent condensation of this vapour to metallic nanoparticles in networks provides the coherence of a ball structure, which also releases light over an extended time. Also discussed is the passage of ball lightning through a sheet of building material, including glass, and its occasional charring of flesh on close contact.

  3. Magnetic preferential orientation of metal oxide superconducting materials

    Science.gov (United States)

    Capone, Donald W.; Dunlap, Bobby D.; Veal, Boyd W.

    1990-01-01

    A superconductor comprised of a polycrystalline metal oxide such as YBa.sub.2 Cu.sub.3 O.sub.7-X (where 0material permits the use of an applied magnetic field to orient the individual crystals when in the superconducting state to substantially increase current transport between adjacent grains. In another embodiment, the anisotropic paramagnetic susceptibility of rare-earth ions substituted into the oxide material is made use of as an applied magnetic field orients the particles in a preferential direction. This latter operation can be performed with the material in the normal (non-superconducting) state.

  4. Transport phenomena of aluminium oxide in metal halide lamps

    Energy Technology Data Exchange (ETDEWEB)

    Fischer, S; Markus, T [Institute for Energy Research, Forschungszentrum Juelich GmbH, D-52425 Juelich (Germany); Niemann, U [Philips GmbH, Research Laboratories, PO Box 500145, Aachen, D-52085 (Germany)], E-mail: s.fischer@fz-juelich.de

    2008-07-21

    A better understanding of the transport phenomena observed in metal halide lamps can be achieved using computer-based model calculations. The chemical transport of aluminium oxide in advanced high-pressure discharge vessels was calculated as a function of temperature and composition of the salt mixture relevant to the lamp. Below 1773 K chemical transport is the prevailing process; above this temperature the vaporization and condensation of the envelope material-aluminium oxide-become more important. The results of the calculations show that the amount of transported alumina increases linearly with the number of iteration cycles and exponentially with the temperature gradient.

  5. Promotion of water-mediated carbon removal by nanostructured barium oxide/nickel interfaces in solid oxide fuel cells

    Science.gov (United States)

    Yang, Lei; Choi, YongMan; Qin, Wentao; Chen, Haiyan; Blinn, Kevin; Liu, Mingfei; Liu, Ping; Bai, Jianming; Tyson, Trevor A.; Liu, Meilin

    2011-01-01

    The existing Ni-yttria-stabilized zirconia anodes in solid oxide fuel cells (SOFCs) perform poorly in carbon-containing fuels because of coking and deactivation at desired operating temperatures. Here we report a new anode with nanostructured barium oxide/nickel (BaO/Ni) interfaces for low-cost SOFCs, demonstrating high power density and stability in C3H8, CO and gasified carbon fuels at 750°C. Synchrotron-based X-ray analyses and microscopy reveal that nanosized BaO islands grow on the Ni surface, creating numerous nanostructured BaO/Ni interfaces that readily adsorb water and facilitate water-mediated carbon removal reactions. Density functional theory calculations predict that the dissociated OH from H2O on BaO reacts with C on Ni near the BaO/Ni interface to produce CO and H species, which are then electrochemically oxidized at the triple-phase boundaries of the anode. This anode offers potential for ushering in a new generation of SOFCs for efficient, low-emission conversion of readily available fuels to electricity. PMID:21694705

  6. Characterization of electrode-electrolyte interface in solid oxide fuel cell

    International Nuclear Information System (INIS)

    Lenka, R.K.; Mahata, T.; Sinha, P.K.; Tyagi, A.K.

    2010-01-01

    Full text: Solid oxide fuel cell (SOFC) is an electrochemical device in which chemical energy of fuel, such as, hydrogen, is directly converted to electrical energy in an efficient and environment-friendly manner.The SOFC is primarily a multi-layer structure in which impervious solid oxide electrolyte is sandwiched between porous electrodes. For good performance the cell resistance should be reasonably low. The internal resistance of a working cell is primarily determined by the resistance of the electrolyte layer and the resistances at the electrode - electrolyte interfaces. The later is dependent on the catalytic activity of the electrode material for the corresponding electrode reaction and the interface microstructure in terms of length of the triple phase boundary (TBP). The ceramic fabrication technique plays an important role in determining the interfacial microstructure and hence, the overall performance of a cell. In the present study, gadolinium cobaltate based cathode material and nickel-gadolinia doped ceria (Ni-GDC) composite anode material have been synthesized and integrated with GDC electrolyte. The interfacial microstructures have been studied by scanning electron microscopy (SEM). The area specific resistance (ASR) at the electrode-electrolyte interfaces have been evaluated by electrochemical impedance spectroscopy (EIS) using symmetrical cell. Using our optimum processing technique ASR values of 0.41 U.cm 2 and 0.03 U.cm 2 have been obtained at Ba-doped GdCoO 3 /GDC interface and Ni-GDC/GDC interface respectively at 900 deg C

  7. X-ray photoelectron spectroscopy study of the initial oxidation of uranium metal in oxygen+water-vapour mixtures

    International Nuclear Information System (INIS)

    Allen, G.C.; Tucker, P.M.; Lewis, R.A.

    1984-01-01

    X-ray photoelectron spectroscopy (X.p.s.) has been used to study the chemical nature of the oxide film initially produced on clean uranium metal in oxygen + water-vapour atmospheres. The rate of reaction has been monitored and the nature of the surface film determined. From a consideration of the O 1s and U 4f X.p. spectra it has been possible to advance a mechanism which explains the complex nature of the surface oxide and the lack of satellite structure in the spectra. This is postulated to be a consequence of the way in which OH - is involved in the growth of the oxide and the presence of hydrogen in the surface film. The presence of oxygen retards the water oxidation reaction by inhibiting the decomposition of water vapour at the gas/oxide interface. (author)

  8. Cell adhesion and proliferation on poly(tetrafluoroethylene) with plasma-metal and plasma-metal-carbon interfaces

    Science.gov (United States)

    Reznickova, Alena; Kvitek, Ondrej; Kolarova, Katerina; Smejkalova, Zuzana; Svorcik, Vaclav

    2017-06-01

    The aim of this article is to investigate the effect of the interface between plasma activated, gold and carbon coated poly(tetrafluoroethylene) (PTFE) on in vitro adhesion and spreading of mouse fibroblasts (L929). Surface properties of pristine and modified PTFE were studied by several experimental techniques. The thickness of a deposited gold film is an increasing function of the sputtering time, conversely thickness of carbon layer decreases with increasing distance between carbon source and the substrate. Because all the used surface modification techniques take place in inert Ar plasma, oxidized degradation products are formed on the PTFE surface, which affects wettability of the polymer surface. Cytocompatibility tests indicate that on samples with Au/C interface, the cells accumulate on the part of sample with evaporated carbon. Number of L929 cells proliferated on the studied samples is comparable to tissue culture polystyrene standard.

  9. Antimicrobial Activity of Nitric Oxide-Releasing Ti-6Al-4V Metal Oxide

    Science.gov (United States)

    Reger, Nina A.; Meng, Wilson S.; Gawalt, Ellen S.

    2017-01-01

    Titanium and titanium alloy materials are commonly used in joint replacements, due to the high strength of the materials. Pathogenic microorganisms can easily adhere to the surface of the metal implant, leading to an increased potential for implant failure. The surface of a titanium-aluminum-vanadium (Ti-6Al-4V) metal oxide implant material was functionalized to deliver an small antibacterial molecule, nitric oxide. S-nitroso-penicillamine, a S-nitrosothiol nitric oxide donor, was covalently immobilized on the metal oxide surface using self-assembled monolayers. Infrared spectroscopy was used to confirm the attachment of the S-nitrosothiol donor to the Ti-Al-4V surface. Attachment of S-nitroso-penicillamine resulted in a nitric oxide (NO) release of 89.6 ± 4.8 nmol/cm2 under physiological conditions. This low concentration of nitric oxide reduced Escherichia coli and Staphylococcus epidermidis growth by 41.5 ± 1.2% and 25.3 ± 0.6%, respectively. Combining the S-nitrosothiol releasing Ti-6Al-4V with tetracycline, a commonly-prescribed antibiotic, increased the effectiveness of the antibiotic by 35.4 ± 1.3%, which allows for lower doses of antibiotics to be used. A synergistic effect of ampicillin with S-nitroso-penicillamine-modified Ti-6Al-4V against S. epidermidis was not observed. The functionalized Ti-6Al-4V surface was not cytotoxic to mouse fibroblasts. PMID:28635681

  10. Understanding of catalysis on early transition metal oxide-based catalysts through exploration of surface structure and chemistry during catalysis using in-situ approaches

    Energy Technology Data Exchange (ETDEWEB)

    Tao, Franklin [Univ. of Kansas, Lawrence, KS (United States). Dept. of Chemical and Petroleum Engineering. Dept. of Chemistry

    2015-09-14

    Two main categories of heterogeneous catalysts are metal and metal oxide which catalyze 80% chemical reactions at solid-gas and solid-liquid interfaces. Metal oxide catalysts are much more complicated than metal catalysts. The reason is that the cations of the metal atoms could exhibit a few different oxidation states on surface of the same catalyst particle such as Co3O4 or change of their oxidation states under different reactive environments. For a metal catalyst, there is only one oxidation state typically. In addition, surface of a metal oxide can be terminated with multiple surface functionalities including O atoms with different binding configurations and OH group. For metal, only metal atoms are exposed typically. Obviously, the complication of surface chemistry and structure of a metal oxide makes studies of surface of an oxide catalyst very challenging. Due to the complication of surface of a meal oxide, the electronic and geometric structures of surface of a metal oxide and the exposed species have received enormous attention since oxide catalysts catalyze at least 1/3 chemical reactions in chemical and energy industries. Understanding of catalytic reactions on early transition metal oxide-based catalysts is fundamentally intriguing and of great practical interest in energy- and environment-related catalysis. Exploration of surface chemistry of oxide-based catalysts at molecular level during catalysis has remained challenging though it is critical in deeply understanding catalysis on oxide-based catalysts and developing oxide-based catalysts with high activity and selectivity. Thus, the overall objective of this project is to explore surface chemistry and structure of early transition metal oxide-based catalysts through in-situ characterization of surface of catalysts, measurements of catalytic performances, and then build an intrinsic correlation of surface chemistry and structure with their catalytic performances in a few

  11. Efficient photocarrier injection in a transition metal oxide heterostructure

    CERN Document Server

    Muraoka, Y; Ueda, Y; Hiroi, Z

    2002-01-01

    An efficient method for doping a transition metal oxide (TMO) with hole carriers is presented: photocarrier injection (PCI) in an oxide heterostructure. It is shown that an insulating vanadium dioxide (VO sub 2) film is rendered metallic under light irradiation by PCI from an n-type titanium dioxide (TiO sub 2) substrate doped with Nb. Consequently, a large photoconductivity, which is exceptional for TMOs, is found in the VO sub 2 /TiO sub 2 :Nb heterostructure. We propose an electronic band structure where photoinduced holes created in TiO sub 2 :Nb can be transferred into the filled V 3d band via the low-lying O 2p band of VO sub 2. (letter to the editor)

  12. Synthesis of metal-metal oxide catalysts and electrocatalysts using a metal cation adsorption/reduction and adatom replacement by more noble ones

    Science.gov (United States)

    Adzic, Radoslav; Vukmirovic, Miomir; Sasaki, Kotaro

    2010-04-27

    The invention relates to platinum-metal oxide composite particles and their use as electrocatalysts in oxygen-reducing cathodes and fuel cells. The invention particularly relates to methods for preventing the oxidation of the platinum electrocatalyst in the cathodes of fuel cells by use of these platinum-metal oxide composite particles. The invention additionally relates to methods for producing electrical energy by supplying such a fuel cell with an oxidant, such as oxygen, and a fuel source, such as hydrogen. The invention also relates to methods of making the metal-metal oxide composites.

  13. A metallization and bonding approach for high performance carbon nanotube thermal interface materials

    International Nuclear Information System (INIS)

    Cross, Robert; Graham, Samuel; Cola, Baratunde A; Fisher, Timothy; Xu Xianfan; Gall, Ken

    2010-01-01

    A method has been developed to create vertically aligned carbon nanotube (VACNT) thermal interface materials that can be attached to a variety of metallized surfaces. VACNT films were grown on Si substrates using standard CVD processing followed by metallization using Ti/Au. The coated CNTs were then bonded to metallized substrates at 220 deg. C. By reducing the adhesion of the VACNTs to the growth substrate during synthesis, the CNTs can be completely transferred from the Si growth substrate and used as a die attachment material for electronic components. Thermal resistance measurements using a photoacoustic technique showed thermal resistances as low as 1.7 mm 2 K W -1 for bonded VACNT films 25-30 μm in length and 10 mm 2 K W -1 for CNTs up to 130 μm in length. Tensile testing demonstrated a die attachment strength of 40 N cm -2 at room temperature. Overall, these metallized and bonded VACNT films demonstrate properties which are promising for next-generation thermal interface material applications.

  14. Hydrogen sensors using nitride-based semiconductor diodes: the role of metal/semiconductor interfaces.

    Science.gov (United States)

    Irokawa, Yoshihiro

    2011-01-01

    In this paper, I review my recent results in investigating hydrogen sensors using nitride-based semiconductor diodes, focusing on the interaction mechanism of hydrogen with the devices. Firstly, effects of interfacial modification in the devices on hydrogen detection sensitivity are discussed. Surface defects of GaN under Schottky electrodes do not play a critical role in hydrogen sensing characteristics. However, dielectric layers inserted in metal/semiconductor interfaces are found to cause dramatic changes in hydrogen sensing performance, implying that chemical selectivity to hydrogen could be realized. The capacitance-voltage (C-V) characteristics reveal that the work function change in the Schottky metal is not responsible mechanism for hydrogen sensitivity. The interface between the metal and the semiconductor plays a critical role in the interaction of hydrogen with semiconductor devises. Secondly, low-frequency C-V characterization is employed to investigate the interaction mechanism of hydrogen with diodes. As a result, it is suggested that the formation of a metal/semiconductor interfacial polarization could be attributed to hydrogen-related dipoles. In addition, using low-frequency C-V characterization leads to clear detection of 100 ppm hydrogen even at room temperature where it is hard to detect hydrogen by using conventional current-voltage (I-V) characterization, suggesting that low-frequency C-V method would be effective in detecting very low hydrogen concentrations.

  15. Hydrogen Sensors Using Nitride-Based Semiconductor Diodes: The Role of Metal/Semiconductor Interfaces

    Directory of Open Access Journals (Sweden)

    Yoshihiro Irokawa

    2011-01-01

    Full Text Available In this paper, I review my recent results in investigating hydrogen sensors using nitride-based semiconductor diodes, focusing on the interaction mechanism of hydrogen with the devices. Firstly, effects of interfacial modification in the devices on hydrogen detection sensitivity are discussed. Surface defects of GaN under Schottky electrodes do not play a critical role in hydrogen sensing characteristics. However, dielectric layers inserted in metal/semiconductor interfaces are found to cause dramatic changes in hydrogen sensing performance, implying that chemical selectivity to hydrogen could be realized. The capacitance-voltage (C-V characteristics reveal that the work function change in the Schottky metal is not responsible mechanism for hydrogen sensitivity. The interface between the metal and the semiconductor plays a critical role in the interaction of hydrogen with semiconductor devises. Secondly, low-frequency C-V characterization is employed to investigate the interaction mechanism of hydrogen with diodes. As a result, it is suggested that the formation of a metal/semiconductor interfacial polarization could be attributed to hydrogen-related dipoles. In addition, using low-frequency C-V characterization leads to clear detection of 100 ppm hydrogen even at room temperature where it is hard to detect hydrogen by using conventional current-voltage (I-V characterization, suggesting that low-frequency C-V method would be effective in detecting very low hydrogen concentrations.

  16. Fermi level dependent native defect formation: Consequences for metal-semiconductor and semiconductor-semiconductor interfaces

    International Nuclear Information System (INIS)

    Walukiewicz, W.

    1988-02-01

    The amphoteric native defect model of the Schottky barrier formation is used to analyze the Fermi level pinning at metal/semiconductor interfaces for submonolayer metal coverages. It is assumed that the energy required for defect generation is released in the process of surface back-relaxation. Model calculations for metal/GaAs interfaces show a weak dependence of the Fermi level pinning on the thickness of metal deposited at room temperature. This weak dependence indicates a strong dependence of the defect formation energy on the Fermi level, a unique feature of amphoteric native defects. This result is in very good agreement with experimental data. It is shown that a very distinct asymmetry in the Fermi level pinning on p- and n-type GaAs observed at liquid nitrogen temperatures can be understood in terms of much different recombination rates for amphoteric native defects in those two types of materials. Also, it is demonstrated that the Fermi level stabilization energy, a central concept of the amphoteric defect system, plays a fundamental role in other phenomena in semiconductors such as semiconductor/semiconductor heterointerface intermixing and saturation of free carrier concentration. 33 refs., 6 figs

  17. High voltage measurements on metal-oxide surge arresters

    Energy Technology Data Exchange (ETDEWEB)

    Yli-Aeyhoe, S. [Tampere University of Technology (Finland). High Voltage Laboratory

    2000-07-01

    Metal-oxide surge arresters (MOA) are used to prevent damages caused by overvoltages and currents. Because of the function of MOAs they have to be tested with high voltage and with high current. The aim of this seminar paper is to give some information how MOAs can be tested in laboratory circumstances and on- site. Few new test methods are introduced as well. (orig.)

  18. Methanol Oxidation on Model Elemental and Bimetallic Transition Metal Surfaces

    DEFF Research Database (Denmark)

    Tritsaris, G. A.; Rossmeisl, J.

    2012-01-01

    Direct methanol fuel cells are a key enabling technology for clean energy conversion. Using density functional theory calculations, we study the methanol oxidation reaction on model electrodes. We discuss trends in reactivity for a set of monometallic and bimetallic transition metal surfaces, flat...... sites on the surface and to screen for novel bimetallic surfaces of enhanced activity. We suggest platinum copper surfaces as promising anode catalysts for direct methanol fuel cells....

  19. Research Update: Interface-engineered oxygen octahedral tilts in perovskite oxide heterostructures

    Directory of Open Access Journals (Sweden)

    Daisuke Kan

    2015-06-01

    Full Text Available Interface engineering of structural distortions is a key for exploring the functional properties of oxide heterostructures and superlattices. In this paper, we report on our comprehensive investigations of oxygen octahedral distortions at the heterointerface between perovskite oxides SrRuO3 and BaTiO3 on GdScO3 substrates and of the influences of the interfacially engineered distortions on the magneto-transport properties of the SrRuO3 layer. Our state-of-the-art annular bright-field imaging in aberration-corrected scanning transmission electron microscopy revealed that the RuO6 octahedral distortions in the SrRuO3 layer have strong dependence on the stacking order of the SrRuO3 and BaTiO3 layers on the substrate. This can be attributed to the difference in the interfacial octahedral connections. We also found that the stacking order of the oxide layers has a strong impact on the magneto-transport properties, allowing for control of the magnetic anisotropy of the SrRuO3 layer through interface engineering. Our results demonstrate the significance of the interface engineering of the octahedral distortions on the structural and physical properties of perovskite oxides.

  20. Effect of recasting on the thickness of metal-ceramic interface of nickel-chromium and cobalt-chromium alloys

    Directory of Open Access Journals (Sweden)

    Mirković Nemanja

    2008-01-01

    Full Text Available Introduction/Aim. This research was done to establish recasting effects of nickel-chromium and cobalt-chromium alloys on the thickness of their metal-ceramic interface in making fixed partial dentures. Metal-ceramic interface determines their functional integrity and prevents damages on ceramics during mastication. Investigation of metal-ceramic samples is supposed to show if base metal alloys for metalceramics are successfully recycled without any risk of reduction of metal-ceramic interface thickness. Methods. The research was performed as an experimental study. Per six metal-ceramic samples of nickel-chromium alloy (Wiron99 and cobalt-chromium alloy (Wirobond C were made each. Alloy residues were recycled through twelve casting generations with the addition of 50% of new alloy on the occasion of every recasting. Analysis Energy Dispersive X-ray (EDX (Oxford Instruments and Scanning Electon Microscop (SEM analysis (JEOL were used to determine thickness of metal-ceramic interface together with PC Software for quantification of visual information's (KVI POPOVAC. Results. Results of this research introduced significant differences between thickness of metal-ceramic interface in every examined recycle generation. Recasting had negative effect on thickness of metal-ceramic interface of the examined alloys. This research showed almost linear reduction of elastic modulus up to the 12th generation of recycling. Conclusion. Recasting of nickel-chromium and cobaltchromium alloys is not recommended because of reduced thickness of metal-ceramic interface of these alloys. Instead of recycling, the alloy residues should be returned to the manufacturers.

  1. Metal oxide-encapsulated dye-sensitized photoanodes for dye-sensitized solar cells

    Science.gov (United States)

    Hupp, Joseph T.; Son, Ho-Jin

    2016-01-12

    Dye-sensitized semiconducting metal oxide films for photoanodes, photoanodes incorporating the films and DSCs incorporating the photoanodes are provided. Also provided are methods for making the dye sensitized semiconducting metal oxide films. The methods of making the films are based on the deposition of an encapsulating layer of a semiconducting metal oxide around the molecular anchoring groups of photosensitizing dye molecules adsorbed to a porous film of the semiconducting metal oxide. The encapsulating layer of semiconducting metal oxide is formed in such a way that it is not coated over the chromophores of the adsorbed dye molecules and, therefore, allows the dye molecules to remain electrochemically addressable.

  2. Directional dependence of the threshold displacement energies in metal oxides

    Science.gov (United States)

    Cowen, Benjamin J.; El-Genk, Mohamed S.

    2017-12-01

    Molecular dynamics (MD) simulations are performed to investigate the directional dependence and the values of the threshold energies (TDEs) for the displacements of the oxygen and metal atoms and for producing stable Frenkel pairs in five metal oxides of Cr2O3, Al2O3, TiO2, SiO2, and MgO. The TDEs for the Frenkel pairs and atoms displacement are calculated in 66 crystallographic directions, on both the anion and cation sublattices. The performed simulations are for metal and oxygen PKA energies up to 350 and 400 eV, respectively. The calculated probability distributions for the atoms displacement and average number of Frenkel pairs produced in the different oxides are compared. The results revealed unique symmetrical patterns of the TDEs for the displacement of the atoms and the formation of stable Frenkel pairs, confirming the strong dependence on the direction and the crystalline structure of the oxides. Results also showed that the formation of stable Frenkel pairs is associated with the displacements of the PKAs and/or of the SKAs. The probabilities of the TDEs for the displacement of the oxygen and metal PKAs are consistently lower than those of the atoms in the crystal. In SiO2, TDEs for the displacement of oxygen and metal atoms and those for the formation of stable Frenkel pairs are the lowest, while those in TiO2 are among the highest. The results for Cr2O3 and Al2O3, which have the same crystal structure, are similar. The calculated TDEs for MgO, Al2O3 and TiO2 are generally in good agreement with the experimental values and the probability distributions of the TDEs for the PKAs in TiO2 are in good agreement with reported MD simulation results.

  3. High performance supercapacitors using metal oxide anchored graphene nanosheet electrodes

    KAUST Repository

    Baby, Rakhi Raghavan

    2011-01-01

    Metal oxide nanoparticles were chemically anchored onto graphene nanosheets (GNs) and the resultant composites - SnO2/GNs, MnO2/GNs and RuO2/GNs (58% of GNs loading) - coated over conductive carbon fabric substrates were successfully used as supercapacitor electrodes. The results showed that the incorporation of metal oxide nanoparticles improved the capacitive performance of GNs due to a combination of the effect of spacers and redox reactions. The specific capacitance values (with respect to the composite mass) obtained for SnO2/GNs (195 F g-1) and RuO 2/GNs (365 F g-1) composites at a scan rate of 20 mV s-1 in the present study are the best ones reported to date for a two electrode configuration. The resultant supercapacitors also exhibited high values for maximum energy (27.6, 33.1 and 50.6 W h kg-1) and power densities (15.9, 20.4 and 31.2 kW kg-1) for SnO2/GNs, MnO2/GNs and RuO2/GNs respectively. These findings demonstrate the importance and great potential of metal oxide/GNs based composite coated carbon fabric in the development of high-performance energy-storage systems. © 2011 The Royal Society of Chemistry.

  4. Size characterization of metal oxide nanoparticles in commercial sunscreen products

    Science.gov (United States)

    Bairi, Venu Gopal; Lim, Jin-Hee; Fong, Andrew; Linder, Sean W.

    2017-07-01

    There is an increase in the usage of engineered metal oxide (TiO2 and ZnO) nanoparticles in commercial sunscreens due to their pleasing esthetics and greater sun protection efficiency. A number of studies have been done concerning the safety of nanoparticles in sunscreen products. In order to do the safety assessment, it is pertinent to develop novel analytical techniques to analyze these nanoparticles in commercial sunscreens. This study is focused on developing analytical techniques that can efficiently determine particle size of metal oxides present in the commercial sunscreens. To isolate the mineral UV filters from the organic matrices, specific procedures such as solvent extraction were identified. In addition, several solvents (hexane, chloroform, dichloromethane, and tetrahydrofuran) have been investigated. The solvent extraction using tetrahydrofuran worked well for all the samples investigated. The isolated nanoparticles were characterized by using several different techniques such as transmission electron microscopy, scanning electron microscopy, dynamic light scattering, differential centrifugal sedimentation, and x-ray diffraction. Elemental analysis mapping studies were performed to obtain individual chemical and morphological identities of the nanoparticles. Results from the electron microscopy techniques were compared against the bulk particle sizing techniques. All of the sunscreen products tested in this study were found to contain nanosized (≤100 nm) metal oxide particles with varied shapes and aspect ratios, and four among the 11 products were showed to have anatase TiO2.

  5. Metal inhibition on the reactivity of manganese dioxide toward organic contaminant oxidation in relation to metal adsorption and ionic potential.

    Science.gov (United States)

    Jiang, Jing; Wang, Zhuopu; Chen, Yang; He, Anfei; Li, Jianliang; Sheng, G Daniel

    2017-03-01

    Coexisting metal ions may significantly inhibit the oxidative reactivity of manganese oxides toward organic contaminants in metal-organic multi-pollutant waters. While the metal inhibition on the oxidation of organic contaminants by manganese oxides has previously been reported, the extent of the inhibition in relation to metal properties has not been established. Six alkali, alkaline, and transition metals, as well as two testing metals were evaluated for their abilities to inhibit the reactivity of birnessite. Regardless of the pathways of phenol and diuron oxidation (polymerization vs. breakdown), the extent of metal inhibition depended mainly on the metal itself and its concentration. The observed metal inhibition efficiency followed the order of Mn 2+  > Co 2+  > Cu 2+  > Al 3+  > Mg 2+  > K + , consistent with metal adsorption on birnessite. The first-order organic oxidation rate constant (k obs ) was linearly negatively correlated with metal adsorption (q e ) on birnessite. These observations demonstrated that the metal inhibition efficiency was determined by metal adsorption on birnessite. The slopes of the k obs -q e varied among metals and followed the order of K +  > Ca 2+  > Mg 2+  > Mn 2+  > Cd 2+  > Co 2+  > Cu 2+  > Al 3+ . These slopes defined intrinsic inhibitory abilities of metals. As metals were adsorbed hydrated on birnessite, the intrinsic inhibitory ability was significantly linearly correlated with ionic potentials of metals, leading to a single straight line. Metals with multiple d electrons in the outermost orbit with polarizing energy that promotes hydrolysis sat slightly below the line, and vice versa. Copyright © 2016 Elsevier Ltd. All rights reserved.

  6. Migration of trace heavy metals at the sea water/sediment interface

    International Nuclear Information System (INIS)

    Terada, Kikuo; Tomiyama, Chisato

    1984-01-01

    Migration behavior of some trace heavy metals such as Co(II), Cu(II), Mn(II) and Zn(II) at the sea water/sediment interface was investigated by tank experiments. The sea water which was doped with these metal ions (ppb to ppm levels) allowed to contact with the raw-, ignited- and autoclaved-marine sediments and the change of the concentration of each metal was traced at definite time intervals. At the end of the experiments, a core sample of the sediment was taken and analyzed for each metal in every 1 mm thick segment. On the other hand, the surface sediment was submitted to partial extraction with various kinds of reagents to estimate the chemical species of the metals captured in the sediment. While every metal ion was quickly adsorbed on surface of the raw sediment, a concentration gradient from surface to bottom of the water phase occurred in the ignited sediment system. The migration of manganese to the sediment phase was assumed to be concerned with bacterial activity in the sediment. Copper and zinc seemed to be adsorbed very quickly onto some fine sediment particles by the formation of organometallic complexes with some organic materials existing in the sediments. Cobalt migrated relatively fast downward within the sediment phase after its deposition. (author)

  7. Performance of metal and oxide fuels during accidents in a large liquid metal cooled reactor

    International Nuclear Information System (INIS)

    Cahalan, J.; Wigeland, R.; Friedel, G.; Kussmaul, G.; Royl, P.; Moreau, J.; Perks, M.

    1990-01-01

    In a cooperative effort among European and US analysts, an assessment of the comparative safety performance of metal and oxide fuels during accidents in a large (3500 MWt), pool-type, liquid-metal-cooled reactor (LMR) was performed. The study focused on three accident initiators with failure to scram: the unprotected loss-of-flow (ULOF), the unprotected transient overpower (UTOP), and the unprotected loss-of-heat-sink (ULOHS). Emphasis was placed on identification of design features that provide passive, self-limiting responses to upset conditions, and quantification of relative safety margins. The analyses show that in ULOF and ULOHS sequences, metal-fueled LMRs with pool-type primary systems provide larger temperature margins to coolant boiling than oxide-fueled reactors of the same design. 3 refs., 4 figs

  8. A polarity-induced defect mechanism for conductivity and magnetism at polar-nonpolar oxide interfaces.

    Science.gov (United States)

    Yu, Liping; Zunger, Alex

    2014-10-13

    The discovery of conductivity and magnetism at the polar-nonpolar interfaces of insulating nonmagnetic oxides such as LaAlO3 and SrTiO3 has raised prospects for attaining interfacial functionalities absent in the component materials. Yet, the microscopic origin of such emergent phenomena remains unclear, posing obstacles to design of improved functionalities. Here we present first principles calculations of electronic and defect properties of LaAlO3/SrTiO3 interfaces and reveal a unifying mechanism for the origins of both conductivity and magnetism. We demonstrate that the polar discontinuity across the interface triggers thermodynamically the spontaneous formation of certain defects that in turn cancel the polar field induced by the polar discontinuity. The ionization of the spontaneously formed surface oxygen vacancy defects leads to interface conductivity, whereas the unionized Ti-on-Al antisite defects lead to interface magnetism. The proposed mechanism suggests practical design principles for inducing and controlling both conductivity and magnetism at general polar-nonpolar interfaces.

  9. Observation of band bending of metal/high-k Si capacitor with high energy x-ray photoemission spectroscopy and its application to interface dipole measurement

    Science.gov (United States)

    Kakushima, K.; Okamoto, K.; Tachi, K.; Song, J.; Sato, S.; Kawanago, T.; Tsutsui, K.; Sugii, N.; Ahmet, P.; Hattori, T.; Iwai, H.

    2008-11-01

    Band bendings of Si substrates have been observed using hard x-ray photoemission spectroscopy. With a capability of collecting photoelectrons generated as deep as 40 nm, the binding energy shift in a core level caused by the potential profile at the surface of the substrate results in a spectrum broadening. The broadening is found to be significant when heavily doped substrates are used owing to its steep potential profile. The surface potential of the substrate can be obtained by deconvolution of the spectrum. This method has been applied to observe the band bending profile of metal-oxide-semiconductor capacitors with high-k gate dielectrics. By comparing the band bending profiles of heavily-doped n+- and p+-Si substrates, the interface dipoles presented at interfaces can be estimated. In the case of W gated La2O3/La-silicate capacitor, an interface dipole to shift the potential of -0.45 V has been estimated at La-silicate/Si interface, which effectively reduces the apparent work function of W. On the other hand, an interface dipole of 0.03-0.07 V has been found to exist at Hf-silicate/SiO2 interface for W gated HfO2/Hf-silicate/SiO2 capacitor.

  10. Oxidation of limonene catalyzed by Metal(Salen complexes

    Directory of Open Access Journals (Sweden)

    L. F. Lima

    2006-03-01

    Full Text Available The compound R-(+limonene is available and cheap than its oxidized products. Consequently, the selective oxidation of R(+limonene has attracted attention as a promising process for the production of compounds with a higher market value, such as cis/trans-1,2-limoneneoxide, cis/trans-carveol and/or carvone. One of the these processes, described in the recent literature, is submission of R-(+limonene to an oxidation reaction catalyzed by neutral or cationic Metal(Salen complexes, in the presence of effective terminal oxidants such as NaOCl or PhIO. These reactions are commonly carried out in organic solvents (dichromethane, ethyl acetate, acetonitrile or acetone. Thus, the main objective of the present work was to study the effect of several factors (type of oxidant, catalyst, solvent and time on reaction selectivity for the high-priced compounds referred to above. For this purposes, experimental statistical multivariate analysis was used in conjunction with a complete experimental design. From the results it was observed that for the three targeted products (1,2-limoneneoxide, carveol or carvone some factors, including the nature of the terminal oxidant and the catalyst, were significant for product selectivity (with a confidence level of 95%. Therefore, this statistical analysis proved to be suitable for choosing of the best reaction conditions for a specific desired product.

  11. Hydrocracking and hydroisomerization of long-chain alkanes and polyolefins over metal-promoted anion-modified transition metal oxides

    Energy Technology Data Exchange (ETDEWEB)

    Venkatesh, Koppampatti R.; Hu, Jianli; Tierney, John W.; Wender, Irving

    1996-12-01

    A method is described for cracking a feedstock by contacting the feedstock with a metal-promoted anion-modified metal oxide catalyst in the presence of hydrogen gas. The metal oxide of the catalyst is one or more of ZrO{sub 2}, HfO{sub 2}, TiO{sub 2} and SnO{sub 2}, and the feedstock is principally chains of at least 20 carbon atoms. The metal-promoted anion-modified metal oxide catalyst contains one or more of Pt, Ni, Pd, Rh, Ir, Ru, (Mn and Fe) or mixtures of them present between about 0.2% to about 15% by weight of the catalyst. The metal-promoted anion-modified metal oxide catalyst contains one or more of SO{sub 4}, WO{sub 3}, or mixtures of them present between about 0.5% to about 20% by weight of the catalyst.

  12. In situ X-ray absorption spectroscopy of transition metal based water oxidation catalysts.

    Science.gov (United States)

    van Oversteeg, Christina H M; Doan, Hoang Q; de Groot, Frank M F; Cuk, Tanja

    2017-01-03

    X-ray absorption studies of the geometric and electronic structure of primarily heterogeneous Co, Ni, and Mn based water oxidation catalysts are reviewed. The X-ray absorption near edge and extended X-ray absorption fine structure studies of the metal K-edge, characterize the metal oxidation state, metal-oxygen bond distance, metal-metal distance, and degree of disorder of the catalysts. These properties guide the coordination environment of the transition metal oxide radical that localizes surface holes and is required to oxidize water. The catalysts are investigated both as-prepared, in their native state, and under reaction conditions, while transition metal oxide radicals are generated. The findings of many experiments are summarized in tables. The advantages of future X-ray experiments on water oxidation catalysts, which include the limited data available of the oxygen K-edge, metal L-edge, and resonant inelastic X-ray scattering, are discussed.

  13. Thermodynamic properties of some metal oxide-zirconia systems

    Science.gov (United States)

    Jacobson, Nathan S.

    1989-01-01

    Metal oxide-zirconia systems are a potential class of materials for use as structural materials at temperatures above 1900 K. These materials must have no destructive phase changes and low vapor pressures. Both alkaline earth oxide (MgO, CaO, SrO, and BaO)-zirconia and some rare earth oxide (Y2O3, Sc2O3, La2O3, CeO2, Sm2O3, Gd2O3, Yb2O3, Dy2O3, Ho2O3, and Er2O3)-zirconia system are examined. For each system, the phase diagram is discussed and the vapor pressure for each vapor species is calculated via a free energy minimization procedure. The available thermodynamic literature on each system is also surveyed. Some of the systems look promising for high temperature structural materials.

  14. Ceria doped mixed metal oxide nanoparticles as oxidation catalysts: Synthesis and their characterization

    Directory of Open Access Journals (Sweden)

    S.S.P. Sultana

    2015-11-01

    Full Text Available Mixed metal nanoparticles (NPs have attracted significant attention as catalysts for various organic transformations. In this study, we have demonstrated the preparation of nickel–manganese mixed metal oxide NPs doped with X% nano cerium oxide (X = 1, 3, 5 mol% by a facile co-precipitation technique using surfactant and surfactant free methodologies. The as-synthesized materials were calcined at different temperatures (300 °C, 400 °C, and 500 °C, and were characterized using various spectroscopic techniques, including, FTIR and XRD. SEM analysis, TEM analysis and TGA were employed to evaluate the structural properties of the as-prepared catalyst. These were evaluated for their catalytic behaviour towards the conversion of benzyl alcohol to benzaldehyde, which was used as a model reaction with molecular oxygen as oxidant. Furthermore, the effect of the variation of the percentage of nano ceria doping and the calcination temperature on the performance of as-prepared mixed metal catalysts was also evaluated. The kinetic studies of the reactions performed employing gas chromatographic technique have revealed that the mixed metal oxide catalyst doped with 5% nano ceria displayed excellent catalytc activity, among various catalysts synthesized.

  15. Enhanced sun protection of nano-sized metal oxide particles over conventional metal oxide particles: an in vitro comparative study.

    Science.gov (United States)

    Singh, P; Nanda, A

    2014-06-01

    A systematic and detailed study has been designed and conducted, taking into account some of the proposed benefits such as increased efficiency, transparency, unique texture, protection of active ingredient and higher consumer compliance of cosmetics containing nano-sized metal oxides. This study also presents an in vitro method to determine sun protection factor of the investigational sunscreen cream samples containing zinc oxide and titanium dioxide with a varied range of particle size. Finally, a comparative study has been conducted between metal oxide particles, conventional as well as nanoparticles. All the skin cosmetics formulated were thermally stable with a pH ranging from 7.9 to 8.2. Moreover, the fatty acid substance content and residue were found to be analogous to the standard values in each skin cosmetic. The skin cosmetics containing the titanium or zinc oxide nanoparticles were found to have improved spreadability as compared to skin cosmetics containing conventional titanium or zinc oxide particles, respectively. All skin cosmetics were found to have uniform distribution of the particles. The sunscreen creams containing zinc oxide nanoparticles and titanium dioxide nanoparticles were found to have higher in vitro sun protection factor (SPF of 3.65 for ZnO nanoparticles and 4.93 for TiO2 nanoparticles) as compared to that of sunscreen creams containing conventional zinc oxide particles (SPF = 2.90) and conventional titanium dioxide (SPF = 1.29), clearly indicating the effect of reduction in particles size, from micro to nano, on the sun protection factor. Good texture, better spreadability and enhanced in vitro SPF proved the advantageous role of nanoparticles in cosmetics. © 2014 Society of Cosmetic Scientists and the Société Française de Cosmétologie.

  16. Metal oxides modified NiO catalysts for oxidative dehydrogenation of ethane to ethylene

    KAUST Repository

    Zhu, Haibo

    2014-06-01

    The sol-gel method was applied to the synthesis of Zr, Ti, Mo, W, and V modified NiO based catalysts for the ethane oxidative dehydrogenation reaction. The synthesized catalysts were characterized by XRD, N2 adsorption, SEM and TPR techniques. The results showed that the doping metals could be highly dispersed into NiO domains without the formation of large amount of other bulk metal oxide. The modified NiO materials have small particle size, larger surface area, and higher reduction temperature in contrast to pure NiO. The introduction of group IV, V and VI transition metals into NiO decreases the catalytic activity in ethane ODH. However, the ethylene selectivity is enhanced with the highest level for the Ni-W-O and Ni-Ti-O catalysts. As a result, these two catalysts show improved efficiency of ethylene production in the ethane ODH reaction. © 2014 Elsevier B.V. All rights reserved.

  17. A General Route for Growing Metal Sulfides onto Graphene Oxide and Exfoliated Graphite Oxide.

    Science.gov (United States)

    Lopes, Joana L; Estrada, Ana C; Fateixa, Sara; Ferro, Marta; Trindade, Tito

    2017-08-31

    Graphene-based materials are elective materials for a number of technologies due to their unique properties. Also, semiconductor nanocrystals have been extensively explored due to their size-dependent properties that make them useful for several applications. By coupling both types of materials, new applications are envisaged that explore the synergistic properties in such hybrid nanostructures. This research reports a general wet chemistry method to prepare graphene oxide (GO) sheets decorated with nanophases of semiconductor metal sulfides. This method allows the in situ growth of metal sulfides onto GO by using metal dialkyldithiocarbamate complexes as single-molecule precursors. In particular, the role of GO as heterogeneous substrate for the growth of semiconductor nanocrystals was investigated by using Raman spectroscopic and imaging methods. The method was further extended to other graphene-based materials, which are easily prepared in a larger scale, such as exfoliated graphite oxide (EGO).

  18. Interface Controlled Oxidation States in Layered Cobalt Oxide Nanoislands on Gold

    DEFF Research Database (Denmark)

    Walton, Alexander; Fester, Jakob; Bajdich, Michal

    2015-01-01

    Layered cobalt oxides have been shown to be highly active catalysts for the oxygen evolution reaction (OER; half of the catalytic “water splitting” reaction), particularly when promoted with gold. However, the surface chemistry of cobalt oxides and in particular the nature of the synergistic effect...

  19. The nano-bio interface mapped by oxidative footprinting of the adsorption sites of myoglobin.

    Science.gov (United States)

    Devineau, Stéphanie; Mathé, Christelle; Legros, Véronique; Gonnet, Florence; Daniel, Régis; Renault, Jean Philippe; Pin, Serge

    2014-12-01

    Oxidative footprinting has been used to study the structure of macromolecular assemblies such as protein-protein and protein-ligand complexes. We propose a novel development of this technique to probe the protein corona that forms at the surface of nanoparticles in any biological medium. Indeed, very few techniques allow studying this interface at the molecular and residue level. Based on hydroxyl radical-mediated oxidation of proteins and analysis by nanoscale liquid chromatography coupled to tandem mass spectrometry (nanoLC-MS/MS), two sites of adsorption of myoglobin on silica nanoparticles are identified. This method gives new insights in the understanding of protein adsorption on nanomaterials.

  20. Metal/metal oxide doped oxide catalysts having high deNOx selectivity for lean NOx exhaust aftertreatment systems

    Science.gov (United States)

    Park, Paul W.

    2004-03-16

    A lean NOx catalyst and method of preparing the same is disclosed. The lean NOx catalyst includes a ceramic substrate, an oxide support material, preferably .gamma.-alumina, deposited on the substrate and a metal promoter or dopant introduced into the oxide support material. The metal promoters or dopants are selected from the group consisting of indium, gallium, tin, silver, germanium, gold, nickel, cobalt, copper, iron, manganese, molybdenum, chromium, cerium, vanadium, oxides thereof, and combinations thereof. The .gamma.-alumina preferably has a pore volume of from about 0.5 to about 2.0 cc/g; a surface area of between about 80 to 350 m.sup.2 /g; an average pore size diameter of between about 3 to 30 nm; and an impurity level of less than or equal to 0.2 weight percent. In a preferred embodiment the .gamma.-alumina is prepared by a sol-gel method, with the metal doping of the .gamma.-alumina preferably accomplished using an incipient wetness impregnation technique.

  1. Evidence of discrete interface traps on thermally grown thin silicon oxide films

    Science.gov (United States)

    Cai, Jin; Sah, Chih-Tang

    1999-01-01

    A very-low density (oxide. Three signatures pointing to discreteness are delineated in the experimental data of the gate voltage modulation of the dc steady-state electron-hole recombination rate. Using the Shockley-Read-Hall recombination kinetics, the energy level is shown to have a linewidth less than 20 meV. From the present and previous data, the dopant impurity origin of this residual interface trap species is speculated rather than the amphoteric silicon dangling bonds.

  2. Fabrication of block copolymer templated mesoporous metal oxide composites for energy storage applications

    Science.gov (United States)

    Bhaway, Sarang M.

    Block copolymer templated mesoporous (2 nm-50 nm) metal oxides are considered promising electrode materials for energy storage devices such as electrochemical capacitors or lithium/sodium ion batteries. The mesoporous electrode morphology offers several advantages: (1) high surface area and porosity facilitate charge transfer across the electrolyte-electrode interface, (2) nanoscale-dimension of the oxide framework minimizes the solid state ion diffusion paths, and (3) interconnected porous morphology enables rapid electrolyte transport through the electrodes, leading to overall enhancement in charge storage capabilities. This research attempts to study the effect of mesoporosity and mesopore geometry on charge storage capabilities and cycling stability of ordered mesoporous metal oxide electrodes in energy storage devices. The first part of this dissertation focuses on fabrication of ordered mesoporous metal oxide composites utilizing the Evaporation Induced Self-Assembly (EISA) and the Block Copolymer Micelle Templating (BCMT) strategy. Firstly, we demonstrate fabrication of ordered mesoporous carbon-vanadium oxide composites utilizing EISA of phenolic resin oligomer (resol), VOCl3 and an amphiphilic triblock. We illustrate that carbon yield from resol carbonization can prevent break-out crystallization of vanadia during calcination and help maintain an ordered mesostructure. The mesoporous carbon-vanadia mesostructured thin films exhibit specific capacitance 7 times higher than their non-porous analog at high scan rates when tested as electrode in aqueous supercapacitor. The second part of this thesis focuses on BCMT technique to fabricate ordered mesoporous mixed-metal oxide electrodes for battery applications. Ordered mesoporous NixCo(3-x)O4 thin films with varying chemical composition are fabricated using a metal nitrate-citric acid complex and an amphiphilic PEGMA-b-PBA block copolymer template. This templating strategy is further extended to fabricate

  3. The crystal chemistry of inorganic metal borohydrides and their relation to metal oxides.

    Science.gov (United States)

    Černý, Radovan; Schouwink, Pascal

    2015-12-01

    The crystal structures of inorganic homoleptic metal borohydrides are analysed with respect to their structural prototypes found amongst metal oxides in the inorganic databases such as Pearson's Crystal Data [Villars & Cenzual (2015). Pearson's Crystal Data. Crystal Structure Database for Inorganic Compounds, Release 2014/2015, ASM International, Materials Park, Ohio, USA]. The coordination polyhedra around the cations and the borohydride anion are determined, and constitute the basis of the structural systematics underlying metal borohydride chemistry in various frameworks and variants of ionic packing, including complex anions and the packing of neutral molecules in the crystal. Underlying nets are determined by topology analysis using the program TOPOS [Blatov (2006). IUCr CompComm. Newsl. 7, 4-38]. It is found that the Pauling rules for ionic crystals apply to all non-molecular borohydride crystal structures, and that the latter can often be derived by simple deformation of the close-packed anionic lattices c.c.p. and h.c.p., by partially removing anions and filling tetrahedral or octahedral sites. The deviation from an ideal close packing is facilitated in metal borohydrides with respect to the oxide due to geometrical and electronic considerations of the BH4(-) anion (tetrahedral shape, polarizability). This review on crystal chemistry of borohydrides and their similarity to oxides is a contribution which should serve materials engineers as a roadmap to design new materials, synthetic chemists in their search for promising compounds to be prepared, and materials scientists in understanding the properties of novel materials.

  4. Constrained-DFT method for accurate energy-level alignment of metal/molecule interfaces

    KAUST Repository

    Souza, A. M.

    2013-10-07

    We present a computational scheme for extracting the energy-level alignment of a metal/molecule interface, based on constrained density functional theory and local exchange and correlation functionals. The method, applied here to benzene on Li(100), allows us to evaluate charge-transfer energies, as well as the spatial distribution of the image charge induced on the metal surface. We systematically study the energies for charge transfer from the molecule to the substrate as function of the molecule-substrate distance, and investigate the effects arising from image-charge confinement and local charge neutrality violation. For benzene on Li(100) we find that the image-charge plane is located at about 1.8 Å above the Li surface, and that our calculated charge-transfer energies compare perfectly with those obtained with a classical electrostatic model having the image plane located at the same position. The methodology outlined here can be applied to study any metal/organic interface in the weak coupling limit at the computational cost of a total energy calculation. Most importantly, as the scheme is based on total energies and not on correcting the Kohn-Sham quasiparticle spectrum, accurate results can be obtained with local/semilocal exchange and correlation functionals. This enables a systematic approach to convergence.

  5. Electroreflectance spectroscopy as a probe of the electronic structure at the metal-electronic interface

    Energy Technology Data Exchange (ETDEWEB)

    Ho, K.M.; Liu, S.H.

    1984-01-01

    The electromagnetic response of a surface is influenced by the surface electronic structure. In particular, the existence of surface states in band gaps can lead to optical absorption below the bulk interband threshold. However, such effects are usually too small to be observed because while surface states are localized within several atomic layers near the surface, light waves can penetrate at least hundreds of layers into the metal. One way to enhance the surface effect for a metallic surface is to make use of electromodulation techniques. When a metal is placed in an electrolyte, an intense electric field (approx. 10/sup 7/ volts/cm) can be induced at the metal-electrolyte boundary with the application of a bias voltage of less than a volt. Electroreflectance (ER) experiments modulate the bias voltage and measure the resultant modulations in the optical reflectivity. Since the static electric field is highly localized at the interface (the Fermi-Thomas screening length for typical metals is of the order of Angstroms) we expect the ER effect to be highly surface sensitive. Sensitivities in ..delta..R/R up to 10/sup -6/ can be achieved in such experiments. 12 references.

  6. Promotion of Water-mediated Carbon Removal by Nanostructured Barium Oxide/nickel Interfaces

    Energy Technology Data Exchange (ETDEWEB)

    L Yang; Y Choi; W Qin; H Chen; K Blinn; M Liu; P Liu; J Bai; T Tyson; M Liu

    2011-12-31

    The existing Ni-yttria-stabilized zirconia anodes in solid oxide fuel cells (SOFCs) perform poorly in carbon-containing fuels because of coking and deactivation at desired operating temperatures. Here we report a new anode with nanostructured barium oxide/nickel (BaO/Ni) interfaces for low-cost SOFCs, demonstrating high power density and stability in C{sub 3}H{sub 8}, CO and gasified carbon fuels at 750 C. Synchrotron-based X-ray analyses and microscopy reveal that nanosized BaO islands grow on the Ni surface, creating numerous nanostructured BaO/Ni interfaces that readily adsorb water and facilitate water-mediated carbon removal reactions. Density functional theory calculations predict that the dissociated OH from H2O on BaO reacts with C on Ni near the BaO/Ni interface to produce CO and H species, which are then electrochemically oxidized at the triple-phase boundaries of the anode. This anode offers potential for ushering in a new generation of SOFCs for efficient, low-emission conversion of readily available fuels to electricity.

  7. Chemical Bonding, Interfaces and Defects in Hafnium Oxide/Germanium Oxynitride Gate Stacks on Ge (100)

    Energy Technology Data Exchange (ETDEWEB)

    Oshima, Yasuhiro; /Stanford U., Materials Sci. Dept.; Sun, Yun; /SLAC, SSRL; Kuzum, Duygu; /Stanford U.; Sugawara, Takuya; Saraswat, Krishna C.; Pianetta, Piero; /SLAC, SSRL; McIntyre, Paul C.; /Stanford U., Materials Sci. Dept.

    2008-10-31

    Correlations among interface properties and chemical bonding characteristics in HfO{sub 2}/GeO{sub x}N{sub y}/Ge MIS stacks were investigated using in-situ remote nitridation of the Ge (100) surface prior to HfO{sub 2} atomic layer deposition (ALD). Ultra thin ({approx}1.1 nm), thermally stable and aqueous etch-resistant GeO{sub x}N{sub y} interfaces layers that exhibited Ge core level photoelectron spectra (PES) similar to stoichiometric Ge{sub 3}N{sub 4} were synthesized. To evaluate GeO{sub x}N{sub y}/Ge interface defects, the density of interface states (D{sub it}) was extracted by the conductance method across the band gap. Forming gas annealed (FGA) samples exhibited substantially lower D{sub it} ({approx} 1 x 10{sup 12} cm{sup -2} eV{sup -1}) than did high vacuum annealed (HVA) and inert gas anneal (IGA) samples ({approx} 1x 10{sup 13} cm{sup -2} eV{sup -1}). Germanium core level photoelectron spectra from similar FGA-treated samples detected out-diffusion of germanium oxide to the HfO{sub 2} film surface and apparent modification of chemical bonding at the GeO{sub x}N{sub y}/Ge interface, which is related to the reduced D{sub it}.

  8. Metal Oxide/Semiconductor Heterojunctions as Carrier-Selective Contacts for Photovoltaic Applications

    Science.gov (United States)

    Man, Gabriel Jen Shi

    Solar radiation is a vast, distributed, and renewable energy source which Humanity can utilize via the photovoltaic effect. The goal of photovoltaic technology is to minimize the true costs, while maximizing the power conversion efficiency and lifetime of the cell/module. Interface-related approaches to achieving this goal are explored here, for two technologically-important classes of light absorbers: crystalline-silicon (c-Si) and metal halide perovskite (MHP). The simplest solar cell consists of a light absorber, sandwiched between two metals with dissimilar work functions. Carrier-selective contacts (CSC's), which are ubiquitous in modern solar cells, are added to improve the electrical performance. Solar cells require asymmetric carrier transport within the cell, which can be effected via electrostatic and/or effective fields, and CSC's augment the asymmetry by selectively transporting holes to one contact, and electrons to the other contact. The proper design and implementation of a CSC is crucial, as the performance, lifetime, and/or cost reduction of a solar cell can be hampered by a single interface or layer. A framework, consisting of eight core requirements, was developed from first-principles to evaluate the effectiveness of a given CSC. The framework includes some requirements which are well-recognized, such as the need for appropriate band offsets, and some requirements which are not well-recognized at the moment, such as the need for effective valence/conduction band density of states matching between the absorber and CSC. The application of the framework to multiple silicon-based and MHP-based CSC's revealed the difficulties of effectively designing and implementing a CSC. A poly(3-hexylthiophene)/c-Si heterojunction was found to be a near ideal hole-selective contact (HSC). Three metal oxide/c-Si heterojunctions initially expected to yield comparable electron-selective contacts (ESC's), titanium dioxide/c-Si (TiO2/c-Si), zinc oxide/c-Si (Zn

  9. Heat-resistant organic molecular layer as a joint interface for metal reduction on plastics surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Sang, Jing [Department of Frontier Materials and Function Engineering, Graduate School of Engineering, Iwate University, 4-3-5 Ueda, Morioka 020-8551 (Japan); Aisawa, Sumio, E-mail: aisawa@iwate-u.ac.jp [Department of Frontier Materials and Function Engineering, Graduate School of Engineering, Iwate University, 4-3-5 Ueda, Morioka 020-8551 (Japan); Hirahara, Hidetoshi [Department of Frontier Materials and Function Engineering, Graduate School of Engineering, Iwate University, 4-3-5 Ueda, Morioka 020-8551 (Japan); Kudo, Takahiro [Sulfur Chemical Institute, 210, Collabo MIU, 4-3-5, Ueda, Morioka 020-0066 (Japan); Mori, Kunio [Department of Frontier Materials and Function Engineering, Graduate School of Engineering, Iwate University, 4-3-5 Ueda, Morioka 020-8551 (Japan); Sulfur Chemical Institute, 210, Collabo MIU, 4-3-5, Ueda, Morioka 020-0066 (Japan)

    2016-04-15

    Graphical abstract: - Highlights: • In situ adsorption behaviors of TES on PA6 surface were clarified by QCM. • Highest adsorption of TES on PA6 was obtained in pH 3 and 0.1 M solution. • Molecular layers of TES with uniform structures were prepared on PA6 surface. • TES layer improved PA6 local heat resistance from 150 °C to 230 °C. • TES molecular layer successfully reduced Ag ion to Ag{sup 0}. - Abstract: Heat-resistant organic molecular layers have been fabricated by triazine-based silane coupling agent for metal reduction on plastic surfaces using adsorption method. These molecular layers were used as an interfacial layer between polyamide (PA6) and metal solution to reduce Ag{sup +} ion to Ag{sup 0}. The interfacial behaviors of triazine molecular layer at the interfaces between PA6 and Ag solution were investigated using quartz crystal microbalance (QCM). The kinetics of molecular adsorption on PA6 was investigated by using triazine-based silane coupling agent solutions at different pH and concentration. X-ray photoelectron spectroscopy (XPS), atomic force microscope (AFM), and local nano thermal analysis were employed to characterize the surfaces and interfaces. The nano thermal analysis results show that molecular layers of triazine-based silane coupling agent greatly improved heat resistance of PA6 resin from 170 °C up to 230 °C. This research developed an in-depth insight for molecular behaviors of triazine-based silane coupling agent at the PA6 and Ag solution interfaces and should be of significant value for interfacial research between plastics and metal solution in plating industry.

  10. [Synthesis and characterization of mixed metal oxide pigments].

    Science.gov (United States)

    Ding, Jie; Yue, Shi-juan; Liu, Cui-ge; Wei, Yong-ju; Meng, Tao; Jiang, Han-jie; Shi, Yong-zheng; Xu, Yi-zhuang; Yu, Jiang; Wu, Jin-guang

    2012-03-01

    In the present work, aluminum chloride and various soluble salts of doping ions were dissolved in water. In addition, urea and polyvinyl pyrrolidone (PVP) were also dissolved in the above aqueous solution under supersonic treatments. Then the solutions were heated to induce the hydrolysis of urea so that soluble aluminum and doping ions convert into insoluble hydroxide or carbonate gels. After calcinations, the obtained gels change to mixed metal oxide pigments whose color is related to type and concentrations of the doping ions. XRD characterization demonstrates that the diffraction patterns of the products are the same as that of alpha-alumina. Diffuse reflectance spectra of samples of the samples in UV-Vis regions show that the absorption bands for d-d transitions of the doping ions undergo considerable change as the coordinate environments change. In addition, L*, a* and b* values of the pigments were measured by using UV-Vis densitometer. SEM results indicate that the size of the pigment powders is in the range 200-300 nm. The pigments are quite stable since no evidence of dissolution was observed after the synthesized pigment is soaked for 24 hours. ICP test shows that very little amount of doped metal occurs in the corresponding filtrate. The above results suggest that these new kinds of mixed metal oxide pigments are stable, non-toxic, environmental friendly and they may be applicable in molten spinning process and provide a new chance for non-aqueous printing and dyeing industry.

  11. Metal oxide multilayer hard mask system for 3D nanofabrication

    Science.gov (United States)

    Han, Zhongmei; Salmi, Emma; Vehkamäki, Marko; Leskelä, Markku; Ritala, Mikko

    2018-02-01

    We demonstrate the preparation and exploitation of multilayer metal oxide hard masks for lithography and 3D nanofabrication. Atomic layer deposition (ALD) and focused ion beam (FIB) technologies are applied for mask deposition and mask patterning, respectively. A combination of ALD and FIB was used and a patterning procedure was developed to avoid the ion beam defects commonly met when using FIB alone for microfabrication. ALD grown Al2O3/Ta2O5/Al2O3 thin film stacks were FIB milled with 30 keV gallium ions and chemically etched in 5% tetramethylammonium hydroxide at 50 °C. With metal evaporation, multilayers consisting of amorphous oxides Al2O3 and Ta2O5 can be tailored for use in 2D lift-off processing, in preparation of embedded sub-100 nm metal lines and for multilevel electrical contacts. Good pattern transfer was achieved by lift-off process from the 2D hard mask for micro- and nano-scaled fabrication. As a demonstration of the applicability of this method to 3D structures, self-supporting 3D Ta2O5 masks were made from a film stack on gold particles. Finally, thin film resistors were fabricated by utilizing controlled stiction of suspended Ta2O5 structures.

  12. Process for producing metal oxide kernels and kernels so obtained

    International Nuclear Information System (INIS)

    Lelievre, Bernard; Feugier, Andre.

    1974-01-01

    The process desbribed is for producing fissile or fertile metal oxide kernels used in the fabrication of fuels for high temperature nuclear reactors. This process consists in adding to an aqueous solution of at least one metallic salt, particularly actinide nitrates, at least one chemical compound capable of releasing ammonia, in dispersing drop by drop the solution thus obtained into a hot organic phase to gel the drops and transform them into solid particles. These particles are then washed, dried and treated to turn them into oxide kernels. The organic phase used for the gel reaction is formed of a mixture composed of two organic liquids, one acting as solvent and the other being a product capable of extracting the anions from the metallic salt of the drop at the time of gelling. Preferably an amine is used as product capable of extracting the anions. Additionally, an alcohol that causes a part dehydration of the drops can be employed as solvent, thus helping to increase the resistance of the particles [fr

  13. Metal oxide films on glass and steel substrates

    CERN Document Server

    Sohi, A M

    1987-01-01

    in the pH8 electrolyte supports the view that the rate limiting reduction reaction is possibly oxygen (or water) reduction although some contribution from an organic 'impurity' cannot be ruled out. Coatings of Fe sub 3 O sub 4 on mild steel have been prepared by CVD using pneumatic spraying techniques and the corrosion behaviour of coated electrodes in organic-phosphate electrolyte (pH8) has been examined. A variety of thin (10-1000nm) metal oxide films have been deposited on flat glass substrates by the pyrolysis of an aerosol of metal acetylacetonates in a suitable carrier. The optical characteristics and thickness of the films have been measured and particular interest has centered on the use of a novel pin on disc apparatus to measure the physical durability of such thin films. Characteristic friction/penetration force traces have been established for 1st Series transition metal oxide films and some ranking in terms of 'hardness' established. The use of SnO sub 2 - coated glass for electrodes in a light m...

  14. Vanadium removal by metal (hydr)oxide adsorbents.

    Science.gov (United States)

    Naeem, A; Westerhoff, P; Mustafa, S

    2007-04-01

    Vanadium is listed on the United States Environment Protection Agency (USEPA) candidate contaminant list # 2 (CCL2), and regulatory guidelines for vanadium exist in some US states. The USEPA requires treatability studies before making regulatory decisions on CCL2 contaminants. Previous studies have examined vanadium adsorption onto some metal hydroxides but not onto commercially available adsorbents. This paper briefly summarizes known vanadium occurrence in North American groundwater and assesses vanadium removal by three commercially available metal oxide adsorbents with different mineralogies. GTO (Dow) is TiO2 based and E-33 (Seven Trents) and GFH (US Filter) are iron based. Preliminary vanadate adsorption kinetics onto GFH, E-33 and GTO has been studied and the homogenous surface diffusion model (HSDM) is used to describe the adsorption kinetics data. The effects of pH, vanadium concentration, and volume/mass ratio are assessed. Vanadium adsorption decreases with increasing pH, with maximum adsorption capacities achieved in at pH 3-4. Results indicate that all adsorbents remove vanadium; GFH has the highest adsorption capacity, followed by GTO and E-33. Data are best fit with the Langmuir model rather than Freundlich isotherms. Both the sorption maxima (Xm) and binding energy constant (b) follow the trend GFH>GTO>E-33. Naturally occurring vanadium is also removed from Arizona ground water in rapid small-scale column tests (RSSCTs). Metal oxide adsorption technologies currently used for arsenic removal may also remove vanadium but not always with the same effectiveness.

  15. First-principles study of van der Waals interactions and lattice mismatch at MoS2/metal interfaces

    NARCIS (Netherlands)

    Farmanbar Gelepordsari, M.; Brocks, G.

    2016-01-01

    We explore the adsorption of MoS 2 on a range of metal substrates by means of first-principles density functional theory calculations. Including van der Waals forces in the density functional is essential to capture the interaction between MoS 2 and a metal surface, and obtain reliable interface

  16. The influence of surface oxide on the growth of metal/semiconductor nanowires.

    Science.gov (United States)

    Lu, Kuo-Chang; Wu, Wen-Wei; Ouyang, Hao; Lin, Yung-Chen; Huang, Yu; Wang, Chun-Wen; Wu, Zheng-Wei; Huang, Chun-Wei; Chen, Lih J; Tu, K N

    2011-07-13

    We report the critical effects of oxide on the growth of nanostructures through silicide formation. Under an in situ ultrahigh vacuum transmission electron microscope, it is observed from the conversion of Si nanowires into the metallic PtSi grains epitaxially through controlled reactions between lithographically defined Pt pads and Si nanowires. With oxide, instead of contact area, single crystal PtSi grains start forming either near the center between two adjacent pads or from the ends of Si nanowires, resulting in the heterostructure formation of Si/PtSi/Si. Without oxide, transformation from Si into PtSi begins at the contact area between them, resulting in the heterostructure formation of PtSi/Si/PtSi. The nanowire heterostructures have an atomically sharp interface with epitaxial relationships of Si(20-2)//PtSi(10-1) and Si[111]//PtSi[111]. Additionally, it has been observed that the existence of oxide significantly affects not only the growth position but also the growth behavior and the growth rate by two orders of magnitude. Molecular dynamics simulations have been performed to support our experimental results and the proposed growth mechanisms. In addition to fundamental science, the significance of the study matters for future processing techniques in nanotechnology and related applications as well.

  17. Study on uranium metallization yield of spent Pressurized Water Reactor fuels and oxidation behavior of fission products in uranium metals

    International Nuclear Information System (INIS)

    Choi, Ke Chon; Lee, Chang Heon; Kim, Won Ho

    2003-01-01

    Metallization yield of uranium oxide to uranium metal from lithium reduction process of spent Pressurized Water Reactor (PWR) fuels was measured using thermogravimetric analyzer. A reduced metal produced in the process was divided into a solid and a powder part, and each metallization yield was measured. Metallization yield of the solid part was 90.7∼95.9 wt%, and the powder being 77.8∼71.5 wt% individually. Oxidation behaviour of the quarternary alloy was investigated to take data on the thermal oxidation stability necessary for the study on dry storage of the reduced metal. At 600∼700 .deg. C, weight increments of allow of No, Ru, Rh and Pd was 0.40∼0.55 wt%. Phase change on the surface of the allow was started at 750 .deg. C. In particular, Mo was rapidly oxidized and then the alloy lost 0.76∼25.22 wt% in weight

  18. CO oxidation on PtSn nanoparticle catalysts occurs at the interface of Pt and Sn oxide domains formed under reaction conditions

    KAUST Repository

    Michalak, William D.

    2014-04-01

    The barrier to CO oxidation on Pt catalysts is the strongly bound adsorbed CO, which inhibits O2 adsorption and hinders CO2 formation. Using reaction studies and in situ X-ray spectroscopy with colloidally prepared, monodisperse ∼2 nm Pt and PtSn nanoparticle catalysts, we show that the addition of Sn to Pt provides distinctly different reaction sites and a more efficient reaction mechanism for CO oxidation compared to pure Pt catalysts. To probe the influence of Sn, we intentionally poisoned the Pt component of the nanoparticle catalysts using a CO-rich atmosphere. With a reaction environment comprised of 100 Torr CO and 40 Torr O2 and a temperature range between 200 and 300 C, Pt and PtSn catalysts exhibited activation barriers for CO2 formation of 133 kJ/mol and 35 kJ/mol, respectively. While pure Sn is readily oxidized and is not active for CO oxidation, the addition of Sn to Pt provides an active site for O2 adsorption that is important when Pt is covered with CO. Sn oxide was identified as the active Sn species under reaction conditions by in situ ambient pressure X-ray photoelectron spectroscopy measurements. While chemical signatures of Pt and Sn indicated intermixed metallic components under reducing conditions, Pt and Sn were found to reversibly separate into isolated domains of Pt and oxidic Sn on the nanoparticle surface under reaction conditions of 100 mTorr CO and 40 mTorr O2 between temperatures of 200-275 C. Under these conditions, PtSn catalysts exhibited apparent reaction orders in O2 for CO 2 production that were 0.5 and lower with increasing partial pressures. These reaction orders contrast the first-order dependence in O 2 known for pure Pt. The differences in activation barriers, non-first-order dependence in O2, and the presence of a partially oxidized Sn indicate that the enhanced activity is due to a reaction mechanism that occurs at a Pt/Sn oxide interface present at the nanoparticle surface. © 2014 Published by Elsevier Inc.

  19. Pure and multi metal oxide nanoparticles: synthesis, antibacterial and cytotoxic properties.

    Science.gov (United States)

    Stankic, Slavica; Suman, Sneha; Haque, Francia; Vidic, Jasmina

    2016-10-24

    Th antibacterial activity of metal oxide nanoparticles has received marked global attention as they can be specifically synthesized to exhibit significant toxicity to bacteria. The importance of their application as antibacterial agents is evident keeping in mind the limited range and effectiveness of antibiotics, on one hand, and the plethora of metal oxides, on the other, along with the propensity of nanoparticles to induce resistance being much lower than that of antibiotics. Effective inhibition against a wide range of bacteria is well known for several nano oxides consisting of one metal (Fe 3 O 4 , TiO 2 , CuO, ZnO), whereas, research in the field of multi-metal oxides still demands extensive exploration. This is understandable given that the relationship between physicochemical properties and biological activity seems to be complex and difficult to generalize even for metal oxide nanoparticles consisting of only one metal component. Also, despite the broad scope that metal oxide nanoparticles have as antibacterial agents, there arise problems in practical applications taking into account the cytotoxic effects. In this respect, the consideration of polymetallic oxides for biological applications becomes even greater since these can provide synergetic effects and unify the best physicochemical properties of their components. For instance, strong antibacterial efficiency specific of one metal oxide can be complemented by non-cytotoxicity of another. This review presents the main methods and technological advances in fabrication of nanostructured metal oxides with a particular emphasis to multi-metal oxide nanoparticles, their antibacterial effects and cytotoxicity.

  20. Planar Indium Tin Oxide Heater for Improved Thermal Distribution for Metal Oxide Micromachined Gas Sensors.

    Science.gov (United States)

    Çakır, M Cihan; Çalışkan, Deniz; Bütün, Bayram; Özbay, Ekmel

    2016-09-29

    Metal oxide gas sensors with integrated micro-hotplate structures are widely used in the industry and they are still being investigated and developed. Metal oxide gas sensors have the advantage of being sensitive to a wide range of organic and inorganic volatile compounds, although they lack selectivity. To introduce selectivity, the operating temperature of a single sensor is swept, and the measurements are fed to a discriminating algorithm. The efficiency of those data processing methods strongly depends on temperature uniformity across the active area of the sensor. To achieve this, hot plate structures with complex resistor geometries have been designed and additional heat-spreading structures have been introduced. In this work we designed and fabricated a metal oxide gas sensor integrated with a simple square planar indium tin oxide (ITO) heating element, by using conventional micromachining and thin-film deposition techniques. Power consumption-dependent surface temperature measurements were performed. A 420 °C working temperature was achieved at 120 mW power consumption. Temperature distribution uniformity was measured and a 17 °C difference between the hottest and the coldest points of the sensor at an operating temperature of 290 °C was achieved. Transient heat-up and cool-down cycle durations are measured as 40 ms and 20 ms, respectively.