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Sample records for titanate srtio3 st

  1. Orthorhombic strontium titanate in BaTiO sub 3 -SrTiO sub 3 superlattices

    CERN Document Server

    Rios, S; Jiang, A Q; Scott, J F; Lü, H; Chen, Z

    2003-01-01

    It has been suggested by several authors that SrTiO sub 3 layers in SrTiO sub 3 -BaTiO sub 3 superlattices should be tetragonal and ferroelectric at ambient temperatures, like the BaTiO sub 3 layers, rather than cubic, as in bulk SrTiO sub 3 , and that free-energy minimization requires continuity of the polarization direction. A recent ab initio calculation constrained solutions to this structure. Surprisingly, our x-ray study shows that the SrTiO sub 3 layers are orthorhombic with 0.03% in-plane strain, with the BaTiO sub 3 c-axis matching the SrTiO sub 3 a- and b-axis better than the c-axis; strain energy overcomes the cost in electrostatic energy. (letter to the editor)

  2. Synthesis of BaTiO3 and SrTiO3 by microwave assisted hydrothermal method (MAH) using anatase as titanium precursor

    International Nuclear Information System (INIS)

    Magalhães, Renata da Silva; Macedo Junior, Wagner Dias; Souza, Agda Eunice de; Teixeira, Silvio Rainho; Li, Maximo Siu; Longo, Elson

    2016-01-01

    Full text: Strontium and barium titanates (SrTiO 3 (ST) and BaTiO 3 (BT)) in their crystalline form belong to the perovskite (ABO 3 ) class. Both display a semiconductor behavior with many interesting properties. The method of synthesis employed and different precursors may influence the morphology and properties of ceramic materials [1,2]. Barium (BT) and strontium (St) titanates were produced using the Microwave Assisted Hydrothermal Method (MAH), different concentrations (1,3 and 6 molL -1 ) of mineralizer (KOH) and a different titanium precursor: a complex anatase-hydrogen peroxide. Barium and strontium chloride were used as the other metal precursors. The resulting material were characterized by different techniques such as: X-ray diffraction (XRD), Micro-Raman Spectroscopy (MR), UV-Vis, Scanning Electron microscopy (SEM) and finally their photoluminescent emissions (FL) were recorded at room temperature. The results show that there were differences in crystallinity, morphology, number of formed phases and photoluminescent emission, among the titanate produced with different concentrations of mineralizer. References: [1] A.E. Souza et al., Order–disorder degree of self-assembled clusters: Influence on photoluminescence emission and morphology of Ba x Sr 1-x TiO 3 nanocrystals, Chemical Physics Letters 514 (2011) 301–306. [2] T. M. Mazzo et al., Influence of titanium precursor on photoluminescent emission of micro-cube-shaped CaTiO 3 , Journal of Luminescence 165 (2015). (author)

  3. Studies on Gas Sensing Performance of Pure and Surface Modified SrTiO3 Thick Film Resistors

    Directory of Open Access Journals (Sweden)

    V. B. Gaikwad

    2009-08-01

    Full Text Available Strontium Titanate (SrTiO3 (ST was prepared mechanochemically from Sr(OH2 and TiO2. XRD confirms the Perovskite phase of material. Thick films of ST were prepared by screen-printing technique. The gas sensing performances of thick films were tested for various gases. It showed maximum sensitivity to CO gas at 350 oC for 100 ppm gas concentration. To improve the sensitivity and selectivity of the film towards a particular gas, ST thick films were surface modified by dipping them in a solution of nano copper for different intervals of time. These surface modified ST films showed larger sensitivity to H2S gas (100 ppm at 300 oC than pure ST film. A systematic study, of sensing performance of the sensor, indicates the key role-played by the nano copper species on the surface .The sensitivity, selectivity, response and recovery time of the sensor were measured and presented.

  4. Resistance switching of the interfacial conductance in amorphous SrTiO3 heterostructures

    DEFF Research Database (Denmark)

    Christensen, Dennis; Trier, Felix; Chen, Yunzhong

    Complex oxides have attracted a lot of interest recently as this class of material exhibits a plethora of remarkable properties. In particular, a great variety of properties is observed in the heterostructure composed of lanthanum aluminate (LaAlO3) and strontium titanate (SrTiO3). For instance...

  5. Effect of Sr/Ti Ratio on the Photocatalytic Properties of SrTiO3

    International Nuclear Information System (INIS)

    Sulaeman, U; Yin, S; Sato, T

    2011-01-01

    Since strontium titanate is a wide gap semiconductor, it requires UV light to generate the photocatalytic activities. Modification of strontium titanate to show photocatalytic activity under visible light irradiation is the essential work to efficiently utilize the sun light energy for environmental application. It is expected that the synthesis of SrTiO 3 with variation of Sr/Ti atomic ratio could induce the defect crystals having unique photocatalytic properties. The SrTiO 3 with various Sr/Ti atomic ratios were synthesized by microwave-assisted solvothermal reaction of SrCl 2 .6H 2 O and Ti(OC 3 H 7 ) 4 in KOH aqueous solutions with different atomic ratios of Sr/Ti. The products were characterized by TG-DTA, XRD and DRS. The photocatalytic activity was determined by DeNO x ability using LED lamps with the wavelengths of 627 nm (red), 530 nm (green), 445 nm (blue) and 390 nm (UV). The nanoparticles of perovskite type SrTiO 3 with the particle size of 30-40 nm were successfully synthesized. The visible light responsive photocatalytic activity was generated by adding excess amount of Sr. The photocatalytic activity in visible light could be enhanced by an increase in the Sr/Ti atomic ratio up to 1.25, indicating that the visible light responsive photocatalytic activity is due to the generation of new band gap between the conduction band and valence band of SrTiO 3 by the formation of oxygen vacancy.

  6. Molecular dynamics simulations of oxygen vacancy diffusion in SrTiO3

    International Nuclear Information System (INIS)

    Schie, Marcel; Marchewka, Astrid; Waser, Rainer; Müller, Thomas; De Souza, Roger A

    2012-01-01

    A classical force-field model with partial ionic charges was applied to study the behaviour of oxygen vacancies in the perovskite oxide strontium titanate (SrTiO 3 ). The dynamical behaviour of these point defects was investigated as a function of temperature and defect concentration by means of molecular dynamics (MD) simulations. The interaction between oxygen vacancies and an extended defect, here a Σ3(111) grain boundary, was also examined by means of MD simulations. Analysis of the vacancy distribution revealed considerable accumulation of vacancies in the envelope of the grain boundary. The possible clustering of oxygen vacancies in bulk SrTiO 3 was studied by means of static lattice calculations within the Mott-Littleton approach. All binary vacancy-vacancy configurations were found to be energetically unfavourable.

  7. Molecular dynamics simulations of oxygen vacancy diffusion in SrTiO3.

    Science.gov (United States)

    Schie, Marcel; Marchewka, Astrid; Müller, Thomas; De Souza, Roger A; Waser, Rainer

    2012-12-05

    A classical force-field model with partial ionic charges was applied to study the behaviour of oxygen vacancies in the perovskite oxide strontium titanate (SrTiO(3)). The dynamical behaviour of these point defects was investigated as a function of temperature and defect concentration by means of molecular dynamics (MD) simulations. The interaction between oxygen vacancies and an extended defect, here a Σ3(111) grain boundary, was also examined by means of MD simulations. Analysis of the vacancy distribution revealed considerable accumulation of vacancies in the envelope of the grain boundary. The possible clustering of oxygen vacancies in bulk SrTiO(3) was studied by means of static lattice calculations within the Mott-Littleton approach. All binary vacancy-vacancy configurations were found to be energetically unfavourable.

  8. Etude de capacités en couches minces à base d'oxydes métalliques à très forte constante diélectrique, BaTiO3, SrTiO3 et SrTiO3/BaTiO3 déposées par pulvérisation par faisceau d'ions

    OpenAIRE

    Guillan , Julie

    2005-01-01

    In a view of miniaturization in microelectronics and more particularly in the sector of mobile phone, perovskites materials with very high permittivity are interesting candidates to replace dielectrics currently used in the development of Metal/Insulator/Metal (MIM) capacitor. This work is devoted to the development and the characterization of thin layers of strontium titanate (SrTiO3) and barium titanate (BaTiO3) deposited by Ion Beam Sputtering (IBS) in capacitive structure Pt/high-k/Pt.An ...

  9. Localized versus itinerant states created by multiple oxygen vacancies in SrTiO3

    Science.gov (United States)

    Jeschke, Harald O.; Shen, Juan; Valentí, Roser

    2015-02-01

    Oxygen vacancies in strontium titanate surfaces (SrTiO3) have been linked to the presence of a two-dimensional electron gas with unique behavior. We perform a detailed density functional theory study of the lattice and electronic structure of SrTiO3 slabs with multiple oxygen vacancies, with a main focus on two vacancies near a titanium dioxide terminated SrTiO3 surface. We conclude based on total energies that the two vacancies preferably inhabit the first two layers, i.e. they cluster vertically, while in the direction parallel to the surface, the vacancies show a weak tendency towards equal spacing. Analysis of the nonmagnetic electronic structure indicates that oxygen defects in the surface TiO2 layer lead to population of Ti {{t}2g} states and thus itinerancy of the electrons donated by the oxygen vacancy. In contrast, electrons from subsurface oxygen vacancies populate Ti eg states and remain localized on the two Ti ions neighboring the vacancy. We find that both the formation of a bound oxygen-vacancy state composed of hybridized Ti 3eg and 4p states neighboring the oxygen vacancy as well as the elastic deformation after extracting oxygen contribute to the stabilization of the in-gap state.

  10. Electronic structure and topography of annealed SrTiO3(1 1 1) surfaces studied with MIES and STM

    International Nuclear Information System (INIS)

    Goemann, Anissa; Goemann, Karsten; Frerichs, Martin; Kempter, Volker; Borchardt, Guenter; Maus-Friedrichs, Wolfgang

    2005-01-01

    Perovskites of ABO 3 type like strontium titanate (SrTiO 3 ) are of great practical concern as materials for oxygen sensors operating at high temperatures. It is well known that the surface layer shows different properties compared to the bulk. Numerous studies exist for the SrTiO 3 (1 0 0) and (1 1 0) surfaces which have investigated the changes in the electronic structure and topography as a function of the preparation conditions. They have indicated a rather complex behaviour of the surface and the near surface region of SrTiO 3 at elevated temperatures. Up to now, the behaviour of the SrTiO 3 (1 1 1) surfaces under thermal treatment is not sufficiently known. This contribution is intended to work out the relation between alteration of the surface topography with respect to the preparation conditions and the simultaneous changes of the electronic structure. We applied scanning tunneling microscopy (STM) to investigate the surface topography and, additionally, metastable impact electron spectroscopy (MIES) to study the surface electronic structure of reconstructed SrTiO 3 (1 1 1) surfaces. The crystals were heated up to 1000 deg. C under reducing and oxidizing conditions. Both preparation conditions cause strong changes of the surface topography and electronic structure. A microfaceting of the topmost layers is found

  11. The synthesis of SrTiO3 nanocubes and the analysis of nearly ideal diode application of Ni/SrTiO3 nanocubes/n-Si heterojunctions

    Science.gov (United States)

    Bilal Taşyürek, Lütfi; Sevim, Melike; Çaldıran, Zakir; Aydogan, Sakir; Metin, Önder

    2018-01-01

    A perovskite type of strontium titanate (SrTiO3) nanocubes (NCs) were synthesized by using a hydrothermal process and the thin films of these NCs were deposited on an n-type silicon wafer by spin coating technique. As-synthesized SrTiO3 NCs were characterized by transmission electron microscope, scanning electron microscope, energy dispersive x-ray, x-ray diffraction and Raman spectroscopy. After evaporation of 12 Ni dots on the SrTiO3 NCs thin films deposited on n-Si, the Ni/SrTiO3 NCs/n-Si heterojunction devices were fabricated for the first time. The ideality factors of the twelve fabricated devices were vary from 1.05 to 1.22 and the barrier height values varied from 0.64 to 0.68 eV. Furthermore, since all devices yielded similar characteristics, only the current-voltage and the capacitance-voltage of one selected device (named H1) were investigated in detailed. The series resistance of this device was calculated as 96 Ω.

  12. Persistent optically induced magnetism in oxygen-deficient strontium titanate.

    Science.gov (United States)

    Rice, W D; Ambwani, P; Bombeck, M; Thompson, J D; Haugstad, G; Leighton, C; Crooker, S A

    2014-05-01

    Strontium titanate (SrTiO3) is a foundational material in the emerging field of complex oxide electronics. Although its bulk electronic and optical properties are rich and have been studied for decades, SrTiO3 has recently become a renewed focus of materials research catalysed in part by the discovery of superconductivity and magnetism at interfaces between SrTiO3 and other non-magnetic oxides. Here we illustrate a new aspect to the phenomenology of magnetism in SrTiO3 by reporting the observation of an optically induced and persistent magnetization in slightly oxygen-deficient bulk SrTiO3-δ crystals using magnetic circular dichroism (MCD) spectroscopy and SQUID magnetometry. This zero-field magnetization appears below ~18 K, persists for hours below 10 K, and is tunable by means of the polarization and wavelength of sub-bandgap (400-500 nm) light. These effects occur only in crystals containing oxygen vacancies, revealing a detailed interplay between magnetism, lattice defects, and light in an archetypal complex oxide material.

  13. Enhanced photocatalytic activity of SrTiO3 photocatalyst by topotactic preparation

    Science.gov (United States)

    Cao, Jiafeng; Huang, Xianshan; Liu, Yi; Wu, Jianguang; Ji, Yuexia

    2016-11-01

    Novel SrTiO3 (ST) photocatalysts with different shapes such as plates, rods and cubes were successfully synthesized based on a topotactic approach. The rod-like ST particles formed in situ at the plates show superior photocatalytic activities towards the decomposition of Rhodamine B than the plate-like and the cubic particles under visible-light irradiation, which could be attributed to the crystal orientation exposing highly active sites accompanied by the crystallite growth in molten salt. The results reveal an effective approach for fabrication of novel photocatalysts of perovskite structure with enhanced photocatalytic activities.

  14. Electronic properties and surface reactivity of SrO-terminated SrTiO3 and SrO-terminated iron-doped SrTiO3.

    Science.gov (United States)

    Staykov, Aleksandar; Tellez, Helena; Druce, John; Wu, Ji; Ishihara, Tatsumi; Kilner, John

    2018-01-01

    Surface reactivity and near-surface electronic properties of SrO-terminated SrTiO 3 and iron doped SrTiO 3 were studied with first principle methods. We have investigated the density of states (DOS) of bulk SrTiO 3 and compared it to DOS of iron-doped SrTiO 3 with different oxidation states of iron corresponding to varying oxygen vacancy content within the bulk material. The obtained bulk DOS was compared to near-surface DOS, i.e. surface states, for both SrO-terminated surface of SrTiO 3 and iron-doped SrTiO 3 . Electron density plots and electron density distribution through the entire slab models were investigated in order to understand the origin of surface electrons that can participate in oxygen reduction reaction. Furthermore, we have compared oxygen reduction reactions at elevated temperatures for SrO surfaces with and without oxygen vacancies. Our calculations demonstrate that the conduction band, which is formed mainly by the d-states of Ti, and Fe-induced states within the band gap of SrTiO 3 , are accessible only on TiO 2 terminated SrTiO 3 surface while the SrO-terminated surface introduces a tunneling barrier for the electrons populating the conductance band. First principle molecular dynamics demonstrated that at elevated temperatures the surface oxygen vacancies are essential for the oxygen reduction reaction.

  15. Optical properties of SrTiO3 films

    International Nuclear Information System (INIS)

    Agasiyev, A.A.; Magerramov, E.M.; Mammadov, M.Z.; Sarmasov, S.M.

    2010-01-01

    The spectrums of optical absorption of amorphous and single crystalline films SrTiO 3 at temperatures : 105 K, 300 K, 400 K are investigated. The temperature dependences of slope absorption edge, forbidden gap and characteristic constant of Urbah rule are obtained. The forbidden gap of single crystalline film SrTiO 3 and average shift shift of absorption edge degree are defined. It is established that edge of optical absorption of SrTiO 3 film is obeyed to Urbah rule and the absorption in the investigated region is caused by the transition of electron interacting with phonon

  16. Dielectric enhancement of BaTiO3/SrTiO3 superlattices with embedded Ni nanocrystals

    International Nuclear Information System (INIS)

    Xiong Zhengwei; Sun Weiguo; Wang Xuemin; Jiang Fan; Wu Weidong

    2012-01-01

    Highlights: ► The BaTiO 3 /SrTiO 3 superlattices with embedded Ni NCs were successfully fabricated by L-MBE. ► The influence with the various concentrations of Ni nanocrystals embedded in BaTiO 3 /SrTiO 3 superlattices was also discussed. ► The BaTiO 3 /SrTiO 3 superlattices with lower concentration of embedded Ni NCs had higher permittivity and dielectric loss compared with the pure BaTiO 3 /SrTiO 3 superlattices. ► The dielectric enhancement of BaTiO 3 /SrTiO 3 superlattices with embedded Ni NCs was proposed to explained by Drude quasi-free-electron theory. - Abstract: The self-organized Ni nanocrystals (NCs) were embedded in BaTiO 3 /SrTiO 3 superlattices using laser molecular beam epitaxy (L-MBE). The stress of the composite films was increased with the increasing concentration of embedded Ni NCs, as investigation in stress calculation. The influence with the various concentrations of Ni NCs embedded in BaTiO 3 /SrTiO 3 superlattices was also discussed. The internal stress of the films was too strong to epitaxial growth of BaTiO 3 /SrTiO 3 superlattices. Compared with the pure BaTiO 3 /SrTiO 3 superlattices, the BaTiO 3 /SrTiO 3 superlattices with lower concentration of embedded Ni NCs had higher permittivity and dielectric loss. Furthermore, the dielectric enhancement of BaTiO 3 /SrTiO 3 superlattices with embedded Ni NCs was proposed to explained by Drude quasi-free-electron theory.

  17. Quantitative analysis of UV excitation bands for red emissions in Pr3+-doped CaTiO3, SrTiO3 and BaTiO3 phosphors by peak fitting

    International Nuclear Information System (INIS)

    Fujiwara, Rei; Sano, Hiroyuki; Shimizu, Mikio; Kuwabara, Makoto

    2009-01-01

    A quantitative spectral analysis of the ultraviolet (UV) broad excitation bands, which are located in the range 300-400 nm, for red emissions at around 610 nm in Pr-doped CaTiO 3 , SrTiO 3 :Al and BaTiO 3 :Mg phosphors has been carried out using a peak fitting technique. The obtained results demonstrate that the UV broad band of CaTiO 3 :Pr consists of four primary excitation bands centered around 330, 335, 365 and 380 nm and those of both SrTiO 3 :Al and BaTiO 3 :Mg consist of three primary bands centered around 310, 345 and 370 nm. Based on the behavior patterns and the values of the respective primary excitation bands' parameters, i.e. center gravity (λ top ), maximum height (I max ) and full-width at half-maximum (FWHM), the UV-to-red relaxation processes in these titanate phosphors can be explained to be essentially the same, except for the existence of an additional relaxation pathway via electron-trap states in CaTiO 3 :Pr, which gives a characteristic shape of its UV excitation spectrum in the wavelength range of >360 nm

  18. Imaging and tuning polarity at SrTiO3 domain walls

    Science.gov (United States)

    Frenkel, Yiftach; Haham, Noam; Shperber, Yishai; Bell, Christopher; Xie, Yanwu; Chen, Zhuoyu; Hikita, Yasuyuki; Hwang, Harold Y.; Salje, Ekhard K. H.; Kalisky, Beena

    2017-12-01

    Electrostatic fields tune the ground state of interfaces between complex oxide materials. Electronic properties, such as conductivity and superconductivity, can be tuned and then used to create and control circuit elements and gate-defined devices. Here we show that naturally occurring twin boundaries, with properties that are different from their surrounding bulk, can tune the LaAlO3/SrTiO3 interface 2DEG at the nanoscale. In particular, SrTiO3 domain boundaries have the unusual distinction of remaining highly mobile down to low temperatures, and were recently suggested to be polar. Here we apply localized pressure to an individual SrTiO3 twin boundary and detect a change in LaAlO3/SrTiO3 interface current distribution. Our data directly confirm the existence of polarity at the twin boundaries, and demonstrate that they can serve as effective tunable gates. As the location of SrTiO3 domain walls can be controlled using external field stimuli, our findings suggest a novel approach to manipulate SrTiO3-based devices on the nanoscale.

  19. Infrared characterization of strontium titanate thin films

    International Nuclear Information System (INIS)

    Almeida, B.G.; Pietka, A.; Mendes, J.A.

    2004-01-01

    Strontium titanate thin films have been prepared at different oxygen pressures with various post-deposition annealing treatments. The films were deposited by pulsed laser ablation at room temperature on Si(0 0 1) substrates with a silica buffer layer. Infrared reflectance measurements were performed in order to determine relevant film parameters such as layer thicknesses and chemical composition. The infrared reflectance spectra were fitted by using adequate dielectric function forms for each layer. The fitting procedure provided the extraction of the dielectric functions of the strontium titanate film, the silica layer and the substrate. The as-deposited films are found to be amorphous, and their infrared spectra present peaks corresponding to modes with high damping constants. As the annealing time and temperature increases the strontium titanate layer becomes more ordered so that it can be described by its SrTiO 3 bulk mode parameters. Also, the silica layer grows along with the ordering of the strontium titanate film, due to oxidation during annealing

  20. Positron annihilation studies on the behaviour of vacancies in LaAlO3/SrTiO3 heterostructures

    Science.gov (United States)

    Yuan, Guoliang; Li, Chen; Yin, Jiang; Liu, Zhiguo; Wu, Di; Uedono, Akira

    2012-11-01

    The formation and diffusion of vacancies are studied in LaAlO3/SrTiO3 heterostructures. Oxygen vacancies (VOS) appear easily in the SrTiO3 substrate during LaAlO3 film growth at 700 °C and 10-4 Pa oxygen pressure rather than at 10-3-10-1 Pa, thus the latter two-dimensional electron gas should come from the polarity discontinuity at the (LaO)+/(TiO2)0 interface. For SrTiO3-δ/LaAlO3/SrTiO3, high-density VOS of the SrTiO3-δ film can pass through the LaAlO3 film and then diffuse to 1.7 µm depth in the SrTiO3 substrate, suggesting that LaAlO3 has VOS at its middle-deep energy levels within the band gap. Moreover, high-density VOS may combine with a strontium/titanium vacancy (VSr/Ti) to form VSr/Ti-O complexes in the SrTiO3 substrate at 700 °C.

  1. Anion and cation diffusion in barium titanate and strontium titanate

    International Nuclear Information System (INIS)

    Kessel, Markus Franz

    2012-01-01

    data suggests that oxygen vacancies and electron holes play the key role in the formation of the equilibrium surface space-charge layers. The oxygen vacancy diffusivities and the oxygen vacancy migration enthalpy are compared to other experimentally and theoretically derived data for barium titanate and a global expression for the temperature dependence of the oxygen vacancy diffusivity is determined. The latter was used for a comparison of the oxygen vacancy diffusivity and the oxygen vacancy migration enthalpy for BaTiO 3 to other perovskite oxides. Furthermore, this work shows results from cation interdiffusion experiments between BaZrO 3 and SrTiO 3 . Thin films of barium zirconate were deposited on strontium titanate single crystals and the cation interdiffusion investigated as a function of temperature. All four cations show a main diffusion profile and an additional fast diffusion profile. Each main diffusion profile can be described independently by the thick-film solution of the diffusion equation suggesting the diffusion coefficients to be concentration independent. The fast diffusion profiles are attributed to fast diffusion of Ba and Zr along dislocations of the SrTiO 3 single crystals and fast diffusion of Sr and Ti along the grain boundaries of the polycrystalline thin-film BaZrO 3 . The migration enthalpies of the bulk profiles for all four cations are very similar. The results suggest a complex diffusion mechanism with coupled diffusion of the cation vacancies on the A and B sites of the perovskite lattice.

  2. Fatigue-resistant epitaxial Pb(Zr,Ti)O3 capacitors on Pt electrode with ultra-thin SrTiO3 template layers

    International Nuclear Information System (INIS)

    Takahara, Seiichi; Morimoto, Akiharu; Kawae, Takeshi; Kumeda, Minoru; Yamada, Satoru; Ohtsubo, Shigeru; Yonezawa, Yasuto

    2008-01-01

    Lead zirconate-titanate Pb(Zr,Ti)O 3 (PZT) capacitors with Pt bottom electrodes were prepared on MgO substrates by pulsed laser deposition (PLD) technique employing SrTiO 3 (STO) template layer. Perovskite PZT thin films are prepared via stoichiometric target using the ultra-thin STO template layers while it is quite difficult to obtain the perovskite PZT on Pt electrode via stoichiometric target in PLD process. The PZT capacitor prepared with the STO template layer showed good hysteresis and leakage current characteristics, and it showed an excellent fatigue resistance. The ultra-thin STO template layers were characterized by angle-resolved X-ray photoelectron spectroscopy measurement. The effect of the STO template layer is discussed based on the viewpoint of the perovskite nucleation and diffusion of Pb and O atoms

  3. Metastable honeycomb SrTiO_3/SrIrO_3 heterostructures

    International Nuclear Information System (INIS)

    Anderson, T. J.; Ryu, S.; Podkaminer, J. P.; Ma, Y.; Eom, C. B.; Zhou, H.; Xie, L.; Irwin, J.; Rzchowski, M. S.; Pan, X. Q.

    2016-01-01

    Recent theory predictions of exotic band topologies in (111) honeycomb perovskite SrIrO_3 layers sandwiched between SrTiO_3 have garnered much attention in the condensed matter physics and materials communities. However, perovskite SrIrO_3 film growth in the (111) direction remains unreported, as efforts to synthesize pure SrIrO_3 on (111) perovskite substrates have yielded films with monoclinic symmetry rather than the perovskite structure required by theory predictions. In this study, we report the synthesis of ultra-thin metastable perovskite SrIrO_3 films capped with SrTiO_3 grown on (111) SrTiO_3 substrates by pulsed laser deposition. The atomic structure of the ultra-thin films was examined with scanning transmission electron microscopy (STEM), which suggests a perovskite layering distinct from the bulk SrIrO_3 monoclinic phase. In-plane 3-fold symmetry for the entire heterostructure was confirmed using synchrotron surface X-ray diffraction to measure symmetry equivalent crystal truncation rods. Our findings demonstrate the ability to stabilize (111) honeycomb perovskite SrIrO_3, which provides an experimental avenue to probe the phenomena predicted for this material system.

  4. Carrier density modulation by structural distortions at modified LaAlO3/SrTiO3 interfaces

    International Nuclear Information System (INIS)

    Schoofs, Frank; Vickers, Mary E; Egilmez, Mehmet; Fix, Thomas; Kleibeuker, Josée E; MacManus-Driscoll, Judith L; Blamire, Mark G; Carpenter, Michael A

    2013-01-01

    In order to study the fundamental conduction mechanism of LaAlO 3 /SrTiO 3 (LAO/STO) interfaces, heterostructures were modified with a single unit cell interface layer of either an isovalent titanate ATiO 3 (A = Ca, Sr, Sn, Ba) or a rare earth modified Sr 0.5 RE 0.5 TiO 3 (RE = La, Nd, Sm, Dy) between the LAO and the STO. A strong coupling between the lattice strain induced in the LAO layer by the interfacial layers and the sheet carrier density in the STO substrate is observed. The observed crystal distortion of the LAO is large and it is suggested that it couples into the sub-surface STO, causing oxygen octahedral rotation and deformation. We propose that the ‘structural reconstruction’ which occurs in the STO surface as a result of the stress in the LAO is the enabling trigger for two-dimensional conduction at the LAO/STO interface by locally changing the band structure and releasing trapped carriers. (paper)

  5. Evolution of the SrTiO3/MoO3 interface electronic structure: An in situ photoelectron spectroscopy study

    KAUST Repository

    Du, Yuanmin; Peng, Haiyang; Mao, Hongying; Jin, Kexin; Wang, Hong; Li, Feng; Gao, Xingyu; Chen, Wei; Wu, Tao

    2015-01-01

    Modifying the surface energetics, particularly the work function, of advanced materials is of critical importance for a wide range of surface- and interface-based devices. In this work, using in situ photoelectron spectroscopy, we investigated the evolution of electronic structure at the SrTiO3 surface during the growth of ultrathin MoO3 layers. Thanks to the large work function difference between SrTiO3 and MoO3, the energy band alignment on the SrTiO3 surface is significantly modified. The charge transfer and dipole formation at the SrTiO3/MoO3 interface leads to a large modulation of work function and an apparent doping in SrTiO3. The measured evolution of electronic structure and upward band bending suggest that the growth of ultrathin MoO3 layers is a powerful tool to modulate the surface energetics of SrTiO3, and this surface-engineering approach could be generalized to other functional oxides.

  6. Evolution of the SrTiO3/MoO3 interface electronic structure: An in situ photoelectron spectroscopy study

    KAUST Repository

    Du, Yuanmin

    2015-05-12

    Modifying the surface energetics, particularly the work function, of advanced materials is of critical importance for a wide range of surface- and interface-based devices. In this work, using in situ photoelectron spectroscopy, we investigated the evolution of electronic structure at the SrTiO3 surface during the growth of ultrathin MoO3 layers. Thanks to the large work function difference between SrTiO3 and MoO3, the energy band alignment on the SrTiO3 surface is significantly modified. The charge transfer and dipole formation at the SrTiO3/MoO3 interface leads to a large modulation of work function and an apparent doping in SrTiO3. The measured evolution of electronic structure and upward band bending suggest that the growth of ultrathin MoO3 layers is a powerful tool to modulate the surface energetics of SrTiO3, and this surface-engineering approach could be generalized to other functional oxides.

  7. Resistive switching phenomena of extended defects in Nb-doped SrTiO3 under influence of external gradients

    International Nuclear Information System (INIS)

    Rodenbuecher, Christian

    2014-01-01

    Redox-based memristive materials have attracted much attention in the last decade owing to their ability to change the resistance upon application of an electric field making them promising candidates for future non-volatile memories. However, a fundamental understanding of the nature of the resistive switching effect, which is indispensable for designing future technological applications,is still lacking. As a prototype material of a memristive oxide, strontium titanate (SrTiO 3 ) has been investigated intensively and it was revealed that the valence change of a Ti ''d'' electron plays an important role during resistive switching related to insulator-to-metal transition. Such a transition can be induced by electrical gradients, by chemical gradients, by a combination of these gradients or by donor doping. Hence, SrTiO 3 doped with the donor Nb should have metallic properties and is used commonly as a conducting substrate for the growth of functional oxide thin films. Nevertheless,the resistive switching effect has also be observed in Nb-doped SrTiO 3 . This paradoxical situation offers a unique opportunity to gain an insight into the processes during the insulator-to metal transition. In this thesis, a comprehensive study of the influence of external gradients on SrTiO 3 :Nb single crystals is presented. The focus is especially set on the investigation of the crystallographic structure, the chemical composition, the electronic structure, the lattice dynamics and the electronic transport phenomena using surface-sensitive methods on the macro- and nanoscale. On the as-received epi-polished single crystals, the evolution of a surface layer having a slight excess of strontium and - in contrast to the bulk of the material - semiconducting properties are observed. Hence, the key for understanding of the resistive switching effect is the knowledge of the nature of the surface layer. On the basis of systematic studies of the influence of external

  8. Deposition of SrTiO3 films by electrophoresis with thickness and particle size control

    International Nuclear Information System (INIS)

    Junior, W.D.M.; Pena, A.F.V.; Souza, A.E.; Santos, G.T.A.; Teixeira, S.R.; Senos, A.M.R.; Longo, E.

    2012-01-01

    The SrTiO3 (ST) is a material that exhibits semiconducting characteristics and interesting electrical properties. In room temperature has a structure of high cubic symmetry. The size of the crystallites of this material directly influences this symmetry, changing its network parameters. ST nanoparticles are obtained by hydrothermal method assisted by microwave (MAH). ST films are prepared by electrophoretic deposition (EPD). Approximately 1 g of the powder is dissolved in 100 ml of acetone and 1.5 ml of triethanolamine. The stainless steel substrates are arranged horizontally in the solution. The depositions are performed for 1-10 min and subjected to a potential difference of 20-100 V. The films were characterized by x-ray diffraction (XRD) and atomic force microscopy (AFM). The characterizations show that it is possible to control both the thickness and size of the crystallites of the film depending on the deposition parameters adopted. (author)

  9. Temperature-dependent surface structure, composition, and electronic properties of the clean SrTiO3(111) crystal face: Low-energy-electron diffraction, Auger-electron spectroscopy, electron energy loss, and ultraviolet-photoelectron spectroscopy studies

    International Nuclear Information System (INIS)

    Lo, W.J.; Somorjai, G.A.

    1978-01-01

    Low-energy-electron diffraction, Auger-electron spectroscopy, electron-energy-loss, and ultraviolet-photoelectron spectroscopies were used to study the structure, composition, and electron energy distribution of a clean single-crystal (111) face of strontium titanate (perovskite). The dependence of the surface chemical composition on the temperature has been observed along with corresponding changes in the surface electronic properties. High-temperature Ar-ion bombardment causes an irreversible change in the surface structure, stoichiometry, and electron energy distribution. In contrast to the TiO 2 surface, there are always significant concentrations of Ti 3+ in an annealed ordered SrTiO 3 (111) surface. This stable active Ti 3+ monolayer on top of a substrate with large surface dipole potential makes SrTiO 3 superior to TiO 2 when used as a photoanode in the photoelectrochemical cell

  10. Sorption of U(VI) in surfaces of SrTiO3

    International Nuclear Information System (INIS)

    Ortiz O, H.B.; Ordonez R, E.; Fernandez V, S.M.

    2004-01-01

    In this work is presented the physico chemical characterization and evaluation of those surface properties and of sorption of U on the SrTiO 3 like possible candidate for contention barrier in the deep geological confinement. The made studies showed that the SrTiO 3 presents maximum levels of sorption of positive nature species (mainly UO 2 2+ and UO 2 NO 3 + ). (Author)

  11. Resistance change effect in SrTiO3/Si (001) isotype heterojunction

    Science.gov (United States)

    Huang, Xiushi; Gao, Zhaomeng; Li, Pei; Wang, Longfei; Liu, Xiansheng; Zhang, Weifeng; Guo, Haizhong

    2018-02-01

    Resistance switching has been observed in double and multi-layer structures of ferroelectric films. The higher switching ratio opens up a vast path for emerging ferroelectric semiconductor devices. An n-n+ isotype heterojunction has been fabricated by depositing an oxide SrTiO3 layer on a conventional n-type Si (001) substrate (SrTiO3/Si) by pulsed laser disposition. Rectification and resistive switching behaviors in the n-n+ SrTiO3/Si heterojunction were observed by a conductive atomic force microscopy, and the n-n+ SrTiO3/Si heterojunction exhibits excellent endurance and retention characteristics. The possible mechanism was proposed based on the band structure of the n-n+ SrTiO3/Si heterojunction, and the observed electrical behaviors could be attributed to the modulation effect of the electric field reversal on the width of accumulation and the depletion region, as well as the height of potential of the n-n+ junction formed at the STO/Si interface. Moreover, oxygen vacancies are also indicated to play a crucial role in causing insulator to semiconductor transition. These results open the way to potential application in future microelectronic devices based on perovskite oxide layers on conventional semiconductors.

  12. Nonvolatile resistive switching in Pt/laALO3/srTiO3 heterostructures

    KAUST Repository

    Wu, S.

    2013-12-12

    Resistive switching heterojunctions, which are promising for nonvolatile memory applications, usually share a capacitorlike metal-oxide-metal configuration. Here, we report on the nonvolatile resistive switching in Pt/LaAlO3/SrTiO3 heterostructures, where the conducting layer near the LaAlO3/SrTiO3 interface serves as the "unconventional"bottom electrode although both oxides are band insulators. Interestingly, the switching between low-resistance and high-resistance states is accompanied by reversible transitions between tunneling and Ohmic characteristics in the current transport perpendicular to the planes of the heterojunctions. We propose that the observed resistive switching is likely caused by the electric-field-induced drift of charged oxygen vacancies across the LaAlO3/SrTiO3 interface and the creation of defect-induced gap states within the ultrathin LaAlO3 layer. These metal-oxide-oxide heterojunctions with atomically smooth interfaces and defect-controlled transport provide a platform for the development of nonvolatile oxide nanoelectronics that integrate logic and memory devices.

  13. Epitaxial growth of SrTiO3 thin film on Si by laser molecular beam epitaxy

    International Nuclear Information System (INIS)

    Zhou, X. Y.; Miao, J.; Dai, J. Y.; Chan, H. L. W.; Choy, C. L.; Wang, Y.; Li, Q.

    2007-01-01

    SrTiO 3 thin films have been deposited on Si (001) wafers by laser molecular beam epitaxy using an ultrathin Sr layer as the template. X-ray diffraction measurements indicated that SrTiO 3 was well crystallized and epitaxially aligned with Si. Cross-sectional observations in a transmission electron microscope revealed that the SrTiO 3 /Si interface was sharp, smooth, and fully crystallized. The thickness of the Sr template was found to be a critical factor that influenced the quality of SrTiO 3 and the interfacial structure. Electrical measurements revealed that the SrTiO 3 film was highly resistive

  14. Contributions of conduction band offset to the enhanced separation efficiency of photoinduced charges for SrTiO3/Bi2O3 heterojunction semiconductor

    International Nuclear Information System (INIS)

    Zhang, Zhenlong; Zhu, Jichun; Li, Shengjun; Mao, Yanli

    2014-01-01

    SrTiO 3 /Bi 2 O 3 heterojunction semiconductor was prepared and characterized by X-ray diffraction, UV–vis absorption spectrum, and scanning electron microscope, surface photovoltage spectroscopy, and photoluminescence spectroscopy. The surface photovoltage spectra indicate that the separation efficiency of photoinduced charges for SrTiO 3 /Bi 2 O 3 was enhanced compared with that of SrTiO 3 or Bi 2 O 3 . The energy band diagram of SrTiO 3 /Bi 2 O 3 heterojunction was directly determined with X-ray photoelectron spectroscopy, and the conduction band offset between SrTiO 3 and Bi 2 O 3 was quantified to be 0.28±0.03 eV. The photoluminescence spectra display that the recombination rate of photoinduced carriers for SrTiO 3 /Bi 2 O 3 decreases compared with that of SrTiO 3 or Bi 2 O 3 , which is mainly due to the energy levels matching between them. Therefore the enhanced separation efficiency of photoinduced charges is resulting from the energy difference between the conduction band edges of SrTiO 3 and Bi 2 O 3 . -- Graphical abstract: Enhanced separation efficiency for SrTiO 3 /Bi 2 O 3 is resulting from the energy difference between the conduction band edges. Highlights: ●Heterojunction semiconductor of SrTiO 3 /Bi 2 O 3 was prepared. ●SrTiO 3 /Bi 2 O 3 presents enhanced separation efficiency. ●Conduction band offset between SrTiO 3 and Bi 2 O 3 is quantified. ●Recombination rate of SrTiO 3 /Bi 2 O 3 decreases compared with single phases

  15. Chemical changes in titanate surfaces induced by Ar+ ion bombardment

    International Nuclear Information System (INIS)

    Gonzalez-Elipe, A.R.; Fernandez, A.; Espinos, J.P.; Munuera, G.; Sanz, J.M.

    1992-01-01

    The reduction effects and compositional changes induced by 3.5 keV Ar + bombardment of several titanates (i.e. SrTiO 3 , Al 2 TiO 5 and NiTiO 3 ) have been quantitatively investigated by XPS. In all the samples studied here the original Ti 4+ species were reduced to lower oxidation states (i.e. Ti 3+ and Ti 2+ ), although to a lesser extent than in pure TiO 2 . On the contrary, whereas Sr 2+ and Al 3+ seem to remain unaffected by Ar + bombardment, in agreement with the behaviour of the respective oxides (i.e. SrO and Al 2 O 3 ), Ni 2+ appears more easily reducible to Ni o in NiTiO 3 than in NiO. In addition, other specific differences were observed between the titanates, which reveal the existence of interesting chemical effects related to the presence of the different counter-ions in the titanates. In the case of Al 2 TiO 5 , its Ar + -induced decomposition to form TiO 2 + Al 2 O 3 could be followed by XPS. (Author)

  16. Influence of crystal phases on electro-optic properties of epitaxially grown lanthanum-modified lead zirconate titanate films

    Science.gov (United States)

    Masuda, Shin; Seki, Atsushi; Masuda, Yoichiro

    2010-02-01

    We describe here how we have improved the crystal qualities and controlled the crystal phase of the lanthanum-modified lead zirconate titanate (PLZT) film without changing the composition ratio using an oxygen-pressure crystallization process. A PLZT film deposited on a SrTiO3 substrate with the largest electro-optic (EO) coefficient of 498 pm/V has been achieved by controlling the crystal phase of the film. Additionally, a fatigue-free lead zirconate titanate (PZT) capacitor with platinum electrodes has been realized by reducing the oxygen vacancies in the films.

  17. Electric field effects in graphene/LaAlO3/SrTiO3 heterostructures and nanostructures

    Directory of Open Access Journals (Sweden)

    Mengchen Huang

    2015-06-01

    Full Text Available We report the development and characterization of graphene/LaAlO3/SrTiO3 heterostructures. Complex-oxide heterostructures are created by pulsed laser deposition and are integrated with graphene using both mechanical exfoliation and transfer from chemical-vapor deposition on ultraflat copper substrates. Nanoscale control of the metal-insulator transition at the LaAlO3/SrTiO3 interface, achieved using conductive atomic force microscope lithography, is demonstrated to be possible through the graphene layer. LaAlO3/SrTiO3-based electric field effects using a graphene top gate are also demonstrated. The ability to create functional field-effect devices provides the potential of graphene-complex-oxide heterostructures for scientific and technological advancement.

  18. Stability and electronic structure studies of LaAlO3/SrTiO3 (110) heterostructures

    International Nuclear Information System (INIS)

    Du Yan-Ling; Wang Chun-Lei; Li Ji-Chao; Xu Pan-Pan; Zhang Xin-Hua; Liu Jian; Su Wen-Bin; Mei Liang-Mo

    2014-01-01

    The first-principles calculations are employed to investigate the stability, magnetic, and electrical properties of the oxide heterostructure of LaAlO 3 /SrTiO 3 (110). By comparing their interface energies, it is obtained that the buckled interface is more stable than the abrupt interface. This result is consistent with experimental observation. At the interface of LaAlO 3 /SrTiO 3 (110) heterostructure, the Ti—O octahedron distortions cause the Ti t 2g orbitals to split into the two-fold degenerate d xz /d yz and nondegenerate d xy orbitals. The former has higher energy than the latter. The partly filled two-fold degenerate t 2g orbitals are the origin of two-dimensional electron gas, which is confined at the interface. Lattice mismatch between LaAlO 3 and SrTiO 3 leads to ferroelectric-like lattice distortions at the interface, and this is the origin of spin-splitting of Ti 3d electrons. Hence the magnetism appears at the interface of LaAlO 3 /SrTiO 3 (110). (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  19. Conductivity and structure of sub-micrometric SrTiO3-YSZ composites

    DEFF Research Database (Denmark)

    Ruiz Trejo, Enrique; Thydén, Karl Tor Sune; Bonanos, Nikolaos

    2016-01-01

    Sub-micrometric composites of SrTiO3-YSZ (1:1 volume) and samples of SrTiO3 were prepared by high temperature consolidation of precursors obtained by precipitation with NaOH. The structure development and morphology of the precursors were studied by XRD and SEM. The perovskite and fluorite phases...... in the composites are clearly formed at 600°C with no signs of reaction up to 1100°C; the nominally pure SrTiO3 can be formed at temperatures as low as 400°C. Composites with sub-micrometric grain sizes can be prepared successfully without reaction between the components, although a change in the cell parameter...... of the SrTiO3 is attributed to the presence of Na. The consolidated composites were studied by impedance spectroscopy between 200 and 400°C and at a fixed temperature of 600°C with a scan in the partial pressure of oxygen. The composites did not exhibit high levels of ionic conductivity in the grain...

  20. Physics of SrTiO3-based heterostructures and nanostructures: a review.

    Science.gov (United States)

    Pai, Yun-Yi; Tylan-Tyler, Anthony; Irvin, Patrick; Levy, Jeremy

    2018-02-09

    This review provides a summary of the rich physics expressed within SrTiO 3 -based heterostructures and nanostructures. The intended audience is researchers who are working in the field of oxides, but also those with different backgrounds (e.g., semiconductor nanostructures). After reviewing the relevant properties of SrTiO 3 itself, we will then discuss the basics of SrTiO 3 -based heterostructures, how they can be grown, and how devices are typically fabricated. Next, we will cover the physics of these heterostructures, including their phase diagram and coupling between the various degrees of freedom. Finally, we will review the rich landscape of quantum transport phenomena, as well as the devices that elicit them.

  1. Physics of SrTiO3-based heterostructures and nanostructures: a review

    Science.gov (United States)

    Pai, Yun-Yi; Tylan-Tyler, Anthony; Irvin, Patrick; Levy, Jeremy

    2018-03-01

    This review provides a summary of the rich physics expressed within SrTiO3-based heterostructures and nanostructures. The intended audience is researchers who are working in the field of oxides, but also those with different backgrounds (e.g., semiconductor nanostructures). After reviewing the relevant properties of SrTiO3 itself, we will then discuss the basics of SrTiO3-based heterostructures, how they can be grown, and how devices are typically fabricated. Next, we will cover the physics of these heterostructures, including their phase diagram and coupling between the various degrees of freedom. Finally, we will review the rich landscape of quantum transport phenomena, as well as the devices that elicit them.

  2. Efficient degradation of Methylene Blue dye over highly reactive Cu doped strontium titanate (SrTiO3) nanoparticles photocatalyst under visible light.

    Science.gov (United States)

    Rahman, Qazi Inamur; Ahmad, Musheer; Misra, Sunil Kumar; Lohani, Minaxi

    2012-09-01

    Visible light induced photocatalysts of Cu doped SrTiO3 (Cu/SrTiO3) nanoparticles with the size -60-75 nm were prepared via facile sol-gel method. The morphological, optical, crystalline properties and compositions of synthesized Cu/SrTiO3 nanoparticles were thoroughly characterized by field emission scanning electron microscopy (FE-SEM), powder X-ray diffraction (XRD), ultra violet-visible spectroscopy (UV-Vis) and energy dispersive X-ray (EDX). A significant red shift in the UV-diffused reflectance spectrum was observed and the absorption edge shifted to visible region by the Cu doping. Surprisingly, the band gap of SrTiO3 was changed from 3.2 eV drop to 2.96 eV. The photocatalytic activity of the synthesized Cu/SrTiO3 nanoparticles was demonstrated for the degradation of Methylene Blue dye under visible light irradiation. The formation of new acceptor region in Cu/SrTiO3 was responsible for high photocatalytic activity of Cu/SrTiO3 nanoparticles. The results showed that the Methylene Blue dye was degraded by -66% within time span of 2 h over the Cu/SrTiO3 nanoparticles. This dye degradation reaction followed the Langmuir-Hinshelwood kinetics and also exhibited first order reaction rate. The calculated rate constant for the degradation reaction following first order kinetics was k = 0.0016 min(-1).

  3. Magnetic two-dimensional electron gas at the manganite-buffered LaAlO3/SrTiO3 interface

    DEFF Research Database (Denmark)

    R. Zhang, H.; Zhang, Y.; Zhang, H.

    2017-01-01

    Fabrication of highly mobile spin-polarized two-dimensional electron gas (2DEG) is crucially important for both fundamental and applied research. Usually, spin polarization appears below 10 K for the 2DEG of LaAlO3/SrTiO3 interface, stemming from the magnetic ordering of Ti3+ ions with the mediat......Fabrication of highly mobile spin-polarized two-dimensional electron gas (2DEG) is crucially important for both fundamental and applied research. Usually, spin polarization appears below 10 K for the 2DEG of LaAlO3/SrTiO3 interface, stemming from the magnetic ordering of Ti3+ ions...... with the mediation of itinerant electrons. Herein, we report a magnetic 2DEG at a La7/8Sr1/8MnO3-buffered LaAlO3/SrTiO3 interface, which simultaneously shows electrically tunable anomalous Hall effect and high conductivity. The spin-polarized temperature for the 2DEG is promoted to 30 K while the mobility remains...... high. The magnetism likely results from a gradient manganese interdiffusion into SrTiO3. The present work demonstrates the great potential of manganite-buffered LaAlO3/SrTiO3 interfaces for spintronic applications....

  4. Fabrication of Schottky Junction Between Au and SrTiO3

    Science.gov (United States)

    Inoue, Akira; Izumisawa, Kei; Uwe, Hiromoto

    2001-05-01

    A Schottky junction with a high rectification ratio between Au and La-doped SrTiO3 has been fabricated using a simple surface treatment. Highly La-doped (5%) SrTiO3 single crystals are annealed in O2 atmosphere at about 1000°C for 1 h and etched in HNO3 for more than five min. The HNO3 etching is performed in a globe box containing N2 to prevent pollution from the air. After the treatment, Au is deposited on the SrTiO3 surface in a vacuum (˜ 10-7 Torr) with an e-gun evaporator. The current voltage characteristics of the junction have shown excellent rectification properties, although junctions using neither annealed nor etched SrTiO3 exhibit high leak current in reverse voltage. The rectification ratio of the junction at 1 V is more than six orders of magnitude and there is no hysteresis in the current voltage spectra. The logarithm of the current is linear with the forward bias voltage. The ideal factor of the junction is estimated to be about 1.68. These results suggest that, if prevented from being pollution by the air, a good Schottky junction can be obtained by easy processes such as annealing in oxygen atmosphere and surface etching with acid.

  5. Processing of Al2O3/SrTiO3/PDMS Composites With Low Dielectric Loss

    Science.gov (United States)

    Yao, J. L.; Guo, M. J.; Qi, Y. B.; Zhu, H. X.; Yi, R. Y.; Gao, L.

    2018-05-01

    Polydimethylsiloxane (PDMS) is widely used in the electrical and electronic industries due to its excellent electrical insulation and biocompatible characteristics. However, the dielectric constant of pure PDMS is very low which restricts its applications. Herein, we report a series of PDMS/Al2O3/strontium titanate (ST) composites with high dielectric constant and low loss prepared by a simple experimental method. The composites exhibit high dielectric constant (relative dielectric constant is 4) after the composites are coated with insulated Al2O3 particles, and the dielectric constant gets further improved for composites with ST particles (dielectric constant reaches 15.5); a lower dielectric loss (tanδ= 0.05) is also found at the same time which makes co-filler composites suitable for electrical insulation products, and makes the experimental method more interesting in modern teaching.

  6. Nonvolatile Resistive Switching in Pt/LaAlO_{3}/SrTiO_{3} Heterostructures

    Directory of Open Access Journals (Sweden)

    Shuxiang Wu

    2013-12-01

    Full Text Available Resistive switching heterojunctions, which are promising for nonvolatile memory applications, usually share a capacitorlike metal-oxide-metal configuration. Here, we report on the nonvolatile resistive switching in Pt/LaAlO_{3}/SrTiO_{3} heterostructures, where the conducting layer near the LaAlO_{3}/SrTiO_{3} interface serves as the “unconventional” bottom electrode although both oxides are band insulators. Interestingly, the switching between low-resistance and high-resistance states is accompanied by reversible transitions between tunneling and Ohmic characteristics in the current transport perpendicular to the planes of the heterojunctions. We propose that the observed resistive switching is likely caused by the electric-field-induced drift of charged oxygen vacancies across the LaAlO_{3}/SrTiO_{3} interface and the creation of defect-induced gap states within the ultrathin LaAlO_{3} layer. These metal-oxide-oxide heterojunctions with atomically smooth interfaces and defect-controlled transport provide a platform for the development of nonvolatile oxide nanoelectronics that integrate logic and memory devices.

  7. Metallic and Insulating Interfaces of Amorphous SrTiO3-Based Oxide Heterostructures

    DEFF Research Database (Denmark)

    Chen, Yunzhong; Pryds, Nini; Kleibeuker, Josée E.

    2011-01-01

    AlO3, SrTiO3, and yttria-stabilized zirconia films. On the other hand, samples of amorphous La7/8Sr1/8MnO3 films on SrTiO3 substrates remain insulating. The interfacial conductivity results from the formation of oxygen vacancies near the interface, suggesting that the redox reactions on the surface...

  8. Synthesis of Ag-loaded SrTiO_3/TiO_2 heterostructure nanotube arrays for enhanced photocatalytic performances

    International Nuclear Information System (INIS)

    Hu, Zijun; Chen, Da; Zhan, Xiaqiang; Wang, Fang; Qin, Laishun; Huang, Yuexiang

    2017-01-01

    In this work, the effect of loading Ag nanoparticles on the photocatalytic activity of SrTiO_3/TiO_2 nanotube arrays (TNTAs) was investigated. TNTAs were partially transformed to SrTiO_3 through a hydrothermal treatment, which could preserve the tubular structure of TNTAs, and then, Ag nanoparticles were well deposited on the surface of SrTiO_3/TNTAs heterostructure by a chemical reduction process. Compared to the TNTAs sample, the Ag-loaded SrTiO_3/TNTAs sample showed significantly enhanced photocatalytic activities for photodegradation of rhodamine B. The enhanced photocatalytic activity of Ag-loaded SrTiO_3/TNTAs could be attributed to the increased optical absorption as well as the efficient charge transfer and separation of photogenerated electron-hole pairs induced by the SrTiO_3/TNTAs heterojunction and the Schottky barrier between metallic Ag and SrTiO_3/TNTAs. On the basis of the trapping experiments, the possible photocatalytic mechanism was also discussed. (orig.)

  9. EPR of photochromic Mo3+ in SrTiO3

    NARCIS (Netherlands)

    Kool, Th.W.

    2010-01-01

    In single crystals of SrTiO_3, a paramagnetic center, characterized by S = 3/2 and hyperfine interaction with an I = 5/2 nuclear spin has been observed in the temperature range 4.2K-77K by means of EPR. The impurity center is attributed to Mo3+. No additional line splitting in the EPR spectrum due

  10. Direct Observation of Room-Temperature Stable Magnetism in LaAlO3/SrTiO3 Heterostructures.

    Science.gov (United States)

    Yang, Ming; Ariando; Zhou, Jun; Asmara, Teguh Citra; Krüger, Peter; Yu, Xiao Jiang; Wang, Xiao; Sanchez-Hanke, Cecilia; Feng, Yuan Ping; Venkatesan, T; Rusydi, Andrivo

    2018-03-21

    Along with an unexpected conducting interface between nonmagnetic insulating perovskites LaAlO 3 and SrTiO 3 (LaAlO 3 /SrTiO 3 ), striking interfacial magnetisms have been observed in LaAlO 3 /SrTiO 3 heterostructures. Interestingly, the strength of the interfacial magnetic moment is found to be dependent on oxygen partial pressures during the growth process. This raises an important, fundamental question on the origin of these remarkable interfacial magnetic orderings. Here, we report a direct evidence of room-temperature stable magnetism in a LaAlO 3 /SrTiO 3 heterostructure prepared at high oxygen partial pressure by using element-specific soft X-ray magnetic circular dichroism at both Ti L 3,2 and O K edges. By combining X-ray absorption spectroscopy at both Ti L 3,2 and O K edges and first-principles calculations, we qualitatively ascribe that this strong magnetic ordering with dominant interfacial Ti 3+ character is due to the coexistence of LaAlO 3 surface oxygen vacancies and interfacial (Ti Al -Al Ti ) antisite defects. On the basis of this new understanding, we revisit the origin of the weak magnetism in LaAlO 3 /SrTiO 3 heterostructures prepared at low oxygen partial pressures. Our calculations show that LaAlO 3 surface oxygen vacancies are responsible for the weak magnetism at the interface. Our result provides direct evidence on the presence of room-temperature stable magnetism and a novel perspective to understand magnetic and electronic reconstructions at such strategic oxide interfaces.

  11. 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.

  12. Vacancy induced metallicity at the CaHfO3/SrTiO3 interface

    KAUST Repository

    Nazir, Safdar; Pulikkotil, J. J.; Schwingenschlö gl, Udo; Singh, Nirpendra

    2011-01-01

    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.

  13. Physics of SrTiO3-based heterostructures and nanostructures: a review.

    Science.gov (United States)

    Pai, Yun-Yi; Tylan-Tyler, Anthony; Irvin, Patrick; Levy, Jeremy

    2017-08-30

    1 Overview 1 1.1 Introduction 1 1.1.1 Oxide growth techniques are rooted in search for high-Tc superconductors 2 1.1.2 First reports of interface conductivity 2 1.2 2D physics 2 1.3 Emergent properties of oxide heterostructures and nanostructures 3 1.4 Outline 3 2 Relevant properties of SrTiO3 3 2.1 Structural properties and transitions 3 2.2 Ferroelectricity, Paraelectricity and Quantum Paraelectricity 4 2.3 Electronic structure 5 2.4 Defects 6 2.4.1 Oxygen vacancies 6 2.4.2 Terraces 7 2.5 Superconductivity 7 3 SrTiO3-based heterostructures and nanostructures 8 3.1 Varieties of heterostructures 8 3.1.1 SrTiO3 only 9 3.1.2 LaAlO3/SrTiO3 9 3.1.3 Other heterostructures formed with SrTiO3 10 3.2 Thin-film growth 10 3.2.1 Substrates 10 3.2.2 SrTiO3 surface treatment 11 3.2.3 Pulsed Laser Deposition 11 3.2.4 Atomic Layer Deposition 13 3.2.5 Molecular Beam Epitaxy 14 3.2.6 Sputtering 15 3.3 Device Fabrication 15 3.3.1 "Conventional" photolithography - Thickness Modulation, hard masks, etc. 15 3.3.2 Ion beam irradiation 16 3.3.3 Conductive-AFM lithography 16 4 Properties and phase diagram of LaAlO3/SrTiO3 16 4.1 Insulating state 16 4.2 Conducting state 17 4.2.1 Confinement thickness (the depth profile of the 2DEG) 17 4.3 Metal-insulator transition and critical thickness 18 4.3.1 Polar catastrophe ( electronic reconstruction) 18 4.3.2 Oxygen Vacancies 19 4.3.3 Interdiffusion 20 4.3.4 Polar Interdiffusion + oxygen vacancies + antisite pairs 20 4.3.5 Role of surface adsorbates 21 4.3.6 Hidden FE like distortion - Strain induced instability 21 4.4 Structural properties and transitions 21 4.5 Electronic band structure 22 4.5.1 Theory 22 4.5.2 Experiment 23 4.5.3 Lifshitz transition 24 4.6 Defects, doping, and compensation 25 4.7 Magnetism 25 4.7.1 Experimental evidence 25 4.7.2 Two types of magnetism 27 4.7.3 Ferromagnetism 27 4.7.4 Metamagnetism 28 4.8 Superconductivity 28 4.9 Optical properties 29 4.9.1 Photoluminesce

  14. Epitaxial growth of SrTiO3/YBa2Cu3O7 - x heterostructures by plasma-enhanced metalorganic chemical vapor deposition

    Science.gov (United States)

    Liang, S.; Chern, C. S.; Shi, Z. Q.; Lu, P.; Safari, A.; Lu, Y.; Kear, B. H.; Hou, S. Y.

    1994-06-01

    We report heteroepitaxial growth of SrTiO3 on YBa2Cu3O7-x/LaAlO3 substrates by plasma-enhanced metalorganic chemical vapor deposition. X-ray diffraction results indicated that SrTiO3 films were epitaxially grown on a (001) YBa2Cu3O7-x surface with [100] orientation perpendicular to the surface. The film composition, with Sr/Ti molar ratio in the range of 0.9 to 1.1, was determined by Rutherford backscattering spectrometry and energy dispersive spectroscopy. The thickness of the SrTiO3 films is 0.1-0.2 μm. The epitaxial growth was further evidenced by high-resolution transmission electron microscopy and selected area diffraction. Atomically abrupt SrTiO3/YBa2Cu3O7-x interface and epitaxial growth with [100]SrTiO3∥[001]YBa2Cu3O7-x were observed in this study. The superconducting transition temperature of the bottom YBa2Cu3O7-x layer, as measured by ac susceptometer, did not significantly degrade after the growth of overlayer SrTiO3. The capacitance-voltage measurements showed that the dielectric constant of the SrTiO3 films was as high as 315 at a signal frequency of 100 KHz. The leakage current density through the SrTiO3 films is about 1×10-6 A/cm2 at 2-V operation. Data analysis on the current-voltage characteristic indicated that the conduction process is related to bulk-limited Poole-Frenkel emission.

  15. Temperature-dependent optical absorption of SrTiO3

    International Nuclear Information System (INIS)

    Kok, Dirk J.; Irmscher, Klaus; Naumann, Martin; Guguschev, Christo; Galazka, Zbigniew; Uecker, Reinhard

    2015-01-01

    The optical absorption edge and near infrared absorption of SrTiO 3 were measured at temperatures from 4 to 1703 K. The absorption edge decreases from 3.25 eV at 4 K to 1.8 eV at 1703 K and is extrapolated to approximately 1.2 eV at the melting point (2350 K). The transmission in the near IR decreases rapidly above 1400 K because of free carrier absorption and is about 50% of the room temperature value at 1673 K. The free carriers are generated by thermal excitation of electrons over the band gap and the formation of charged vacancies. The observed temperature-dependent infrared absorption can be well reproduced by a calculation based on simple models for the intrinsic free carrier concentration and the free carrier absorption coefficient. The measured red shift of the optical absorption edge and the rising free carrier absorption strongly narrow the spectral range of transmission and impede radiative heat transport through the crystal. These effects have to be considered in high temperature applications of SrTiO 3 -based devices, as the number of free carriers rises considerably, and in bulk crystal growth to avoid growth instabilities. Temperature dependent optical absorption edge of SrTiO 3 , measured, fitted, and extrapolated to the melting point. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  16. Photo(electro)chemical oxidation of water by the persulfate ion over aqueous suspensions of strontium titanate SrTiO3 containing lanthanum chromite LaCrO3

    NARCIS (Netherlands)

    Thewissen, D.H.M.W.; Timmer, K.; Eeuwhorst‐Reinten, M.; Tinnemans, A.H.A.; Mackor, A.

    1982-01-01

    The photodecomposition of the S2O2‐ 8 ion to the SO2‐ 4 ion with concomitant oxidation of water to molecular oxygen over n‐type SrTiO3 powders mixed with LaCrO3 (mole fraction x = 0–1), using UV light (λ > 300 nm), is considerably faster than the photochemical (UV) decomposition of S2O2‐ 8 in water

  17. Adsorption of hazardous cationic dye onto the combustion derived SrTiO3 nanoparticles: Kinetic and isotherm studies

    Directory of Open Access Journals (Sweden)

    N.P. Bhagya

    2016-03-01

    Full Text Available In this article we report on solution combustion method to synthesize SrTiO3 nanoparticles (ST-NPs and the removal of malachite green (MG azo dye from the aqueous solution. The synthesized ST-NPs were calcined at 600 °C for 2 h. Powder X-ray diffraction (PXRD, field emission scanning electron microscopy (FE-SEM, transmission electron microscopy (TEM, Fourier transform infrared spectroscopy (FT-IR, and Brunauer–Emmett–Teller (BET were used to characterize the product. Adsorption experiments were performed with cationic malachite green (MG dye. ∼98% dye was adsorbed onto the ST-NPs at pH 10 for 30 min of the contact time. The optimum adsorbent dose was found to be 0.015 g/L of the dye. To study the adsorption kinetics Langmuir Hinshelwood model was used and the first order kinetic best describes the MG adsorption onto the ST-NPs. The adsorption isotherms data of MG onto ST-NPs obtained were analyzed by Langmuir and Freundlich isotherm models and the results describe the best representation of the Langmuir isotherm model.

  18. Ferroelectricity of strained SrTiO3 in lithium tetraborate glass-nanocomposite and glass-ceramic

    Science.gov (United States)

    Abdel-Khalek, E. K.; Mohamed, E. A.; Kashif, I.

    2018-02-01

    Glass-nanocomposite (GNCs) sample of the composition [90Li2B4O7-10SrTiO3] (mol %) was prepared by conventional melt quenching technique. The glassy phase and the amorphous nature of the GNCs sample were identified by Differential thermal analysis (DTA) and X-ray diffraction (XRD) studies, respectively. DTA of the GNCs exhibits sharp and broad exothermic peaks which represent the crystallization of Li2B4O7 and SrTiO3, respectively. The tetragonal Li2B4O7 and tetragonal SrTiO3 crystalline phases in glass-ceramic (GC) were identified by XRD and scanning electron microscopic (SEM). The strain tetragonal SrTiO3 phase in GNCs and GC has been confirmed by SEM. The values of crystallization activation energies (Ec1 and Ec2) for the first and second exothermic peaks are equal to 174 and 1452 kJ/mol, respectively. The Ti3+ ions in tetragonal distorted octahedral sites in GNCs were identified by optical transmission spectrum. GNCs and GC samples exhibit broad dielectric anomalies at 303 and 319 K because of strained SrTiO3 ferroelectric, respectively.

  19. Interface properties of SrTiO3-based heterostructures studied by spectroscopy and high-resolution microscopy

    International Nuclear Information System (INIS)

    Pfaff, Florian Georg

    2017-01-01

    Oxide heterostructures can exhibit a variety of unexpected electronic and magnetic phenomena at their interfaces. A prominent example is the interface in LaAlO 3 /SrTiO 3 heterostructures where a two-dimensional electron system (2DES) forms if the LaAlO 3 thickness equals or exceeds a critical thickness of four unit cells. Similar to LaAlO 3 /SrTiO 3 an interface 2DES above a critical overlayer thickness has been observed in γ-Al 2 O 3 /SrTiO 3 . However, the electron mobility as well as the sheet carrier density exceed those of LaAlO 3 /SrTiO 3 heterostructures by more than one order of magnitude. This thesis is concerned with the growth and the characterization of these two types of interface systems with the main focus on the analysis of the physical properties at the interface and the understanding of their leading mechanisms. In regard to the sample fabrication it is demonstrated in the present thesis that the hitherto established growth routine of LaAlO 3 /SrTiO 3 by pulsed laser deposition has to be altered and optimized for the growth of γ-Al 2 O 3 . It is shown that growth monitoring by analyzing reflection high energy electron diffraction (RHEED) intensity oscillations is hindered by the formation of surface wave resonances. In order to avoid this effect, a modified growth geometry has to be used whereby also in this heterostructure systems monitoring of the layer-by-layer growth of γ-Al 2 O 3 /SrTiO 3 heterostructures by electron diffraction can be achieved. A so-called electronic reconstruction is discussed as the possible driving mechanism for the 2DES formation in LaAlO 3 /SrTiO 3 . In this scenario, the built-up potential within the polar LaAlO 3 overlayer is compensated by a charge transfer from the sample surface to the top most layers of the non-polar SrTiO 3 substrate. Furthermore, the properties of these heterostructures strongly depend on the used growth conditions. In the present work, for instance, a significant increase in the charge

  20. Sintering and Electrical Characterization of La and Nb Co‐doped SrTiO3 Electrode Materials for Solid Oxide Cell Applications

    DEFF Research Database (Denmark)

    Sudireddy, Bhaskar Reddy; Agersted, Karsten

    2014-01-01

    Single‐phase lanthanum and niobium co‐doped strontium titanate (Sr1–3x/2LaxTi0.9Nb0.1O3; x = 0–0.02) ceramics were prepared. Dilatometry in reducing atmosphere showed an increase in the sintering rate and sintered density with an increase in La amount. Microscopy of fractured surfaces of sintered...... samples showed that the average grain size increased drastically in reducing conditions with increasing La content (and associated A‐site vacancies). By incorporating 2 mol.% La, the electronic conductivity significantly improved from 80 to 135 S cm−1 at 1,000 °C, and even larger improvements were...... observed at lower temperatures. These observations demonstrate the flexibility in tailoring the microstructure and electronic transport properties by doping small amounts of La into the Nb‐doped SrTiO3 and show that Sr1–3x/2LaxTi0.9Nb0.1O3 is a potential electrode material for solid oxide cells....

  1. Nonvolatile resistive switching in Pt/laALO3/srTiO3 heterostructures

    KAUST Repository

    Wu, S.; Luo, X.; Turner, S.; Peng, H.; Lin, W.; Ding, J.; David, A.; Wang, B.; Van, Tendeloo, G.; Wang, J.; Wu, Tao

    2013-01-01

    Resistive switching heterojunctions, which are promising for nonvolatile memory applications, usually share a capacitorlike metal-oxide-metal configuration. Here, we report on the nonvolatile resistive switching in Pt/LaAlO3/SrTiO3 heterostructures

  2. Microstructure of Homoepitaxial SrTiO3 Films Deposited by Laser Ablation

    International Nuclear Information System (INIS)

    Tse, Y Y; Jackson, T J; Koutsonas, Y; Passerieux, G; Jones, I P

    2006-01-01

    Homoepitaxial strontium titanate thin films have been grown by pulsed laser deposition on (001) SrTiO 3 (STO) substrates with pulse rates ranging from 0.15 Hz to 100 Hz. The microstructure of the as-deposited films has been characterised by cross-sectional transmission electron microscopy. It is found that the growth mode and microstructure of the films are strongly influenced by the intervals between the laser pulses. Films have homogeneous microstructure under a critical thickness, above which the film breaks into toothlike columns. The growth is unstable against the formation of low angle boundaries which result in the formation of grains elongated in the direction of film growth. These become toothlike structures and the size of the tooth depends on the pulse rate and the growth time. The diffusion of point defects in films grown over a long time can lead instead to the development of elongated vacancy clusters directed normal to the film-vacuum interface. All films grow with a high density of point defects which may be related to deviation from the stoichiometry of the ceramic ablation target. Microanalysis suggests that there is strontium loss in the film, which causes defect formation inside the STO films

  3. Defect engineering of SrTiO3 thin films for resistive switching applications

    International Nuclear Information System (INIS)

    Wicklein, Sebastian

    2013-01-01

    As a matter of fact, the importance of (transition) metal oxides for modern applications in the field of energy and information technology (IT) for e.g. novel energy storage systems and solid state electronic devices is increasing. Previous studies discovered the importance of defects in an oxide for their functionality and emphasized the impact of stoichiometry on the oxide performance. A new field of interest of the memory technology sector is the so-called resistive switching phenomena where a voltage stimulus causes a thin oxide (≤10 nm) to change its resistance state from a high resistance state to a low resistance state and back. So called resistive RAM (ReRAM or RRAM) are deemed to be the future replacement (2015) for contemporary FLASH memory technology due to its extremely low energy consumption, its very fast read/write time (ns) and its possible node size 3 was used as an oxide model material and was deposited by pulsed laser deposition (PLD) onto doped and undoped SrTiO 3 single crystals to investigate the formation of defects as a function of the process parameters. By combining structural and chemical thin film analysis with detailed PLD plume diagnostics and modeling of the laser plume dynamics, it was possible to elucidate the different physical mechanisms determining the stoichiometry of SrTiO 3 during PLD. Deviations between thin film and target stoichiometry are basically a result of two effects, namely, incongruent ablation and preferential scattering of lighter ablated species during their motion towards the substrate in the O 2 background gas. It is shown that the SrTiO 3 system reacts to a non-stoichiometry with the systematic incorporation of titanium and strontium vacancies which could be detected by positron annihilation lifetime spectroscopy. The role of extrinsic dopands such as Fe is shown to have more complicated effects on the SrTiO 3 system than portrayed by theoretical considerations. The effect of defects on the resistive

  4. Mechanisms of charge transfer and redistribution in LaAlO3/SrTiO3 revealed by high-energy optical conductivity.

    Science.gov (United States)

    Asmara, T C; Annadi, A; Santoso, I; Gogoi, P K; Kotlov, A; Omer, H M; Motapothula, M; Breese, M B H; Rübhausen, M; Venkatesan, T; Ariando; Rusydi, A

    2014-04-14

    In condensed matter physics the quasi two-dimensional electron gas at the interface of two different insulators, polar LaAlO3 on nonpolar SrTiO3 (LaAlO3/SrTiO3) is a spectacular and surprising observation. This phenomenon is LaAlO3 film thickness dependent and may be explained by the polarization catastrophe model, in which a charge transfer of 0.5e(-) from the LaAlO3 film into the LaAlO3/SrTiO3 interface is expected. Here we show that in conducting samples (≥ 4 unit cells of LaAlO3) there is indeed a ~0.5e(-) transfer from LaAlO3 into the LaAlO3/SrTiO3 interface by studying the optical conductivity in a broad energy range (0.5-35 eV). Surprisingly, in insulating samples (≤ 3 unit cells of LaAlO3) a redistribution of charges within the polar LaAlO3 sublayers (from AlO2 to LaO) as large as ~0.5e(-) is observed, with no charge transfer into the interface. Hence, our results reveal the different mechanisms for the polarization catastrophe compensation in insulating and conducting LaAlO3/SrTiO3 interfaces.

  5. Epitaxial properties of ZnO thin films on SrTiO3 substrates grown by laser molecular beam epitaxy

    International Nuclear Information System (INIS)

    Wei, X. H.; Li, Y. R.; Zhu, J.; Huang, W.; Zhang, Y.; Luo, W. B.; Ji, H.

    2007-01-01

    Epitaxial ZnO thin films with different orientations have been grown by laser molecular beam epitaxy on (001)- (011)-, and (111)-orientated SrTiO 3 single-crystal substrates. The growth behavior was in situ monitored by reflection high-energy electron diffraction, and the epitaxial orientation relations were reconfirmed by ex situ x-ray diffraction measurements. In the case of ZnO on SrTiO 3 (001), four orthogonal domains coexisted in the ZnO epilayer, i.e., ZnO(110) parallel SrTiO 3 (001) and ZnO[-111] parallel SrTiO 3 . For (011)- and (111)-orientated substrates, single-domain epitaxy with c axial orientation was observed, in which the in-plane relationship was ZnO[110] parallel SrTiO 3 [110] irrespective of the substrate orientations. Additionally, the crystalline quality of ZnO on SrTiO 3 (111) was better than that of ZnO on SrTiO 3 (011) because of the same symmetry between the (111) substrates and (001) films. The obtained results can be attributed to the difference of the in-plane crystallographic symmetry. Furthermore, those alignments can be explained by the interface stress between the substrates and the films

  6. Two-dimensional thermoelectric Seebeck coefficient of SrTiO3-based superlattices

    International Nuclear Information System (INIS)

    Ohta, Hiromichi

    2008-01-01

    This review provides the origin of the unusually large thermoelectric Seebeck coefficient vertical stroke S vertical stroke of a two-dimensional electron gas confined within a unit cell layer thickness (∝0.4 nm) of a SrTi 0.8 Nb 0.2 O 3 layer of artificial superlattices of SrTiO 3 /SrTi 0.8 Nb 0.2 O 3 [H. Ohta et al., Nature Mater. 6, 129 (2007)]. The vertical stroke S vertical stroke 2D values of the[(SrTiO 3 ) 17 /(SrTi 0.8 Nb 0.2 O 3 ) y ] 20 superlattice increase proportional to y -0.5 , and reach 290 μV K -1 (y=1) at room temperature, which is ∝5 times larger than that of the SrTi 0.8 Nb 0.2 O 3 bulk (vertical stroke S vertical stroke 3D =61 μVK -1 ), proving that the density of states in the ground state for SrTiO 3 increases in inverse proportion to y. The critical barrier thickness for quantum electron confinement is also clarified to be 6.25 nm (16 unit cells of SrTiO 3 ). Significant structural changes are not observed in the superlattice after annealing at 900 K in a vacuum. The value of vertical stroke S vertical stroke 2D of the superlattice gradually increases with temperature and reaches 450 μVK -1 at 900 K, which is ∝3 times larger than that of bulk SrTi 0.8 Nb 0.2 O 3 . These observations provide clear evidence that the [(SrTiO 3 ) 17 /(SrTi 0.8 Nb 0.2 O 3 ) 1 ] 20 superlattice is stable and exhibits a giant vertical stroke S vertical stroke even at high temperature. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  7. Charge transfer mechanism for the formation of metallic states at the KTaO3/SrTiO3 interface

    KAUST Repository

    Nazir, Safdar

    2011-03-29

    The electronic and optical properties of the KTaO3/SrTiO3 heterointerface are analyzed by the full-potential linearized augmented plane-wave approach of density functional theory. Optimization of the atomic positions points at subordinate changes in the crystal structure and chemical bonding near the interface, which is due to a minimal lattice mismatch. The creation of metallic interface states thus is not affected by structural relaxation but can be explained by charge transfer between transition metal and oxygen atoms. It is to be expected that a charge transfer is likewise important for related interfaces such as LaAlO3/SrTiO3. The KTaO3/SrTiO3 system is ideal for disentangling the complex behavior of metallic interface states, since almost no structural relaxation takes place.

  8. Promoting Photocatalytic Overall Water Splitting by Controlled Magnesium Incorporation in SrTiO3 Photocatalysts

    NARCIS (Netherlands)

    Han, Kai; Lin, Yen Chun; Yang, Chia Min; Jong, Ronald; Mul, Guido; Mei, Bastian

    2017-01-01

    SrTiO3 is a well-known photocatalyst inducing overall water splitting when exposed to UV irradiation of wavelengths <370 nm. However, the apparent quantum efficiency of SrTiO3 is typically low, even when functionalized with nanoparticles of Pt or Ni@NiO. Here, we introduce a simple solid-state

  9. Investigation of the electroforming and resistive switching mechanisms in Fe-doped SrTiO3 thin films

    International Nuclear Information System (INIS)

    Menke, Tobias

    2009-01-01

    To overcome the physical limits of todays memory technologies new concepts are needed. The resistive random access memory (RRAM), which bases on a nonvolatile and repeatable change of the resistance by external electrical stimuli, seems to be one promising candidate. Within the scope of this work, the model system Strontium titanate (SrTiO 3 ) has been investigated to get a deeper understanding of the underlying physical mechanism related to the resistance change. The electrical properties of SrTiO 3 (STO) can be modulated from a band insulator to metallic conduction by a self-doping with oxygen vacancies which act as shallow donors. A local accumulation or depletion of oxygen vacancies at the vicinity of the surface will lead to a local redox process which is responsible for the resistance change. To study the influence of the interfaces on the switching properties of SrTiO 3 thin films, epitaxial films of Fe-doped SrTiO 3 were grown on different bottom electrodes (SrRuO 3 , LaNiO 3 und Nb:STO) by a ''Pulsed Laser Deposition'' technique. An atomic force microscope equipped with a conductive tip (LC-AFM) allowed studying the conductivity of the deposited films on the nanometer scale. Resistive switching of lateral structures smaller than ∝5 nm could be realized which represents the potential of this material for a further downscaling of RRAM devices. The deposition of top electrodes, made of Platinum or Titanium, allowed the electrical characterization of metal-insulator-metal (MIM) structures. An extensive investigation of pristine MIM-devices by impedance spectroscopy showed the big impact of the metal-insulator interface on the overall device resistance. Furthermore, a chemical polarization was studied by dynamical current sweeps and identified as a volatile resistance variation. Usually a forming procedure is needed to ''enable'' the resistive switching properties in MIM devices. The electroforming of these devices was extensively studied and could be

  10. Voltage-controlled ferromagnetism and magnetoresistance in LaCoO3/SrTiO3 heterostructures

    International Nuclear Information System (INIS)

    Hu, Chengqing; Park, Keun Woo; Yu, Edward T.; Posadas, Agham; Demkov, Alexander A.; Jordan-Sweet, Jean L.

    2013-01-01

    A LaCoO 3 /SrTiO 3 heterostructure grown on Si (001) is shown to provide electrically switchable ferromagnetism, a large, electrically tunable magnetoresistance, and a vehicle for achieving and probing electrical control over ferromagnetic behavior at submicron dimensions. Fabrication of devices in a field-effect transistor geometry enables application of a gate bias voltage that modulates strain in the heterostructure via the converse piezoelectric effect in SrTiO 3 , leading to an artificial inverse magnetoelectric effect arising from the dependence of ferromagnetism in the LaCoO 3 layer on strain. Below the Curie temperature of the LaCoO 3 layer, this effect leads to modulation of resistance in LaCoO 3 as large as 100%, and magnetoresistance as high as 80%, both of which arise from carrier scattering at ferromagnetic-nonmagnetic interfaces in LaCoO 3 . Finite-element numerical modeling of electric field distributions is used to explain the dependence of carrier transport behavior on gate contact geometry, and a Valet-Fert transport model enables determination of spin polarization in the LaCoO 3 layer. Piezoresponse force microscopy is used to confirm the existence of piezoelectric response in SrTiO 3 grown on Si (001). It is also shown that this structure offers the possibility of achieving exclusive-NOR logic functionality within a single device

  11. Temperature effect on the retention of U(VI) by SrTiO3

    International Nuclear Information System (INIS)

    Garcia Rosales, G.

    2007-11-01

    The purpose of this research was the study of the interaction mechanisms between U(VI) ions and SrTiO 3 surfaces versus pH and temperature: 25, 50, 75 and 90 C. Firstly, a physicochemical characterization was realized (DRX, MEB, FTIR) and the surface site density was determined. The potentiometric titration data were simulated, for each temperature, using the constant capacitance model and taking into account bath protonation of the ≡Sr-OH surface sites and deprotonation of the ≡Ti-OH ones (one pK a model). Both enthalpy and entropy changes, corresponding to the surface acid-base reactions, were evaluated using the van't Hoff relation. U(VI) was sorbed onto SrTiO 3 powder in the pH range 0.5-5.0 with an U(VI) initial concentration 1.10 -4 M. By TRLIFS two U(VI) complexes were detected associated with two lifetime values (60 ± 5 and 12 ± 2 μs at 25 C). The sorption edges were simulated using FITEQL 4.0 software. The surface complexation constants of the system SrTiO 3 /U(VI) between 25 and 90 C temperature range were thus obtained with the constant capacitance model considering two reactive surface sites. It reveals that two types of surface complex, namely [(≡SrOH)(≡TiOH)UO 2 ] 2+ and [(≡TiOH)(≡TiO)UO 2+ ] 2+ , are needed to properly describe the experimental observations. By application of the van't Hoff equation, Delta R S 0 and Delta R H 0 were obtained, which indicated an endothermic sorption process. Finally, an energy transfer study was realised by TRLIFS. The energy transfer between Tb 3+ and Eu 3+ ions sorbed onto SrTiO 3 powders were investigated. The results showed that the energy transfer between Tb 3+ and Eu 3+ is a non-radiative process and follows a dipole-dipole type interaction. A formalism based on the Dexter and the Inokuti-Hirayama theories was used to calculate the distances (2,7-3,4 Angstroms between Tb 3+ and Eu 3+ onto SrTiO 3 surface. (author)

  12. Plasma plume effects on the conductivity of amorphous-LaAlO3/SrTiO3 interfaces grown by pulsed laser deposition in O2 and Ar

    DEFF Research Database (Denmark)

    Sambri, A.; Christensen, Dennis; Trier, Felix

    2012-01-01

    Amorphous-LaAlO3/SrTiO3 interfaces exhibit metallic conductivity similar to those found for the extensively studied crystalline-LaAlO3/SrTiO3 interfaces. Here, we investigate the conductivity of the amorphous-LaAlO3/SrTiO3 interfaces grown in different pressures of O2 and Ar background gases...

  13. Magnetism Control by Doping in LaAlO3/SrTiO3 Heterointerfaces.

    Science.gov (United States)

    Yan, Hong; Zhang, Zhaoting; Wang, Shuanhu; Wei, Xiangyang; Chen, Changle; Jin, Kexin

    2018-04-25

    Magnetic two-dimensional electron gases at the oxide interfaces are always one of the key issues in spintronics, giving rise to intriguing magnetotransport properties. However, reports about magnetic two-dimensional electron gases remain elusive. Here, we obtain the magnetic order of LaAlO 3 /SrTiO 3 systems by introducing magnetic dopants at the La site. The transport properties with a characteristic of metallic behavior at the interfaces are investigated. More significantly, magnetic-doped samples exhibit obvious magnetic hysteresis loops and the mobility is enhanced. Meanwhile, the photoresponsive experiments are realized by irradiating all samples with a 360 nm light. Compared to magnetism, the effects of dopants on photoresponsive and relaxation properties are negligible because the behavior originates from SrTiO 3 substrates. This work paves a way for revealing and better controlling the magnetic properties of oxide heterointerfaces.

  14. Magnetism and metal-insulator transition in oxygen deficient SrTiO3

    Science.gov (United States)

    Lopez-Bezanilla, Alejandro; Ganesh, P.; Littlewood, Peter

    2015-03-01

    We report new findings in the electronic structure and magnetism of oxygen vacancies in SrTiO3. By means of first-principles calculations we show that the appearance of magnetism in oxygen-deficient SrTiO3 is not determined solely by the presence of a single oxygen vacancy but by the density of free carriers and the relative proximity of the vacant sites. While an isolated vacancy behaves as a non-magnetic double donor, manipulation of the doping conditions allows the stability of a single donor state with emergent local moments. Strong local lattice distortions enhance the binding of this state. Consequently we find that the free-carrier density and strain are fundamental components to obtaining trapped spin-polarized electrons in oxygen-deficient SrTiO3, which may have important implications in the design of switchable magneto-optic devices. AL-B and PBL were supported by DOE-BES under Contract No. DE-AC02-06CH11357. PG was sponsored by the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory, managed by UT- Battelle, LLC, for the US Department of Energy.

  15. Native SrTiO3 (001) surface layer from resonant Ti L2,3 reflectance spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Valvidares, Manuel; Huijben, Mark; Yu, Pu; Ramesh, Ramamoorthy; Kortright, Jeffrey

    2010-11-03

    We quantitatively model resonant Ti L2,3 reflectivity Rs,p(q, hn) from several SrTiO3 (001) single crystals having different initial surface preparations and stored in ambient conditions before and between measurements. All samples exhibit unexpected 300 K Rs(hn) - Rp(hn) anisotropy corresponding to weak linear dichroism and tetragonal distortion of the TiO6 octahedra indicating a surface layer with properties different from cubic SrTiO3. Oscillations in Rs(q) confirm a ubiquitous surface layer 2-3 nm thick that evolves over a range of time scales. Resonant optical constant spectra derived from Rs,p(hn) assuming a uniform sample are refined using a single surface layer to fit measured Rs(q). Differences in surface layer and bulk optical properties indicate that the surface is significantly depleted in Sr and enriched in Ti and O. While consistent with the tendency of SrTiO3 surfaces toward non-stoichiometry, this layer does not conform simply to existing models for the near surface region and apparently forms via room temperature surface reactions with the ambient. This new quantitative spectral modeling approach is generally applicable and has potential to study near-surface properties of a variety of systems with unique chemical and electronic sensitivities.

  16. Resistance switching at the interface of LaAlO3/SrTiO3

    DEFF Research Database (Denmark)

    Chen, Yunzhong; Zhao, J.L.; Sun, J.R.

    2010-01-01

    At the interface of LaAlO3/SrTiO3 with film thickness of 3 unit cells or greater, a reproducible electric-field-induced bipolar resistance switching of the interfacial conduction is observed on nanometer scale by a biased conducting atomic force microscopy under vacuum environment. The switching ...

  17. Prediction of two-dimensional electron gas mediated magnetoelectric coupling at ferroelectric PbTiO3/SrTiO3 heterostructures

    Science.gov (United States)

    Wei, Lan-ying; Lian, Chao; Meng, Sheng

    2017-05-01

    First-principles calculations predict the emergence of magnetoelectric coupling mediated by two-dimensional electron gas (2DEG) at the ferroelectric PbTiO3/SrTiO3 heterostructure. Free electrons endowed by naturally existing oxygen vacancies in SrTiO3 are driven to the heterostructure interface under the polarizing field of ferroelectric PbTiO3 to form a 2DEG. The electrons are captured by interfacial Ti atoms, which surprisingly exhibits ferromagnetism even at room temperature with a small critical density of ˜15.5 μ C /cm2 . The ferroelectricity-controlled ferromagnetism mediated by interfacial 2DEG shows strong magnetoelectric coupling strength, enabling convenient control of magnetism by electric field and vice versa. The PbTiO3/SrTiO3 heterostructure is cheap, easily grown, and controllable, promising future applications in low-cost spintronics and information storage at ambient condition.

  18. Electrostatic analysis of n-doped SrTiO3 metal-insulator-semiconductor systems

    International Nuclear Information System (INIS)

    Kamerbeek, A. M.; Banerjee, T.; Hueting, R. J. E.

    2015-01-01

    Electron doped SrTiO 3 , a complex-oxide semiconductor, possesses novel electronic properties due to its strong temperature and electric-field dependent permittivity. Due to the high permittivity, metal/n-SrTiO 3 systems show reasonably strong rectification even when SrTiO 3 is degenerately doped. Our experiments show that the insertion of a sub nanometer layer of AlO x in between the metal and n-SrTiO 3 interface leads to a dramatic reduction of the Schottky barrier height (from around 0.90 V to 0.25 V). This reduces the interface resistivity by 4 orders of magnitude. The derived electrostatic analysis of the metal-insulator-semiconductor (n-SrTiO 3 ) system is consistent with this trend. When compared with a Si based MIS system, the change is much larger and mainly governed by the high permittivity of SrTiO 3 . The non-linear permittivity of n-SrTiO 3 leads to unconventional properties such as a temperature dependent surface potential non-existent for semiconductors with linear permittivity such as Si. This allows tuning of the interfacial band alignment, and consequently the Schottky barrier height, in a much more drastic way than in conventional semiconductors

  19. Synthesis of Non-uniformly Pr-doped SrTiO3 Ceramics and Their Thermoelectric Properties

    KAUST Repository

    Mehdizadeh Dehkordi, Arash; Bhattacharya, Sriparna; Darroudi, Taghi; Zeng, Xiaoyu; Alshareef, Husam N.; Tritt, Terry M.

    2015-01-01

    We demonstrate a novel synthesis strategy for the preparation of Pr-doped SrTiO3 ceramics via a combination of solid state reaction and spark plasma sintering techniques. Polycrystalline ceramics possessing a unique morphology can be achieved by optimizing the process parameters, particularly spark plasma sintering heating rate. The phase and morphology of the synthesized ceramics were investigated in detail using X-ray diffraction, scanning electron microcopy and energy-dispersive X-ray spectroscopy It was observed that the grains of these bulk Pr-doped SrTiO3 ceramics were enhanced with Pr-rich grain boundaries. Electronic and thermal transport properties were also investigated as a function of temperature and doping concentration Such a microstructure was found to give rise to improved thermoelectric properties. Specifically, it resulted in a significant improvement in carrier mobility and the thermoelectric power factor. Simultaneously, it also led to a marked reduction in the thermal conductivity. As a result, a significant improvement (> 30%) in the thermoelectric figure of merit was achieved for the whole temperature range over all previously reported maximum values for SrTiO3-based ceramics. This synthesis demonstrates the steps for the preparation of bulk polycrystalline ceramics of non-uniformly Pr-doped SrTiO3.

  20. Synthesis of Non-uniformly Pr-doped SrTiO3 Ceramics and Their Thermoelectric Properties

    KAUST Repository

    Mehdizadeh Dehkordi, Arash

    2015-08-15

    We demonstrate a novel synthesis strategy for the preparation of Pr-doped SrTiO3 ceramics via a combination of solid state reaction and spark plasma sintering techniques. Polycrystalline ceramics possessing a unique morphology can be achieved by optimizing the process parameters, particularly spark plasma sintering heating rate. The phase and morphology of the synthesized ceramics were investigated in detail using X-ray diffraction, scanning electron microcopy and energy-dispersive X-ray spectroscopy It was observed that the grains of these bulk Pr-doped SrTiO3 ceramics were enhanced with Pr-rich grain boundaries. Electronic and thermal transport properties were also investigated as a function of temperature and doping concentration Such a microstructure was found to give rise to improved thermoelectric properties. Specifically, it resulted in a significant improvement in carrier mobility and the thermoelectric power factor. Simultaneously, it also led to a marked reduction in the thermal conductivity. As a result, a significant improvement (> 30%) in the thermoelectric figure of merit was achieved for the whole temperature range over all previously reported maximum values for SrTiO3-based ceramics. This synthesis demonstrates the steps for the preparation of bulk polycrystalline ceramics of non-uniformly Pr-doped SrTiO3.

  1. Thermal infrared and microwave absorbing properties of SrTiO3/SrFe12O19/polyaniline nanocomposites

    International Nuclear Information System (INIS)

    Hosseini, Seyed Hossein; Zamani, Parisa; Mousavi, S.Y.

    2015-01-01

    Graphical abstract: We have developed a new perspective of applications and properties of conducting polymers. The combination of absorption ability prepared nanocomposites in the present of PANI display a great potential in organization of shielding structures into thermal IR and microwave. Further investigations using other conducting polymers to demonstrate their capability for advance thermal IR and microwave shielding devices is under way. The application of these samples may improve the IR thermographic detection, catalysis, sensors, magnetic data storage, electromagnetic resonance wave absorption, photonic crystals, and microelectronic devices and military aspects. - Highlights: • The SrTiO 3 /SrFe 12 O 19 /PANI exhibited electric and electromagnetic properties. • The SrTiO 3 /SrFe 12 O 19 /PANI has shielding structures into thermal IR and microwave. • Increasing weight ratios and thicknesses will increase thermal IR ability. • Increasing weight ratios and thicknesses will increase microwave absorption ability. - Abstract: Polyaniline (PANI) as a unique polymer that also has electromagnetic absorption used as the substrate. In this research, SrTiO 3 was synthesized as IR absorbent and core and then SrFe 12 O 19 as microwave absorbent was prepared on SrTiO 3 via co-precipitation method as the first shell. As the next step, PANI was coated on SrTiO 3 /SrFe 12 O 19 nanoparticles via in situ polymerization by multi core–shell structures (SrTiO 3 /SrFe 12 O 19 /PANI). Nanometer size and structures of samples were measured by TEM, XRD and FTIR. Morphology of nanocomposite was showed by SEM images. The magnetic and electric properties were also performed by VSM and four probe techniques. Thermal infrared (IR) absorption and microwave reflection loss of nanocomposites were investigated at 10–40 μm and 8–12 GHz, IR and microwave frequencies, respectively. The results showed that the SrTiO 3 /SrFe 12 O 19 /PANI nanocomposites have good compatible

  2. High mobility half-metallicity in the (LaMnO3)2/(SrTiO3)8 superlattice

    KAUST Repository

    Cossu, Fabrizio

    2013-01-28

    First principles calculations have been performed to investigate the LaMnO3/SrTiO3 superlattice. Structural relaxation within the generalized gradient approximation results in no significant tiltings or rotations of oxygen octahedra, but in distinct distortions in the SrTiO3 region. Taking into account the onsite Coulomb interaction, we find that the Mn spins order ferromagnetically, in contrast to the antiferromagnetic state of bulk LaMnO3. Most importantly, the interface strain combined with charge transfer across the interface induces half-metallicity within the MnO2 layers. The superlattice is particulary interesting for spintronics applications because the half-metallic states are characterized by an extraordinary high mobility.

  3. High mobility half-metallicity in the (LaMnO3)2/(SrTiO3)8 superlattice

    KAUST Repository

    Cossu, Fabrizio; Schwingenschlö gl, Udo; Singh, Nirpendra

    2013-01-01

    First principles calculations have been performed to investigate the LaMnO3/SrTiO3 superlattice. Structural relaxation within the generalized gradient approximation results in no significant tiltings or rotations of oxygen octahedra, but in distinct distortions in the SrTiO3 region. Taking into account the onsite Coulomb interaction, we find that the Mn spins order ferromagnetically, in contrast to the antiferromagnetic state of bulk LaMnO3. Most importantly, the interface strain combined with charge transfer across the interface induces half-metallicity within the MnO2 layers. The superlattice is particulary interesting for spintronics applications because the half-metallic states are characterized by an extraordinary high mobility.

  4. Tunability of resonance frequencies in a superconducting microwave resonator by using SrTiO sub 3 ferroelectric films

    CERN Document Server

    Sok, J; Lee, E H

    1998-01-01

    An applied dc voltage varies the dielectric constant of ferroelectric SrTiO sub 3 films. A tuning mechanism for superconducting microwave resonators was realized by using the variation in the dielectric constant of SrTiO sub 3 films. In order to estimate the values of the capacitance, C, and the loss tangent, tan delta, of SrTiO sub 3 ferroelectric capacitors, we used high-temperature superconducting microwave resonators which were composed of two ports, two poles, and dc bias circuits at the zero-field points. SrTiO sub 3 ferroelectric capacitors successfully controlled the resonant frequency of the resonator. Resonant frequencies of 3.98 GHz and 4.20 GHz were measured at bias voltages of 0 V and 50 V which correspond to capacitance values of 0.94 pF and 0.7pF, respectively. The values of the loss tangent, tan delta sub e sub f sub f , obtained in this measurements, were about 0.01.

  5. Texturing of sodium bismuth titanate-barium titanate ceramics by templated grain growth

    Science.gov (United States)

    Yilmaz, Huseyin

    2002-01-01

    Sodium bismuth titanate modified with barium titanate, (Na1/2Bi 1/2)TiO3-BaTiO3 (NBT-BT), is a candidate lead-free piezoelectric material which has been shown to have comparatively high piezoelectric response. In this work, textured (Na1/2Bi1/2)TiO 3-BaTiO3 (5.5mol% BaTiO3) ceramics with pc (where pc denotes the pseudocubic perovskite cell) orientation were fabricated by Templated Grain Growth (TGG) or Reactive Templated Grain Growth (RTGG) using anisotropically shaped template particles. In the case of TGG, molten salt synthesized SrTiO3 platelets were tape cast with a (Na1/2Bi1/2)TiO3-5.5mol%BaTiO3 powder and sintered at 1200°C for up to 12 hours. For the RTGG approach, Bi4Ti3O12 (BiT) platelets were tape cast with a Na2CO3, Bi2O3, TiO 2, and BaCO3 powder mixture and reactively sintered. The TGG approach using SrTiO3 templates gave stronger texture along [001] compared to the RTGG approach using BiT templates. The textured ceramics were characterized by X-ray and electron backscatter diffraction for the quality of texture. The texture function was quantified by the Lotgering factor, rocking curve, pole figures, inverse pole figures, and orientation imaging microscopy. Electrical and electromechanical property characterization of randomly oriented and pc textured (Na1/2Bi1/2)TiO 3-5.5 mol% BaTiO3 rhombohedral ceramics showed 0.26% strain at 70 kV/cm, d33 coefficients over 500 pC/N have been obtained for highly textured samples (f ˜ 90%). The piezoelectric coefficient from Berlincourt was d33 ˜ 200 pC/N. The materials show considerable hysteresis. The presence of hysteresis in the unipolar-electric field curve is probably linked to the ferroelastic phase transition seen in the (Na 1/2Bi1/2)TiO3 system on cooling from high temperature at ˜520°C. The macroscopic physical properties (remanent polarization, dielectric constant, and piezoelectric coefficient) of random and textured ([001] pc) rhombohedral perovskites were estimated by linear averaging of single

  6. LCAO calculations of SrTiO3 nanotubes

    International Nuclear Information System (INIS)

    Evarestov, Robert; Bandura, Andrei

    2011-01-01

    The large-scale first-principles simulation of the structure and stability of SrTiO 3 nanotubes is performed for the first time using the periodic PBE0 LCAO method. The initial structures of the nanotubes have been obtained by the rolling up of the stoichiometric SrTiO 3 slabs consisting of two or four alternating (001) SrO and TiO 2 atomic planes. Nanotubes (NTs) with chiralities (n,0) and (n,n) have been studied. Two different NTs were constructed for each chirality: (I) with SrO outer shell, and (II) with TiO 2 outer shell. Positions of all atoms have been optimized to obtain the most stable NT structure . In the majority of considered cases the inner or outer TiO 2 shells of NT undergo a considerable reconstruction due to shrinkage or stretching of interatomic distances in the initial cubic perovskite structure. There were found two types of surface reconstruction: (1) breaking of Ti-O bonds with creating of Ti = O titanyl groups in outer surface; (2) inner surface folding due to Ti-O-Ti bending. Based on strain energy calculations the largest stability was found for (n,0) NTs with TiO 2 outer shell.

  7. Microscopic characterization of Fe nanoparticles formed on SrTiO3(001 and SrTiO3(110 surfaces

    Directory of Open Access Journals (Sweden)

    Miyoko Tanaka

    2016-06-01

    Full Text Available Fe nanoparticles grown on SrTiO3 (STO {001} and {110} surfaces at room temperature have been studied in ultrahigh vacuum by means of transmission electron microscopy and scanning tunnelling microscopy. It was shown that some Fe nanoparticles grow epitaxially. They exhibit a modified Wulff shape: nanoparticles on STO {001} surfaces have truncated pyramid shapes while those on STO {110} surfaces have hexagonal shapes. From profile-view TEM images, approximate values of the adhesion energy of the nanoparticles for both shapes are obtained.

  8. Epitaxial growth and thermodynamic stability of SrIrO3/SrTiO3 heterostructures

    Science.gov (United States)

    Groenendijk, D. J.; Manca, N.; Mattoni, G.; Kootstra, L.; Gariglio, S.; Huang, Y.; van Heumen, E.; Caviglia, A. D.

    2016-07-01

    Obtaining high-quality thin films of 5d transition metal oxides is essential to explore the exotic semimetallic and topological phases predicted to arise from the combination of strong electron correlations and spin-orbit coupling. Here, we show that the transport properties of SrIrO3 thin films, grown by pulsed laser deposition, can be optimized by considering the effect of laser-induced modification of the SrIrO3 target surface. We further demonstrate that bare SrIrO3 thin films are subject to degradation in air and are highly sensitive to lithographic processing. A crystalline SrTiO3 cap layer deposited in-situ is effective in preserving the film quality, allowing us to measure metallic transport behavior in films with thicknesses down to 4 unit cells. In addition, the SrTiO3 encapsulation enables the fabrication of devices such as Hall bars without altering the film properties, allowing precise (magneto)transport measurements on micro- and nanoscale devices.

  9. Structure and cation distribution of (Mn0.5Zn0.5)Fe2O4 thin films on SrTiO3(001)

    Science.gov (United States)

    Welke, M.; Brachwitz, K.; Lorenz, M.; Grundmann, M.; Schindler, K.-M.; Chassé, A.; Denecke, R.

    2017-06-01

    A comprehensive study on growth of ferrimagnetic manganese zinc ferrite (Mn0.5Zn0.5Fe2O4) films on single crystalline strontium titanate(001) (SrTiO3) substrates was carried out. Under the optimized conditions, a thin film with a layer thickness of 200 nm was deposited, and the structural properties were investigated. Contrary to data published in literature, no buffer layer was necessary to achieve epitaxial growth of a poorly lattice-matched layer. This was confirmed for Mn0.5Zn0.5Fe2O4(001) on SrTiO3(001) by x-ray diffraction and the adjoined phi scans, which also revealed a lattice compression of 1.2% of the manganese zinc ferrite film in the out-of-plane direction. Using x-ray photoelectron spectroscopy, the near surface stoichiometry of the film could be shown to agree with the intended one within the uncertainty of the method. X-ray absorption spectroscopy showed an electronic structure close to that published for bulk samples. Additional x-ray magnetic circular dichroism investigations were performed to answer detailed structural questions by a comparison of experimental data with the calculated ones. The calculations took into account ion sites (tetrahedral vs. octahedral coordination) as well as the charge of Fe ions (Fe2+ vs. Fe3+). Contrary to the expectation for a perfect normal spinel that only Fe3+ ions are present in octahedral sites, hints regarding the presence of additional Fe2+ in octahedral sites as well as Fe3+ ions in tetrahedral sites have been obtained. Altogether, the layer could be shown to be mostly in a normal spinel configuration.

  10. Titan through Time: Evolution of Titan's Atmosphere and its Hydrocarbon Cycle on the Surface

    Science.gov (United States)

    Gilliam, Ashley E.

    The Introduction and Appendix i-A outline briefly the history of Titan exploration since its discovery by Christiaan Huygens in 1675 through the recent International Mission of Cassini-Huygens.. Chapter 1: This chapter discusses two possible pathways of loss of the two main gases from Titan's post-accretional atmosphere, methane (CH 4) and ammonia (NH3), by the mechanisms of thermal escape and emission from the interior coupled with thermal escape. Chapter 2: In this chapter, a simple photolysis model is created, where the second most abundant component of the present-day Titan atmosphere, methane (CH4), can either escape the atmosphere or undergo photolytic conversion to ethane (C2H6). Chapter 3: This chapter examines different fluvial features on Titan, identified by the Cassini spacecraft, and evaluates the possibilities of channel formation by two mechanisms: dissolution of ice by a concentrated solution of ammonium sulfate, and by mechanical erosion by flow of liquid ammonia and liquid ethane. Chapter 4: This chapter presents: (1) new explicit mathematical solutions of mixed 1st and 2nd order chemical reactions, represented by ordinary differential first-degree and Riccati equations; (2) the computed present-day concentrations of the three gases in Titan's scale atmosphere, treated as at near-steady state; and (3) an analysis of the reported and computed atmospheric concentrations of CH4, CH 3, and C2H6 on Titan, based on the reaction rate parameters of the species, the rate parameters taken as constants representative of their mean values. Chapter 5: This chapter examines the possible reactions of methane formation in terms of the thermodynamic relationships of the reactions that include pure carbon as graphite, the gases H2, CO2, H2 O, and serpentinization and magnetite formation from olivine fayalite. (Abstract shortened by ProQuest.).

  11. Potential Fluctuations at Low Temperatures in Mesoscopic-Scale SmTiO3/SrTiO3/SmTiO3 Quantum Well Structures.

    Science.gov (United States)

    Hardy, Will J; Isaac, Brandon; Marshall, Patrick; Mikheev, Evgeny; Zhou, Panpan; Stemmer, Susanne; Natelson, Douglas

    2017-04-25

    Heterointerfaces of SrTiO 3 with other transition metal oxides make up an intriguing family of systems with a bounty of coexisting and competing physical orders. Some examples, such as LaAlO 3 /SrTiO 3 , support a high carrier density electron gas at the interface whose electronic properties are determined by a combination of lattice distortions, spin-orbit coupling, defects, and various regimes of magnetic and charge ordering. Here, we study electronic transport in mesoscale devices made with heterostructures of SrTiO 3 sandwiched between layers of SmTiO 3 , in which the transport properties can be tuned from a regime of Fermi-liquid like resistivity (ρ ∝ T 2 ) to a non-Fermi liquid (ρ ∝ T 5/3 ) by controlling the SrTiO 3 thickness. In mesoscale devices at low temperatures, we find unexpected voltage fluctuations that grow in magnitude as T is decreased below 20 K, are suppressed with increasing contact electrode size, and are independent of the drive current and contact spacing distance. Magnetoresistance fluctuations are also observed, which are reminiscent of universal conductance fluctuations but not entirely consistent with their conventional properties. Candidate explanations are considered, and a mechanism is suggested based on mesoscopic temporal fluctuations of the Seebeck coefficient. An improved understanding of charge transport in these model systems, especially their quantum coherent properties, may lead to insights into the nature of transport in strongly correlated materials that deviate from Fermi liquid theory.

  12. Promoting Photocatalytic Overall Water Splitting by Controlled Magnesium Incorporation in SrTiO3 Photocatalysts.

    Science.gov (United States)

    Han, Kai; Lin, Yen-Chun; Yang, Chia-Min; Jong, Ronald; Mul, Guido; Mei, Bastian

    2017-11-23

    SrTiO 3 is a well-known photocatalyst inducing overall water splitting when exposed to UV irradiation of wavelengths water-splitting efficiency of the Mg:SrTiO x composites is up to 20 times higher compared to SrTiO 3 containing similar catalytic nanoparticles, and an apparent quantum yield (AQY) of 10 % can be obtained in the wavelength range of 300-400 nm. Detailed characterization of the Mg:SrTiO x composites revealed that Mg is likely substituting the tetravalent Ti ion, leading to a favorable surface-space-charge layer. This originates from tuning of the donor density in the cubic SrTiO 3 structure by Mg incorporation and enables high oxygen-evolution rates. Nevertheless, interfacing with an appropriate hydrogen evolution catalyst is mandatory and non-trivial to obtain high-performance in water splitting. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Controlling the conductivity of amorphous LaAlO3/SrTiO3 interfaces by in-situ application of an electric field during fabrication

    DEFF Research Database (Denmark)

    Trier, Felix; Amoruso, S.; Christensen, Dennis Valbjørn

    2013-01-01

    Amorphous-LaAlO3/SrTiO3 interfaces present metallic conductivity similar to those found in their all-crystalline counterparts. Here, the conductivity of amorphous-LaAlO3/SrTiO3 interfaces is modified by an external electric field applied in-situ with a biased truncated cone electrode (−10 V ≤ Vbias...

  14. Synthesis of BiFeO3 thin films on single-terminated Nb : SrTiO3 (111 substrates by intermittent microwave assisted hydrothermal method

    Directory of Open Access Journals (Sweden)

    Ivan Velasco-Davalos

    2016-06-01

    Full Text Available We report on a simple and fast procedure to create arrays of atomically flat terraces on single crystal SrTiO3 (111 substrates and the deposition of ferroelectric BiFeO3 thin films on such single-terminated surfaces. A microwave-assisted hydrothermal method in deionized water and ammonia solution selectively removes either (SrO34− or Ti4+ layers to ensure the same chemical termination on all terraces. Measured step heights of 0.225 nm (d111 and uniform contrast in the phase image of the terraces confirm the single termination in pure and Nb doped SrTiO3 single crystal substrates. Multiferroic BiFeO3 thin films were then deposited by the same microwave assisted hydrothermal process on Nb : SrTiO3 (111 substrates. Bi(NO33 and Fe(NO33 along with KOH served as the precursors solution. Ferroelectric behavior of the BiFeO3 films on Nb : SrTiO3 (100 substrates was verified by piezoresponse force microscopy.

  15. Síntese de BaTIO3 e SrTIO3 pelo método hidrotermal assistido por micro-ondas utilizando anatase como precursor de titânio

    Directory of Open Access Journals (Sweden)

    Renata S. Magalhães

    Full Text Available In this work barium titanate (BT and strontium titanate (ST were prepared by Microwave-Assisted Hydrothermal (MAH method, using a Ti precursor different from those shown in the literature and various concentrations (1, 3 e 6 mol L-1 of KOH mineralizer. As a titanium precursor, an anatase complex with hydrogen peroxide were used. For the precursors of barium and strontium, chlorides were used. The materials resulting from the synthesis processes were characterized in room temperature by different techniques as like: X-Ray Diffraction (XRD, micro-Raman Spectroscopy, UV-Vis, Scanning Electron Microscopy (SEM and Photoluminescence (PL. The results show that there were differences in crystallinity, morphology, number of phases and photoluminescence depending on the concentration of the mineralizer.

  16. Characterization of irradiation damage distribution near TiO2/SrTiO3 interfaces using coherent acoustic phonon interferometry

    International Nuclear Information System (INIS)

    Yarotski, Dmitry; Yan Li; Jia Quanxi; Taylor, Antoinette J.; Fu Engang; Wang Yongqiang; Uberuaga, Blas P.

    2012-01-01

    We apply ultrafast coherent acoustic phonon interferometry to characterize the distribution of the radiation damage near the TiO 2 /SrTiO 3 interfaces. We show that the optical and mechanical properties of anatase TiO 2 remain unaffected by the radiation dosages in the 0.1÷5 dpa (displacements per atom) range, while the degraded optical response indicates a significant defect accumulation in the interfacial region of SrTiO 3 at 0.1 dpa and subsequent amorphization at 3 dpa. Comparison between the theoretical simulations and the experimental results reveals an almost threefold reduction of the sound velocity in the irradiated SrTiO 3 layer with peak damage levels of 3 and 5 dpa.

  17. Universality of electron mobility in LaAlO3/SrTiO3 and bulk SrTiO3

    Science.gov (United States)

    Trier, Felix; Reich, K. V.; Christensen, Dennis Valbjørn; Zhang, Yu; Tuller, Harry L.; Chen, Yunzhong; Shklovskii, B. I.; Pryds, Nini

    2017-08-01

    Metallic LaAlO3/SrTiO3 (LAO/STO) interfaces attract enormous attention, but the relationship between the electron mobility and the sheet electron density, ns, is poorly understood. Here, we derive a simple expression for the three-dimensional electron density near the interface, n3 D , as a function of ns and find that the mobility for LAO/STO-based interfaces depends on n3 D in the same way as it does for bulk doped STO. It is known that undoped bulk STO is strongly compensated with N ≃5 ×1018 cm-3 background donors and acceptors. In intentionally doped bulk STO with a concentration of electrons n3 DN , the mobility collapses because scattering happens on n3 D intentionally introduced donors. For LAO/STO, the polar catastrophe which provides electrons is not supposed to provide an equal number of random donors and thus the mobility should be larger. The fact that the mobility is still the same implies that for the LAO/STO, the polar catastrophe model should be revisited.

  18. Research Update: Conductivity and beyond at the LaAlO3/SrTiO3 interface

    Directory of Open Access Journals (Sweden)

    S. Gariglio

    2016-06-01

    Full Text Available In this review, we focus on the celebrated interface between two band insulators, LaAlO3 and SrTiO3, that was found to be conducting, superconducting, and to display a strong spin-orbit coupling. We discuss the formation of the 2-dimensional electron liquid at this interface, the particular electronic structure linked to the carrier confinement, the transport properties, and the signatures of magnetism. We then highlight distinctive characteristics of the superconducting regime, such as the electric field effect control of the carrier density, the unique tunability observed in this system, and the role of the electronic subband structure. Finally we compare the behavior of Tc versus 2D doping with the dome-like behavior of the 3D bulk superconductivity observed in doped SrTiO3. This comparison reveals surprising differences when the Tc behavior is analyzed in terms of the 3D carrier density for the interface and the bulk.

  19. High charge carrier density at the NaTaO3/SrTiO3 hetero-interface

    KAUST Repository

    Nazir, Safdar; Schwingenschlö gl, Udo

    2011-01-01

    The formation of a (quasi) two-dimensional electron gas between the band insulators NaTaO3 and SrTiO3 is studied by means of the full-potential linearized augmented plane-wave method of density functional theory. Optimization of the atomic positions

  20. Dielectric characterization of low-loss calcium strontium titanate fibers produced by laser floating zone technique for wireless communication

    International Nuclear Information System (INIS)

    Amaral, F.; Valente, M.A.; Costa, L.C.; Costa, F.M.

    2014-01-01

    Wireless communication technology assisted to a huge development during the last two decades, responding to the growing demand for small size and low weight devices such as cell phones and global positioning systems. The need for miniaturization and higher autonomy resulted in the development of new dielectric oxide ceramics with very specific properties, to be applied as dielectric resonators in filters, oscillators, and antennas. Some crucial properties as a high quality factor, high dielectric constant, and near zero temperature coefficient of resonant frequency must be considered during the selection of the appropriate materials. The present work deals with the preparation of calcium titanate (CaTiO 3 ), strontium titanate (SrTiO 3 ), and calcium strontium titanate (Ca x Sr 1-x TiO 3 ) fibers produced by laser floating zone (LFZ) technique. Our results show that fibers grown at lower pulling rates exhibit higher ε', for all the studied frequency range, including the microwave region. Moreover, the quality factor is always high envisaging the possibility to include these materials in future wireless device applications. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  1. Electrochemical characterization and redox behavior of Nb-doped SrTiO3

    DEFF Research Database (Denmark)

    Blennow Tullmar, Peter; Kammer Hansen, Kent; Wallenberg, L. Reine

    2009-01-01

    Sr-vacancy compensated Nb-doped SrTiO3 with the nominal composition Sr0.94Ti0.9Nb0.1O3 has been evaluated as a solid oxide fuel cell (SOFC) anode material in terms of redox stability and electrochemical properties. Sr0.94Ti0.9Nb0.1O3 has been synthesized with a recently developed modified glycine......-nitrate process. The phase purity and redox behavior have been analyzed with XRD and TGA. The electrochemical properties of Sr0.94Ti0.9Nb0.1O3 and a composite electrode of Sr0.94Ti0.9Nb0.1O3/YSZ have been investigated by electrochemical impedance spectroscopy (EIS) on cone shaped electrodes and on electrodes...... in a symmetrical cell configuration. The experiments indicated that the Nb-doped SrTiO3 electrodes were redox stable and showed a potential ability to be used as a part of a SOFC anode. The electrochemical activity appeared to be governed by the concentration of defect species (especially Ti3+ and V-0...

  2. Adsorption of UO22+ in surfaces of SrTiO3

    International Nuclear Information System (INIS)

    Ortiz O, H.B.; Ordonez R, E.; Fernandez V, S.M.

    2005-01-01

    The internationally accepted solution in the administration of the high level radioactive residuals is the multi barrier deep geologic storage which should guarantee that do not exist flights neither transfer of residuals to the atmosphere in time periods of at least 10,000 years. In this confinement type exists the interest to study materials that can be used as engineering barriers as well as the diverse interaction phenomena between these and the radionuclides. In this work it is presented the physicochemical characterization and evaluation of the surface properties and of adsorption of U(VI) in form of UO 2 (NO 3 ) 2 on the SrTiO 3 like possible candidate for contention barrier in the deep geologic confinement. The made studies showed that the SrTiO 3 is stable to temperatures between 0 and 800 C. At the same time it could settle down that the maximum sorption percentages are reached to near pH to the isoelectric point, where chemical species prevail in solution of the type UO 2 (X) - . (Author)

  3. Visible light carrier generation in co-doped epitaxial titanate films

    Energy Technology Data Exchange (ETDEWEB)

    Comes, Ryan B.; Smolin, Sergey Y.; Kaspar, Tiffany C.; Gao, Ran; Apgar, Brent A.; Martin, Lane W.; Bowden, Mark E.; Baxter, Jason; Chambers, Scott A.

    2015-03-02

    Perovskite titanates such as SrTiO3 (STO) exhibit a wide range of important functional properties, including high electron mobility, ferroelectricity—which may be valuable in photovoltaic applications—and excellent photocatalytic performance. The wide optical band gap of titanates limits their use in these applications, however, making them ill-suited for integration into solar energy harvesting technologies. Our recent work has shown that by doping STO with equal concentrations of La and Cr we can enhance visible light absorption in epitaxial thin films while avoiding any compensating defects. In this work, we explore the optical properties of photoexcited carriers in these films. Using spectroscopic ellipsometry, we show that the Cr3+ dopants, which produce electronic states immediately above the top of the O 2p valence band in STO reduce the direct band gap of the material from 3.75 eV to between 2.4 and 2.7 eV depending on doping levels. Transient reflectance measurements confirm that optically generated carriers have a recombination lifetime comparable to that of STO and are in agreement with the observations from ellipsometry. Finally, through photoelectrochemical yield measurements, we show that these co-doped films exhibit enhanced visible light photocatalysis when compared to pure STO.

  4. Influence of SrTiO3 modification on dielectric properties of Mg(Zr0.05Ti0.95)O3 ceramics at microwave frequency

    International Nuclear Information System (INIS)

    Tseng, Ching-Fang; Lu, Shu-Cheng

    2013-01-01

    Highlights: ► The microwave dielectric properties of (1−x)Mg(Zr 0.05 Ti 0.95 )O 3 –xSrTiO 3 system have been discussed. ► The dielectric constant and τ f increased; nevertheless, the Q × f decreased with an increase in x. ► Second phases were formed and affected the microwave dielectric properties of (1−x)MZT–xST system. ► ε r of 20.8, Q × f of 257,000, and τ f of 0.2 ppm/°C were obtained for the 0.06Mg(Zr 0.05 Ti 0.95 )O 3 –0.04SrTiO 3 ceramics. ► Due to high-quality factor and near-zero τ f , MZT–ST demonstrate a good potential for use in microwave devices. -- Abstract: The microwave dielectric properties and microstructures were investigated in the (1−x)Mg(Zr 0.05 Ti 0.95 )O 3 –xSrTiO 3 (hereafter referred to as (1−x)MZT–xST) system. The compounds were prepared via the conventional solid-state reaction. Compositions in the (1−x)Mg(Zr 0.05 Ti 0.95 )O 3 –xSrTiO 3 system were designed to compensate the negative temperature coefficient of the resonant frequency of Mg(Zr 0.05 Ti 0.95 )O 3 . The values displayed nonmonotonic mixture-like behavior, because the TiO 2 phase was formed in the MZT composite ceramics with increasing x. A close zero τ f of 0.2 ppm/°C could be achieved at 0.96MZT–0.04ST with ε r = 20.8 and Q × f = 257,000 GHz

  5. Charge modulated interfacial conductivity in SrTiO3-based oxide heterostructures

    DEFF Research Database (Denmark)

    Chen, Yunzhong; Stamate, Eugen; Pryds, Nini

    2011-01-01

    When depositing amorphous SrTiO3 (STO) films on crystalline STO substrates by pulsed laser deposition, metallic interfaces are observed, though both materials are band-gap insulators. The interfacial conductivity exhibits strong dependence on oxygen pressure during film growth, which is closely...

  6. Electrical transport across nanometric SrTiO3 and BaTiO3 barriers in conducting/insulator/conducting junctions

    Science.gov (United States)

    Navarro, H.; Sirena, M.; González Sutter, J.; Troiani, H. E.; del Corro, P. G.; Granell, P.; Golmar, F.; Haberkorn, N.

    2018-01-01

    We report the electrical transport properties of conducting/insulator/conducting heterostructures by studying current-voltage IV curves at room temperature. The measurements were obtained on tunnel junctions with different areas (900, 400 and 100 μm2) using a conducting atomic force microscope. Trilayers with GdBa2Cu3O7 (GBCO) as the bottom electrode, SrTiO3 or BaTiO3 (thicknesses between 1.6 and 4 nm) as the insulator barrier, and GBCO or Nb as the top electrode were grown by DC sputtering on (100) SrTiO3 substrates For SrTiO3 and BaTiO3 barriers, asymmetric IV curves at positive and negative polarization can be obtained using electrodes with different work function. In addition, hysteretic IV curves are obtained for BaTiO3 barriers, which can be ascribed to a combined effect of the FE reversal switching polarization and an oxygen vacancy migration. For GBCO/BaTiO3/GBCO heterostructures, the IV curves correspond to that expected for asymmetric interfaces, which indicates that the disorder affects differently the properties at the bottom and top interfaces. Our results show the role of the interface disorder on the electrical transport of conducting/insulator/conduction heterostructures, which is relevant for different applications, going from resistive switching memories (at room temperature) to Josephson junctions (at low temperatures).

  7. How Correlated is the FeSe /SrTiO3 System?

    Science.gov (United States)

    Mandal, Subhasish; Zhang, Peng; Ismail-Beigi, Sohrab; Haule, K.

    2017-08-01

    Recent observation of ˜10 times higher critical temperature in a FeSe monolayer compared with its bulk phase has drawn a great deal of attention because the electronic structure in the monolayer phase appears to be different than bulk FeSe. Using a combination of density functional theory and dynamical mean field theory, we find electronic correlations have important effects on the predicted atomic-scale geometry and the electronic structure of the monolayer FeSe on SrTiO3 . The electronic correlations are dominantly controlled by the Se-Fe-Se angle either in the bulk phase or the monolayer phase. But the angle sensitivity increases and the orbital differentiation decreases in the monolayer phase compared to the bulk phase. The correlations are more dependent on Hund's J than Hubbard U . The observed orbital selective incoherence to coherence crossover with temperature confirms the Hund's metallic nature of the monolayer FeSe. We also find electron doping by oxygen vacancies in SrTiO3 increases the correlation strength, especially in the dx y orbital by reducing the Se-Fe-Se angle.

  8. Enhanced thermoelectric figure-of-merit in thermally robust, nanostructured superlattices based on SrTiO3

    KAUST Repository

    Abutaha, Anas I.

    2015-03-24

    Thermoelectric (TE) metal oxides overcome crucial disadvantages of traditional heavy-metal-alloy-based TE materials, such as toxicity, scarcity, and instability at high temperatures. Here, we report the TE properties of metal oxide superlattices, composed from alternating layers of 5% Pr3+-doped SrTiO3-δ (SPTO) and 20% Nb5+-doped SrTiO3-δ (STNO) fabricated using pulsed laser deposition (PLD). Excellent stability is established for these superlattices by maintaining the crystal structure and reproducing the TE properties after long-time (20 h) annealing at high temperature (∼1000 K). The introduction of oxygen vacancies as well as extrinsic dopants (Pr3+ and Nb5+), with different masses and ionic radii, at different lattice sites in SPTO and STNO layers, respectively, results in a substantial reduction of thermal conductivity via scattering a wider range of phonon spectrum without limiting the electrical transport and thermopower, leading to an enhancement in the figure-of-merit (ZT). The superlattice composed of 20 SPTO/STNO pairs, 8 unit cells of each layer, exhibits a ZT value of 0.46 at 1000 K, which is the highest among SrTiO3-based thermoelectrics. © 2015 American Chemical Society.

  9. Enhanced thermoelectric figure-of-merit in thermally robust, nanostructured superlattices based on SrTiO3

    KAUST Repository

    Abutaha, Anas I.; Sarath Kumar, S. R.; Li, Kun; Dehkordi, Arash Mehdizadeh; Tritt, Terry M.; Alshareef, Husam N.

    2015-01-01

    Thermoelectric (TE) metal oxides overcome crucial disadvantages of traditional heavy-metal-alloy-based TE materials, such as toxicity, scarcity, and instability at high temperatures. Here, we report the TE properties of metal oxide superlattices, composed from alternating layers of 5% Pr3+-doped SrTiO3-δ (SPTO) and 20% Nb5+-doped SrTiO3-δ (STNO) fabricated using pulsed laser deposition (PLD). Excellent stability is established for these superlattices by maintaining the crystal structure and reproducing the TE properties after long-time (20 h) annealing at high temperature (∼1000 K). The introduction of oxygen vacancies as well as extrinsic dopants (Pr3+ and Nb5+), with different masses and ionic radii, at different lattice sites in SPTO and STNO layers, respectively, results in a substantial reduction of thermal conductivity via scattering a wider range of phonon spectrum without limiting the electrical transport and thermopower, leading to an enhancement in the figure-of-merit (ZT). The superlattice composed of 20 SPTO/STNO pairs, 8 unit cells of each layer, exhibits a ZT value of 0.46 at 1000 K, which is the highest among SrTiO3-based thermoelectrics. © 2015 American Chemical Society.

  10. Effects of SrTiO3 on dielectric and piezoelectric properties of K0.48Na0.48Li0.04Nb0.96Ta0.04O3-based piezoceramics

    International Nuclear Information System (INIS)

    Bafandeh, Mohammad Reza; Abbasi, Mohammad Hasan; Saidi, Ali; Lee, Jae-Shin

    2013-01-01

    Highlights: ► Sodium potassium niobate based piezoceramics modified with SrTiO 3 (ST) were prepared. ► Crystal structure, microstructure and dielectric properties of ceramics were investigated. ► Addition of ST more than 3 mol% changed ferroelectric behavior from normal to relaxor. ► Coexistence of two structures in ceramic with 1 mol% ST enhanced piezoelectric constant. - Abstract: In this study, (100 − x) K 0.48 Na 0.48 Li 0.04 Nb 0.96 Ta 0.04 O 3 − xSrTiO 3 (0 ≤ x ≤ 10) ceramics were fabricated via normal sintering of synthesized powder by using solid state reaction. All ceramics revealed pure perovskite structure, indicating formation of solid solution between KNNLT and ST up to 10%. With increasing x, the crystal structure of ceramics changed from orthorhombic to tetragonal and finally pseudocubic symmetry when x = 10. Ceramic containing 1% ST had orthorhombic and tetragonal symmetries, simultaneously. Investigation of the variation of dielectric constant of ceramics versus temperature revealed that for ceramic with x = 1, polymorphic phase transition (PPT) temperature between orthorhombic and tetragonal is less than room temperature. Thus coexistence of two different structures in this ceramic is due to vicinity of its composition to morphotropic phase boundary (MPB). As a result, the maximum piezoelectric constant was measured for this ceramic. Ceramics containing 5 and 7.5% ST tend to appear relaxor ferroelectric behavior which is because of chemical inhomogeneities in both A- and B-sites of the ABO 3 perovskite structure.

  11. Electronic structure and visible light photocatalysis water splitting property of chromium-doped SrTiO3

    International Nuclear Information System (INIS)

    Liu, J.W.; Chen, G.; Li, Z.H.; Zhang, Z.G.

    2006-01-01

    Cr-doped SrTi 1- x Cr x O 3 (x=0.00, 0.02, 0.05, 0.10) powders, prepared by solvothermal method, were further characterized by ultraviolet-visible (UV-vis) absorption spectroscopy. The UV-vis spectra indicate that the SrTi 1- x Cr x O 3 powders can absorb not only UV light like pure SrTiO 3 powder but also the visible-light spectrum (λ>420 nm). The results of density functional theory (DFT) calculation illuminate that the visible-light absorption bands in the SrTi 1- x Cr x O 3 catalyst are attributed to the band transition from the Cr 3d to the Cr 3d+Ti 3d hybrid orbital. The photocatalytic activities of chromium-doped SrTiO 3 both under UV and visible light are increased with the increase in the amounts of chromium. -- Graphical abstract: SrTi 1- x Cr x O 3 powders, prepared by solvothermal method, can absorb not only UV light like pure SrTiO 3 powder but also the visible-light spectrum (λ>420 nm). The results of DFT calculation illuminate that the visible-light absorption bands in the SrTi 1- x Cr x O 3 catalyst are attributed to the band transition from the Cr 3d to the Cr 3d+Ti 3d hybrid orbital

  12. Thermal Transport and Phonon Hydrodynamics in Strontium Titanate

    Science.gov (United States)

    Martelli, Valentina; Jiménez, Julio Larrea; Continentino, Mucio; Baggio-Saitovitch, Elisa; Behnia, Kamran

    2018-03-01

    We present a study of thermal conductivity, κ , in undoped and doped strontium titanate in a wide temperature range (2-400 K) and detecting different regimes of heat flow. In undoped SrTiO3 , κ evolves faster than cubic with temperature below its peak and in a narrow temperature window. Such behavior, previously observed in a handful of solids, has been attributed to a Poiseuille flow of phonons, expected to arise when momentum-conserving scattering events outweigh momentum-degrading ones. The effect disappears in the presence of dopants. In SrTi1 -xNbx O3 , a significant reduction in lattice thermal conductivity starts below the temperature at which the average inter-dopant distance and the thermal wavelength of acoustic phonons become comparable. In the high-temperature regime, thermal diffusivity becomes proportional to the inverse of temperature, with a prefactor set by sound velocity and Planckian time (τp=(ℏ/kBT ) ).

  13. Gate-tunable polarized phase of two-dimensional electrons at the LaAlO3/SrTiO3 interface.

    Science.gov (United States)

    Joshua, Arjun; Ruhman, Jonathan; Pecker, Sharon; Altman, Ehud; Ilani, Shahal

    2013-06-11

    Controlling the coupling between localized spins and itinerant electrons can lead to exotic magnetic states. A novel system featuring local magnetic moments and extended 2D electrons is the interface between LaAlO3 and SrTiO3. The magnetism of the interface, however, was observed to be insensitive to the presence of these electrons and is believed to arise solely from extrinsic sources like oxygen vacancies and strain. Here we show the existence of unconventional electronic phases in the LaAlO3/SrTiO3 system pointing to an underlying tunable coupling between itinerant electrons and localized moments. Using anisotropic magnetoresistance and anomalous Hall effect measurements in a unique in-plane configuration, we identify two distinct phases in the space of carrier density and magnetic field. At high densities and fields, the electronic system is strongly polarized and shows a response, which is highly anisotropic along the crystalline directions. Surprisingly, below a density-dependent critical field, the polarization and anisotropy vanish whereas the resistivity sharply rises. The unprecedented vanishing of the easy axes below a critical field is in sharp contrast with other coupled magnetic systems and indicates strong coupling with the moments that depends on the symmetry of the itinerant electrons. The observed interplay between the two phases indicates the nature of magnetism at the LaAlO3/SrTiO3 interface as both having an intrinsic origin and being tunable.

  14. Charge transfer mechanism for the formation of metallic states at the KTaO3/SrTiO3 interface

    KAUST Repository

    Nazir, Safdar; Schwingenschlö gl, Udo; Singh, Nirpendra

    2011-01-01

    The electronic and optical properties of the KTaO3/SrTiO3 heterointerface are analyzed by the full-potential linearized augmented plane-wave approach of density functional theory. Optimization of the atomic positions points at subordinate changes

  15. Controlling the Carrier Density of SrTiO3-Based Heterostructures with Annealing

    DEFF Research Database (Denmark)

    Christensen, Dennis Valbjørn; von Soosten, Merlin; Trier, Felix

    2017-01-01

    The conducting interface between the insulating oxides LaAlO3 (LAO) and SrTiO3 (STO) displays numerous physical phenomena that can be tuned by varying the carrier density, which is generally achieved by electrostatic gating or adjustment of growth parameters. Here, it is reported how annealing...... in oxygen at low temperatures (T

  16. Metal-insulator transition at the LaAlO3/SrTiO3 interface revisited: A hybrid functional study

    KAUST Repository

    Cossu, Fabrizio; Eyert, V.; Schwingenschlö gl, Udo

    2013-01-01

    We investigate the electronic properties of the LaAlO3/SrTiO3 interface using density functional theory. In contrast to previous studies, which relied on (semi-)local functionals and the GGA+U method, we here use a recently developed hybrid

  17. Large piezoelectricity in electric-field modified single crystals of SrTiO3

    Science.gov (United States)

    Khanbabaee, B.; Mehner, E.; Richter, C.; Hanzig, J.; Zschornak, M.; Pietsch, U.; Stöcker, H.; Leisegang, T.; Meyer, D. C.; Gorfman, S.

    2016-11-01

    Defect engineering is an effective and powerful tool to control the existing material properties and produce completely new ones, which are symmetry-forbidden in a defect-free crystal. For example, the application of a static electric field to a single crystal of SrTiO3 forms a strained near-surface layer through the migration of oxygen vacancies out of the area beneath the positively charged electrode. While it was previously shown that this near-surface phase holds pyroelectric properties, which are symmetry-forbidden in centrosymmetric bulk SrTiO3, this paper reports that the same phase is strongly piezoelectric. We demonstrate the piezoelectricity of this phase through stroboscopic time-resolved X-ray diffraction under alternating electric field and show that the effective piezoelectric coefficient d33 ranges between 60 and 100 pC/N. The possible atomistic origins of the piezoelectric activity are discussed as a coupling between the electrostrictive effect and spontaneous polarization of this near-surface phase.

  18. Simulating the 3-D Structure of Titan's Upper Atmosphere

    Science.gov (United States)

    Bell, J. M.; Waite, H.; Westlake, J.; Magee, B.

    2009-05-01

    We present results from the 3-D Titan Global Ionosphere-Thermosphere Model (Bell et al [2009], PSS, in review). We show comparisons between simulated N2, CH4, and H2 density fields and the in-situ data from the Cassini Ion Neutral Mass Spectrometer (INMS). We describe the temperature and wind fields consistent with these density calculations. Variations with local time, longitude, and latitude will be addressed. Potential plasma heating sources can be estimated using the 1-D model of De La Haye et al [2007, 2008] and the impacts on the thermosphere of Titan can be assessed in a global sense in Titan-GITM. Lastly, we will place these findings within the context of recent work in modeling the 2-D structure of Titan's upper atmosphere (Mueller-Wodarg et al [2008]).

  19. Performance-Microstructure Relations in Ni/CGO Infiltrated Nb-doped SrTiO3 SOFC Anodes

    DEFF Research Database (Denmark)

    Ramos, Tania; Bernuy-Lopez, Carlos; Reddy Sudireddy, Bhaskar

    2012-01-01

    Nb-doped SrTiO3 solid oxide fuel cell (SOFC) anodes, infiltrated with CGO/Ni, were investigated by electrochemical impedance spectroscopy (EIS) and high resolution microscopy techniques, upon varying production and testing parameters. The electrochemical analysis involved a combination of distrib......Nb-doped SrTiO3 solid oxide fuel cell (SOFC) anodes, infiltrated with CGO/Ni, were investigated by electrochemical impedance spectroscopy (EIS) and high resolution microscopy techniques, upon varying production and testing parameters. The electrochemical analysis involved a combination...... of distribution of relaxation times (DRT) and complex non-linear least squares (CNLS) fitting routine. These electrodes were studied as singlephase or as composites with 8YSZ. Sr0.94Ti0.9Nb0.1O3-δ/ 10 vol.% 8YSZ composite infiltrated electrodes were the best overall performers, with enhanced performance stability...

  20. Evolution of ferromagnetism in two-dimensional electron gas of LaTiO3/SrTiO3

    Science.gov (United States)

    Wen, Fangdi; Cao, Yanwei; Liu, Xiaoran; Pal, B.; Middey, S.; Kareev, M.; Chakhalian, J.

    2018-03-01

    Understanding, creating, and manipulating spin polarization of two-dimensional electron gases at complex oxide interfaces present an experimental challenge. For example, despite almost a decade long research effort, the microscopic origin of ferromagnetism in LaAlO3/SrTiO3 heterojunctions is still an open question. Here, by using a prototypical two-dimensional electron gas (2DEG) which emerges at the interface between band insulator SrTiO3 and antiferromagnetic Mott insulator LaTiO3, the experiment reveals the evidence for magnetic phase separation in a hole-doped Ti d1 t2g system, resulting in spin-polarized 2DEG. The details of electronic and magnetic properties of the 2DEG were investigated by temperature-dependent d.c. transport, angle-dependent X-ray photoemission spectroscopy, and temperature-dependent magnetoresistance. The observation of clear hysteresis in magnetotransport at low magnetic fields implies spin-polarization from magnetic islands in the hole rich LaTiO3 near the interface. These findings emphasize the role of magnetic instabilities in doped Mott insulators, thus providing another path for designing all-oxide structures relevant to spintronic applications.

  1. Three-dimensional self-branching anatase TiO_2 nanorods with the improved carrier collection for SrTiO_3-based perovskite solar cells

    International Nuclear Information System (INIS)

    Hu, Yajing; Wang, Chen; Tang, Ying; Huang, Lu; Fu, Jianxun; Shi, Weimin; Wang, Linjun; Yang, Weiguang

    2016-01-01

    The organic–inorganic perovskite solar cells based on ternary oxide SrTiO_3 shows a higher Voc, attributed to its slightly higher conduction band edge and better morphology of absorber material. However, its less efficient carrier collection and limited overall interfacial areas between the absorber material and the electron-transport layer (ETL), dramatically reducing the Jsc. Here, By adjusting the concentrations of the Ti(OBu)_4, we successfully prepared the three-dimensional (3D) self-branching anatase TiO_2 nanorod/SrTiO_3 nanocomposites, and slightly tuned the particle size of SrTiO_3. With the incorporation of the three-dimensional (3D) self-branching anatase TiO_2 nanorod, the Jsc of the device based on SrTiO_3 was highly boosted. The best performing solar cell we obtained exhibited a PCE of 9.99% with a Jsc of 19.48 mA/cm"2. The excellent performance could be ascribed to the improvement of charge carrier collection of SrTiO_3, better surface coverage and crystallinity of CH_3NH_3PbI_3, and enhanced light scattering ability caused by 3D self-branching anatase TiO_2 nanorods. - Highlights: • The three-dimensional (3D) self-branching anatase TiO_2 nanorod/SrTiO_3 nanocomposites were prepared. • The particle sizes of SrTiO_3 can be slightly tuned. • The best performing solar cell we obtained exhibited a PCE of 9.99% with the Jsc of 19.48 mA/cm"2.

  2. Strain induced atomic structure at the Ir-doped LaAlO3/SrTiO3 interface.

    Science.gov (United States)

    Lee, M; Arras, R; Warot-Fonrose, B; Hungria, T; Lippmaa, M; Daimon, H; Casanove, M J

    2017-11-01

    The structure of Ir-doped LaAlO 3 /SrTiO 3 (001) interfaces was investigated on the atomic scale using probe-corrected transmission electron microscopy in high-angle annular dark-field scanning mode (HAADF-STEM) and electron energy loss spectroscopy (EELS), combined with first-principles calculations. We report the evolution of the strain state experimentally measured in a 5 unit-cell thick LaAlO 3 film as a function of the Ir concentration in the topmost SrTiO 3 layer. It is shown that the LaAlO 3 layers remain fully elastically strained up to 3% of Ir doping, whereas a higher doping level seems to promote strain relaxation through enhanced cationic interdiffusion. The observed differences between the energy loss near edge structure (ELNES) of Ti-L 2,3 and O-K edges at non-doped and Ir-doped interfaces are consistent with the location of the Ir dopants at the interface, up to 3% of Ir doping. These findings, supported by the results of density functional theory (DFT) calculations, provide strong evidence that the effect of dopant concentrations on the properties of this kind of interface should not be analyzed without obtaining essential information from the fine structural and chemical analysis of the grown structures.

  3. EXAFS Study of Disorder in SrTiO3 Perovskite

    International Nuclear Information System (INIS)

    Kodre, Alojz; Arcon, Iztok; Gomilsek, Jana Padeznik; Zalar, Bostjan

    2007-01-01

    Ti K-edge EXAFS spectra of SrTiO3 at room temperature and at N2 boiling point are measured to detect the Ti ion displacement above and below the antiferrodistortive phase transition occurring at Tc = 105 K. The data yield a definite value of the displacement, only slightly dependent on the temperature. The sensitive dependence of the amplitude of Ti-O-Ti focusing paths on the scattering angle is used to infer the correlation of Ti displacements. A preference to alternating displacements is indicated

  4. Anomalous Transport in Sketched Nanostructures at the LaAlO_{3}/SrTiO_{3} Interface

    Directory of Open Access Journals (Sweden)

    Guanglei Cheng

    2013-03-01

    Full Text Available The oxide heterostructure LaAlO_{3}/SrTiO_{3} supports a two-dimensional electron liquid with a variety of competing phases, including magnetism, superconductivity, and weak antilocalization because of Rashba spin-orbit coupling. Further confinement of this two-dimensional electron liquid to the quasi-one-dimensional regime can provide insight into the underlying physics of this system and reveal new behavior. Here, we describe magnetotransport experiments on narrow LaAlO_{3}/SrTiO_{3} structures created by a conductive atomic force microscope lithography technique. Four-terminal local-transport measurements on Hall bar structures about 10 nm wide yield longitudinal resistances that are comparable to the resistance quantum h/e^{2} and independent of the channel length. Large nonlocal resistances (as large as 10^{4}  Ω are observed in some but not all structures with separations between current and voltage that are large compared to the two-dimensional mean-free path. The nonlocal transport is strongly suppressed by the onset of superconductivity below about 200 mK. The origin of these anomalous transport signatures is not understood, but may arise from coherent transport defined by strong spin-orbit coupling and/or magnetic interactions.

  5. Quasistatic antiferromagnetism in the quantum wells of SmTiO3/SrTiO3 heterostructures

    Science.gov (United States)

    Need, Ryan F.; Marshall, Patrick B.; Kenney, Eric; Suter, Andreas; Prokscha, Thomas; Salman, Zaher; Kirby, Brian J.; Stemmer, Susanne; Graf, Michael J.; Wilson, Stephen D.

    2018-03-01

    High carrier density quantum wells embedded within a Mott insulating matrix present a rich arena for exploring unconventional electronic phase behavior ranging from non-Fermi-liquid transport and signatures of quantum criticality to pseudogap formation. Probing the proposed connection between unconventional magnetotransport and incipient electronic order within these quantum wells has however remained an enduring challenge due to the ultra-thin layer thicknesses required. Here we address this challenge by exploring the magnetic properties of high-density SrTiO3 quantum wells embedded within the antiferromagnetic Mott insulator SmTiO3 via muon spin relaxation and polarized neutron reflectometry measurements. The one electron per planar unit cell acquired by the nominal d0 band insulator SrTiO3 when embedded within a d1 Mott SmTiO3 matrix exhibits slow magnetic fluctuations that begin to freeze into a quasistatic spin state below a critical temperature T*. The appearance of this quasistatic well magnetism coincides with the previously reported opening of a pseudogap in the tunneling spectra of high carrier density wells inside this film architecture. Our data suggest a common origin of the pseudogap phase behavior in this quantum critical oxide heterostructure with those observed in bulk Mott materials close to an antiferromagnetic instability.

  6. Suppression of the two-dimensional electron gas in LaGaO3/SrTiO3 by cation intermixing

    KAUST Repository

    Nazir, S.; Amin, B.; Schwingenschlö gl, Udo

    2013-01-01

    Cation intermixing at the n-type polar LaGaO 3 /SrTiO 3 (001) interface is investigated by first principles calculations. Ti"Ga, Sr"La, and SrTi"LaGa intermixing are studied in comparison to each other, with a focus on the interface stability. We

  7. Evolution of subband structure with gate-tuning at LaAlO3/SrTiO3 interfaces

    Science.gov (United States)

    Tang, Lucas; Smink, Sander; van Heeringen, Linde; Geessinck, Jaap; Rana, Abimanuya; Rastogi, Ankur; Maan, Jan Kees; Brinkman, Alexander; Zeitler, Uli; Hilgenkamp, Hans; McCollam, Alix

    The outstanding characteristic of LaAlO3/SrTiO3 heterostructures is the formation of a high mobility 2D electron gas (2DEG) at the interface. The additional presence of superconductivity, magnetism and large spin-orbit coupling in these systems suggests that strong correlations play an important role in the electronic properties, in contrast to conventional semiconductor-based 2DEGs. Knowledge of the electronic bandstructure, and the interdependence of conduction electron density and properties is therefore essential for our understanding of these materials. We present new results of low temperature transport measurements in a high mobility LaAlO3/SrTiO3-based heterostructure, in magnetic fields up to 33 T. Shubnikov de-Haas oscillations are observed, revealing several subbands with different carrier densities. By application of an electric field in the back gate geometry, the Fermi level is tuned and thus we are able to map the smooth evolution of the subbands and their properties with carrier density. These results are in good agreement with recent theoretical work, such that we can disentangle the complex band structure, and quantify aspects such as Rashba spin-splitting and the mixing of orbital character.

  8. Training effect of exchange bias in La0.67Sr0.33MnO3/SrTiO3 superlattice

    International Nuclear Information System (INIS)

    Zhu, S J; Zhao, B R; Xu, B; Zhu, B Y; Cao, L X; Qiu, X G

    2008-01-01

    The training effect of exchange bias has been observed in the superlattice consisting of ferromagnetic La 0.67 Sr 0.33 MnO 3 and non-magnetic SrTiO 3 layers. The exchange field shows an approximately power-law decrease with an increase in the number of hysteresis loop measurements. The vertical shift of the hysteresis loop reveals the existence of the net uncompensated spins at the interface between the La 0.67 Sr 0.33 MnO 3 and the SrTiO 3 layers. The irreversibility of magnetization measurements gives clear evidence that the interfacial spins will be frozen at low temperature. It is suggested that the frozen uncompensated spins at the interface are responsible for the shift of the hysteresis loop and the training effect of exchange bias might be a result of the relaxation process of those interfacial spins when the superlattice is consecutively field-cycled.

  9. Influence of oxygen pressure and aging on LaAlO3 films grown by pulsed laser deposition on SrTiO3 substrates

    KAUST Repository

    Park, Jihwey

    2014-02-24

    The crystal structures of LaAlO3 films grown by pulsed laser deposition on SrTiO3 substrates at oxygen pressure of 10−3 millibars or 10−5 millibars, where kinetics of ablated species hardly depend on oxygen background pressure, are compared. Our results show that the interface between LaAlO3 and SrTiO3 is sharper when the oxygen pressure is lower. Over time, the formation of various crystalline phases is observed while the crystalline thickness of the LaAlO3 layer remains unchanged. X-ray scattering as well as atomic force microscopy measurements indicate three-dimensional growth of such phases, which appear to be fed from an amorphous capping layer present in as-grown samples.

  10. Experimental studies on 3D printing of barium titanate ceramics for medical applications

    Directory of Open Access Journals (Sweden)

    Schult Mark

    2016-09-01

    Full Text Available The present work deals with the 3D printing of porous barium titanate ceramics. Barium titanate is a biocompatible material with piezoelectric properties. Due to insufficient flowability of the starting material for 3D printing, the barium titanate raw material has been modified in three different ways. Firstly, barium titanate powder has been calcined. Secondly, flow additives have been added to the powder. And thirdly, flow additives have been added to the calcined powder. Finally, a polymer has been added to the three materials and specimens have been printed from these three material mixtures. The 3D printed parts were then sintered at 1320°C. The sintering leads to shrinkage which differs between 29.51–71.53% for the tested material mixtures. The porosity of the parts is beneficial for cell growth which is relevant for future medical applications. The results reported in this study demonstrate the possibility to fabricate porous piezoelectric barium titanate parts with a 3D printer that can be used for medical applications. 3D printed porous barium titanate ceramics can especially be used as scaffold for bone tissue engineering, where the bone formation can be promoted by electrical stimulation.

  11. Titan

    Science.gov (United States)

    Müller-Wodarg, Ingo; Griffith, Caitlin A.; Lellouch, Emmanuel; Cravens, Thomas E.

    2014-03-01

    Introduction I. C. F. Müller-Wodarg, C. A. Griffith, E. Lellouch and T. E. Cravens; Prologue 1: the genesis of Cassini-Huygens W.-H. Ip, T. Owen and D. Gautier; Prologue 2: building a space flight instrument: a P.I.'s perspective M. Tomasko; 1. The origin and evolution of Titan G. Tobie, J. I. Lunine, J. Monteux, O. Mousis and F. Nimmo; 2. Titan's surface geology O. Aharonson, A. G. Hayes, P. O. Hayne, R. M. Lopes, A. Lucas and J. T. Perron; 3. Thermal structure of Titan's troposphere and middle atmosphere F. M. Flasar, R. K. Achterberg and P. J. Schinder; 4. The general circulation of Titan's lower and middle atmosphere S. Lebonnois, F. M. Flasar, T. Tokano and C. E. Newman; 5. The composition of Titan's atmosphere B. Bézard, R. V. Yelle and C. A. Nixon; 6. Storms, clouds, and weather C. A. Griffith, S. Rafkin, P. Rannou and C. P. McKay; 7. Chemistry of Titan's atmosphere V. Vuitton, O. Dutuit, M. A. Smith and N. Balucani; 8. Titan's haze R. West, P. Lavvas, C. Anderson and H. Imanaka; 9. Titan's upper atmosphere: thermal structure, dynamics, and energetics R. V. Yelle and I. C. F. Müller-Wodarg; 10. Titan's upper atmosphere/exosphere, escape processes, and rates D. F. Strobel and J. Cui; 11. Titan's ionosphere M. Galand, A. J. Coates, T. E. Cravens and J.-E. Wahlund; 12. Titan's magnetospheric and plasma environment J.-E. Wahlund, R. Modolo, C. Bertucci and A. J. Coates.

  12. Control of growth mode in SrTiO3 homoepitaxy under 500 deg. C

    International Nuclear Information System (INIS)

    Li Yanrong; Li Jinlong; Zhang Ying; Wei Xianhua; Deng Xinwu; Liu Xingzhao

    2004-01-01

    Homoepitaxial SrTiO 3 thin films were grown by laser molecular beam epitaxy. The growth mode was determined by in-situ reflective high energy electron diffraction, and the surface of the films was studied by ex-situ atomic force microscopy. At the deposition rate of 0.16A ring /sec and the laser energy density of 6J/cm 2 , layer-by-layer growth was observed above 460 deg. C substrate temperature, while the Stranski-Krastanov growth mode, that is layer-by-layer growth plus island growth mode, prevailed between 460 deg. C and 410 deg. C. On further decreasing the substrate temperature, the island growth was determined under 410 deg. C. With the optimization of deposition process in terms of laser energy density and deposition rate, the lowest crystallization temperatures of SrTiO 3 films grown in layer-by-layer growth mode were obtained as low as 280 deg. C. The effects of laser energy density on growth temperature were studied

  13. Digital to analog resistive switching transition induced by graphene buffer layer in strontium titanate based devices.

    Science.gov (United States)

    Wan, Tao; Qu, Bo; Du, Haiwei; Lin, Xi; Lin, Qianru; Wang, Da-Wei; Cazorla, Claudio; Li, Sean; Liu, Sidong; Chu, Dewei

    2018-02-15

    Resistive switching behaviour can be classified into digital and analog switching based on its abrupt and gradual resistance change characteristics. Realizing the transition from digital to analog switching in the same device is essential for understanding and controlling the performance of the devices with various switching mechanisms. Here, we investigate the resistive switching in a device made with strontium titanate (SrTiO 3 ) nanoparticles using X-ray diffractometry, scanning electron microscopy, Raman spectroscopy, and direct electrical measurements. It is found that the well-known rupture/formation of Ag filaments is responsible for the digital switching in the device with Ag as the top electrode. To modulate the switching performance, we insert a reduced graphene oxide layer between SrTiO 3 and the bottom FTO electrode owing to its good barrier property for the diffusion of Ag ions and high out-of-plane resistance. In this case, resistive switching is changed from digital to analog as determined by the modulation of interfacial resistance under applied voltage. Based on that controllable resistance, potentiation and depression behaviours are implemented as well. This study opens up new ways for the design of multifunctional devices which are promising for memory and neuromorphic computing applications. Copyright © 2017 Elsevier Inc. All rights reserved.

  14. SrTiO3 Nanocube-Doped Polyaniline Nanocomposites with Enhanced Photocatalytic Degradation of Methylene Blue under Visible Light

    Directory of Open Access Journals (Sweden)

    Syed Shahabuddin

    2016-02-01

    Full Text Available The present study highlights the facile synthesis of polyaniline (PANI-based nanocomposites doped with SrTiO3 nanocubes synthesized via the in situ oxidative polymerization technique using ammonium persulfate (APS as an oxidant in acidic medium for the photocatalytic degradation of methylene blue dye. Field emission scanning electron microscopy (FESEM, transmission electron microscopy (TEM, thermogravimetric analysis (TGA, X-ray diffraction (XRD, UV–Vis spectroscopy, Brunauer–Emmett–Teller analysis (BET and Fourier transform infrared spectroscopy (FTIR measurements were used to characterize the prepared nanocomposite photocatalysts. The photocatalytic efficiencies of the photocatalysts were examined by degrading methylene blue (MB under visible light irradiation. The results showed that the degradation efficiency of the composite photocatalysts that were doped with SrTiO3 nanocubes was higher than that of the undoped polyaniline. In this study, the effects of the weight ratio of polyaniline to SrTiO3 on the photocatalytic activities were investigated. The results revealed that the nanocomposite P-Sr500 was found to be an optimum photocatalyst, with a 97% degradation efficiency after 90 min of irradiation under solar light.

  15. A versatile light-switchable nanorod memory: Wurtzite ZnO on perovskite SrTiO3

    KAUST Repository

    Kumar, Anup Bera; Peng, Haiyang; Lourembam, James; Shen, Youde; Sun, Xiaowei; Wu, Tao

    2013-01-01

    heterojunction memory made of wurtzite ZnO nanorods grown on perovskite Nb-doped SrTiO3 (NSTO) is reported, the electronic properties of which can be drastically reconfigured by applying a voltage and light. Despite of the distinct lattice structures of Zn

  16. Octahedral rotations in strained LaAlO3/SrTiO3 (001 heterostructures

    Directory of Open Access Journals (Sweden)

    T. T. Fister

    2014-02-01

    Full Text Available Many complex oxides display an array of structural instabilities often tied to altered electronic behavior. For oxide heterostructures, several different interfacial effects can dramatically change the nature of these instabilities. Here, we investigate LaAlO3/SrTiO3 (001 heterostructures using synchrotron x-ray scattering. We find that when cooling from high temperature, LaAlO3 transforms from the Pm3¯m to the Imma phase due to strain. Furthermore, the first 4 unit cells of the film adjacent to the substrate exhibit a gradient in rotation angle that can couple with polar displacements in films thinner than that necessary for 2D electron gas formation.

  17. New insights on the synthesis and electronic transport in bulk polycrystalline Pr-doped SrTiO3−δ

    International Nuclear Information System (INIS)

    Dehkordi, Arash Mehdizadeh; Bhattacharya, Sriparna; Darroudi, Taghi; Alshareef, Husam N.; Tritt, Terry M.

    2015-01-01

    Recently, we have reported a significant enhancement in the electronic and thermoelectric properties of bulk polycrystalline SrTiO 3 ceramics via praseodymium doping. This improvement was originated from the simultaneous enhancement in the thermoelectric power factor and reduction in thermal conductivity, which was contributed to the non-uniform distribution of Pr dopants. In order to further understand the underlying mechanism, we herein investigate the role of praseodymium doping source (Pr 2 O 3 versus Pr 6 O 11 ) on the synthesis and electronic transport in Pr-doped SrTiO 3 ceramics. It was observed that the high-temperature electronic transport properties are independent of the choice of praseodymium doping source for samples prepared following our synthesis strategy. Theoretical calculations were also performed in order to estimate the maximum achievable power factor and the corresponding optimal carrier concentration. The result suggests the possibility of further improvement of the power factor. This study should shed some light on the superior electronic transport in bulk polycrystalline Pr-doped SrTiO 3 ceramics and provide new insight on further improvement of the thermoelectric power factor

  18. New insights on the synthesis and electronic transport in bulk polycrystalline Pr-doped SrTiO3−δ

    KAUST Repository

    Dehkordi, Arash Mehdizadeh

    2015-02-07

    Recently, we have reported a significant enhancement in the electronic and thermoelectric properties of bulk polycrystalline SrTiO3 ceramics via praseodymium doping. This improvement was originated from the simultaneous enhancement in the thermoelectric power factor and reduction in thermal conductivity, which was contributed to the non-uniform distribution of Pr dopants. In order to further understand the underlying mechanism, we herein investigate the role of praseodymium doping source (Pr2O3 versus Pr6O11) on the synthesis and electronic transport in Pr-doped SrTiO3 ceramics. It was observed that the high-temperature electronic transport properties are independent of the choice of praseodymium doping source for samples prepared following our synthesis strategy. Theoretical calculations were also performed in order to estimate the maximum achievable power factor and the corresponding optimal carrier concentration. The result suggests the possibility of further improvement of the power factor. This study should shed some light on the superior electronic transport in bulk polycrystalline Pr-doped SrTiO3 ceramics and provide new insight on further improvement of the thermoelectric power factor.

  19. Nonlinear acoustic effects in the propagation of surface acoustic waves in SrTiO3 near the structural phase transition

    International Nuclear Information System (INIS)

    Balashova, E.V.; Lemanov, V.V.; Sherman, A.B.

    1986-01-01

    Generation process of a surface acoustic wave with summarized frequency in collinear propagation of two surface acoustic waves in SrTiO 3 crystal near crystal-phase transition O n → D 4h (T c ≅ 105 K) is investigated. Anomalous increase of a nonlinear parameter Γ ∼ (T-T c ) -1 attributed to a fluctuation mechanism is observed. It is shown that the presence of a surface layer in SrTiO 3 having a higher, than in crystal volume, temperature of phase transition results in summarized frequency signal oscillation

  20. Appearance and disappearance of ferromagnetism in ultrathin LaMnO3 on SrTiO3 substrate: A viewpoint from first principles

    Science.gov (United States)

    An, Ming; Weng, Yakui; Zhang, Huimin; Zhang, Jun-Jie; Zhang, Yang; Dong, Shuai

    2017-12-01

    The intrinsic magnetic state (ferromagnetic or antiferromagnetic) of ultrathin LaMnO3 films on the most commonly used SrTiO3 substrate is a long-existing question under debate. Either strain effect or nonstoichiometry was argued to be responsible for the experimental ferromagnetism. In a recent experiment [X. R. Wang, C. J. Li, W. M. Lü, T. R. Paudel, D. P. Leusink, M. Hoek, N. Poccia, A. Vailionis, T. Venkatesan, J. M. D. Coey, E. Y. Tsymbal, Ariando, and H. Hilgenkamp, Science 349, 716 (2015), 10.1126/science.aaa5198], one more mechanism, namely, the self-doping due to polar discontinuity, was argued to be the driving force of ferromagnetism beyond the critical thickness. Here systematic first-principles calculations have been performed to check these mechanisms in ultrathin LaMnO3 films as well as superlattices. Starting from the very precise descriptions of both LaMnO3 and SrTiO3, it is found that the compressive strain is the dominant force for the appearance of ferromagnetism, while the open surface with oxygen vacancies leads to the suppression of ferromagnetism. Within LaMnO3 layers, the charge reconstructions involve many competitive factors and certainly go beyond the intuitive polar catastrophe model established for LaAlO3/SrTiO3 heterostructures. Our paper not only explains the long-term puzzle regarding the magnetism of ultrathin LaMnO3 films but also sheds light on how to overcome the notorious magnetic dead layer in ultrathin manganites.

  1. Major enhancement of the thermoelectric performance in Pr/Nb-doped SrTiO3 under strain

    KAUST Repository

    Amin, B.

    2013-07-16

    The electronic structure and thermoelectric properties of strained (biaxially and uniaxially) Sr0.95Pr0.05TiO3 and SrTi0.95Nb0.05O3 are investigated in the temperature range from 300 K to 1200 K. Substitutions of Pr at the Sr site and Nb at the Ti site generate n-type doping and thus improve the thermoelectric performance as compared to pristine SrTiO3. Further enhancement is achieved by the application of strain, for example, of the Seebeck coefficient by 21% for Sr0.95Pr0.05TiO3 and 10% for SrTi0.95Nb0.05O3 at room temperature in the case of 5% biaxial strain. At 1200 K, we predict figures of merit of 0.58 and 0.55 for 2.5% biaxially strained Sr0.95Pr0.05TiO3 and SrTi0.95Nb0.05O3 , respectively, which are the highest values reported for rare earth doped SrTiO3.

  2. Hydrogen molecule defect in proton-conductive SrTiO3 Perovskite

    Science.gov (United States)

    Onishi, Taku

    2017-11-01

    In proton-conductive SrTiO3 perovskite, no hydrogen molecule defect ideally exists. However, the unforeseen chemical reaction is often observed after the use of fuel cell. From the viewpoint of battery safety, we have investigated the effect of hydrogen molecule defect by molecular orbital analysis. When counter cation vacancy exists, the activation energy for hydrogen molecule migration was 1.39 - 1.50 eV, which is much smaller than the dissociation energy of hydrogen molecule. It implies that hydrogen molecule may migrate without its dissociation.

  3. Giant Polarization Rotation in BiFeO3/SrTiO3 Thin Films.

    Science.gov (United States)

    Langner, M. C.; Chu, Y. H.; Martin, L. M.; Gajek, M.; Ramesh, R.; Orenstein, J.

    2008-03-01

    We use optical second harmonic generation to probe dynamics of the ferroelectric polarization in (111) oriented BiFeO3 thin films grown on SrTiO3 substrates. The second harmonic response indicates 3m point group symmetry and is consistent with a spontaneous polarization normal to the surface of the film. We measure large changes in amplitude and lowering of symmetry, consistent with polarization rotation, when modest electric fields are applied in the plane of the film. At room temperature the rotation is an order of magnitude larger than expected from reported values of the dielectric constant and increases further (as 1/T) as temperature is lowered. We propose a substrate interaction model to explain these results.

  4. Critical thickness of high structural quality SrTiO3 films grown on orthorhombic (101) DyScO3

    International Nuclear Information System (INIS)

    Biegalski, M. D.; Trolier-McKinstry, S.; Schlom, D. G.; Fong, D. D.; Eastman, J. A.; Fuoss, P. H.; Streiffer, S. K.; Heeg, T.; Schubert, J.; Tian, W.; Nelson, C. T.; Pan, X. Q.; Hawley, M. E.; Bernhagen, M.; Reiche, P.; Uecker, R.

    2008-01-01

    Strained epitaxial SrTiO 3 films were grown on orthorhombic (101) DyScO 3 substrates by reactive molecular-beam epitaxy. The epitaxy of this substrate/film combination is cube on cube with a pseudocubic out-of-plane (001) orientation. The strain state and structural perfection of films with thicknesses ranging from 50 to 1000 A were examined using x-ray scattering. The critical thickness at which misfit dislocations was introduced was between 350 and 500 A. These films have the narrowest rocking curves (full width at half maximum) ever reported for any heteroepitaxial oxide film (0.0018 deg.). Only a modest amount of relaxation is seen in films exceeding the critical thicknesses even after postdeposition annealing at 700 deg. C in 1 atm of oxygen. The dependence of strain relaxation on crystallographic direction is attributed to the anisotropy of the substrate. These SrTiO 3 films show structural quality more typical of semiconductors such as GaAs and silicon than perovskite materials; their structural relaxation behavior also shows similarity to that of compound semiconductor films

  5. Interface structure and electronic properties of SrTiO3 and YBa2Cu3O7-δ crystals and thin films

    International Nuclear Information System (INIS)

    Thiess, S.

    2007-01-01

    Two new extensions of the X-ray standing wave (XSW) technique, made possible by the intense highly collimated X-ray beams from undulators at the ESRF, are described in this thesis. First, the XSW method was applied in a structural study to solve the nucleation mechanism of the high temperature superconductor YBa 2 Cu 3 O 7-δ on the (001) surface of SrTiO 3 . Second, the valence electronic structures of SrTiO 3 and YBa 2 Cu 3 O 7-δ were investigated. Finally, recent developments in the field of photoelectron spectroscopy in the hard X-ray region are described. The X-ray standing wave method is used in combination with fluorescence, Auger or photoelectron spectroscopy and lends very high spatial resolution power to these analytical techniques. Previously, the XSW method has been used for structure determination of surfaces and interfaces. The currently available X-ray intensities permit extensions to the XSW technique. Two recently established applications, described in this thesis, are XSW real space imaging and XSW valence electronic structure analysis. XSW real space imaging was employed to analyse the atomic structure of 0.5 and 1.0 layers of YBa 2 Cu 3 O 7-δ deposited on SrTiO 3 (001). Three-dimensional images of the atomic distributions were reconstructed for each of the elements from experimentally determined Fourier components of the atomic distribution functions. The images confirmed the formation of a perovskite precursor phase prior to the formation of the YBa 2 Cu 3 O 7-δ phase during the growth of the first monolayer of the film. XSW valence electronic structure analysis applied to SrTiO 3 identified the valence band contributions arising from the strontium, titanium, and oxygen sites of the crystal lattice. Relations between the site-specific valence electronic structure and the lattice structure were established. The experimental results agree very well with predictions by state-of-the-art ab initio calculations. X-ray absorption cross sections for

  6. Plasma environment of Titan: a 3-D hybrid simulation study

    Directory of Open Access Journals (Sweden)

    S. Simon

    2006-05-01

    Full Text Available Titan possesses a dense atmosphere, consisting mainly of molecular nitrogen. Titan's orbit is located within the Saturnian magnetosphere most of the time, where the corotating plasma flow is super-Alfvénic, yet subsonic and submagnetosonic. Since Titan does not possess a significant intrinsic magnetic field, the incident plasma interacts directly with the atmosphere and ionosphere. Due to the characteristic length scales of the interaction region being comparable to the ion gyroradii in the vicinity of Titan, magnetohydrodynamic models can only offer a rough description of Titan's interaction with the corotating magnetospheric plasma flow. For this reason, Titan's plasma environment has been studied by using a 3-D hybrid simulation code, treating the electrons as a massless, charge-neutralizing fluid, whereas a completely kinetic approach is used to cover ion dynamics. The calculations are performed on a curvilinear simulation grid which is adapted to the spherical geometry of the obstacle. In the model, Titan's dayside ionosphere is mainly generated by solar UV radiation; hence, the local ion production rate depends on the solar zenith angle. Because the Titan interaction features the possibility of having the densest ionosphere located on a face not aligned with the ram flow of the magnetospheric plasma, a variety of different scenarios can be studied. The simulations show the formation of a strong magnetic draping pattern and an extended pick-up region, being highly asymmetric with respect to the direction of the convective electric field. In general, the mechanism giving rise to these structures exhibits similarities to the interaction of the ionospheres of Mars and Venus with the supersonic solar wind. The simulation results are in agreement with data from recent Cassini flybys.

  7. Plasma environment of Titan: a 3-D hybrid simulation study

    Directory of Open Access Journals (Sweden)

    S. Simon

    2006-05-01

    Full Text Available Titan possesses a dense atmosphere, consisting mainly of molecular nitrogen. Titan's orbit is located within the Saturnian magnetosphere most of the time, where the corotating plasma flow is super-Alfvénic, yet subsonic and submagnetosonic. Since Titan does not possess a significant intrinsic magnetic field, the incident plasma interacts directly with the atmosphere and ionosphere. Due to the characteristic length scales of the interaction region being comparable to the ion gyroradii in the vicinity of Titan, magnetohydrodynamic models can only offer a rough description of Titan's interaction with the corotating magnetospheric plasma flow. For this reason, Titan's plasma environment has been studied by using a 3-D hybrid simulation code, treating the electrons as a massless, charge-neutralizing fluid, whereas a completely kinetic approach is used to cover ion dynamics. The calculations are performed on a curvilinear simulation grid which is adapted to the spherical geometry of the obstacle. In the model, Titan's dayside ionosphere is mainly generated by solar UV radiation; hence, the local ion production rate depends on the solar zenith angle. Because the Titan interaction features the possibility of having the densest ionosphere located on a face not aligned with the ram flow of the magnetospheric plasma, a variety of different scenarios can be studied. The simulations show the formation of a strong magnetic draping pattern and an extended pick-up region, being highly asymmetric with respect to the direction of the convective electric field. In general, the mechanism giving rise to these structures exhibits similarities to the interaction of the ionospheres of Mars and Venus with the supersonic solar wind. The simulation results are in agreement with data from recent Cassini flybys.

  8. Tuning the electronic structure of SrTiO3/SrFeO3−x superlattices via composition and vacancy control

    Directory of Open Access Journals (Sweden)

    Robert F. Berger

    2014-04-01

    Full Text Available Using density functional theory-based calculations, we explore the effects of oxygen vacancies and epitaxial layering on the atomic, magnetic, and electronic structure of (SrTiO3n(SrFeO3−x1 superlattices. While structures without oxygen vacancies (x = 0 possess small or non-existent band gaps and ferromagnetic ordering in their iron layers, those with large vacancy concentrations (x = 0.5 have much larger gaps and antiferromagnetic ordering. Though the computed gaps depend numerically on the delicate energetic balance of vacancy ordering and on the value of Hubbard U eff used in the calculations, we demonstrate that changes in layering can tune the band gaps of these superlattices below that of SrTiO3 (3.2 eV by raising their valence band maxima. This suggests the possibility that these superlattices could absorb in the solar spectrum, and could serve as water-splitting photocatalysts.

  9. Nonmonotonic anisotropy in charge conduction induced by antiferrodistortive transition in metallic SrTiO3

    Science.gov (United States)

    Tao, Qian; Loret, Bastien; Xu, Bin; Yang, Xiaojun; Rischau, Carl Willem; Lin, Xiao; Fauqué, Benoît; Verstraete, Matthieu J.; Behnia, Kamran

    2016-07-01

    Cubic SrTiO3 becomes tetragonal below 105 K. The antiferrodistortive (AFD) distortion leads to clockwise and counterclockwise rotation of adjacent TiO6 octahedra. This insulator becomes a metal upon the introduction of extremely low concentration of n -type dopants. However, signatures of the structural phase transition in charge conduction have remained elusive. Employing the Montgomery technique, we succeed in resolving the anisotropy of charge conductivity induced by the AFD transition, in the presence of different types of dopants. We find that the slight lattice distortion (liquids, the anisotropy has opposite signs for elastic and inelastic scattering. Increasing the concentration of dopants leads to a drastic shift in the temperature of the AFD transition either upward or downward. The latter result puts strong constraints on any hypothetical role played by the AFD soft mode in the formation of Cooper pairs and the emergence of superconductivity in SrTiO3.

  10. The dynamics of ultraviolet-induced oxygen vacancy at the surface of insulating SrTiO_3(0 0 1)

    International Nuclear Information System (INIS)

    Suwanwong, S.; Eknapakul, T.; Rattanachai, Y.; Masingboon, C.; Rattanasuporn, S.; Phatthanakun, R.; Nakajima, H.; King, P.D.C.; Hodak, S.K.; Meevasana, W.

    2015-01-01

    Highlights: • The dynamics of UV-induced oxygen vacancy is studied from the change of surface resistance. • The formation of 2DEG at the insulating surface of SrTiO_3 is confirmed by ARPES. • The UV-induced change in resistance responds differently to oxygen/gas exposure. • The behavior of resistance recovery suggests an alternative method of low-pressure sensing. - Abstract: The effect of ultra-violet (UV) irradiation on the electronic structure and the surface resistance of an insulating SrTiO_3(0 0 1) crystal is studied in this work. Upon UV irradiation, we show that the two-dimensional electron gas (2DEG) emerges at the insulating SrTiO_3 surface and there is a pronounced change in the surface resistance. By combining the observations of the change in valance band and the resistance change under different environments of gas pressure and gas species, we find that UV-induced oxygen vacancies at the surface plays a major role in the resistance change. The dynamic of the resistance change at different oxygen pressures also suggests an alternative method of low-pressure sensing.

  11. Transport and magnetoresistance effect in an oxygen-deficient SrTiO3/La0.67Sr0.33MnO3 heterojunction

    International Nuclear Information System (INIS)

    Wang Jing; Chen Chang-Le; Yang Shi-Hai; Luo Bing-Cheng; Duan Meng-Meng; Jin Ke-Xin

    2013-01-01

    An oxygen-deficient SrTiO 3 /La 0.67 Sr 0.33 MnO 3 heterojunction is fabricated on an SrTiO 3 (001) substrate by a pulsed laser deposition method. The electrical characteristics of the heterojunction are studied systematically in a temperature range from 80 K to 300 K. The transport mechanism follows I ∞ exp(eV/nkT) under small forward bias, while it becomes space charge limited and follows I ∞ V m(T) with 1.49 < m < 1.99 under high bias. Such a heterojunction also exhibits magnetoresistance (MR) effect. The absolute value of negative MR monotonically increases with temperature decreasing and reaches 26.7% at 80 K under H = 0.7 T. Various factors, such as strain and oxygen deficiency play dominant roles in the characteristics. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  12. Major enhancement of the thermoelectric performance in Pr/Nb-doped SrTiO3 under strain

    KAUST Repository

    Amin, B.; Alshareef, Husam N.; Schwingenschlö gl, Udo; Singh, Nirpendra; Tritt, T. M.

    2013-01-01

    site generate n-type doping and thus improve the thermoelectric performance as compared to pristine SrTiO3. Further enhancement is achieved by the application of strain, for example, of the Seebeck coefficient by 21% for Sr0.95Pr0.05TiO3 and 10% for Sr

  13. Reactive Coevaporation Synthesis and Characterization of SrTiO3 Thin Films

    Science.gov (United States)

    Yamaguchi, Hiromu; Matsubara, Shogo; Miyasaka, Yoichi

    1991-09-01

    SrTiO3 thin films were prepared by the reactive coevaporation method, where the Ti and Sr metals were evaporated in oxygen ambient with an E-gun and K-cell, respectively. A uniform depth profile in composition was achieved by altering the Ti evaporation rate according to the Sr evaporation rate change. A typical dielectric constant of 170 was measured on films of 75 nm in thickness. The in-situ annealing in oxygen plasma reduced the leakage current.

  14. Thermoelectric performance enhancement of SrTiO3 by Pr doping

    KAUST Repository

    Kahaly, M. Upadhyay; Schwingenschlö gl, Udo

    2014-01-01

    We investigate Pr doping at the Sr site as a possible route to enhance the thermoelectric behavior of SrTiO3-based materials, using first principles calculations in full-potential density functional theory. The effects of the Pr dopant on the local electronic structure and resulting transport properties are compared to common Nb doping. We demonstrate a substantial enhancement of the thermoelectric figure of merit and develop an explanation for the positive effects, which opens new ways for materials optimization by substitutional doping at the perovskite B site. © 2014 the Partner Organisations.

  15. Linear thermal expansion of SrTiO3

    International Nuclear Information System (INIS)

    Tsunekawa, S.; Watanabe, H.F.J.; Takei, H.

    1984-01-01

    The linear thermal expansion of SrTiO 3 in the temperature range 10 to 150 K is measured with a relative accuracy of 5 x 10 -7 by using a three-terminal capacitance dilatometer. The dilation ΔL/L of a single-domain crystal is converted to the ratio of the pseudo-cubic cell constants a(T)/a(T/sub a/) by the equation a(T)/a(T/sub a/) = [1 + (ΔL/L)/sub T/]/[1 + (ΔL/L)/sub T//sub a/], where L is the specimen length, T/sub a/ is the cubic-to-tetragonal transition temperature and T 6 octahedra around the [001] axis. The temperature at which the dilation shows a minimum, 37.5 K, is very close to the transition point T/sub c/ = (32 +- 5) K predicted by Cowley. (author)

  16. Enhanced carrier density in Nb-doped SrTiO3 thermoelectrics

    KAUST Repository

    Ozdogan, K.

    2012-03-08

    We study epitaxial SrTiO3 interfaced with Nb-doped SrTi1-x Nb x O3 (x = 0, 0.125, 0.25, 0.375, and 0.5) by full-potential density functional theory. From the electronic band structures obtained by our ab-initio calculations we determine the dependence of the induced metallicity on the Nb concentration. We obtain a monotonous increase of the carrier density with the Nb concentration. The results are confirmed by experiments for SrTi0.88Nb0.12O3 and SrTi0.8Nb0.2O3, demonstrating the predictive power and limitations of our theoretical approach. We also show that the Seebeck coefficient decreases monotonously with increasing temperature.

  17. Enhanced carrier density in Nb-doped SrTiO3 thermoelectrics

    KAUST Repository

    Ozdogan, K.; Upadhyay Kahaly, M.; Sarath Kumar, S. R.; Alshareef, Husam N.; Schwingenschlö gl, Udo

    2012-01-01

    We study epitaxial SrTiO3 interfaced with Nb-doped SrTi1-x Nb x O3 (x = 0, 0.125, 0.25, 0.375, and 0.5) by full-potential density functional theory. From the electronic band structures obtained by our ab-initio calculations we determine the dependence of the induced metallicity on the Nb concentration. We obtain a monotonous increase of the carrier density with the Nb concentration. The results are confirmed by experiments for SrTi0.88Nb0.12O3 and SrTi0.8Nb0.2O3, demonstrating the predictive power and limitations of our theoretical approach. We also show that the Seebeck coefficient decreases monotonously with increasing temperature.

  18. Quantification of flexoelectricity in PbTiO3/SrTiO3 superlattice polar vortices using machine learning and phase-field modeling.

    Science.gov (United States)

    Li, Q; Nelson, C T; Hsu, S-L; Damodaran, A R; Li, L-L; Yadav, A K; McCarter, M; Martin, L W; Ramesh, R; Kalinin, S V

    2017-11-13

    Flexoelectricity refers to electric polarization generated by heterogeneous mechanical strains, namely strain gradients, in materials of arbitrary crystal symmetries. Despite more than 50 years of work on this effect, an accurate identification of its coupling strength remains an experimental challenge for most materials, which impedes its wide recognition. Here, we show the presence of flexoelectricity in the recently discovered polar vortices in PbTiO 3 /SrTiO 3 superlattices based on a combination of machine-learning analysis of the atomic-scale electron microscopy imaging data and phenomenological phase-field modeling. By scrutinizing the influence of flexocoupling on the global vortex structure, we match theory and experiment using computer vision methodologies to determine the flexoelectric coefficients for PbTiO 3 and SrTiO 3 . Our findings highlight the inherent, nontrivial role of flexoelectricity in the generation of emergent complex polarization morphologies and demonstrate a viable approach to delineating this effect, conducive to the deeper exploration of both topics.

  19. 2D Electron Gas with 100% Spin-Polarization in the (LaMnO3)2/(SrTiO3)2 Superlattice under Uniaxial Strain

    KAUST Repository

    Cossu, Fabrizio

    2014-07-28

    By first-principles calculations we investigate the structural, electronic, and magnetic properties of the (LaMnO3)2/(SrTiO3)2 superlattice. We find that a monoclinic C2h symmetry is energetically favorable and that the spins order ferromagnetically. Under both compressive and tensile uniaxial strain the electronic structure of the superlattice shows a half-metallic character. In particular, a fully spin-polarized two-dimensional electron gas, which traces back to the Ti 3dxy orbitals, is achieved under compressive uniaxial strain. The (LaMnO3)2/(SrTiO3)2 superlattice is analysed with respect to its structure, magnetism, and electronic properties. Our results demonstrate that uniaxial strain in an experimentally accessible range, both tensile and compressive, can be used to induce half-metallicity. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Influence of oxygen pressure and aging on LaAlO3 films grown by pulsed laser deposition on SrTiO3 substrates

    KAUST Repository

    Park, Jihwey; Soh, Yeong-Ah; Aeppli, Gabriel; David, Adrian; Lin, Weinan; Wu, Tao

    2014-01-01

    The crystal structures of LaAlO3 films grown by pulsed laser deposition on SrTiO3 substrates at oxygen pressure of 10−3 millibars or 10−5 millibars, where kinetics of ablated species hardly depend on oxygen background pressure, are compared. Our

  1. Suppressed carrier density for the patterned high mobility two-dimensional electron gas at γ-Al2O3/SrTiO3 heterointerfaces

    DEFF Research Database (Denmark)

    Niu, Wei; Gan, Yulin; Christensen, Dennis Valbjørn

    2017-01-01

    The two-dimensional electron gas (2DEG) at the non-isostructural interface between spinel γ-Al2O3 and perovskite SrTiO3 is featured by a record electron mobility among complex oxide interfaces in addition to a high carrier density up to the order of 1015 cm-2. Herein, we report on the patterning...... is found to be approximately 3×1013 cm-2, much lower than that of the unpatterned sample (~1015 cm-2). Remarkably, a high electron mobility of approximately 3,600 cm2V-1s-1 was obtained at low temperatures for the patterned 2DEG at a carrier density of ~ 7×1012 cm-2, which exhibits clear Shubnikov-de Hass...... quantum oscillations. The patterned high-mobility 2DEG at the γ-Al2O3/SrTiO3 interface paves the way for the design and application of spinel/perovskite interfaces for high-mobility all-oxide electronic devic...

  2. Interfacial B-site atomic configuration in polar (111) and non-polar (001) SrIrO3/SrTiO3 heterostructures

    Science.gov (United States)

    Anderson, T. J.; Zhou, H.; Xie, L.; Podkaminer, J. P.; Patzner, J. J.; Ryu, S.; Pan, X. Q.; Eom, C. B.

    2017-09-01

    The precise control of interfacial atomic arrangement in ABO3 perovskite heterostructures is paramount, particularly in cases where the subsequent electronic properties of the material exhibit geometrical preferences along polar crystallographic directions that feature inevitably complex surface reconstructions. Here, we present the B-site interfacial structure in polar (111) and non-polar (001) SrIrO3/SrTiO3 interfaces. The heterostructures were examined using scanning transmission electron microscopy and synchrotron-based coherent Bragg rod analysis. Our results reveal the preference of B-site intermixing across the (111) interface due to the polarity-compensated SrTiO3 substrate surface prior to growth. By comparison, the intermixing at the non-polar (001) interface is negligible. This finding suggests that the intermixing may be necessary to mitigate epitaxy along heavily reconstructed and non-stoichiometric (111) perovskite surfaces. Furthermore, this preferential B-site configuration could allow the geometric design of the interfacial perovskite structure and chemistry to selectively engineer the correlated electronic states of the B-site d-orbital.

  3. Interfacial B-site atomic configuration in polar (111 and non-polar (001 SrIrO3/SrTiO3 heterostructures

    Directory of Open Access Journals (Sweden)

    T. J. Anderson

    2017-09-01

    Full Text Available The precise control of interfacial atomic arrangement in ABO3 perovskite heterostructures is paramount, particularly in cases where the subsequent electronic properties of the material exhibit geometrical preferences along polar crystallographic directions that feature inevitably complex surface reconstructions. Here, we present the B-site interfacial structure in polar (111 and non-polar (001 SrIrO3/SrTiO3 interfaces. The heterostructures were examined using scanning transmission electron microscopy and synchrotron-based coherent Bragg rod analysis. Our results reveal the preference of B-site intermixing across the (111 interface due to the polarity-compensated SrTiO3 substrate surface prior to growth. By comparison, the intermixing at the non-polar (001 interface is negligible. This finding suggests that the intermixing may be necessary to mitigate epitaxy along heavily reconstructed and non-stoichiometric (111 perovskite surfaces. Furthermore, this preferential B-site configuration could allow the geometric design of the interfacial perovskite structure and chemistry to selectively engineer the correlated electronic states of the B-site d-orbital.

  4. Integrated oxygen sensors based on Mg-doped SrTiO3 fabricated by screen-printing

    DEFF Research Database (Denmark)

    Zheng, H.; Toft Sørensen, O.

    1998-01-01

    This paper describes the fabrication and testing of Mg-doped SrTiO3 thick-film oxygen sensors with an integrated Pt heater. The results show that the sensor exhibits a PO2 dependence according to R proportional to PO2-1/4 in the considered PO2 range(2.5 x 10(-5) bar

  5. Strain effects on the spin polarized electron gas in ABO3/SrTiO3 (A = Pr, Nd and B = Al, Ga) heterostructures

    KAUST Repository

    Nazir, Safdar

    2013-04-11

    The spin polarized two dimensional electron gas in the correlated ABO3/SrTiO3 (A = Pr, Nd and B = Al, Ga) heterostructures is investigated by ab-initio calculations using density functional theory. Structural relaxation shows a strong buckling at and near the TiO2 terminated n-type interface (IFs) due to significant TiO6 octahedral distortions. We find in all cases, metallic states in a very narrow region of the SrTiO3, in agreement with experimental results. We demonstrate that the interface magnetism strongly reacts to the magnitude of the lattice strain. The orbital occupations and, hence, the charge carrier density change systematically as a function of the lattice mismatch between the component materials.

  6. Strain effects on the spin polarized electron gas in ABO3/SrTiO3 (A = Pr, Nd and B = Al, Ga) heterostructures

    KAUST Repository

    Nazir, Safdar; Schwingenschlö gl, Udo

    2013-01-01

    The spin polarized two dimensional electron gas in the correlated ABO3/SrTiO3 (A = Pr, Nd and B = Al, Ga) heterostructures is investigated by ab-initio calculations using density functional theory. Structural relaxation shows a strong buckling at and near the TiO2 terminated n-type interface (IFs) due to significant TiO6 octahedral distortions. We find in all cases, metallic states in a very narrow region of the SrTiO3, in agreement with experimental results. We demonstrate that the interface magnetism strongly reacts to the magnitude of the lattice strain. The orbital occupations and, hence, the charge carrier density change systematically as a function of the lattice mismatch between the component materials.

  7. Effect of the out-of-plane stress on the properties of epitaxial SrTiO3 films with nano-pillar array on Si-substrate

    Science.gov (United States)

    Bai, Gang; Xie, Qiyun; Liu, Zhiguo; Wu, Dongmei

    2015-08-01

    A nonlinear thermodynamic formalism has been proposed to calculate the physical properties of the epitaxial SrTiO3 films containing vertical nano-pillar array on Si-substrate. The out-of-plane stress induced by the mismatch between film and nano-pillars provides an effective way to tune the physical properties of ferroelectric SrTiO3 films. Tensile out-of-plane stress raises the phase transition temperature and increases the out-of-plane polarization, but decreases the out-of-plane dielectric constant below Curie temperature, pyroelectric coefficient, and piezoelectric coefficient. These results showed that by properly controlling the out-of-plane stress, the out-of-plane stress induced paraelectric-ferroelectric phase transformation will appear near room temperature. Excellent dielectric, pyroelectric, piezoelectric properties of these SrTiO3 films similar to PZT and other lead-based ferroelectrics can be expected.

  8. Hydrogen impurity in SrTiO3: structure, electronic properties and migration

    International Nuclear Information System (INIS)

    Villamagua, Luis; Barreto, Rafael; Procel, Luis Miguel; Stashans, Arvids

    2007-01-01

    The present paper reports a computational investigation of the geometry and electronic structure as well as the migration of a hydrogen impurity in the cubic SrTiO 3 crystal. The study is done using an approach based on the Hartree-Fock theory and developed for periodic systems. It is found that the H impurity forms the so-called OH group at the equilibrium. Analysis of electron density within the defective region implies the enhancement in covalent chemical bonding. A possible defect migration has been also investigated

  9. Integrated oxygen sensors based on Mg-doped SrTiO3 fabricated by screen-printing

    DEFF Research Database (Denmark)

    Zheng, H.; Sørensen, Ole Toft

    2000-01-01

    This paper describes the fabrication and testing of Mg-doped SrTiO3 thick-film oxygen sensors with an integrated Pt heater. The results show that the sensor exhibits a P-o2 dependence according to R proportional to p(o2)(-1/4) in the considered P-o2 range(2.5 x 10(-5) bar

  10. Topotactic Epitaxy of SrTiO3 Mesocrystal Superstructures with Anisotropic Construction for Efficient Overall Water Splitting.

    Science.gov (United States)

    Zhang, Peng; Ochi, Tomoya; Fujitsuka, Mamoru; Kobori, Yasuhiro; Majima, Tetsuro; Tachikawa, Takashi

    2017-05-02

    The higher-order structures of semiconductor-based photocatalysts play crucial roles in their physicochemical properties for efficient light-to-energy conversion. A novel perovskite SrTiO 3 mesocrystal superstructure with well-defined orientation of assembled cubic nanocrystals was synthesized by topotactic epitaxy from TiO 2 mesocrystals through a facile hydrothermal treatment. The SrTiO 3 mesocrystal exhibits three times the efficiency for the hydrogen evolution of conventional disordered systems in alkaline aqueous solution. It also exhibits a high quantum yield of 6.7 % at 360 nm in overall water splitting and even good durability up to 1 day. Temporal and spatial spectroscopic observations revealed that the synergy of the efficient electron flow along the internal nanocube network and efficient collection at the larger external cubes produces remarkably long-lived charges for enhanced photocatalysis. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Topotactic epitaxy of SrTiO3 mesocrystal superstructures with anisotropic construction for efficient overall water splitting

    International Nuclear Information System (INIS)

    Zhang, Peng; Fujitsuka, Mamoru; Majima, Tetsuro; Ochi, Tomoya; Kobori, Yasuhiro; Tachikawa, Takashi

    2017-01-01

    The higher-order structures of semiconductor-based photocatalysts play crucial roles in their physicochemical properties for efficient light-to-energy conversion. A novel perovskite SrTiO 3 mesocrystal superstructure with well-defined orientation of assembled cubic nanocrystals was synthesized by topotactic epitaxy from TiO 2 mesocrystals through a facile hydrothermal treatment. The SrTiO 3 mesocrystal exhibits three times the efficiency for the hydrogen evolution of conventional disordered systems in alkaline aqueous solution. It also exhibits a high quantum yield of 6.7 % at 360 nm in overall water splitting and even good durability up to 1 day. Temporal and spatial spectroscopic observations revealed that the synergy of the efficient electron flow along the internal nanocube network and efficient collection at the larger external cubes produces remarkably long-lived charges for enhanced photocatalysis. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

  12. Nanoscale strontium titanate photocatalysts for overall water splitting.

    Science.gov (United States)

    Townsend, Troy K; Browning, Nigel D; Osterloh, Frank E

    2012-08-28

    SrTiO(3) (STO) is a large band gap (3.2 eV) semiconductor that catalyzes the overall water splitting reaction under UV light irradiation in the presence of a NiO cocatalyst. As we show here, the reactivity persists in nanoscale particles of the material, although the process is less effective at the nanoscale. To reach these conclusions, Bulk STO, 30 ± 5 nm STO, and 6.5 ± 1 nm STO were synthesized by three different methods, their crystal structures verified with XRD and their morphology observed with HRTEM before and after NiO deposition. In connection with NiO, all samples split water into stoichiometric mixtures of H(2) and O(2), but the activity is decreasing from 28 μmol H(2) g(-1) h(-1) (bulk STO), to 19.4 μmol H(2) g(-1) h(-1) (30 nm STO), and 3.0 μmol H(2) g(-1) h(-1) (6.5 nm STO). The reasons for this decrease are an increase of the water oxidation overpotential for the smaller particles and reduced light absorption due to a quantum size effect. Overall, these findings establish the first nanoscale titanate photocatalyst for overall water splitting.

  13. Thermodynamic and kinetic properties of hydrogen defect pairs in SrTiO3 from density functional theory

    DEFF Research Database (Denmark)

    Bork, Nicolai Christian; Bonanos, Nikolaos; Rossmeisl, Jan

    2011-01-01

    A density functional theory investigation of the thermodynamic and kinetic properties of hydrogen–hydrogen defect interactions in the cubic SrTiO3 perovskite is presented. We find a net attraction between two hydrogen atoms with an optimal separation of ∼2.3 Å. The energy gain is ca. 0.33 eV comp...

  14. Tuning metal-insulator behavior in LaTiO3/SrTiO3 heterostructures integrated directly on Si(100) through control of atomic layer thickness

    Science.gov (United States)

    Ahmadi-Majlan, Kamyar; Chen, Tongjie; Lim, Zheng Hui; Conlin, Patrick; Hensley, Ricky; Chrysler, Matthew; Su, Dong; Chen, Hanghui; Kumah, Divine P.; Ngai, Joseph H.

    2018-05-01

    We present electrical and structural characterization of epitaxial LaTiO3/SrTiO3 heterostructures integrated directly on Si(100). By reducing the thicknesses of the heterostructures, an enhancement in carrier-carrier scattering is observed in the Fermi liquid behavior, followed by a metal to insulator transition in the electrical transport. The insulating behavior is described by activated transport, and its onset occurs near an occupation of 1 electron per Ti site within the SrTiO3, providing evidence for a Mott driven transition. We also discuss the role that structure and gradients in strain could play in enhancing the carrier density. The manipulation of Mott metal-insulator behavior in oxides grown directly on Si opens the pathway to harnessing strongly correlated phenomena in device technologies.

  15. Inhomogeneity at the LaAlO3/SrTiO3 interface

    Science.gov (United States)

    Claeson, T.; Kalabukhov, A.; Gunnarsson, R.; Winkler, D.; Borjesson, J.; Ljustina, N.; Olsson, E.; Popok, V.; Boikov, Yu.; Serenkov, I.; Sakharov, V.

    2010-03-01

    High electrical conductivity has been reported for the interface between two wide-band gap insulators, LaAlO3 (LAO) and SrTiO3 (STO). It occurs above a critical thickness of LAO and can be tuned by an electric field. The conduction has been attributed to i) ``polar catastrophe'' , where the electrostatic charge at the interface is compensated by the transfer of half an electron per unit cell to the interface, ii) oxygen vacancies in the STO, and iii) cation intermixing, which may result in the formation of metallic La1-xSrxTiO3 layer. The relation between microstructure and electrical properties is crucial for understanding the origin of electrical conductivity. We have investigated the interface composition using medium-energy ion spectroscopy, high resolution electron microscopy, and Kelvin probe force microscopy. We find a correlation between cationic intermixing at the interface and electrical properties and inhomogeneities of the interface conductivity that may support a percolation model. Work supported by Swedish VR & KAW, Russian ISTC 3743, EC NANOXIDE

  16. Tunnel and electrostatic coupling in graphene-LaAlO3/SrTiO3 hybrid systems

    Directory of Open Access Journals (Sweden)

    I. Aliaj

    2016-06-01

    Full Text Available We report on the transport properties of hybrid devices obtained by depositing graphene on a LaAlO3/SrTiO3 oxide junction hosting a 4 nm-deep 2-dimensional electron system. At low graphene-oxide inter-layer bias, the two electron systems are electrically isolated, despite their small spatial separation. A very efficient reciprocal gating of the two neighboring 2-dimensional systems is shown. A pronounced rectifying behavior is observed for larger bias values and ascribed to the interplay between electrostatic field-effects and tunneling across the LaAlO3 barrier. The relevance of these results in the context of strongly coupled bilayer systems is discussed.

  17. Fractal formation of a Y-Ba-Cu-O thin film on SrTiO3

    International Nuclear Information System (INIS)

    Chow, L.; Chen, J.; Desai, V.; Sundaram, K.; Arora, S.

    1989-01-01

    Fractal formation has been observed after thermal annealing of the rf-sputtered Y-Ba-Cu-O thin film on SrTiO 3 substrate. Through energy-dispersive x-ray analysis, it was found that the composition of the fractal was YBa 2 Cu 3 O x and the surrounding film composition wasY 2 Ba 2 Cu 3 O x . The fractal dimensions D ranging from 1.26 to 1.65 were obtained using the standard sandbox method with different thresholds

  18. Spin polarized electronic states and spin textures at the surface of oxygen-deficient SrTiO3

    Science.gov (United States)

    Jeschke, Harald O.; Altmeyer, Michaela; Rozenberg, Marcelo; Gabay, Marc; Valenti, Roser

    We investigate the electronic structure and spin texture at the (001) surface of SrTiO3 in the presence of oxygen vacancies by means of ab initio density functional theory (DFT) calculations of slabs. Relativistic non-magnetic DFT calculations exhibit Rashba-like spin winding with a characteristic energy scale ~ 10 meV. However, when surface magnetism on the Ti ions is included, bands become spin-split with an energy difference ~ 100 meV at the Γ point. This energy scale is comparable to the observations in SARPES experiments performed on the two-dimensional electronic states confined near the (001) surface of SrTiO3. We find the spin polarized state to be the ground state of the system, and while magnetism tends to suppress the effects of the relativistic Rashba interaction, signatures of it are still clearly visible in terms of complex spin textures. We gratefully acknowledge financial support from the Deutsche Forschungsgemeinschaft through grants SFB/TR 49 and FOR 1346.

  19. Modification of Ag nanoparticles on the surface of SrTiO3 particles and resultant influence on photoreduction of CO2

    Science.gov (United States)

    Shao, Kunjuan; Wang, Yanjie; Iqbal, Muzaffar; Lin, Lin; Wang, Kai; Zhang, Xuehua; He, Meng; He, Tao

    2018-03-01

    Modification of a wide-bandgap semiconductor with noble metals that can exhibit surface plasmon effect is an effective approach to make it responsive to the visible light. In this work, a series of cubic and all-edge-truncated SrTiO3 with and without thermal pretreatment in air are modified by Ag nanoparticles via photodeposition method. The crystal structure, morphology, loading amount of Ag nanoparticles, and optical properties of the obtained Ag-SrTiO3 nanomaterials are well characterized by powder X-ray diffraction, scanning microscope, transmission electron microscope, energy disperse X-ray spectroscopy, ICP-MS and UV-vis diffuse-reflection spectroscopy. The loading amount and size of the Ag nanoparticles can be controlled to some extent by tuning the photodeposition time via growth-dissolution mechanism. The Ag nanoparticles are inclined to deposit on different locations on the surface of cubic and truncated SrTiO3 with and without thermal pretreatment. The resultant SrTiO3 modified by Ag nanoparticles exhibits visible light activity for photocatalytic reduction of CO2, which is closely related to the oxygen vacancy induced by thermal pretreatment, size and amount of Ag nanoparticles. Accordingly, there is an optimized photodeposition time for the synthesis of the photocatalyst that exhibits the highest photocatalytic activity.

  20. Nanoscale patterning of electronic devices at the amorphous LaAlO3/SrTiO3 oxide interface using an electron sensitive polymer mask

    DEFF Research Database (Denmark)

    Bjorlig, Anders V.; von Soosten, Merlin; Erlandsen, Ricci

    2018-01-01

    A simple approach is presented for designing complex oxide mesoscopic electronic devices based on the conducting interfaces of room temperature grown LaAlO3/SrTiO3 heterostructures. The technique is based entirely on methods known from conventional semiconductor processing technology, and we demo...

  1. Hole localization, migration, and the formation of peroxide anion in perovskite SrTiO3

    Science.gov (United States)

    Chen, Hungru; Umezawa, Naoto

    2014-07-01

    Hybrid density functional calculations are carried out to investigate the behavior of holes in SrTiO3. As in many other oxides, it is shown that a hole tend to localize on one oxygen forming an O- anion with a concomitant lattice distortion; therefore a hole polaron. The calculated emission energy from the recombination of the localized hole and a conduction-band electron is about 2.5 eV, in good agreement with experiments. Therefore the localization of the hole or self-trapping is likely to be responsible for the green photoluminescence at low temperature, which was previously attributed to an unknown defect state. Compared to an electron, the calculated hole polaron mobility is three orders of magnitude lower at room temperature. In addition, two O- anions can bind strongly to form an O22- peroxide anion. No electronic states associated with the O22- peroxide anion are located inside the band gap or close to the band edges, indicating that it is electronically inactive. We suggest that in addition to the oxygen vacancy, the formation of the O22- peroxide anion can be an alternative to compensate acceptor doping in SrTiO3.

  2. Quasiparticle dynamics and spin-orbital texture of the SrTiO3 two-dimensional electron gas.

    Science.gov (United States)

    King, P D C; McKeown Walker, S; Tamai, A; de la Torre, A; Eknapakul, T; Buaphet, P; Mo, S-K; Meevasana, W; Bahramy, M S; Baumberger, F

    2014-02-27

    Two-dimensional electron gases (2DEGs) in SrTiO3 have become model systems for engineering emergent behaviour in complex transition metal oxides. Understanding the collective interactions that enable this, however, has thus far proved elusive. Here we demonstrate that angle-resolved photoemission can directly image the quasiparticle dynamics of the d-electron subband ladder of this complex-oxide 2DEG. Combined with realistic tight-binding supercell calculations, we uncover how quantum confinement and inversion symmetry breaking collectively tune the delicate interplay of charge, spin, orbital and lattice degrees of freedom in this system. We reveal how they lead to pronounced orbital ordering, mediate an orbitally enhanced Rashba splitting with complex subband-dependent spin-orbital textures and markedly change the character of electron-phonon coupling, co-operatively shaping the low-energy electronic structure of the 2DEG. Our results allow for a unified understanding of spectroscopic and transport measurements across different classes of SrTiO3-based 2DEGs, and yield new microscopic insights on their functional properties.

  3. Growing LaAlO3/SrTiO3 interfaces by sputter deposition

    Directory of Open Access Journals (Sweden)

    I. M. Dildar

    2015-06-01

    Full Text Available Sputter deposition of oxide materials in a high-pressure oxygen atmosphere is a well-known technique to produce thin films of perovskite oxides in particular. Also interfaces can be fabricated, which we demonstrated recently by growing LaAlO3 on SrTiO3 substrates and showing that the interface showed the same high degree of epitaxy and atomic order as is made by pulsed laser deposition. However, the high pressure sputtering of oxides is not trivial and number of parameters are needed to be optimized for epitaxial growth. Here we elaborate on the earlier work to show that only a relatively small parameter window exists with respect to oxygen pressure, growth temperature, radiofrequency power supply and target to substrate distance. In particular the sensitivity to oxygen pressure makes it more difficult to vary the oxygen stoichiometry at the interface, yielding it insulating rather than conducting.

  4. Suppression of the two-dimensional electron gas in LaGaO3/SrTiO3 by cation intermixing

    KAUST Repository

    Nazir, S.

    2013-12-03

    Cation intermixing at the n-type polar LaGaO 3 /SrTiO 3 (001) interface is investigated by first principles calculations. Ti"Ga, Sr"La, and SrTi"LaGa intermixing are studied in comparison to each other, with a focus on the interface stability. We demonstrate in which cases intermixing is energetically favorable as compared to a clean interface. A depopulation of the Ti 3d xy orbitals under cation intermixing is found, reflecting a complete suppression of the two-dimensional electron gas present at the clean interface.

  5. Thickness-dependent photovoltaic effects in miscut Nb-doped SrTiO3 single crystals

    International Nuclear Information System (INIS)

    Yue Zengji; Zhao Kun; Zhao Songqing; Lu Zhiqing; Li Xiaoming; Ni Hao; Wang Aijun

    2010-01-01

    The photovoltaic effects of Nb-doped SrTiO 3 single crystals with different thicknesses were investigated under the illumination of ultraviolet pulsed lasers. The peak photovoltage increased and then decreased quickly with the decrease in crystal thickness, and a maximum photovoltage occurred for the 180 μm-thick crystal. The photovoltaic response time decreased monotonically with decreasing crystal thickness. The present results suggested the promising potential of reducing crystal thickness in high sensitivity detectors with fast response.

  6. High charge carrier density at the NaTaO3/SrTiO3 hetero-interface

    KAUST Repository

    Nazir, Safdar

    2011-08-05

    The formation of a (quasi) two-dimensional electron gas between the band insulators NaTaO3 and SrTiO3 is studied by means of the full-potential linearized augmented plane-wave method of density functional theory. Optimization of the atomic positions points to only small changes in the chemical bonding at the interface. Both the p-type (NaO)−/(TiO2)0 and n-type (TaO2)+/(SrO)0 interfaces are found to be metallic with high charge carrier densities. The effects of O vacancies are discussed. Spin-polarized calculations point to the formation of isolated O 2pmagnetic moments, located in the metallic region of the p-type interface.

  7. Deposition barium titanate (BaTiO3) doped lanthanum with chemical solution deposition

    International Nuclear Information System (INIS)

    Iriani, Y.; Nurhadi, N.; Jamaludin, A.

    2016-01-01

    Deposition of Barium Titanate (BaTiO 3 ) thin films used Chemical Solution Deposition (CSD) method and prepared with spin coater. BaTiO 3 is doped with lanthanum, 1%, 2%, and 3%. The thermal process use annealing temperature 900°C and holding time for 3 hours. The result of characterization with x-ray diffraction (XRD) equipment show that the addition of La 3+ doped on Barium Titanate caused the change of angle diffraction.The result of refine with GSAS software shows that lanthanum have been included in the structure of BaTiO 3 . Increasing mol dopant La 3+ cause lattice parameter and crystal volume become smaller. Characterization result using Scanning Electron Microscopy (SEM) equipment show that grain size (grain size) become smaller with increasing mole dopant (x) La 3+ . The result of characterization using Sawyer Tower methods show that all the samples (Barium Titanante and Barium Titanate doped lanthanum) are ferroelectric material. Increasing of mole dopant La 3+ cause smaller coercive field and remanent polarization increases. (paper)

  8. High mobility of the strongly confined hole gas in AgTaO3/SrTiO3

    KAUST Repository

    Nazir, Safdar

    2012-05-18

    A theoretical study of the two-dimensional hole gas at the (AgO)−/(TiO2)0 p-type interface in the AgTaO3/SrTiO3 (001) heterostructure is presented. The Ag 4d states strongly hybridize with the O 2p states and contribute to the hole gas. It is demonstrated that the holes are confined to an ultra thin layer (∼4.9Å) with a considerable carrier density of ∼1014cm−2. We estimate a hole mobility of 18.6 cm2 V−1 s−1, which is high enough to enable device applications.

  9. The metallic interface between the two band insulators LaGaO3 and SrTiO3

    KAUST Repository

    Nazir, Safdar; Schwingenschlö gl, Udo; Singh, Nirpendra

    2011-01-01

    The formation of metallic interface states between the two band insulators LaGaO3 and SrTiO3 is studied by the full-potential linearized augmented plane-wave method based on density functional theory.Structural optimization of the atomic positions points to only small changes of the chemical bonding at the interface. The n-type (LaO/TiO2) and p-type (GaO2/SrO) interfaces turn out to be metallic. Reduction of the O content increases the conductivity of the n-type interface, while the p-type interface can be turned gradually from a hole doped into an electron doped state.

  10. The metallic interface between the two band insulators LaGaO3 and SrTiO3

    KAUST Repository

    Nazir, Safdar

    2011-06-28

    The formation of metallic interface states between the two band insulators LaGaO3 and SrTiO3 is studied by the full-potential linearized augmented plane-wave method based on density functional theory.Structural optimization of the atomic positions points to only small changes of the chemical bonding at the interface. The n-type (LaO/TiO2) and p-type (GaO2/SrO) interfaces turn out to be metallic. Reduction of the O content increases the conductivity of the n-type interface, while the p-type interface can be turned gradually from a hole doped into an electron doped state.

  11. High mobility of the strongly confined hole gas in AgTaO3/SrTiO3

    KAUST Repository

    Nazir, Safdar; Schwingenschlö gl, Udo; Upadhyay Kahaly, M.

    2012-01-01

    A theoretical study of the two-dimensional hole gas at the (AgO)−/(TiO2)0 p-type interface in the AgTaO3/SrTiO3 (001) heterostructure is presented. The Ag 4d states strongly hybridize with the O 2p states and contribute to the hole gas. It is demonstrated that the holes are confined to an ultra thin layer (∼4.9Å) with a considerable carrier density of ∼1014cm−2. We estimate a hole mobility of 18.6 cm2 V−1 s−1, which is high enough to enable device applications.

  12. Highly oriented as-deposited superconducting laser ablated thin films of Y1Ba2Cu3O/sub 7-//sub δ/ on SrTiO3, zirconia, and Si substrates

    International Nuclear Information System (INIS)

    Koren, G.; Polturak, E.; Fisher, B.; Cohen, D.; Kimel, G.

    1988-01-01

    KrF excimer laser ablation of an Y 1 Ba 2 Cu 3 O/sub 7-//sub δ/ pellet in 0.1--0.2 Torr of O 2 ambient was used to deposit thin superconducting films onto SrTiO 3 , yttria-stabilized zirconia (YSZ), and silicon substrates at 600--700 0 C. The as-deposited 1-μm-thick films at 650--700 0 C substrate temperature were superconducting, without further high-temperature annealing. All films had a similar T/sub c/ onset of ∼92 K but different zero-resistance T/sub c/ of 90, 85, and 70 K for the films on SrTiO 3 , YSZ, and Si substrates, respectively. Angular x-ray diffraction analysis showed that all the films were highly oriented with the c axis perpendicular to their surface. Critical current densities at 77 K were about 40 000 and 10 000 A/cm 2 for the films on SrTiO 3 and YSZ, respectively. Smooth surface morphology was observed in all films, with occasional defects and cracks in the films on YSZ, which seems to explain the lower critical current in these films

  13. Explanation for the temperature dependence of plasma frequencies in SrTiO3 using mixed-polaron theory

    International Nuclear Information System (INIS)

    Eagles, D.M.; Georgiev, M.; Petrova, P.C.

    1996-01-01

    A theory of mixed polarons is used to interpret the published experimental results of Gervais et al. on temperature-dependent plasma frequencies in Nb-doped SrTiO 3 . For given polaron masses before mixing, the appropriate average mixed-polaron mass at any temperature T depends on two quantities, δ and b, which are measures of the separation between the bottoms of large and nearly small polaron bands before mixing and of a mixing matrix element; δ and b are assumed to have arbitrary linear dependences on T, probably related to a T dependence of the bare mass, and a term quadratic in T is included in δ, determined from the T dependence of large-polaron binding energies. Including a constraint on the ratio δ/|b| at low T from known masses from specific-heat data, satisfactory agreement is obtained with masses determined from plasma frequencies. This gives further support for the theory of mixed polarons in SrTiO 3 in addition to that already published. copyright 1996 The American Physical Society

  14. Suppression of oxygen diffusion by thin Al2O3 films grown on SrTiO3 studied using a monoenergetic positron beam

    International Nuclear Information System (INIS)

    Uedono, A.; Kiyohara, M.; Yasui, N.; Yamabe, K.

    2005-01-01

    The annealing behaviors of oxygen vacancies introduced by the epitaxial growth of thin SrTiO 3 and Al 2 O 3 films on SrTiO 3 substrates were studied by using a monoenergetic positron beam. The films were grown by molecular-beam epitaxy without using an oxidant. The Doppler broadening spectra of the annihilation radiation were measured as a function of the incident positron energy for samples fabricated under various growth conditions. The line-shape parameter S, corresponding to the annihilation of positrons in the substrate, was increased by the film growth, suggesting diffusion of oxygen from the substrate into the film and a resultant introduction of vacancies (mainly oxygen vacancies). A clear correlation between the value of S and the substrate conductivity was obtained. From isochronal annealing experiments, the Al 2 O 3 thin film was found to suppress the penetration of oxygen from the atmosphere for annealing temperatures below 600 deg. C. Degradation of the film's oxygen blocking property occurred due to the annealing at 700 deg. C, and this was attributed to the oxidation of the Al 2 O 3 by the atmosphere and the resultant introduction of vacancy-type defects

  15. Photoinduced modulation and relaxation characteristics in LaAlO3/SrTiO3 heterointerface

    KAUST Repository

    Jin, K. X.

    2015-03-05

    We report the modulation and relaxation characteristics in the two-dimensional electron gas system at LaAlO3/SrTiO3 heterointerface induced by the ultraviolet light illumination (365 nm). The suppression of Kondo effect at the interface illuminated by the light originates from the light irradiation-induced decoherence effect of localized states. It is interesting to note that the persistent and transient photoinduced effects are simultaneously observed and the photoinduced maximum change values in resistance are 80.8% and 51.4% at T = 20 K, respectively. Moreover, the photoinduced relaxation processes after the irradiation are systematically analyzed using the double exponential model. These results provide the deeper understanding of the photoinduced effect and the experimental evidence of tunable Kondo effect in oxides-based two-dimensional electron gas systems.

  16. Photoinduced modulation and relaxation characteristics in LaAlO3/SrTiO3 heterointerface

    KAUST Repository

    Jin, K. X.; Lin, W.; Luo, B. C.; Wu, Tao

    2015-01-01

    We report the modulation and relaxation characteristics in the two-dimensional electron gas system at LaAlO3/SrTiO3 heterointerface induced by the ultraviolet light illumination (365 nm). The suppression of Kondo effect at the interface illuminated by the light originates from the light irradiation-induced decoherence effect of localized states. It is interesting to note that the persistent and transient photoinduced effects are simultaneously observed and the photoinduced maximum change values in resistance are 80.8% and 51.4% at T = 20 K, respectively. Moreover, the photoinduced relaxation processes after the irradiation are systematically analyzed using the double exponential model. These results provide the deeper understanding of the photoinduced effect and the experimental evidence of tunable Kondo effect in oxides-based two-dimensional electron gas systems.

  17. Microscopic observation of ferroelectric domains in SrTiO3 using birefringence imaging techniques under high electric fields

    International Nuclear Information System (INIS)

    Manaka, Hirotaka; Nozaki, Hirofumi; Miura, Yoko

    2017-01-01

    Phase transitions in SrTiO 3 between quantum paraelectric, coherent paraelectric, and electric-field-induced ferroelectric states are governed by tetragonal domains with quantum fluctuations. However, their characteristics are still unclear. To observe the electric-field-induced ferroelectric state using birefringence imaging techniques, we developed a suitable sample holder to apply high electric fields of up to E ≃ 5 kV/cm and temperatures down to T = 20 K. From birefringence imaging measurements of the ferroelectric LiNbO 3 with varying electric field, distributions of the electric field in the sample stage were found to be negligible. In SrTiO 3 , a huge-retardance area corresponding to the ferroelectric domains appears at E > 2 kV/cm and T ≤ 60 K even though the paraelectric domains partially remain. Furthermore, the fast-axis direction rotates by 90° at the ferroelectric phase transition because of an electrostrictive effect in ferroelectrics. The phase diagram of the critical electric field and temperature agrees with previous reports obtained from dielectric and neutron scattering measurements. (author)

  18. Strain-induced large spin splitting and persistent spin helix at LaAlO$_3$/SrTiO$_3$ interface

    OpenAIRE

    Yamaguchi, Naoya; Ishii, Fumiyuki

    2017-01-01

    We investigated the effect of the tensile strain on the spin splitting at the n-type interface in LaAlO$_3$/SrTiO$_3$ in terms of the spin-orbit coupling coefficient $\\alpha$ and spin texture in the momentum space using first-principles calculations. We found that the $\\alpha$ could be controlled by the tensile strain and be enhanced up to 5 times for the tensile strain of 7%, and the effect of the tensile strain leads to a persistent spin helix, which has a long spin lifetime. These results ...

  19. New insights on the synthesis and electronic transport in bulk polycrystalline Pr-doped SrTiO3−δ

    KAUST Repository

    Dehkordi, Arash Mehdizadeh; Bhattacharya, Sriparna; Darroudi, Taghi; Alshareef, Husam N.; Tritt, Terry M.

    2015-01-01

    versus Pr6O11) on the synthesis and electronic transport in Pr-doped SrTiO3 ceramics. It was observed that the high-temperature electronic transport properties are independent of the choice of praseodymium doping source for samples prepared following our

  20. Tunable Electron-Electron Interactions in LaAlO_{3}/SrTiO_{3} Nanostructures

    Directory of Open Access Journals (Sweden)

    Guanglei Cheng

    2016-12-01

    Full Text Available The interface between the two complex oxides LaAlO_{3} and SrTiO_{3} has remarkable properties that can be locally reconfigured between conducting and insulating states using a conductive atomic force microscope. Prior investigations of “sketched” quantum dot devices revealed a phase in which electrons form pairs, implying a strongly attractive electron-electron interaction. Here, we show that these devices with strong electron-electron interactions can exhibit a gate-tunable transition from a pair-tunneling regime to a single-electron (Andreev bound state tunneling regime where the interactions become repulsive. The electron-electron interaction sign change is associated with a Lifshitz transition where the d_{xz} and d_{yz} bands start to become occupied. This electronically tunable electron-electron interaction, combined with the nanoscale reconfigurability of this system, provides an interesting starting point towards solid-state quantum simulation.

  1. Anisotropic magnetoresistance and spin polarization of La0.7Sr0.3MnO3/SrTiO3 superlattices

    International Nuclear Information System (INIS)

    Wang, L.M.; Guo, C.-C.

    2005-01-01

    The crystalline structure, anisotropic magnetoresistance (AMR), and magnetization of La 0.7 Sr 0.3 MnO 3 /SrTiO 3 (LSMO/STO) superlattices grown by a rf sputtering system are systematically analyzed to study the spin polarization of manganite at interfaces. The presence of positive low-temperature AMR in LSMO/STO superlattices implies that two bands of majority and minority character contribute to the transport properties, leading to a reduced spin polarization. Furthermore, the magnetization of superlattices follows the T 3/2 law and decays more quickly as the thickness ratio d STO /d LSMO increases, corresponding to a reduced exchange coupling. The results clearly show that the spin polarization is strongly correlated with the influence of interface-induced strain on the structure

  2. Remember the Titans: A Theoretical Analysis

    Directory of Open Access Journals (Sweden)

    Rameca Leary

    2013-06-01

    Full Text Available This paper addresses a pivotal time in American history, when a 1971 Supreme Court mandate required southern school districts to end segregation (Daugherity, 2011. In Alexandria, Virginia, the merger of three rival high schools yielded a racially diverse football team and coaching staff. Beforehand, blacks and whites had their own schools. Many wondered how the new T.C. Williams Titans football team would fare. This paper takes an in-depth look at the film, Remember the Titans, which is based on this story. It analyzes the film using Gordon Allport’s (1954 Intergroup Contact Theory to assess how people from different backgrounds interact within group settings. It explores how communication barriers and the absence of knowledge can lead to ignorance. A 21st century legacy is also discussed, including ideas for further research. 

  3. Remember the Titans: A Theoretical Analysis

    Directory of Open Access Journals (Sweden)

    Rameca Leary

    2013-06-01

    Full Text Available This paper addresses a pivotal time in American history, when a 1971 Supreme Court mandate required southern school districts to end segregation (Daugherity, 2011. In Alexandria, Virginia, the merger of three rival high schools yielded a racially diverse football team and coaching staff. Beforehand, blacks and whites had their own schools. Many wondered how the new T.C. Williams Titans football team would fare. This paper takes an in-depth look at the film, Remember the Titans, which is based on this story. It analyzes the film using Gordon Allport’s (1954 Intergroup Contact Theory to assess how people from different backgrounds interact within group settings. It explores how communication barriers and the absence of knowledge can lead to ignorance. A 21st century legacy is also discussed, including ideas for further research.

  4. Influence of Mg O and B2O3 addition on reaction sintering, properties and microstructure of Aluminum titanate

    International Nuclear Information System (INIS)

    Ajami, R.; Sarpoolaki, H.; Akbari, G. H.

    2007-01-01

    The effect of Mg O and B 2 O 3 on the formation, physical properties, phase analysis and microstructure of aluminum titanate was investigated. Density results showed the sample containing of 1 wt percent B 2 O 3 and 2 wt percent Mg O leads to the highest density while the lowest density was seen in samples containing 1 wt percent B 2 O 3 compared to pure aluminum titanate. Regarding the phase analysis of samples, Mg O was found most effective additive on reaction sintering of aluminum titanate through the intermediate phases. Furthermore at the temperatures above 1350 d eg C , B 2 O 3 promote the formation reaction of aluminum titanate. Microstructural analysis showed the samples containing Mg O are fine grain and homogeneous. Thermal expansion coefficient of samples with additives is greater than pure aluminum titanate. Pure aluminum titanate samples and one containing B 2 O 3 additive decompose to Al 2 O 3 and TiO 2 after 5 hours heat treatment at 1150 d eg C while the samples containing 2 wt percent Mg O was stable even after 25 hours

  5. Cytotoxicity of Titanate-Calcium Complexes to MC3T3 Osteoblast-Like Cells

    Science.gov (United States)

    Drury, Jeanie L.; Moussi, Joelle; Taylor-Pashow, Kathryn M. L.

    2016-01-01

    Monosodium titanates (MST) are a relatively novel form of particulate titanium dioxide that have been proposed for biological use as metal sorbents or delivery agents, most recently calcium (II). In these roles, the toxicity of the titanate or its metal complex is crucial to its biological utility. The aim of this study was to determine the cytotoxicity of MST and MST-calcium complexes with MC3T3 osteoblast-like cells; MST-Ca(II) complexes could be useful to promote bone formation in various hard tissue applications. MC3T3 cells were exposed to native MST or MST-Ca(II) complexes for 24–72 h. A CellTiter-Blue® assay was employed to assess the metabolic activity of the cells. The results showed that MST and MST-Ca(II) suppressed MC3T3 metabolic activity significantly in a dose-, time-, and cell-density-dependent fashion. MST-Ca(II) suppressed MC3T3 metabolism in a statistically identical manner as native MST at all concentrations. We concluded that MST and MST-Ca(II) are significantly cytotoxic to MC3T3 cells through a mechanism yet unknown; this is a potential problem to the biological utility of these complexes. PMID:28044136

  6. Cytotoxicity of Titanate-Calcium Complexes to MC3T3 Osteoblast-Like Cells

    Directory of Open Access Journals (Sweden)

    Yen-Wei Chen

    2016-01-01

    Full Text Available Monosodium titanates (MST are a relatively novel form of particulate titanium dioxide that have been proposed for biological use as metal sorbents or delivery agents, most recently calcium (II. In these roles, the toxicity of the titanate or its metal complex is crucial to its biological utility. The aim of this study was to determine the cytotoxicity of MST and MST-calcium complexes with MC3T3 osteoblast-like cells; MST-Ca(II complexes could be useful to promote bone formation in various hard tissue applications. MC3T3 cells were exposed to native MST or MST-Ca(II complexes for 24–72 h. A CellTiter-Blue® assay was employed to assess the metabolic activity of the cells. The results showed that MST and MST-Ca(II suppressed MC3T3 metabolic activity significantly in a dose-, time-, and cell-density-dependent fashion. MST-Ca(II suppressed MC3T3 metabolism in a statistically identical manner as native MST at all concentrations. We concluded that MST and MST-Ca(II are significantly cytotoxic to MC3T3 cells through a mechanism yet unknown; this is a potential problem to the biological utility of these complexes.

  7. Titan's Ammonia Feature

    Science.gov (United States)

    Smythe, W.; Nelson, R.; Boryta, M.; Choukroun, M.

    2011-01-01

    NH3 has long been considered an important component in the formation and evolution of the outer planet satellites. NH3 is particularly important for Titan, since it may serve as the reservoir for atmospheric nitrogen. A brightening seen on Titan starting in 2004 may arise from a transient low-lying fog or surface coating of ammonia. The spectral shape suggests the ammonia is anhydrous, a molecule that hydrates quickly in the presence of water.

  8. Ferroelectricity of Sn-doped SrTiO3 perovskites with tin at both A and B sites

    Science.gov (United States)

    Suzuki, Shoichiro; Honda, Atsushi; Iwaji, Naoki; Higai, Shin'ichi; Ando, Akira; Takagi, Hiroshi; Kasatani, Hirofumi; Deguchi, Kiyoshi

    2012-08-01

    We successfully obtained Sn-doped SrTiO3 (SSTO) perovskites, and clarified their ferroelectricity and structural properties by using first-principles theoretical calculations. The ferroelectricity of SSTO was confirmed by the appearance of a dielectric permittivity maximum and a clear hysteresis loop of the relationship between the external electric field and the electric flux density below 180 K. X-ray diffraction and Raman spectra revealed the structural phase transition of SSTO at approximately 200 K. We directly observed by spherical aberration corrected scanning transmission electron microscopy with energy-dispersive x-ray spectroscopy that Sn ions are doped into both Sr and Ti sites (SnA and SnB), and that SnA is located at an off-centered position. We also performed theoretical analyses of SSTO and related perovskites, and found that SnA is preferentially located in an off-centered position and that SnA and the O6 octahedron, which includes SnB in its center, oscillate along the antiphase direction in the soft mode. Thus, we propose that the ferroelectricity of SSTO originates from the antiphase off-centering, which induces ferroelectric nanoregions in paraelectric SrTiO3.

  9. Electronic structure and lattice dynamics at the interface of single layer FeSe and SrTiO3

    Science.gov (United States)

    Ahmed, Towfiq; Balatsky, Alexander; Zhu, Jian-Xin

    Recent discovery of high-temperature superconductivity with the superconducting energy gap opening at temperatures close to or above the liquid nitrogen boiling point in the single-layer FeSe grown on SrTiO3 has attracted significant interest. It suggests that the interface effects can be utilized to enhance the superconductivity. It has been shown recently that the coupling between the electrons in FeSe and vibrational modes at the interface play an important role. Here we report on a detailed study of electronic structure and lattice dynamics in the single-layer FeSe/SrTiO3 interface by using the state-of-art electronic structure method within the density functional theory. The nature of the vibrational modes at the interface and their coupling to the electronic degrees of freedom are analyzed. In addition, the effect of hole and electron doping in SrTiO3 on the electron-mode coupling strength is also considered. This work was carried out under the auspices of the National Nuclear Security Administration of the U.S. DOE at LANL under Contract No. DE-AC52-06NA25396, and was supported by the DOE Office of Basic Energy Sciences.

  10. Spin injection and detection in lanthanum- and niobium-doped SrTiO3 using the Hanle technique

    KAUST Repository

    Han, Wei

    2013-07-08

    There has been much interest in the injection and detection of spin-polarized carriers in semiconductors for the purposes of developing novel spintronic devices. Here we report the electrical injection and detection of spin-polarized carriers into Nb-doped strontium titanate single crystals and La-doped strontium titanate epitaxial thin films using MgO tunnel barriers and the three-terminal Hanle technique. Spin lifetimes of up to ∼100 ps are measured at room temperature and vary little as the temperature is decreased to low temperatures. However, the mobility of the strontium titanate has a strong temperature dependence. This behaviour and the carrier doping dependence of the spin lifetime suggest that the spin lifetime is limited by spin-dependent scattering at the MgO/strontium titanate interfaces, perhaps related to the formation of doping induced Ti 3+. Our results reveal a severe limitation of the three-terminal Hanle technique for measuring spin lifetimes within the interior of the subject material. © 2013 Macmillan Publishers Limited. All rights reserved.

  11. Epitaxial films of YBa2Cu3O/sub 7-//sub δ/ on NdGaO3, LaGaO3, and SrTiO3 substrates deposited by laser ablation

    International Nuclear Information System (INIS)

    Koren, G.; Gupta, A.; Giess, E.A.; Segmueller, A.; Laibowitz, R.B.

    1989-01-01

    Frequency-doubled Nd:YAG laser (532 nm) pulses of 1.7 J/cm 2 and 10 ns duration were used to deposit thin films of YBa 2 Cu 3 O/sub 7-//sub δ/ by laser ablation on NdGaO 3 , LaGaO 3 , and SrTiO 3 substrates held at 725 +- 5 0 C in 0.2 Torr of O 2 ambient. Electrical resistivities versus temperature of all films show normal metallic behavior and sharp superconducting transitions with T/sub c/ (R = 0) at 92--93 K. Critical current densities in 0.3--0.6 μm thick, 200 μm long, and 10--30 μm wide strips were measured to be 10 6 A/cm 2 at 60, 77, and 80 K in the films on LaGaO 3 , NdGaO 3 , and SrTiO 3 , respectively. X-ray diffraction patterns show that all films grew epitaxially, with domains of only two crystalline orientations rotated 90 0 with respect to each other in the a-b plane (consistent with twins), and the c axis perpendicular to the substrates. The closely matched lattice constants of the film and substrates (0.8--2.1%) result in epitaxial growth of the films

  12. Near-surface effects of transient oxidation and reduction on Nb-doped SrTiO3 epitaxial thin films

    Science.gov (United States)

    Chang, C. F.; Chen, Q. Y.; Wadekar, P. V.; Lozano, O.; Wong, M. S.; Hsieh, W. C.; Lin, W. Y.; Ko, H. H.; Lin, Q. J.; Huang, H. C.; Ho, N. J.; Tu, L. W.; Liao, H. H.; Chinta, P. V.; Chu, W. K.; Seo, H. W.

    2014-03-01

    We studied the effects of transient oxidation and reduction of Nb-doped epitaxial thin films through variations of PAr and PO2. The samples were prepared by co-sputtering of Nb and SrTiO3 on LaAlO3 substrates. The Nb-content were varied from 0-33.7%, as determined by PIXE. Contact resistance, sheet resistance, and optical properties are used to discriminate the effects.

  13. Core-shell SrTiO3/graphene structure by chemical vapor deposition for enhanced photocatalytic performance

    Science.gov (United States)

    He, Chenye; Bu, Xiuming; Yang, Siwei; He, Peng; Ding, Guqiao; Xie, Xiaoming

    2018-04-01

    Direct growth of high quality graphene on the surface of SrTiO3 (STO) was realized through chemical vapor deposition (CVD), to construct few-layer 'graphene shell' on every STO nanoparticle. The STO/graphene composite shows significantly enhanced UV light photocatalytic activity compared with the STO/rGO reference. Mechanism analysis confirms the role of special core-shell structure and chemical bond (Tisbnd C) for rapid interfacial electron transfer and effective electron-hole separation.

  14. Vantage TitanTM 3T 3-tesla MRI system with enhanced serviceability and comfort

    International Nuclear Information System (INIS)

    Kanazawa, Hitoshi; Okamoto, Kazuya; Yamamoto, Takao

    2011-01-01

    Since 3-tesla magnetic resonance imaging (MRI) systems appeared on the market, in addition to their clinical usefulness a variety of issues have been pointed out in the clinical setting. The 3-tesla MRI system has therefore gained a reputation as a difficult system suitable only for hospital facilities including university hospitals that specialize in medical research. To rectify this situation, Toshiba Medical Systems Corporation has developed the Vantage Titan TM 3T, which is expected to not only improve the MRI examination environment, but also to be applicable to patients with claustrophobia and those with large physiques for whom MRI examination has not been appropriate until now, while maintaining the clinical usefulness of the 3-tesla MRI system. The Vantage Titan 3T system also incorporates the Pianissimo TM noise reduction mechanism, which has already been introduced in our 1.5-tesla MRI system and has been highly evaluated by the market. This reduces the stress of patients by providing a quieter and more open examination environment compared with conventional MRI systems. (author)

  15. Intrinsic origin of interface states and band offset profiling of nanostructured LaAlO3/SrTiO3 heterojunctions probed by element-specific resonant spectroscopies

    NARCIS (Netherlands)

    Drera, G.; Salvinelli, G.; Bondino, F.; Magnano, E.; Huijben, Mark; Brinkman, Alexander; Sangaletti, L.

    2014-01-01

    The origin of electronic states at the basis of the 2DEG found in conducting LaAlO 3 /SrTiO 3 interfaces (5 u.c. LaAlO 3 ) is investigated by resonant photoemission experiments at the Ti L 2,3 and La M 4,5 edges. As shown by the resonant enhancement at the Ti L 2,3 edge, electronic states at E F

  16. The preparation of a novel layered lead titanate and its conversion to the perovskite lead titanate PbTiO3

    NARCIS (Netherlands)

    Blake, G.R.; Armstrong, A.R.; Sastre, E.; Wright, P.A.

    2001-01-01

    A novel layered lead titanate with the approximate composition PbTiO2(CO3)0.3(NO3)0.35(OH) has been synthesized hydrothermally under acidic conditions. The structure has been solved and refined from X-ray and neutron powder diffraction data in the space group P -3 1 m, with cell dimensions a =

  17. Quenched Magnon excitations by oxygen sublattice reconstruction in (SrCuO 2) n /(SrTiO 3) 2 superlattices

    NARCIS (Netherlands)

    Dantz, M.; Pelliciari, J.; Samal, D.; Bisogni, V.; Huang, Y.; Olalde-Velasco, P.; Strocov, V. N.; Koster, G.; Schmitt, T.

    2016-01-01

    The recently discovered structural reconstruction in the cuprate superlattice (SrCuO 2) n /(SrTiO 3) 2 has been investigated across the critical value of n = 5 using resonant inelastic x-ray scattering (RIXS). We find that at the critical value of n, the cuprate layer remains largely in the

  18. Rapid Synthesis and Formation Mechanism of Core-Shell-Structured La-Doped SrTiO3 with a Nb-Doped Shell

    Directory of Open Access Journals (Sweden)

    Nam-Hee Park

    2015-07-01

    Full Text Available To provide a convenient and practical synthesis process for metal ion doping on the surface of nanoparticles in an assembled nanostructure, core-shell-structured La-doped SrTiO3 nanocubes with a Nb-doped surface layer were synthesized via a rapid synthesis combining a rapid sol-precipitation and hydrothermal process. The La-doped SrTiO3 nanocubes were formed at room temperature by a rapid dissolution of NaOH pellets during the rapid sol-precipitation process, and the Nb-doped surface (shell along with Nb-rich edges formed on the core nanocubes via the hydrothermal process. The formation mechanism of the core-shell-structured nanocubes and their shape evolution as a function of the Nb doping level were investigated. The synthesized core-shell-structured nanocubes could be arranged face-to-face on a SiO2/Si substrate by a slow evaporation process, and this nanostructured 10 μm thick thin film showed a smooth surface.

  19. In-situ YBa2Cu3O7/SrTiO3/YBa2Cu3O7 a-b plane Josephson edge junctions

    International Nuclear Information System (INIS)

    Aharoni, E.; Koren, G.; Polturak, E.; Cohen, D.; Iskevitch, E.

    1992-01-01

    YBCO/SrTiO 3 /YBCO thin film edge junctions were prepared in-situ and characterized. The epitaxial growth of SrTiO 3 on YBCO led to a sharp and well defined junction edge with a very high yield. Typical junctions showed critical currents up to 83 K, with I c ∝ (1 - T/Tc) 2 temperature dependence. Sharp Shapiro steps were observed under microwave radiation at temperatures up to 82 K. A typical diffraction pattern was found in the voltage response of the junctions to transverse magnetic field. (orig.)

  20. Electrical characterization of strontium titanate borosilicate glass ceramics system with bismuth oxide addition using impedance spectroscopy

    International Nuclear Information System (INIS)

    Thakur, O.P.; Kumar, Devendra; Parkash, Om; Pandey, Lakshman

    2003-01-01

    The ac electrical data, measured in the frequency range 0.1 kHz-1 MHz, were used to study the electrical response of strontium titanate borosilicate glass ceramic system with bismuth oxide addition. Complex plane plots from these electrical data for various glass ceramic samples reveal contributions from simultaneously operating polarization mechanisms to overall dielectric behavior. The complex modulus (M * ) representation of electrical data for various glass ceramic samples were found to be more informative. Equivalent circuit models, which represent the electrical behavior of glass ceramic samples, were determined using complex non-linear least square (CNLS) fitting. An attempt has been made to understand the dielectric behavior of various glass ceramics in terms of contributions arising from different polarization processes occurring at glassy matrix, crystalline phases, glass to crystal interface region and blocking electrodes. Glass ceramics containing SrTiO 3 and TiO 2 (rutile) phases show thermally stable dielectric behavior

  1. Surface structural reconstruction of SrVO3 thin films on SrTiO3 (001)

    Science.gov (United States)

    Wang, Gaomin; Saghayezhian, Mohammad; Chen, Lina; Guo, Hangwen; Zhang, Jiandi

    Paramagnetic metallic oxide SrVO3>(SVO) is an itinerant system known to undergo thickness-induced metal-insulator-transition (MIT) in ultrathin film form, which makes it a prototype system for the study of the mechanism behind metal-insulator-transition like structure distortion, electron correlations and disorder-induced localization. We have grown SrVO3 thin film with atomically flat surface through the layer-by-layer deposition by laser Molecular Beam Epitaxy (laser-MBE) on SrTiO3 (001) surface. Low Energy Electron Diffraction (LEED) measurements reveal that there is a (√2X √2) R45°surface reconstruction independent of film thickness. By using LEED-I(V) structure refinement, we determine the surface structure. In combination with X-ray Photoelectron Spectroscopy (XPS) and Scanning Tunneling Microscopy (STM), we discuss the implication on the MIT in ultrathin films below 2-3 unit cell thickness. This work is supported by the National Science Foundation under the NSF EPSCoR Cooperative Agreement No. EPS-1003897 with additional support from the Louisiana Board of Regents.

  2. Diurnal variations of Titan

    Science.gov (United States)

    Cui, J.; Galand, M.; Yelle, R. V.; Vuitton, V.; Wahlund, J.-E.; Lavvas, P. P.; Mueller-Wodarg, I. C. F.; Kasprzak, W. T.; Waite, J. H.

    2009-04-01

    We present our analysis of the diurnal variations of Titan's ionosphere (between 1,000 and 1,400 km) based on a sample of Ion Neutral Mass Spectrometer (INMS) measurements in the Open Source Ion (OSI) mode obtained from 8 close encounters of the Cassini spacecraft with Titan. Though there is an overall ion depletion well beyond the terminator, the ion content on Titan's nightside is still appreciable, with a density plateau of ~700 cm-3 below ~1,300 km. Such a plateau is associated with the combination of distinct diurnal variations of light and heavy ions. Light ions (e.g. CH5+, HCNH+, C2H5+) show strong diurnal variation, with clear bite-outs in their nightside distributions. In contrast, heavy ions (e.g. c-C3H3+, C2H3CNH+, C6H7+) present modest diurnal variation, with significant densities observed on the nightside. We propose that the distinctions between light and heavy ions are associated with their different chemical loss pathways, with the former primarily through "fast" ion-neutral chemistry and the latter through "slow" electron dissociative recombination. The INMS data suggest day-to-night transport as an important source of ions on Titan's nightside, to be distinguished from the conventional scenario of auroral ionization by magnetospheric particles as the only ionizing source on the nightside. This is supported by the strong correlation between the observed night-to-day ion density ratios and the associated ion lifetimes. We construct a time-dependent ion chemistry model to investigate the effects of day-to-night transport on the ionospheric structures of Titan. The predicted diurnal variation has similar general characteristics to those observed, with some apparent discrepancies which could be reconciled by imposing fast horizontal thermal winds in Titan's upper atmosphere.

  3. Interferometric imaging of Titan's HC$_3$N, H$^{13}$CCCN and HCCC$^{15}$N

    OpenAIRE

    Cordiner, M. A.; Nixon, C. A.; Charnley, S. B.; Teanby, N. A.; Molter, E. M.; Kisiel, Z.; Vuitton, V.

    2018-01-01

    We present the first maps of cyanoacetylene isotopologues in Titan's atmosphere, including H$^{13}$CCCN and HCCC$^{15}$N, detected in the 0.9 mm band using the Atacama Large Millimeter/submillimeter array (ALMA) around the time of Titan's (southern winter) solstice in May 2017. The first high-resolution map of HC$_3$N in its $v_7=1$ vibrationally excited state is also presented, revealing a unique snapshot of the global HC$_3$N distribution, free from the strong optical depth effects that adv...

  4. Ion channeling study of lattice distortions in chromium-doped SrTiO3 crystals

    Czech Academy of Sciences Publication Activity Database

    Lavrentiev, Vasyl; Vacík, Jiří; Dejneka, Alexandr; Trepakov, Vladimír; Jastrabík, Lubomír

    2013-01-01

    Roč. 55, č. 7 (2013), s. 1431-1437 ISSN 1063-7834 R&D Projects: GA ČR(CZ) GAP107/11/1856; GA ČR(CZ) GBP108/12/G108; GA ČR GAP108/12/1941 Grant - others:GA MŠk(CZ) ED2.1.00/03.0058 Program:ED Institutional support: RVO:68378271 ; RVO:61389005 Keywords : ion channeling * lattice distortions * SrTiO3 Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders; BM - Solid Matter Physics ; Magnetism (FZU-D) Impact factor: 0.782, year: 2013 http://link.springer.com/article/10.1134%2FS1063783413070202

  5. Diversity of hydrogen configuration and its roles in SrTiO3−δ

    Directory of Open Access Journals (Sweden)

    Yoshiki Iwazaki

    2014-01-01

    Full Text Available As a source of carrier electron, various configurations of hydrogen in SrTiO3 are searched by using first-principles calculations. The most stable form of hydrogen is found to be H−, where doubly charged oxygen vacancy VO2+ changes into singly charged HO+. Most importantly, an additional H− is found to be weakly trapped by HO+, which completely neutralizes carrier electrons by forming (2HO0. These unexpected behaviors of hydrogen, which can explain reported experimental results, expand the role of the hydrogen in carrier-control technology in transition-metal oxides.

  6. Titan!

    Science.gov (United States)

    Matson, Dennis L.

    2010-05-01

    Cassini-Huygens achieved Saturnian orbit on July 1, 2004. The first order of business was the safe delivery of the Huygens atmospheric probe to Titan that took place on January 14, 2005. Huygens descended under parachute obtaining observations all the way down to a safe landing. It revealed Titan for the first time. Stunning are the similarities between Titan and the Earth. Viewing the lakes and seas, the fluvial terrain, the sand dunes and other features through the hazy, nitrogen atmosphere, brings to mind the geological processes that created analogous features on the Earth. On Titan frozen water plays the geological role of rock; liquid methane takes the role of terrestrial water. The atmospheres of both Earth and Titan are predominately nitrogen gas. Titan's atmosphere contains 1.5% methane and no oxygen. The surface pressure on Titan is 1.5 times the Earth's. There are aerosol layers and clouds that come and go. Now, as Saturn proceeds along its solar orbit, the seasons are changing. The effects upon the transport of methane are starting to be seen. A large lake in the South Polar Region seems to be filling more as winter onsets. Will the size and number of the lakes in the South grow during winter? Will the northern lakes and seas diminish or dry up as northern summer progresses? How will the atmospheric circulation change? Much work remains not only for Cassini but also for future missions. Titan has many different environments to explore. These require more capable instruments and in situ probes. This work was conducted at the Jet Propulsion Laboratory, California Institute of Technology under contract with the National Aeronautics and Space Administration.

  7. Incipient 2D Mott insulators in extreme high electron density, ultra-thin GdTiO3/SrTiO3/GdTiO3 quantum wells

    Science.gov (United States)

    Allen, S. James; Ouellette, Daniel G.; Moetakef, Pouya; Cain, Tyler; Chen, Ru; Balents, Leon; Stemmer, Susanne

    2013-03-01

    By reducing the number of SrO planes in a GdTiO3 /SrTiO3/ GdTiO3 quantum well heterostructure, an electron gas with ~ fixed 2D electron density can be driven close to the Mott metal insulator transition - a quantum critical point at ~1 electron per unit cell. A single interface between the Mott insulator GdTiO3 and band insulator SrTiO3 has been shown to introduce ~ 1/2 electron per interface unit cell. Two interfaces produce a quantum well with ~ 7 1014 cm-2 electrons: at the limit of a single SrO layer it may produce a 2D magnetic Mott insulator. We use temperature and frequency dependent (DC - 3eV) conductivity and temperature dependent magneto-transport to understand the relative importance of electron-electron interactions, electron-phonon interactions, and surface roughness scattering as the electron gas is compressed toward the quantum critical point. Terahertz time-domain and FTIR spectroscopies, measure the frequency dependent carrier mass and scattering rate, and the mid-IR polaron absorption as a function of quantum well thickness. At the extreme limit of a single SrO plane, we observe insulating behavior with an optical gap substantially less than that of the surrounding GdTiO3, suggesting a novel 2D Mott insulator. MURI program of the Army Research Office - Grant No. W911-NF-09-1-0398

  8. Magnetic and electrical transport properties of LaBaCo2O(5.5+δ) thin films on vicinal (001) SrTiO3 surfaces.

    Science.gov (United States)

    Ma, Chunrui; Liu, Ming; Collins, Gregory; Wang, Haibin; Bao, Shanyong; Xu, Xing; Enriquez, Erik; Chen, Chonglin; Lin, Yuan; Whangbo, Myung-Hwan

    2013-01-23

    Highly epitaxial LaBaCo(2)O(5.5+δ) thin films were grown on the vicinal (001) SrTiO(3) substrates with miscut angles of 0.5°, 3.0°, and 5.0° to systemically study strain effect on its physical properties. The electronic transport properties and magnetic behaviors of these films are strongly dependent on the miscut angles. With increasing the miscut angle, the transport property of the film changes from semiconducting to semimetallic, which results most probably from the locally strained domains induced by the surface step terraces. In addition, a very large magnetoresistance (34% at 60 K) was achieved for the 0.5°-miscut film, which is ~30% larger than that for the film grown on the regular (001) SrTiO(3) substrates.

  9. Development of Strontium Titanate Thin films on Technical Substrates for Superconducting Coated Conductors

    DEFF Research Database (Denmark)

    Pallewatta, Pallewatta G A P; Yue, Zhao; Grivel, Jean-Claude

    2012-01-01

    SrTiO3 is a widely studied perovskite material due to its advantages as a template for high temperature superconducting tapes. Heteroepitaxial SrTiO3 thin films were deposited on Ni/W tapes using dip-coating in a precursor solution followed by drying and annealing under reducing conditions. Nearl...

  10. Chemistry and evolution of Titan's atmosphere

    International Nuclear Information System (INIS)

    Strobel, D.F.

    1982-01-01

    The chemistry and evolution of Titan's atmosphere is reviewed in the light of the scientific findings from the Voyager mission. It is argued that the present N 2 atmosphere may be Titan's initial atmosphere rather than photochemically derived from an original NH 3 atmosphere. The escape rate of hydrogen from Titan is controlled by photochemical production from hydrocarbons. CH 4 is irreversibly converted to less hydrogen rich hydrocarbons, which over geologic time accumulate on the surface to a layer thickness of approximately 0.5 km. Magnetospheric electrons interacting with Titan's exosphere may dissociate enough N 2 into hot, escaping N atoms to remove approximately 0.2 of Titan's present atmosphere over geologic time. The energy dissipation of magnetospheric electrons exceeds solar e.u.v. energy deposition in Titan's atmosphere by an order of magnitude and is the principal driver of nitrogen photochemistry. The environmental conditions in Titan's upper atmosphere are favorable to building up complex molecules, particularly in the north polar cap region. (author)

  11. Photoconductive response of a single Au nanorod coupled to LaAlO3/SrTiO3 nanowires

    International Nuclear Information System (INIS)

    Jnawali, Giriraj; Chen, Lu; Huang, Mengchen; Lee, Hyungwoo; Ryu, Sangwoo; Podkaminer, Jacob P.; Eom, Chang-Beom; Irvin, Patrick; Levy, Jeremy

    2015-01-01

    Terahertz (THz) spectroscopy is an important tool that provides resonant access to free carrier motion, molecular rotation, lattice vibrations, excitonic, spin, and other degrees of freedom. Current methods using THz radiation suffer from limits due to diffraction or low-sensitivity, preventing application at the scale of single nanoscale objects. Here, we present coupling between plasmonic degrees of freedom in a single gold nanorod and broadband THz emission generated from a proximal LaAlO 3 /SrTiO 3 nanostructure. A strong enhancement of THz emission is measured for incident radiation that is linearly polarized along the long axis of the nanorod. This demonstration paves the way for the investigation of near-field plasmonic coupling in a variety of molecular-scale systems

  12. Anisotropic electrical properties of epitaxial Yba2Cu3O7-gd films on (110) SrTiO3

    International Nuclear Information System (INIS)

    Gupta, A.; Koren, G.; Baseman, R.J.; Segmuller, A.; Holber, W.

    1989-01-01

    Epitaxial thin films of YBa 2 Cu 3 O 7 - δ were deposited on (110) SrTiO 3 at 600 degrees C in the presence of atomic oxygen using the laser ablation technique. X-ray diffraction patterns in the standard Bragg and grazing incidence modes show epitaxial growth of the films with their c-axis and axis parallel to the and directions in the plane of the substrate, respectively. Superconductivity with T c (R = ) = 82 K was found along the direction in the basal plane, whereas finite resistivity down to 5 k was observed along the c-axis direction. The authors maintain that these preliminary results suggest that YBa 2 Cu 3 O 7 - δ behaves like a true two-dimensional superconductor

  13. Disorder influence on the magnetic properties of La0.55Sr0.45MnO3/SrTiO3 superlattices

    International Nuclear Information System (INIS)

    Haberkorn, N.; Sirena, M.; Guimpel, J.; Steren, L.B.

    2004-01-01

    The structural and physical properties of La 0.55 Sr 0.45 MnO 3 /SrTiO 3 superlattices grown by magnetron sputtering are studied. Two deposition temperatures and different mismatched substrates and buffer layers were used. The structure was determined by refinement through X-ray diffraction pattern fitting. The results indicate 1 unit cell (u.c.) interdiffusion at the interfaces and a 1 u.c. layer thickness fluctuation, i.e. roughness. In-plane hysteresis loops show the expected ferromagnetic behavior, while the perpendicular-to-plane hysteresis loops show anomalies which could evidence magnetic domain size inhomogeneities and stress

  14. Modification of SrTiO3 single-crystalline surface after plasma flow treatment

    Energy Technology Data Exchange (ETDEWEB)

    Levin, Alexandr A.; Weissbach, Torsten; Leisegang, Tilmann; Meyer, Dirk C. [Institut fuer Strukturphysik, Technische Universitaet Dresden, 01062 Dresden (Germany); Kulagin, Nikolay A. [Kharkiv National University for Radioelectronics, av. Shakespeare 6-48, 61045 Kharkiv (Ukraine); Langer, Enrico [Institut fuer Festkoerperphysik, Technische Universitaet Dresden, 01062 Dresden (Germany)

    2009-07-01

    Surface of pure and transition metal-doped SrTiO3(STO) single crystals before and after hydrogen plasma-flow treatment (energy of 5..20 J/cm2) is investigated by wide-angle X-ray diffraction (WAXRD), fluorescence X-ray absorption near edge structure (XANES) and scanning electron microscopy (SEM) techniques. Plasma treatment results in the formation of a textured polycrystalline layer at the surface of the single-crystalline samples with different orientation. The formation of the quasi-ordered structures consisting of nanoscale-sized pyramids is observed by SEM. XANES evidences the change of the valency of the part of Ti4+ to Ti3+ due to the plasma treatment. The data obtained together with results of X-ray spectroscopy measurements gives evidences of the change of stoichiometry of the STO samples resulting in a change of their physical properties after plasma treatment.

  15. Erbium implantation in Strontium Titanate

    CERN Document Server

    Araújo, J P; Alves, E; Correia, J G; Monteiro, T; Soares, J; Santos, L

    2002-01-01

    We report on the lattice location of Er in SrTiO$_{3}$ single crystals using the emission channeling technique. The angular distribution of conversion electrons emitted from $^{167m}$Er(T$_{1/2}$=2.27 s) was monitored with a position-sensitive detector following the room-temperature 60 keV implantation of the precursor isotope $^{167}$Tm(T$_{1/2}$=9.25 d) to a dose of 2$\\times$ 10$^{12}$ at./cm$^{2}$. The results for the sample annealed in vacuum at 610°C for 15 min provide direct evidence that Er occupies both Sr and Ti substitutional lattice sites. In addition, thermal recovery of lattice damage was also studied with RBS/C for SrTiO$_{3}$ implanted to doses of 5$\\times$ 10$^{14}$ and 5 $\\times$ 10$^{15}$ Er/cm$^{2}$. We further comment on preliminary photoluminescence results from these samples.

  16. Electrical and magnetic behavior of iron doped nickel titanate (Fe{sup 3+}/NiTiO{sub 3}) magnetic nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Lenin, Nayagam; Karthik, Arumugam; Sridharpanday, Mathu; Selvam, Mohanraj; Srither, Saturappan Ravisekaran; Arunmetha, Sundarmoorthy; Paramasivam, Palanisamy; Rajendran, Venkatachalam, E-mail: veerajendran@gmail.com

    2016-01-01

    Iron doped nickel titanate (Fe{sup 3+}/NiTiO{sub 3}) ferromagnetic nanoparticles with different concentrations of Fe (0.2, 0.4, and 0.6 mol) were synthesized using precipitation route with precursor source such as nickel nitrate and iron nitrate solutions. The prepared magnetic nanopowders were investigated through X-ray diffraction (XRD), Fourier transform infrared, scanning electron microscope, X-ray fluorescence, Brunauer–Emmett–Teller, vibrating sample magnetometer, and electrochemical impedance spectroscopy to explore the structural, ferromagnetic, and dielectric properties. The obtained XRD pattern shows formation of iron doped nickel titanate in orthorhombic structure. The crystallite size ranges from 57 to 21 nm and specific surface area ranges from 11 to 137 m{sup 2} g{sup −1}. The hysteresis loops of nanomagnetic materials show ferromagnetic behavior with higher magnitude of coercivity (H{sub c}) 867–462 Oe. The impedance analysis of ferromagnetic materials explores the ferro-dielectric behavior with enhanced properties of Fe{sup 3+}/NiTiO{sub 3} nanoparticles at higher Fe content. - Highlights: • Iron doped nickel titanate magnetic nanoparticles. • Ferromagnetic magnetism behavior with higher magnitude of coercivity. • Dielectric behavior of ferromagnetic nanoparticles with increase of Fe content.

  17. Analysis of SrTiO sub 3 step-flow growth by using RHEED

    CERN Document Server

    Nakagawa, N; Kawasaki, M; Ohashi, S; Koinuma, H

    1999-01-01

    SrTiO sub 3 homoepitaxial films were deposited by pulsed-laser deposition in a chamber equipped with a reflection high-energy electron-diffraction (RHEED) specular spot-intensity monitoring system. Changes in the substrate temperature or the excimer laser pulse rate gave rise to different behaviors of the RHEED specular intensity. At low temperatures and high pulse rates, ordinary RHEED oscillations were observed, indicating layer-by-layer growth. At very high temperatures and low pulse rates, the RHEED specular intensity was modulated synchronously with the excimer laser pulses, indicating that film growth proceeded in the step-flow mode. No Nb diffusion from the substrates into the homoepitaxial films was observed, even at the highest deposition temperatures, when Nb-doped STO substrates were used.

  18. 3D hybrid simulation of the Titan's plasma environment

    Science.gov (United States)

    Lipatov, Alexander; Sittler, Edward, Jr.; Hartle, Richard

    2007-11-01

    Titan plays an important role as a simulation laboratory for multiscale kinetic plasma processes which are key processes in space and laboratory plasmas. A development of multiscale combined numerical methods allows us to use more realistic plasma models at Titan. In this report, we describe a Particle-Ion--Fluid-Ion--Fluid--Electron method of kinetic ion-neutral simulation code. This method takes into account charge-exchange and photoionization processes. The model of atmosphere of Titan was based on a paper by Sittler, Hartle, Vinas et al., [2005]. The background ions H^+, O^+ and pickup ions H2^+, CH4^+ and N2^+ are described in a kinetic approximation, where the electrons are approximated as a fluid. In this report we study the coupling between background ions and pickup ions on the multiple space scales determined by the ion gyroradiis. The first results of such a simulation of the dynamics of ions near Titan are discussed in this report and compared with recent measurements made by the Cassini Plasma Spectrometer (CAPS, [Hartle, Sittler et al., 2006]). E C Sittler Jr., R E Hartle, A F Vinas, R E Johnson, H T Smith and I Mueller-Wodarg, J. Geophys. Res., 110, A09302, 2005.R E Hartle, E C Sittler, F M Neubauer, R E Johnson, et al., Planet. Space Sci., 54, 1211, 2006.

  19. Significant enhancement in thermoelectric properties of polycrystalline Pr-doped SrTiO3−δ ceramics originating from nonuniform distribution of Pr dopants

    KAUST Repository

    Dehkordi, Arash Mehdizadeh

    2014-05-12

    Recently, we have reported a significant enhancement ( >70% at 500 °C) in the thermoelectric power factor (PF) of bulk polycrystalline Pr-doped SrTiO3 ceramics employing a novel synthesis strategy which led to the highest ever reported values of PF among doped polycrystalline SrTiO3. It was found that the formation of Pr-rich grain boundary regions gives rise to an enhancement in carrier mobility. In this Letter, we investigate the electronic and thermal transport in Sr1− x Pr x TiO3 ceramics in order to determine the optimum doping concentration and to evaluate the overall thermoelectric performance. Simultaneous enhancement in the thermoelectric power factor and reduction in thermal conductivity in these samples resulted in more than 30% improvement in the dimensionless thermoelectric figure of merit (ZT) for the whole temperature range over all previously reported maximum values. Maximum ZT value of 0.35 was obtained at 500 °C.

  20. Significant enhancement in thermoelectric properties of polycrystalline Pr-doped SrTiO3−δ ceramics originating from nonuniform distribution of Pr dopants

    KAUST Repository

    Dehkordi, Arash Mehdizadeh; Bhattacharya, Sriparna; He, Jian; Alshareef, Husam N.; Tritt, Terry M.

    2014-01-01

    Recently, we have reported a significant enhancement ( >70% at 500 °C) in the thermoelectric power factor (PF) of bulk polycrystalline Pr-doped SrTiO3 ceramics employing a novel synthesis strategy which led to the highest ever reported values of PF among doped polycrystalline SrTiO3. It was found that the formation of Pr-rich grain boundary regions gives rise to an enhancement in carrier mobility. In this Letter, we investigate the electronic and thermal transport in Sr1− x Pr x TiO3 ceramics in order to determine the optimum doping concentration and to evaluate the overall thermoelectric performance. Simultaneous enhancement in the thermoelectric power factor and reduction in thermal conductivity in these samples resulted in more than 30% improvement in the dimensionless thermoelectric figure of merit (ZT) for the whole temperature range over all previously reported maximum values. Maximum ZT value of 0.35 was obtained at 500 °C.

  1. Development of HANARO ST3 shield

    International Nuclear Information System (INIS)

    Park, K. N.; Lee, J. S.; Shim, H. S.

    2004-12-01

    This report contains the design, fabrication and accurate installation of ST3 shield, which would be installed at ST3 beam port of HANARO. At first, we designed and fabricated ST3 shield casemate composed of 14 blocks. We filled it with heavy concrete, lead ingot and polyethylene that mixed B 4 C powder and epoxy. The average filling density of total shield casemate was 4.7g/cm 3 . The developed ST3 shield was installed at the ST3 beam port and the accuracy of installation for each beam path and channel was evaluated. We found that the extraction of neutron beam to meet the requirement of neutron spectrometer is possible. Also, we developed ancillary equipment such as BGU, quick shutter and exterior shield door for the effective opening and closing of neutron beam. As a result of this study, it was found that neutron spectrometer such as neutron reflectometer and high intensity powder diffractomater can be installed at the ST3 beam port

  2. Enhancing mid-infrared spectral response at the LaAlO3/SrTiO3 interface by magnetic field

    International Nuclear Information System (INIS)

    Feng, Xin; Zhao, Kun; Xi, Jian-Feng; Xiang, Wen-Feng; Lu, Zhi-Qing; Sun, Qi; Wu, Shi-Xiang; Ni, Hao

    2014-01-01

    Many unexpected properties have been found in the LaAlO 3 /SrTiO 3 heterostructure, but the interaction of the many ground states at its interface remains unclear. Here, we demonstrate an optical property of this n-type heterostructure where the mid-infrared spectral responsivity at the interface is enhanced by an external magnetic field. The field intensity ranged from 0.8 to 6 kOe at a low temperature (19 K) as measured with our spectral response measurement system. Two spectral peaks related to the spin-orbit coupling effect were also observed at wavelengths 2400 nm and 3700 nm. The intriguing phenomena relate to changes in the crystallographic structure and subband structure at the interface

  3. Maintenance procedures for the TITAN-I and TITAN-II reversed field pinch reactors

    International Nuclear Information System (INIS)

    Grotz, S.P.; Duggan, W.; Krakowski, R.; Najmabadi, F.; Wong, C.P.C.

    1989-01-01

    The TITAN reactor is a compact, high-power-density (neutron wall loading 18 MW/m 2 ) machine, based on the reversed-field-pinch (RFP) confinement concept. Two designs for the fusion power core have been examined: TITAN-I is based on a self-cooled lithium loop with a vanadium-alloy structure for the first wall, blanket and shield; and TITAN-II is based on an aqueous loop-in-pool design with a LiNO 3 solution as the coolant and breeder. The compact design of the TITAN fusion power core, (FPC) reduces the system to a few small and relatively low mass components, making toroidal segmentation of the FPC unnecessary. A single-piece maintenance procedure is possible. The potential advantages of single-piece maintenance procedures are: (1) Short period of down time; (2) improved reliability; (3) no adverse effects resulting from unequal levels of irradiation; and (4) ability to continually modify the FPC design. Increased availability can be expected from a fully pre-tested, single-piece FPC. Pre-testing of the FPC throughout the assembly process and prior to installation into the reactor vault is discussed. (orig.)

  4. Strontium Titanate Buffer Layers on Cu/33%Ni Substrates using a Novel Solution Chemistry

    DEFF Research Database (Denmark)

    Pallewatta, Pallewatta G A P; Yue, Zhao; Hui, Tian

    2013-01-01

    SrTiO3 is a widely studied perovskite material due to its advantages as a buffer template which can be simply applied between a metal substrate tape and a superconducting layer in 2G high temperature superconducting (HTS) tapes. In this study, heteroepitaxial SrTiO3 thin films were deposited on t...

  5. Direct evidence of superconductivity and determination of the superfluid density in buried ultrathin FeSe grown on SrTiO3

    Science.gov (United States)

    Biswas, P. K.; Salman, Z.; Song, Q.; Peng, R.; Zhang, J.; Shu, L.; Feng, D. L.; Prokscha, T.; Morenzoni, E.

    2018-05-01

    Bulk FeSe is superconducting with a critical temperature Tc≅8 K and SrTiO3 is insulating in nature, yet high-temperature superconductivity has been reported at the interface between a single-layer FeSe and SrTiO3. Angle-resolved photoemission spectroscopy and scanning tunneling microscopy measurements observe a gap opening at the Fermi surface below ≈60 K. Elucidating the microscopic properties and understanding the pairing mechanism of single-layer FeSe is of utmost importance as it is a basic building block of iron-based superconductors. Here, we use the low-energy muon spin rotation/relaxation technique to detect and quantify the supercarrier density and determine the gap symmetry in FeSe grown on SrTiO3 (100). Measurements in applied field show a temperature-dependent broadening of the field distribution below ˜60 K, reflecting the superconducting transition and formation of a vortex state. Zero-field measurements rule out the presence of magnetism of static or fluctuating origin. From the inhomogeneous field distribution, we determine an effective sheet supercarrier density ns2 D≃6 ×1014cm-2 at T →0 K, which is a factor of 4 larger than expected from ARPES measurements of the excess electron count per Fe of 1 monolayer FeSe. The temperature dependence of the superfluid density ns(T ) can be well described down to ˜10 K by simple s -wave BCS, indicating a rather clean superconducting phase with a gap of 10.2(1.1) meV. The result is a clear indication of the gradual formation of a two-dimensional vortex lattice existing over the entire large FeSe/STO interface and provides unambiguous evidence for robust superconductivity below 60 K in ultrathin FeSe.

  6. Army Research Laboratory S&T Campaign Plans 2015-2035

    Science.gov (United States)

    2014-09-01

    for micro-robotics, and high quality factor communications, electronic warfare. Efforts focus on the maturation of LEAD zirconium titanate ( PZT ) and...spectrums (multiple impact, high energy impact, and high to low cycle fatigue ) to meet the needs of current and future Army platforms and structures...MATERIALS RESEARCH CAMPAIGN’s Polymer Coatings S&T Footprint S&T AREA POSTURE Polymer Coatings LEAD Corrosion & Fatigue research explores corrosion

  7. MP3 - A Meteorology and Physical Properties Package for Titan Air-Sea Studies

    Science.gov (United States)

    Lorenz, R. D.; Stofan, E.; Lunine, J. I.; Zarnecki, J. C.; Harri, A.-M.; Karkoschka, E.; Newman, C. E.; Bierhaus, E. B.; Clark, B. C.; Yelland, M.; Leese, M. R.; Boldt, J.; Darlington, E.; Neish, C. D.; Sotzen, K.; Arvelo, J.; Rasbach, C.; Kretsch, W.; Strohbehn, K.; Grey, M.; Mann, J.; Zimmerman, H.; Reed, C.

    2012-10-01

    MP3 is a sensor suite for the proposed Titan Mare Explorer (TiME) Discovery mission to Ligeia Mare. MP3 will measure temperatures, and wind velocity, methane humidity, and pressure, as well as sea turbidity, dielectric properties, and depth via sonar.

  8. Physical characteristics and magnetic properties of BaFe12O19/SrTiO3 based composites derived from mechanical alloying

    International Nuclear Information System (INIS)

    Widodo, Rahmat Doni; Manaf, Azwar

    2016-01-01

    A composite system BaFe 12 O 19 /SrTiO 3 with ferrimagnetic BaFe 12 O 19 phase (BHF) and ferroelectric SrTiO 3 phase (STO) have been prepared by mechanical alloying and subsequent heat treatment. The composite powders were studied by Particle Size Analyze, X-ray diffraction and magnetic measurement. It was found that the particle size of composite powders initially increased due to laminated layers formation of a composite and then decreased to an asymptotic value of ∼8 µm as the milling time extended even to a relatively longer time. However, based on results of line broadening analysis the mean grain size of the particles was found in the nanometer scale. We thus believed that mechanical blending and milling of mixture components for the composite materials has promoted heterogeneous nucleation and only after successive sintering at 1100°C the milled powder transformed into particles of nanograin. In this report, microstructure as well as magnetic properties for the composite is also briefly discussed.

  9. Morphology and structural studies of WO_3 films deposited on SrTiO_3 by pulsed laser deposition

    International Nuclear Information System (INIS)

    Kalhori, Hossein; Porter, Stephen B.; Esmaeily, Amir Sajjad; Coey, Michael; Ranjbar, Mehdi; Salamati, Hadi

    2016-01-01

    Highlights: • Highly oriented WO_3 stoichiometric films were determined using pulsed laser deposition method. • Effective parameters on thin films including temperature, oxygen partial pressure and laser energy fluency was studied. • A phase transition was observed in WO_3 films at 700 °C from monoclinic to tetragonal. - Abstract: WO_3 films have been grown by pulsed laser deposition on SrTiO_3 (001) substrates. The effects of substrate temperature, oxygen partial pressure and energy fluence of the laser beam on the physical properties of the films were studied. Reflection high-energy electron diffraction (RHEED) patterns during and after growth were used to determine the surface structure and morphology. The chemical composition and crystalline phases were obtained by XPS and XRD respectively. AFM results showed that the roughness and skewness of the films depend on the substrate temperature during deposition. Optimal conditions were determined for the growth of the highly oriented films.

  10. Enhancing photocatalytic activity for hydrogen production and pollutant degradation by modifying tetragonal ZrO2 with monolayers slab surface of BiVO4, Ag3PO4, SrTiO3 and WO3: A first-principles study

    CSIR Research Space (South Africa)

    Opoku, F

    2017-10-01

    Full Text Available Semiconductor-based photocatalysis has received increasing attention in energy storage and environmental remediation process due to the abundant solar energy. For this purpose, heterostructures of ZrO2 coupled with BiVO4, Ag3PO4, SrTiO3 and WO3...

  11. First-principles investigations of electronic and magnetic properties of SrTiO3 (001) surfaces with adsorbed ethanol and acetone molecules

    Science.gov (United States)

    Adeagbo, Waheed A.; Fischer, Guntram; Hergert, Wolfram

    2011-05-01

    First-principles methods based on density functional theory are used to investigate the electronic and magnetic properties of molecular interaction of the TiO2 terminated SrTiO3 (100) surface with ethanol or acetone. Both the perfect surface and the surface with an oxygen or a titanium vacancy in the top layer are considered. Ethanol and acetone are preferentially adsorbed molecularly via their respective oxygen atom on top of the Ti atom on the perfect surface. In case of an oxygen vacancy the adsorption of ethanol or acetone occurs directly on top of the vacancy and does not significantly affect the magnetism caused by the vacancy. In the case of a titanium vacancy both adsorbates occupy positions above Ti atoms. During this adsorption process the ethanol molecule dissociates into a CH3CO radical and three hydrogen atoms. The latter form hydroxide bonds with three of the four dangling oxygen bonds around the Ti vacancy and any magnetic moment induced by the Ti vacancy is annihilated. Thus the ethanol and acetone have a different impact on the surface magnetism of the SrTiO3 (100) surface.

  12. Optical Properties of Nitrogen-Substituted Strontium Titanate Thin Films Prepared by Pulsed Laser Deposition

    Directory of Open Access Journals (Sweden)

    Alexander Wokaun

    2009-09-01

    Full Text Available Perovskite-type N-substituted SrTiO3 thin films with a preferential (001 orientation were grown by pulsed laser deposition on (001-oriented MgO and LaAlO3 substrates. Application of N2 or ammonia using a synchronized reactive gas pulse produces SrTiO3-x:Nx films with a nitrogen content of up to 4.1 at.% if prepared with the NH3 gas pulse at a substrate temperature of 720 °C. Incorporating nitrogen in SrTiO3 results in an optical absorption at 370-460 nm associated with localized N(2p orbitals. The estimated energy of these levels is ≈2.7 eV below the conduction band. In addition, the optical absorption increases gradually with increasing nitrogen content.

  13. XPS Analysis of Ni and Oxygen in Single-Sintered SrTiO3 Multifunction Ceramic

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    XPS analyses have been performed to investigate the chemical conditions of Ni and oxygen on grain surfaces in single-sintered SrTiO3 capacitor-varistor ceramic doped with Nb2O5 and NiO. It is ascertained that Ni is in form of Ni2+ ions, which substitute for Ti4+ ions on grain surfaces during the oxidizing annealing. Moreover, it is confirmed that three kinds of chemically adsorbed oxygen such as O2-, O- and O~ are formed on grain surfaces. It is proposed that these behaviors contribute greatly to the generation of multiple types of grain boundary acceptor states in the ceramic.

  14. Valence band offset of wurtzite InN/SrTiO3 heterojunction measured by x-ray photoelectron spectroscopy

    Directory of Open Access Journals (Sweden)

    Li Zhiwei

    2011-01-01

    Full Text Available Abstract The valence band offset (VBO of wurtzite indium nitride/strontium titanate (InN/SrTiO3 heterojunction has been directly measured by x-ray photoelectron spectroscopy. The VBO is determined to be 1.26 ± 0.23 eV and the conduction band offset is deduced to be 1.30 ± 0.23 eV, indicating the heterojunction has a type-I band alignment. The accurate determination of the valence and conduction band offsets paves a way to the applications of integrating InN with the functional oxide SrTiO3.

  15. Thermoelectric properties of strontium titanate superlattices incorporating niobium oxide nanolayers

    KAUST Repository

    Sarath Kumar, S. R.; Hedhili, Mohamed N.; Cha, Dong Kyu; Tritt, Terry M.; Alshareef, Husam N.

    2014-01-01

    A novel superlattice structure based on epitaxial nanoscale layers of NbOx and Nb-doped SrTiO3 is fabricated using a layer-by-layer approach on lattice matched LAO substrates. The absolute Seebeck coefficient and electrical conductivity of the [(NbOx) a/(Nb-doped SrTiO3)b]20 superlattices (SLs) were found to increase with decreasing layer thickness ratio (a/b ratio), reaching, at high temperatures, a power factor that is comparable to epitaxial Nb-doped SrTiO3 (STNO) films (∼0.7 W m-1 K-1). High temperature studies reveal that the SLs behave as n-type semiconductors and undergo an irreversible change at a varying crossover temperature that depends on the a/b ratio. By use of high resolution X-ray photoelectron spectroscopy and X-ray diffraction, the irreversible changes are identified to be due to a phase transformation from cubic NbO to orthorhombic Nb2O5, which limits the highest temperature of stable operation of the superlattice to 950 K. © 2014 American Chemical Society.

  16. Thermoelectric properties of strontium titanate superlattices incorporating niobium oxide nanolayers

    KAUST Repository

    Sarath Kumar, S. R.

    2014-04-22

    A novel superlattice structure based on epitaxial nanoscale layers of NbOx and Nb-doped SrTiO3 is fabricated using a layer-by-layer approach on lattice matched LAO substrates. The absolute Seebeck coefficient and electrical conductivity of the [(NbOx) a/(Nb-doped SrTiO3)b]20 superlattices (SLs) were found to increase with decreasing layer thickness ratio (a/b ratio), reaching, at high temperatures, a power factor that is comparable to epitaxial Nb-doped SrTiO3 (STNO) films (∼0.7 W m-1 K-1). High temperature studies reveal that the SLs behave as n-type semiconductors and undergo an irreversible change at a varying crossover temperature that depends on the a/b ratio. By use of high resolution X-ray photoelectron spectroscopy and X-ray diffraction, the irreversible changes are identified to be due to a phase transformation from cubic NbO to orthorhombic Nb2O5, which limits the highest temperature of stable operation of the superlattice to 950 K. © 2014 American Chemical Society.

  17. Strong Energy-momentum Dispersion of Phonon Dressed Carriers in the Lightly Doped Band Insulator SrTiO3

    International Nuclear Information System (INIS)

    Meevasana, Warawat

    2010-01-01

    Much progress has been made recently in the study of the effects of electron-phonon (el-ph) coupling in doped insulators using angle resolved photoemission (ARPES), yielding evidence for the dominant role of el-ph interactions in underdoped cuprates. As these studies have been limited to doped Mott insulators, the important question arises how this compares with doped band insulators where similar el-ph couplings should be at work. The archetypical case is the perovskite SrTiO 3 (STO), well known for its giant dielectric constant of 10000 at low temperature, exceeding that of La 2 CuO 4 by a factor of 500. Based on this fact, it has been suggested that doped STO should be the archetypical bipolaron superconductor. Here we report an ARPES study from high-quality surfaces of lightly doped SrTiO 3 . Comparing to lightly doped Mott insulators, we find the signatures of only moderate electron-phonon coupling: a dispersion anomaly associated with the low frequency optical phonon with a λ(prime) ∼ 0.3 and an overall bandwidth renormalization suggesting an overall λ(prime) ∼ 0.7 coming from the higher frequency phonons. Further, we find no clear signatures of the large pseudogap or small polaron phenomena. These findings demonstrate that a large dielectric constant itself is not a good indicator of el-ph coupling and highlight the unusually strong effects of the el-ph coupling in doped Mott insulators.

  18. Lead titanate nanotubes synthesized via ion-exchange method: Characteristics and formation mechanism

    International Nuclear Information System (INIS)

    Song Liang; Cao Lixin; Li Jingyu; Liu Wei; Zhang Fen; Zhu Lin; Su Ge

    2011-01-01

    Highlights: → Lead titanate nanotubes PbTi 3 O 7 were firstly synthesized by ion-exchange method. → Sodium titanate nanotubes have ion exchangeability. → Lead titanate nanotubes show a distinct red shift on absorption edge. - Abstract: A two-step method is presented for the synthesis of one dimensional lead titanate (PbTi 3 O 7 ) nanotubes. Firstly, titanate nanotubes were prepared by an alkaline hydrothermal process with TiO 2 nanopowder as precursor, and then lead titanate nanotubes were formed through an ion-exchange reaction. We found that sodium titanate nanotubes have ion exchangeability with lead ions, while protonated titanate nanotubes have not. For the first time, we distinguished the difference between sodium titanate nanotubes and protonated titanate nanotubes in the ion-exchange process, which reveals a layer space effect of nanotubes in the ion-exchange reaction. In comparison with sodium titanate, the synthesized lead titanate nanotubes show a narrowed bandgap.

  19. Surface morphology and in-plane-epitaxy of SmBa2Cu3O7-δ films on SrTiO3 (001) substrates studied by STM and grazing incidence x-ray diffraction

    DEFF Research Database (Denmark)

    Jiang, Q.D.; Smilgies, D.M.; Feidenhans'l, R.

    1996-01-01

    The surface morphology and in-plane epitaxy of thin films of SmBa(2)Cu3O(7-delta) (Sm-BCO) grown on SrTiO3 (001) substrates with various thicknesses have been investigated by scanning tunneling microscopy (STM) and grazing incidence x-ray diffraction (GIXRD). As revealed by GIXRD, SmBCO films as ...... films above h(c2), introduction of screw dislocations leads to spiral growth.......The surface morphology and in-plane epitaxy of thin films of SmBa(2)Cu3O(7-delta) (Sm-BCO) grown on SrTiO3 (001) substrates with various thicknesses have been investigated by scanning tunneling microscopy (STM) and grazing incidence x-ray diffraction (GIXRD). As revealed by GIXRD, SmBCO films...... substrate. Three different types of surface morphology were observed by STM with increasing film thickness h: a) 2D growth for hh(c2). With GIXRD, a density modulation is observed in the films with a thickness below h(c2). For thicker...

  20. Metal-insulator transition at the LaAlO3/SrTiO3 interface revisited: A hybrid functional study

    KAUST Repository

    Cossu, Fabrizio

    2013-07-17

    We investigate the electronic properties of the LaAlO3/SrTiO3 interface using density functional theory. In contrast to previous studies, which relied on (semi-)local functionals and the GGA+U method, we here use a recently developed hybrid functional to determine the electronic structure. This approach offers the distinct advantage of accessing both the metallic and insulating multilayers on a parameter-free equal footing. As compared to calculations based on semilocal GGA functionals, our hybrid functional calculations lead to a considerably increased band gap for the insulating systems. The details of the electronic structure show substantial deviations from those obtained by GGA calculations. This casts severe doubts on all previous results based on semilocal functionals. In particular, corrections using rigid band shifts (“scissors operator”) cannot lead to valid results.

  1. History and challenges of barium titanate: Part I

    Directory of Open Access Journals (Sweden)

    Vijatović M.M.

    2008-01-01

    Full Text Available Barium titanate is the first ferroelectric ceramics and a good candidate for a variety of applications due to its excellent dielectric, ferroelectric and piezoelectric properties. Barium titanate is a member of a large family of compounds with the general formula ABO3 called perovskites. Barium titanate can be prepared using different methods. The synthesis method depends on the desired characteristics for the end application. The used method has a significant influence on the structure and properties of barium titanate materials. In this review paper, Part I contains a study of the BaTiO3 structure and frequently used synthesis methods.

  2. Isotherms of ion exchange on titanates of alkaline metals

    International Nuclear Information System (INIS)

    Fillina, L.P.; Belinskaya, F.A.

    1986-01-01

    Present article is devoted to isotherms of ion exchange on titanates of alkaline metals. Therefore, finely dispersed hydrated titanates of alkaline metals (lithium, sodium, potassium) with ion exchange properties are obtained by means of alkaline hydrolysis of titanium chloride at high ph rates. Sorption of cations from salts solution of Li 2 SO 4 , NaNO 3 , Ca(NO 3 ) 2 , AgNO 3 by titanates is studied.

  3. Damage Accumulation and Recovery in Gold-Ion-Irradiated Barium Titanate

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Weilin; Weber, William J.; Thevuthasan, Suntharampillai

    2001-06-04

    Single-crystal barium titanate (BaTiO) wafers were irradiated 60? off the surface normal at 170 and 300 K using 1.0 MeV Au ions over a fluence range from 0.03 to 0.19 ions/nm. Disorder on both the Ba and Ti sublattices has been studied in situ using Rutherford backscattering spectrometry along the <110> axial direction. At these irradiation temperatures, the temperature dependence of disordering is small. The dose for amorphization under these conditions is on the order of 0.5 dpa, which is 50% of that required to amorphize SrTiO under similar conditions. At low damage levels, recovery of disorder is observed at room temperature, suggesting at least one lower temperature recovery stage. For more highly damaged states, two distinct recovery stages have been identified between 420 and 570 K and between 720 and 870 K. The recovery stage between 420 and 570 K is associated with the critical temperature for full amorphization ({approx}550 K) in BaTiO. The higher temperature recovery stage is most likely associated with epitaxial recrystallization.

  4. Hydrogen production over Au-loaded mesoporous-assembled SrTiO3 nanocrystal photocatalyst: Effects of molecular structure and chemical properties of hole scavengers

    International Nuclear Information System (INIS)

    Puangpetch, Tarawipa; Chavadej, Sumaeth; Sreethawong, Thammanoon

    2011-01-01

    Graphical abstract: Formic acid, which is the smallest and completely-dissociated water-soluble carboxylic acid, exhibited the highest hydrogen production enhancement ability over the 1 wt.% Au-loaded mesoporous-assembled SrTiO 3 nanocrystal photocatalyst. Display Omitted Research highlights: → The 1 wt.% Au-loaded mesoporous-assembled SrTiO 3 nanocrystal photocatalyst was synthesized. → The molecular structure and chemical properties of hole scavengers affected H 2 production rate. → Formic acid exhibited the highest photocatalytic H 2 production enhancement ability. -- Abstract: The hydrogen production via the photocatalytic water splitting under UV irradiation using different compounds as hole scavengers (including methanol, formic acid, acetic acid, propanoic acid, hydrochloric acid, and sulfuric acid) under a low concentration range ( 3 nanocrystal photocatalyst. The results indicated that the hydrogen production efficiency greatly depended on the molecular structure, chemical properties, and concentration of the hole scavengers. Formic acid, which is the smallest and completely-dissociated water-soluble carboxylic acid, exhibited the highest hydrogen production enhancement ability. The 2.5 vol.% aqueous formic acid solution system provided the highest photocatalytic hydrogen production rate.

  5. Application of titanates, niobates, and tantalates to neutralized defense waste decontamination: materials properties, physical forms, and regeneration techniques. Final report

    International Nuclear Information System (INIS)

    Dosch, R.G.

    1981-01-01

    A study of the application of sodium titanate (ST) to the decontamination of neutralized defense waste has been completed. The work was directed at Sr removal from dissolved salt cake, simulated in this work with a 6.0 N NaNO 3 - 0.6 N NaOH solution. Three physical forms of the titanates were developed including powder, pellets, and titanate-loaded resin beads and all were found to be superior to conventional organic ion exchange in this application. When spent, the titanate materials can be calcined to an oxide from which is a stable waste form in itself or can be added directly to a glass melter to become part of a vitrified waste form. Radiation stability of titanate powder and resin forms was assessed in tests in which these materials were exposed to 60 Co radiation. The strontium exchange capacity of the powder remained constant through a dose of 3 x 10 7 rads and retained 50% capacity after a dose of 2 x 10 9 rads. The primary mechanism involved in loss of capacity was believed to be heating associated with the irradiation. The resin forms were unchanged through a dose of 5 x 10 8 rads and retained 30% capacity after a dose of 2 x 10 9 rads. The latter dose resulted in visible degradation of the resin matrix. Anion exchange resins loaded with sodium niobate and sodium tantalate were also prepared by similar methods and evaluated for this application. These materials had Sr sorption properties comparable to the titanate material; however, they would have to provide a significant improvement to justify their higher cost

  6. Thickness-dependent resistance switching in Cr-doped SrTiO3

    Science.gov (United States)

    Kim, TaeKwang; Du, Hyewon; Kim, Minchang; Seo, Sunae; Hwang, Inrok; Kim, Yeonsoo; Jeon, Jihoon; Lee, Sangik; Park, Baeho

    2012-09-01

    The thickness-dependent bipolar resistance-switching behavior was investigated for epitaxiallygrown Cr-doped SrTiO3 (Cr-STO). All the pristine devices of different thickness showed polarity-independent symmetric current-voltage characteristic and the same space-charge-limited conduction mechanism. However, after a forming process, the resultant conduction and switching phenomena were significantly different depending on the thickness of Cr-STO. The forming process itself was highly influenced by resistance value of each pristine device. Based on our results, we suggest that the resistance-switching mechanism in Cr-STO depends not only on the insulating material's composition or the contact metal as previously reported but also on the initial resistance level determined by the geometry and the quality of the insulating material. The bipolar resistance-switching behaviors in oxide materials of different thicknesses exhibit mixed bulk and interface switching. This indicates that efforts in resistance-based memory research should be focused on scalability or process method to control a given oxide material in addition to material type and device structure.

  7. Carrier density independent scattering rate in SrTiO3-based electron liquids.

    Science.gov (United States)

    Mikheev, Evgeny; Raghavan, Santosh; Zhang, Jack Y; Marshall, Patrick B; Kajdos, Adam P; Balents, Leon; Stemmer, Susanne

    2016-02-10

    We examine the carrier density dependence of the scattering rate in two- and three-dimensional electron liquids in SrTiO3 in the regime where it scales with T(n) (T is the temperature and n ≤ 2) in the cases when it is varied by electrostatic control and chemical doping, respectively. It is shown that the scattering rate is independent of the carrier density. This is contrary to the expectations from Landau Fermi liquid theory, where the scattering rate scales inversely with the Fermi energy (EF). We discuss that the behavior is very similar to systems traditionally identified as non-Fermi liquids (n density-independent scattering rates have been observed. The results indicate that the applicability of Fermi liquid theory should be questioned for a much broader range of correlated materials and point to the need for a unified theory.

  8. Full Ceramic Fuel Cells Based on Strontium Titanate Anodes, An Approach Towards More Robust SOFCs

    DEFF Research Database (Denmark)

    Holtappels, Peter; Irvine, J.T.S.; Iwanschitz, B.

    2013-01-01

    The persistent problems with Ni-YSZ cermet based SOFCs, with respect to redox stability and tolerance towards sulfur has stimulated the development of a full ceramic cell based on strontium titanate(ST)- based anodes and anode support materials, within the EU FCH JU project SCOTAS-SOFC. Three...

  9. Barium titanate coated with magnesium titanate via fused salt method and its dielectric property

    International Nuclear Information System (INIS)

    Chen Renzheng; Cui Aili; Wang Xiaohui; Li Longtu

    2003-01-01

    Barium titanate fine particles were coated homogeneously with magnesium titanate via the fused salt method. The thickness of the magnesium titanate film is 20 nm, as verified by TEM and XRD. The mechanism of the coating is that: when magnesium chloride is liquated in 800 deg. C, magnesium will replace barium in barium titanate, and form magnesium titanate film on the surface of barium titanate particles. Ceramics sintered from the coated particles show improved high frequency ability. The dielectric constant is about 130 at the frequency from 1 to 800 MHz

  10. Coupled atmosphere-ocean models of Titan's past

    Science.gov (United States)

    Mckay, Christopher P.; Pollack, James B.; Lunine, Jonathan I.; Courtin, Regis

    1993-01-01

    The behavior and possible past evolution of fully coupled atmosphere and ocean model of Titan are investigated. It is found that Titan's surface temperature was about 20 K cooler at 4 Gyr ago and will be about 5 K warmer 0.5 Gyr in the future. The change in solar luminosity and the conversion of oceanic CH4 to C2H6 drive the evolution of the ocean and atmosphere over time. Titan appears to have experienced a frozen epoch about 3 Gyr ago independent of whether an ocean is present or not. This finding may have important implications for understanding the inventory of Titan's volatile compounds.

  11. Bright white upconversion luminescence from Er3+/Tm3+/Yb3+-doped titanate-based glasses prepared by aerodynamic levitation method

    Science.gov (United States)

    Zhang, Minghui; Yu, Jianding; Jiang, Wan; Liu, Yan; Ai, Fei; Wen, Haiqin; Jiang, Meng; Yu, Huimei; Pan, Xiuhong; Tang, Meibo; Gai, Lijun

    2017-10-01

    Aerodynamic levitation method was employed to prepare Er3+/Tm3+/Yb3+-doped titanate-based glasses. DTA results show that the glass performs high thermal stability with the glass transition temperature of 799 °C. The interaction among rare earth ions has been discussed by adjusting the relative concentration. Er3+ ions can quench the upconversion luminescence of Tm3+ ions. Tm3+ ions play a strong role in quenching the emissions of Er3+ and Tm3+ when the content of Tm3+ ions is greater than or equal 0.05. From the view of the ratio of red emission to green emission, Tm3+ ions can improve the red emission of Er3+ ions to some extent in contrast with the green emissions of Er3+ ions. 980 nm incident laser can be efficiently absorbed by Yb3+ ions. The relative intensity of red, green, and blue upconversion luminescence has been tuned to obtain white light. The composition with white upconversion luminescence of the color coordinate (0.291, 0.3292) has been found. Moreover, white upconversion luminescence mechanism is a two-photon process of ET, ESA, and cooperative sensitization. Rare earth ions doped titanate-based glasses with bright upconversion luminescence perform potential applications in color display, back light, et al.

  12. Titan's Radioactive Haze : Production and Fate of Radiocarbon On Titan

    Science.gov (United States)

    Lorenz, R. D.; Jull, A. J. T.; Swindle, T. D.; Lunine, J. I.

    Just as cosmic rays interact with nitrogen atoms in the atmosphere of Earth to gener- ate radiocarbon (14C), the same process should occur in Titan`s nitrogen-rich atmo- sphere. Titan`s atmosphere is thick enough that cosmic ray flux, rather than nitrogen column depth, limits the production of 14 C. Absence of a strong magnetic field and the increased distance from the sun suggest production rates of 9 atom/cm2/s, approx- imately 4 times higher than Earth. On Earth the carbon is rapidly oxidised into CO2. The fate and detectability of 14C on Titan depends on the chemical species into which it is incorporated in Titan's reducing atmosphere : as methane it would be hopelessly diluted even in only the atmosphere (ignoring the other, much more massive carbon reservoirs likely to be present on Titan, like hydrocarbon lakes.) However, in the more likely case that the 14C attaches to the haze that rains out onto the surface (as tholin, HCN or acetylene and their polymers - a much smaller carbon reservoir) , haze in the atmosphere or recently deposited on the surface would therefore be quite intrinsically radioactive. Such activity may modify the haze electrical charging and hence its coag- ulation. Measurements with compact instrumentation on future in-situ missions could place useful constraints on the mass deposition rates of photochemical material on the surface and identify locations where surface deposits of such material are `freshest`.

  13. Tunable magnetism in the LaAlO3/SrTiO3 heterostructure: Insights from first-principles calculations

    Science.gov (United States)

    Xue, Yuanbin; Zhao, Jinzhu; Shan, Yueyue; Xu, Hu

    2018-04-01

    By performing first-principles calculations, we explored the origin and controlling methods of magnetism in ideal and oxygen deficient (001) LaAlO3/SrTiO3 (LAO/STO) heterostructures. It was found that the ferromagnetic ordering is the ground state and that the interfacial Ti 3d electrons introduced by the LaO-termination, polar catastrophe and oxygen vacancies can all contribute to the magnetism. With respect to the ways of tuning the magnetic properties, our results show that LaO-terminated films generally carry much stronger magnetic moments than their AlO2-terminated counterparts and that the magnitude of magnetic moments can also be effectively controlled by the LAO film thickness. In addition, oxygen vacancy leads to substantial electronic reconstruction of the interfacial Ti 3d orbitals, which enhances the magnetization and makes the magnetism emerge in thinner polar LAO films. This work offers useful information to facilitate one's understanding of the magnetism and to provide clues to engineer the magnetic behaviors in related oxide heterostructures.

  14. Thickness dependent charge transport in ferroelectric BaTiO3 heterojunctions

    Science.gov (United States)

    Singh, Pooja; Rout, P. K.; Singh, Manju; Rakshit, R. K.; Dogra, Anjana

    2015-09-01

    We have investigated the effect of ferroelectric barium titanate (BaTiO3) film thickness on the charge transport mechanism in pulsed laser deposited epitaxial metal-ferroelectric semiconductor junctions. The current (I)-voltage (V) measurements across the junctions comprising of 20-500 nm thick BaTiO3 and conducting bottom electrode (Nb: SrTiO3 substrate or La2/3Ca1/3MnO3 buffer layer) demonstrate the space charge limited conduction. Further analysis indicates a reduction in the ratio of free to trapped carriers with increasing thickness in spite of decreasing trap density. Such behaviour arises the deepening of the shallow trap levels (I-V curves implies a bipolar resistive switching behaviour, which can be explained in terms of charge trapping and de-trapping process.

  15. Critical thickness and strain relaxation in molecular beam epitaxy-grown SrTiO3 films

    International Nuclear Information System (INIS)

    Wang, Tianqi; Ganguly, Koustav; Marshall, Patrick; Xu, Peng; Jalan, Bharat

    2013-01-01

    We report on the study of the critical thickness and the strain relaxation in epitaxial SrTiO 3 film grown on (La 0.3 Sr 0.7 )(Al 0.65 Ta 0.35 )O 3 (001) (LSAT) substrate using the hybrid molecular beam epitaxy approach. No change in the film's lattice parameter (both the in-plane and the out-of-plane) was observed up to a film thickness of 180 nm, which is in sharp contrast to the theoretical critical thickness of ∼12 nm calculated using the equilibrium theory of strain relaxation. For film thicknesses greater than 180 nm, the out-of-plane lattice parameter was found to decrease hyperbolically in an excellent agreement with the relaxation via forming misfit dislocations. Possible mechanisms are discussed by which the elastic strain energy can be accommodated prior to forming misfit dislocations leading to such anomalously large critical thickness

  16. Instability of the layered orthorhombic post-perovskite phase of SrTiO3 and other candidate orthorhombic phases under pressure

    Science.gov (United States)

    Bhandari, Churna; Lambrecht, Walter R. L.

    2018-06-01

    While the tetragonal antiferro-electrically distorted (AFD) phase with space group I 4 / mcm is well known for SrTiO3 to occur below 105 K, there are also some hints in the literature of an orthorhombic phase, either at the lower temperature or at high pressure. A previously proposed orthorhombic layered structure of SrTiO3, known as the post-perovskite or CaIrO3 structure with space group Cmcm is shown to have significantly higher energy than the cubic or tetragonal phase and to have its minimum volume at larger volume than cubic perovskite. The Cmcm structure is thus ruled out. We also study an alternative Pnma phase obtained by two octahedral rotations about different axes. This phase is found to have slightly lower energy than the I 4 / mcm phase in spite of the fact that its parent, in-phase tilted P 4 / mbm phase is not found to occur. Our calculated enthalpies of formation show that the I 4 / mcm phase occurs at slightly higher volume than the cubic phase and has a negative transition pressure relative to the cubic phase, which suggests that it does not correspond to the high-pressure tetragonal phase. The enthalpy of the Pnma phase is almost indistinguishable from the I 4 / mcm phase. Alternative ferro-electric tetragonal and orthorhombic structures previously suggested in literature are discussed.

  17. Configuration and local elastic interaction of ferroelectric domains and misfit dislocation in PbTiO3/SrTiO3 epitaxial thin films

    Directory of Open Access Journals (Sweden)

    Takanori Kiguchi, Kenta Aoyagi, Yoshitaka Ehara, Hiroshi Funakubo, Tomoaki Yamada, Noritaka Usami and Toyohiko J Konno

    2011-01-01

    Full Text Available We have studied the strain field around the 90° domains and misfit dislocations in PbTiO3/SrTiO3 (001 epitaxial thin films, at the nanoscale, using the geometric phase analysis (GPA combined with high-resolution transmission electron microscopy (HRTEM and high-angle annular dark field––scanning transmission electron microscopy (HAADF-STEM. The films typically contain a combination of a/c-mixed domains and misfit dislocations. The PbTiO3 layer was composed from the two types of the a-domain (90° domain: a typical a/c-mixed domain configuration where a-domains are 20–30 nm wide and nano sized domains with a width of about 3 nm. In the latter case, the nano sized a-domain does not contact the film/substrate interface; it remains far from the interface and stems from the misfit dislocation. Strain maps obtained from the GPA of HRTEM images show the elastic interaction between the a-domain and the dislocations. The normal strain field and lattice rotation match each other between them. Strain maps reveal that the a-domain nucleation takes place at the misfit dislocation. The lattice rotation around the misfit dislocation triggers the nucleation of the a-domain; the normal strains around the misfit dislocation relax the residual strain in a-domain; then, the a-domain growth takes place, accompanying the introduction of the additional dislocation perpendicular to the misfit dislocation and the dissociation of the dislocations into two pairs of partial dislocations with an APB, which is the bottom boundary of the a-domain. The novel mechanism of the nucleation and growth of 90° domain in PbTiO3/SrTiO3 epitaxial system has been proposed based on above the results.

  18. Epitaxial growth of Co(0 0 0 1)hcp/Fe(1 1 0)bcc magnetic bi-layer films on SrTiO3(1 1 1) substrates

    International Nuclear Information System (INIS)

    Ohtake, Mitsuru; Shikada, Kouhei; Kirino, Fumiyoshi; Futamoto, Masaaki

    2008-01-01

    Co(0 0 0 1) hcp /Fe(1 1 0) bcc epitaxial magnetic bi-layer films were successfully prepared on SrTiO 3 (1 1 1) substrates. The crystallographic properties of Co/Fe epitaxial magnetic bi-layer films were investigated. Fe(1 1 0) bcc soft magnetic layer grew epitaxially on SrTiO 3 (1 1 1) substrate with two type variants, Nishiyama-Wasserman and Kurdjumov-Sachs relationships. An hcp-Co single-crystal layer is obtained on Ru(0 0 0 1) hcp interlayer, while hcp-Co layer formed on Au(1 1 1) fcc or Ag(1 1 1) fcc interlayer is strained and may involve fcc-Co phase. It has been shown possible to prepare Co/Fe epitaxial magnetic bi-layer films which can be usable for patterned media application

  19. Correlation between atomic structure and magnetic properties of La0.7Ca0.3MnO3 thin films grown on SrTiO3 (1 0 0)

    International Nuclear Information System (INIS)

    Rubio-Zuazo, J.; Andres, A. de; Taboada, S.; Prieto, C.; Martinez, J.L.; Castro, G.R.

    2005-01-01

    The crystallographic structure of La 0.7 Ca 0.3 MnO 3 (LCMO) ultra-thin films grown on SrTiO 3 (0 0 1) has been investigated by surface X-ray diffraction (SXD) and the correlation between their transport and magnetic properties and crystallographic structure is discussed. LCMO thin films in a thickness range between 2.4 and 27 nm were grown by DC-sputtering on SrTiO 3 (0 0 1). We distinguish two different crystallographic structures associated to the 2.4 and 27 nm thin films, respectively. The 27 nm film structure corresponds to a tetragonal perovskite (space group Pbnm), as has been reported for bulk LCMO. For the 2.4 nm film the La/Ca ions are located at the regular position of an ideal perovskite and the MnO 6 octahedrons are aligned along the c-axis. The MnO 2 stacking layer (basal plane) is distorted and coplanar to the a-b crystallographic axis with an anti-correlation between octahedron layers. This observed distortion is not compatible with the Pbnm space group. The new phase, which cannot be excluded to coexist at the interface of thicker films, can be described, as an example, through an I4/mcm or Pbcn space group. Based on the observed structure, plausible models to explain their transport and magnetic behaviour are proposed. For the 2.4 nm film, an octahedron in-plane (basal plane) distortion induced by the substrate is observed. Thicker films behave structurally and magnetically as bulk-like materials

  20. Titan Casts Revealing Shadow

    Science.gov (United States)

    2004-05-01

    A rare celestial event was captured by NASA's Chandra X-ray Observatory as Titan -- Saturn's largest moon and the only moon in the Solar System with a thick atmosphere -- crossed in front of the X-ray bright Crab Nebula. The X-ray shadow cast by Titan allowed astronomers to make the first X-ray measurement of the extent of its atmosphere. On January 5, 2003, Titan transited the Crab Nebula, the remnant of a supernova explosion that was observed to occur in the year 1054. Although Saturn and Titan pass within a few degrees of the Crab Nebula every 30 years, they rarely pass directly in front of it. "This may have been the first transit of the Crab Nebula by Titan since the birth of the Crab Nebula," said Koji Mori of Pennsylvania State University in University Park, and lead author on an Astrophysical Journal paper describing these results. "The next similar conjunction will take place in the year 2267, so this was truly a once in a lifetime event." Animation of Titan's Shadow on Crab Nebula Animation of Titan's Shadow on Crab Nebula Chandra's observation revealed that the diameter of the X-ray shadow cast by Titan was larger than the diameter of its solid surface. The difference in diameters gives a measurement of about 550 miles (880 kilometers) for the height of the X-ray absorbing region of Titan's atmosphere. The extent of the upper atmosphere is consistent with, or slightly (10-15%) larger, than that implied by Voyager I observations made at radio, infrared, and ultraviolet wavelengths in 1980. "Saturn was about 5% closer to the Sun in 2003, so increased solar heating of Titan may account for some of this atmospheric expansion," said Hiroshi Tsunemi of Osaka University in Japan, one of the coauthors on the paper. The X-ray brightness and extent of the Crab Nebula made it possible to study the tiny X-ray shadow cast by Titan during its transit. By using Chandra to precisely track Titan's position, astronomers were able to measure a shadow one arcsecond in

  1. Radiation effects in uranium-niobium titanates

    International Nuclear Information System (INIS)

    Lian, J.; Wang, S.X.; Wang, L.M.; Ewing, R.C.

    2000-01-01

    Pyrochlore is an important actinide host phase proposed for the immobilization of high level nuclear wastes and excess weapon plutonium.[1] Synthetic pyrochlore has a great variety of chemical compositions due to the possibility of extensive substitutions in the pyrochlore structure.[2] During the synthesis of pyrochlore, additional complex titanate phases may form in small quantities. The response of these phases to radiation damage must be evaluated because volume expansion of minor phases may cause micro-fracturing. In this work, two complex uranium-niobium titanates, U 3 NbO 9.8 (U-rich titanate) and Nb 3 UO 10 (Nb-rich titanate) were synthesized by the alkoxide/nitrate route at 1300 deg. C under an argon atmosphere. The phase composition and structure were analyzed by EDS, BSE, XRD, EMPA and TEM techniques. An 800 KeVKr 2+ irradiation was performed using the IVEM-Tandem Facility at Argonne National Laboratory in a temperature range from 30 K to 973 K. The radiation effects were observed by in situ TEM

  2. Mechanical control of magnetism in oxygen deficient perovskite SrTiO3.

    Science.gov (United States)

    Zhang, Yajun; Wang, Jie; Sahoo, M P K; Shimada, Takahiro; Kitamura, Takayuki

    2015-10-28

    Mechanical control of magnetism in perovskite oxides is an important and promising approach in spintronics. Based on the first-principles calculations, we demonstrate that a negative pressure leads to a great enhancement of magnetic moment in deficient SrTiO3 with oxygen vacancies, whereas a positive pressure results in the gradual disappearance of magnetism. Spin charge density, Bader charge analysis and electronic density of states successfully elucidate the origin and underlying physics of the enhancement and disappearance of magnetism. It is found that the split electronic states of dz(2), dyz and dzx in the 3d orbitals of Ti atoms remarkably contribute to the occupancy of majority spin states under negative pressure, which induces a large magnetic moment. Under positive pressure, however, the equal occupancy of both majority and minority t2g and eg states leads to the disappearance of magnetization. In addition, both negative and positive pressures can largely lower the vacancy formation enthalpy, suggesting that the oxygen vacancy is preferable with pressure. Our findings may provide a mechanism to achieve the pressure control of magnetization in nonmagnetic perovskite oxides.

  3. O deficient LaAlO3/SrTiO3(110) and (001) superlattices under hydrostatic pressure: a comparative first principles study

    KAUST Repository

    Albar, Arwa; Schwingenschlö gl, Udo

    2017-01-01

    We compare the electronic properties of O deficient LaAlO3/SrTiO3 superlattices oriented along the (001) and (110) directions, taking into account the effect of hydrostatic compression and tension. Interfacial O vacancies turn out to be less likely in the case of the (110) orientation, with compression (tension) reducing (enhancing) the energy cost for both orientations. The presence of O vacancies results in the formation of a two-dimensional electron gas, for which we observe a distinct spatial pattern of carrier density that depends strongly on the amount of applied pressure. We clarify the interrelation between structural features and the properties of this electron gas (confinement, carrier density, and mobility).

  4. O deficient LaAlO3/SrTiO3(110) and (001) superlattices under hydrostatic pressure: a comparative first principles study

    KAUST Repository

    Albar, Arwa

    2017-03-17

    We compare the electronic properties of O deficient LaAlO3/SrTiO3 superlattices oriented along the (001) and (110) directions, taking into account the effect of hydrostatic compression and tension. Interfacial O vacancies turn out to be less likely in the case of the (110) orientation, with compression (tension) reducing (enhancing) the energy cost for both orientations. The presence of O vacancies results in the formation of a two-dimensional electron gas, for which we observe a distinct spatial pattern of carrier density that depends strongly on the amount of applied pressure. We clarify the interrelation between structural features and the properties of this electron gas (confinement, carrier density, and mobility).

  5. Microstructure and dielectric properties of La2O3 doped Ti-rich barium strontium titanate ceramics for capacitor applications

    Directory of Open Access Journals (Sweden)

    Zhang Chen

    2018-03-01

    Full Text Available Microstructure and dielectric properties of La2O3 doped Ti-rich barium strontium titanate ceramics, prepared by solid state method, were investigated with non-stoichiometric level and various La2O3 content, using XRD, SEM and LCR measuring system. With an increase of non-stoichiometric level, the unit cell volumes of perovskite lattices for the single phase Ti-rich barium strontium titanate ceramics increased due to the decreasing A site vacancy concentration V″A. The unit cell volume increased and then decreased slightly with the increasing La2O3 content. Relatively high non-stoichiometric level and high La2O3 content in Ti-rich barium strontium titanate ceramics contributed to the decreased average grain size as well as fine grain size distribution, which correspondingly improved the temperature stability of the relative dielectric constant. The relative dielectric constant єrRT, dielectric loss tanδRT and the maximum relative dielectric constant єrmax decreased and then increased with the increasing non-stoichiometric level. With the increase of La2O3 doping content, the relative dielectric constant єrRT increased initially and then decreased. The maximum relative dielectric constant єrmax can be increased by applying low doping content of La2O3 in Ti-rich barium strontium titanate ceramics due to the increased spontaneous polarization.

  6. Chemical investigation of Titan and Triton tholins

    Science.gov (United States)

    Mcdonald, Gene D.; Thompson, W. R.; Heinrich, Michael; Khare, Bishun N.; Sagan, Carl

    1994-01-01

    We report chromatographic and spectroscopic analyses of both Titan and Triton tholins, organic solids made from the plasma irradiation of 0.9:0.1 and 0.999:0.001 N2/CH4 gas mixtures, respectively. The lower CH4 mixing ratio leads to a nitrogen-richer tholin (N/C greater than 1), probably including nitrogen heterocyclic compounds. Unlike Titan tholin, bulk Triton tholin is poor in nitriles. From high-pressure liquid chromatography, ultraviolet and infrared spectroscopy, and molecular weight estimation by gel filtration chromatography, we conclude that (1) several H2O-soluble fractions, each with distinct UV and IR spectral signatures, are present, (2) these fractions are not identical in the two tholins, (3) the H2O-soluble fractions of Titan tholins do not contain significant amounts of nitriles, despite the major role of nitriles in bulk Titan tholin, and (4) the H2O-soluble fractions of both tholins are mainly molcules containing about 10 to 50 (C + N) atoms. We report yields of amino acids upon hydrolysis of Titan and Triton tholins. Titan tholin is largely insoluble in the putative hydrocarbon lakes or oceans on Titan, but can yield the H2O-soluble species investigated here upon contact with transient (e.g., impact-generated) liquid water.

  7. Titan's geoid and hydrology: implications for Titan's geological evolution

    Science.gov (United States)

    Sotin, Christophe; Seignovert, Benoit; Lawrence, Kenneth; MacKenzie, Shannon; Barnes, Jason; Brown, Robert

    2014-05-01

    A 1x1 degree altitude map of Titan is constructed from the degree 4 gravity potential [1] and Titan's shape [2] determined by the Radio Science measurements and RADAR observations of the Cassini mission. The amplitude of the latitudinal altitude variations is equal to 300 m compared to 600 m for the amplitude of the latitudinal shape variations. The two polar caps form marked depressions with an abrupt change in topography at exactly 60 degrees at both caps. Three models are envisaged to explain the low altitude of the polar caps: (i) thinner ice crust due to higher heat flux at the poles, (ii) fossil shape acquired if Titan had higher spin rate in the past, and (iii) subsidence of the crust following the formation of a denser layer of clathrates as ethane rain reacts with the H2O ice crust [3]. The later model is favored because of the strong correlation between the location of the cloud system during the winter season and the latitude of the abrupt change in altitude. Low altitude polar caps would be the place where liquids would run to and eventually form large seas. Indeed, the large seas of Titan are found at the deepest locations at the North Pole. However, the lakes and terrains considered to be evaporite candidates due to their spectral characteristics in the infrared [4,5] seem to be perched. Lakes may have been filled during Titan's winter and then slowly evaporated leaving material on the surface. Interestingly, the largest evaporite deposits are located at the equator in a deep depression 150 m below the altitude of the northern seas. This observation seems to rule out the presence of a global subsurface hydrocarbon reservoir unless the evaporation rate at the equator is faster than the transport of fluids from the North Pole to the equator. This work has been performed at the Jet Propulsion Laboratory, California Institute of Technology, under contract to NASA. [1] Iess L. et al. (2012) Science, doi 10.1126/science.1219631. [2] Lorenz R.D. (2013

  8. Structural and thermal characterization of La5Ca9Cu24O41 thin films grown by pulsed laser deposition on (1 1 0) SrTiO3 substrates

    International Nuclear Information System (INIS)

    Svoukis, E.; Athanasopoulos, G.I.; Altantzis, Th.; Lioutas, Ch.; Martin, R.S.; Revcolevschi, A.; Giapintzakis, J.

    2012-01-01

    In the present study stoichiometric, b-axis oriented La 5 Ca 9 Cu 24 O 41 thin films were grown by pulsed laser deposition on (1 1 0) SrTiO 3 substrates in the temperature range 600–750 °C. High resolution transmission electron microscopy was employed to investigate the growth mechanism and the epitaxial relationship between the SrTiO 3 substrates and the La 5 Ca 9 Cu 24 O 41 films grown at 700 °C. The 3-ω method was used to measure the cross-plane thermal conductivity of La 5 Ca 9 Cu 24 O 41 films in the temperature range 50–350 K. The observed glass-like behavior is attributed to atomic-scale defects, grain boundaries and an interfacial layer formed between film and substrate.

  9. Spin-Orbit Interaction and Kondo Scattering at the PrAlO3/SrTiO3 Interface

    Science.gov (United States)

    Mozaffari, Shirin; Guchhait, Samaresh; Markert, John

    We have investigated the effect of oxygen content, in the PO2 range of 6 ×10-6 - 1 ×10-3 torr, on the spin-orbit (SO) interaction at PrAlO3/SrTiO3 interface. The most-conducting 2-D-like PrAlO3 interfaces were not as conducting as comparable LaAlO3 samples, indicating either a steric or mixed-valent effect. The least-conducting, most oxygenated PrAlO3 interface exhibits hole conductivity, a departure from the typical electron-doped behavior. For 10-5 and 10-4 torr samples, high-temperature metallic behavior is accompanied by an upturn in resistivity at low temperatures, consistent with Kondo scattering theory; analysis gives a Kondo temperature 17 K. The magnetoresistance (MR) for the low PO2-grown samples was modeled with a positive part due to weak anti-localization (WAL) from a strong SO interaction, and a negative part due to the Kondo effect. The variation of MR suggests a strong SO interaction for the 10-5 torr sample with HSO = 1.25 T in both field orientations. The WAL effect is smaller for higher PO2-grown samples, where the high-field MR is dominated by the Kondo effect.

  10. Large thermoelectric power factor in Pr-doped SrTiO3-δ ceramics via grain-boundary-induced mobility enhancement

    KAUST Repository

    Mehdizadeh Dehkordi, Arash

    2014-04-08

    We report a novel synthesis strategy to prepare high-performance bulk polycrystalline Pr-doped SrTiO3 ceramics. A large thermoelectric power factor of 1.3 W m-1 K-1 at 500 °C is achieved in these samples. In-depth investigations of the electronic transport and microstructure suggest that this significant improvement results from a substantial enhancement in carrier mobility originating from the formation of Pr-rich grain boundaries. This work provides new directions to higher performance oxide thermoelectrics as well as possibly other properties and applications of this broadly functional perovskite material. © 2014 American Chemical Society.

  11. Large thermoelectric power factor in Pr-doped SrTiO3-δ ceramics via grain-boundary-induced mobility enhancement

    KAUST Repository

    Mehdizadeh Dehkordi, Arash; Bhattacharya, Sriparna K.; Darroudi, Taghi; Graff, Jennifer W.; Schwingenschlö gl, Udo; Alshareef, Husam N.; Tritt, Terry M.

    2014-01-01

    We report a novel synthesis strategy to prepare high-performance bulk polycrystalline Pr-doped SrTiO3 ceramics. A large thermoelectric power factor of 1.3 W m-1 K-1 at 500 °C is achieved in these samples. In-depth investigations of the electronic transport and microstructure suggest that this significant improvement results from a substantial enhancement in carrier mobility originating from the formation of Pr-rich grain boundaries. This work provides new directions to higher performance oxide thermoelectrics as well as possibly other properties and applications of this broadly functional perovskite material. © 2014 American Chemical Society.

  12. Characterizing the Upper Atmosphere of Titan using the Titan Global Ionosphere- Thermosphere Model: Nitrogen and Methane.

    Science.gov (United States)

    Bell, J. M.; Waite, J. H.; Bar-Nun, A.; Bougher, S. W.; Ridley, A. J.; Magee, B.

    2008-12-01

    Recently, a great deal of effort has been put forth to explain the Cassini Ion-Neutral Mass Spectrometer (Waite et al [2004]) in-situ measurements of Titan's upper atmosphere (e.g. Muller-Wodarg [2008], Strobel [2008], Yelle et al [2008]). Currently, the community seems to agree that large amounts of CH4 are escaping from Titan's upper atmosphere at a rate of roughly 2.0 x 1027 molecules of CH4/s (3.33 x 1028 amu/s), representing a significant mass source to the Kronian Magnetosphere. However, such large escape fluxes from Titan are currently not corroborated by measurements onboard the Cassini Spacecraft. Thus, we posit another potential scenario: Aerosol depletion of atmospheric methane. Using the three-dimensional Titan Global Ionosphere-Thermosphere Model (T-GITM) (Bell et al [2008]), we explore the possible removal mechanisms of atmospheric gaseous constituents by these aerosols. Titan simulations are directly compared against Cassini Ion-Neutral Mass Spectrometer in-situ densities of N2 and CH4. From this work, we can then compare and contrast this aerosol depletion scenario against the currently posited hydrodynamic escape scenario, illustrating the merits and shortcomings of both.

  13. The surface structure of SrTiO3 at high temperatures under influence of oxygen

    International Nuclear Information System (INIS)

    Hesselberth, M. B. S.; Molen, S. J. van der; Aarts, J.

    2014-01-01

    We use low energy electron microscopy to investigate the structure of the SrTiO 3 (001) surface at elevated temperatures and different oxygen pressures. Upon varying the temperature between 500 °C and 900 °C in oxygen pressures ranging from 10 −9 millibar to 10 −4 millibar, two surface transitions are found to be present. The lower temperature (1 × 1) → (2 × 1) transition that is known to occur in ultrahigh vacuum can be reversed by increasing the oxygen pressure. At higher temperatures, we observe a (2 × 1) → disordered (1 × 1) transition which is irreversible in the experimental parameter range. The observations are expected to have a strong bearing on the growth of interface structures

  14. Giant Negative Magnetoresistance Driven by Spin-Orbit Coupling at the LaAlO3/SrTiO3 Interface.

    Science.gov (United States)

    Diez, M; Monteiro, A M R V L; Mattoni, G; Cobanera, E; Hyart, T; Mulazimoglu, E; Bovenzi, N; Beenakker, C W J; Caviglia, A D

    2015-07-03

    The LaAlO3/SrTiO3 interface hosts a two-dimensional electron system that is unusually sensitive to the application of an in-plane magnetic field. Low-temperature experiments have revealed a giant negative magnetoresistance (dropping by 70%), attributed to a magnetic-field induced transition between interacting phases of conduction electrons with Kondo-screened magnetic impurities. Here we report on experiments over a broad temperature range, showing the persistence of the magnetoresistance up to the 20 K range--indicative of a single-particle mechanism. Motivated by a striking correspondence between the temperature and carrier density dependence of our magnetoresistance measurements we propose an alternative explanation. Working in the framework of semiclassical Boltzmann transport theory we demonstrate that the combination of spin-orbit coupling and scattering from finite-range impurities can explain the observed magnitude of the negative magnetoresistance, as well as the temperature and electron density dependence.

  15. Probing charge transfer during metal-insulator transitions in graphene-LaAlO3/SrTiO3 systems

    Science.gov (United States)

    Aliaj, I.; Sambri, A.; Miseikis, V.; Stornaiuolo, D.; di Gennaro, E.; Coletti, C.; Pellegrini, V.; Miletto Granozio, F.; Roddaro, S.

    2018-06-01

    Two-dimensional electron systems (2DESs) at the interface between LaAlO3 (LAO) and SrTiO3 (STO) perovskite oxides display a wide class of tunable phenomena ranging from superconductivity to metal-insulator transitions. Most of these effects are strongly sensitive to surface physics and often involve charge transfer mechanisms, which are, however, hard to detect. In this work, we realize hybrid field-effect devices where graphene is used to modulate the transport properties of the LAO/STO 2DES. Different from a conventional gate, graphene is semimetallic and allows us to probe charge transfer with the oxide structure underneath the field-effect electrode. In LAO/STO samples with a low initial carrier density, graphene-covered regions turn insulating when the temperature is lowered to 3 K, but conduction can be restored in the oxide structure by increasing the temperature or by field effect. The evolution of graphene's electron density is found to be inconsistent with a depletion of LAO/STO, but it rather points to a localization of interfacial carriers in the oxide structure.

  16. AVIATR - Aerial Vehicle for In-situ and Airborne Titan Reconnaissance A Titan Airplane Mission Concept

    Science.gov (United States)

    Barnes, Jason W.; Lemke, Lawrence; Foch, Rick; McKay, Christopher P.; Beyer, Ross A.; Radebaugh, Jani; Atkinson, David H.; Lorenz, Ralph D.; LeMouelic, Stephane; Rodriguez, Sebastien; hide

    2011-01-01

    We describe a mission concept for a stand-alone Titan airplane mission: Aerial Vehicle for In-situ and Airborne Titan Reconnaissance (AVIATR). With independent delivery and direct-to-Earth communications, AVIATR could contribute to Titan science either alone or as part of a sustained Titan Exploration Program. As a focused mission, AVIATR as we have envisioned it would concentrate on the science that an airplane can do best: exploration of Titan's global diversity. We focus on surface geology/hydrology and lower-atmospheric structure and dynamics. With a carefully chosen set of seven instruments-2 near-IR cameras, 1 near-IR spectrometer, a RADAR altimeter, an atmospheric structure suite, a haze sensor, and a raindrop detector-AVIATR could accomplish a significant subset of the scientific objectives of the aerial element of flagship studies. The AVIATR spacecraft stack is composed of a Space Vehicle (SV) for cruise, an Entry Vehicle (EV) for entry and descent, and the Air Vehicle (AV) to fly in Titan's atmosphere. Using an Earth-Jupiter gravity assist trajectory delivers the spacecraft to Titan in 7.5 years, after which the AVIATR AV would operate for a 1-Earth-year nominal mission. We propose a novel 'gravity battery' climb-then-glide strategy to store energy for optimal use during telecommunications sessions. We would optimize our science by using the flexibility of the airplane platform, generating context data and stereo pairs by flying and banking the AV instead of using gimbaled cameras. AVIATR would climb up to 14 km altitude and descend down to 3.5 km altitude once per Earth day, allowing for repeated atmospheric structure and wind measurements all over the globe. An initial Team-X run at JPL priced the AVIATR mission at FY10 $715M based on the rules stipulated in the recent Discovery announcement of opportunity. Hence we find that a standalone Titan airplane mission can achieve important science building on Cassini's discoveries and can likely do so within

  17. Misfit dislocations of anisotropic magnetoresistant Nd0.45Sr0.55MnO3 thin films grown on SrTiO3 (1 1 0) substrates

    International Nuclear Information System (INIS)

    Tang, Y.L.; Zhu, Y.L.; Meng, H.; Zhang, Y.Q.; Ma, X.L.

    2012-01-01

    Nd 0.45 Sr 0.55 MnO 3 is an A-type antiferromagnetic manganite showing obvious angular-dependent magnetoresistance, which can be tuned by misfit strain. The misfit strain relaxation of Nd 0.45 Sr 0.55 MnO 3 thin films is of both fundamental and technical importance. In this paper, microstructures of epitaxial Nd 0.45 Sr 0.55 MnO 3 thin films grown on SrTiO 3 (1 1 0) substrates by pulsed laser deposition were investigated by means of (scanning) transmission electron microscopy. The Nd 0.45 Sr 0.55 MnO 3 thin films exhibit a two-layered structure: a continuous perovskite layer epitaxial grown on the substrate followed by epitaxially grown columnar nanostructures. An approximately periodic array of misfit dislocations is found along the interface with line directions of both 〈1 1 1〉 and [0 0 1]. High-resolution (scanning) transmission electron microscopy reveals that all the misfit dislocations possess a〈1 1 0〉-type Burgers vectors. A formation mechanism based on gliding or climbing of the dislocations is proposed to elucidate this novel misfit dislocation configuration. These misfit dislocations have complex effects on the strain relaxation and microstructure of the films, and thus their influence needs further consideration for heteroepitaxial perovskite thin film systems, especially for films grown on substrates with low-symmetry surfaces such as SrTiO 3 (1 1 0) and (1 1 1), which are attracting attention for their potentially new functions.

  18. Effective theory of exotic superconductivity in LaAlO3/SrTiO3 interfaces

    Science.gov (United States)

    Esmailzadeh, Haniyeh; Moghaddam, Ali G.

    2018-05-01

    Motivated by experimental and theoretical works about superconductivity at the oxide interfaces, we provide a simple model for possible unconventional pairings inside the exotic two-dimensional electron gas formed in heterostructures of SrTiO3 and LaAlO3. At the low energy limit, the electron gas at the interfaces is usually modeled with an effective three band model considering of 3d t2g orbitals which are slightly coupled by atomic spin-orbit couplings (SOC). Considering direct superconducting pairing in two higher delocalized bands and by exploiting a perturbative scheme based on canonical transformation, we derive the effective pairing amplitudes with possibly exotic nature inside the localized dxy band as well as various inter-band pairing components. In particular we show that equal-spin triplet pairings are possible between the band dxy and any of other dxz and dyz bands. In addition weaker effective pairings take place inside the localized band itself and between delocalized dxz and dyz bands with singlet and opposite-spin triplet characters. These unconventional effective pairings are indeed mediated by SOC-induced higher order virtual transitions between the bands and particularly into the localized band. Our model suggest that unconventional effective superconductivity is possible at oxide interfaces, simply, due to the special band structure and important role of atomic SOC and perhaps other magnetic effects present at these heterostructures.

  19. Application of electroless Ni-P coating on magnesium alloy via CrO3/HF free titanate pretreatment

    Science.gov (United States)

    Rajabalizadeh, Z.; Seifzadeh, D.

    2017-11-01

    The titanate conversion coating was applied as CrO3/HF free pretreatment for the electroless Ni-P plating on AM60B magnesium alloy. The microscopic images revealed that the alloy surface was completely covered by a cracked conversion film after titanate pretreatment which was mainly composed of Mg(OH)2/MgO, MgF2, TiO2, SiO2, and Al2O3/Al(OH)3. The microscopic images also revealed that numerous Ni nucleation centers were formed over the titanate film after short electroless plating times. The nucleation centers were created not only on the cracked area but also over the whole pretreated surface due to the catalytic action of the titanate film. Also, uniform, dense, and defect-free Ni-P coating with fine structure was achieved after 3 h plating. The Ni-P coating showed mixed crystalline-amorphous structure due to its moderate phosphorus content. The results of two traditional corrosion monitoring methods indicated that the Ni-P coating significantly increases the corrosion resistance of the magnesium alloy. Moreover, Electrochemical Noise (EN) method was used as a non-polarized technique to study the corrosion behavior of the electroless coating at different immersion times. The results of the EN tests were clearly showed the localized nature of the corrosion process. Micro-hardness value of the magnesium alloy was remarkably enhanced after the electroless plating. Finally, suitable adhesion between the Ni-P coating and the magnesium alloy substrate was confirmed by thermal shock and pull-off-adhesion tests.

  20. Adsorptive and photocatalytic properties of S-doped SrTiO3 under simulated solar irradiation

    Science.gov (United States)

    Huynh, Phu Chi; Le, Vien Minh

    2017-09-01

    S-doped SrTiO3 (SSTO) nanoparticles were synthesized using the sol-gel method with Sr(NO3)2, n- Ti(OC4H9)4, and Thiourea as precursors. Several analytical techniques including XRD, SEM, BET were employed to characterize the physical properties of the product. High crystalline perovskite of SSTO powder was synthesized at 700 °C calcined temperature with the specific surface area of 20.71 m2/g. UV-Vis diffuse reflectance spectra results of STO and 5SSTO present band gap energy of 3.2 and 2.95 eV respectively. Photocatalytic activity was determined through the photodegradation of Congo Red at the initial concentrations of 70 ppm under simulated solar irradiation using 26W mercury lamp (120V - 60Hz). The decompositions of approximately 90.4% was obtained after 210 minutes of illumination. The photocatalyst was stable in aqueous solution that its photocatalytic activity was merely reduced by 9% even after 4 reusing iterations.

  1. TITAN'S TRANSPORT-DRIVEN METHANE CYCLE

    International Nuclear Information System (INIS)

    Mitchell, Jonathan L.

    2012-01-01

    The mechanisms behind the occurrence of large cloud outbursts and precipitation on Titan have been disputed. A global- and annual-mean estimate of surface fluxes indicated only 1% of the insolation, or ∼0.04 W m –2 , is exchanged as sensible and/or latent fluxes. Since these fluxes are responsible for driving atmospheric convection, it has been argued that moist convection should be quite rare and precipitation even rarer, even if evaporation globally dominates the surface-atmosphere energy exchange. In contrast, climate simulations indicate substantial cloud formation and/or precipitation. We argue that the top-of-atmosphere (TOA) radiative imbalance is diagnostic of horizontal heat transport by Titan's atmosphere, and thus constrains the strength of the methane cycle. Simple calculations show the TOA radiative imbalance is ∼0.5-1 W m –2 in Titan's equatorial region, which implies 2-3 MW of latitudinal heat transport by the atmosphere. Our simulation of Titan's climate suggests this transport may occur primarily as latent heat, with net evaporation at the equator and net accumulation at higher latitudes. Thus, the methane cycle could be 10-20 times previous estimates. Opposing seasonal transport at solstices, compensation by sensible heat transport, and focusing of precipitation by large-scale dynamics could further enhance the local, instantaneous strength of Titan's methane cycle by a factor of several. A limited supply of surface liquids in regions of large surface radiative imbalance may throttle the methane cycle, and if so, we predict more frequent large storms over the lakes district during Titan's northern summer.

  2. Thermogravimetric study of the kinetics of lithium titanate reduction by hydrogen

    International Nuclear Information System (INIS)

    Sonak, Sagar; Rakesh, R.; Jain, Uttam; Mukherjee, Abhishek; Kumar, Sanjay; Krishnamurthy, Nagaiyar

    2014-01-01

    Highlights: • Li 2 TiO 3 powder is synthesized by the gel combustion route. • Activation energy of reduction of Li 2 TiO 3 by H 2 found out to be 27.45 kJ/mol H 2 . • Non-stoichiometric phase of Li 2 TiO 3 is formed in hydrogen atmosphere. • One-dimensional diffusion appears to be the most probable mechanism of reduction. - Abstract: The lithium titanate powder was synthesized by gel-combustion route. The mechanism and the kinetics of hydrogen interaction with lithium titanate powder were studied using non-isothermal thermogravimetric technique. Lithium titanate underwent reduction in hydrogen atmosphere which led to the formation of oxygen deficient non-stoichiometric compound in lithium titanate. One-dimensional diffusion appeared to be the most probable reaction mechanism. The activation energy for reduction of lithium titanate under hydrogen atmosphere was found to be 27.4 kJ/mol/K. Structural changes after hydrogen reduction in lithium titanate were observed in X-ray diffraction analysis

  3. Nonthermal atmospheric escape from Mars and Titan

    International Nuclear Information System (INIS)

    Lammer, H.; Bauer, S.J.

    1991-01-01

    Energy flux spectra and particle concentrations of the hot O and N coronae from Mars and Titan, respectively, resulting primarily from dissociative recombination of molecular ions, have been calculated by means of a Monte Carlo method. The calculated energy flux spectra lead to an escape flux null esc ∼ 6 x 10 6 cm -2 s -1 for Mars and null esc ∼ 2 x 10 6 cm -2 s -1 for Titan, corresponding to a mass loss of about 0.14 kg/s for Mars and about 0.3 kg/s for Titan. (The contribution of electron impact ionization on N 2 amounts to only about 25% of Titan's mass loss.) Mass loss via solar and magnetospheric wind is also estimated using newly calculated mass loading limits. The mass loss via ion pickup from the extended hot atom corona for Mars amounts to about 0.25 kg/s (O + ) and for Titan to about 50 g/s (N 2 + or H 2 CN + ). Thus, the total mass loss rate from Mars and Titan is about the same, i.e., 0.4 kg/s

  4. Coexistence of nonvolatility and volatility in Pt/Nb-doped SrTiO3/In memristive devices

    International Nuclear Information System (INIS)

    Yang, M; Bao, D H; Li, S W

    2013-01-01

    Memristive devices are triggering innovations in the fields of nonvolatile memory, digital logic, analogue circuits, neuromorphic engineering, and so on. Creating new memristive devices with unique characteristics would be significant for these emergent applications. Here we report the coexistence of nonvolatility and volatility in Pt/Nb-doped SrTiO 3 (NSTO)/In memristive devices. The Pt/NSTO interface contributes a nonvolatile resistive switching behaviour, whereas the NSTO/In interface displays a volatile hysteresis loop. Combining the two interfaces in the Pt/NSTO/In devices leads to the unique coexistence of nonvolatility and volatility. The results imply more opportunities to invent new memristive devices by engineering both interfaces in metal/insulator/metal structures. (paper)

  5. Charge driven metal-insulator transitions in LaMnO3|SrTiO3 (111) superlattices

    KAUST Repository

    Cossu, Fabrizio; Tahini, Hassan Ali; Singh, Nirpendra; Schwingenschlö gl, Udo

    2017-01-01

    Interfaces of perovskite oxides, due to the strong interplay between the lattice, charge and spin degrees of freedom, can host various phase transitions, which is particularly interesting if these transitions can be tuned by external fields. Recently, ferromagnetism was found together with a seemingly insulating state in superlattices of manganites and titanates. We therefore study the (111) oriented $(\\text{LaMnO}_3)_{6-x}\\vert(\\text{SrTiO}_3)_{6+x}~(x = -0.5, 0, 0.5)$ superlattices by means of ab initio calculations, predicting a ferromagnetic ground state due to double exchange in all cases. We shed light on the ferromagnetic coupling in the LaMnO3 region and at the interfaces. The insulating states of specific superlattices can be understood on the basis of Jahn-Teller modes and electron/hole doping.

  6. Charge driven metal-insulator transitions in LaMnO3|SrTiO3 (111) superlattices

    KAUST Repository

    Cossu, Fabrizio

    2017-08-01

    Interfaces of perovskite oxides, due to the strong interplay between the lattice, charge and spin degrees of freedom, can host various phase transitions, which is particularly interesting if these transitions can be tuned by external fields. Recently, ferromagnetism was found together with a seemingly insulating state in superlattices of manganites and titanates. We therefore study the (111) oriented $(\\\\text{LaMnO}_3)_{6-x}\\\\vert(\\\\text{SrTiO}_3)_{6+x}~(x = -0.5, 0, 0.5)$ superlattices by means of ab initio calculations, predicting a ferromagnetic ground state due to double exchange in all cases. We shed light on the ferromagnetic coupling in the LaMnO3 region and at the interfaces. The insulating states of specific superlattices can be understood on the basis of Jahn-Teller modes and electron/hole doping.

  7. Barium Titanate Nanoparticles for Biomarker Applications

    International Nuclear Information System (INIS)

    Matar, O; Hondow, N S; Brydson, R M D; Milne, S J; Brown, A P; Posada, O M; Wälti, C; Saunders, M; Murray, C A

    2015-01-01

    A tetragonal crystal structure is required for barium titanate nanoparticles to exhibit the nonlinear optical effect of second harmonic light generation (SHG) for use as a biomarker when illuminated by a near-infrared source. Here we use synchrotron XRD to elucidate the tetragonal phase of commercially purchased tetragonal, cubic and hydrothermally prepared barium titanate (BaTiO 3 ) nanoparticles by peak fitting with reference patterns. The local phase of individual nanoparticles is determined by STEM electron energy loss spectroscopy (EELS), measuring the core-loss O K-edge and the Ti L 3 -edge energy separation of the t 2g , e g peaks. The results show a change in energy separation between the t 2g and e g peak from the surface and core of the particles, suggesting an intraparticle phase mixture of the barium titanate nanoparticles. HAADF-STEM and bright field TEM-EDX show cellular uptake of the hydrothermally prepared BaTiO 3 nanoparticles, highlighting the potential for application as biomarkers. (paper)

  8. Electrical and piezoelectric properties of BiFeO3 thin films grown on SrxCa1−xRuO3-buffered SrTiO3 substrates

    KAUST Repository

    Yao, Yingbang

    2012-06-01

    (001)-oriented BiFeO 3 (BFO) thin films were grown on Sr xCa 1-xRuO 3- (SCRO; x = 1, 0.67, 0.33, 0) buffered SrTiO 3 (001) substrates using pulsed laser deposition. The microstructural, electrical, ferroelectric, and piezoelectric properties of the thin films were considerably affected by the buffer layers. The interface between the BFO films and the SCRO-buffer layer was found to play a dominant role in determining the electrical and piezoelectric behaviors of the films. We found that films grown on SrRuO 3-buffer layers exhibited minimal electrical leakage while films grown on Sr 0.33Ca 0.67RuO 3-buffer layers had the largest piezoelectric response. The origin of this difference is discussed. © 2012 American Institute of Physics.

  9. Perovskite oxide SrTiO3 as an efficient electron transporter for hybrid perovskite solar cells

    KAUST Repository

    Bera, Ashok

    2014-12-11

    In this work, we explored perovskite oxide SrTiO3 (STO) for the first time as the electron-transporting layer in organolead trihalide perovskite solar cells. The steady-state photoluminescence (PL) quenching and transient absorption experiments revealed efficient photoelectron transfer from CH3NH3PbI3-xClx to STO. Perovskite solar cells with meso-STO exhibit an open circuit voltage of 1.01 V, which is 25% higher than the value of 0.81 V achieved in the control device with the conventional meso-TiO2. In addition, an increase of 17% in the fill factor was achieved by tailoring the thickness of the meso-STO layer. We found that the application of STO leads to uniform perovskite layers with large grains and complete surface coverage, leading to a high shunt resistance and improved performance. These findings suggest STO as a competitive candidate as electron transport material in organometal perovskite solar cells.

  10. Perovskite oxide SrTiO3 as an efficient electron transporter for hybrid perovskite solar cells

    KAUST Repository

    Bera, Ashok; Wu, Kewei; Sheikh, Arif D.; Alarousu, Erkki; Mohammed, Omar F.; Wu, Tao

    2014-01-01

    In this work, we explored perovskite oxide SrTiO3 (STO) for the first time as the electron-transporting layer in organolead trihalide perovskite solar cells. The steady-state photoluminescence (PL) quenching and transient absorption experiments revealed efficient photoelectron transfer from CH3NH3PbI3-xClx to STO. Perovskite solar cells with meso-STO exhibit an open circuit voltage of 1.01 V, which is 25% higher than the value of 0.81 V achieved in the control device with the conventional meso-TiO2. In addition, an increase of 17% in the fill factor was achieved by tailoring the thickness of the meso-STO layer. We found that the application of STO leads to uniform perovskite layers with large grains and complete surface coverage, leading to a high shunt resistance and improved performance. These findings suggest STO as a competitive candidate as electron transport material in organometal perovskite solar cells.

  11. Three members of Medicago truncatula ST family are ubiquitous during development and modulated by nutritional status (MtST1) and dehydration (MtST2 and MtST3).

    Science.gov (United States)

    Albornos, Lucía; Martín, Ignacio; Labrador, Emilia; Dopico, Berta

    2017-07-10

    ShooT specific/Specific Tissue (ST) belong to a protein family of unknown function characterized by the DUF2775 domain and produced in specific taxonomic plant families, mainly Fabaceae and Asteraceae, with the Medicago truncatula ST family being the largest. The putative roles proposed for this family are cell elongation, biotic interactions, abiotic stress and N reserve. The aim of this work was to go deeper into the role of three M. truncatula ST proteins, namely ST1, ST2 and ST3. Our starting hypothesis was that each member of the family could perform a specific role, and hence, each ST gene would be subjected to a different type of regulation. The search for cis-acting regulatory elements (CREs) in silico in pST1, pST2 and pST3 promoters showed prevalence of tissue/organ specific motifs, especially root- and seed-specific ones. Light, hormone, biotic and abiotic related motifs were also present. None of these pSTs showed the same combination of CREs, or presented the same activity pattern. In general, pST activity was associated with the vascular cylinder, mainly in roots. Promoter activation was highly specific and dissimilar during reproductive development. The ST1, ST2 and ST3 transcripts accumulated in most of the organs and developmental stages analysed - decreasing with age - and expression was higher in the roots than in the aerial parts and more abundant in light-grown plants. The effect of the different treatments on transcript accumulation indicated that ST1 behaved differently from ST2 and ST3, mainly in response to several hormones and dehydration treatments (NaCl or mannitol), upon which ST1 transcript levels decreased and ST2 and ST3 levels increased. Finally, the ST1 protein was located in the cell wall whereas ST2 and ST3 were present both in the cytoplasm and in the cell wall. The ST proteins studied are ubiquitous proteins that could perform distinct/complementary roles in plant biology as they are encoded by differentially regulated genes

  12. Titan Aerial Daughtercraft

    Data.gov (United States)

    National Aeronautics and Space Administration — Saturn's giant moon Titan has become one of the most fascinating bodies in the Solar System. Titan is the richest laboratory in the solar system for studying...

  13. A whiff of nebular gas in Titan's atmosphere - Potential implications for the conditions and timing of Titan's formation

    Science.gov (United States)

    Glein, Christopher R.

    2017-09-01

    solar system, before the ultimate source of gas (the solar nebula) dissipated. More specifically, if photoevaporative fractionation happened, the time-evolution for the depletion of permanent gases in the solar nebula can be parameterized to the ∼3 times solar noble gas enrichments of Jupiter for an assumed Jupiter formation time of ∼2 Myr after calcium-aluminum-rich inclusions (CAIs). This allows the construction of a consistent chronology with a Titan formation time of ∼3-4 Myr after CAIs. Because the models presented in this work are pushing the limits of the data from Titan, future mass spectrometric measurements of the noble gases and their isotopes (to at least ppt sensitivity) will be essential to confirm the Huygens detection of 22Ne, and to constrain the roles of evolutionary processes and mixed sources in determining the noble gas geochemistry of Titan's atmosphere. The clearest indication of a nebular gas source for noble gases on Titan would be a solar-like isotopic ratio of 20Ne/22Ne ≈ 14.

  14. Diurnal variations of Titan's ionosphere

    Science.gov (United States)

    Cui, J.; Galand, M.; Yelle, R. V.; Vuitton, V.; Wahlund, J.-E.; Lavvas, P. P.; Müller-Wodarg, I. C. F.; Cravens, T. E.; Kasprzak, W. T.; Waite, J. H.

    2009-06-01

    We present our analysis of the diurnal variations of Titan's ionosphere (between 1000 and 1300 km) based on a sample of Ion Neutral Mass Spectrometer (INMS) measurements in the Open Source Ion (OSI) mode obtained from eight close encounters of the Cassini spacecraft with Titan. Although there is an overall ion depletion well beyond the terminator, the ion content on Titan's nightside is still appreciable, with a density plateau of ˜700 cm-3 below ˜1300 km. Such a plateau is a combined result of significant depletion of light ions and modest depletion of heavy ones on Titan's nightside. We propose that the distinctions between the diurnal variations of light and heavy ions are associated with their different chemical loss pathways, with the former primarily through “fast” ion-neutral chemistry and the latter through “slow” electron dissociative recombination. The strong correlation between the observed night-to-day ion density ratios and the associated ion lifetimes suggests a scenario in which the ions created on Titan's dayside may survive well to the nightside. The observed asymmetry between the dawn and dusk ion density profiles also supports such an interpretation. We construct a time-dependent ion chemistry model to investigate the effect of ion survival associated with solid body rotation alone as well as superrotating horizontal winds. For long-lived ions, the predicted diurnal variations have similar general characteristics to those observed. However, for short-lived ions, the model densities on the nightside are significantly lower than the observed values. This implies that electron precipitation from Saturn's magnetosphere may be an additional and important contributor to the densities of the short-lived ions observed on Titan's nightside.

  15. Detection and mapping of organic molecules in Titan's atmosphere using ALMA

    Science.gov (United States)

    Cordiner, Martin

    2016-06-01

    Titan's atmospheric photochemistry results in the production of a wide range of organic molecules, including hydrocarbons, nitriles, aromatics and other complex species of possible pre-biotic relevance. Studies of Titan's atmospheric chemistry thus provide a unique opportunity to explore the origin and evolution of organic matter in primitive (terrestrial) planetary atmospheres. The Atacama Large Millimeter/submillimeter Array (ALMA) is a powerful new facility, well suited to the study of molecular emission from Titan's upper and middle-atmosphere. Results will be presented from our ongoing studies of Titan using ALMA data obtained during the period 2012-2014 [1,2], including detection and mapping of emission from C2H5CN, HNC, HC3N, CH3CN and CH3CCH. In addition, combining data from multiple ALMA Band 6 observations, we obtained high-resolution spectra with unprecedented sensitivity, enabling the first detection of C2H3CN (vinyl cyanide) on Titan, and derived a mean C2H3CN C2H5CN abundance ratio above 300 km of 0.3. Vinyl cyanide has recently been investigated as a possible constituent of (pre-biotic) vesicle membranes in Titan's liquid CH4 oceans [3]. Radiative transfer models and possible chemical formation pathways for the detected molecules will be discussed. ALMA observations provide instantaneous snapshot mapping of Titan's entire Earth-facing hemisphere for gases inaccessible to previous studies, and therefore provide new insights into photochemical production and transport, particularly at higher altitudes. Our maps show spatially resolved peaks in Titan's northern and southern hemispheres, consistent with the molecular distributions found in previous studies at infrared wavelengths by Voyager and Cassini, but high-altitude longitudinal asymmetries in our nitrile data indicate that the mesosphere may be more spatially variable than previously thought.

  16. Epitaxial growth of YBa2Cu307−δ films on SrTiO3 (100) by direct solution precursor deposition

    International Nuclear Information System (INIS)

    Bustamante, A; Garcia, Jorge; Osorio, Ana M; Valladares, Luis De Los Santos; Barnes, C H W; González, J C; Azuma, Y; Majima, Y; Aguiar, J Albino

    2014-01-01

    We study the optimal temperature to obtain YBa 2 Cu 3 O 7-δ epitaxial films grown onto SrTiO 3 substrates by direct solution deposition. The samples received heat treatment at 820, 840 and 860 °C, then characterized by XRD, observing the (00l) profiles; and magnetic susceptibility measurements. The T C-onset for all the samples was 90 K. In addition, the current – voltage (I-V) measurements shows typical tunneling signals corresponding to normal metal-superconducting junctions indicating the films are promising for potential electrical applications.

  17. Atomic control of substrate termination and heteroepitaxial growth of SrTiO sub 3 /LaAlO sub 3 films

    CERN Document Server

    Kim, D W; Choi, C; Lim, K D; Noh, T W; Lee, D R; Park, J H; Lee, K B

    2000-01-01

    The roles of substrate termination in the growth behaviors of SrTiO sub 3 (STO) films were investigated. With heat treatment and an atomic layer deposition technique, LaAlO sub 3 (LAO) substrates with two kinds of terminations, i.e., LaO- and AlO sub 2 -terminated ones, could be prepared. On top of them STO films were grown by using laser molecular beam epitaxy. In the case of the STO/LaO-LAO film, a transition from layer-by-layer growth to island growth was observed after growth of about 10 monolayers (ML). On the other hand, the STO/AlO sub 2 -LAO film could be grown in a layer-by-layer mode with a flat surface up to 40 ML. We suggest that defects induced by charge compensation influence the strain states and the physical properties of oxide heterostructures significantly.

  18. Advances in Architectural Elements For Future Missions to Titan

    Science.gov (United States)

    Reh, Kim; Coustenis, Athena; Lunine, Jonathan; Matson, Dennis; Lebreton, Jean-Pierre; Vargas, Andre; Beauchamp, Pat; Spilker, Tom; Strange, Nathan; Elliott, John

    2010-05-01

    The future exploration of Titan is of high priority for the solar system exploration community as recommended by the 2003 National Research Council (NRC) Decadal Survey [1] and ESA's Cosmic Vision Program themes. Recent Cassini-Huygens discoveries continue to emphasize that Titan is a complex world with very many Earth-like features. Titan has a dense, nitrogen atmosphere, an active climate and meteorological cycles where conditions are such that the working fluid, methane, plays the role that water does on Earth. Titan's surface, with lakes and seas, broad river valleys, sand dunes and mountains was formed by processes like those that have shaped the Earth. Supporting this panoply of Earth-like processes is an ice crust that floats atop what might be a liquid water ocean. Furthermore, Titan is rich in very many different organic compounds—more so than any place in the solar system, except Earth. The Titan Saturn System Mission (TSSM) concept that followed the 2007 TandEM ESA CV proposal [2] and the 2007 Titan Explorer NASA Flagship study [3], was examined [4,5] and prioritized by NASA and ESA in February 2009 as a mission to follow the Europa Jupiter System Mission. The TSSM study, like others before it, again concluded that an orbiter, a montgolfiere hot-air balloon and a surface package (e.g. lake lander, Geosaucer (instrumented heat shield), …) are very high priority elements for any future mission to Titan. Such missions could be conceived as Flagship/Cosmic Vision L-Class or as individual smaller missions that could possibly fit into NASA New Frontiers or ESA Cosmic Vision M-Class budgets. As a result of a multitude of Titan mission studies, a clear blueprint has been laid out for the work needed to reduce the risks inherent in such missions and the areas where advances would be beneficial for elements critical to future Titan missions have been identified. The purpose of this paper is to provide a brief overview of the flagship mission architecture and

  19. First-principles modeling of titanate/ruthenate superlattices

    Science.gov (United States)

    Junquera, Javier

    2013-03-01

    The possibility to create highly confined two-dimensional electron gases (2DEG) at oxide interfaces has generated much excitement during the last few years. The most widely studied system is the 2DEG formed at the LaO/TiO2 polar interface between LaAlO3 and SrTiO3, where the polar catastrophe at the interface has been invoked as the driving force. More recently, partial or complete delta doping of the Sr or Ti cations at a single layer of a SrTiO3 matrix has also been used to generate 2DEG. Following this recipe, we report first principles characterization of the structural and electronic properties of (SrTiO3)5/(SrRuO3)1 superlattices, where all the Ti of a given layer have been replaced by Ru. We show that the system exhibits a spin-polarized two-dimensional electron gas extremely confined to the 4 d orbitals of Ru in the SrRuO3 layer, a fact that is independent of the level of correlation included in the simulations. For hybrid functionals or LDA+U, every interface in the superlattice behaves as minority-spin half-metal ferromagnet, with a magnetic moment of μ = 2.0 μB/SrRuO3 unit. The shape of the electronic density of states, half metallicity and magnetism are explained in terms of a simplified tight-binding model, considering only the t2 g orbitals plus (i) the bi-dimensionality of the system, and (ii) strong electron correlations. Possible applications are discussed, from their eventual role in thermoelectric applications to the possible tuning of ferromagnetic properties of the 2DEG with the polarization of the dielectric. Work done in collaboration with P. García, M. Verissimo-Alves, D. I. Bilc, and Ph. Ghosez. Financial support provided by MICINN Grant FIS2009-12721-C04-02, and by the European Union Grant No. CP-FP 228989-2 ``OxIDes.'' The authors thankfully acknowledge the computer resources, technical expertise and assistance provided by the BSC/RES.

  20. A 3-D Chemistry Transport Model for Titan's Thermosphere

    Science.gov (United States)

    Doege, M. C.; Marsh, D. R.; Brasseur, G. P.; Mueller-Wodarg, I.; Tokano, T.; Newman, C. E.

    2008-12-01

    MOZART-2 (Horowitz et al., 2003) has been adapted to investigate seasonal and diurnal differences in neutral composition in Titan's atmosphere between the surface and 1,200 km altitude. The chemical scheme with 64 solution species and 383 reactions is based on a simplified version of the Lavvas et al. (2008) scheme, without haze production. Wind and temperature fields were taken from the Cologne GCM (Tokano, 2007) or TitanWRF (Richardson et al., 2007) for the troposphere and stratosphere, and from the London TGCM (Mueller-Wodarg, 2000) for the thermosphere. Pronounced hemispheric concentration gradients develop in the thermosphere, and a strong diurnal cycle in composition is found, similar to the findings of Mueller-Wodarg (2003) for methane. Sensitivity experiments with different strengths of thermospheric circulation to account for uncertainty about the wind fields in that region are presented.

  1. The Exploration of Titan and the Saturnian System

    Science.gov (United States)

    Coustenis, Athena

    The exploration of the outer solar system and in particular of the giant planets and their environments is an on-going process with the Cassini spacecraft currently around Saturn, the Juno mission to Jupiter preparing to depart and two large future space missions planned to launch in the 2020-2025 time frame for the Jupiter system and its satellites (Europa and Ganymede) on the one hand, and the Saturnian system and Titan on the other hand [1,2]. Titan, Saturn's largest satellite, is the only other object in our Solar system to possess an extensive nitrogen atmosphere, host to an active organic chemistry, based on the interaction of N2 with methane (CH4). Following the Voyager flyby in 1980, Titan has been intensely studied from the ground-based large telescopes (such as the Keck or the VLT) and by artificial satellites (such as the Infrared Space Observatory and the Hubble Space Telescope) for the past three decades. Prior to Cassini-Huygens, Titan's atmospheric composition was thus known to us from the Voyager missions and also through the explorations by the ISO. Our perception of Titan had thus greatly been enhanced accordingly, but many questions remained as to the nature of the haze surrounding the satellite and the composition of the surface. The recent revelations by the Cassini-Huygens mission have managed to surprise us with many discoveries [3-8] and have yet to reveal more of the interesting aspects of the satellite. The Cassini-Huygens mission to the Saturnian system has been an extraordinary success for the planetary community since the Saturn-Orbit-Insertion (SOI) in July 2004 and again the very successful probe descent and landing of Huygens on January 14, 2005. One of its main targets was Titan. Titan was revealed to be a complex world more like the Earth than any other: it has a dense mostly nitrogen atmosphere and active climate and meteorological cycles where the working fluid, methane, behaves under Titan conditions the way that water does on

  2. Emergent chirality in the electric polarization texture of titanate superlattices.

    Science.gov (United States)

    Shafer, Padraic; García-Fernández, Pablo; Aguado-Puente, Pablo; Damodaran, Anoop R; Yadav, Ajay K; Nelson, Christopher T; Hsu, Shang-Lin; Wojdeł, Jacek C; Íñiguez, Jorge; Martin, Lane W; Arenholz, Elke; Junquera, Javier; Ramesh, Ramamoorthy

    2018-01-30

    Chirality is a geometrical property by which an object is not superimposable onto its mirror image, thereby imparting a handedness. Chirality determines many important properties in nature-from the strength of the weak interactions according to the electroweak theory in particle physics to the binding of enzymes with naturally occurring amino acids or sugars, reactions that are fundamental for life. In condensed matter physics, the prediction of topologically protected magnetic skyrmions and related spin textures in chiral magnets has stimulated significant research. If the magnetic dipoles were replaced by their electrical counterparts, then electrically controllable chiral devices could be designed. Complex oxide BaTiO 3 /SrTiO 3 nanocomposites and PbTiO 3 /SrTiO 3 superlattices are perfect candidates, since "polar vortices," in which a continuous rotation of ferroelectric polarization spontaneously forms, have been recently discovered. Using resonant soft X-ray diffraction, we report the observation of a strong circular dichroism from the interaction between circularly polarized light and the chiral electric polarization texture that emerges in PbTiO 3 /SrTiO 3 superlattices. This hallmark of chirality is explained by a helical rotation of electric polarization that second-principles simulations predict to reside within complex 3D polarization textures comprising ordered topological line defects. The handedness of the texture can be topologically characterized by the sign of the helicity number of the chiral line defects. This coupling between the optical and novel polar properties could be exploited to encode chiral signatures into photon or electron beams for information processing.

  3. Electron-density distribution in cubic SrTiO3: a comparative γ-ray diffraction study

    International Nuclear Information System (INIS)

    Jauch, W.; Reehuis, M.

    2005-01-01

    The electron density and atomic displacements in the perovskite SrTiO 3 have been studied using extensive and accurate γ-ray diffraction data (λ=0.0392 Aa) at room temperature. The six strongest low-order structure factors have been determined under extinction-free conditions. Gram-Charlier series expansion of the thermal parameters have revealed no evidence for anharmonicity. The population of the 3d subshell on Ti is found to be close to zero, in agreement with the observed magnetic behaviour. The electronic properties at the bond critical points indicate ionic Ti-O and Sr-O interactions of different strengths, which is corroborated by the net charges of the atomic basins [q(Sr)=1.18 vertical stroke e vertical stroke, q(Ti)=3.10 vertical stroke e vertical stroke, q(O)=1.42 vertical stroke e vertical stroke ]. A critical comparison is made with earlier experimental results from laboratory X-ray, synchrotron X-ray, electron and neutron diffraction studies. Agreement and discrepancies are identified and resolved. (orig.)

  4. ATOMIC CARBON IN THE UPPER ATMOSPHERE OF TITAN

    International Nuclear Information System (INIS)

    Zhang, X.; Yung, Y. L.; Ajello, J. M.

    2010-01-01

    The atomic carbon emission C I line feature at 1657 A ( 3 P 0 J - 3 P J ) in the upper atmosphere of Titan is first identified from the airglow spectra obtained by the Cassini Ultra-violet Imaging Spectrograph. A one-dimensional photochemical model of Titan is used to study the photochemistry of atomic carbon on Titan. Reaction between CH and atomic hydrogen is the major source of atomic carbon, and reactions with hydrocarbons (C 2 H 2 and C 2 H 4 ) are the most important loss processes. Resonance scattering of sunlight by atomic carbon is the dominant emission mechanism. The emission intensity calculations based on model results show good agreement with the observations.

  5. Thermal conductivity reduction in oxygen-deficient strontium titanates

    NARCIS (Netherlands)

    Yu, Choongho; Scullin, Matthew L.; Huijben, Mark; Ramesh, Ramamoorthy; Majumdar, Arun

    2008-01-01

    We report significant thermal conductivity reduction in oxygen-deficient lanthanum-doped strontium titanate (Sr1−xLaxTiO3−δ) films as compared to unreduced strontium titanates. Our experimental results suggest that the oxygen vacancies could have played an important role in the reduction. This could

  6. An epitaxial transparent conducting perovskite oxide: double-doped SrTiO3

    NARCIS (Netherlands)

    Ravichandran, Jayakanth; Siemons, W.; Heijmerikx, Herman; Huijben, Mark; Majumdar, Arun; Ramesh, Ramamoorthy

    2010-01-01

    Epitaxial thin films of strontium titanate doped with different concentrations of lanthanum and oxygen vacancies were grown on LSAT substrates by pulsed laser deposition technique. Films grown with 5−15% La doping and a critical growth pressure of 1−10 mTorr showed high transparency (>70−95%) in the

  7. Large tunneling anisotropic magnetoresistance in La0.7Sr0.3MnO3/pentacene/Cu structures prepared on SrTiO3 (110) substrates

    Science.gov (United States)

    Kamiya, Takeshi; Miyahara, Chihiro; Tada, Hirokazu

    2017-01-01

    We investigated tunneling anisotropic magnetoresistance (TAMR) at the interface between pentacene and La0.7Sr0.3MnO3 (LSMO) thin films prepared on SrTiO3 (STO) (110) substrates. The dependence of the TAMR ratio on the magnetic field strength was approximately ten times larger than that of the magnetic field angle at a high magnetic field. This large difference in the TAMR ratio is explained by the interface magnetic anisotropy of strain-induced LSMO thin films on a STO (110) substrate, which has an easy axis with an out-of-plane component. We also note that the TAMR owing to out-of-plane magnetization was positive at each angle of the in-plane magnetic field. This result implies that active control of the interface magnetic anisotropy between organic materials and ferromagnetic metals should realize nonvolatile and high-efficiency TAMR devices.

  8. Tunable photovoltaic effect and solar cell performance of self-doped perovskite SrTiO3

    Directory of Open Access Journals (Sweden)

    K. X. Jin

    2012-12-01

    Full Text Available We report on the tunable photovoltaic effect of self-doped single-crystal SrTiO3 (STO, a prototypical perovskite-structured complex oxide, and evaluate its performance in Schottky junction solar cells. The photovaltaic characteristics of vacuum-reduced STO single crystals are dictated by a thin surface layer with electrons donated by oxygen vacancies. Under UV illumination, a photovoltage of 1.1 V is observed in the as-received STO single crystal, while the sample reduced at 750 °C presents the highest incident photon to carrier conversion efficiency. Furthermore, in the STO/Pt Schottky junction, a power conversion efficiency of 0.88% was achieved under standard AM 1.5 illumination at room temperature. This work establishes STO as a high-mobility photovoltaic semiconductor with potential of integration in self-powered oxide electronics.

  9. The TITAN reversed-field-pinch fusion reactor study

    International Nuclear Information System (INIS)

    1990-01-01

    This report discusses the following topics: overview of titan-2 design; titan-2 fusion-power-core engineering; titan-2 divertor engineering; titan-2 tritium systems; titan-2 safety design and radioactive-waste disposal; and titan-2 maintenance procedures

  10. The TITAN reversed-field-pinch fusion reactor study

    Energy Technology Data Exchange (ETDEWEB)

    1990-01-01

    This report discusses the following topics: overview of titan-2 design; titan-2 fusion-power-core engineering; titan-2 divertor engineering; titan-2 tritium systems; titan-2 safety design and radioactive-waste disposal; and titan-2 maintenance procedures.

  11. Titan's organic chemistry

    Science.gov (United States)

    Sagan, C.; Thompson, W. R.; Khare, B. N.

    1985-01-01

    Voyager discovered nine simple organic molecules in the atmosphere of Titan. Complex organic solids, called tholins, produced by irradiation of the simulated Titanian atmosphere, are consistent with measured properties of Titan from ultraviolet to microwave frequencies and are the likely main constituents of the observed red aerosols. The tholins contain many of the organic building blocks central to life on earth. At least 100-m, and possibly kms thicknesses of complex organics have been produced on Titan during the age of the solar system, and may exist today as submarine deposits beneath an extensive ocean of simple hydrocarbons.

  12. GeoTIFF of 3x3 m Bathymetry for St. Thomas & St. John, 2011, UTM 20N NAD83

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This image represents a LiDAR (Light Detection & Ranging) 3x3 meter resolution bathymetric surface for an area of shallow seabed surrounding St. Thomas and St....

  13. Visible-light-driven photoelectrochemical and photocatalytic performances of Cr-doped SrTiO3/TiO2 heterostructured nanotube arrays.

    Science.gov (United States)

    Jiao, Zhengbo; Chen, Tao; Xiong, Jinyan; Wang, Teng; Lu, Gongxuan; Ye, Jinhua; Bi, Yingpu

    2013-01-01

    Well-aligned TiO2 nanotube arrays have become of increasing significance because of their unique highly ordered array structure, high specific surface area, unidirectional charge transfer and transportation features. However, their poor visible light utilization as well as the high recombination rate of photoexcited electron-hole pairs greatly limited their practical applications. Herein, we demonstrate the fabrication of visible-light-responsive heterostructured Cr-doped SrTiO3/TiO2 nanotube arrays by a simple hydrothermal method, which facilitate efficient charge separation and thus improve the photoelectrochemical as well as photocatalytic performances.

  14. A green synthesis of a layered titanate, potassium lithium titanate; lower temperature solid-state reaction and improved materials performance

    International Nuclear Information System (INIS)

    Ogawa, Makoto; Morita, Masashi; Igarashi, Shota; Sato, Soh

    2013-01-01

    A layered titanate, potassium lithium titanate, with the size range from 0.1 to 30 µm was prepared to show the effects of the particle size on the materials performance. The potassium lithium titanate was prepared by solid-state reaction as reported previously, where the reaction temperature was varied. The reported temperature for the titanate preparation was higher than 800 °C, though 600 °C is good enough to obtain single-phase potassium lithium titanate. The lower temperature synthesis is cost effective and the product exhibit better performance as photocatalysts due to surface reactivity. - Graphical abstract: Finite particle of a layered titanate, potassium lithium titanate, was prepared by solid-state reaction at lower temperature to show modified materials performance. Display Omitted - Highlights: • Potassium lithium titanate was prepared by solid-state reaction. • Lower temperature reaction resulted in smaller sized particles of titanate. • 600 °C was good enough to obtain single phased potassium lithium titanate. • The product exhibited better performance as photocatalyst

  15. Infrared Spectra and Optical Constants of Nitrile Ices Relevant to Titan's Atmosphere

    Science.gov (United States)

    Anderson, Carrie; Ferrante, Robert F.; Moore, W. James; Hudson, Reggie; Moore, Marla H.

    2011-01-01

    Spectra and optical constants of nitrile ices known or suspected to be in Titan?s atmosphere have been determined from 2.0 to 333.3 microns (approx.5000 to 30/cm). These results are relevant to the ongoing modeling of Cassini CIRS observations of Titan?s winter pole. Ices studied were: HCN, hydrogen cyanide; C2N2, cyanogen; CH3CN, acetonitrile; C2H5CN, propionitrile; and HC3N, cyanoacetylene. Optical constants were calculated, using Kramers-Kronig analysis, for each nitrile ice?s spectrum measured at a variety of temperatures, in both the amorphous- and crystalline phases. Spectra were also measured for many of the nitriles after quenching at the annealing temperature and compared with those of annealed ices. For each of these molecules we also measured the real component, n, of the refractive index for amorphous and crystalline phases at 670 nm. Several examples of the information contained in these new data sets and their usefulness in modeling Titan?s observed features will be presented (e.g., the broad emission feature at 160/cm; Anderson and Samuelson, 2011).

  16. The TITAN reversed-field-pinch fusion reactor study

    International Nuclear Information System (INIS)

    1990-01-01

    This report discusses research on the titan-1 fusion power core. The major topics covered are: titan-1 fusion-power-core engineering; titan-1 divertor engineering; titan-1 tritium systems; titan-1 safety design and radioactive-waste disposal; and titan-1 maintenance procedures

  17. The TITAN reversed-field-pinch fusion reactor study

    Energy Technology Data Exchange (ETDEWEB)

    1990-01-01

    This report discusses research on the titan-1 fusion power core. The major topics covered are: titan-1 fusion-power-core engineering; titan-1 divertor engineering; titan-1 tritium systems; titan-1 safety design and radioactive-waste disposal; and titan-1 maintenance procedures.

  18. DETECTION OF PROPENE IN TITAN'S STRATOSPHERE

    Energy Technology Data Exchange (ETDEWEB)

    Nixon, C. A.; Flasar, F. M. [Planetary Systems Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Jennings, D. E. [Detector Systems Branch, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Bézard, B.; Vinatier, S.; Coustenis, A. [LESIA, Observatoire de Paris, CNRS, 5 Place Jules Janssen, F-92195 Meudon Cedex (France); Teanby, N. A. [School of Earth Sciences, University of Bristol, Wills Memorial Building, Queen' s Road, Bristol BS8 1RJ (United Kingdom); Sung, K. [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, CA 91109 (United States); Ansty, T. M. [Department of Space Science, Cornell University, Ithaca, NY 14853 (United States); Irwin, P. G. J. [Atmospheric, Oceanic and Planetary Physics, University of Oxford, Clarendon Laboratory, Parks Road, Oxford OX1 3PU (United Kingdom); Gorius, N. [IACS, Catholic University of America, Washington, DC 20064 (United States); Cottini, V. [Department of Astronomy, University of Maryland, College Park, MD 20742 (United States)

    2013-10-10

    The Voyager 1 flyby of Titan in 1980 gave a first glimpse of the chemical complexity of Titan's atmosphere, detecting many new molecules with the infrared interferometer spectrometer (IRIS). These included propane (C{sub 3}H{sub 8}) and propyne (CH{sub 3}C{sub 2}H), while the intermediate-sized C{sub 3}H {sub x} hydrocarbon (C{sub 3}H{sub 6}) was curiously absent. Using spectra from the Composite Infrared Spectrometer on Cassini, we show the first positive detection of propene (C{sub 3}H{sub 6}) in Titan's stratosphere (5σ significance), finally filling the three-decade gap in the chemical sequence. We retrieve a vertical abundance profile from 100-250 km, that varies slowly with altitude from 2.0 ± 0.8 ppbv at 125 km, to 4.6 ± 1.5 ppbv at 200 km. The abundance of C{sub 3}H{sub 6} is less than both C{sub 3}H{sub 8} and CH{sub 3}C{sub 2}H, and we remark on an emerging paradigm in Titan's hydrocarbon abundances whereby alkanes > alkynes > alkenes within the C{sub 2}H {sub x} and C{sub 3}H {sub x} chemical families in the lower stratosphere. More generally, there appears to be much greater ubiquity and relative abundance of triple-bonded species than double-bonded, likely due to the greater resistance of triple bonds to photolysis and chemical attack.

  19. Interdiffusion effect on strained La0.8Ba0.2MnO3 thin films by off-axis sputtering on SrTiO3 (100) substrates

    International Nuclear Information System (INIS)

    Chou, Hsiung; Hsu, S. G.; Lin, C. B.; Wu, C. B.

    2007-01-01

    Strained La 0.8 Ba 0.2 MnO 3 thin films on SrTiO 3 (100) substrate are grown by an off-axis sputtering technique. It is found that the ferromagnetic temperature T C increases for thinner films. Secondary ion mass spectroscopy indicates that Sr diffuses partially into the film, making it structurally nonuniform. The region close to the film/substrate interface acts as La 1-x (Sr y Ba 1-y ) x MnO 3 with a near negligible y for the as grown film and a non-negligible amount of y for the high-temperature postannealed film. The enhancement of T C is attributed to the combination of the strain and interdiffusion effects

  20. Interdiffusion effect on strained La0.8Ba0.2MnO3 thin films by off-axis sputtering on SrTiO3 (100) substrates

    Science.gov (United States)

    Chou, Hsiung; Hsu, S. G.; Lin, C. B.; Wu, C. B.

    2007-02-01

    Strained La0.8Ba0.2MnO3 thin films on SrTiO3 (100) substrate are grown by an off-axis sputtering technique. It is found that the ferromagnetic temperature TC increases for thinner films. Secondary ion mass spectroscopy indicates that Sr diffuses partially into the film, making it structurally nonuniform. The region close to the film/substrate interface acts as La1-x(SryBa1-y)xMnO3 with a near negligible y for the as grown film and a non-negligible amount of y for the high-temperature postannealed film. The enhancement of TC is attributed to the combination of the strain and interdiffusion effects.

  1. Spectroscopic detection and mapping of vinyl cyanide on Titan

    Science.gov (United States)

    Cordiner, Martin; Yukiko Palmer, Maureen; Lai, James; Nixon, Conor A.; Teanby, Nicholas; Charnley, Steven B.; Vuitton, Veronique; Kisiel, Zbigniew; Irwin, Patrick; Molter, Ned; Mumma, Michael J.

    2017-10-01

    The first spectroscopic detection of vinyl cyanide (otherwise known as acrylonitrile; C2H3CN) on Titan was obtained by Palmer et al. (2017), based on three rotational emission lines observed with ALMA at millimeter wavelengths (in receiver band 6). The astrobiological significance of this detection was highlighted due to the theorized ability of C2H3CN molecules to combine into cell membrane-like structures under the cold conditions found in Titan's hydrocarbon lakes. Here we report the detection of three additional C2H3CN transitions at higher frequencies (from ALMA band 7 flux calibration data). We present the first emission maps for this gas on Titan, and compare the molecular distribution with that of other nitriles observed with ALMA including HC3N, CH3CN, C2H5CN and HNC. The molecular abundance patterns are interpreted based on our understanding of Titan's high-altitude photochemistry and time-variable global circulation. Similar to the short-lived HC3N molecule, vinyl cyanide is found to be most abundant in the vicinity of the southern (winter) pole, whereas the longer-lived CH3CN is more concentrated in the north. The vertical abundance profile of C2H3CN (from radiative transfer modeling), as well as its latitudinal distribution, are consistent with a short photochemical lifetime for this species. Complementary results from our more recent (2017) nitrile mapping studies at higher spatial resolution will also be discussed.REFERENCES:Palmer, M. Y., Cordiner, M. A., Nixon, C. A. et al. "ALMA detection and astrobiological potential of vinyl cyanide on Titan", Sci. Adv. 2017, 3, e1700022

  2. Mission Techniques for Exploring Saturn's icy moons Titan and Enceladus

    Science.gov (United States)

    Reh, Kim; Coustenis, Athena; Lunine, Jonathan; Matson, Dennis; Lebreton, Jean-Pierre; Vargas, Andre; Beauchamp, Pat; Spilker, Tom; Strange, Nathan; Elliott, John

    2010-05-01

    The future exploration of Titan is of high priority for the solar system exploration community as recommended by the 2003 National Research Council (NRC) Decadal Survey [1] and ESA's Cosmic Vision Program themes. Cassini-Huygens discoveries continue to emphasize that Titan is a complex world with very many Earth-like features. Titan has a dense, nitrogen atmosphere, an active climate and meteorological cycles where conditions are such that the working fluid, methane, plays the role that water does on Earth. Titan's surface, with lakes and seas, broad river valleys, sand dunes and mountains was formed by processes like those that have shaped the Earth. Supporting this panoply of Earth-like processes is an ice crust that floats atop what might be a liquid water ocean. Furthermore, Titan is rich in very many different organic compounds—more so than any place in the solar system, except Earth. The Titan Saturn System Mission (TSSM) concept that followed the 2007 TandEM ESA CV proposal [2] and the 2007 Titan Explorer NASA Flagship study [3], was examined [4,5] and prioritized by NASA and ESA in February 2009 as a mission to follow the Europa Jupiter System Mission. The TSSM study, like others before it, again concluded that an orbiter, a montgolfiѐre hot-air balloon and a surface package (e.g. lake lander, Geosaucer (instrumented heat shield), …) are very high priority elements for any future mission to Titan. Such missions could be conceived as Flagship/Cosmic Vision L-Class or as individual smaller missions that could possibly fit within NASA's New Frontiers or ESA's Cosmic Vision M-Class budgets. As a result of a multitude of Titan mission studies, several mission concepts have been developed that potentially fit within various cost classes. Also, a clear blueprint has been laid out for early efforts critical toward reducing the risks inherent in such missions. The purpose of this paper is to provide a brief overview of potential Titan (and Enceladus) mission

  3. Titan's Methane Cycle is Closed

    Science.gov (United States)

    Hofgartner, J. D.; Lunine, J. I.

    2013-12-01

    Doppler tracking of the Cassini spacecraft determined a polar moment of inertia for Titan of 0.34 (Iess et al., 2010, Science, 327, 1367). Assuming hydrostatic equilibrium, one interpretation is that Titan's silicate core is partially hydrated (Castillo-Rogez and Lunine, 2010, Geophys. Res. Lett., 37, L20205). These authors point out that for the core to have avoided complete thermal dehydration to the present day, at least 30% of the potassium content of Titan must have leached into an overlying water ocean by the end of the core overturn. We calculate that for probable ammonia compositions of Titan's ocean (compositions with greater than 1% ammonia by weight), that this amount of potassium leaching is achievable via the substitution of ammonium for potassium during the hydration epoch. Formation of a hydrous core early in Titan's history by serpentinization results in the loss of one hydrogen molecule for every hydrating water molecule. We calculate that complete serpentinization of Titan's core corresponds to the release of more than enough hydrogen to reconstitute all of the methane atoms photolyzed throughout Titan's history. Insertion of molecular hydrogen by double occupancy into crustal clathrates provides a storage medium and an opportunity for ethane to be converted back to methane slowly over time--potentially completing a cycle that extends the lifetime of methane in Titan's surface atmosphere system by factors of several to an order of magnitude over the photochemically-calculated lifetime.

  4. Poster 7: Could PAH or HAC explain the Titan's stratosphere absorption around 3.4 µm revealed by solar occultations?

    Science.gov (United States)

    Cordier, Daniel; Cours, Thibaud; Rey, Michael; Maltagliati, Luca; Seignovert, Benoit; Biennier, Ludovic

    2016-06-01

    In 2006, during Cassini's 10th flyby of Titan (T10), Bellucci et al. (2009) observed a solar occultation by Titan's atmosphere through the solar port of the Cassini/VIMS instrument. These authors noticed the existence of an unexplained additional absorption superimposed to the CH4 3.3 µm band. Because they were unable to model this absorption with gases, they attributed this intriguing feature to the signature of solid state organic components. Kim et al. (2011) revisited the data collected by Bellucci et al. (2009) and they considered the possible contribution of aerosols formed by hydrocarbon ices. They specifically took into account C2H6, CH4, CH3CN, C5H12 and C6H12 ices. More recently, Maltagliati et al. (2015) analyzed a set of four VIMS solar occultations, corresponding to flybys performed between January 2006 and September 2011 at different latitudes. They confirmed the presence of the 3.3 µm absorption in all occultations and underlined the possible importance of gaseous ethane, which has a strong plateau of absorption lines in that wavelength range.In this work, we show that neither hydrocarbon ices nor molecular C2H6 cannot satisfactorily explain the observed absorption. Our simulations speak in favor of an absorption due to the presence of PAH molecules or HAC in the stratosphere of Titan. PAH have been already considered by Lopes-Puertas et al. (2013) at altitudes larger than ˜900 km and tentatively identified in the stratosphere by Maltagliati et al. (2015); PAH and HAC are good candidates for Titan's aerosols precursors.

  5. Growth and characterization of epitaxial anatase TiO2(001) on SrTiO3-buffered Si(001) using atomic layer deposition

    International Nuclear Information System (INIS)

    McDaniel, M.D.; Posadas, A.; Wang, T.; Demkov, A.A.; Ekerdt, J.G.

    2012-01-01

    Epitaxial anatase titanium dioxide (TiO 2 ) films have been grown by atomic layer deposition (ALD) on Si(001) substrates using a strontium titanate (STO) buffer layer grown by molecular beam epitaxy (MBE) to serve as a surface template. The growth of TiO 2 was achieved using titanium isopropoxide and water as the co-reactants at a substrate temperature of 225–250 °C. To preserve the quality of the MBE-grown STO, the samples were transferred in-situ from the MBE chamber to the ALD chamber. After ALD growth, the samples were annealed in-situ at 600 °C in vacuum (10 −7 Pa) for 1–2 h. Reflection high-energy electron diffraction was performed during the MBE growth of STO on Si(001), as well as after deposition of TiO 2 by ALD. The ALD films were shown to be highly ordered with the substrate. At least four unit cells of STO must be present to create a stable template on the Si(001) substrate for epitaxial anatase TiO 2 growth. X-ray diffraction revealed that the TiO 2 films were anatase with only the (004) reflection present at 2θ = 38.2°, indicating that the c-axis is slightly reduced from that of anatase powder (2θ = 37.9°). Anatase TiO 2 films up to 100 nm thick have been grown that remain highly ordered in the (001) direction on STO-buffered Si(001) substrates. - Highlights: ► Epitaxial anatase films are grown by atomic layer deposition (ALD) on Si(001). ► Four unit cells of SrTiO 3 on silicon create a stable template for ALD. ► TiO 2 thin films have a compressed c-axis and an expanded a-axis. ► Up to 100 nm thick TiO 2 films remain highly ordered in the (001) direction.

  6. ZnO Nanorods on a LaAlO 3 -SrTiO 3 Interface: Hybrid 1D-2D Diodes with Engineered Electronic Properties

    KAUST Repository

    Bera, Ashok

    2015-12-28

    Integrating nanomaterials with different dimensionalities and properties is a versatile approach toward realizing new functionalities in advanced devices. Here, a novel diode-type heterostructure is reported consisting of 1D semiconducting ZnO nanorods and 2D metallic LaAlO3-SrTiO3 interface. Tunable insulator-to-metal transitions, absent in the individual components, are observed as a result of the competing temperature-dependent conduction mechanisms. Detailed transport analysis reveals direct tunneling at low bias, Fowler-Nordheim tunneling at high forward bias, and Zener breakdown at high reverse bias. Our results highlight the rich electronic properties of such artificial diodes with hybrid dimensionalities, and the design principle may be generalized to other nanomaterials. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. ZnO Nanorods on a LaAlO 3 -SrTiO 3 Interface: Hybrid 1D-2D Diodes with Engineered Electronic Properties

    KAUST Repository

    Bera, Ashok; Lin, Weinan; Yao, Yingbang; Ding, Junfeng; Lourembam, James; Wu, Tao

    2015-01-01

    Integrating nanomaterials with different dimensionalities and properties is a versatile approach toward realizing new functionalities in advanced devices. Here, a novel diode-type heterostructure is reported consisting of 1D semiconducting ZnO nanorods and 2D metallic LaAlO3-SrTiO3 interface. Tunable insulator-to-metal transitions, absent in the individual components, are observed as a result of the competing temperature-dependent conduction mechanisms. Detailed transport analysis reveals direct tunneling at low bias, Fowler-Nordheim tunneling at high forward bias, and Zener breakdown at high reverse bias. Our results highlight the rich electronic properties of such artificial diodes with hybrid dimensionalities, and the design principle may be generalized to other nanomaterials. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Microstructural Characterisation of Cuprate/Manganate Films on (110) SrTiO3 Deposited by Laser Ablation

    International Nuclear Information System (INIS)

    Tse, Y Y; Chakalov, R I; Joshi, M M; Jones, I P; Muirhead, C M; Palai, R

    2006-01-01

    Cross-sectional TEM and microanalysis were carried out to understand at a microscopic level the effects of microstructure and chemistry on the physical properties of manganites and manganite/cuprate films. TEM observations on pure LCMO grown on a (110) STO substrate were carried out first to determine the defect structure and detect any formation of second phase precipitates, as well as microstructural changes not detectable by X-ray reflections. La 0.7 Ca 0.3 MnO 3 (LCMO) grows epitaxially on a (110) SrTiO 3 (STO) substrate. HRTEM reveals a nearly defect-free interface between LCMO and STO with a few irregularly arranged misfit dislocations. The microstructure obtained from laser ablated nanometre scaled La 0.7 Ca 0.3 MnO 3 (LCMO)/YBa 2 Cu 3 O 7 -δ (YBCO)/PrBa 2 Cu 3 O 7 (PBCO) multilayers on (110) STO was also studied. Diffraction patterns show that all films grow epitaxially on top of the (110) STO substrate, with the c-axis of YBCO in plane. There is a roughness of about 10nm between PBCO and YBCO and the roughness is increased at the YBCO - LCMO interface

  9. Titan Polar Landscape Evolution

    Science.gov (United States)

    Moore, Jeffrey M.

    2016-01-01

    With the ongoing Cassini-era observations and studies of Titan it is clear that the intensity and distribution of surface processes (particularly fluvial erosion by methane and Aeolian transport) has changed through time. Currently however, alternate hypotheses substantially differ among specific scenarios with respect to the effects of atmospheric evolution, seasonal changes, and endogenic processes. We have studied the evolution of Titan's polar region through a combination of analysis of imaging, elevation data, and geomorphic mapping, spatially explicit simulations of landform evolution, and quantitative comparison of the simulated landscapes with corresponding Titan morphology. We have quantitatively evaluated alternate scenarios for the landform evolution of Titan's polar terrain. The investigations have been guided by recent geomorphic mapping and topographic characterization of the polar regions that are used to frame hypotheses of process interactions, which have been evaluated using simulation modeling. Topographic information about Titan's polar region is be based on SAR-Topography and altimetry archived on PDS, SAR-based stereo radar-grammetry, radar-sounding lake depth measurements, and superposition relationships between geomorphologic map units, which we will use to create a generalized topographic map.

  10. Titan's methane clock

    Science.gov (United States)

    Nixon, C. A.; Jennings, D. E.; Romani, P. N.; Teanby, N. A.; Irwin, P. G. J.; Flasar, F. M.

    2010-04-01

    Measurements of the 12C/13C and D/H isotopic ratios in Titan's methane show intriguing differences from the values recorded in the giant planets. This implies that either (1) the atmosphere was differently endowed with material at the time of formation, or (2) evolutionary processes are at work in the moon's atmosphere - or some combination of the two. The Huygens Gas Chromatograph Mass Spectrometer Instrument (GCMS) found 12CH4/13CH4 = 82 +/- 1 (Niemann et al. 2005), some 7% lower than the giant planets' value of 88 +/- 7 (Sada et al. 1996), which closely matches the terrestrial inorganic standard of 89. The Cassini Composite Infrared Spectrometer (CIRS) has previously reported 12CH4/13CH4 of 77 +/-3 based on nadir sounding, which we now revise upwards to 80 +/- 4 based on more accurate limb sounding. The CIRS and GCMS results are therefore in agreement about an overall enrichment in 13CH4 of ~10%. The value of D/H in Titan's CH4 has long been controversial: historical measurements have ranged from about 8-15 x 10-5 (e.g. Coustenis et al. 1989, Coustenis et al. 2003). A recent measurement based on CIRS limb data by Bezard et al. (2007) puts the D/H in CH4 at (13 +/- 1) x 10-5, very much greater than in Jupiter and Saturn, ~2 x 10-5 (Mahaffy et al. 1998, Fletcher et al. 2009). To add complexity, the 12C/13C and D/H vary among molecules in Titan atmosphere, typically showing enhancement in D but depletion in 13C in the daughter species (H2, C2H2, C2H6), relative to the photochemical progenitor, methane. Jennings et al. (2009) have sought to interpret the variance in carbon isotopes as a Kinetic Isotope Effect (KIE), whilst an explanation for the D/H in all molecules remains elusive (Cordier et al. 2008). In this presentation we argue that evolution of isotopic ratios in Titan's methane over time forms a ticking 'clock', somewhat analogous to isotopic ratios in geochronology. Under plausible assumptions about the initial values and subsequent replenishment, various

  11. Activation and waste disposal of the TITAN RFP [reversed-field-pinch] reactors

    International Nuclear Information System (INIS)

    Cheng, E.T.; Conn, R.W.

    1988-01-01

    The TITAN-I lithium self-cooled and TITAN-II aqueous lithium nitrate solution-cooled fusion reactors are based on the reversed-field-pinch (RFP) toroidal confinement concept and operate at high power density with an 18.1 MW/m 2 neutron wall loading. These designs were analyzed to study the activation and waste disposal aspects of such high-power density reactors. It was found that because of the use of V-3Ti-1Si (TITAN-I) and reduced activation ferritic steel (TITAN-II) as structural alloys for the first wall, blanket, reflector, and shield components, all the TITAN components except the divertor collector plates can be classified as shallow-land burial (10CFR61 Class C or better) nuclear waste for disposal, provided that the impurity elements, niobium and molybdenum, can be controlled below about 1 and 0.3 appm levels, respectively. The average annual disposal masses were estimated to be 150 and 96 tonnes, respectively, for the 1,000 MW TITAN-I and TITAN-II reactors. This corresponds to about 11% of the total mass in the fusion power core of both reactors. The divertor collector plates are fabricated with tungsten because of its low particle sputtering properties. These divertor collector plates in the TITAN-I reactor will be qualified as Class C waste after 18.1 MW-y/m 2 operation. The waste disposal rating of the divertor collector plates in the TITAN-II reactor, however, is estimated to be a factor of 4 higher than allowed for Class C disposal, because of the soft neutron spectrum in the beryllium environment. The annual disposal mass of this non-Class C waste is 0.35 tons, about 0.04% of the average annual discharge mass for the TITAN-II reactor. An additional 74 m 3 annual discharge of Class C waste containing 14 C may be needed for the TITAN-II reactor because of the use of nitrate salt in the aqueous coolant as the tritium breeder. 13 refs., 6 tabs

  12. Absence of confinement in (SrTiO3)/( SrTi0.8Nb0.2O3 ) superlattices

    Science.gov (United States)

    Bouzerar, G.; Thébaud, S.; Bouzerar, R.; Pailhès, S.; Adessi, Ch.

    2018-03-01

    The reduction of dimensionality is considered an efficient pathway to boost the performances of thermoelectric materials. Quantum confinement of the carriers is expected to induce large Seebeck coefficients (S ) and it also suppresses the thermal conductivity by increasing the phonon scattering processes. However, quantum confinement in superlattices is not always easy to achieve and needs to be carefully validated. In the past decade, large values of S have been measured in (SrTiO3)/(SrTi0.8Nb0.2O3 ) superlattices [H. Ohta et al., Nat. Mater. 6, 129 (2007), 10.1038/nmat1821; Y. Mune et al., Appl. Phys. Lett. 91, 192105 (2007), 10.1063/1.2809364]. In the δ -doped compound, the reported S was almost six times larger than that of the bulk material. This huge increase has been attributed to the two-dimensional carrier confinement in the doped regions. Here, we demonstrate that the experimental data are well explained quantitatively assuming delocalized electrons in both in-plane and growth directions. Moreover, we rule out the confined electron hypothesis whose signature would be the suppression of the Seebeck coefficient. This strongly suggests that the presupposed confinement picture in these superlattices is unlikely.

  13. Ferroelectricity-induced resistive switching in Pb(Zr0.52Ti0.48)O3/Pr0.7Ca0.3MnO3/Nb-doped SrTiO3 epitaxial heterostructure

    Science.gov (United States)

    Md. Sadaf, Sharif; Mostafa Bourim, El; Liu, Xinjun; Hasan Choudhury, Sakeb; Kim, Dong-Wook; Hwang, Hyunsang

    2012-03-01

    We investigated the effect of a ferroelectric Pb(Zr0.52Ti0.48)O3 (PZT) thin film on the generation of resistive switching in a stacked Pr0.7Ca0.3MnO3 (PCMO)/Nb-doped SrTiO3 (Nb:STO) heterostructure forming a p-n junction. To promote the ferroelectric effect, the thin PZT active layer was deposited on an epitaxially grown p-type PCMO film on a lattice-matched n-type Nb:STO single crystal. It was concluded that the observed resistive switching behavior in the all-perovskite Pt/PZT/PCMO/Nb:STO heterostructure was related to the modulation of PCMO/Nb:STO p-n junction's depletion width, which was caused either by the PZT ferroelectric polarization field effect, the electrochemical drift of oxygen ions under an electric field, or both simultaneously.

  14. Sintering, microstructure and electrical conductivity of gadolinia-doped ceria with SrO, TiO2 and SrTiO3

    International Nuclear Information System (INIS)

    Dias, Maria Cely Freitas

    2013-01-01

    Ceria containing trivalent rare-earths is a solid electrolyte with higher ionic conductivity than the standard yttria fully-stabilized zirconia ionic conductor. This property turns these ceria-based ionic conductors promising materials for application in solid oxide fuel cells operating at intermediate temperatures (500-700 deg C). One of the most utilized approaches to optimize the electrical conductivity and other properties of these materials is the introduction of a second additive. In this work, ceria-20 mol% gadolinia with additions of 1, 2.5 and 5 mol% of SrO, TiO 2 and SrTiO 3 as co-additives were prepared by solid state reaction. The main purpose was to investigate the effects of the co-additives on densification, microstructure and electrical conductivity of the solid electrolyte. Sintered pellets were characterized by apparent density, X-ray diffraction, Raman spectroscopy, scanning electron microscopy and electrical conductivity by impedance spectroscopy. The additives were found to exert different influences in all studied properties. The way they influence the solid electrolyte properties depends on the type and content of the additive. SrO addition to doped ceria improves the intergranular conductivity, but decreases the apparent density of the pellets. Increase of densification was obtained with TiO 2 addition. This additive promotes increase of the blocking of charge carriers at the grain boundaries due to solute exsolution and formation of the pyrochlore Gd 2 Ti 2 O 7 phase at grain boundaries for contents in excess of the solubility limit. No influence on densification was found for SrTiO 3 additions. (author)

  15. Interaction of Titan's atmosphere with Saturn's magnetosphere

    International Nuclear Information System (INIS)

    Hartle, R.E.

    1985-01-01

    The Voyager 1 measurements made during the Titan flyby reveal that Saturn's rotating magnetospheric plasma interacts directly with Titan's neutral atmosphere and ionosphere. This results from the lack of an intrinsic magnetic field at Titan. The interaction induces a magnetosphere which deflects the flowing plasma around Titan and forms a plasma wake downstream. Within the tail of the induced magnetosphere, ions of ionospheric origin flow away from Titan. Just outside Titan's magnetosphere, a substantial ion-exosphere forms from an extensive hydrogen-nitrogen exosphere. The exospheric ions are picked up and carried downstream into the wake by the plasma flowing around Titan. Mass loading produced by the addition of exospheric ions slows the wake plasma down considerably in the vicinity of the magnetopause. 36 references

  16. On low temperature glide of dissociated 〈1 1 0〉 dislocations in strontium titanate

    Science.gov (United States)

    Ritterbex, Sebastian; Hirel, Pierre; Carrez, Philippe

    2018-05-01

    An elastic interaction model is presented to quantify low temperature plasticity of SrTiO3 via glide of dissociated 〈1 1 0〉{1 1 0} screw dislocations. Because 〈1 1 0〉 dislocations are dissociated, their glide, controlled by the kink-pair mechanism at T good quantitative agreement with the observed non-monotonic mechanical behaviour of SrTiO3. This agreement allows to explain the experimental results in terms of a (progressive) change in 〈1 1 0〉{1 1 0} glide mechanism, from simultaneous nucleation of two kink-pairs along both partials at low stress, towards nucleation of single kink-pairs on individual partials if resolved shear stress exceeds a critical value of 95 MPa. High resolved shear stress allows thus for the activation of extra nucleation mechanisms on dissociated dislocations impossible to occur under the sole action of thermal activation. We suggest that stress condition in conjunction with core dissociation is key to the origin of non-monotonic plastic behaviour of SrTiO3 at low temperatures.

  17. Volatile products controlling Titan's tholins production

    KAUST Repository

    Carrasco, Nathalie

    2012-05-01

    A quantitative agreement between nitrile relative abundances and Titan\\'s atmospheric composition was recently shown with a reactor simulating the global chemistry occurring in Titan\\'s atmosphere (Gautier et al. [2011]. Icarus, 213, 625-635). Here we present a complementary study on the same reactor using an in situ diagnostic of the gas phase composition. Various initial N 2/CH 4 gas mixtures (methane varying from 1% to 10%) are studied, with a monitoring of the methane consumption and of the stable gas neutrals by in situ mass spectrometry. Atomic hydrogen is also measured by optical emission spectroscopy. A positive correlation is found between atomic hydrogen abundance and the inhibition function for aerosol production. This confirms the suspected role of hydrogen as an inhibitor of heterogeneous organic growth processes, as found in Sciamma-O\\'Brien et al. (Sciamma-O\\'Brien et al. [2010]. Icarus, 209, 704-714). The study of the gas phase organic products is focussed on its evolution with the initial methane amount [CH 4] 0 and its comparison with the aerosol production efficiency. We identify a change in the stationary gas phase composition for intermediate methane amounts: below [CH 4] 0=5%, the gas phase composition is mainly dominated by nitrogen-containing species, whereas hydrocarbons are massively produced for [CH 4] 0>5%. This predominance of N-containing species at lower initial methane amount, compared with the maximum gas-to solid conversion observed in Sciamma-O\\'Brien et al. (2010) for identical methane amounts confirms the central role played by N-containing gas-phase compounds to produce tholins. Moreover, two protonated imines (methanimine CH 2NH and ethanamine CH 3CHNH) are detected in the ion composition in agreement with Titan\\'s INMS measurements, and reinforcing the suspected role of these chemical species on aerosol production. © 2012 Elsevier Inc.

  18. Investigation on corrosion resistance of metal superficially modified with alkoxy titanates

    International Nuclear Information System (INIS)

    Yao Kangde; Song Shizhe; Shen Ningxiang

    1991-01-01

    A study has been made in order to determine corrosion protection performance of alkoxy titanate modified iron in a 3% NaCl solution. The effectiveness of alkoxy titanates as corrosion retarders for chloride environments is confirmed by both stepped potential sweep technique and electrochemical impedance spectroscopy (EIS). Ion microanalysis (IMA) depth profiles are used to elucidate the corrosion inhibitive action of different alkoxy titanate. (orig.)

  19. Modified titanate perovskites in photocatalytic water splitting

    Energy Technology Data Exchange (ETDEWEB)

    Wlodarczak, M.; Ludwiczak, M.; Laniecki, M. [A. Mickiewicz Univ. (Poland)

    2010-07-01

    Received materials have structure of perovskite, what was shown by XRD diffraction patterns. Perovskite structure is present in all samples with strontium, barium and one sample with calcium. Moreover, received barium and strontium titanate are very similar to pattern materials. XRD results show, that temperature 500 C is too low to create perovskite structure in CaTiO{sub 3}. However, it is high enough in case of SrTiO{sub 3} and BaTiO{sub 3}. One regularity is obvious, surface area increases for samples calcined in lower temperature. There is a connection between surface area and dispersion of platinum. Both of them reach the greatest value to the calcium titanate. Catalytic activity was shown by all of received samples. Measurable values were received to samples calcined in 700 C. Calcium titanate had the best catalytic activity, both an amount of hydrogen and a ratio of hydrogen to platinum. There is one regularity to all samples, the ration of hydrogen to platinum increase when amount of platinum decrease. (orig.)

  20. Iron-catalyzed oxidative biaryl cross-couplings via mixed diaryl titanates: significant influence of the order of combining aryl Grignard reagents with titanate.

    Science.gov (United States)

    Liu, Kun Ming; Wei, Juan; Duan, Xin Fang

    2015-03-18

    The mixed diaryl titanates were used for the first time to modify the reactivity of two aryl Grignard reagents. Two titanate intermediates, Ar[Ar'Ti(OR)3]MgX and Ar'[ArTi(OR)3]MgX, formed via alternating the sequence of combining Grignard reagents with ClTi(OR)3 showed a significant reactivity difference. Taking advantage of such different reactivity, two highly structurally similar aryl groups could be facilely assembled through iron-catalyzed oxidative cross-couplings using oxygen as the oxidant.

  1. Titanic: A Statistical Exploration.

    Science.gov (United States)

    Takis, Sandra L.

    1999-01-01

    Uses the available data about the Titanic's passengers to interest students in exploring categorical data and the chi-square distribution. Describes activities incorporated into a statistics class and gives additional resources for collecting information about the Titanic. (ASK)

  2. The age of Titan's surface

    Science.gov (United States)

    Neish, C. D.; Lorenz, R. D.

    2010-04-01

    High-resolution images of the surface of Titan taken by the Cassini spacecraft reveal a world with an extreme paucity of impact craters. Planetary surfaces are commonly dated by dividing the number of impact craters by the estimated impactor flux, but this approach has been confounded at Titan by several difficulties. First, high-resolution imaging of the surface of Titan is far from complete (in the near-infrared as well as radar). As of December 2007, Cassini RADAR images covered only 22% of its surface. However, we can use Monte-Carlo models to explore how many craters of a given size (with large or very large craters being of particular interest) may be present in the unobserved areas. Second, literature descriptions of the crater formation rate (e.g. Korycansky and Zahnle 2005 and Artemieva and Lunine 2005) are apparently not in agreement. We discuss possible resolutions. Third, since surface modification processes are ongoing, the actual number of craters on Titan's surface remains uncertain, as craters may be eroded beyond recognition, or obscured by lakes or sand seas. In this connection, we use the Earth as an analogue. The Earth is in many ways the most "Titan-like" world in the solar system, with extensive modification by erosion, burial, tectonism, and volcanism. We compare the observed number of terrestrial craters to the expected terrestrial impactor flux to determine the crater reduction factor for a world similar to Titan. From this information, we can back out the actual number of craters on Titan's surface and estimate its crater retention age. An accurate age estimate will be critical for constraining models of Titan's formation and evolution.

  3. The Titan Sky Simulator ™ - Testing Prototype Balloons in Conditions Approximating those in Titan's Atmosphere

    Science.gov (United States)

    Nott, Julian

    This paper will describe practical work flying prototype balloons in the "The Titan Sky Simulator TM " in conditions approximating those found in Titan's atmosphere. Saturn's moon, Titan, is attracting intense scientific interest. This has led to wide interest in exploring it with Aerobots, balloons or airships. Their function would be similar to the Rovers exploring Mars, but instead of moving laboriously across the rough terrain on wheels, they would float freely from location to location. To design any balloon or airship it is essential to know the temperature of the lifting gas as this influences the volume of the gas, which in turn influences the lift. To determine this temperature it is necessary to know how heat is transferred between the craft and its surroundings. Heat transfer for existing balloons is well understood. However, Titan conditions are utterly different from those in which balloons have ever been flown, so heat transfer rates cannot currently be calculated. In particular, thermal radiation accounts for most heat transfer for existing balloons but over Titan heat transfer will be dominated by convection. To be able to make these fundamental calculations, it is necessary to get fundamental experimental data. This is being obtained by flying balloons in a Simulator filled with nitrogen gas at very low temperature, about 95° K / minus 180° C, typical of Titan's temperatures. Because the gas in the Simulator is so cold, operating at atmospheric pressure the density is close to that of Titan's atmosphere. "The Titan Sky Simulator TM " has an open interior approximately 4.5 meter tall and 2.5 meters square. It has already been operated at 95° K/-180° C. By the time of the Conference it is fully expected to have data to present from actual balloons flying at this temperature. Perhaps the most important purpose of this testing is to validate numerical [computational fluid dynamics] models being developed by Tim Colonius of Caltech. These numerical

  4. Calcium titanate (CaTiO{sub 3}) dielectrics prepared by plasma spray and post-deposition thermal treatment

    Energy Technology Data Exchange (ETDEWEB)

    Ctibor, Pavel [Materials Engineering Department, Institute of Plasma Physics ASCR, v.v.i., Za Slovankou 3, Prague 8 (Czech Republic); Kotlan, Jiri, E-mail: kotlan@ipp.cas.cz [Materials Engineering Department, Institute of Plasma Physics ASCR, v.v.i., Za Slovankou 3, Prague 8 (Czech Republic); Department of Electrotechnology, Faculty of Electrical Engineering, Czech Technical University in Prague, Technicka 2, Prague 6 (Czech Republic); Pala, Zdenek [Materials Engineering Department, Institute of Plasma Physics ASCR, v.v.i., Za Slovankou 3, Prague 8 (Czech Republic); Sedlacek, Josef [Department of Electrotechnology, Faculty of Electrical Engineering, Czech Technical University in Prague, Technicka 2, Prague 6 (Czech Republic); Hajkova, Zuzana; Grygar, Tomas Matys [Institute of Inorganic Chemistry ASCR, v.v.i., Husinec-Rez 1001, Rez (Czech Republic)

    2015-12-15

    Highlights: • Calcium titanate was sprayed by two different plasma spray systems. • Significant improvement of dielectric properties after annealing was observed. • Calcium titanate self-supporting parts can be fabricated by plasma spraying. - Abstract: This paper studies calcium titanate (CaTiO{sub 3}) dielectrics prepared by plasma spray technology. A water stabilized plasma gun (WSP) as well as a widely used gas stabilized plasma gun (GSP) were employed in this study to deposit three sample sets at different spray conditions. Prepared specimens were annealed in air at atmospheric pressure for 2 h at various temperatures from 530 to 1170 °C. X-ray diffraction (XRD), Raman spectroscopy and porosity measurements were used for sample characterization. Dielectric spectroscopy was applied to obtain relative permittivity, conductivity and loss factor frequency dependence. Band gap energy was estimated from reflectance measurements. The work is focused on the explanation of changes in microstructure and properties of a plasma sprayed deposit after thermal annealing. Obtained results show significant improvement of dielectric properties after thermal annealing.

  5. Aerosol chemistry in Titan's ionosphere: simultaneous growth and etching processes

    Science.gov (United States)

    Carrasco, Nathalie; Cernogora, Guy; Jomard, François; Etcheberry, Arnaud; Vigneron, Jackie

    2016-10-01

    Since the Cassini-CAPS measurements, organic aerosols are known to be present and formed at high altitudes in the diluted and partially ionized medium that is Titan's ionosphere [1]. This unexpected chemistry can be further investigated in the laboratory with plasma experiments simulating the complex ion-neutral chemistry starting from N2-CH4 [2]. Two sorts of solid organic samples can be produced in laboratory experiments simulating Titan's atmospheric reactivity: grains in the volume and thin films on the reactor walls. We expect that grains are more representative of Titan's atmospheric aerosols, but films are used to provide optical indices for radiative models of Titan's atmosphere.The aim of the present study is to address if these two sorts of analogues are chemically equivalent or not, when produced in the same N2-CH4 plasma discharge. The chemical compositions of both these materials are measured by using elemental analysis, XPS analysis and Secondary Ion Mass Spectrometry. We find that films are homogeneous but significantly less rich in nitrogen and hydrogen than grains produced in the same experimental conditions. This surprising difference in their chemical compositions is explained by the efficient etching occurring on the films, which stay in the discharge during the whole plasma duration, whereas the grains are ejected after a few minutes [3]. The impact for our understanding of Titan's aerosols chemical composition is important. Our study shows that chemical growth and etching process are simultaneously at stake in Titan's ionosphere. The more the aerosols stay in the ionosphere, the more graphitized they get through etching process. In order to infer Titan's aerosols composition, our work highlights a need for constraints on the residence time of aerosols in Titan's ionosphere. [1] Waite et al. (2009) Science , 316, p. 870[2] Szopa et al. (2006) PSS, 54, p. 394[3] Carrasco et al. (2016) PSS, 128, p. 52

  6. The atmospheric temperature structure of Titan

    Science.gov (United States)

    Mckay, Christopher P.; Pollack, J. B.; Courtin, Regis; Lunine, Jonathan I.

    1992-01-01

    The contribution of various factors to the thermal structure of Titan's past and present atmosphere are discussed. A one dimensional model of Titan's thermal structure is summarized. The greenhouse effect of Titan's atmosphere, caused primarily by pressure induced opacity of N2, CH4, and H2, is discussed together with the antigreenhouse effect dominated by the haze which absorbs incident sunlight. The implications for the atmosphere of the presence of an ocean on Titan are also discussed.

  7. Structure/Property Relationships for Sol-gel Derived YBa2Cu3O7-d and SrTiO3 Films

    Science.gov (United States)

    Dawley, Jeff; Clem, Paul; Siegal, Michael; Overmyer, Don

    2001-03-01

    Solution deposition of c-axis oriented YBa2Cu3O7-d (YBCO) films on buffered RABiT substrates is a potential method for rapid, low cost production of superconducting tapes for power transmission and other applications. For this work, 100-250 nm thick YBCO and SrTiO3 (STO) films have been prepared by spin-coating and dip-coating sol-gel solutions onto LaAlO3 (100) and RABiT Ni (200) substrates. Biaxially textured STO coatings have been deposited on LaAlO3 and RABiT Ni by using a "templating" technique and controlling growth temperature and pO2. YBCO films grown on STO coated LaAlO3 possess comparable superconducting properties to YBCO films grown directly on LaAlO3 ( 1 MA/cm2 at 77K), indicating that a high quality STO layer does not degrade the crystalline quality of the YBCO. The effects of processing parameters on the STO buffer layer and novel processing techniques for decreasing the processing time and simplifying the integration of sol-gel YBCO with Ni substrates will be discussed. Sandia is a multiprogram laboratory operated by Sandia Corp., a Lockheed Martin Company, for the US Dept. Of Energy under contract DE-AC04-94A185000.

  8. Acetylene on Titan

    Science.gov (United States)

    Singh, Sandeep; McCord, Thomas B.; Combe, Jean-Philippe; Rodriguez, Sebastien; Cornet, Thomas; Le Mouélic, Stéphane; Clark, Roger Nelson; Maltagliati, Luca; Chevrier, Vincent

    2016-10-01

    Saturn's moon Titan possesses a thick atmosphere that is mainly composed of N2 (98%), CH4 (2 % overall, but 4.9% close to the surface) and less than 1% of minor species, mostly hydrocarbons [1]. A dissociation of N2 and CH4 forms complex hydrocarbons in the atmsophere and acetylene (C2H2) and ethane (C2H6) are produced most abundently. Since years, C2H2 has been speculated to exist on the surface of Titan based on its high production rate in the stratosphere predicted by photochemical models [2,3] and from its detection as trace gas sublimated/evaporated from the surface after the landing of the Huygens probe by the Gas Chromatograph Mass Spectrometer (GCMS) [1]. Here we show evidence of acetylene (C2H2) on the surface of Titan by detecting absorption bands at 1.55 µm and 4.93 µm using Cassini Visual and Infrared Mapping Spectrometer (VIMS) [4] at equatorial areas of eastern Shangri-La, and Fensal-Aztlan/Quivira.An anti-correlation of absorption band strength with albedo indicates greater concentrations of C2H2 in the dark terrains, such as sand dunes and near the Huygens landing site. The specific location of the C2H2 detections suggests that C2H2 is mobilized by surface processes, such as surface weathering by liquids through dissolution/evaporation processes.References:[1]Niemann et al., Nature 438, 779-784 (2005).[2]Lavvas et al., Planetary and Space Science 56, 67 - 99 (2008).[3]Lavvas et al., Planetary and Space Science 56, 27 - 66 (2008).[4] Brown et al., The Cassini-Huygens Mission 111-168 (Springer, 2004).

  9. Crystallinity and electrical properties of neodymium-substituted bismuth titanate thin films

    International Nuclear Information System (INIS)

    Chen, Y.-C.; Hsiung, C.-P.; Chen, C.-Y.; Gan, J.-Y.; Sun, Y.-M.; Lin, C.-P.

    2006-01-01

    We report on the properties of Nd-substituted bismuth titanate Bi 4-x Nd x Ti 3 O 12 (BNdT) thin films for ferroelectric non-volatile memory applications. The Nd-substituted bismuth titanate thin films fabricated by modified chemical solution deposition technique showed much improved properties compared to pure bismuth titanate. A pyrochlore free crystalline phase was obtained at a low annealing temperature of 640 deg. C and grain size was found to be considerably increased as the annealing temperature increased. The film properties were found to be strongly dependent on the Nd content and annealing temperatures. The measured dielectric constant of BNdT thin films was in the range 172-130 for Bi 4-x Nd x Ti 3 O 12 with x 0.0-0.75. Ferroelectric properties of Nd-substituted bismuth titanate thin films were significantly improved compared to pure bismuth titanate. For example, the observed 2P r and E c for Bi 3.25 Nd 0.75 Ti 3 O 12 , annealed at 680 deg. C, were 38 μC/cm 2 and 98 kV/cm, respectively. The improved microstructural and ferroelectric properties of BNdT thin films suggest their suitability for high density ferroelectric random access memory applications

  10. Quantum Chemical Study of Water Adsorption on the Surfaces of SrTiO3 Nanotubes.

    Science.gov (United States)

    Bandura, Andrei V; Kuruch, Dmitry D; Evarestov, Robert A

    2015-07-20

    We have studied the adsorption of water molecules on the inner and outer surfaces of nanotubes generated by rolling (001) layers of SrTiO3 cubic crystals. The stability and the atomic and electronic structures of the adsorbed layers are determined by using hybrid density functional theory. The absorption energy and the preferred adsorbate structure are essentially governed by the nature of the surface of the nanotube. Dissociative adsorption prevails on the outer nanotube surfaces. The stability of the adsorbed layers on the inner surfaces is related to the possibility of the formation of hydrogen bonds between water molecules and surface oxygen atoms, and depends on the surface curvature. The presence of water molecules on the inner surface of the nanotubes leads to an increase of the electronic band gap. Externally TiO2 -terminated nanotubes could be used for the photocatalytic decomposition of water by ultraviolet radiation. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Ocular Toxicity Profile of ST-162 and ST-168 as Novel Bifunctional MEK/PI3K Inhibitors.

    Science.gov (United States)

    Smith, Andrew; Pawar, Mercy; Van Dort, Marcian E; Galbán, Stefanie; Welton, Amanda R; Thurber, Greg M; Ross, Brian D; Besirli, Cagri G

    2018-04-30

    ST-162 and ST-168 are small-molecule bifunctional inhibitors of MEK and PI3K signaling pathways that are being developed as novel antitumor agents. Previous small-molecule and biologic MEK inhibitors demonstrated ocular toxicity events that were dose limiting in clinical studies. We evaluated in vitro and in vivo ocular toxicity profiles of ST-162 and ST-168. Photoreceptor cell line 661W and adult retinal pigment epithelium cell line ARPE-19 were treated with increasing concentrations of bifunctional inhibitors. Western blots, cell viability, and caspase activity assays were performed to evaluate MEK and PI3K inhibition and dose-dependent in vitro toxicity, and compared with monotherapy. In vivo toxicity profile was assessed by intravitreal injection of ST-162 and ST-168 in Dutch-Belted rabbits, followed by ocular examination and histological analysis of enucleated eyes. Retinal cell lines treated with ST-162 or ST-168 exhibited dose-dependent inhibition of MEK and PI3K signaling. Compared with inhibition by monotherapies and their combinations, bifunctional inhibitors demonstrated reduced cell death and caspase activity. In vivo, both bifunctional inhibitors exhibited a more favorable toxicity profile when compared with MEK inhibitor PD0325901. Novel MEK and PI3K bifunctional inhibitors ST-162 and ST-168 demonstrate favorable in vitro and in vivo ocular toxicity profiles, supporting their further development as potential therapeutic agents targeting multiple aggressive tumors.

  12. Synthesis of BaTiO{sub 3} and SrTiO{sub 3} by microwave assisted hydrothermal method (MAH) using anatase as titanium precursor

    Energy Technology Data Exchange (ETDEWEB)

    Magalhães, Renata da Silva; Macedo Junior, Wagner Dias; Souza, Agda Eunice de; Teixeira, Silvio Rainho, E-mail: R.S.Magalhaes@hotmail.com [Universidade Estadual Paulista Julio de Mesquita Filho (FCT/UNESP), Presidente Prudente, SP (Brazil); Li, Maximo Siu [Universidade de Sao Paulo (USP), São Carlos, SP (Brazil). Instituto de Física; Longo, Elson [Universidade Estadual Paulista Julio de Mesquita Filho (UNESP), Araraquara, SP (Brazil). Instituto de Química

    2016-07-01

    Full text: Strontium and barium titanates (SrTiO{sub 3} (ST) and BaTiO{sub 3} (BT)) in their crystalline form belong to the perovskite (ABO{sub 3}) class. Both display a semiconductor behavior with many interesting properties. The method of synthesis employed and different precursors may influence the morphology and properties of ceramic materials [1,2]. Barium (BT) and strontium (St) titanates were produced using the Microwave Assisted Hydrothermal Method (MAH), different concentrations (1,3 and 6 molL{sup -1}) of mineralizer (KOH) and a different titanium precursor: a complex anatase-hydrogen peroxide. Barium and strontium chloride were used as the other metal precursors. The resulting material were characterized by different techniques such as: X-ray diffraction (XRD), Micro-Raman Spectroscopy (MR), UV-Vis, Scanning Electron microscopy (SEM) and finally their photoluminescent emissions (FL) were recorded at room temperature. The results show that there were differences in crystallinity, morphology, number of formed phases and photoluminescent emission, among the titanate produced with different concentrations of mineralizer. References: [1] A.E. Souza et al., Order–disorder degree of self-assembled clusters: Influence on photoluminescence emission and morphology of Ba{sub x}Sr{sub 1-x}TiO{sub 3} nanocrystals, Chemical Physics Letters 514 (2011) 301–306. [2] T. M. Mazzo et al., Influence of titanium precursor on photoluminescent emission of micro-cube-shaped CaTiO{sub 3}, Journal of Luminescence 165 (2015). (author)

  13. Above room-temperature ferromagnetism in La1-xCaxMnO3 epitaxial thin films on SrTiO3(001) substrates

    Science.gov (United States)

    Kou, Yunfang; Wang, Hui; Miao, Tian; Wang, Yanmei; Xie, Lin; Wang, Shasha; Liu, Hao; Lin, Hanxuan; Zhu, Yinyan; Wang, Wenbin; Du, Haifeng; Pan, Xiaoqing; Wu, Ruqian; Yin, Lifeng; Shen, Jian

    The colossal magnetoresistive (CMR) manganites are popular materials for spintronics applications due to their high spin polarization. Only a couple of manganites like La1-xSrxMnO3 have a Curie temperature (Tc) that is higher than room temperature. Finding methods to raise the Tc of manganites over room temperature is useful but challenging. In this work, we use the most intensively studied La1-xCaxMnO3 (LCMO) as the prototype system to demonstrate that Tc can be greatly enhanced by carefully tuning the electronic structure using doping and strain. Specifically, we grow LCMO films on SrTiO3 (001) substrates using pulsed laser deposition. Magnetic and transport measurements indicate a great enhancement of Tc over room temperature at x =0.2 doping. Theoretical calculations indicate that the combined effects from doping and strain give rise to a new electronic structure favoring ferromagnetism in LCMO system. Furthermore, using the La0.8Ca0.2MnO3 as ferromagnetic electrodes, we achieve finite tunneling magnetoresistance (TMR) above room temperature.

  14. Synthesis and structural characterization of Ce-doped bismuth titanate

    International Nuclear Information System (INIS)

    Pavlovic, Nikolina; Srdic, Vladimir V.

    2009-01-01

    Ce-modified bismuth titanate nanopowders Bi 4-x Ce x Ti 3 O 12 (x ≤ 1) have been synthesized using a coprecipitation method. DTA/TG, FTIR, XRD, SEM/EDS and BET methods were used in order to investigate the effect of Ce-substitution on the structure, morphology and sinterability of the obtained powders. The phase structure investigation revealed that after calcinations at 600 deg. C powder without Ce addition exhibited pure bismuth titanate phase; however, powders with Ce (x = 0.25, 0.5 and 0.75) had bismuth titanate pyrochlore phase as the second phase. The strongest effect of Ce addition on the structure was noted for the powder with the highest amount of Ce (x = 1) having a cubic pyrochlore structure. The presence of pure pyrochlore phase was explained by its stabilization due to the incorporation of cerium ions in titanate structure. Ce-modified bismuth titanate ceramic had a density over 95% of theoretical density and the fracture in transgranular manner most probably due to preferable distribution of Ce in boundary region

  15. Titan Orbiter Aerorover Mission

    Science.gov (United States)

    Sittler Jr., E. C.; Acuna, M.; Burchell, M. J.; Coates, A.; Farrell, W.; Flasar, M.; Goldstein, B. E.; Gorevan, S.; Hartle, R. E.; Johnson, W. T. K.

    2001-01-01

    We propose a combined Titan orbiter and Titan Aerorover mission with an emphasis on both in situ and remote sensing measurements of Titan's surface, atmosphere, ionosphere, and magnetospheric interaction. The biological aspect of the Titan environment will be emphasized by the mission (i.e., search for organic materials which may include simple organics to 'amono' analogues of amino acids and possibly more complex, lightening detection and infrared, ultraviolet, and charged particle interactions with Titan's surface and atmosphere). An international mission is assumed to control costs. NASA will provide the orbiter, launch vehicle, DSN coverage and operations, while international partners will provide the Aerorover and up to 30% of the cost for the scientific instruments through collaborative efforts. To further reduce costs we propose a single PI for orbiter science instruments and a single PI for Aerorover science instruments. This approach will provide single command/data and power interface between spacecraft and orbiter instruments that will have redundant central DPU and power converter for their instruments. A similar approach could be used for the Aerorover. The mission profile will be constructed to minimize conflicts between Aerorover science, orbiter radar science, orbiter radio science, orbiter imaging science, and orbiter fields and particles (FP) science. Additional information is contained in the original extended abstract.

  16. Raman and fluorescence contributions to the resonant inelastic soft x-ray scattering on LaAlO3/SrTiO3 heterostructures

    Science.gov (United States)

    Pfaff, F.; Fujiwara, H.; Berner, G.; Yamasaki, A.; Niwa, H.; Kiuchi, H.; Gloskovskii, A.; Drube, W.; Gabel, J.; Kirilmaz, O.; Sekiyama, A.; Miyawaki, J.; Harada, Y.; Suga, S.; Sing, M.; Claessen, R.

    2018-01-01

    We present a detailed study of the Ti 3 d carriers at the interface of LaAlO3/SrTiO3 heterostructures by high-resolution resonant inelastic soft x-ray scattering (RIXS), with special focus on the roles of overlayer thickness and oxygen vacancies. Our measurements show the existence of interfacial Ti 3 d electrons already below the critical thickness for conductivity. The (total) interface charge carrier density increases up to a LaAlO3 overlayer thickness of 6 unit cells before it levels out. Furthermore, we observe strong Ti 3 d charge carrier doping by oxygen vacancies. The RIXS data combined with photoelectron spectroscopy and transport measurements indicate the simultaneous presence of localized and itinerant charge carriers. At variance with previous interpretations, we show that in our excitation energy dependent RIXS measurements the amounts of localized and itinerant Ti 3 d electrons in the ground state do not scale with the intensities of the Raman and fluorescence peaks, respectively. Rather, we attribute the observation of either Raman components or fluorescence signal to the specific nature of the intermediate state reached in the RIXS excitation process.

  17. Epitaxial growth and dielectric properties of Bi sub 2 VO sub 5 sub . sub 5 thin films on TiN/Si substrates with SrTiO sub 3 buffer layers

    CERN Document Server

    Lee, H Y; Choi, B C; Jeong, J H; Joseph, M; Tabata, H; Kawai, T

    2000-01-01

    Bi sub 2 VO sub 5 sub . sub 5 (BVO) thin films were epitaxially grown on SrTiO sub 3 /TiN/Si substrates by using pulsed laser ablation. A TiN thin film was prepared at 700 .deg. C as a bottom electrode. The TiN film exhibited a high alpha axis orientation and a very smooth morphology. Before the preparation of the BVO thin film, a crystallized SrTiO sub 3 thin film was deposited as a buffer layer on TiN/Si. The BVO thin film grown at a substrate temperature at 700 .deg. C and an oxygen pressure of 50 mTorr was found to be epitaxial along the c-axis. Also, BVO films were observed to have flat surfaces and the step-flow modes. The dielectric constant of the BVO film on STO/TiN/Si was constant at about 8 approx 4 in the applied frequency range between 10 sup 2 and 10 sup 6 Hz.

  18. Titan AVIATR - Aerial Vehicle for In Situ and Airborne Titan Reconnaissance

    Science.gov (United States)

    Kattenhorn, Simon A.; Barnes, J. W.; McKay, C. P.; Lemke, L.; Beyer, R. A.; Radebaugh, J.; Adamkovics, M.; Atkinson, D. H.; Burr, D. M.; Colaprete, T.; Foch, R.; Le Mouélic, S.; Merrison, J.; Mitchell, J.; Rodriguez, S.; Schaller, E.

    2010-10-01

    Titan AVIATR - Aerial Vehicle for In Situ and Airborne Titan Reconnaissance - is a small (120 kg), nuclear-powered Titan airplane in the Discovery/New Frontiers class based on the concept of Lemke (2008 IPPW). The scientific goals of the mission are designed around the unique flexibility offered by an airborne platform: to explore Titan's diversity of surface landforms, processes, and compositions, as well as to study and measure the atmospheric circulation, aerosols, and humidity. AVIATR would address and surpass many of the science goals of hot-air balloons in Titan flagship studies. The strawman instrument payload is narrowly focused on the stated scientific objectives. The optical remote sensing suite comprises three instruments - an off-nadir high-resolution 2-micron camera, a horizon-looking 5-micron imager, and a 1-6 micron pushbroom near-infrared spectrometer. The in situ instruments include atmospheric structure, a methane humidity sensor, and a raindrop detector. An airplane has operational advantages over a balloon. Its piloted nature allows a go-to capability to image locations of interest in real time, thereby allowing for directed exploration of many features of primary geologic interest: Titan's sand dunes, mountains, craters, channels, and lakes. Subsequent imaging can capture changes in these features during the primary mission. AVIATR can fly predesigned routes, building up large context mosaics of areas of interest before swooping down to low altitude to acquire high-resolution images at 30-cm spatial sampling, similar to that of HiRISE at Mars. The elevation flexibility of the airplane allows us to acquire atmospheric profiles as a function of altitude at any desired location. Although limited by the direct-to-Earth downlink bandwidth, the total scientific data return from AVIATR will be >40 times that returned from Huygens. To maximize the science per bit, novel data storage and downlink techniques will be employed, including lossy compression

  19. Anion and cation diffusion in barium titanate and strontium titanate; Anionen- und Kationendiffusion in Barium- und Strontiumtitanat

    Energy Technology Data Exchange (ETDEWEB)

    Kessel, Markus Franz

    2012-12-19

    Perovskite oxides show various interesting properties providing several technical applications. In many cases the defect chemistry is the key to understand and influence the material's properties. In this work the defect chemistry of barium titanate and strontium titanate is analysed by anion and cation diffusion experiments and subsequent time-of-flight secondary ion mass spectrometry (ToF-SIMS). The reoxidation equation for barium titanate used in multi-layer ceramic capacitors (MLCCs) is found out by a combination of different isotope exchange experiments and the analysis of the resulting tracer diffusion profiles. It is shown that the incorporation of oxygen from water vapour is faster by orders of magnitude than from molecular oxygen. Chemical analysis shows the samples contain various dopants leading to a complex defect chemistry. Dysprosium is the most important dopant, acting partially as a donor and partially as an acceptor in this effectively acceptor-doped material. TEM and EELS analysis show the inhomogeneous distribution of Dy in a core-shell microstructure. The oxygen partial pressure and temperature dependence of the oxygen tracer diffusion coefficients is analysed and explained by the complex defect chemistry of Dy-doped barium titanate. Additional fast diffusion profiles are attributed to fast diffusion along grain boundaries. In addition to the barium titanate ceramics from an important technical application, oxygen diffusion in cubic, nominally undoped BaTiO{sub 3} single crystals has been studied by means of {sup 18}O{sub 2}/{sup 16}O{sub 2} isotope exchange annealing and subsequent determination of the isotope profiles in the solid by ToF-SIMS. It is shown that a correct description of the diffusion profiles requires the analysis of the diffusion through the surface space-charge into the material's bulk. Surface exchange coefficients, space-charge potentials and bulk diffusion coefficients are analysed as a function of oxygen partial

  20. Barium titanate thick films prepared by screen printing technique

    Directory of Open Access Journals (Sweden)

    Mirjana M. Vijatović

    2010-06-01

    Full Text Available The barium titanate (BaTiO3 thick films were prepared by screen printing technique using powders obtained by soft chemical route, modified Pechini process. Three different barium titanate powders were prepared: i pure, ii doped with lanthanum and iii doped with antimony. Pastes for screen printing were prepared using previously obtained powders. The thick films were deposited onto Al2O3 substrates and fired at 850°C together with electrode material (silver/palladium in the moving belt furnace in the air atmosphere. Measurements of thickness and roughness of barium titanate thick films were performed. The electrical properties of thick films such as dielectric constant, dielectric losses, Curie temperature, hysteresis loop were reported. The influence of different factors on electrical properties values was analyzed.

  1. Titan's greenhouse and antigreenhouse effects

    Science.gov (United States)

    Mckay, Christopher P.; Pollack, James B.; Courtin, Regis

    1992-01-01

    Thermal mechanisms active in Titan's atmosphere are discussed in a brief review of data obtained during the Voyager I flyby in 1980. Particular attention is given to the greenhouse effect (GHE) produced by atmospheric H2, N2, and CH4; this GHE is stronger than that on earth, with CH4 and H2 playing roles similar to those of H2O and CO2 on earth. Also active on Titan is an antigreenhouse effect, in which dark-brown and orange organic aerosols block incoming solar light while allowing IR radiation from the Titan surface to escape. The combination of GHE and anti-GHE leads to a surface temperature about 12 C higher than it would be if Titan had no atmosphere.

  2. Titan: a laboratory for prebiological organic chemistry

    Science.gov (United States)

    Sagan, C.; Thompson, W. R.; Khare, B. N.

    1992-01-01

    When we examine the atmospheres of the Jovian planets (Jupiter, Saturn, Uranus, and Neptune), the satellites in the outer solar system, comets, and even--through microwave and infrared spectroscopy--the cold dilute gas and grains between the stars, we find a rich organic chemistry, presumably abiological, not only in most of the solar system but throughout the Milky Way galaxy. In part because the composition and surface pressure of the Earth's atmosphere 4 x 10(9) years ago are unknown, laboratory experiments on prebiological organic chemistry are at best suggestive; but we can test our understanding by looking more closely at the observed extraterrestrial organic chemistry. The present Account is restricted to atmospheric organic chemistry, primarily on the large moon of Saturn. Titan is a test of our understanding of the organic chemistry of planetary atmospheres. Its atmospheric bulk composition (N2/CH4) is intermediate between the highly reducing (H2/He/CH4/NH3/H2O) atmospheres of the Jovian planets and the more oxidized (N2/CO2/H2O) atmospheres of the terrestrial planets Mars and Venus. It has long been recognized that Titan's organic chemistry may have some relevance to the events that led to the origin of life on Earth. But with Titan surface temperatures approximately equal to 94 K and pressures approximately equal to 1.6 bar, the oceans of the early Earth have no ready analogue on Titan. Nevertheless, tectonic events in the water ice-rich interior or impact melting and slow re-freezing may lead to an episodic availability of liquid water. Indeed, the latter process is the equivalent of a approximately 10(3)-year-duration shallow aqueous sea over the entire surface of Titan.

  3. Epitaxial Pb(Mg1/3Nb2/3)O3 thin films synthesized by metal-organic chemical vapor deposition

    International Nuclear Information System (INIS)

    Bai, G. R.; Streiffer, S. K.; Baumann, P. K.; Auciello, O.; Ghosh, K.; Stemmer, S.; Munkholm, A.; Thompson, Carol; Rao, R. A.; Eom, C. B.

    2000-01-01

    Metal-organic chemical vapor deposition was used to prepare Pb(Mg 1/3 Nb 2/3 )O 3 (PMN) thin films on (001) SrTiO 3 and SrRuO 3 /SrTiO 3 substrates, using solid Mg β-diketonate as the Mg precursor. Parameters including the precursor ratio in the vapor phase, growth temperature, growth rate, and reaction pressure in the reactor chamber were varied in order to determine suitable growth conditions for producing phase-pure, epitaxial PMN films. A cube-on-cube orientation relationship between the thin film and the SrTiO 3 substrate was found, with a (001) rocking curve width of 0.1 degree sign , and in-plane rocking-curve width of 0.8 degree sign . The root-mean-square surface roughness of a 200-nm-thick film on SrTiO 3 was 2 to 3 nm as measured by scanning probe microscopy. The zero-bias dielectric constant and loss measured at room temperature and 10 kHz for a 200-nm-thick film on SrRuO 3 /SrTiO 3 were approximately 1100 and 2%, respectively. The remnant polarization for this film was 16 μC/cm 2 . (c) 2000 American Institute of Physics

  4. Titan Orbiter with Aerorover Mission (TOAM)

    Science.gov (United States)

    Sittler, Edward C.; Cooper, J. F.; Mahaffey, P.; Esper, J.; Fairbrother, D.; Farley, R.; Pitman, J.; Kojiro, D. R.; TOAM Team

    2006-12-01

    We propose to develop a new mission to Titan called Titan Orbiter with Aerorover Mission (TOAM). This mission is motivated by the recent discoveries of Titan, its atmosphere and its surface by the Huygens Probe, and a combination of in situ, remote sensing and radar mapping measurements of Titan by the Cassini orbiter. Titan is a body for which Astrobiology (i.e., prebiotic chemistry) will be the primary science goal of any future missions to it. TOAM is planned to use an orbiter and balloon technology (i.e., aerorover). Aerobraking will be used to put payload into orbit around Titan. The Aerorover will probably use a hot air balloon concept using the waste heat from the MMRTG 500 watts. Orbiter support for the Aerorover is unique to our approach for Titan. Our strategy to use an orbiter is contrary to some studies using just a single probe with balloon. Autonomous operation and navigation of the Aerorover around Titan will be required, which will include descent near to the surface to collect surface samples for analysis (i.e., touch and go technique). The orbiter can provide both relay station and GPS roles for the Aerorover. The Aerorover will have all the instruments needed to sample Titan’s atmosphere, surface, possible methane lakes-rivers, use multi-spectral imagers for surface reconnaissance; to take close up surface images; take core samples and deploy seismometers during landing phase. Both active and passive broadband remote sensing techniques will be used for surface topography, winds and composition measurements.

  5. Structural and electrical characterization of ultra-thin SrTiO3 tunnel barriers grown over YBa2Cu3O7 electrodes for the development of high Tc Josephson junctions.

    Science.gov (United States)

    Félix, L Avilés; Sirena, M; Guzmán, L A Agüero; Sutter, J González; Vargas, S Pons; Steren, L B; Bernard, R; Trastoy, J; Villegas, J E; Briático, J; Bergeal, N; Lesueur, J; Faini, G

    2012-12-14

    The transport properties of ultra-thin SrTiO(3) (STO) layers grown over YBa(2)Cu(3)O(7) electrodes were studied by conductive atomic force microscopy at the nano-scale. A very good control of the barrier thickness was achieved during the deposition process. A phenomenological approach was used to obtain critical parameters regarding the structural and electrical properties of the system. The STO layers present an energy barrier of 0.9 eV and an attenuation length of 0.23 nm, indicating very good insulating properties for the development of high-quality Josephson junctions.

  6. Structural and electrical characterization of ultra-thin SrTiO3 tunnel barriers grown over YBa2Cu3O7 electrodes for the development of high Tc Josephson junctions

    International Nuclear Information System (INIS)

    Avilés Félix, L; Sirena, M; Agüero Guzmán, L A; González Sutter, J; Pons Vargas, S; Steren, L B; Bernard, R; Trastoy, J; Villegas, J E; Briático, J; Bergeal, N; Lesueur, J; Faini, G

    2012-01-01

    The transport properties of ultra-thin SrTiO 3 (STO) layers grown over YBa 2 Cu 3 O 7 electrodes were studied by conductive atomic force microscopy at the nano-scale. A very good control of the barrier thickness was achieved during the deposition process. A phenomenological approach was used to obtain critical parameters regarding the structural and electrical properties of the system. The STO layers present an energy barrier of 0.9 eV and an attenuation length of 0.23 nm, indicating very good insulating properties for the development of high-quality Josephson junctions. (paper)

  7. GeoTIFF of 3x3 m Bathymetry for St. Thomas & St. John, 2011, UTM 20N NAD83 (NCEI Accession 0131858)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This image represents a LiDAR (Light Detection & Ranging) 3x3 meter resolution bathymetric surface for an area of shallow seabed surrounding St. Thomas and St....

  8. Rectifying characteristics and magnetoresistance in La0.9Sr0.1MnO3/Nb-doped SrTiO3 heterojunctions

    International Nuclear Information System (INIS)

    Luo, Z.; Gao, J.

    2007-01-01

    Manganite-based heterojunctions have attracted lots of attention as one of the most promising practical applications of colossal magnetoresistance materials. In this work, heterojunctions were fabricated by depositing La 0.9 Sr 0.1 MnO 3 (LSMO) films on substrates of 0.7 wt.% Nb-doped SrTiO 3 using pulsed laser deposition technique. X-ray diffraction spectra confirmed that the grown films are of single phase and have an orientation with the c-axis perpendicular to the substrate surface. As temperature decreases, the resistivity of LSMO films first increases gradually and then increases abruptly at temperature lower than 150 K. These junctions showed clear rectifying characteristics and strong temperature dependent current-voltage relation. Diffusion voltage decreases as temperature increases. Under forward bias, current is proportion to exp(eV/nkT). Ideal factor increases quickly and tunneling current plays more and more important role as temperature decreases. At 50 K, tunneling current becomes nearly dominant. Large magnetoresistance was observed. The sign and value of such magnetoresistance depends on the direction and value of current

  9. Strontium Titanate-based Composite Anodes for Solid Oxide Fuel Cells

    DEFF Research Database (Denmark)

    Blennow Tullmar, Peter; Kammer Hansen, Kent; Wallenberg, L.R.

    2008-01-01

    Surfactant-assisted infiltration of Gd-doped ceria (CGO) in Nb-doped SrTiO3 (STN) was investigated as a potential fuel electrode for solid oxide fuel cells (SOFC). An electronically conductive backbone structure of STN was first fabricated at high temperatures and then combined with the mixed con...

  10. Cosmic-rays induced Titan tholins and their astrobiological significances

    Science.gov (United States)

    Kobayashi, Kensei; Taniuchi, Toshinori; Hosogai, Tomohiro; Kaneko, Takeo; Takano, Yoshinori; Khare, Bishun; McKay, Chris

    Titan is the largest satellite of Saturn. It is quite unique satellite since it has a dense atmosphere composed of nitrogen and methane, and has been sometimes considered as a model of primitive Earth. In Titan atmosphere, a wide variety of organic compounds and mists made of complex organics. Such solid complex organics are often referred to as tholins. A number of laboratory experiments simulating reactions in Titan atmosphere have been conducted. In most of them, ultraviolet light and discharges (simulating actions of electrons in Saturn magnetosphere) were used, which were simulation of the reactions in upper dilute atmosphere of Titan. We examined possible formation of organic compounds in the lower dense atmosphere of Titan, where cosmic rays are major energies. A Mixture of 35 Torr of methane and 665 Torr of nitrogen was irradiated with high-energy protons (3 MeV) from a van de Graaff accelerator (TIT, Japan) or from a Tandem accelerator (TIARA, QUBS, JAEA, Japan). In some experiments, 13 C-labelled methane was used. We also performed plasma discharges in a mixture of methane (10 %) and nitrogen (90 %) to simulate the reactions in the upper atmosphere of Titan. Solid products by proton irradiation and those by plasma discharges are hereafter referred to as PI-tholins and PD-tholins, respectively. The resulting PI-tholins were observed with SEM and AFM. They were characterized by pyrolysis-GC/MS, gel permeation chromatography, FT-IR, etc. Amino acids in PI-and PD-tholins were analyzed by HPLC, GC/MS and MALDI-TOF-MS after acid hydrolysis. 18 O-Labelled water was used in some cases during hydrolysis. Filamentary and/or globular-like structures were observed by SEM and AFM. By pyrolysis-GC/MS of PI-tholins, ammonia and hydrogen cyanide were detected, which was the same as the results obtained in Titan atmosphere during the Huygens mission. A wide variety of amino acids were detected after hydrolysis of both tholins. It was proved that oxygen atoms in the amino

  11. Organic chemistry on Titan: Surface interactions

    Science.gov (United States)

    Thompson, W. Reid; Sagan, Carl

    1992-01-01

    The interaction of Titan's organic sediments with the surface (solubility in nonpolar fluids) is discussed. How Titan's sediments can be exposed to an aqueous medium for short, but perhaps significant, periods of time is also discussed. Interactions with hydrocarbons and with volcanic magmas are considered. The alteration of Titan's organic sediments over geologic time by the impacts of meteorites and comets is discussed.

  12. TSSM: The in situ exploration of Titan

    Science.gov (United States)

    Coustenis, A.; Lunine, J. I.; Lebreton, J. P.; Matson, D.; Reh, K.; Beauchamp, P.; Erd, C.

    2008-09-01

    The Titan Saturn System Mission (TSSM) mission was born when NASA and ESA decided to collaborate on two missions independently selected by each agency: the Titan and Enceladus mission (TandEM), and Titan Explorer, a 2007 Flagship study. TandEM, the Titan and Enceladus mission, was proposed as an L-class (large) mission in response to ESA's Cosmic Vision 2015-2025 Call. The mission concept is to perform remote and in situ investigations of Titan primarily, but also of Enceladus and Saturn's magentosphere. The two satellites are tied together by location and properties, whose remarkable natures have been partly revealed by the ongoing Cassini-Huygens mission. These bodies still hold mysteries requiring a complete exploration using a variety of vehicles and instruments. TSSM will study Titan as a system, including its upper atmosphere, the interactions with the magnetosphere, the neutral atmosphere, surface, interior, origin and evolution, as well as the astrobiological potential of Titan. It is an ambitious mission because its targets are two of the most exciting and challenging bodies in the Solar System. It is designed to build on but exceed the scientific and technological accomplishments of the Cassini- Huygens mission, exploring Titan and Enceladus in ways that are not currently possible (full close-up and in situ coverage over long periods of time for Titan, several close flybys of Enceladus). One overarching goal of the TSSM mission is to explore in situ the atmosphere and surface of Titan. In the current mission architecture, TSSM consists of an orbiter (under NASA's responsibility) with a large host of instruments which would perform several Enceladus and Titan flybys before stabilizing in an orbit around Titan alone, therein delivering in situ elements (a Montgolfière, or hot air balloon, and a probe/lander). The latter are being studied by ESA. The balloon will circumnavigate Titan above the equator at an altitude of about 10 km for several months. The

  13. ALMA Spectroscopy of Titan's Atmosphere: First Detections of Vinyl Cyanide and Acetonitrile Isotopologues

    Science.gov (United States)

    Cordiner, Martin; Y Palmer, Maureen; Nixon, Conor A.; Charnley, Steven B.; Mumma, Michael J.; Irwin, Pat G. J.; Teanby, Nick A.; Kisiel, Zbigniew; Serigano, Joseph

    2015-11-01

    Studies of Titan's atmospheric chemistry provide a unique opportunity to explore the origin and evolution of complex organic matter in primitive planetary atmospheres. The Atacama Large Millimeter/submillimeter Array (ALMA) is a powerful new telescope, well suited to the study of molecular emission from Titan's stratosphere and mesosphere. Here we present early results from our ongoing study to exploit the large volume of Titan data taken using ALMA in Early Science Mode (during the period 2012-2014). Combining data from multiple ALMA Band 6 observations, we obtained high-resolution mm-wave spectra with unprecedented sensitivity, enabling the first detection of vinyl cyanide (C2H3CN) in Titan's atmosphere. Initial estimates indicate a mesospheric abundance ratio with respect to ethyl cyanide (C2H5CN) of [C2H3CN]/[C2H5CN] = 0.31. In addition, we report the first detections on Titan of the 13C and 15N-substituted isotopologues of acetonitrile (13CH3CN and CH3C15N). Radiative transfer models and possible chemical formation pathways for these molecules will be discussed.

  14. Fracture force analysis at the interface of Pd and SrTiO3

    International Nuclear Information System (INIS)

    Nazarpour, S.; Zamani, C.; Cirera, A.

    2009-01-01

    The objective of this work is to develop an experimental indentation based method to determine the fracture force at the interface of Pd thin films and SrTiO 3 perovskite substrate. This paper reports on the results obtained for indentation into Pd thin films which were deposited in various thicknesses from 20 nm to 200 nm under vacuum and 300 deg. C substrate temperature by an electron beam physical vapor deposition. Initially, the relation between grain size, elastic module and hardness was considered as a function of film thickness. Thereafter, in developing new method, oscillating indentation was performed with different applied forces and oscillating times in order to measure the critical fracture force in each thickness. The effect of oscillating time on plastically deformed regions surrounding an indentation was schematically explained in conjunction with variation of oscillating time to determine the interfacial properties of the Pd thin film. Furthermore, the accuracy of the critical fracture force was ensured by applied force versus piling up height plot. The method is validated experimentally for the soft thin films over the hard substrate. However, further study would be essential to measure the film adhesion by means of fracture force at the interface

  15. Nanoscale leakage current measurements in metal organic chemical vapor deposition crystalline SrTiO3 films

    International Nuclear Information System (INIS)

    Rozier, Y.; Gautier, B.; Hyvert, G.; Descamps, A.; Plossu, C.; Dubourdieu, C.; Ducroquet, F.

    2009-01-01

    The properties of SrTiO 3 thin films, grown by liquid injection metal organic chemical vapor deposition on Si/SiO 2 , using a mixture of precursors, have been investigated at the nanoscale using an Atomic Force Microscope in the so-called Conductive Atomic Force Microscopy mode. Maps of the leakage currents with a nanometric resolution have been obtained on films elaborated at different temperatures and stoichiometries in order to discriminate the role of each parameter on the onset of leakage currents in the resulting layers. It appears that the higher the deposition temperature, the higher the leakage currents of the films. The mapping with a nanometric precision allows to show a heterogeneous behaviour of the surface with leaky grains and insulating boundaries. The study of films elaborated at the same temperature with different compositions supports the assumption that the leakage currents on Ti-rich layers are far higher than on Sr-rich layers

  16. Synthesis and sorption properties of new synthesized rare-earth-doped sodium titanate

    International Nuclear Information System (INIS)

    Ali, I.M.

    2010-01-01

    A series of rare-earth-doped sodium titanates with the chemical formula R x H y Na 4-(x+y) TiO 4 ·nH 2 O (where R = Ce 3+ , Nd 3+ and Sm 3+ ) were grown employing solid-state fusion reaction technique. The physico-chemical investigations indicated that the new materials were self engineered into large particles enough to be used in sorption process and having crystalline structures containing localized Na + ions. Equilibrium studies revealed that an enhancement in sorption efficiency of sodium titanate after rare-earth doping. The neodymium-rich sodium titanate exhibited a better exchange affinity for Cs + compared to the other studied series. Data on the kinetics of cesium exchange fit well to pseudo-second order and intra-particle diffusion models. In a separate experiment, it was reported that the R-HNaTi series showed responsible sorption affinity toward Ce, Nd and Sm ions in their solution mixture with insignificant selectivity trend which reflects the high stability of titanate matrices. (author)

  17. Orientation Control of Interfacial Magnetism at La0.67Sr0.33MnO3/SrTiO3 Interfaces.

    Science.gov (United States)

    Guo, Er-Jia; Charlton, Timothy; Ambaye, Haile; Desautels, Ryan D; Lee, Ho Nyung; Fitzsimmons, Michael R

    2017-06-07

    Understanding the magnetism at the interface between a ferromagnet and an insulator is essential because the commonly posited magnetic "dead" layer close to an interface can be problematic in magnetic tunnel junctions. Previously, degradation of the magnetic interface was attributed to charge discontinuity across the interface. Here, the interfacial magnetism was investigated using three identically prepared La 0.67 Sr 0.33 MnO 3 (LSMO) thin films grown on different oriented SrTiO 3 (STO) substrates by polarized neutron reflectometry. In all cases the magnetization at the LSMO/STO interface is larger than the film bulk. We show that the interfacial magnetization is largest across the LSMO/STO interfaces with (001) and (111) orientations, which have the largest net charge discontinuities across the interfaces. In contrast, the magnetization of LSMO/STO across the (110) interface, the orientation with no net charge discontinuity, is the smallest of the three orientations. We show that a magnetically degraded interface is not intrinsic to LSMO/STO heterostructures. The approach to use different crystallographic orientations provides a means to investigate the influence of charge discontinuity on the interfacial magnetization.

  18. Amino acidis derived from Titan tholins

    Science.gov (United States)

    Khare, Bishun N.; Sagan, Carl; Ogino, Hiroshi; Nagy, Bartholomew; Er, Cevat

    1986-01-01

    The production of amino acids by acid treatment of Titan tholin is experimentally investigated. The synthesis of Titan tholin and the derivatization of amino acids to N-trifluoroacetyl isopropyl esters are described. The gas chromatography/mass spectroscopy analysis of the Titan tholins reveals the presence of glycine, alpha and beta alainine, and aspartic acid, and the total yield of amino acids is about 0.01.

  19. Bismuth titanate nanorods and their visible light photocatalytic properties

    International Nuclear Information System (INIS)

    Pei, L.Z.; Liu, H.D.; Lin, N.; Yu, H.Y.

    2015-01-01

    Highlights: • Bismuth titanate nanorods have been synthesized by a simple hydrothermal process. • The size of bismuth titanate nanorods can be controlled by growth conditions. • Bismuth titanate nanorods show good photocatalytic activities of methylene blue and Rhodamine B. - Abstract: Bismuth titanate nanorods have been prepared using a facile hydrothermal process without additives. The bismuth titanate products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM) and UV-vis diffusion reflectance spectrum. XRD pattern shows that the bismuth titanate nanorods are composed of cubic Bi 2 Ti 2 O 7 phase. Electron microscopy images show that the length and diameter of the bismuth titanate nanorods are 50-200 nm and 2 μm, respectively. Hydrothermal temperature and reaction time play important roles on the formation and size of the bismuth titanate nanorods. UV-vis diffusion reflectance spectrum indicates that bismuth titanate nanorods have a band gap of 2.58 eV. The bismuth titanate nanorods exhibit good photocatalytic activities in the photocatalytic degradation of methylene blue (MB) and Rhodamine B (RB) under visible light irradiation. The bismuth titanate nanorods with cubic Bi 2 Ti 2 O 7 phase are a promising candidate as a visible light photocatalyst

  20. Hubble Observes Surface of Titan

    Science.gov (United States)

    1994-01-01

    Scientists for the first time have made images of the surface of Saturn's giant, haze-shrouded moon, Titan. They mapped light and dark features over the surface of the satellite during nearly a complete 16-day rotation. One prominent bright area they discovered is a surface feature 2,500 miles across, about the size of the continent of Australia.Titan, larger than Mercury and slightly smaller than Mars, is the only body in the solar system, other than Earth, that may have oceans and rainfall on its surface, albeit oceans and rain of ethane-methane rather than water. Scientists suspect that Titan's present environment -- although colder than minus 289 degrees Fahrenheit, so cold that water ice would be as hard as granite -- might be similar to that on Earth billions of years ago, before life began pumping oxygen into the atmosphere.Peter H. Smith of the University of Arizona Lunar and Planetary Laboratory and his team took the images with the Hubble Space Telescope during 14 observing runs between Oct. 4 - 18. Smith announced the team's first results last week at the 26th annual meeting of the American Astronomical Society Division for Planetary Sciences in Bethesda, Md. Co-investigators on the team are Mark Lemmon, a doctoral candidate with the UA Lunar and Planetary Laboratory; John Caldwell of York University, Canada; Larry Sromovsky of the University of Wisconsin; and Michael Allison of the Goddard Institute for Space Studies, New York City.Titan's atmosphere, about four times as dense as Earth's atmosphere, is primarily nitrogen laced with such poisonous substances as methane and ethane. This thick, orange, hydrocarbon haze was impenetrable to cameras aboard the Pioneer and Voyager spacecraft that flew by the Saturn system in the late 1970s and early 1980s. The haze is formed as methane in the atmosphere is destroyed by sunlight. The hydrocarbons produced by this methane destruction form a smog similar to that found over large cities, but is much thicker

  1. Effect of crystal structure on strontium titanate thin films and their dielectric properties

    Science.gov (United States)

    Kampangkeaw, Satreerat

    Strontium titanate (SrTiO3 or STO) has application in radio and microwave-frequency tunable capacitor devices particularly at low temperatures due to its high dielectric constant, low loss and the electric field tunability of its dielectric constant. The main goal of improving the performance in these devices is to increase the tunability and decrease the dielectric loss at the same time, especially at microwave frequencies. Thin films of STO however, show dramatic differences compared to the bulk. The dielectric constant of bulk STO increases nonlinearly from 300 at room temperature to 30000 at 4 K and the loss range is 10-3--10 -4. On the other hand. STO thin films, while showing a dielectric constant close to 300 at room temperature, typically reach a maximum between 1000 and 10000 in the 30 K to 100 K range before decreasing, and the high-loss range is 10-2--10-3. We have grown strontium titanate thin films using a pulsed laser deposition technique on substrates selected to have a small lattice mismatch between the film and substrate. Neodymium gallate (NdGaO3 or NGO) and lanthanum aluminate (LaAlO3 or LAO) substrates were good candidates due to only 1--2% mismatching. Film capacitor devices were fabricated with 25 micron gap separation. 1.5 mm total gap length and an overall 1 x 2 mm dimension using standard lithography and gold metal evaporative techniques. Their nonlinear dielectric constant and loss tangent were measured at low frequencies and also at 2 GHz, and from room temperature down to 4 K. The resulting films show significant variations of dielectric properties with position on the substrates with respect to the deposition plume axis. In the presence of DC electric fields up to +/-4 V/mum, STO films show improved dielectric tunability and low loss in regions far from the plume axis. We found that the films grown on NCO have lower dielectric loss than those on LAO due to a closer match of the NCO lattice to that of STO. We investigated the possible

  2. The safety designs for the TITAN reversed-field pinch reactor study

    International Nuclear Information System (INIS)

    Wong, C.P.C.; Cheng, E.T.; Creedon, R.L.; Hoot, C.G.; Schultz, K.R.; Grotz, S.P.; Blanchard, J.; Sharafat, S.; Najmabadi, F.

    1989-01-01

    TITAN is a study to investigate the potential of the reversed-field pinch concept as a compact, high-power density energy system. Two reactor concepts were developed, a self-cooled lithium design with vanadium structure and an aqueous solution loop-in-pool design, both operating at 18 MW/m 2 . The key safety features of the TITAN-I lithium-vanadium blanket design are in material selection, fusion power core configuration selection, lithium piping connections, and passive lithium drain tank system. Based on these safety features and results from accident evaluation, TITAN-I can at least be rated at a level 3 of safety assurance. For the TITAN-II aqueous loop-in-pool design, the key passive feature is the complete submersion of the fusion power core and the corresponding primary coolant loop system into a pool of low temperature water. Based on this key safety design feature, the TITAN-II design can be rated at a level 2 of safety assurance. (orig.)

  3. The safety designs for the TITAN reversed-field pinch reactor study

    International Nuclear Information System (INIS)

    Wong, C.P.C.; Cheng, E.T.; Creedon, R.L.; Hoot, C.G.; Schultz, K.R.; Grotz, S.P.; Blanchard, J.P.; Sharafat, S.; Najmabadi, F.

    1988-01-01

    TITAN is a study to investigate the potential of the reversed-field pinch concept as a compact, high-power density energy system. Two reactor concepts were developed, a self-cooled lithium design with vanadium structure and an aqueous solution loop-in-pool design, both operating at 18 MW/m 2 . The key safety features of the TITAN-I lithium-vanadium blanket design are in material selection, fusion power core configuration selection, lithium piping connections and passive lithium drain tank system. Based on these safety features and results from accident evaluation, TITAN-I can at least be rated as level 3 of safety assurance. For the TITAN-II aqueous loop-in-pool design, the key passive feature is the complete submersion of the fusion power core and the corresponding primary coolant loop system into a pool of low temperature water. Based on this key safety design feature, the TITAN-II design can be rated as level 2 of safety assurance. 7 refs., 2 figs

  4. UV-laser-light-controlled photoluminescence of metal oxide nanoparticles in different gas atmospheres: BaTiO3, SrTiO3 and HfO2

    International Nuclear Information System (INIS)

    Mochizuki, Shosuke; Saito, Takashi; Yoshida, Kaori

    2012-01-01

    The photoluminescence (PL) enhancement has been studied at room temperature using various specimen atmospheres (O 2 gas, CO 2 gas, CO 2 -H 2 mixture gas, Ar-H 2 mixture gas and vacuum) under 325 nm laser light irradiation on various metal oxides. Of them, the results obtained for BaTiO 3 nanocrystals, SrTiO 3 ones and HfO 2 powder crystal are given in the present paper. Their PL were considerably increased in intensity by irradiation of 325 nm laser light in CO 2 gas and CO 2 -H 2 mixture gas. The cause of the PL intensity enhancements is discussed in the light of the exciton theory, the defect chemistry and the photocatalytic theory. The results may be applied for the utilization of greenhouse gas (CO 2 ) and the optical sensor for CO 2 gas.

  5. The rotation of Titan and Ganymede

    Science.gov (United States)

    Van Hoolst, Tim; Coyette, Alexis; Baland, Rose-Marie; Trinh, Antony

    2016-10-01

    The rotation rates of Titan and Ganymede, the largest satellites of Saturn and Jupiter, are on average equal to their orbital mean motion. Here we discuss small deviations from the average rotation for both satellites and evaluate the polar motion of Titan induced by its surface fluid layers. We examine different causes at various time scales and assess possible consequences and the potential of using librations and polar motion as probes of the interior structure of the satellites.The rotation rate of Titan and Ganymede cannot be constant on the orbital time scale as a result of the gravitational torque of the central planet acting on the satellites. Titan is moreover expected to show significant polar motion and additional variations in the rotation rate due to angular momentum exchange with the atmosphere, mainly at seasonal periods. Observational evidence for deviations from the synchronous state has been reported several times for Titan but is unfortunately inconclusive. The measurements of the rotation variations are based on determinations of the shift in position of Cassini radar images taken during different flybys. The ESA JUICE (JUpiter ICy moons Explorer) mission will measure the rotation variations of Ganymede during its orbital phase around the satellite starting in 2032.We report on different theoretical aspects of the librations and polar motion. We consider the influence of the rheology of the ice shell and take into account Cassini measurements of the external gravitational field and of the topography of Titan and similar Galileo data about Ganymede. We also evaluate the librations and polar motion induced by Titan's hydrocarbon seas and use the most recent results of Titan's atmosphere dynamics. We finally evaluate the potential of rotation variations to constrain the satellite's interior structure, in particular its ice shell and ocean.

  6. Future Exploration of Titan and Enceladus

    Science.gov (United States)

    Matson, D. L.; Coustenis, A.; Lunine, J.; Lebreton, J.; Reh, K.; Beauchamp, P.

    2009-05-01

    The future exploration of Titan and Enceladus has become very important for the planetary community. The study conducted last year of the Titan Saturn System Mission (TSSM) led to an announcement in which ESA and NASA prioritized future OPF missions, stating that TSSM is planned after EJSM (for details see http://www.lpi.usra.edu/opag/). TSSM consists of a TSSM Orbiter that would carry two in situ elements: the Titan Montgolfiere hot air balloon and the Titan Lake Lander. The mission could launch in the 2023-2025 timeframe on a trajectory to arrive ~9 years later for a 4-year mission in the Saturn system. Soon after arrival at Saturn, the montgolfiere would be delivered to Titan to begin its mission of airborne, scientific observations of Titan from an altitude of about 10 km. The montgolfiere would have a Multi-Mission Radioisotope Thermoelectric Generator (MMRTG) power system and would be designed to last at least 6-12 months in Titan's atmosphere. With the predicted winds and weather, that would be sufficient to circumnavigate the globe! On a subsequent fly-by, the TSSM orbiter would release the Lake Lander on a trajectory toward Titan for a targeted entry. It would descend through the atmosphere making scientific measurements, much like Huygens did, and then land and float on one of Titan's seas. This would be its oceanographic phase, making a physical and chemical assessment of the sea. The Lake Lander would operate 8-10 hours until its batteries become depleted. Following the delivery of the in situ elements, the TSSM orbiter would explore the Saturn system via a 2-year tour that includes in situ sampling of Enceladus' plumes as well as Titan flybys. After the Saturn system tour, the TSSM orbiter would enter orbit around Titan for a global survey phase. Synergistic and coordinated observations would be carried out between the TSSM orbiter and the in situ elements. The scientific requirements were developed by the international TSSM Joint Science Definition

  7. Clash of the Titans

    Science.gov (United States)

    Subramaniam, Karthigeyan

    2010-01-01

    WebQuests and the 5E learning cycle are titans of the science classroom. These popular inquiry-based strategies are most often used as separate entities, but the author has discovered that using a combined WebQuest and 5E learning cycle format taps into the inherent power and potential of both strategies. In the lesson, "Clash of the Titans,"…

  8. The Greenhouse and Anti-Greenhouse Effects on Titan

    Science.gov (United States)

    McKay, C. P.; Cuzzi, Jeffrey N. (Technical Monitor)

    1994-01-01

    Titan is the largest moon of Saturn and is the only moon in the solar system with a substantial atmosphere. Its atmosphere is mostly made of nitrogen, with a few percent CH4, 0.1% H2 and an uncertain level of Ar (less than 10%). The surface pressure is 1.5 atms and the surface temperature is 95 K, decreasing to 71 at the tropopause before rising to stratospheric temperatures of 180 K. In pressure and composition Titan's atmosphere is the closest twin to Earth's. The surface of Titan remains unknown, hidden by the thick smog layer, but it may be an ocean of liquid methane and ethane. Titan's atmosphere has a greenhouse effect which is much stronger than the Earth's - 92% of the surface warming is due to greenhouse radiation. However an organic smog layer in the upper atmosphere produces an anti-greenhouse effect that cuts the greenhouse warming in half - removing 35% of the incoming solar radiation. Models suggest that during its formation Titan's atmosphere was heated to high temperatures due to accretional energy. This was followed by a cold Triton-like period which gradually warmed to the present conditions. The coupled greenhouse and haze anti-greenhouse may be relevant to recent suggestions for haze shielding of a CH4 - NH3 early atmosphere on Earth or Mars. When the NASA/ESA mission to the Saturn System, Cassini, launches in a few years it will carry a probe that will be sent to the surface of Titan and show us this world that is strange and yet in many ways similar to our own.

  9. Unexpected metal-insulator transition in thick Ca1-xSrxVO3 film on SrTiO3 (100) single crystal

    Science.gov (United States)

    Takayanagi, Makoto; Tsuchiya, Takashi; Namiki, Wataru; Ueda, Shigenori; Minohara, Makoto; Horiba, Koji; Kumigashira, Hiroshi; Terabe, Kazuya; Higuchi, Tohru

    2018-03-01

    Epitaxial Ca1-xSrxVO3 (0 ≦ x ≦ 1) thin films were grown on (100)-oriented SrTiO3 substrates by using the pulsed laser deposition technique. In contrast to the previous report that metal-insulator transition (MIT) in Ca1-xSrxVO3 (CSVO) was achieved only for extremely thin films (several nm thick), MIT was observed at 39, 72, and 113 K for films with a thickness of 50 nm. The electronic structure was investigated by hard and soft X-ray photoemission spectroscopy (HX-PES and SX-PES). The difference between these PES results was significant due to the variation in an escape depth of photoelectrons of PES. While HX-PES showed that the V 2p3/2 spectra consisted of four peaks (V5+, V4+, V3+, and V2+/1+), SX-PES showed only three peaks (V5+, V4+, and V3+). This difference can be caused by a strain from the substrate, which leads to the chemical disorder (V5+, V4+, V3+, and V2+/1+). The thin film near the substrate is affected by the strain. The positive magnetoresistance is attributed to the effect of electron-electron interactions in the disorder system. Therefore, the emergence of MIT can be explained by the electron-electron interactions from the chemical disorder due to the strain.

  10. Synthesis and characterization of novel lanthanide- and actinide-containing titanates and zircono-titanates; relevance to nuclear waste disposal

    International Nuclear Information System (INIS)

    Shoup, S.L.S.

    1995-08-01

    Before experiments using actinide elements are performed, synthetic routes are tested using lanthanides of comparable ionic radii as surrogates. Compound and solid solution formation in several lanthanide-containing titanate and zircono-titanate systems have been established using X-ray diffraction (XRD) analysis, which helped to define interesting and novel experiments, some of which have been performed and are discussed, for selected actinide elements. The aqueous solubilities of several lanthanide- and actinide-containing compounds, representative of the systems studied, were tested in several leachants, including the WIPP open-quotes Aclose quotes brine, following modified Materials Characterization Center procedures (MCC-3). The WIPP open-quotes Aclose quotes brine is a synthetic substitute for that found in nature at the Waste Isolation Pilot Plant (WIPP) in New Mexico. The concentrations of cerium, used as a surrogate for plutonium, leached by the WIPP open-quotes Aclose quotes brine from all the cerium-containing compounds and solid solutions tested were below the Inductively Coupled Plasma (ICP) atomic emission spectrometry limit of detection (10 ppm) established for cerium in this brine. The concentrations of plutonium leached from the two plutonium-containing solid solutions were less than 1 ppm as determined by gross alpha counting and alpha pulse height analysis. Concentrations of strontium leached by the WIPP brine from stable strontium containing titanate compounds, studied as possible immobilizers of both 90 Sr and actinide elements, were also quite low. These compound and solid solution formation investigations and the aqueous solubility studies suggest that the types of titanate and zircono-titanate compounds and solid solutions studied in this work appear to be useful as host matrices for nuclear waste immobilization

  11. Diffusion barrier performance of novel Ti/TaN double layers for Cu metallization

    International Nuclear Information System (INIS)

    Zhou, Y.M.; He, M.Z.; Xie, Z.

    2014-01-01

    Highlights: • Novel Ti/TaN double layers offering good stability as a barrier against Cu metallization have been made achievable by annealing in vacuum. • The Ti/TaN double layers improved the adhesion with Cu thin films and showed good diffusion barrier between Cu and SiO 2 /Si up to the annealing condition. • The failure mechanism of Ti/TaN bi-layer is similar with the Cu/TaN/Si metallization system in which Cu atoms diffuse through the grain boundary of barrier and react with silicon to form Cu 3 Si. - Abstract: Novel Ti/TaN double layers offering good stability as a barrier against Cu metallization have been made achievable by annealing in vacuum better than 1 × 10 −3 Pa. Ti/TaN double layers were formed on SiO 2 /Si substrates by DC magnetron sputtering and then the properties of Cu/Ti/TaN/SiO 2 /Si film stacks were studied. It was found that the Ti/TaN double layers provide good diffusion barrier between Cu and SiO 2 /Si up to 750 °C for 30 min. The XRD, Auger and EDS results show that the Cu–Si compounds like Cu 3 Si were formed by Cu diffusion through Ti/TaN barrier for the 800 °C annealed samples. It seems that the improved diffusion barrier property of Cu/Ti/TaN/SiO 2 /Si stack is due to the diffusion of nitrogen along the grain boundaries in Ti layer, which would decrease the defects in Ti film and block the diffusion path for Cu diffusion with increasing annealing temperature. The failure mechanism of Ti/TaN bi-layer is similar to the Cu/TaN/Si metallization system in which Cu atoms diffuse through the grain boundary of barrier and react with silicon to form Cu 3 Si

  12. Application of La-Doped SrTiO3 in Advanced Metal-Supported Solid Oxide Fuel Cells

    Directory of Open Access Journals (Sweden)

    Sabrina Presto

    2018-03-01

    Full Text Available Composite materials frequently allow the drawbacks of single components to be overcome thanks to a synergistic combination of material- and structure-specific features, leading to enhanced and also new properties. This is the case of a metallic-ceramic composite, a nickel-chromium-aluminum (NiCrAl foam impregnated with La-doped Strontium Titanate (LST. This particular cermet has very interesting properties that can be used in different fields of application, namely: mechanical robustness provided by the metal foam; and chemical stability in harsh conditions of temperature and atmosphere by promotion of a thin protective layer of alumina (Al2O3; high electronic conductivity given by a percolating ceramic conducting phase, i.e., La-doped Strontium Titanate. In this paper, its application as a current collector in a metal-supported Solid Oxide Fuel Cells (SOFC was studied. Firstly, the electronic properties of different compositions, stoichiometric and under stoichiometric, of LST were analyzed to choose the best one in terms of conductivity and phase purity. Then, LST chemical stability was studied in the presence of Al2O3 at different temperatures, gas compositions and aging times. Finally, stability and conductivity of LST-impregnated NiCrAl foam composite materials were measured, and LST was found to be fully compatible with the NiCrAl foam, as no reactions were detected in oxidizing and reducing atmosphere after up to 300 h operation at 750 °C and 900 °C between the Al2O3 layer and LST. Results showed that the composite is suitable as a current collector in innovative designs of metal-supported SOFC, like the Evolve cell, in which the metallic part is supposed not only to provide the structural stability to the cell, but also to play the role of current collector due to the impregnation of ceramic material.

  13. Radiation stability of sodium titanate ion exchange materials

    International Nuclear Information System (INIS)

    Kenna, B.T.

    1980-02-01

    Sodium titanate and sodium titanate loaded macroreticular resin are being considered as ion exchangers to remove 90 Sr and actinides from the large volume of defense waste stored at Hanford Site in Washington. Preliminary studies to determine the radiation effect on Sr +2 and I - capacity of these ion-exchange materials were conducted. Samples of sodium titanate powder, sodium titanate loaded macroreticular resin, as well as the nitrate form of macroreticular anion resin were irradiated with up to 2 x 10 9 Rads of 60 Co gamma rays. Sodium titanate cation capacity decreased about 50% while the sodium titanate loaded macroeticular resin displayed a dramatic decrease in cation capacity when irradiated with 10 8 -10 9 Rad. The latter decrease is tentatively ascribed to radiation damage to the organic portion which subsequently inhibits interaction with the contained sodium titanate. The anion capacity of both macroreticular resin and sodium titanate loaded macroreticular resin exhibited significant decreases with increasing radiation exposure. These results suggest that consideration should be given to the potential effects of radiation degradation if column regeneration is to be used. 5 figures, 2 tables

  14. Improvement of conditions for ceramics sintering on the base of lead zirconate-titanate

    International Nuclear Information System (INIS)

    Glinchuk, M.D.; Kim, P.V.; Bykov, I.P.; Lyashchenko, A.B.

    1989-01-01

    Lead zirconate-titanate powders of different graininess are studied for their phase composition. The finest grains of the powder consist of lead zirconate-titanate with the rhombohedral structure. Grains of 3-5 μm size are a mixture of lead zirconate-titanate and lead titanate, the latter exceeding 50% (by weight) causes the effect of anomalous expansion in the process of sintering. Control of the technological parameters of the synthesis permits producing powder with favourable correlation of the above phases and grain sizes. Sintering of such a powder induces no effect of the anomalous expansion with an increased density of the product attained

  15. MICROSTRUCTURE CHARACTERISTIC OF ALUMINUM TITANATE SYNTHESIED BY BOTH SOLID- STATE AND SOL-GEL PROCESSES

    Directory of Open Access Journals (Sweden)

    M. Khosravi Saghezchi

    2015-12-01

    Full Text Available A comparing study on formation and microstructure features of aluminum titanate is investigated through both solid-state and sol-gel processes. Aluminum titanate formed by firing at 1350ºC and 1450ºC for 4h in solid-state process. In the sol-gel process formation of submicron sized particles is followed by addition of sucrose into the transparent sol. XRD analysis was confirmed the formation of aluminum titanate at 1400ºC  in lower duration of calcination (3h without any additives in the sol-gel process. In this work 2wt% MgO is added to the samples as the additive for forming acceleration of aluminum titanate. The influence of MgO addition and heat treatment are studied on phase formation and microstructure development of aluminum titanate in both procedures. Additive optimizes aluminum titanate formation at lower temperatures (1300-1350ºC. Phase and microstructure studies of Mg containing samples optimally show significance in aluminum titanate formation.

  16. Chemistry of the galactic cosmic ray induced ionosphere of Titan

    Science.gov (United States)

    Molina-Cuberos, G. J.; López-Moreno, J. J.; Rodrigo, R.; Lara, L. M.

    1999-09-01

    Titan's lower ionosphere (from 1 to 400 km) has been studied with a one-dimensional ion-neutral model. In this region of the atmosphere, galactic cosmic rays (GCRs) are the main ionization source. They penetrate to the deeper atmosphere and ionize the neutral constituents of Titan's atmosphere (mainly N2, CH4, Ar, H2, and CO) to produce N2+, N+, Ar+, CH4+, CH3+, CH2+, H2+, H+, and CO+. Fast reactions with the neutrals convert these ions into ions such as CH5+, C2H5+, and N2H+. Different pathways are proposed to obtain the ion and electron densities. The most abundant ions are cluster ions, like CH5+.CH4, HCO+.H2, and HCNH+.C2H4, and long chain hydrocarbon ions. In atmospheres very rich in N2, such as Titan's, ions like H4C7N+ and CH3CNH+ also represent an important contribution to the total positive ion density. Three-body reactions may play an important role in the dense atmosphere of Titan, and special attention is devoted to them. The calculated electron density in the lower atmosphere reaches a peak of ~2150 cm-3 at an altitude of 90 km.

  17. Overview of the TITAN-II reversed-field pinch aqueous fusion power core design

    Energy Technology Data Exchange (ETDEWEB)

    Wong, C.P.C.; Creedon, R.L.; Grotz, S.; Cheng, E.T.; Sharafat, S.; Cooke, P.I.H.

    1988-03-01

    TITAN-II is a compact, high power density Reversed-Field Pinch fusion power reactor design based on the aqueous lithium solution fusion power core concept. The selected breeding and structural materials are LiNO/sub 3/ and 9-C low activation ferritic steel, respectively. TITAN-II is a viable alternative to the TITAN-I lithium self-cooled design for the Reversed-Field Pinch reactor to operate at a neutron wall loading of 18 MWm/sup 2/. Submerging the complete fusion power core and the primary loop in a large pool of cool water will minimize the probability of radioactivity release. Since the protection of the large pool integrity is the only requirement for the protection of the public, TITAN-II is a passive safety assurance design. 13 refs., 3 figs., 1 tab.

  18. Measurement of thermal conductance of La0.7Sr0.3MnO3 thin films deposited on SrTiO3 and MgO substrates

    Science.gov (United States)

    Aryan, A.; Guillet, B.; Routoure, J. M.; Fur, C.; Langlois, P.; Méchin, L.

    2015-01-01

    We present measurements of the thermal conductance of thin-film-on-substrate structures that could serve as thin film uncooled bolometers. Studied samples were 75 nm thick epitaxial La0.7Sr0.3MnO3 thin films deposited on SrTiO3 (0 0 1) and MgO (0 0 1) substrates patterned in square geometries of areas ranging from 50 μm × 50 μm to 200 μm × 200 μm. The model allows estimating thermal boundary conductance values at the interface between film and substrate of 0.28 ± 0.08 × 106 W K-1 m-2 for LSMO/STO (0 0 1) and 5.8 ± 3.0 × 106 W K-1 m-2 for LSMO/MgO (0 0 1) from measurements performed in the static regime. Analytical expressions of thermal conductance and thermal capacitance versus modulation frequency are compared to measurements of the elevation temperature due to absorbed incoming optical power. The overall good agreement found between measurements and model finally provides the possibility to calculate the bolometric response of thin film bolometers, thus predicting their frequency response for various geometries.

  19. Large Abundances of Polycyclic Aromatic Hydrocarbons in Titan's Upper Atmosphere

    Science.gov (United States)

    Lopez-Puertas, M.; Dinelli, B. M.; Adriani, A.; Funke, B.; Garcia-Comas, M.; Moriconi, M. L.; D'Aversa, E.; Boersma, C.; Allamandola, L. J.

    2013-01-01

    In this paper, we analyze the strong unidentified emission near 3.28 micron in Titan's upper daytime atmosphere recently discovered by Dinelli et al.We have studied it by using the NASA Ames PAH IR Spectroscopic Database. The polycyclic aromatic hydrocarbons (PAHs), after absorbing UV solar radiation, are able to emit strongly near 3.3 micron. By using current models for the redistribution of the absorbed UV energy, we have explained the observed spectral feature and have derived the vertical distribution of PAH abundances in Titan's upper atmosphere. PAHs have been found to be present in large concentrations, about (2-3) × 10(exp 4) particles / cubic cm. The identified PAHs have 9-96 carbons, with a concentration-weighted average of 34 carbons. The mean mass is approx 430 u; the mean area is about 0.53 sq. nm; they are formed by 10-11 rings on average, and about one-third of them contain nitrogen atoms. Recently, benzene together with light aromatic species as well as small concentrations of heavy positive and negative ions have been detected in Titan's upper atmosphere. We suggest that the large concentrations of PAHs found here are the neutral counterpart of those positive and negative ions, which hence supports the theory that the origin of Titan main haze layer is located in the upper atmosphere.

  20. Development of partitioning method: adsorption behavior of Sr on titanic acid pelletized with binder

    Energy Technology Data Exchange (ETDEWEB)

    Mizoguchi, Kenichi; Yamaguchi, Isoo; Morita, Yasuji; Yamagishi, Isao; Fujiwara, Takeshi; Kubota, Masumitsu [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

    1998-05-01

    The adsorption behavior of Sr was examined with the titanic acid with the binder and with binderless titanic acid. Then the effect of the difference of the neutralizer was also examined. When the initial concentration of Sr was constant, distribution coefficient (Kd) increased with pH after adsorption. At pH 4, Kd decreased in order of the titanic acid neutralized with NH{sub 4}OH solution without the binder > the titanic acid neutralized with NH{sub 4}OH solution and pelletized with the binder > the titanic acid neutralized with KOH solution and pelletized with the binder. At pH 6, Kd decreased with increasing the concentration of Sr in the solution, but the decreasing tendency of Kd for each titanic acid was the same. Adsorption kinetics was examined with titanic acids neutralized with NH{sub 4}OH solution, keeping the initial concentration of Sr and the initial pH constant. It took about one hour to reach Kd of 100mL/g for the titanic acid without the binder but over 10 hours for the titanic acid pelletized with the binder. It was confirmed that by pelletizing titanic acid with the binder, Kd of Sr became small and it took very long time to reach the adsorption equilibrium. However, by sufficient conditioning with water of the titanic acid pelletized with the binder, 1) it took about half time of titanic acid without conditioning to reach Kd of 100mL/g, 2) after 24 hours mixing, Kd for the titanic acid pelletized with the binder was almost equal to that for the titanic acid without the binder, 3) apparent ion exchange capacity obtained through a column test became over about 1meq/g. (J.P.N.)

  1. Development of partitioning method: adsorption behavior of Sr on titanic acid pelletized with binder

    International Nuclear Information System (INIS)

    Mizoguchi, Kenichi; Yamaguchi, Isoo; Morita, Yasuji; Yamagishi, Isao; Fujiwara, Takeshi; Kubota, Masumitsu

    1998-05-01

    The adsorption behavior of Sr was examined with the titanic acid with the binder and with binderless titanic acid. Then the effect of the difference of the neutralizer was also examined. When the initial concentration of Sr was constant, distribution coefficient (Kd) increased with pH after adsorption. At pH 4, Kd decreased in order of the titanic acid neutralized with NH 4 OH solution without the binder > the titanic acid neutralized with NH 4 OH solution and pelletized with the binder > the titanic acid neutralized with KOH solution and pelletized with the binder. At pH 6, Kd decreased with increasing the concentration of Sr in the solution, but the decreasing tendency of Kd for each titanic acid was the same. Adsorption kinetics was examined with titanic acids neutralized with NH 4 OH solution, keeping the initial concentration of Sr and the initial pH constant. It took about one hour to reach Kd of 100mL/g for the titanic acid without the binder but over 10 hours for the titanic acid pelletized with the binder. It was confirmed that by pelletizing titanic acid with the binder, Kd of Sr became small and it took very long time to reach the adsorption equilibrium. However, by sufficient conditioning with water of the titanic acid pelletized with the binder, 1) it took about half time of titanic acid without conditioning to reach Kd of 100mL/g, 2) after 24 hours mixing, Kd for the titanic acid pelletized with the binder was almost equal to that for the titanic acid without the binder, 3) apparent ion exchange capacity obtained through a column test became over about 1meq/g. (J.P.N.)

  2. Photoresponse in La0.9Hf0.1MnO3/0.05wt%Nb-doped SrTiO3 heteroepitaxial junctions

    Science.gov (United States)

    Qi, Yaping; Ni, Hao; Zheng, Ming; Zeng, Jiali; Jiang, Yucheng; Gao, Ju

    2018-05-01

    Excellent photo detectors need to have the rapid response and good repeatability from the requirement of industrial applications. In this paper, transport behavior and opto-response of heterostructures made with La0.9Hf0.1MnO3 and 0.05wt%Nb-doped SrTiO3 were investigated. The heterojunctions exhibited an excellent rectifying feature with very low leakage in a broad temperature region (from 40 to 300 K). These thin films presented persistent and stable photovoltages upon light illumination. Rapid shift between small and large voltages corresponding to "light OFF" and "light ON" states, respectively, was observed, demonstrating reliable photo detection behavior. A semiconductor laser with a wavelength of 650 nm was used as the light source. It is also noted that the observed photovoltages are strongly determined by light intensity. The injection of photoexcited charge carriers (electrons) could be responsible for the appearance of the observed opto-response. Such manipulative features by light irradiation exhibit great potential for light detectors for visible light.

  3. Photoresponse in La0.9Hf0.1MnO3/0.05wt%Nb-doped SrTiO3 heteroepitaxial junctions

    Directory of Open Access Journals (Sweden)

    Yaping Qi

    2018-05-01

    Full Text Available Excellent photo detectors need to have the rapid response and good repeatability from the requirement of industrial applications. In this paper, transport behavior and opto-response of heterostructures made with La0.9Hf0.1MnO3 and 0.05wt%Nb-doped SrTiO3 were investigated. The heterojunctions exhibited an excellent rectifying feature with very low leakage in a broad temperature region (from 40 to 300 K. These thin films presented persistent and stable photovoltages upon light illumination. Rapid shift between small and large voltages corresponding to “light OFF” and “light ON” states, respectively, was observed, demonstrating reliable photo detection behavior. A semiconductor laser with a wavelength of 650 nm was used as the light source. It is also noted that the observed photovoltages are strongly determined by light intensity. The injection of photoexcited charge carriers (electrons could be responsible for the appearance of the observed opto-response. Such manipulative features by light irradiation exhibit great potential for light detectors for visible light.

  4. Epitaxial c-axis oriented BaTiO3 thin films on SrTiO3-buffered Si(001) by atomic layer deposition

    International Nuclear Information System (INIS)

    Ngo, Thong Q.; McDaniel, Martin D.; Ekerdt, John G.; Posadas, Agham B.; Demkov, Alexander A.; Hu, Chengqing; Yu, Edward T.; Bruley, John

    2014-01-01

    Atomic layer deposition (ALD) of epitaxial c-axis oriented BaTiO 3 (BTO) on Si(001) using a thin (1.6 nm) buffer layer of SrTiO 3 (STO) grown by molecular beam epitaxy is reported. The ALD growth of crystalline BTO films at 225  °C used barium bis(triisopropylcyclopentadienyl), titanium tetraisopropoxide, and water as co-reactants. X-ray diffraction (XRD) reveals a high degree of crystallinity and c-axis orientation of as-deposited BTO films. Crystallinity is improved after vacuum annealing at 600  °C. Two-dimensional XRD confirms the tetragonal structure and orientation of 7–20-nm thick films. The effect of the annealing process on the BTO structure is discussed. A clean STO/Si interface is found using in-situ X-ray photoelectron spectroscopy and confirmed by cross-sectional scanning transmission electron microscopy. The capacitance-voltage characteristics of 7–20 nm-thick BTO films are examined and show an effective dielectric constant of ∼660 for the heterostructure

  5. Two-Dimensional Electron Gas at SrTiO3-Based Oxide Heterostructures via Atomic Layer Deposition

    Directory of Open Access Journals (Sweden)

    Sang Woon Lee

    2016-01-01

    Full Text Available Two-dimensional electron gas (2DEG at an oxide interface has been attracting considerable attention for physics research and nanoelectronic applications. Early studies reported the formation of 2DEG at semiconductor interfaces (e.g., AlGaAs/GaAs heterostructures with interesting electrical properties such as high electron mobility. Besides 2DEG formation at semiconductor junctions, 2DEG was realized at the interface of an oxide heterostructure such as the LaAlO3/SrTiO3 (LAO/STO heterojunction. The origin of 2DEG was attributed to the well-known “polar catastrophe” mechanism in oxide heterostructures, which consist of an epitaxial LAO layer on a single crystalline STO substrate among proposed mechanisms. Recently, it was reported that the creation of 2DEG was achieved using the atomic layer deposition (ALD technique, which opens new functionality of ALD in emerging nanoelectronics. This review is focused on the origin of 2DEG at oxide heterostructures using the ALD process. In particular, it addresses the origin of 2DEG at oxide interfaces based on an alternative mechanism (i.e., oxygen vacancies.

  6. Freeze cast porous barium titanate for enhanced piezoelectric energy harvesting

    Science.gov (United States)

    Roscow, J. I.; Zhang, Y.; Kraśny, M. J.; Lewis, R. W. C.; Taylor, J.; Bowen, C. R.

    2018-06-01

    Energy harvesting is an important developing technology for a new generation of self-powered sensor networks. This paper demonstrates the significant improvement in the piezoelectric energy harvesting performance of barium titanate by forming highly aligned porosity using freeze casting. Firstly, a finite element model demonstrating the effect of pore morphology and angle with respect to poling field on the poling behaviour of porous ferroelectrics was developed. A second model was then developed to understand the influence of microstructure-property relationships on the poling behaviour of porous freeze cast ferroelectric materials and their resultant piezoelectric and energy harvesting properties. To compare with model predictions, porous barium titanate was fabricated using freeze casting to form highly aligned microstructures with excellent longitudinal piezoelectric strain coefficients, d 33. The freeze cast barium titanate with 45 vol.% porosity had a d 33  =  134.5 pC N‑1 compared to d 33  =  144.5 pC N‑1 for dense barium titanate. The d 33 coefficients of the freeze cast materials were also higher than materials with uniformly distributed spherical porosity due to improved poling of the aligned microstructures, as predicted by the models. Both model and experimental data indicated that introducing porosity provides a large reduction in the permittivity () of barium titanate, which leads to a substantial increase in energy harvesting figure of merit, , with a maximum of 3.79 pm2 N‑1 for barium titanate with 45 vol.% porosity, compared to only 1.40 pm2 N‑1 for dense barium titanate. Dense and porous barium titanate materials were then used to harvest energy from a mechanical excitation by rectification and storage of the piezoelectric charge on a capacitor. The porous barium titanate charged the capacitor to a voltage of 234 mV compared to 96 mV for the dense material, indicating a 2.4-fold increase that was similar to that

  7. Titan's Stratospheric Condensibles at High Northern Latitudes During Northern Winter

    Science.gov (United States)

    Anderson, Carrie; Samuelson, R.; Achterberg, R.

    2012-01-01

    The Infrared Interferometer Spectrometer (IRIS) instrument on board Voyager 1 caught the first glimpse of an unidentified particulate feature in Titan's stratosphere that spectrally peaks at 221 per centimeter. Until recently, this feature that we have termed 'the haystack,' has been seen persistently at high northern latitudes with the Composite Infrared Spectrometer (CIRS) instrument onboard Cassini, The strength of the haystack emission feature diminishes rapidly with season, becoming drastically reduced at high northern latitudes, as Titan transitions from northern winter into spring, In contrast to IRIS whose shortest wavenumber was 200 per centimeter, CIRS extends down to 10 per centimeter, thus revealing an entirely unexplored spectral region in which nitrile ices have numerous broad lattice vibration features, Unlike the haystack, which is only found at high northern latitudes during northern winter/early northern spring, this geometrically thin nitrile cloud pervades Titan's lower stratosphere, spectrally peaking at 160 per centimeter, and is almost global in extent spanning latitudes 85 N to 600 S, The inference of nitrile ices are consistent with the highly restricted altitude ranges over which these features are observed, and appear to be dominated by a mixture of HCN and HC3N, The narrow range in altitude over which the nitrile ices extend is unlike the haystack, whose vertical distribution is significantly broader, spanning roughly 70 kilometers in altitude in Titan's lower stratosphere, The nitrile clouds that CIRS observes are located in a dynamically stable region of Titan's atmosphere, whereas CH4 clouds, which ordinarily form in the troposphere, form in a more dynamically unstable region, where convective cloud systems tend to occur. In the unusual situation where Titan's tropopause cools significantly from the HASI 70.5K temperature minimum, CH4 should condense in Titan's lower stratosphere, just like the aforementioned nitrile clouds, although

  8. Seasonal Changes in Titan's Meteorology

    Science.gov (United States)

    Turtle, E. P.; DelGenio, A. D.; Barbara, J. M.; Perry, J. E.; Schaller, E. L.; McEwen, A. S.; West, R. A.; Ray, T. L.

    2011-01-01

    The Cassini Imaging Science Subsystem has observed Titan for 1/4 Titan year, and we report here the first evidence of seasonal shifts in preferred locations of tropospheric methane clouds. South \\polar convective cloud activity, common in late southern summer, has become rare. North \\polar and northern mid \\latitude clouds appeared during the approach to the northern spring equinox in August 2009. Recent observations have shown extensive cloud systems at low latitudes. In contrast, southern mid \\latitude and subtropical clouds have appeared sporadically throughout the mission, exhibiting little seasonality to date. These differences in behavior suggest that Titan s clouds, and thus its general circulation, are influenced by both the rapid temperature response of a low \\thermal \\inertia surface and the much longer radiative timescale of Titan s cold thick troposphere. North \\polar clouds are often seen near lakes and seas, suggesting that local increases in methane concentration and/or lifting generated by surface roughness gradients may promote cloud formation. Citation

  9. Chemistry in Titan

    Science.gov (United States)

    Plessis, S.; Carrasco, N.; Pernot, P.

    2009-04-01

    Modelling the chemical composition of Titan's ionosphere is a very challenging issue. Latest works perform either inversion of CASSINI's INMS mass spectra (neutral[1] or ion[2]), or design coupled ion-neutral chemistry models[3]. Coupling ionic and neutral chemistry has been reported to be an essential feature of accurate modelling[3]. Electron Dissociative Recombination (EDR), where free electrons recombine with positive ions to produce neutral species, is a key component of ion-neutral coupling. There is a major difficulty in EDR modelling: for heavy ions, the distribution of neutral products is incompletely characterized by experiments. For instance, for some hydrocarbon ions only the carbon repartition is measured, leaving the hydrogen repartition and thus the exact neutral species identity unknown[4]. This precludes reliable deterministic modelling of this process and of ion-neutral coupling. We propose a novel stochastic description of the EDR chemical reactions which enables efficient representation and simulation of the partial experimental knowledge. The description of products distribution in multi-pathways reactions is based on branching ratios, which should sum to unity. The keystone of our approach is the design of a probability density function accounting for all available informations and physical constrains. This is done by Dirichlet modelling which enables one to sample random variables whose sum is constant[5]. The specifics of EDR partial uncertainty call for a hierarchiral Dirichlet representation, which generalizes our previous work[5]. We present results on the importance of ion-neutral coupling based on our stochastic model. C repartition H repartition (measured) (unknown ) → C4H2 + 3H2 + H .. -→ C4 . → C4H2 + 7H → C3H8. + CH C4H+9 + e- -→ C3 + C .. → C3H3 + CH2 + 2H2 → C2H6 + C2H2 + H .. -→ C2 + C2 . → 2C2H2 + 2H2 + H (1) References [1] J. Cui, R.V. Yelle, V. Vuitton, J.H. Waite Jr., W.T. Kasprzak

  10. High Ic, YBa2Cu3O7-x films grown at very high rates by liquid assisted growth incorporating lightly Au-doped SrTiO3 buffers

    International Nuclear Information System (INIS)

    Kursumovic, A; Durrell, J H; Harrington, S; Wimbush, S; MacManus-Driscoll, J L; Maiorov, B; Zhou, H; Stan, L; Holesinger, T G; Wang, H

    2009-01-01

    YBa 2 Cu 3 O 7-x (YBCO) thick films were grown by hybrid liquid phase epitaxy (HLPE) on (001) SrTiO 3 (STO) substrates. In the presence of a 100 nm thick, 5 mol% Au-doped STO buffer, self-field critical current densities, J c sf , at 77 K of ∼2.4 MA cm -2 and critical currents, I c sf , up to 700 A (cm-width) -1 were achieved. The J c value is virtually independent of thickness and the growth rates are very high (∼1 μm min -1 ). From transmission electron microscopy (TEM), Y 2 O 3 nanocloud extended defects (∼100 nm in size) were identified as the pinning defects in the films. Enhanced random pinning was induced by the presence of Au in the buffer.

  11. The tides of Titan.

    Science.gov (United States)

    Iess, Luciano; Jacobson, Robert A; Ducci, Marco; Stevenson, David J; Lunine, Jonathan I; Armstrong, John W; Asmar, Sami W; Racioppa, Paolo; Rappaport, Nicole J; Tortora, Paolo

    2012-07-27

    We have detected in Cassini spacecraft data the signature of the periodic tidal stresses within Titan, driven by the eccentricity (e = 0.028) of its 16-day orbit around Saturn. Precise measurements of the acceleration of Cassini during six close flybys between 2006 and 2011 have revealed that Titan responds to the variable tidal field exerted by Saturn with periodic changes of its quadrupole gravity, at about 4% of the static value. Two independent determinations of the corresponding degree-2 Love number yield k(2) = 0.589 ± 0.150 and k(2) = 0.637 ± 0.224 (2σ). Such a large response to the tidal field requires that Titan's interior be deformable over time scales of the orbital period, in a way that is consistent with a global ocean at depth.

  12. Applications of inorganic ion exchangers; I-sorption and fixation of some radionuclides in synthetic iron (III)titanate ion exchanger

    International Nuclear Information System (INIS)

    Abou-Mesalam, M.M.; El-Naggar, I.M.

    2002-01-01

    Iron(III) titanate as inorganic ion exchange material has been synthesized by addition of ferric nitrate solution to titanium tetrachloride (dissolved in 4M HCI) with molar ratio equal to unity. The data obtained proposed that the chemical formula of iron(III) titanate may written either as Fe 1 .3 (TiO). 2h 2 O or Fe(TiO 4 ) 0 .76.1.5H 2 O. The surface area values of unloaded and loaded iron(III) titanate with Cs + , Co 2 + and Eu 3 + ions were measured using BET-technique. The selectiy sequence for sorption of Cs + , Co 2 + and Fu 3 + ions on iron (III) titanate was found to be; Co 2 + > Eu 3 + > Cs + . The leach rate values of Cs + , Co 2 + and Fu 3 + ions from iron (II) titanate heated to 1000 degree C different leachants were determined and shows lower values compared to those obtained from unheated iron (III) titanate (dried at 50 degree C) which elucidate the suitability of iron (III) titanate in fixation of Cs + , Co 2 + and Eu 3 + ions by thermal treatment up to1000 degree.

  13. Titan's cold case files - Outstanding questions after Cassini-Huygens

    Science.gov (United States)

    Nixon, C. A.; Lorenz, R. D.; Achterberg, R. K.; Buch, A.; Coll, P.; Clark, R. N.; Courtin, R.; Hayes, A.; Iess, L.; Johnson, R. E.; Lopes, R. M. C.; Mastrogiuseppe, M.; Mandt, K.; Mitchell, D. G.; Raulin, F.; Rymer, A. M.; Todd Smith, H.; Solomonidou, A.; Sotin, C.; Strobel, D.; Turtle, E. P.; Vuitton, V.; West, R. A.; Yelle, R. V.

    2018-06-01

    The entry of the Cassini-Huygens spacecraft into orbit around Saturn in July 2004 marked the start of a golden era in the exploration of Titan, Saturn's giant moon. During the Prime Mission (2004-2008), ground-breaking discoveries were made by the Cassini orbiter including the equatorial dune fields (flyby T3, 2005), northern lakes and seas (T16, 2006), and the large positive and negative ions (T16 & T18, 2006), to name a few. In 2005 the Huygens probe descended through Titan's atmosphere, taking the first close-up pictures of the surface, including large networks of dendritic channels leading to a dried-up seabed, and also obtaining detailed profiles of temperature and gas composition during the atmospheric descent. The discoveries continued through the Equinox Mission (2008-2010) and Solstice Mission (2010-2017) totaling 127 targeted flybys of Titan in all. Now at the end of the mission, we are able to look back on the high-level scientific questions from the start of the mission, and assess the progress that has been made towards answering these. At the same time, new scientific questions regarding Titan have emerged from the discoveries that have been made. In this paper we review a cross-section of important scientific questions that remain partially or completely unanswered, ranging from Titan's deep interior to the exosphere. Our intention is to help formulate the science goals for the next generation of planetary missions to Titan, and to stimulate new experimental, observational and theoretical investigations in the interim.

  14. ALMA observations of Titan's atmospheric chemistry and seasonal variation

    Science.gov (United States)

    Cordiner, Martin

    2017-04-01

    Titan is the largest moon of Saturn, with a thick (1.45 bar) atmosphere composed primarily of molecular nitrogen and methane. Photochemistry in Titan's upper atmosphere results in the production of a wide range of organic molecules, including hydrocarbons, nitriles and aromatics, some of which could be of pre-biotic relevance. Thus, we obtain insights into the possible molecular inventories of primitive (reducing) planetary atmospheres. Titan's atmosphere also provides a unique laboratory for testing our understanding of fundamental processes involving the chemistry and spectroscopy of complex organic molecules. In this talk, results will be presented from our studies using the Atacama Large Millimeter/submillimeter Array (ALMA) during the period 2012-2015, focussing in particular on the detection and mapping of emission from various nitrile species. By combining data from multiple ALMA observations, our spectra have reached an unprecedented sensitivity level, enabling the first spectroscopic detection and mapping of C2H3CN (vinyl cyanide) on Titan. Liquid-phase simulations of Titan's seas indicate that vinyl cyanide molecules could combine to form vesicle membranes (similar to the cells of terrestrial biology), and the astrobiological implications of this discovery will be discussed. Furthermore, ALMA observations provide instantaneous snapshot mapping of Titan's entire Earth-facing hemisphere, for gases inaccessible to previous instruments. Combined with complementary data obtained from the Cassini Saturn orbiter, as well as theoretical models and laboratory studies, our observed, seasonally variable, spatially resolved abundance patterns are capable of providing new insights into photochemical production and transport in primitive planetary atmospheres in the Solar System and beyond.

  15. Organic chemistry on Titan

    Science.gov (United States)

    Chang, S.; Scattergood, T.; Aronowitz, S.; Flores, J.

    1979-01-01

    Features taken from various models of Titan's atmosphere are combined in a working composite model that provides environmental constraints within which different pathways for organic chemical synthesis are determined. Experimental results and theoretical modeling suggest that the organic chemistry of the satellite is dominated by two processes: photochemistry and energetic particle bombardment. Photochemical reactions of CH4 in the upper atmosphere can account for the presence of C2 hydrocarbons. Reactions initiated at various levels of the atmosphere by cosmic rays, Saturn 'wind', and solar wind particle bombardment of a CH4-N2 atmospheric mixture can account for the UV-visible absorbing stratospheric haze, the reddish appearance of the satellite, and some of the C2 hydrocarbons. In the lower atmosphere photochemical processes will be important if surface temperatures are sufficiently high for gaseous NH3 to exist. It is concluded that the surface of Titan may contain ancient or recent organic matter (or both) produced in the atmosphere.

  16. Titan LEAF: A Sky Rover Granting Targeted Access to Titan's Lakes and Plains

    Science.gov (United States)

    Ross, Floyd; Lee, Greg; Sokol, Daniel; Goldman, Benjamin; Bolisay, Linden

    2016-10-01

    Northrop Grumman, in collaboration with L'Garde Inc. and Global Aerospace Corporation (GAC), has been developing the Titan Lifting Entry Atmospheric Flight (T-LEAF) sky rover to roam the atmosphere and observe at close quarters the lakes and plains of Titan. T-LEAF also supports surface exploration and science by providing precision delivery of in situ instruments to the surface.T-LEAF is a maneuverable, buoyant air vehicle. Its aerodynamic shape provides its maneuverability, and its internal helium envelope reduces propulsion power requirements and also the risk of crashing. Because of these features, T-LEAF is not restricted to following prevailing wind patterns. This freedom of mobility allows it be commanded to follow the shorelines of Titan's methane lakes, for example, or to target very specific surface locations.T-LEAF utilizes a variable power propulsion system, from high power at ~200W to low power at ~50W. High power mode uses the propellers and control surfaces for additional mobility and maneuverability. It also allows the vehicle to hover over specific locations for long duration surface observations. Low power mode utilizes GAC's Titan Winged Aerobot (TWA) concept, currently being developed with NASA funding, which achieves guided flight without the use of propellers or control surfaces. Although slower than high powered flight, this mode grants increased power to science instruments while still maintaining control over direction of travel.Additionally, T-LEAF is its own entry vehicle, with its leading edges protected by flexible thermal protection system (f-TPS) materials already being tested by NASA's Hypersonic Inflatable Aerodynamic Decelerator (HIAD) group. This f-TPS technology allows T-LEAF to inflate in space, like HIAD, and then enter the atmosphere fully deployed. This approach accommodates entry velocities from as low as ~1.8 km/s if entering from Titan orbit, up to ~6 km/s if entering directly from Saturn orbit, like the Huygens probe

  17. Ferroelectric Polarization-Modulated Interfacial Fine Structures Involving Two-Dimensional Electron Gases in Pb(Zr,Ti)O3/LaAlO3/SrTiO3 Heterostructures.

    Science.gov (United States)

    Wang, Shuangbao; Bai, Yuhang; Xie, Lin; Li, Chen; Key, Julian D; Wu, Di; Wang, Peng; Pan, Xiaoqing

    2018-01-10

    Interfacial fine structures of bare LaAlO 3 /SrTiO 3 (LAO/STO) heterostructures are compared with those of LAO/STO heterostructures capped with upward-polarized Pb(Zr 0.1 ,Ti 0.9 )O 3 (PZT up ) or downward-polarized Pb(Zr 0.5 ,Ti 0.5 )O 3 (PZT down ) overlayers by aberration-corrected scanning transmission electron microscopy experiments. By combining the acquired electron energy-loss spectroscopy mapping, we are able to directly observe electron transfer from Ti 4+ to Ti 3+ and ionic displacements at the interface of bare LAO/STO and PZT down /LAO/STO heterostructure unit cell by unit cell. No evidence of Ti 3+ is observed at the interface of the PZT up /LAO/STO samples. Furthermore, the confinement of the two-dimensional electron gas (2DEG) at the interface is determined by atomic-column spatial resolution. Compared with the bare LAO/STO interface, the 2DEG density at the LAO/STO interface is enhanced or depressed by the PZT down or PZT up overlayer, respectively. Our microscopy studies shed light on the mechanism of ferroelectric modulation of interfacial transport at polar/nonpolar oxide heterointerfaces, which may facilitate applications of these materials as nonvolatile memory.

  18. Titan the earth-like moon

    CERN Document Server

    Coustenis, Athena

    1999-01-01

    This is the first book to deal with Titan, one of the most mysterious bodies in the solar system. The largest satellite of the giant planet Saturn, Titan is itself larger than the planet Mercury, and is unique in being the only known moon with a thick atmosphere. In addition, its atmosphere bears a startling resemblance to the Earth's, but is much colder.The American and European space agencies, NASA and ESA, have recently combined efforts to send a huge robot spacecraft to orbit Saturn and land on Titan. This book provides the background to this, the greatest deep space venture of our time, a

  19. Conventional hydrothermal synthesis of titanate nanotubes: Systematic discussions on structural, optical, thermal and morphological properties

    Directory of Open Access Journals (Sweden)

    S. Muniyappan

    2017-12-01

    Full Text Available Titanate nanotubes were successfully synthesized by hydrothermal technique under acidic-base medium. The anatase and titanate phase of the starting TiO2 and tubular titanate was confirmed by powder XRD technique. The UV–vis-NIR spectroscopy was used to study the absorption nature of titanate nanotubes and the band gap was calculated as 3.3 eV. Infrared technique was employed to detect the presence of all the functional groups in the synthesized titanate nanotube material. Thermal properties of the title material were studied by TG-DTA analyses. The shrinkage of interlayer distance of TiO2 network confirms the nanotube formation. Morphology and size information about the synthesized material were carried out using FESEM and TEM analysis. Titanate nanotubes are having the maximum length of 2.24 µm and the average diameter of 169.73 nm. EDX analysis gives out the elemental composition of the as synthesized product. This report may fetch an efficient way to synthesize TiO2 nanotubes using TiO2 nanoparticles.

  20. Upconversion emission study of Er3+/Yb3+ doped barium titanate phosphor prepared by co-precipitation method

    International Nuclear Information System (INIS)

    Mahata, M.K.; Dey, R.; Kumar, K.; Rai, V.K.; Rai, S.B.

    2012-01-01

    In the present work we have successfully synthesized the Er 3+ , Yb 3+ doped barium titanate phosphor via co-precipitation synthesis method. Under 980 nm excitation, tri-color upconversion fluorescence has been observed. The Fourier Transform Infrared measurement was done to check the presence of organic impurities. In order to find out how many photons are involved in each emission band, the variation of UC emission intensity of the codoped phosphor is studied with increase in excitation power. Upconversion emission spectra show that as the annealing temperature of the powder is increased, intensity of red emission decreases and intensity of green emission increases due to the decrease in maximum phonon frequency of the host material. (author)

  1. Titan and habitable planets around M-dwarfs.

    Science.gov (United States)

    Lunine, Jonathan I

    2010-01-01

    The Cassini-Huygens mission discovered an active "hydrologic cycle" on Saturn's giant moon Titan, in which methane takes the place of water. Shrouded by a dense nitrogen-methane atmosphere, Titan's surface is blanketed in the equatorial regions by dunes composed of solid organics, sculpted by wind and fluvial erosion, and dotted at the poles with lakes and seas of liquid methane and ethane. The underlying crust is almost certainly water ice, possibly in the form of gas hydrates (clathrate hydrates) dominated by methane as the included species. The processes that work the surface of Titan resemble in their overall balance no other moon in the solar system; instead, they are most like that of the Earth. The presence of methane in place of water, however, means that in any particular planetary system, a body like Titan will always be outside the orbit of an Earth-type planet. Around M-dwarfs, planets with a Titan-like climate will sit at 1 AU--a far more stable environment than the approximately 0.1 AU where Earth-like planets sit. However, an observable Titan-like exoplanet might have to be much larger than Titan itself to be observable, increasing the ratio of heat contributed to the surface atmosphere system from internal (geologic) processes versus photons from the parent star.

  2. PEROXOTITANATE- AND MONOSODIUM METAL-TITANATE COMPOUNDS AS INHIBITORS OF BACTERIAL GROWTH

    Energy Technology Data Exchange (ETDEWEB)

    Hobbs, D.

    2011-01-19

    Sodium titanates are ion-exchange materials that effectively bind a variety of metal ions over a wide pH range. Sodium titanates alone have no known adverse biological effects but metal-exchanged titanates (or metal titanates) can deliver metal ions to mammalian cells to alter cell processes in vitro. In this work, we test a hypothesis that metal-titanate compounds inhibit bacterial growth; demonstration of this principle is one prerequisite to developing metal-based, titanate-delivered antibacterial agents. Focusing initially on oral diseases, we exposed five species of oral bacteria to titanates for 24 h, with or without loading of Au(III), Pd(II), Pt(II), and Pt(IV), and measuring bacterial growth in planktonic assays through increases in optical density. In each experiment, bacterial growth was compared with control cultures of titanates or bacteria alone. We observed no suppression of bacterial growth by the sodium titanates alone, but significant (p < 0.05, two-sided t-tests) suppression was observed with metal-titanate compounds, particularly Au(III)-titanates, but with other metal titanates as well. Growth inhibition ranged from 15 to 100% depending on the metal ion and bacterial species involved. Furthermore, in specific cases, the titanates inhibited bacterial growth 5- to 375-fold versus metal ions alone, suggesting that titanates enhanced metal-bacteria interactions. This work supports further development of metal titanates as a novel class of antibacterials.

  3. Spin-orbit interaction and Kondo scattering at the PrAlO3/SrTiO3 interface: effects of oxygen content

    Science.gov (United States)

    Mozaffari, Shirin; Guchhait, Samaresh; Markert, John T.

    2017-10-01

    We report the effects of oxygen pressure during growth (PO2 ) on the electronic and magnetic properties of PrAlO3 films grown on TiO2 -terminated SrTiO3 substrates. Resistivity measurements show an increase in the sheet resistance as PO2 is increased. The saturation of the sheet resistance down to 0.3 K is consistent with Kondo theory for PO2 ≥slant 10-5 torr. Resistivity data fits indicate Kondo temperatures of 16-18 K. For the 10-4 sample, we measured a moderate positive magnetoresistance (MR) due to a strong spin-orbit (SO) interaction at low magnetic fields that evolves into a larger negative MR at high fields due to the Kondo effect. Analysis of the MR data permitted the extraction of the SO interaction critical field for the PO2=10-5 torr interface ( H_SO=1.25 T). We observed high positive MR for the least oxygenated sample, where a fraction of the n-type carriers are derived from oxygen vacancies and possible cation interdiffusion; for this 6×10-6 torr sample, Hall effect data indicate a thick conducting layer. Its extremely high MR (˜400% ) is attributed to classical behavior due to a distribution of mobilities.

  4. Bipolar and unipolar resistive switching behaviors of sol–gel-derived SrTiO3 thin films with different compliance currents

    International Nuclear Information System (INIS)

    Tang, M H; Wang, Z P; Zeng, Z Q; Xu, X L; Wang, G Y; Zhang, L B; Xiao, Y G; Yang, S B; Jiang, B; Li, J C; He, J

    2011-01-01

    The SrTiO 3 (STO) thin films on a Pt/Ti/SiO 2 /Si substrate were synthesized using a sol–gel method to form a metal–insulator–metal structure. This device shows the bipolar resistance switching (BRS) behavior for a compliance current I cc of less than 0.1 mA but exhibits soft breakdown at a higher level of compliance current. A transition from the BRS behavior to the stable unipolar resistive switching behavior (URS) was also observed. We found that the BRS behavior may be controlled by the structure interface while the URS behavior is likely bulk controlled. Our study indicates that the external compliance current is a key factor in resistance switching phenomenon of STO thin films

  5. Chemical compatibility study of lithium titanate with Indian reduced activation ferritic martensitic steel

    International Nuclear Information System (INIS)

    Sonak, Sagar; Jain, Uttam; Haldar, Rumu; Kumar, Sanjay

    2015-01-01

    Highlights: • Chemical compatibility between Li_2TiO_3 and Indian RAFM steel has been studied at ITER operating temperature. • The lithium titanate chemically reacted with ferritic martensitic steel to form a brittle and non-adherent oxide layer. • The layer grew in a parabolic manner as a function of heating time. • Diffusion of oxygen (from Li_2TiO_3) appears to be controlling the oxide layer. - Abstract: Chemical compatibility between lithium titanate and Indian reduced activation ferritic-martensitic steel (In-RAFMS) was studied for the first time under ITER operating temperature. Lithium titanate required for the study was synthesized in-house. Coupons of In-RAFMS were packed inside lithium titanate powder and heated at 550 °C up to 900 h under inert argon atmosphere. The lithium titanate chemically reacted with ferritic martensitic steel to form a brittle and non-adherent oxide layer. The layer grew in a parabolic manner as a function of heating time. Microstructural and phase evolution of this oxide layer was studied using XRD, SEM and EPMA. Iron and chromium enriched zones were found within the oxide layer. Diffusion of oxygen (from Li_2TiO_3) appears to be controlling the oxide layer.

  6. Detailed exploration of Titan with a Montgolfiere aerobot

    Science.gov (United States)

    Spilker, T.; Tipex Team

    atmosphere is ideal for aerial vehicles, requiring orders of magnitude less power for sustained flight than equivalent vehicles at Earth. Its winds provide mobility unequaled by any ground-based platform, and even controllability by the same techniques used by hot-air balloonists on Earth. The study team also found that the Montgolfiere approach is most effective when it is supported by a Titan orbiter that provides data relay as well as its own science observations. 1 Operationally, the Montgolfiere is seen as an evolutionary step from the Huygens probe, adding controlled buoyancy to the long list of Huygens demonstrations, thus enabling greatly expanded longevity (at least months) and greater data return by 3 to 4 orders of magnitude. It is amenable to long periods of autonomous control, necessary due to the three-hour communication round-trip time to Earth and longer periods out of Earth and orbiter visibility. Tests at Earth show that deployment and inflation under a parachute present no unsolved problems, and that altitude control is simple and accurate, as demonstrated by precision "touch and go" landings, so surface sampling of a limited number of sites at Titan is practical. This presentation will summarize the study team's concept of science objectives, mission architecture, and operations of a Montgolfiere mission to Titan. 2

  7. Effects of PEG4000 template on sol-gel synthesis of porous cerium titanate photocatalyst

    Science.gov (United States)

    Zhang, Wenjie; Tao, Yingjie; Li, Chuanguo

    2018-04-01

    Porous cerium titanate was synthesized by sol-gel method, using polyethylene glycol (PEG4000) as template agent. Brannerite structured CeTi2O6 in monoclinic system is the major substance formed in the materials. Formation of CeO2 and rutile TiO2 depends on the amount of PEG4000. The addition of PEG4000 leads to production of fine particles in the samples, but it does not apparently affect the band gap energy. Pore volume of the cerium titanate sample continuously increases with rising PEG4000 amount. The sample obtained using 3.5 g PEG4000 has BET surface area of 16.2 m2/g and pore volume of 0.0232 cm3/g. The addition of PEG4000 can obviously promote photocatalytic activity of cerium titanate, which can be proven by both enhanced production of hydroxyl radical and ofloxacin degradation efficiency. As much as 95.2% of the initial ofloxacin molecules are removed from the solution after 50 min of photocatalytic degradation on the cerium titanate obtained using 3.5 g PEG4000, while only 48.4% ofloxacin is removed on cerium titanate obtained without PEG4000.

  8. Self-regulated growth of LaVO3 thin films by hybrid molecular beam epitaxy

    International Nuclear Information System (INIS)

    Zhang, Hai-Tian; Engel-Herbert, Roman; Dedon, Liv R.; Martin, Lane W.

    2015-01-01

    LaVO 3 thin films were grown on SrTiO 3 (001) by hybrid molecular beam epitaxy. A volatile metalorganic precursor, vanadium oxytriisopropoxide (VTIP), and elemental La were co-supplied in the presence of a molecular oxygen flux. By keeping the La flux fixed and varying the VTIP flux, stoichiometric LaVO 3 films were obtained for a range of cation flux ratios, indicating the presence of a self-regulated growth window. Films grown under stoichiometric conditions were found to have the largest lattice parameter, which decreased monotonically with increasing amounts of excess La or V. Energy dispersive X-ray spectroscopy and Rutherford backscattering measurements were carried out to confirm film compositions. Stoichiometric growth of complex vanadate thin films independent of cation flux ratios expands upon the previously reported self-regulated growth of perovskite titanates using hybrid molecular beam epitaxy, thus demonstrating the general applicability of this growth approach to other complex oxide materials, where a precise control over film stoichiometry is demanded by the application

  9. Study of the growth of CeO2 nanoparticles onto titanate nanotubes

    Science.gov (United States)

    Marques, Thalles M. F.; Ferreira, Odair P.; da Costa, Jose A. P.; Fujisawa, Kazunori; Terrones, Mauricio; Viana, Bartolomeu C.

    2015-12-01

    We report the study of the growth of CeO2 nanoparticles on the external walls and Ce4+ intercalation within the titanate nanotubes. The materials were fully characterized by multiple techniques, such as: Raman spectroscopy, infrared spectroscopy (FTIR), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The ion exchange processes in the titanate nanotubes were carried out using different concentrations of Ce4+ in aqueous solution. Our results indicate that the growth of CeO2 nanoparticles grown mediated by the hydrolysis in the colloidal species of Ce and the attachment onto the titanate nanotubes happened and get it strongly anchored to the titanate nanotube surface by a simple electrostatic interaction between the nanoparticles and titanate nanotubes, which can explain the small size and even distribution of nanoparticles on titanate supports. It was demonstrated that it is possible to control the amount and size of CeO2 nanoparticles onto the nanotube surface, the species of the Ce ions intercalated between the layers of titanate nanotubes, and the materials could be tuned for using in specific catalysis in according with the amount of CeO2 nanoparticles, their oxygen vacancies/defects and the types of Ce species (Ce4+ or Ce3+) present into the nanotubes.

  10. Titan atmospheric composition by hypervelocity shock layer analysis

    International Nuclear Information System (INIS)

    Nelson, H.F.; Park, C.; Whiting, E.E.

    1989-01-01

    The Cassini Mission, a NASA/ESA cooperative project which includes a deployment of probe into the atmosphere of Titan, is described, with particular attention given to the shock radiometer experiment planned for the Titan probe for the analysis of Titan's atmosphere. Results from a shock layer analysis are presented, demonstrating that the mole fractions of the major species (N2, CH4, and, possibly Ar) in the Titan atmosphere can be successfully determined by the Titan-probe radiometer, by measuring the intensity of the CN(violet) radiation emitted in the shock layer during the high velocity portion of the probe entry between 200 and 400 km altitude. It is shown that the sensitivity of the CN(violet) radiation makes it possible to determine the mole fractions of N2, CH4, and Ar to about 0.015, 0.003, and 0.01, respectively, i.e., much better than the present uncertainties in the composition of Titan atmosphere. 29 refs

  11. A versatile light-switchable nanorod memory: Wurtzite ZnO on perovskite SrTiO3

    KAUST Repository

    Kumar, Anup Bera

    2013-04-25

    Integrating materials with distinct lattice symmetries and dimensions is an effective design strategy toward realizing novel devices with unprecedented functionalities, but many challenges remain in synthesis and device design. Here, a heterojunction memory made of wurtzite ZnO nanorods grown on perovskite Nb-doped SrTiO3 (NSTO) is reported, the electronic properties of which can be drastically reconfigured by applying a voltage and light. Despite of the distinct lattice structures of ZnO and NSTO, a consistent nature of single crystallinity is achieved in the heterojunctions via the low-temperature solution-based hydrothermal growth. In addition to a high and persistent photoconductivity, the ZnO/NSTO heterojunction diode can be turned into a versatile light-switchable resistive switching memory with highly tunable ON and OFF states. The reversible modification of the effective interfacial energy barrier in the concurrent electronic and ionic processes most likely gives rise to the high susceptibility of the ZnO/NSTO heterojunction to external electric and optical stimuli. Furthermore, this facile synthesis route is promising to be generalized to other novel functional nanodevices integrating materials with diverse structures and properties. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Ceria and strontium titanate based electrodes

    DEFF Research Database (Denmark)

    2010-01-01

    A ceramic anode structure obtainable by a process comprising the steps of: (a) providing a slurry by dispersing a powder of an electronically conductive phase and by adding a binder to the dispersion, in which said powder is selected from the group consisting of niobium-doped strontium titanate......, vanadium-doped strontium titanate, tantalum-doped strontium titanate, and mixtures thereof, (b) sintering the slurry of step (a), (c) providing a precursor solution of ceria, said solution containing a solvent and a surfactant, (d) impregnating the resulting sintered structure of step (b...

  13. The key to Mars, Titan and beyond?

    International Nuclear Information System (INIS)

    Zubrin, R.M.

    1990-01-01

    This paper discusses the use of nuclear rockets using indigenous Mars propellants for future missions to Mars and Titan, which would drastically reduce the mass and cost of the mission while increasing its capability. Special attention is given to the CO2-powered nuclear rocket using indigenous Martian fuel (NIMF) vehicle for hopping around on Mars. If water is available on Mars, it could make a NIMF propellant yielding an exhaust velocity of 3.4 km/sec, good enough to allow a piloted NIMF spacecraft to ascent from the surface of Mars and propel itself directly to LEO; if water is available on Phobos, a NIMF spacecraft could travel to earth orbit and then back to Phobos or Mars without any additional propellant from earth. One of the many exciting missions beyond Mars that will be made possible by NIMF technology is the exploration of Saturn's moon Titan. A small automated NIMF Titan explorer, with foldout wings and a NERVA (Nuclear Engine for Rocket Vehicle Applications) engine, is proposed

  14. Temperature dependence of photoluminescence spectra of bilayer two-dimensional electron gases in LaAlO3/SrTiO3 superlattices: coexistence of Auger recombination and single-carrier trapping

    Directory of Open Access Journals (Sweden)

    H. J. Harsan Ma

    2015-06-01

    Full Text Available We report emerging photoluminescence (PL of bilayer two-dimensional electron gases (2DEG in LaAlO3/SrTiO3 (LAO/STO systems. A strong blue PL emerges in bilayer-2DEGs in LAO/STO/LAO/STO which doesn’t show in LAO/STO. PL band in bilayer-2DEGs includes both nearly temperature independent Auger recombination and temperature dependent free electron trapping while it crossovers from Auger recombination to single carrier trapping in LAO/STO. The PL signal of free electron trapping appears at high temperatures and it is much stronger than Auger recombination in the conducting channel in bilayer 2DEGs. This observation shows that high mobility carriers dominate the carrier dynamics in bilayer-2DEGs in LAO/STO superlattices.

  15. Comparison of TITAN hybrid deterministic transport code and MCNP5 for simulation of SPECT

    International Nuclear Information System (INIS)

    Royston, K.; Haghighat, A.; Yi, C.

    2010-01-01

    Traditionally, Single Photon Emission Computed Tomography (SPECT) simulations use Monte Carlo methods. The hybrid deterministic transport code TITAN has recently been applied to the simulation of a SPECT myocardial perfusion study. The TITAN SPECT simulation uses the discrete ordinates formulation in the phantom region and a simplified ray-tracing formulation outside of the phantom. A SPECT model has been created in the Monte Carlo Neutral particle (MCNP)5 Monte Carlo code for comparison. In MCNP5 the collimator is directly modeled, but TITAN instead simulates the effect of collimator blur using a circular ordinate splitting technique. Projection images created using the TITAN code are compared to results using MCNP5 for three collimator acceptance angles. Normalized projection images for 2.97 deg, 1.42 deg and 0.98 deg collimator acceptance angles had maximum relative differences of 21.3%, 11.9% and 8.3%, respectively. Visually the images are in good agreement. Profiles through the projection images were plotted to find that the TITAN results followed the shape of the MCNP5 results with some differences in magnitude. A timing comparison on 16 processors found that the TITAN code completed the calculation 382 to 2787 times faster than MCNP5. Both codes exhibit good parallel performance. (author)

  16. The Michigan Titan Thermospheric General Circulation Model (TTGCM)

    Science.gov (United States)

    Bell, J. M.; Bougher, S. W.; de Lahaye, V.; Waite, J. H.

    2005-12-01

    The Cassini flybys of Titan since late October, 2004 have provided data critical to better understanding its chemical and thermal structures. With this in mind, a 3-D TGCM of Titan's atmosphere from 600km to the exobase (~1450km) has been developed. This paper presents the first results from the partially operational code. Currently, the TTGCM includes static background chemistry (Lebonnois et al 2001, Vervack et al 2004) coupled with thermal conduction routines. The thermosphere remains dominated by solar EUV forcing and HCN rotational cooling, which is calculated by a full line-by-line radiative transfer routine along the lines of Yelle (1991) and Mueller-Wodarg (2000, 2002). In addition, an approximate treatment of magnetospheric heating is explored. This paper illustrates the model's capabilities as well as some initial results from the Titan Thermospheric General Circulation model that will be compared with both the Cassini INMS data and the model of Mueller-Wodarg (2000,2002).

  17. Growth and characterization of textured YBaCo2O5+δ thin films grown on (001)-SrTiO3 via DC magnetron sputtering

    International Nuclear Information System (INIS)

    Galeano, V.; Arnache, O.; Supelano, I.; Vargas, C.A. Parra; Morán, O.

    2016-01-01

    Thin films of the layered cobaltite YBaCo 2 O 5+δ were successfully grown on (001)-oriented SrTiO 3 single-crystal substrates by means of DC magnetron sputtering. The 112 phase of the compound was stabilized by choosing an adequate Co reactant and through careful thermal treatment of the target. The results demonstrate the strong influence of these variables on the final phase of the compound. A substrate temperature of 1053 K and an oxygen pressure of 300 Pa seemed to be appropriate growing conditions for depositing (00ℓ)-textured YBaCo 2 O 5+δ thin films onto the chosen substrate. In like fashion to the polycrystalline YBaCo 2 O 5+δ , the films showed a clear sequence of antiferromagnetic–ferromagnetic–paramagnetic transitions within a narrow temperature range. Well-defined hysteresis loops were observed at temperatures as high as 270 K, which supports the existence of a FM order in the films. In turn, the dependence of the resistivity on the temperature shows a semiconductor-like behavior, without any distinguishable structure, within the temperature range measured (50–350 K). The analysis of the experimental data showed that the transport mechanism in the films is well described by using the Mott variable range hopping (VRH) conduction model. - Highlights: • YBaCo 2 O 5+δ thin films are grown on SrTiO 3 substrates. • Strong (00ℓ) reflections are observed in the X-ray diffraction pattern. • A clear sequence of magnetic transitions is observed. • Semiconducting-like behavior is verified.

  18. Titan's plasma environment: 3D hybrid simulation and comparison with observations

    Science.gov (United States)

    Lipatov, A. S.; Sittler, E. C.; Hartle, R. E.

    2007-12-01

    A multiscale combined (fluid--kinetic) numerical method allows us to use more realistic plasma models at Titan. This method takes into account charge-exchange and photoionization processes. We study the Titan's plasma environment in case of high, intermediate and low exosphere density in Chamberlain models. The background ions H+, O+ and pickup ions H2+, CH4+ and N2+ are described in a kinetic approximation, where the electrons are approximated as a fluid. We also include an immobile ionosphere at the height 1300km. In this report we consider the multiscale spatial structure for plasma and electromagnetic field, and the velocity distribution of ions that results from the coupling between background ions and pickup ions. Special attention will be paid for the comparisons our numerical results with Voyager and Cassini observations (see e.g. [Sittler, Hartle, et al., 2005; Hartle, Sittler et al., 2006]). We shall estimate of mass loading rate for Ta, energy input to upper atmosphere from ambient +pickup ions, and the T9 encounter with two crossings. \

  19. Domain structure and magnetic properties of epitaxial SrRuO sub 3 films grown on SrTiO sub 3 (100) substrates by ion beam sputtering

    CERN Document Server

    Oh, S H

    2000-01-01

    The domain structure of epitaxial SrRuO sub 3 thin films grown on SrTiO sub 3 (100) substrates by using ion beam sputtering has been investigated with transmission electron microscopy (TEM) and X-ray diffraction (XRD). The SrRuO sub 3 films grown in the present study revealed a unique cube-on-cube epitaxial relationship, i.e., (100) sub S sub R sub O ll (100) sub S sub T sub O , [010] sub S sub R sub O ll [101] sub S sub T sub O , prevailing with a cubic single-domain structure. The cubic SrRuO sub 3 thin films that were inherently with free from RuO sub 6 octahedron tilting exhibited higher resistivity with suppressed magnetic properties. The Curie temperature of the thin films was suppressed by 60 K from 160 K for the bulk specimen, and the saturation magnetic moment was reduced by a significant amount. The tetragonal distortion of the SrRuO sub 3 thin films due to coherent growth with the substrate seemed to result in a strong magnetic anisotropy.

  20. Contribution of the irreversible displacement of domain walls to the piezoelectric effect in barium titanate and lead zirconate titanate ceramics

    CERN Document Server

    Damjanovic, D

    1997-01-01

    The contribution from the irreversible displacement of non-180 deg domain walls to the direct longitudinal piezoelectric d sub 3 sub 3 coefficient of BaTiO sub 3 and Pb(Zr, Ti)O sub 3 ceramics was determined quantitatively by using the Rayleigh law. Effects of the crystal structure and microstructure of the ceramics as well as the external d.c. pressure on the domain wall contribution to d sub 3 sub 3 were examined. In barium titanate, this domain wall contribution is large (up to 35% of the total d sub 3 sub 3 , under the experimental conditions used) and dependent on the external d.c. pressure in coarse grained ceramics, and much smaller and independent of the external d.c. pressure in fine-grained samples. The presence of internal stresses in fine-grained ceramics could account for the observed behaviour. The analysis shows that the domain-wall contribution to the d sub 3 sub 3 in lead zirconate titanate ceramics is large in compositions close to the morphotropic phase boundary that contain a mixture of te...

  1. Effect of mechanical milling on barium titanate (BaTiO3) perovskite

    Science.gov (United States)

    Singh, Rajan Kumar; Sanodia, Sagar; Jain, Neha; Kumar, Ranveer

    2018-05-01

    Commercial Barium Titanate BaTiO3 (BT) is milled by planetary ball mill in acetone medium using stainless steel bowl & ball for different hours. BT is an important perovskite oxide with structure ABO3. BT has applications in electro-optic devices, energy storing devices such as photovoltaic cells, thermistors, multiceramic capacitors & DRAMs etc. BT is non-toxic & environment friendly ceramic with high dielectric and piezoelectric property so it can be used as the substitute of PZT & PbTiO3. Here, we have investigated the effect of milling time and temperature on particle size and phase transition of BT powder. We used use Raman spectroscopy for studying the spectra of BT; XRD is used for structural study. Intensity (height) of Raman spectra and XRD spectra continuously decrease with increasing the milling hours and width if these spectra increases which indicates, decrease in BT size.

  2. The spread of KPC-producing Enterobacteriaceae in Spain: WGS analysis of the emerging high-risk clones of Klebsiella pneumoniae ST11/KPC-2, ST101/KPC-2 and ST512/KPC-3.

    Science.gov (United States)

    Oteo, Jesús; Pérez-Vázquez, María; Bautista, Verónica; Ortega, Adriana; Zamarrón, Pilar; Saez, David; Fernández-Romero, Sara; Lara, Noelia; Ramiro, Raquel; Aracil, Belén; Campos, José

    2016-12-01

    We analysed the microbiological traits and population structure of KPC-producing Enterobacteriaceae isolates collected in Spain between 2012 and 2014. We also performed a comparative WGS analysis of the three major KPC-producing Klebsiella pneumoniae clones detected. Carbapenemase and ESBL genes were sequenced. The Institut Pasteur MLST scheme was used. WGS data were used to construct phylogenetic trees, to identify the determinants of resistance and to de novo assemble the genome of one representative isolate of each of the three major K. pneumoniae clones. Of the 2443 carbapenemase-producing Enterobacteriaceae isolates identified during the study period, 111 (4.5%) produced KPC. Of these, 81 (73.0%) were K. pneumoniae and 13 (11.7%) were Enterobacter cloacae. Three major epidemic clones of K. pneumoniae were identified: ST11/KPC-2, ST101/KPC-2 and ST512/KPC-3. ST11/KPC-2 differed from ST101/KPC-2 and ST512/KPC-3 by 27 819 and 6924 SNPs, respectively. ST101/KPC-2 differed from ST512/KPC-3 by 28 345 SNPs. Nine acquired resistance genes were found in ST11/KPC-2, 11 in ST512/KPC-3 and 13 in ST101/KPC-2. ST101/KPC-2 had the highest number of virulence genes (20). An 11 bp deletion at the end of the mgrB sequence was the cause of colistin resistance in ST512/KPC-3. KPC-producing Enterobacteriaceae are increasing in Spain. Most KPC-producing K. pneumoniae isolates belonged to only five clones: ST11 and ST512 caused interregional spread, ST101 caused regional spread and ST1961 and ST678 produced independent hospital outbreaks. ST101/KPC-2 had the highest number of resistance and virulence genes. ST101/KPC-2 and ST512/KPC-3 were recently implicated in the spread of KPC in Italy. © The Author 2016. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

  3. Titan Orbiter Aerorover Mission with Enceladus Science (TOAMES)

    Science.gov (United States)

    Sittler, E.; Cooper, J.; Mahaffy, P.; Fairbrother, D.; de Pater, I.; Schulze-Makuch, D.; Pitman, J.

    2007-08-01

    same time made us aware of how little we understand about these bodies. For example, the source, and/or recycling mechanism, of methane in Titan's atmosphere is still puzzling. Indeed, river beds (mostly dry) and lakes have been spotted, and occasional clouds have been seen, but the physics to explain the observations is still mostly lacking, since our "image" of Titan is still sketchy and quite incomplete. Enceladus, only 500 km in extent, is even more puzzling, with its fiery plumes of vapor, dust and ice emanating from its south polar region, "feeding" Saturn's E ring. Long term variability of magnetospheric plasma, neutral gas, E-ring ice grain density, radio emissions, and corotation of Saturn's planetary magnetic field in response to Enceladus plume activity are of great interest for Saturn system science. Both Titan and Enceladus are bodies of considerable astrobiological interest in view of high organic abundances at Titan and potential subsurface liquid water at Enceladus. We propose to develop a new mission to Titan and Enceladus, the Titan Orbiter Aerorover Mission with Enceladus Science (TOAMES), to address these questions using novel new technologies. TOAMES is a multi-faceted mission that starts with orbit insertion around Saturn using aerobraking with Titan's extended atmosphere. We then have an orbital tour around Saturn (for 1-2 years) and close encounters with Enceladus, before it goes into orbit around Titan (via aerocapture). During the early reconnaissance phase around Titan, perhaps 6 months long, the orbiter will use altimetry, radio science and remote sensing instruments to measure Titan's global topography, subsurface structure and atmospheric winds. This information will be used to determine where and when to release the Aerorover, so that it can navigate safely around Titan and identify prime sites for surface sampling and analysis. In situ instruments will sample the upper atmosphere which may provide the seed population for the complex

  4. Spacecraft Exploration of Titan and Enceladus

    Science.gov (United States)

    Matson, D.; Coustenis, A.; Lunine, J. I.; Lebreton, J.; Reh, K.; Beauchamp, P.; Erd, C.

    2009-12-01

    The future exploration of Titan and Enceladus is very important for planetary science. The study titled Titan Saturn System Mission (TSSM) led to an announcement in which ESA and NASA prioritized future OPF missions, stating that TSSM is planned after EJSM (for details see http://www.lpi.usra.edu/opag/). The TSSM concept consists of an Orbiter that would carry two in situ elements: the Titan Montgolfiere hot air balloon and the Titan Lake Lander. This mission could launch in the 2023-2025 timeframe on a trajectory to arrive ~9 years later and begin a 4-year mission in the Saturnian system. At an appropriate time after arrival at Saturn, the montgolfiere would be delivered to Titan to begin its mission of airborne, scientific observations of Titan from an altitude of about 10 km above the surface. The montgolfiere would have a Multi-Mission Radioisotope Thermoelectric Generator (MMRTG) power system whose waste heat would warm the gas in the balloon, providing buoyancy. It would be designed to survive at least 6-12 months in Titan’s atmosphere. With the predicted winds and weather, it should be possible to circumnavigate the globe! Later, on a subsequent fly-by, the TSSM orbiter would send the Lake Lander to Titan. It would descend through the atmosphere making scientific measurements, much like Huygens did, and then land and float on one of Titan’s seas. This would be its oceanographic phase of making a physical and chemical assessment of the sea. The Lake Lander would operate for 8-10 hours until its batteries become depleted. Following the delivery of the in situ elements, the TSSM orbiter would then explore the Saturn system for two years on a tour that includes in situ sampling of Enceladus’ plumes as well as flybys of Titan. After the Saturn tour, the TSSM orbiter would go into orbit around Titan and carry out a global survey phase. Synergistic observations would be carried out by the TSSM orbiter and the in situ elements. The scientific requirements for

  5. Observations of CO in Titan's Atmosphere Using ALMA

    Science.gov (United States)

    Serigano, Joseph; Nixon, Conor A.; Cordiner, Martin; Irwin, Patrick G. J.; Teanby, Nicholas; Charnley, Steven B.; Lindberg, Johan E.; Remijan, Anthony J.

    2015-11-01

    The advent of the Atacama Large Millimeter/submillimeter Array (ALMA) has provided a powerful facility for probing the atmospheres of solar system targets at long wavelengths (84-720 GHz) where the rotational lines of small, polar molecules are prominent. In the dense, nitrogen-dominated atmosphere of Titan, photodissociation of molecular nitrogen and methane leads to a wealth of complex hydrocarbons and nitriles in small abundances. Past millimeter/submillimeter observations, including ground-based observations as well as those by the Composite Infrared Spectrometer (CIRS) aboard the Cassini spacecraft, have proven the significance of this wavelength region for the derivation of vertical mixing profiles, latitudinal and seasonal variations, and molecular detections. Previous ALMA studies of Titan have presented mapping and vertical column densities of hydrogen isocyanide (HNC) and cyanoacetylene (HC3N) (Cordiner et al. 2014) as well as the first spectroscopic detection of ethyl cyanide (C2H5CN) in Titan’s atmosphere (Cordiner et al. 2015).Here, we report several submillimetric observations of carbon monoxide (CO) and its isotopologues 13CO, C18O, and C17O in Titan’s atmosphere obtained with flux calibration data from the ALMA Science Archive. We employ NEMESIS, a line-by-line radiative transfer code, to determine the stratospheric abundances of these molecules. The abundance of CO in Titan's atmosphere is determined to be approximately 50±1 ppm, constant with altitude, and isotopic ratios are determined to be approximately 12C/13C = 90, 16O/18O = 470, and 16O/17O = 2800. This report presents the first spectroscopic detection of C17O in the outer solar system, detected at >11σ confidence. This talk will focus on isotopic ratios in CO in Titan's atmosphere and will compare our results to previously measured values for Titan and other bodies in the Solar System. General implications for the history of Titan from measurements of CO and its isotopologues will be

  6. Single-crystal SrTiO3 fiber grown by laser heated pedestal growth method: influence of ceramic feed rod preparation in fiber quality

    Directory of Open Access Journals (Sweden)

    D. Reyes Ardila

    1998-10-01

    Full Text Available The rapidly spreading use of optical fiber as a transmission medium has created an interest in fiber-compatible optical devices and methods for growing them, such as the Laser Heated Pedestal Growth (LHPG. This paper reports on the influence of the ceramic feed rod treatment on fiber quality and optimization of ceramic pedestal processing that allows improvements to be made on the final quality in a simple manner. Using the LHPG technique, transparent crack-free colorless single crystal fibers of SrTiO3 (0.50 mm in diameter and 30-40 mm in length were grown directly from green-body feed rods, without using external oxygen atmosphere.

  7. A new ion exchange behavior of protonated titanate nanotubes after deprotonation and the study on their morphology and optical properties

    International Nuclear Information System (INIS)

    Zhang Huibin; Cao Lixin; Liu Wei; Su Ge

    2012-01-01

    Graphical abstract: The morphological transformation of protonated titanate nanotubes under alkali solution before ion exchange (a) and after ion exchange (b). Highlights: ► A novel ion exchange behavior of protonated titanate nanotubes after deprotonation. ► The exchangeability of protonated titanate nanotubes are not as inert as past reported. ► The tube walls of H 2 Ti 3 O 7 nanotubes is observed to get loosened after ion exchange. ► The paper proves a new and easy way to modify protonated titanate nanotubes. - Abstract: After the deprotonation of protonated titanate nanotubes (H 2 Ti 3 O 7 ), we observed a novel ion exchange behavior on them. In the past literatures, protonated titanate nanotubes prepared via hydrothermal method have been reported with a poor exchangeability which may due to the chemical bonding of interlayer protons to nearby oxygen atoms. However, in this experiment under alkali environment (pH > 10), protonated titanate nanotubes exhibited a vast ion exchange capacity toward [Co(NH 3 ) 6 ] 2+ . This interesting phenomenon is contrary to the past reports which found protonated titanate nanotubes hardly could be ionexchanged by objective cations. This paper proves the deprotonation process on H 2 Ti 3 O 7 nanotubes sufficiently facilitates the diffusion of metal complex cations into protonated titanate nanotubes and significantly changes their ion exchange capacity. As a consequence of cabalt intercalting via ion exchange, the tube wall of H 2 Ti 3 O 7 nanotubes is observed to get loosened. Additionally, the exciton concentrations corresponding to the nanotube surface states are discussed in the paper.

  8. Scandium doped Strontium Titanate Ceramics: Structure, Microstructure, and Dielectric Properties

    Directory of Open Access Journals (Sweden)

    Tkach, Alexander

    2008-08-01

    Full Text Available Sc-doped strontium titanate (ST ceramics were synthesised by solid state reaction, according to the composition Sr1-1.5xScxTiO3 with x = 0-0.01. Structural properties and microstructure development was examined by XRD and SEM. The dielectric properties were evaluated as a function of the temperature and frequency in the radio frequency range. Lattice parameter, density and grain size, were found to decrease slightly with increasing Sc content. The dielectric permittivity and losses decrease also. Sc-doping has only a weak effect on the quantum paraelectric behaviour of ST and no dielectric anomaly was observed, what is probably related to the limited solubility of Sc on the Sr site of the perovskite lattice of ST.

    Se sintetizaron materiales cerámicos de titanato de estroncio dopado con escandio mediante reacción en estado sólido De acuerdo a la composición Sr1-1.5xScxTiO3 con x= 0-0.1. Las propiedades estructurales y el desarrollo microestructural se estudiaron mediante XRD y SEM. La propiedades dieléctricas se estudiaron como función de la temperatura y de la frecuencia en el rango de la frecuencias de radio. Se observó que los parámetros de red, la densidad y el tamaño del grano disminuyen ligeramente con el contenido en Sc. La permitividad dieléctrica y las perdidas también disminuyen. El dopado con Sc tiene un efecto muy ligero sobre el comportamiento paraeléctrico cuántico del titanato de estroncio y no se observó anomalías dioeléctricas , lo que está probablemente relacionado con la baja solubilidad del Sc en posiciones del Sr en la estructura tipo perovskita del titanato de estroncio.

  9. Exploring inner structure of Titan's dunes from Cassini Radar observations

    Science.gov (United States)

    Sharma, P.; Heggy, E.; Farr, T. G.

    2013-12-01

    Linear dunes discovered in the equatorial regions of Titan by the Cassini-Huygens mission are morphologically very similar to many terrestrial linear dune fields. These features have been compared with terrestrial longitudinal dune fields like the ones in Namib desert in western Africa. This comparison is based on the overall parallel orientation of Titan's dunes to the predominant wind direction on Titan, their superposition on other geomorphological features and the way they wrap around topographic obstacles. Studying the internal layering of dunes has strong implications in understanding the hypothesis for their origin and evolution. In Titan's case, although the morphology of the dunes has been studied from Cassini Synthetic Aperture Radar (SAR) images, it has not been possible to investigate their internal structure in detail as of yet. Since no radar sounding data is available for studying Titan's subsurface yet, we have developed another technique to examine the inner layering of the dunes. In this study, we utilize multiple complementary radar datasets, including radar imaging data for Titan's and Earth's dunes and Ground Penetrating Radar (GPR)/radar sounding data for terrestrial dunes. Based on dielectric mixing models, we suggest that the Cassini Ku-band microwaves should be able to penetrate up to ~ 3 m through Titan's dunes, indicating that the returned radar backscatter signal would include contributions from both surface and shallow subsurface echoes. This implies that the shallow subsurface properties can be retrieved from the observed radar backscatter (σ0). In our analysis, the variation of the radar backscatter as a function of dune height is used to provide an insight into the layering in Titan's dunes. We compare the variation of radar backscatter with elevation over individual dunes on Titan and analogous terrestrial dunes in three sites (Great Sand Sea, Siwa dunes and Qattaniya dunes) in the Egyptian Sahara. We observe a strong, positive

  10. Investigations of the Structure of Titanate Nanoscrolls

    International Nuclear Information System (INIS)

    Sheppard, D.A.; Buckley, C.E.

    2005-01-01

    Full text: Nanosized materials have attracted much research lately due to their unique properties and their potential application in nanoelectronic and optoelectronic devices. Nanostructured materials have also sparked interest as possible hydrogen storage candidates. Research at Curtin University has shown titanate nanoscrolls to absorb modest amounts of hydrogen at low temperatures. Whether or not this capacity can be improved will be dependent on a thorough understanding of the structure and the way it interacts with hydrogen. Titanate nanoscrolls are made via a soft chemical process that involves ageing TiO 2 powder in a concentrated NaOH solution. The resultant nanoscrolls, once filtered and washed, are typically 8-10 nm in diameter and hundreds of nanometers long. The walls consist of 3-5 layers and the diameter of the hollow centre is typically 5 nm. A number of different structures have been assigned to nanoscrolls produced via the soft chemical process. These include anatase, H 2 Ti 3 O 7 , lepidocrocite-type structure and H 2 Ti 4 O 9 .H 2 O. Many of these structures are similar, consisting of titanate type layers, and qualitatively reproduce the X-ray diffraction data. However, preliminary data suggests that these structures are inconsistent with neutron diffraction data. Here we attempt a more quantitative analysis of the structure than those published previously using neutron and X-ray diffraction. (authors)

  11. Spin injection and detection in lanthanum- and niobium-doped SrTiO3 using the Hanle technique

    KAUST Repository

    Han, Wei; Jiang, Xin; Kajdos, Adam; Yang, See-Hun; Stemmer, Susanne; Parkin, Stuart S. P.

    2013-01-01

    as the temperature is decreased to low temperatures. However, the mobility of the strontium titanate has a strong temperature dependence. This behaviour and the carrier doping dependence of the spin lifetime suggest that the spin lifetime is limited by spin

  12. Study of thermal stability of (3-aminopropyl)trimethoxy silane-grafted titanate nanotubes for application as nanofillers in polymers

    International Nuclear Information System (INIS)

    Plodinec, Milivoj; Gajović, Andreja; Iveković, Damir; Tomašić, Nenad; Zimmermann, Boris; Macan, Jelena; Haramina, Tatjana; Su, D S; Willinger, Marc

    2014-01-01

    Protonated titanate nanotubes (TiNT-H) were surface-modified with (3-aminopropyl)trimethoxy silane (APTMS) by a novel method suitable for the syntheses of large amounts of materials at a low cost. The usage of prepared nanotubes for polymer reinforcement was studied. Since the thermal stability of the nanofiller was important to preserve its functional properties, its stability was studied by in situ high-temperature measurements. The most thermally stable nanotubes were silanized for 20 min and used for the preparation of epoxy-based nanocomposites. The nanofiller formed smaller (a few hundred nm) and larger (a few μm) aggregates in the polymer matrix, and the amount of aggregates increased as the nanofiller content increased. The APTMS-modified titanate nanotubes bonded well with the epoxy matrix since amine groups on the TiNT’s surface can react with an epoxy group to form covalent bonds between the matrix and the nanofiller. A very small addition (0.19–1.52 wt%) of the nanotubes significantly increased the glass transition temperature and the modulus in the rubbery state of the epoxy-based polymer. Smaller nanofiller content leads to a larger increase in these parameters and therefore better dynamic mechanical properties due to the smaller amount of large aggregates. APTMS-modified titanate nanotubes have proven to be a promising nanofiller in epoxy-based nanocomposites. (paper)

  13. Study of thermal stability of (3-aminopropyl)trimethoxy silane-grafted titanate nanotubes for application as nanofillers in polymers.

    Science.gov (United States)

    Plodinec, Milivoj; Gajović, Andreja; Iveković, Damir; Tomašić, Nenad; Zimmermann, Boris; Macan, Jelena; Haramina, Tatjana; Su, D S; Willinger, Marc

    2014-10-31

    Protonated titanate nanotubes (TiNT-H) were surface-modified with (3-aminopropyl)trimethoxy silane (APTMS) by a novel method suitable for the syntheses of large amounts of materials at a low cost. The usage of prepared nanotubes for polymer reinforcement was studied. Since the thermal stability of the nanofiller was important to preserve its functional properties, its stability was studied by in situ high-temperature measurements. The most thermally stable nanotubes were silanized for 20 min and used for the preparation of epoxy-based nanocomposites. The nanofiller formed smaller (a few hundred nm) and larger (a few μm) aggregates in the polymer matrix, and the amount of aggregates increased as the nanofiller content increased. The APTMS-modified titanate nanotubes bonded well with the epoxy matrix since amine groups on the TiNT's surface can react with an epoxy group to form covalent bonds between the matrix and the nanofiller. A very small addition (0.19-1.52 wt%) of the nanotubes significantly increased the glass transition temperature and the modulus in the rubbery state of the epoxy-based polymer. Smaller nanofiller content leads to a larger increase in these parameters and therefore better dynamic mechanical properties due to the smaller amount of large aggregates. APTMS-modified titanate nanotubes have proven to be a promising nanofiller in epoxy-based nanocomposites.

  14. Determination of vanadium in titanate-based ferroelectrics by INAA with discriminating gamma-ray spectrometry

    Czech Academy of Sciences Publication Activity Database

    Kameník, Jan; Dragounová, K.; Kučera, Jan; Bryknar, Z.; Trepakov, Vladimír; Strunga, Vladimír

    2017-01-01

    Roč. 311, č. 2 (2017), s. 1333-1338 ISSN 0236-5731. [1st International Conference on Radioanalytical and Nuclear chemistry (RANC). Budapest, 10.04.2016-15.04.2016] R&D Projects: GA ČR(CZ) GBP108/12/G108; GA MŠk LM2015056 Institutional support: RVO:68378271 ; RVO:61389005 Keywords : Titanate-based ferroelectrics * Vanadium * INAA * discriminating gamma-ray spectrometry Subject RIV: CB - Analytical Chemistry, Separation; BM - Solid Matter Physics ; Magnetism (FZU-D) OBOR OECD: Analytical chemistry; Condensed matter physics (including formerly solid state physics, supercond.) (FZU-D) Impact factor: 1.282, year: 2016

  15. Strontium titanate thin film deposition - structural and electronical characterization

    Energy Technology Data Exchange (ETDEWEB)

    Hanzig, Florian; Hanzig, Juliane; Stoecker, Hartmut; Mehner, Erik; Abendroth, Barbara; Meyer, Dirk C. [TU Bergakademie Freiberg, Institut fuer Experimentelle Physik (Germany); Franke, Michael [TU Bergakademie Freiberg, Institut fuer Elektronik- und Sensormaterialien (Germany)

    2012-07-01

    Strontium titanate is on the one hand a widely-used model oxide for solids which crystallize in perovskite type of structure. On the other hand, with its large band-gap energy and its mixed ionic and electronic conductivity, SrTiO{sub 3} is a promising isolating material in metal-insulator-metal (MIM) structures for resistive switching memory cells. Here, we used physical vapour deposition methods (e. g. electron-beam and sputtering) to produce strontium titanate layers. Sample thicknesses were probed with X-ray reflectometry (XRR) and spectroscopic ellipsometry (SE). Additionally, layer densities and dielectric functions were quantified with XRR and SE, respectively. Using infrared spectroscopy free electron concentrations were obtained. Phase and element composition analysis was carried out with grazing incidence X-ray diffraction and X-ray photoelectron spectroscopy. Subsequent temperature treatment of samples lead to crystallization of the initially amorphous strontium titanate.

  16. Titan Montgolfiere Terrestrial Test Bed, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — With the Titan Saturn System Mission, NASA is proposing to send a Montgolfiere balloon to probe the atmosphere of Titan. To better plan this mission and create a...

  17. Titan Montgolfiere Terrestrial Test Bed, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — With the Titan Saturn System Mission, NASA is proposing to send a Montgolfiere balloon to probe the atmosphere of Titan. In order to better plan this mission and...

  18. AVIATR—Aerial Vehicle for In-situ and Airborne Titan Reconnaissance

    DEFF Research Database (Denmark)

    Barnes, Jason W.; Lemke, Lawrence; Foch, Rick

    2012-01-01

    We describe a mission concept for a stand-alone Titan airplane mission: Aerial Vehicle for In-situ and Airborne Titan Reconnaissance (AVIATR). With independent delivery and direct-to-Earth communications, AVIATR could contribute to Titan science either alone or as part of a sustained Titan...... Exploration Program. As a focused mission, AVIATR as we have envisioned it would concentrate on the science that an airplane can do best: exploration of Titan's global diversity. We focus on surface geology/hydrology and lower-atmospheric structure and dynamics. With a carefully chosen set of seven...... of a Space Vehicle (SV) for cruise, an Entry Vehicle (EV) for entry and descent, and the Air Vehicle (AV) to fly in Titan's atmosphere. Using an Earth-Jupiter gravity assist trajectory delivers the spacecraft to Titan in 7.5 years, after which the AVIATR AV would operate for a 1-Earth-year nominal mission...

  19. HST observations of the limb polarization of Titan

    Science.gov (United States)

    Bazzon, A.; Schmid, H. M.; Buenzli, E.

    2014-12-01

    Context. Titan is an excellent test case for detailed studies of the scattering polarization from thick hazy atmospheres. Accurate scattering and polarization parameters have been provided by the in situ measurements of the Cassini-Huygens landing probe. For Earth-bound observations Titan can only be observed at a backscattering situation, where the disk-integrated polarization is close to zero. However, with resolved imaging polarimetry a second order polarization signal along the entire limb of Titan can be measured. Aims: We present the first limb polarization measurements of Titan, which are compared as a test to our limb polarization models. Methods: Previously unpublished imaging polarimetry from the HST archive is presented, which resolves the disk of Titan. We determine flux-weighted averages of the limb polarization and radial limb polarization profiles, and investigate the degradation and cancelation effects in the polarization signal due to the limited spatial resolution of our observations. Taking this into account we derive corrected values for the limb polarization in Titan. The results are compared with limb polarization models, using atmosphere and haze scattering parameters from the literature. Results: In the wavelength bands between 250 nm and 2 μm a strong limb polarization of about 2 - 7% is detected with a position angle perpendicular to the limb. The fractional polarization is highest around 1 μm. As a first approximation, the polarization seems to be equally strong along the entire limb. The comparison of our data with model calculations and the literature shows that the detected polarization is compatible with expectations from previous polarimetric observations taken with Voyager 2, Pioneer 11, and the Huygens probe. Conclusions: Our results indicate that ground-based monitoring measurements of the limb-polarization of Titan could be useful for investigating local haze properties and the impact of short-term and seasonal variations of

  20. Molecular weight growth in Titan's atmosphere: branching pathways for the reaction of 1-propynyl radical (H3CC≡C˙) with small alkenes and alkynes.

    Science.gov (United States)

    Kirk, Benjamin B; Savee, John D; Trevitt, Adam J; Osborn, David L; Wilson, Kevin R

    2015-08-28

    The reaction of small hydrocarbon radicals (i.e.˙CN, ˙C2H) with trace alkenes and alkynes is believed to play an important role in molecular weight growth and ultimately the formation of Titan's characteristic haze. Current photochemical models of Titan's atmosphere largely assume hydrogen atom abstraction or unimolecular hydrogen elimination reactions dominate the mechanism, in contrast to recent experiments that reveal significant alkyl radical loss pathways during reaction of ethynyl radical (˙C2H) with alkenes and alkynes. In this study, the trend is explored for the case of a larger ethynyl radical analogue, the 1-propynyl radical (H3CC[triple bond, length as m-dash]C˙), a likely product from the high-energy photolysis of propyne in Titan's atmosphere. Using synchrotron vacuum ultraviolet photoionization mass spectrometry, product branching ratios are measured for the reactions of 1-propynyl radical with a suite of small alkenes (ethylene and propene) and alkynes (acetylene and d4-propyne) at 4 Torr and 300 K. Reactions of 1-propynyl radical with acetylene and ethylene form single products, identified as penta-1,3-diyne and pent-1-en-3-yne, respectively. These products form by hydrogen atom loss from the radical-adduct intermediates. The reactions of 1-propynyl radical with d4-propyne and propene form products from both hydrogen atom and methyl loss, (-H = 27%, -CH3 = 73%) and (-H = 14%, -CH3 = 86%), respectively. Together, these results indicate that reactions of ethynyl radical analogues with alkenes and alkynes form significant quantities of products by alkyl loss channels, suggesting that current photochemical models of Titan over predict both hydrogen atom production as well as the efficiency of molecular weight growth in these reactions.

  1. Experimental basis for a Titan probe organic analysis

    International Nuclear Information System (INIS)

    Mckay, C.P.; Scattergood, T.W.; Borucki, W.J.; Kasting, J.F.; Miller, S.L.; California Univ., San Diego, La Jolla)

    1986-01-01

    The recent Voyager flyby of Titan produced evidence for at least nine organic compounds in that atmosphere that are heavier than methane. Several models of Titan's atmosphere, as well as laboratory simulations, suggest the presence of organics considerably more complex that those observed. To ensure that the in situ measurements are definitive with respect to Titan's atmosphere, experiment concepts, and the related instrumentation, must be carefully developed specifically for such a mission. To this end, the possible composition of the environment to be analyzed must be bracketed and model samples must be provided for instrumentation development studies. Laboratory studies to define the optimum flight experiment and sampling strategy for a Titan entry probe are currently being conducted. Titan mixtures are being subjected to a variety of energy sources including high voltage electron from a DC discharge, high current electric shock, and laser detonation. Gaseous and solid products are produced which are then analyzed. Samples from these experiements are also provided to candidate flight experiments as models for instrument development studies. Preliminary results show that existing theoretical models for chemistry in Titan's atmosphere cannot adequetely explain the presence and abundance of all trace gases observed in these experiments

  2. Overview of the TITAN-II reversed-field pinch aqueous fusion power core design

    Energy Technology Data Exchange (ETDEWEB)

    Wong, C.P.C.; Creedon, R.L.; Cheng, E.T. (General Atomic Co., San Diego, CA (USA)); Grotz, S.P.; Sharafat, S.; Cooke, P.I.H. (California Univ., Los Angeles (USA). Dept. of Mechanical, Aerospace and Nuclear Engineering; California Univ., Los Angeles, CA (USA). Inst. for Plasma and Fusion Research); TITAN Research Group

    1989-04-01

    TITAN-II is a compact, high-power-density Reversed-Field Pinch fusion power reactor design based on the aqueous lithium solution fusion power core concept. The selected breeding and structural materials are LiNO/sub 3/ and 9-C low activation ferritic steel, respectively. TITAN-II is a viable alternative to the TITAN-I lithium self-cooled design for the Reversed-Field Pinch reactor to operate at a neutron wall loading of 18 MW/m/sup 2/. Submerging the complete fusion power core and the primary loop in a large pool of cool water will minimize the probability of radioactivity release. Since the protection of the large pool integrity is the only requirement for the protection of the public, TITAN-II is a level 2 of passive safety assurance design. (orig.).

  3. EPR study of charge compensation of chromium centers in the strontium titanate crystal

    Czech Academy of Sciences Publication Activity Database

    Badalyan, A. G.; Azamat, Dmitry; Babunts, R.A.; Neverova, E.V.; Dejneka, Alexandr; Trepakov, Vladimír; Jastrabík, Lubomír

    2013-01-01

    Roč. 55, č. 7 (2013), 1454-1458 ISSN 1063-7834 R&D Projects: GA ČR GAP108/12/1941 Institutional support: RVO:68378271 Keywords : EPR spectroscopy * SrTiO3:Cr crystal * chromium centers Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.782, year: 2013

  4. Microwave-hydrothermal synthesis of barium strontium titanate nanoparticles

    International Nuclear Information System (INIS)

    Simoes, A.Z.; Moura, F.; Onofre, T.B.; Ramirez, M.A.; Varela, J.A.; Longo, E.

    2010-01-01

    Research highlights: → Barium strontium titanate nanoparticles were obtained by the Hydrothemal microwave technique (HTMW) → This is a genuine technique to obtain nanoparticles at low temperature and short times → Barium strontium titanate free of carbonates with tetragonal structure was grown at 130 o C. - Abstract: Hydrothermal-microwave method (HTMW) was used to synthesize crystalline barium strontium titanate (Ba 0.8 Sr 0.2 TiO 3 ) nanoparticles (BST) in the temperature range of 100-130 o C. The crystallization of BST with tetragonal structure was reached at all the synthesis temperatures along with the formation of BaCO 3 as a minor impurity at lower syntheses temperatures. Typical FT-IR spectra for tetragonal (BST) nanoparticles presented well defined bands, indicating a substantial short-range order in the system. TG-DTA analyses confirmed the presence of lattice OH- groups, commonly found in materials obtained by HTMW process. FE/SEM revealed that lower syntheses temperatures led to a morphology that consisted of uniform grains while higher syntheses temperature consisted of big grains isolated and embedded in a matrix of small grains. TEM has shown BST nanoparticles with diameters between 40 and 80 nm. These results show that the HTMW synthesis route is rapid, cost effective, and could serve as an alternative to obtain BST nanoparticles.

  5. Titan's organic chemistry: Results of simulation experiments

    Science.gov (United States)

    Sagan, Carl; Thompson, W. Reid; Khare, Bishun N.

    1992-01-01

    Recent low pressure continuous low plasma discharge simulations of the auroral electron driven organic chemistry in Titan's mesosphere are reviewed. These simulations yielded results in good accord with Voyager observations of gas phase organic species. Optical constants of the brownish solid tholins produced in similar experiments are in good accord with Voyager observations of the Titan haze. Titan tholins are rich in prebiotic organic constituents; the Huygens entry probe may shed light on some of the processes that led to the origin of life on Earth.

  6. The commercial evolution of the Titan program

    Science.gov (United States)

    Isakowitz, Steven

    1988-07-01

    The present status evaluation of proprietary efforts to turn the once exclusively government-requirements-oriented Titan launch vehicle into a successful commercial competitor is divided into three phases. The first phase notes recent changes in U.S. space transportation policy and the Titan configurations evaluated for commercial feasibility. The second phase is a development history for the current vehicle's marketing organization and the right-to-use agreement for a launch site. Phase three projects the prospective marketing climate for a commercial Titan vehicle and its planned improvements.

  7. Descent imager/spectral radiometer (DISR) instrument aboard the Huygens probe of Titan

    Science.gov (United States)

    Tomasko, Martin G.; Doose, Lyn R.; Smith, Peter H.; Fellows, C.; Rizk, B.; See, C.; Bushroe, M.; McFarlane, E.; Wegryn, E.; Frans, E.; Clark, R.; Prout, M.; Clapp, S.

    1996-10-01

    The Huygen's probe of the atmosphere of Saturn's moon Titan includes one optical instrument sensitive to the wavelengths of solar radiation. The goals of this investigation fall into four broad areas: 1) the measurement of the profile of solar heating to support an improved understanding of the thermal balance of Titan and the role of the greenhouse effect in maintaining Titan's temperature structure; 2) the measurement of the size, vertical distribution, and optical properties of the aerosol and cloud particles in Titan's atmosphere to support studies of the origin, chemistry, life cycles, and role in the radiation balance of Titan played by these particles; 3) the composition of the atmosphere, particularly the vertical profile of the mixing ratio of methane, a condensable constituent in Titan's atmosphere; and 4) the physical state, composition, topography, and physical processes at work in determining the nature of the surface of Titan and its interaction with Titan's atmosphere. In order to accomplish these objectives, the Descent Imager/Spectral Radiometer (DISR) instrument makes extensive use of fiber optics to bring the light from several different sets of foreoptics to a silicon CCD detector, to a pair of InGaAs linear array detectors, and to three silicon photometers. Together these detectors permit DISR to make panoramic images of the clouds and surface of Titan, to measure the spectrum of upward and downward streaming sunlight from 350 to 1700 nm at a resolving power of about 200, to measure the reflection spectrum of >= 3000 locations on the surface, to measure the brightness and polarization of the solar aureole between 4 and 30 degrees from the sun at 500 and 935 nm, to separate the direct and diffuse downward solar flux at each wavelength measured, and to measure the continuous reflection spectrum of the ground between 850 and 1600 nm using an onboard lamp in the last 100 m of the descent.

  8. Preparation and characterization of titanate nanotubes/carbon composites

    International Nuclear Information System (INIS)

    Wang Xiaodong; Pan Hui; Xue Xiaoxiao; Qian Junjie; Yu Laigui; Yang Jianjun; Zhang Zhijun

    2011-01-01

    Highlights: → Titanate nanotubes/carbon composites were synthesized from TiO 2 -carbon composites. → The carbon shell of TiO 2 particles obstructed the reaction between TiO 2 and NaOH. → TEM, XRD, and Raman spectra reveal the formation processes of the TNT/CCs. - Abstract: Titanate nanotubes/carbon composites(TNT/CCs) were synthesized by allowing carbon-coated TiO 2 (CCT) powder to react with a dense aqueous solution of NaOH at 120 deg. C for a proper period of time. As-prepared CCT and TNT/CCs were characterized by means of transmission electron microscopy (TEM), X-ray diffraction (XRD), and Raman spectrometry. The processes for formation of titanate nanotubes/carbon composites were discussed. It was found that the TiO 2 particles in TiO 2 -carbon composite were enwrapped by a fine layer of carbon with a thickness of about 4 nm. This carbon layer functioned to inhibit the transformation from anatase TiO 2 to orthorhombic titanate. As a result, the anatase TiO 2 in CCT was incompletely transformed into orthorhombic titanate nanotubes upon 24 h of reaction in the dense and hot NaOH solution. When the carbon layers were gradually peeled off along with the formation of more orthorhombic titanate nanotubes at extended reaction durations (e.g., 72 h), anatase TiO 2 particles in CCT were completely transformed into orthorhombic titanate nanotubes, yielding TNT/CCs whose morphology was highly dependent on the reaction time and temperature.

  9. Selections from 2017: Discoveries in Titan's Atmosphere

    Science.gov (United States)

    Kohler, Susanna

    2017-12-01

    Editors note:In these last two weeks of 2017, well be looking at a few selections that we havent yet discussed on AAS Nova from among the most-downloaded paperspublished in AAS journals this year. The usual posting schedule will resume in January.Carbon Chain Anions and the Growth of Complex Organic Molecules in Titans IonospherePublished July2017Main takeaway:Graphic depicting some of the chemical reactions taking place in Titans atmosphere, leading to the generation of organic haze particles. [ESA]In a recently published study led by Ravi Desai (University College London), scientists used data from the Cassini mission to identify negatively charged molecules known as carbon chain anions in the atmosphere of Saturns largest moon, Titan.Why its interesting:Carbon chain anions are the building blocks ofmore complex molecules, and Titans thick nitrogen and methane atmosphere mightmimic the atmosphere of earlyEarth. This first unambiguous detection of carbon chain anions in a planet-like atmosphere might therefore teach us about the conditions and chemical reactions that eventually led to the development of life on Earth. And ifwe can use Titan to learn about how complex molecules grow from these anion chains, we may be able to identify auniversal pathway towards the ingredients for life.What weve learned so far:Cassini measured fewer and fewer lower-mass anions the deeper in Titans ionosphere that it looked and at the same time,an increase in the number of precursors to larger aerosol molecules further down. This tradeoff strongly suggests that the anions are indeed involved in building up the more complex molecules, seeding their eventual growth into the complex organic haze of Titans lower atmosphere.CitationR. T. Desai et al 2017 ApJL 844 L18. doi:10.3847/2041-8213/aa7851

  10. Barium zirconate-titanate/barium calcium-titanate ceramics via sol-gel process: novel high-energy-density capacitors

    International Nuclear Information System (INIS)

    Puli, Venkata Sreenivas; Kumar, Ashok; Scott, J F; Katiyar, Ram S; Chrisey, Douglas B; Tomozawa, M

    2011-01-01

    Lead-free barium zirconate-titanate/barium calcium-titanate, [(BaZr 0.2 Ti 0.80 )O 3 ] 1-x -[(Ba 0.70 Ca 0.30 )TiO 3 ] x (x = 0.10, 0.15, 0.20) (BZT-BCT) ceramics with high dielectric constant, low dielectric loss and moderate electric breakdown field were prepared by the sol-gel synthesis technique. X-ray diffraction patterns revealed tetragonal crystal structure and this was further confirmed by Raman spectra. Well-behaved ferroelectric hysteresis loops and moderate polarizations (spontaneous polarization, P s ∼ 3-6 μC cm -2 ) were obtained in these BZT-BCT ceramics. Frequency-dependent dielectric spectra confirmed that ferroelectric diffuse phase transition (DPT) exists near room temperature. Scanning electron microscope images revealed monolithic grain growth in samples sintered at 1280 deg. C. 1000/ε versus (T) plots revealed ferroelectric DPT behaviour with estimated γ values of ∼1.52, 1.51 and 1.88, respectively, for the studied BZT-BCT compositions. All three compositions showed packing-limited breakdown fields of ∼47-73 kV cm -1 with an energy density of 0.05-0.6 J cm -3 for thick ceramics (>1 mm). Therefore these compositions might be useful in Y5V-type capacitor applications.

  11. Titanate nanotube thin films with enhanced thermal stability and high-transparency prepared from additive-free sols

    Energy Technology Data Exchange (ETDEWEB)

    Koroesi, Laszlo, E-mail: korosi@enviroinvest.hu [Supramolecular and Nanostructured Materials Research Group of the Hungarian Academy of Sciences, University of Szeged, Aradi vertanuk tere 1, H-6720 Szeged (Hungary); Department of Biotechnology, Nanophage Therapy Center, Enviroinvest Corporation, Kertvaros utca 2, H-7632 Pecs (Hungary); Papp, Szilvia [Supramolecular and Nanostructured Materials Research Group of the Hungarian Academy of Sciences, University of Szeged, Aradi vertanuk tere 1, H-6720 Szeged (Hungary); Department of Biotechnology, Nanophage Therapy Center, Enviroinvest Corporation, Kertvaros utca 2, H-7632 Pecs (Hungary); Hornok, Viktoria [Supramolecular and Nanostructured Materials Research Group of the Hungarian Academy of Sciences, University of Szeged, Aradi vertanuk tere 1, H-6720 Szeged (Hungary); Oszko, Albert [Department of Physical Chemistry and Materials Science, University of Szeged, Aradi vertanuk tere 1, H-6720 Szeged (Hungary); Petrik, Peter; Patko, Daniel; Horvath, Robert [Institute for Technical Physics and Materials Science MFA, Research Center for Natural Sciences, Konkoly-Thege ut 29-33, H-1121 Budapest (Hungary); Dekany, Imre [Supramolecular and Nanostructured Materials Research Group of the Hungarian Academy of Sciences, University of Szeged, Aradi vertanuk tere 1, H-6720 Szeged (Hungary)

    2012-08-15

    Titanate nanotubes were synthesized from TiO{sub 2} in alkaline medium by a conventional hydrothermal method (150 Degree-Sign C, 4.7 bar). To obtain hydrogen titanates, the as-prepared sodium titanates were treated with either HCl or H{sub 3}PO{sub 4} aqueous solutions. A simple synthesis procedure was devised for stable titanate nanotube sols without using any additives. These highly stable ethanolic sols can readily be used to prepare transparent titanate nanotube thin films of high quality. The resulting samples were studied by X-ray diffraction, N{sub 2}-sorption measurements, Raman spectroscopy, transmission and scanning electron microscopy, X-ray photoelectron spectroscopy and spectroscopic ellipsometry. The comparative results of using two kinds of acids shed light on the superior thermal stability of the H{sub 3}PO{sub 4}-treated titanate nanotubes (P-TNTs). X-ray photoelectron spectroscopy revealed that P-TNTs contains P in the near-surface region and the thermal stability was enhanced even at a low ({approx}0.5 at%) concentration of P. After calcination at 500 Degree-Sign C, the specific surface areas of the HCl- and H{sub 3}PO{sub 4}-treated samples were 153 and 244 m{sup 2} g{sup -1}, respectively. The effects of H{sub 3}PO{sub 4} treatment on the structure, morphology and porosity of titanate nanotubes are discussed. - Graphical Abstract: TEM picture (left) shows P-TNTs with diameters about 5-6 nm. Inset shows a stable titanate nanotube sol illuminated by a 532 nm laser beam. Due to the presence of the nanoparticles the way of the light is visible in the sol. Cross sectional SEM picture (right) as well as ellipsometry revealed the formation of optical quality P-TNT films with thicknesses below 50 nm. Highlights: Black-Right-Pointing-Pointer H{sub 3}PO{sub 4} treatment led to TNTs with high surface area even after calcination at 500 Degree-Sign C. Black-Right-Pointing-Pointer H{sub 3}PO{sub 4}-treated TNTs preserved their nanotube morphology up to 500

  12. Niobium-doped strontium titanates as SOFC anodes

    DEFF Research Database (Denmark)

    Blennow Tullmar, Peter; Kammer Hansen, Kent; Wallenberg, L. Reine

    2008-01-01

    been synthesized with a recently developed modified glycine-nitrate process. The synthesized powders have been calcined and sintered in air or in 9% H(2) / N(2) between 800 - 1400 degrees C. After calcination the samples were single phase Nb-doped strontium titanate with grain sizes of less than 100 nm...... in diameter on average. The phase purity, defect structure, and microstructure of the materials have been analyzed with SEM, XRD, and TGA. The electrical conductivity of the Nb-doped titanate decreased with increasing temperature and showed a phonon scattering conduction mechanism with sigma > 120 S...... ability of the Nb-doped titanates to be used as a part of a SOFC anode. However, the catalytic activity of the materials was not sufficient and it needs to be improved if titanate based materials are to be realized as constituents in SOFC anodes....

  13. LARGE ABUNDANCES OF POLYCYCLIC AROMATIC HYDROCARBONS IN TITAN'S UPPER ATMOSPHERE

    Energy Technology Data Exchange (ETDEWEB)

    Lopez-Puertas, M.; Funke, B.; Garcia-Comas, M. [Instituto de Astrofisica de Andalucia (CSIC), E-18080 Granada (Spain); Dinelli, B. M. [ISAC-CNR, I-40129 Bologna (Italy); Adriani, A.; D' Aversa, E. [IAPS-INAF, I-00133 Rome (Italy); Moriconi, M. L. [ISAC-CNR, I-00133 Rome (Italy); Boersma, C.; Allamandola, L. J., E-mail: puertas@iaa.es [NASA Ames Research Center, Moffett Field, CA 94035-1000 (United States)

    2013-06-20

    In this paper, we analyze the strong unidentified emission near 3.28 {mu}m in Titan's upper daytime atmosphere recently discovered by Dinelli et al. We have studied it by using the NASA Ames PAH IR Spectroscopic Database. The polycyclic aromatic hydrocarbons (PAHs), after absorbing UV solar radiation, are able to emit strongly near 3.3 {mu}m. By using current models for the redistribution of the absorbed UV energy, we have explained the observed spectral feature and have derived the vertical distribution of PAH abundances in Titan's upper atmosphere. PAHs have been found to be present in large concentrations, about (2-3) Multiplication-Sign 10{sup 4} particles cm{sup -3}. The identified PAHs have 9-96 carbons, with a concentration-weighted average of 34 carbons. The mean mass is {approx}430 u; the mean area is about 0.53 nm{sup 2}; they are formed by 10-11 rings on average, and about one-third of them contain nitrogen atoms. Recently, benzene together with light aromatic species as well as small concentrations of heavy positive and negative ions have been detected in Titan's upper atmosphere. We suggest that the large concentrations of PAHs found here are the neutral counterpart of those positive and negative ions, which hence supports the theory that the origin of Titan main haze layer is located in the upper atmosphere.

  14. Selective adsorption and ion exchange of metal cations and anions with silico-titanates and layered titanates

    International Nuclear Information System (INIS)

    Anthony, R.G.; Philip, C.V.

    1993-01-01

    Metal ions may be removed from aqueous wastes from metal processing plants and from refineries. They may also be used in concentrating radioactive elements found in dilute, aqueous, nuclear wastes. A new series of silico-titanates and alkali titanates are shown to have specific selectivity for cations of lead, mercury, and cadmium and the dichromate anion in solutions with low and high pH. Furthermore, one particular silico-titanate, TAM-5, was found to be highly selective for Cs + and Sr 2+ in solutions of 5.7 M Na + and 0.6 M Oh - . A high potential exists for these materials for removing Cs + and Sr 2+ from radioactive aqueous wastes containing high concentrations of Na + at high and low pH

  15. The TITAN Reversed-Field Pinch fusion reactor study

    International Nuclear Information System (INIS)

    1988-03-01

    The TITAN Reversed-Field Pinch (RFP) fusion reactor study is a multi-institutional research effort to determine the technical feasibility and key developmental issues of an RFP fusion reactor, especially at high power density, and to determine the potential economics, operations, safety, and environmental features of high-mass-power-density fusion systems. The TITAN conceptual designs are DT burning, 1000 MWe power reactors based on the RFP confinement concept. The designs are compact, have a high neutron wall loading of 18 MW/m 2 and a mass power density of 700 kWe/tonne. The inherent characteristics of the RFP confinement concept make fusion reactors with such a high mass power density possible. Two different detailed designs have emerged: the TITAN-I lithium-vanadium design, incorporating the integrated-blanket-coil concept; and the TITAN-II aqueous loop-in-pool design with ferritic steel structure. This report contains a collection of 16 papers on the results of the TITAN study which were presented at the International Symposium on Fusion Nuclear Technology. This collection describes the TITAN research effort, and specifically the TITAN-I and TITAN-II designs, summarizing the major results, the key technical issues, and the central conclusions and recommendations. Overall, the basic conclusions are that high-mass power-density fusion reactors appear to be technically feasible even with neutron wall loadings up to 20 MW/m 2 ; that single-piece maintenance of the FPC is possible and advantageous; that the economics of the reactor is enhanced by its compactness; and the safety and environmental features need not to be sacrificed in high-power-density designs. The fact that two design approaches have emerged, and others may also be possible, in some sense indicates the robustness of the general findings

  16. ALMA OBSERVATIONS OF HCN AND ITS ISOTOPOLOGUES ON TITAN

    Energy Technology Data Exchange (ETDEWEB)

    Molter, Edward M.; Nixon, C. A.; Cordiner, M. A.; Charnley, S. B.; Lindberg, J. E. [NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20771 (United States); Serigano, J. [Department of Earth and Planetary Sciences, Johns Hopkins University, Baltimore, MD 21218 (United States); Irwin, P. G. J. [Atmospheric, Oceanic, and Planetary Physics, Clarendon Laboratory, University of Oxford, Parks Road, Oxford, OX1 3PU (United Kingdom); Teanby, N. A., E-mail: edward.m.molter@nasa.gov [School of Earth Sciences, University of Bristol, Wills Memorial Building, Queens Road, Bristol, BS8 1RJ (United Kingdom)

    2016-08-01

    We present sub-millimeter spectra of HCN isotopologues on Titan, derived from publicly available ALMA flux calibration observations of Titan taken in early 2014. We report the detection of a new HCN isotopologue on Titan, H{sup 13}C{sup 15}N, and confirm an earlier report of detection of DCN. We model high signal-to-noise observations of HCN, H{sup 13}CN, HC{sup 15}N, DCN, and H{sup 13}C{sup 15}N to derive abundances and infer the following isotopic ratios: {sup 12}C/{sup 13}C = 89.8 ± 2.8, {sup 14}N/{sup 15}N = 72.3 ± 2.2, D/H = (2.5 ± 0.2) × 10{sup −4}, and HCN/H{sup 13}C{sup 15}N = 5800 ± 270 (1 σ errors). The carbon and nitrogen ratios are consistent with and improve on the precision of previous results, confirming a factor of ∼2.3 elevation in {sup 14}N/{sup 15}N in HCN compared to N{sub 2} and a lack of fractionation in {sup 12}C/{sup 13}C from the protosolar value. This is the first published measurement of D/H in a nitrile species on Titan, and we find evidence for a factor of ∼2 deuterium enrichment in hydrogen cyanide compared to methane. The isotopic ratios we derive may be used as constraints for future models to better understand the fractionation processes occurring in Titan’s atmosphere.

  17. Laboratory investigation of nitrile ices of Titan's stratospheric clouds

    Science.gov (United States)

    Nna Mvondo, D.; Anderson, C. M.; McLain, J. L.; Samuelson, R. E.

    2017-09-01

    Titan's mid to lower stratosphere contains complex cloud systems of numerous organic ice particles comprised of both hydrocarbon and nitrile compounds. Most of these stratospheric ice clouds form as a result of vapor condensation formation processes. However, there are additional ice emission features such as dicyanoacetylene (C4N2) and the 220 cm-1 ice emission feature (the "Haystack") that are difficult to explain since there are no observed vapor emission features associated with these ices. In our laboratory, using a high-vacuum chamber coupled to a FTIR spectrometer, we are engaged in a dedicated investigation of Titan's stratospheric ices to interpret and constrain Cassini Composite InfraRed Spectrometer (CIRS) far-IR data. We will present laboratory transmittance spectra obtained for propionitrile (CH3CH2CN), cyanogen (C2N2) and hydrogen cyanide (HCN) ices, as well as various combinations of their mixtures, to better understand the cloud chemistry occurring in Titan's stratosphere.

  18. Epitaxial growth of SrTiO3 (001) films on multilayer buffered GaN (0002) by pulsed laser deposition

    International Nuclear Information System (INIS)

    Luo, W B; Jing, J; Shuai, Y; Zhu, J; Zhang, W L; Zhou, S; Gemming, S; Du, N; Schmidt, H

    2013-01-01

    SrTiO 3 films were grown on CeO 2 /YSZ/TiO 2 multilayer buffered GaN/Al 2 O 3 (0001) substrates with and without the YBa 2 Cu 3 O 7-x (YBCO) bridge layer by pulsed laser deposition (PLD). The deposition process of the buffer layers was in situ monitored by reflection high-energy electron diffraction. The crystallographical orientation of the heterostructure was studied by x-ray diffraction (XRD). With the introduction of the YBCO (001) layer, the STO (001) film was epitaxially grown on the GaN substrate. There were three sets of inplane domains separated from each other by 30° in both STO and YBCO buffer layers. The epitaxial relationship was STO (002)[110]∥YBCO(001)[110]∥CeO 2 (002)[010]∥YSZ (002)[010]∥GaN(0001)[1 1 -2 0] according to XRD results. By comparing the orientation of STO grown on GaN with and without the YBCO top buffer layer, the surface chemical bonding was found to be a very important factor in determining the orientation relationship of STO.

  19. TIOMAX: A Spanish Multicenter Registry of the real-world use of the TItanium OptiMAX® biostent: TIOMAX: Registro Español Multicéntrico Del Biostent De Titanio OptiMAX® En La Vida Real.

    Science.gov (United States)

    López-Mínguez, José R; Nogales-Asensio, Juan M; Romani, Sebastián; Rivero-Crespo, Fernando; Aragón-Extremera, Victor M; Jiménez-Mazuecos, Jesús M; Carrasco, Fernando; Oteo-Domínguez, Juan Francisco; Bosa-Ojeda, Francisco; Gómez-Hospital, Joan A

    2017-09-30

    To compare the safety and efficacy of the new cobalt-chromium bioactive stent Titan Optimax ® (Hexacath, France) with its predecessor, Titan-2 ® . The TIOMAX registry includes 784 patients who underwent percutaneous coronary intervention with these stents in 21 Spanish hospitals. Analysis of all patients in the registry without exclusion criteria, candidates for revascularization (March-2013/July-2014). Initially 273 patients received Titan-2 ® , and the next 511 received the Optimax ® after its launch. Mean age was 65.8 ± 13.0 (78.1% men); 49.2% were STEACS patients (n = 322), 29.8% NSTEACS, and 27.3% had stable angina or silent ischemia. Most STEACS patients (76.4% of n = 322) were treated <24 hr after developing symptoms. All-cause death (D), cardiac death (CD), acute myocardial infarction (AMI), and stent thrombosis (ST) at 1 month were 1.1, 0.8, 0.1, and 0.5%, respectively, with no significant differences between groups. At 1 year, the death rate was 5.5% for Titan-2 vs. 4.1% for Optimax ® , CD was 1.8% for both groups, ST 1.1 vs. 0.6%, new AMI 3.3 vs. 2.5% and target lesion revascularization (TLR) 3.7 vs. 2.9%. The primary endpoint of the composite event (CE) of D/AMI/TLR/ST occurred in 10.3% vs. 7.6% (p = 0.211). Patients with STEACS (N = 322: Titan-2/Optimax: 103/209) had better outcomes for secondary events, device-oriented failure CD/AMI/TLR (7.8% vs. 5.0%; p = 0.330), and non-fatal CE of AMI/ST/TLR (7.8% vs. 2.7%, p = 0.039). The Titan Optimax retains the efficacy and safety of Titan 2. It appears to perform better in the subgroup of STEACS patients, by reducing the non-fatal CE of AMI/ST/TLR. © 2017 Wiley Periodicals, Inc.

  20. Towards a solution of the puzzle posed by superconducting SrTiO3

    Science.gov (United States)

    Malik, G. P.

    2015-09-01

    Suitably doped SrTiO3 was found in 1964 to undergo a superconducting transition below 1 K with a dome-like Tc versus n (electron concentration) plot. The apex of the dome — a point of inflection — corresponds to the point (n≈9 ×1019cm-3, Tc≈0.30 K). On either side of it, Tc goes down to ≈0.1 K for the extreme values between which n was varied. A single value of Tc is thus observed for two different values of n. The puzzle for the theory has been to explain this result. Treating the problem in all its generality, we present here three equations: the μ1-incorporated BCS equation for Tc, the μ0-incorporated equation for the T = 0 gap Δ0, where μ1 and μ0 are the chemical potentials at T = Tc and T = 0 respectively, and an equation that relates the interaction parameters λ1 and λ0 at these temperatures. Because there are five unknowns in the problem, we tackle these equations via an approximation scheme that includes setting μ1 = μ0 and λ1 = λ0. The latter of these is factually a basic tenet of the BCS theory. Salient features of our findings are: (i) the solutions for Tc and Δ0 on the RHS (LHS) of the dome correspond to μ> kBθD(μ LHS the limits of the integrals in the equations need to be curtailed to obtain real solutions and (iii) the point μ = kBθD is a point of inflection in the Tc versus μ plot. Since the puzzle has remained unsolved for a long time, we also offer here a purely mathematical model for λ(μ) — sans physical justification — which leads to a Tc versus μ plot qualitatively in agreement with experiment.