Sample records for oxide liti2o4 thin

  1. Reversible superconductor-insulator transition in LiTi2O4 induced by Li-ion electrochemical reaction

    PubMed Central

    Yoshimatsu, K.; Niwa, M.; Mashiko, H.; Oshima, T.; Ohtomo, A.

    2015-01-01

    Transition metal oxides display various electronic and magnetic phases such as high-temperature superconductivity. Controlling such exotic properties by applying an external field is one of the biggest continuous challenges in condensed matter physics. Here, we demonstrate clear superconductor-insulator transition of LiTi2O4 films induced by Li-ion electrochemical reaction. A compact electrochemical cell of pseudo-Li-ion battery structure is formed with a superconducting LiTi2O4 film as an anode. Li content in the film is controlled by applying a constant redox voltage. An insulating state is achieved by Li-ion intercalation to the superconducting film by applying reduction potential. In contrast, the superconducting state is reproduced by applying oxidation potential to the Li-ion intercalated film. Moreover, superconducting transition temperature is also recovered after a number of cycles of Li-ion electrochemical reactions. This complete reversible transition originates in difference in potentials required for deintercalation of initially contained and electrochemically intercalated Li+ ions. PMID:26541508

  2. Reversible superconductor-insulator transition in LiTi2O4 induced by Li-ion electrochemical reaction.

    PubMed

    Yoshimatsu, K; Niwa, M; Mashiko, H; Oshima, T; Ohtomo, A

    2015-11-06

    Transition metal oxides display various electronic and magnetic phases such as high-temperature superconductivity. Controlling such exotic properties by applying an external field is one of the biggest continuous challenges in condensed matter physics. Here, we demonstrate clear superconductor-insulator transition of LiTi2O4 films induced by Li-ion electrochemical reaction. A compact electrochemical cell of pseudo-Li-ion battery structure is formed with a superconducting LiTi2O4 film as an anode. Li content in the film is controlled by applying a constant redox voltage. An insulating state is achieved by Li-ion intercalation to the superconducting film by applying reduction potential. In contrast, the superconducting state is reproduced by applying oxidation potential to the Li-ion intercalated film. Moreover, superconducting transition temperature is also recovered after a number of cycles of Li-ion electrochemical reactions. This complete reversible transition originates in difference in potentials required for deintercalation of initially contained and electrochemically intercalated Li(+) ions.

  3. The effects of oxygen in spinel oxide Li1+xTi2-xO4thin films.

    PubMed

    Jia, Yanli; He, Ge; Hu, Wei; Yang, Hua; Yang, Zhenzhong; Yu, Heshan; Zhang, Qinghua; Shi, Jinan; Lin, Zefeng; Yuan, Jie; Zhu, Beiyi; Gu, Lin; Li, Hong; Jin, Kui

    2018-03-05

    The evolution from superconducting LiTi 2 O 4-δ to insulating Li 4 Ti 5 O 12 thin films has been studied by precisely tuning the oxygen pressure in the sample fabrication process. In superconducting LiTi 2 O 4-δ films, with the increase of oxygen pressure, the oxygen vacancies are filled gradually and the c-axis lattice constant decreases. When the oxygen pressure increases to a certain critical value, the c-axis lattice constant becomes stable, which implies that the sample has been completely converted to Li 4 Ti 5 O 12 phase. The two processes can be manifested by the angular bright-field images of the scanning transmission electron microscopy techniques. The transition temperature (T ch ) of magnetoresistance from the positive to the negative shows a nonmonotonic behavior, i.e. first decrease and then increase, with the increase of oxygen pressure. We suggest that the decrease T ch can be attributed to the suppressing of orbital-related state, and the inhomogeneous phase separated regions contribute positive MR and thereby lead to the reverse relation between T ch and oxygen pressure.

  4. New ramsdellites LiTi 2-yV yO 4 (0≤ y≤1): Synthesis, structure, magnetic properties and electrochemical performances as electrode materials for lithium batteries

    NASA Astrophysics Data System (ADS)

    Kuhn, Alois; Martín, María; García-Alvarado, Flaviano

    2010-01-01

    The new ramsdellite series LiTi 2-yV yO 4 (0≤ y≤1) has been prepared by conventional solid state chemistry techniques and was characterized by X-ray powder diffraction and electron diffraction. To our knowledge, this is the first report on ramsdellites containing vanadium. The magnetic behaviour of these ramsdellites is strongly influenced by its vanadium content. In this sense, LiTi 2O 4 ( y=0) exhibits metallic-like temperature independent paramagnetism, but d electrons tend to localize with increasing V content. LiTiVO 4, though also paramagnetic, follows then the Curie-Weiss law. The crossover from delocalized to localized electrons is observed between compositions y=0.6 and 0.8. For y≥0.8 the magnetic results evidence an isovalent substitution mechanism of trivalent Ti by V. The electrochemical lithium intercalation and deintercalation chemistry of LiTi 2-yV yO 4 is grouped into two different operating voltage regions. Reversible lithium deintercalation of vanadium-substituted ramsdellite titanates LiTi 2-yV yO 4 in the high voltage range 2-3 V vs. Li occurs in two main steps, one at about 2 V and the other at about 3 V. The 3 V process capacity increases with the vanadium content, while the 2 V capacity decreases at the same time. The vanadium to titanium substitution rate in LiTi 2O 4 was found to be beneficial to the specific energy in as much as a 50% increase (1 V) of the working voltage is observed. On the other hand, reversible lithium intercalation in vanadium-substituted ramsdellite titanates LiTi 2-yV yO 4 in the low voltage range 1-2 V vs. Li occurs in one main single step, in which the capacity is not affected by the vanadium content, although vanadium-doping produces an improved capacity retention with an excellent cycling behaviour observed for y≤0.6.

  5. One-pot synthesis of carbon-coated nanosized LiTi2(PO4)3 as anode materials for aqueous lithium ion batteries

    NASA Astrophysics Data System (ADS)

    Liu, Zhantao; Qin, Xusong; Xu, Hui; Chen, Guohua

    2015-10-01

    In this study, a one-pot sintering process incorporating sol-gel preparation route and in-situ carbon coating was proposed for the synthesis of carbon-coated nanosized LiTi2(PO4)3. Experimental results show that the prepared LiTi2(PO4)3 particles are of high crystallinity and well-coated by turbostratic carbon. Attributed to nanosized particles and enhanced conductivity provided by turbostratic carbon coating, the carbon-coated LiTi2(PO4)3 showed high rate performance and good cycling life in aqueous electrolyte. Particularly, the carbon-coated LiTi2(PO4)3 exhibited initial specific capacities of 103 and 89 mAh g-1, and retained 80.6% and 97% of the initial capacities after 120 cycles at 1C and 10C in aqueous electrolyte, respectively. The high rate performance and good cycling life of carbon-coated LiTi2(PO4)3 in aqueous electrolyte reveal its potential as negative electrode in aqueous lithium-ion batteries for electric vehicles and industrial-scale energy storage systems.

  6. All-spinel oxide Josephson junctions for high-efficiency spin filtering.

    PubMed

    Mesoraca, S; Knudde, S; Leitao, D C; Cardoso, S; Blamire, M G

    2018-01-10

    Obtaining high efficiency spin filtering at room temperature using spinel ferromagnetic tunnel barriers has been hampered by the formation of antiphase boundaries due to their difference in lattice parameters between barrier and electrodes. In this work we demonstrate the use of LiTi 2 O 4 thin films as electrodes in an all-spinel oxide CoFe 2 O 4 -based spin filter devices. These structures show nearly perfect epitaxy maintained throughout the structure and so minimise the potential for APBs formation. The LiTi 2 O 4 in these devices is superconducting and so measurements at low temperature have been used to explore details of the tunnelling and Josephson junction behaviour.

  7. Synthesis, characterization and oxidation of metallic cobalt (Co) thin film into semiconducting cobalt oxide (Co3O4)thin film using microwave plasma CVD

    NASA Astrophysics Data System (ADS)

    Rahman Ansari, Akhalakur; Hussain, Shahir; Imran, Mohd; Abdel-wahab, M. Sh; Alshahrie, Ahmed

    2018-06-01

    The pure cobalt thin film was deposited on the glass substrate by using DC magnetron sputtering and then exposed to microwave assist oxygen plasma generated in microwave plasma CVD. The oxidation process of Co thin film into Co3O4 thin films with different microwave power and temperature were studied. The influences of microwave power, temperature and irradiation time were investigated on the morphology and particle size of oxide thin films. The crystal structure, chemical conformation, morphologies and optical properties of oxidized Co thin films (Co3O4) were studied by using x-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), Raman Spectroscopy and UV–vis Spectroscopy. The data of these films showed complete oxidation pure metallic cobalt (Co) into cobalt oxide (Co3O4). The optical properties were studied for calculating the direct band gaps which ranges from 1.35 to 1.8 eV.

  8. Oxidation of atomically thin MoS2 on SiO2

    NASA Astrophysics Data System (ADS)

    Yamamoto, Mahito; Cullen, William; Einstein, Theodore; Fuhrer, Michael

    2013-03-01

    Surface oxidation of MoS2 markedly affects its electronic, optical, and tribological properties. However, oxidative reactivity of atomically thin MoS2 has yet to be addressed. Here, we investigate oxidation of atomic layers of MoS2 using atomic force microscopy and Raman spectroscopy. MoS2 is mechanically exfoliated onto SiO2 and oxidized in Ar/O2 or Ar/O3 (ozone) at 100-450 °C. MoS2 is much more reactive to O2 than an analogous atomic membrane of graphene and monolayer MoS2 is completely etched very rapidly upon O2 treatment above 300 °C. Thicker MoS2 (> 15 nm) transforms into MoO3 after oxidation at 400 °C, which is confirmed by a Raman peak at 820 cm-1. However, few-layer MoS2 oxidized below 400 °C exhibits no MoO3 Raman mode but etch pits are formed, similar to graphene. We find atomic layers of MoS2 shows larger reactivity to O3 than to O2 and monolayer MoS2 transforms chemically upon O3 treatment even below 100 °C. Work supported by the U. of Maryland NSF-MRSEC under Grant No. DMR 05-20741.

  9. The low temperature oxidation of lithium thin films on HOPG by O 2 and H 2O

    DOE PAGES

    Wulfsberg, Steven M.; Koel, Bruce E.; Bernasek, Steven L.

    2016-04-16

    Lithiated graphite and lithium thin films have been used in fusion devices. In this environment, lithiated graphite will undergo oxidation by background gases. In order to gain insight into this oxidation process, thin (< 15 monolayer (ML)) lithium films on highly ordered pyrolytic graphite (HOPG) were exposed in this paper to O 2(g) and H 2O (g) in an ultra-high vacuum chamber. High resolution electron energy loss spectroscopy (HREELS) was used to identify the surface species formed during O 2(g) and H 2O (g) exposure. Auger electron spectroscopy (AES) was used to obtain the relative oxidation rates during O 2(g)more » and H 2O (g) exposure. AES showed that as the lithium film thickness decreased from 15 to 5 to 1 ML, the oxidation rate decreased for both O 2(g) and H 2O (g). HREELS showed that a 15 ML lithium film was fully oxidized after 9.7 L (L) of O 2(g) exposure and Li 2O was formed. HREELS also showed that during initial exposure (< 0.5 L) H 2O (g), lithium hydride and lithium hydroxide were formed on the surface of a 15 ML lithium film. Finally, after 0.5 L of H 2O (g) exposure, the H 2O (g) began to physisorb, and after 15 L of H 2O (g) exposure, the 15 ML lithium film was not fully oxidized.« less

  10. The low temperature oxidation of lithium thin films on HOPG by O 2 and H 2O

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Wulfsberg, Steven M.; Koel, Bruce E.; Bernasek, Steven L.

    Lithiated graphite and lithium thin films have been used in fusion devices. In this environment, lithiated graphite will undergo oxidation by background gases. In order to gain insight into this oxidation process, thin (< 15 monolayer (ML)) lithium films on highly ordered pyrolytic graphite (HOPG) were exposed in this paper to O 2(g) and H 2O (g) in an ultra-high vacuum chamber. High resolution electron energy loss spectroscopy (HREELS) was used to identify the surface species formed during O 2(g) and H 2O (g) exposure. Auger electron spectroscopy (AES) was used to obtain the relative oxidation rates during O 2(g)more » and H 2O (g) exposure. AES showed that as the lithium film thickness decreased from 15 to 5 to 1 ML, the oxidation rate decreased for both O 2(g) and H 2O (g). HREELS showed that a 15 ML lithium film was fully oxidized after 9.7 L (L) of O 2(g) exposure and Li 2O was formed. HREELS also showed that during initial exposure (< 0.5 L) H 2O (g), lithium hydride and lithium hydroxide were formed on the surface of a 15 ML lithium film. Finally, after 0.5 L of H 2O (g) exposure, the H 2O (g) began to physisorb, and after 15 L of H 2O (g) exposure, the 15 ML lithium film was not fully oxidized.« less

  11. An influence of a Glass Braze Composition on the Properties of Li-Ti Ferrite Joints

    NASA Astrophysics Data System (ADS)

    Lin, Panpan; Lin, Tiesong; He, Peng; Sekulic, Dusan P.; Zhao, Mengyuan; Wang, Shulei

    2017-04-01

    The influence of the chemical composition of Bi2O3-B2O3-SiO2-ZnO glass brazes on (i) the microstructure, (ii) the mechanical and (iii) the dielectric properties of Li-Ti ferrite joints was systematically investigated. The Bi5(Ti3Fe)O15 whisker and a white block phase consisting of Bi12SiO2 and Bi24B2O39 were observed in the joints of Li-Ti ferrite/Bi25-Ba and Li-Ti ferrite/glass brazes, respectively, containing a higher content of Bi2O3. No crystalline phase was detected in the Li-Ti ferrite/Bi25 and Li-Ti ferrite/Bi20 joints. The joint strength reached the maximum of 48 MPa in the Li-Ti ferrite/Bi25-Ba couples. It is assumed that this is mainly due to the strengthening effect of Bi5(Ti3Fe)O15 whiskers. The bonding temperature (700°C) had little effect on the dielectric properties of Li-Ti ferrite. Moreover, compared to the Bi25-Ba glass brazes, the Bi25 and Bi20 glass brazes had a less pronounced influence on the dielectric properties of joints. Different glass brazes can be tailored to different requirements depending on specific application and joint property requirements.

  12. Molten Salt Assisted Self-Assembly: Synthesis of Mesoporous LiCoO2 and LiMn2 O4 Thin Films and Investigation of Electrocatalytic Water Oxidation Performance of Lithium Cobaltate.

    PubMed

    Saat, Gülbahar; Balci, Fadime Mert; Alsaç, Elif Pınar; Karadas, Ferdi; Dag, Ömer

    2018-01-01

    Mesoporous thin films of transition metal lithiates (TML) belong to an important group of materials for the advancement of electrochemical systems. This study demonstrates a simple one pot method to synthesize the first examples of mesoporous LiCoO 2 and LiMn 2 O 4 thin films. Molten salt assisted self-assembly can be used to establish an easy route to produce mesoporous TML thin films. The salts (LiNO 3 and [Co(H 2 O) 6 ](NO 3 ) 2 or [Mn(H 2 O) 4 ](NO 3 ) 2 ) and two surfactants (10-lauryl ether and cethyltrimethylammonium bromide (CTAB) or cethyltrimethylammonium nitrate (CTAN)) form stable liquid crystalline mesophases. The charged surfactant is needed for the assembly of the necessary amount of salt in the hydrophilic domains of the mesophase, which produces stable metal lithiate pore-walls upon calcination. The films have a large pore size with a high surface area that can be increased up to 82 m 2 g -1 . The method described can be adopted to synthesize other metal oxides and metal lithiates. The mesoporous thin films of LiCoO 2 show promising performance as water oxidation catalysts under pH 7 and 14 conditions. The electrodes, prepared using CTAN as the cosurfactant, display the lowest overpotentials in the literature among other LiCoO 2 systems, as low as 376 mV at 10 mA cm -2 and 282 mV at 1 mA cm -2 . © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. A photochemical proposal for the preparation of ZnAl{sub 2}O{sub 4} and MgAl{sub 2}O{sub 4} thin films from β-diketonate complex precursors

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Cabello, G., E-mail: gerardocabelloguzman@hotmail.com; Lillo, L.; Caro, C.

    2016-05-15

    Highlights: • ZnAl{sub 2}O{sub 4} and MgAl{sub 2}O{sub 4} thin films were prepared by photo-chemical method. • The Zn(II), Mg(II) and Al(III) β-diketonate complexes were used as precursors. • The photochemical reaction was monitored by UV–vis and FT-IR spectroscopy. • The results reveal spinel oxide formation and the generation of intermediate products. - Abstract: ZnAl{sub 2}O{sub 4} and MgAl{sub 2}O{sub 4} thin films were grown on Si(100) and quartz plate substrates using a photochemical method in the solid phase with thin films of β-diketonate complexes as the precursors. The films were deposited by spin-coating and subsequently photolyzed at room temperaturemore » using 254 nm UV light. The photolysis of these films results in the deposition of metal oxide thin films and fragmentation of the ligands from the coordination sphere of the complexes. The obtained samples were post-annealed at different temperatures (350–1100 °C) for 2 h and characterized by FT-Infrared spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), atomic force miscroscopy (AFM), and UV–vis spectroscopy. The results indicate the formation of spinel-type structures and other phases. These characteristics determined the quality of the films, which were obtained from the photodeposition of ternary metal oxides.« less

  14. Thermal conversion of Cu4O3 into CuO and Cu2O and the electrical properties of magnetron sputtered Cu4O3 thin films

    NASA Astrophysics Data System (ADS)

    Murali, Dhanya S.; Aryasomayajula, Subrahmanyam

    2018-03-01

    Among the three oxides of copper (CuO, Cu2O, and Cu4O3), Cu4O3 phase (paramelaconite is a natural, and very scarce mineral) is very difficult to synthesize. It contains copper in both + 1 and + 2 valence states, with an average composition Cu2 1+Cu2 2+O3. We have successfully synthesized Cu4O3 phase at room temperature (300 K) by reactive DC magnetron sputtering by controlling the oxygen flow rate (Murali and Subrahmanyam in J Phys D Appl Phys 49:375102, 2016). In the present communication, Cu4O3 thin films are converted to CuO phases by annealing in the air at 680 K and to Cu2O phase when annealed in argon at 720 K; these phase changes are confirmed by temperature-dependent Raman spectroscopy studies. Probably, this is the first report of the conversion of Cu4O3-CuO and Cu2O by thermal annealing. The temperature-dependent (300-200 K) electrical transport properties of Cu4O3 thin films show that the charge transport above 190 K follows Arrhenius-type behavior with activation energy of 0.14 eV. From photo-electron spectroscopy and electrical transport measurements of Cu4O3 thin films, a downward band bending is observed at the surface of the thin film, which shows its p-type semiconducting nature. The successful preparation of phase pure p-type semiconducting Cu4O3 could provide opportunities to further explore its potential applications.

  15. Preparation of Zinc Oxide (ZnO) Thin Film as Transparent Conductive Oxide (TCO) from Zinc Complex Compound on Thin Film Solar Cells: A Study of O2 Effect on Annealing Process

    NASA Astrophysics Data System (ADS)

    Muslih, E. Y.; Kim, K. H.

    2017-07-01

    Zinc oxide (ZnO) thin film as a transparent conductive oxide (TCO) for thin film solar cell application was successfully prepared through two step preparations which consisted of deposition by spin coating at 2000 rpm for 10 second and followed by annealing at 500 °C for 2 hours under O2 and ambient atmosphere. Zinc acetate dehydrate was used as a precursor which dissolved in ethanol and acetone (1:1 mol) mixture in order to make a zinc complex compound. In this work, we reported the O2 effect, reaction mechanism, structure, morphology, optical and electrical properties. ZnO thin film in this work shows a single phase of wurtzite, with n-type semiconductor and has band gap, carrier concentration, mobility, and resistivity as 3.18 eV, 1.21 × 10-19cm3, 11 cm2/Vs, 2.35 × 10-3 Ωcm respectively which is suitable for TCO at thin film solar cell.

  16. A photoelectrochemical (PEC) study on graphene oxide based hematite thin films heterojunction (R-GO/Fe2O3)

    NASA Astrophysics Data System (ADS)

    Sharma, Poonam; Zachariah, Michael; Ehrman, Sheryl; Shrivastava, Rohit; Dass, Sahab; Satsangi, Vibha; Michael Zachariah, Sheryl Ehrman Collaboration; Rohit Shrivastava, Sahab Dass Collaboration; Vibha R Satsangi, Poonam Sharma Team

    2013-03-01

    Graphene has an excellent electronic conductivity, a high theoretical surface area of 2630 m2/g and excellent mechanical properties and, thus, is a promising component for high-performance electrode materials. Following this, GO has been used to modify the PEC response of photoactive material hematite thin films in PEC cell. A reduced graphene oxide/iron oxide (R-GO/Fe2O3) thin film structure has been successfully prepared on ITO by directly growing iron oxide particles on the thermally reduced graphene oxide sheets prepared from suspension of exfoliated graphene oxide. R-GO/Fe2O3 thin films were tested in PEC cell and offered ten times higher photocurrent density than pristine Fe2O3 thin film sample. XRD, SEM, EDS, UV-Vis, Mott-Schottky and Raman studies were carried out to study spectro-electrochemical properties. Enhanced PEC performance of these photoelectrodes was attributed to its porous morphology, improved conductivity upon favorable carrier transfer across the oxides interface.

  17. Improved photoelectrochemical performance of BiVO4/MoO3 heterostructure thin films

    NASA Astrophysics Data System (ADS)

    Kodan, Nisha; Mehta, B. R.

    2018-05-01

    Bismuth vanadate (BiVO4) and Molybdenum trioxide (MoO3) thin films have been prepared by RF sputtering technique. BiVO4 thin films were deposited on indium doped tin oxide (In: SnO2; ITO) substrates at room temperature and 80W applied rf power. The prepared BiVO4 thin films were further annealed at 450°C for 2 hours in air to obtain crystalline monoclinic phase and successively coated with MoO3 thin films deposited at 150W rf power and 400°C for 30 minutes. The effect of coupling BiVO4 and MoO3 on the structural, optical and photoelectrochemical (PEC) properties have been studied. Optical studies reveal that coupling of BiVO4 and MoO3 results in improvement of optical absorption in visible region of solar spectrum. PEC study shows approximate 3-fold and 38-fold increment in photocurrent values of BiVO4/MoO3 (0.38 mA/cm2) heterostructure thin film as compared to MoO3 (0.15 mA/cm2) and BiVO4 (10 µA/cm2) thin films at applied bias of 1 V vs Ag/AgCl in 0.5 M Na2SO4 (pH=7) electrolyte.

  18. Cu2O-based solar cells using oxide semiconductors

    NASA Astrophysics Data System (ADS)

    Minami, Tadatsugu; Nishi, Yuki; Miyata, Toshihiro

    2016-01-01

    We describe significant improvements of the photovoltaic properties that were achieved in Al-doped ZnO (AZO)/n-type oxide semiconductor/p-type Cu2O heterojunction solar cells fabricated using p-type Cu2O sheets prepared by thermally oxidizing Cu sheets. The multicomponent oxide thin film used as the n-type semiconductor layer was prepared with various chemical compositions on non-intentionally heated Cu2O sheets under various deposition conditions using a pulsed laser deposition method. In Cu2O-based heterojunction solar cells fabricated using various ternary compounds as the n-type oxide thin-film layer, the best photovoltaic performance was obtained with an n-ZnGa2O4 thin-film layer. In most of the Cu2O-based heterojunction solar cells using multicomponent oxides composed of combinations of various binary compounds, the obtained photovoltaic properties changed gradually as the chemical composition was varied. However, with the ZnO-MgO and Ga2O3-Al2O3 systems, higher conversion efficiencies (η) as well as a high open circuit voltage (Voc) were obtained by using a relatively small amount of MgO or Al2O3, e.g., (ZnO)0.91-(MgO)0.09 and (Ga2O3)0.975-(Al2O3)0.025, respectively. When Cu2O-based heterojunction solar cells were fabricated using Al2O3-Ga2O3-MgO-ZnO (AGMZO) multicomponent oxide thin films deposited with metal atomic ratios of 10, 60, 10 and 20 at.% for the Al, Ga, Mg and Zn, respectively, a high Voc of 0.98 V and an η of 4.82% were obtained. In addition, an enhanced η and an improved fill factor could be achieved in AZO/n-type multicomponent oxide/p-type Cu2O heterojunction solar cells fabricated using Na-doped Cu2O (Cu2O:Na) sheets that featured a resistivity controlled by optimizing the post-annealing temperature and duration. Consequently, an η of 6.25% and a Voc of 0.84 V were obtained in a MgF2/AZO/n-(Ga2O3-Al2O3)/p-Cu2O:Na heterojunction solar cell fabricated using a Cu2O:Na sheet with a resistivity of approximately 10 Ω·cm and a (Ga0.975Al0.025)2

  19. Synthesis of high-oxidation Y-Ba-Cu-O phases in superoxygenated thin films

    NASA Astrophysics Data System (ADS)

    Zhang, H.; Gauquelin, N.; McMahon, C.; Hawthorn, D. G.; Botton, G. A.; Wei, J. Y. T.

    2018-03-01

    It is known that solid-state reaction in high-pressure oxygen can stabilize high-oxidation phases of Y-Ba-Cu-O superconductors in powder form. We extend this superoxygenation concept of synthesis to thin films which, due to their large surface-to-volume ratio, are more reactive thermodynamically. Epitaxial thin films of YBa2Cu3O7 -δ grown by pulsed laser deposition are annealed at up to 700 atm O2 and 900 ∘C , in conjunction with Cu enrichment by solid-state diffusion. The films show the clear formation of Y2Ba4Cu7O15 -δ and Y2Ba4Cu8O16 as well as regions of YBa2Cu5O9 -δ and YBa2Cu6O10 -δ phases, according to scanning transmission electron microscopy, x-ray diffraction, and x-ray absorption spectroscopy. Similarly annealed YBa2Cu3O7 -δ powders show no phase conversion. Our results demonstrate a route of synthesis towards discovering more complex phases of cuprates and other superconducting oxides.

  20. Water oxidation catalyzed by the tetranuclear Mn complex [Mn(IV)4O5(terpy)4(H2O)2](ClO4)6.

    PubMed

    Gao, Yunlong; Crabtree, Robert H; Brudvig, Gary W

    2012-04-02

    The tetranuclear manganese complex [Mn(IV)(4)O(5)(terpy)(4)(H(2)O)(2)](ClO(4))(6) (1; terpy = 2,2':6',2″-terpyridine) gives catalytic water oxidation in aqueous solution, as determined by electrochemistry and GC-MS. Complex 1 also exhibits catalytic water oxidation when adsorbed on kaolin clay, with Ce(IV) as the primary oxidant. The redox intermediates of complex 1 adsorbed on kaolin clay upon addition of Ce(IV) have been characterized by using diffuse reflectance UV/visible and EPR spectroscopy. One of the products in the reaction on kaolin clay is Mn(III), as determined by parallel-mode EPR spectroscopic studies. When 1 is oxidized in aqueous solution with Ce(IV), the reaction intermediates are unstable and decompose to form Mn(II), detected by EPR spectroscopy, and MnO(2). DFT calculations show that the oxygen in the mono-μ-oxo bridge, rather than Mn(IV), is oxidized after an electron is removed from the Mn(IV,IV,IV,IV) tetramer. On the basis of the calculations, the formation of O(2) is proposed to occur by reaction of water with an electrophilic manganese-bound oxyl radical species, (•)O-Mn(2)(IV/IV), produced during the oxidation of the tetramer. This study demonstrates that [Mn(IV)(4)O(5)(terpy)(4)(H(2)O)(2)](ClO(4))(6) may be relevant for understanding the role of the Mn tetramer in photosystem II.

  1. Epitaxy of Zn{sub 2}TiO{sub 4} (1 1 1) thin films on GaN (0 0 1)

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Hsiao, Chu-Yun; Wu, Jhih-Cheng; Shih, Chuan-Feng, E-mail: cfshih@mail.ncku.edu.tw

    2013-03-15

    Highlights: ► High-permittivity spinel Zn{sub 2}TiO{sub 4} thin films were grown on GaN (0 0 1) by sputtering. ► Oxygen atmosphere and post heat-treatment annealing effectively enhanced epitaxy. ► The epitaxial Zn{sub 2}TiO{sub 4} modifies the dielectric properties of ceramic oxide. - Abstract: High-permittivity spinel Zn{sub 2}TiO{sub 4} thin films were grown on GaN (0 0 1) by rf-sputtering. Grazing-angle, powder, and pole-figure X-ray diffractometries (XRD) were performed to identify the crystallinity and the preferred orientation of the Zn{sub 2}TiO{sub 4} films. Lattice image at the Zn{sub 2}TiO{sub 4} (1 1 1)/GaN (0 0 1) interface was obtained by high-resolutionmore » transmission-electron microscopy (HR-TEM). An oxygen atmosphere in sputtering and post heat-treatment using rapid thermal annealing effectively enhanced the epitaxy. The epitaxial relationship was determined from the XRD and HR-TEM results: (111){sub Zn{sub 2TiO{sub 4}}}||(001){sub GaN}, (202{sup ¯}){sub Zn{sub 2TiO{sub 4}}}||(110){sub GaN},and[21{sup ¯}1{sup ¯}]{sub Zn{sub 2TiO{sub 4}}}||[01{sup ¯}10]{sub GaN}. Finally, the relative permittivity, interfacial trap density and the flat-band voltage of the Zn{sub 2}TiO{sub 4} based capacitor were ∼18.9, 8.38 × 10{sup 11} eV{sup −1} cm{sup −2}, and 1.1 V, respectively, indicating the potential applications of the Zn{sub 2}TiO{sub 4} thin film to the GaN-based metal-oxide-semiconductor capacitor.« less

  2. Li4SiO4-Based Artificial Passivation Thin Film for Improving Interfacial Stability of Li Metal Anodes.

    PubMed

    Kim, Ji Young; Kim, A-Young; Liu, Guicheng; Woo, Jae-Young; Kim, Hansung; Lee, Joong Kee

    2018-03-14

    An amorphous SiO 2 (a-SiO 2 ) thin film was developed as an artificial passivation layer to stabilize Li metal anodes during electrochemical reactions. The thin film was prepared using an electron cyclotron resonance-chemical vapor deposition apparatus. The obtained passivation layer has a hierarchical structure, which is composed of lithium silicide, lithiated silicon oxide, and a-SiO 2 . The thickness of the a-SiO 2 passivation layer could be varied by changing the processing time, whereas that of the lithium silicide and lithiated silicon oxide layers was almost constant. During cycling, the surface of the a-SiO 2 passivation layer is converted into lithium silicate (Li 4 SiO 4 ), and the portion of Li 4 SiO 4 depends on the thickness of a-SiO 2 . A minimum overpotential of 21.7 mV was observed at the Li metal electrode at a current density of 3 mA cm -2 with flat voltage profiles, when an a-SiO 2 passivation layer of 92.5 nm was used. The Li metal with this optimized thin passivation layer also showed the lowest charge-transfer resistance (3.948 Ω cm) and the highest Li ion diffusivity (7.06 × 10 -14 cm 2 s -1 ) after cycling in a Li-S battery. The existence of the Li 4 SiO 4 artificial passivation layer prevents the corrosion of Li metal by suppressing Li dendritic growth and improving the ionic conductivity, which contribute to the low charge-transfer resistance and high Li ion diffusivity of the electrode.

  3. Influence of oxygen vacancies in ALD HfO2-x thin films on non-volatile resistive switching phenomena with a Ti/HfO2-x/Pt structure

    NASA Astrophysics Data System (ADS)

    Sokolov, Andrey Sergeevich; Jeon, Yu-Rim; Kim, Sohyeon; Ku, Boncheol; Lim, Donghwan; Han, Hoonhee; Chae, Myeong Gyoon; Lee, Jaeho; Ha, Beom Gil; Choi, Changhwan

    2018-03-01

    We report a modulation of oxygen vacancies profile in atomic layer deposition (ALD) HfO2-x thin films by reducing oxidant pulse time (0.7 s-0.1 s) and study its effect on resistive switching behavior with a Ti/HfO2-x/Pt structure. Hf 4f spectra of x-ray photoelectron microscopy (XPS) and depth profile confirm varied oxygen vacancies profiles by shifts of binding energies of Hf 4f5/2 and Hf 4f7/2 main peaks and its according HfO2-x sub-oxides for each device. The ultraviolet photoelectron spectroscopy (UPS) confirms different electron affinity (χ) of HfO2 and HfO2-x thin films, implying that barrier height at Ti/oxide interface is reduced. Current transport mechanism is dictated by Ohmic conduction in fully oxidized HfO2 thin films - Device A (0.7 s) and by Trap Filled Space Charge Limited Conduction (TF-SCLC) in less oxidized HfO2-x thin films - Device B (0.3 s) and Device C (0.1 s). A switching mechanism related to the oxygen vacancies modulation in Ti/HfO2-x/Pt based resistive random access memory (RRAM) devices is used to explain carefully notified current transport mechanism variations from device-to-device. A proper endurance and long-time retention characteristics of the devices are also obtained.

  4. Growth control of the oxidation state in vanadium oxide thin films

    NASA Astrophysics Data System (ADS)

    Lee, Shinbuhm; Meyer, Tricia L.; Park, Sungkyun; Egami, Takeshi; Lee, Ho Nyung

    2014-12-01

    Precise control of the chemical valence or oxidation state of vanadium in vanadium oxide thin films is highly desirable for not only fundamental research but also technological applications that utilize the subtle change in the physical properties originating from the metal-insulator transition (MIT) near room temperature. However, due to the multivalent nature of vanadium and the lack of a good understanding on growth control of the oxidation state, stabilization of phase pure vanadium oxides with a single oxidation state is extremely challenging. Here, we systematically varied the growth conditions to clearly map out the growth window for preparing phase pure epitaxial vanadium oxides by pulsed laser deposition for providing a guideline to grow high quality thin films with well-defined oxidation states of V2 + 3 O 3 , V + 4 O 2 , and V2 + 5 O 5 . A well pronounced MIT was only observed in VO2 films grown in a very narrow range of oxygen partial pressure P(O2). The films grown either in lower (<10 mTorr) or higher P(O2) (>25 mTorr) result in V2O3 and V2O5 phases, respectively, thereby suppressing the MIT for both cases. We have also found that the resistivity ratio before and after the MIT of VO2 thin films can be further enhanced by one order of magnitude when the films are further oxidized by post-annealing at a well-controlled oxidizing ambient. This result indicates that stabilizing vanadium into a single valence state has to compromise with insufficient oxidation of an as grown thin film and, thereby, a subsequent oxidation is required for an improved MIT behavior.

  5. Growth control of the oxidation state in vanadium oxide thin films

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Lee, Shinbuhm; Meyer, Tricia L.; Lee, Ho Nyung, E-mail: hnlee@ornl.gov

    2014-12-01

    Precise control of the chemical valence or oxidation state of vanadium in vanadium oxide thin films is highly desirable for not only fundamental research but also technological applications that utilize the subtle change in the physical properties originating from the metal-insulator transition (MIT) near room temperature. However, due to the multivalent nature of vanadium and the lack of a good understanding on growth control of the oxidation state, stabilization of phase pure vanadium oxides with a single oxidation state is extremely challenging. Here, we systematically varied the growth conditions to clearly map out the growth window for preparing phase puremore » epitaxial vanadium oxides by pulsed laser deposition for providing a guideline to grow high quality thin films with well-defined oxidation states of V{sub 2}{sup +3}O{sub 3}, V{sup +4}O{sub 2}, and V{sub 2}{sup +5}O{sub 5}. A well pronounced MIT was only observed in VO{sub 2} films grown in a very narrow range of oxygen partial pressure P(O{sub 2}). The films grown either in lower (<10 mTorr) or higher P(O{sub 2}) (>25 mTorr) result in V{sub 2}O{sub 3} and V{sub 2}O{sub 5} phases, respectively, thereby suppressing the MIT for both cases. We have also found that the resistivity ratio before and after the MIT of VO{sub 2} thin films can be further enhanced by one order of magnitude when the films are further oxidized by post-annealing at a well-controlled oxidizing ambient. This result indicates that stabilizing vanadium into a single valence state has to compromise with insufficient oxidation of an as grown thin film and, thereby, a subsequent oxidation is required for an improved MIT behavior.« less

  6. Impact of ultra-thin Al2O3-y layers on TiO2-x ReRAM switching characteristics

    NASA Astrophysics Data System (ADS)

    Trapatseli, Maria; Cortese, Simone; Serb, Alexander; Khiat, Ali; Prodromakis, Themistoklis

    2017-05-01

    Transition metal-oxide resistive random access memory devices have demonstrated excellent performance in switching speed, versatility of switching and low-power operation. However, this technology still faces challenges like poor cycling endurance, degradation due to high electroforming (EF) switching voltages and low yields. Approaches such as engineering of the active layer by doping or addition of thin oxide buffer layers have been often adopted to tackle these problems. Here, we have followed a strategy that combines the two; we have used ultra-thin Al2O3-y buffer layers incorporated between TiO2-x thin films taking into account both 3+/4+ oxidation states of Al/Ti cations. Our devices were tested by DC and pulsed voltage sweeping and in both cases demonstrated improved switching voltages. We believe that the Al2O3-y layers act as reservoirs of oxygen vacancies which are injected during EF, facilitate a filamentary switching mechanism and provide enhanced filament stability, as shown by the cycling endurance measurements.

  7. The role of Tin Oxide Concentration on The X-ray Diffraction, Morphology and Optical Properties of In2O3:SnO2 Thin Films

    NASA Astrophysics Data System (ADS)

    Hasan, Bushra A.; Abdallah, Rusul M.

    2018-05-01

    Alloys were performed from In2O3 doped SnO2 with different doping ratio by quenching from the melt technique. Pulsed Laser Deposition PLD was used to deposit thin films of different doping ratio In2O3 : SnO2 (0, 1, 3, 5, 7 and 9 % wt.) on glass substrate at ambient temperature under vacuum of 10-3 bar thickness of ∼100nm. The structural type,grain size and morphology of the prepared alloys compounds and thin films were examined using X-ray diffraction and atomic force microscopy. The results showed that all alloys have polycrystalline structures and the peaks belonged to the preferred plane for crystal growth were identical with the ITO (Indium – Tin –Oxide) standard cards also another peaks were observed belonged to SnO2 phase. The structures of thin films was also polycrystalline, and the predominate peaks are identical with standard cards ITO. On the other side the prepared thin films declared decrease a reduction of degree of crystallinity with the increase of doping ratio. Atomic Force Microscopy AFM measurements showed the average grain size and average surface roughness exhibit to change in systematic manner with the increase of doping ratio with tin oxide. The optical measurements show that the In2O3:SnO2 thin films have a direct energy gap Eg opt in the first stage decreases with the increase of doping ratio and then get to increase with further increase of doping ration, whereas reverse to that the optical constants such as refractive index (n), extinction coefficient (k) and dielectric constant (εr, εi) have a regular increase with the doping ratio by tin oxide and then decreases.

  8. Zn1-xAlxO:Cu2O transparent metal oxide composite thin films by sol gel method

    NASA Astrophysics Data System (ADS)

    AlHammad, M. S.

    2017-05-01

    We have synthesized undoped zinc oxide (ZnO) and Cu2O doped Zn1-XAlXO (AZO; Al/Zn = 1.5 at.%) metal oxide films by sol-gel spin coating method. Atomic force microscopy results indicate that the Zn1-xAlxO:Cu2O is are formed form the fibers. The surface morphology of the films is found to depend on the concentration of Cu2O. The optical constants such as band gap, Urbach energy, refractive index, extinction coefficient and dielectric constants of the films were determined. The transmittance spectra shows that all the films are highly transparent. The study revealed that undoped ZnO film has direct bang gap of 3.29 eV and the optical band gap of films is increased with doping content. The hot probe measurements indicate that Zn1-xAlxO:Cu2O transparent metal oxide composite thin films exhibited p-type electrical conductivity.

  9. Growth and electrical transport properties of La 0.7 Sr 0.3 MnO 3 thin films on Sr 2 IrO 4 single crystals

    DOE PAGES

    Moon, E. J.; May, A. F.; Shafer, P.; ...

    2017-04-20

    Here, we report the physical properties of La 0.7 Sr 0.3 MnO 3 thin films on Sr 2 IrO 4 single crystals. We also deposited the manganite films using oxide molecular beam epitaxy on flux-grown (001)-oriented iridate crystals. Temperature-dependent magnetotransport and x-ray magnetic circular dichroism measurements reveal the presence of a ferromagnetic metallic ground state in the films, consistent with films grown on SrTiO 3 and La 0.3 Sr 0.7 Al 0.65 Ta 0.35 O 3 . A parallel resistance model is used to separate conduction effects within the Sr 2 IrO 4 substrate and the La 0.7 Sr 0.3more » MnO 3 thin films, revealing that the measured resistance maximum does not correspond to the manganite Curie temperature but results from a convolution of properties of the near-insulating substrate and metallic film. Furthermore, the ability to grow and characterize epitaxial perovskites on Sr 2 IrO 4 crystals enables a new route for studying magnetism at oxide interfaces in the presence of strong spin-orbit interactions.« less

  10. Properties of nanostructured undoped ZrO{sub 2} thin film electrolytes by plasma enhanced atomic layer deposition for thin film solid oxide fuel cells

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Cho, Gu Young; Noh, Seungtak; Lee, Yoon Ho

    2016-01-15

    Nanostructured ZrO{sub 2} thin films were prepared by thermal atomic layer deposition (ALD) and by plasma-enhanced atomic layer deposition (PEALD). The effects of the deposition conditions of temperature, reactant, plasma power, and duration upon the physical and chemical properties of ZrO{sub 2} films were investigated. The ZrO{sub 2} films by PEALD were polycrystalline and had low contamination, rough surfaces, and relatively large grains. Increasing the plasma power and duration led to a clear polycrystalline structure with relatively large grains due to the additional energy imparted by the plasma. After characterization, the films were incorporated as electrolytes in thin film solidmore » oxide fuel cells, and the performance was measured at 500 °C. Despite similar structure and cathode morphology of the cells studied, the thin film solid oxide fuel cell with the ZrO{sub 2} thin film electrolyte by the thermal ALD at 250 °C exhibited the highest power density (38 mW/cm{sup 2}) because of the lowest average grain size at cathode/electrolyte interface.« less

  11. Enhanced Electrochemical Performance of Fast Ionic Conductor LiTi2(PO4)3-Coated LiNi1/3Co1/3Mn1/3O2 Cathode Material.

    PubMed

    Zhang, Lu-Lu; Wang, Ji-Qing; Yang, Xue-Lin; Liang, Gan; Li, Tao; Yu, Peng-Lin; Ma, Di

    2018-04-11

    Layered LiNi 1/3 Co 1/3 Mn 1/3 O 2 (NCM333) is successfully coated by fast ionic conductor LiTi 2 (PO 4 ) 3 (LTP) via a wet chemical method. The effects of LTP on the physicochemical properties and electrochemical performance are studied. The results reveal that a highly layered structure of NCM333 can be well maintained with less cation mixing after LTP coating. LTP of about 5 nm thickness is coated on the surface of NCM333. Such an LTP coating layer can effectively suppress the side reactions between NCM333 and electrolyte but will not hinder the lithium ion transmission. As a result, LTP-coated NCM333 owns an improved capability and cyclic performance, for example, NCM333/LTP delivers an initial capacity as high as 121.0 mA h g -1 with a capacity retention ratio of 82.3% after 200 cycles at 10 C, whereas NCM333 only has an initial capacity of 120.4 mA h g -1 with a very low capacity retention ratio of 66.4%. This method of using a fast ionic conductor like LTP as a coating material may provide a simple and effective strategy to modify those electrode materials with poor cyclic performance.

  12. Checkerboard deposition of lithium manganese oxide spinel (LiMn2O4) by RF magnetron sputtering on a stainless steel in all-solid-state thin film battery

    NASA Astrophysics Data System (ADS)

    Hsueh, T. H.; Yu, Y. Q.; Jan, D. J.; Su, C. H.; Chang, S. M.

    2018-03-01

    All-solid-state thin film lithium batteries (TFLBs) are the most competitive low-power sources to be applied in various kinds of micro-electro-mechanical systems and have been draw a lot of attention in academic research. In this paper, the checkerboard deposition of all-solid-state TFLB was composed of thin film lithium metal anode, lithium phosphorus oxynitride (LiPON) solid electrolyte, and checkerboard deposition of lithium manganese oxide spinel (LiMn2O4) cathode. The LiPON and LiMn2O4 were deposited by a radio frequency magnetron sputtering system, and the lithium metal was deposited by a thermal evaporation coater. The electrochemical characterization of this lithium battery showed the first discharge capacity of 107.8 μAh and the capacity retention was achieved 95.5% after 150 charge-discharge cycles between 4.3V and 3V at a current density of 11 μA/cm2 (0.5C). Obviously, the checkerboard of thin film increased the charge exchange rate; also this lithium battery exhibited high C-rate performance, with better capacity retention of 82% at 220 μA/cm2 (10C).

  13. Pulsed photonic fabrication of nanostructured metal oxide thin films

    NASA Astrophysics Data System (ADS)

    Bourgeois, Briley B.; Luo, Sijun; Riggs, Brian C.; Adireddy, Shiva; Chrisey, Douglas B.

    2017-09-01

    Nanostructured metal oxide thin films with a large specific surface area are preferable for practical device applications in energy conversion and storage. Herein, we report instantaneous (milliseconds) photonic synthesis of three-dimensional (3-D) nanostructured metal oxide thin films through the pulsed photoinitiated pyrolysis of organometallic precursor films made by chemical solution deposition. High wall-plug efficiency-pulsed photonic irradiation (xenon flash lamp, pulse width of 1.93 ms, fluence of 7.7 J/cm2 and frequency of 1.2 Hz) is used for scalable photonic processing. The photothermal effect of subsequent pulses rapidly improves the crystalline quality of nanocrystalline metal oxide thin films in minutes. The following paper highlights pulsed photonic fabrication of 3-D nanostructured TiO2, Co3O4, and Fe2O3 thin films, exemplifying a promising new method for the low-cost and high-throughput manufacturing of nanostructured metal oxide thin films for energy applications.

  14. Facile Phase Control of Multivalent Vanadium Oxide Thin Films (V2O5 and VO2) by Atomic Layer Deposition and Postdeposition Annealing.

    PubMed

    Song, Gwang Yeom; Oh, Chadol; Sinha, Soumyadeep; Son, Junwoo; Heo, Jaeyeong

    2017-07-19

    Atomic layer deposition was adopted to deposit VO x thin films using vanadyl tri-isopropoxide {VO[O(C 3 H 7 )] 3 , VTIP} and water (H 2 O) at 135 °C. The self-limiting and purge-time-dependent growth behaviors were studied by ex situ ellipsometry to determine the saturated growth conditions for atomic-layer-deposited VO x . The as-deposited films were found to be amorphous. The structural, chemical, and optical properties of the crystalline thin films with controlled phase formation were investigated after postdeposition annealing at various atmospheres and temperatures. Reducing and oxidizing atmospheres enabled the formation of pure VO 2 and V 2 O 5 phases, respectively. The possible band structures of the crystalline VO 2 and V 2 O 5 thin films were established. Furthermore, an electrochemical response and a voltage-induced insulator-to-metal transition in the vertical metal-vanadium oxide-metal device structure were observed for V 2 O 5 and VO 2 films, respectively.

  15. Touching the theoretical capacity: synthesizing cubic LiTi2(PO4)3/C nanocomposites for high-performance lithium-ion battery.

    PubMed

    Deng, Wenjun; Wang, Xusheng; Liu, Chunyi; Li, Chang; Xue, Mianqi; Li, Rui; Pan, Feng

    2018-04-05

    A cubic LiTi2(PO4)3/C composite is successfully prepared via a simple solvothermal method and further glucose-pyrolysis treatment. The as-fabricated LTP/C material delivers an ultra-high reversible capacity of 144 mA h g-1 at 0.2C rate, which is the highest ever reported, and shows considerable performance improvement compared with before. Combining this with the stable cycling performance and high rate capability, such material has a promising future in practical application.

  16. Thermal conductivity of ZrO2-4mol%Y2O3 thin coatings by pulsed thermal imaging method

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Jang, Byung-Koog; Sun, Jiangang; Kim, Seongwon

    Thin ZrO2-4mol% Y2O3 coatings were deposited onto ZrO2 substrates by electron beam-physical vapor deposition. The coated samples revealed a feather-like columnar microstructure. The main phase of the ZrO2-4mol% Y2O3 coatings was the tetragonal phase. To evaluate the influence of the coating’s thickness on the thermal conductivity of thin ZrO2-4mol% Y2O3 coatings, the pulsed thermal imaging method was employed to obtain the thermal conductivity of the coating layer in the two-layer (coating and substrate) samples with thickness between 56 and 337 micrometers. The thermal conductivity of the coating layer was successfully evaluated and compared well with those obtained by the lasermore » flash method for similar coatings. The thermal conductivity of coatings shows an increasing tendency with an increase in the coating’s thickness.« less

  17. Vanadium oxide thin films produced by magnetron sputtering from a V2O5 target at room temperature

    NASA Astrophysics Data System (ADS)

    de Castro, Marcelo S. B.; Ferreira, Carlos L.; de Avillez, Roberto R.

    2013-09-01

    Vanadium oxide thin films were grown by RF magnetron sputtering from a V2O5 target at room temperature, an alternative route of production of vanadium oxide thin films for infrared detector applications. The films were deposited on glass substrates, in an argon-oxygen atmosphere with an oxygen partial pressure from nominal 0% to 20% of the total pressure. X-ray diffraction (XRD) and X-ray photon spectroscopy (XPS) analyses showed that the films were a mixture of several vanadium oxides (V2O5, VO2, V5O9 and V2O3), which resulted in different colors, from yellow to black, depending on composition. The electrical resistivity varied from 1 mΩ cm to more than 500 Ω cm and the thermal coefficient of resistance (TCR), varied from -0.02 to -2.51% K-1. Computational thermodynamics was used to simulate the phase diagram of the vanadium-oxygen system. Even if plasma processes are far from equilibrium, this diagram provides the range of oxygen pressures that lead to the growth of different vanadium oxide phases. These conditions were used in the present work.

  18. Structural and magnetic analysis of Cu, Co substituted NiFe2O4 thin films

    NASA Astrophysics Data System (ADS)

    Sharma, Hakikat; Bala, Kanchan; Negi, N. S.

    2016-05-01

    In the present work we prepared NiFe2O4, Ni0.95Cu0.05Fe2O4 and Ni0.94Cu0.05Co0.01 Fe2O4 thin films by metallo-organic decomposition method (MOD) using spin coating technique. The thin films were analyzed by X-ray diffractometer (XRD) and Atomic force microscope (AFM) for structural studies. The XRD patterns confirmed the ferrite phase of thin films. From AFM, we analyzed surface morphology, calculated grain size (GS) and root mean square roughness (RMSR). Room temperature magnetic properties were investigated by vibrating sample magnetometer (VSM).

  19. Effect of substrate temperature on magnetic properties of MnFe2O4 thin films

    NASA Astrophysics Data System (ADS)

    Rajagiri, Prabhu; Sahu, B. N.; Venkataramani, N.; Prasad, Shiva; Krishnan, R.

    2018-05-01

    MnFe2O4 thin films were pulsed laser deposited on to quartz substrate from room temperature (RT) to 650 °C in a pure argon environment. Temperature dependence of spontaneous magnetization (4πMS) was measured on these films from 10 K to 350 K using a vibrating sample magnetometer. Ferromagnetic resonance (FMR) study was also carried out at 300 K. The exchange stiffness constant (D) values were obtained by fitting the 4πMS data to the Bloch's equation. The D values of the films thus found decreases while the 4πMS value increases, though non-monotonically, with the increase in TS and tend to reach bulk values at TS = 650 °C. The variation in D and 4πMS values of the films are explained based on the degree of inversion and oxidation state of cations in thin films.

  20. Capacity decline of ambient temperature secondary Li-TiS2 cells

    NASA Technical Reports Server (NTRS)

    Subbarao, S.; Shen, D. H.; Huang, C.-K.; Deligiannis, F.; Halpert, G.; Peled, E.

    1990-01-01

    The main objective of the study described was to identify the causes responsible for the capacity losses observed during cycling of secondary Li-TiS2 cells. Experimental Li-TiS2 cells were fabricated and tested for their cycle life performance. The open circuit voltage of the cells was monitored during the rest period between the charging and discharging. The polarization at the Li and TiS2 electrodes was also monitored during cycling. Cycled cells were disassembled and the cathodes were analyzed by various analytical techniques. The results of the study indicate that the observed capacity loss is almost entirely due to the increased polarization of the TiS2 electrode with cycling. The electrolyte was found to degrade during cycling and the degradation products were found to deposit at the TiS2 electrode, which probably lead to the higher polarization.

  1. Structural, electronic and chemical properties of metal/oxide and oxide/oxide interfaces and thin film structures

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Lad, Robert J.

    1999-12-14

    This project focused on three different aspects of oxide thin film systems: (1) Model metal/oxide and oxide/oxide interface studies were carried out by depositing ultra-thin metal (Al, K, Mg) and oxide (MgO, AlO{sub x}) films on TiO{sub 2}, NiO and {alpha}-Al{sub 2}O{sub 3} single crystal oxide substrates. (2) Electron cyclotron resonance (ECR) oxygen plasma deposition was used to fabricate AlO{sub 3} and ZrO{sub 2} films on sapphire substrates, and film growth mechanisms and structural characteristics were investigated. (3) The friction and wear characteristics of ZrO{sub 2} films on sapphire substrates in unlubricated sliding contact were studied and correlated with filmmore » microstructure. In these studies, thin film and interfacial regions were characterized using diffraction (RHEED, LEED, XRD), electron spectroscopies (XPS, UPS, AES), microscopy (AFM) and tribology instruments (pin-on-disk, friction microprobe, and scratch tester). By precise control of thin film microstructure, an increased understanding of the structural and chemical stability of interface regions and tribological performance of ultra-thin oxide films was achieved in these important ceramic systems.« less

  2. Low-temperature, solution-processed ZrO2:B thin film: a bifunctional inorganic/organic interfacial glue for flexible thin-film transistors.

    PubMed

    Park, Jee Ho; Oh, Jin Young; Han, Sun Woong; Lee, Tae Il; Baik, Hong Koo

    2015-03-04

    A solution-processed boron-doped peroxo-zirconium oxide (ZrO2:B) thin film has been found to have multifunctional characteristics, providing both hydrophobic surface modification and a chemical glue layer. Specifically, a ZrO2:B thin film deposited on a hydrophobic layer becomes superhydrophilic following ultraviolet-ozone (UVO) treatment, whereas the same treatment has no effect on the hydrophobicity of the hydrophobic layer alone. Investigation of the ZrO2:B/hydrophobic interface layer using angle-resolved X-ray photoelectron spectroscopy (AR XPS) confirmed it to be chemically bonded like glue. Using the multifunctional nature of the ZrO2:B thin film, flexible amorphous indium oxide (In2O3) thin-film transistors (TFTs) were subsequently fabricated on a polyimide substrate along with a ZrO2:B/poly-4-vinylphenol (PVP) dielectric. An aqueous In2O3 solution was successfully coated onto the ZrO2:B/PVP dielectric, and the surface and chemical properties of the PVP and ZrO2:B thin films were analyzed by contact angle measurement, atomic force microscopy (AFM), Fourier transform infrared (FT-IR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). The surface-engineered PVP dielectric was found to have a lower leakage current density (Jleak) of 4.38 × 10(-8) A/cm(2) at 1 MV/cm, with no breakdown behavior observed up to a bending radius of 5 mm. In contrast, the electrical characteristics of the flexible amorphous In2O3 TFT such as on/off current ratio (Ion/off) and electron mobility remained similar up to 10 mm of bending without degradation, with the device being nonactivated at a bending radius of 5 mm. These results suggest that ZrO2:B thin films could be used for low-temperature, solution-processed surface-modified flexible devices.

  3. Thin film colossal dielectric constant oxide La2-xSrxNiO4: Synthesis, dielectric relaxation measurements, and electrode effects

    NASA Astrophysics Data System (ADS)

    Podpirka, Adrian; Ramanathan, Shriram

    2011-01-01

    We have successfully synthesized the colossal dielectric constant oxide La2-xSrxNiO4 in thin film form by reactive cosputtering from metallic targets and careful annealing protocols. Composition and phase purity was determined through energy dispersive spectra and x-ray diffraction, respectively. The dielectric constant exceeds values of over 20 000 up to 1 kHz and the activation energy for the frequency-independent conductivity plateau was extracted to be approximately 155 meV from 300 to 473 K, both in agreement with measurements conducted on bulk single crystals. However, unlike in single crystals, we observe early onset of relaxation in thin films indicating the crucial role of grain boundaries in influencing the dielectric response. ac conductivity at varying temperatures is analyzed within the framework of the universal dielectric law leading to an exponent of approximately 0.3, dependent on the electrode material. Impedance spectroscopy with electrodes of different work function (Pt, Pd, and Ag) was further carried out as a function of temperature and applied bias to provide mechanistic insights into the nature of the dielectric response.

  4. Electrical Performance and Reliability Improvement of Amorphous-Indium-Gallium-Zinc-Oxide Thin-Film Transistors with HfO2 Gate Dielectrics by CF4 Plasma Treatment

    PubMed Central

    Fan, Ching-Lin; Tseng, Fan-Ping; Tseng, Chiao-Yuan

    2018-01-01

    In this work, amorphous indium-gallium-zinc oxide thin-film transistors (a-IGZO TFTs) with a HfO2 gate insulator and CF4 plasma treatment was demonstrated for the first time. Through the plasma treatment, both the electrical performance and reliability of the a-IGZO TFT with HfO2 gate dielectric were improved. The carrier mobility significantly increased by 80.8%, from 30.2 cm2/V∙s (without treatment) to 54.6 cm2/V∙s (with CF4 plasma treatment), which is due to the incorporated fluorine not only providing an extra electron to the IGZO, but also passivating the interface trap density. In addition, the reliability of the a-IGZO TFT with HfO2 gate dielectric has also been improved by the CF4 plasma treatment. By applying the CF4 plasma treatment to the a-IGZO TFT, the hysteresis effect of the device has been improved and the device’s immunity against moisture from the ambient atmosphere has been enhanced. It is believed that the CF4 plasma treatment not only significantly improves the electrical performance of a-IGZO TFT with HfO2 gate dielectric, but also enhances the device’s reliability. PMID:29772767

  5. Epitaxial Ba2IrO4 thin-films grown on SrTiO3 substrates by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Nichols, J.; Korneta, O. B.; Terzic, J.; Cao, G.; Brill, J. W.; Seo, S. S. A.

    2014-03-01

    We have synthesized epitaxial Ba2IrO4 (BIO) thin-films on SrTiO3 (001) substrates by pulsed laser deposition and studied their electronic structure by dc-transport and optical spectroscopic experiments. We have observed that BIO thin-films are insulating but close to the metal-insulator transition boundary with significantly smaller transport and optical gap energies than its sister compound, Sr2IrO4. Moreover, BIO thin-films have both an enhanced electronic bandwidth and electronic-correlation energy. Our results suggest that BIO thin-films have great potential for realizing the interesting physical properties predicted in layered iridates.

  6. Surface-area-controlled synthesis of porous TiO2 thin films for gas-sensing applications

    NASA Astrophysics Data System (ADS)

    Park, Jae Young; Kim, Ho-hyoung; Rana, Dolly; Jamwal, Deepika; Katoch, Akash

    2017-03-01

    Surface-area-controlled porous TiO2 thin films were prepared via a simple sol-gel chemical route, and their gas-sensing properties were thoroughly investigated in the presence of typical oxidizing NO2 gas. The surface area of TiO2 thin films was controlled by developing porous TiO2 networked by means of controlling the TiO2-to-TTIP (titanium isopropoxide, C12H28O4Ti) molar ratio, where TiO2 nanoparticles of size ˜20 nm were used. The sensor’s response was found to depend on the surface area of the TiO2 thin films. The porous TiO2 thin-film sensor with greater surface area was more sensitive than those of TiO2 thin films with lesser surface area. The improved sensing ability was ascribed to the porous network formed within the thin films by TiO2 sol. Our results show that surface area is a key parameter for obtaining superior gas-sensing performance; this provides important guidelines for preparing and using porous thin films for gas-sensing applications.

  7. Effects of O2 plasma post-treatment on ZnO: Ga thin films grown by H2O-thermal ALD

    NASA Astrophysics Data System (ADS)

    Lee, Yueh-Lin; Chuang, Jia-Hao; Huang, Tzu-Hsuan; Ho, Chong-Long; Wu, Meng-Chyi

    2013-03-01

    Transparent conducting oxides have been widely employed in optoelectronic devices using the various deposition methods such as sputtering, thermal evaporator, and e-gun evaporator technologies.1-3 In this work, gallium doped zinc oxide (ZnO:Ga) thin films were grown on glass substrates via H2O-thermal atomic layer deposition (ALD) at different deposition temperatures. ALD-GZO thin films were constituted as a layer-by-layer structure by stacking zinc oxides and gallium oxides. Diethylzinc (DEZ), triethylgallium (TEG) and H2O were used as zinc, gallium precursors and oxygen source, respectively. Furthermore, we investigated the influences of O2 plasma post-treatment power on the surface morphology, electrical and optical property of ZnO:Ga films. As the result of O2 plasma post-treatment, the characteristics of ZnO:Ga films exhibit a smooth surface, low resistivity, high carrier concentration, and high optical transmittance in the visible spectrum. However, the transmittance decreases with O2 plasma power in the near- and mid-infrared regions.

  8. Heterojunction solar cell with 6% efficiency based on an n-type aluminum-gallium-oxide thin film and p-type sodium-doped Cu2O sheet

    NASA Astrophysics Data System (ADS)

    Minami, Tadatsugu; Nishi, Yuki; Miyata, Toshihiro

    2015-02-01

    In this paper, we describe efforts to enhance the efficiency of Cu2O-based heterojunction solar cells fabricated with an aluminum-gallium-oxide (Al-Ga-O) thin film as the n-type layer and a p-type sodium (Na)-doped Cu2O (Cu2O:Na) sheet prepared by thermally oxidizing copper sheets. The optimal Al content [X; Al/(Ga + Al) atomic ratio] of an AlX-Ga1-X-O thin-film n-type layer was found to be approximately 2.5 at. %. The optimized resistivity was approximately 15 Ω cm for n-type AlX-Ga1-X-O/p-type Cu2O:Na heterojunction solar cells. A MgF2/AZO/Al0.025-Ga0.975-O/Cu2O:Na heterojunction solar cell with 6.1% efficiency was fabricated using a 60-nm-thick n-type oxide thin-film layer and a 0.2-mm-thick Cu2O:Na sheet with the optimized resistivity.

  9. Band diagram and rate analysis of thin film spinel LiMn 2O 4 formed by electrochemical conversion of ALD-grown MnO

    DOE PAGES

    Young, Matthias J.; Schnabel, Hans-Dieter; Holder, Aaron M.; ...

    2016-09-22

    Nanoscale spinel lithium manganese oxide is of interest as a high-rate cathode material for advanced battery technologies among other electrochemical applications. In this work, the synthesis of ultrathin films of spinel lithium manganese oxide (LiMn 2O 4) between 20 and 200 nm in thickness by room-temperature electrochemical conversion of MnO grown by atomic layer deposition (ALD) is demonstrated. The charge storage properties of LiMn 2O 4 thin films in electrolytes containing Li +, Na +, K +, and Mg 2+ are investigated. A unified electrochemical band-diagram (UEB) analysis of LiMn 2O 4 informed by screened hybrid density functional theory calculationsmore » is also employed to expand on existing understanding of the underpinnings of charge storage and stability in LiMn 2O 4. It is shown that the incorporation of Li + or other cations into the host manganese dioxide spinel structure (λ-MnO 2) stabilizes electronic states from the conduction band which align with the known redox potentials of LiMn 2O 4. Furthermore, the cyclic voltammetry experiments demonstrate that up to 30% of the capacity of LiMn 2O 4 arises from bulk electronic charge-switching which does not require compensating cation mass transport. As a result, the hybrid ALD-electrochemical synthesis, UEB analysis, and unique charge storage mechanism described here provide a fundamental framework to guide the development of future nanoscale electrode materials for ion-incorporation charge storage.« less

  10. Electrical and optical properties of nitrogen doped SnO{sub 2} thin films deposited on flexible substrates by magnetron sputtering

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Fang, Feng, E-mail: fangfeng@seu.edu.cn; Zhang, Yeyu; Wu, Xiaoqin

    2015-08-15

    Graphical abstract: The best SnO{sub 2}:N TCO film: about 80% transmittance and 9.1 × 10{sup −4} Ω cm. - Highlights: • Nitrogen-doped tin oxide film was deposited on PET by RF-magnetron sputtering. • Effects of oxygen partial pressure on the properties of thin films were investigated. • For SnO{sub 2}:N film, visible light transmittance was 80% and electrical resistivity was 9.1 × 10{sup −4} Ω cm. - Abstract: Nitrogen-doped tin oxide (SnO{sub 2}:N) thin films were deposited on flexible polyethylene terephthalate (PET) substrates at room temperature by RF-magnetron sputtering. Effects of oxygen partial pressure (0–4%) on electrical and optical propertiesmore » of thin films were investigated. Experimental results showed that SnO{sub 2}:N films were amorphous state, and O/Sn ratios of SnO{sub 2}:N films were deviated from the standard stoichiometry 2:1. Optical band gap of SnO{sub 2}:N films increased from approximately 3.10 eV to 3.42 eV as oxygen partial pressure increased from 0% to 4%. For SnO{sub 2}:N thin films deposited on PET, transmittance was about 80% in the visible light region. The best transparent conductive oxide (TCO) deposited on flexible PET substrates was SnO{sub 2}:N thin films preparing at 2% oxygen partial pressure, the transmittance was about 80% and electrical conductivity was about 9.1 × 10{sup −4} Ω cm.« less

  11. Sb:SnO2 thin films-synthesis and characterization

    NASA Astrophysics Data System (ADS)

    Bhadrapriya B., C.; Varghese, Anitta Rose; Amarendra, G.; Hussain, Shamima

    2018-04-01

    Transparent thin films of antimony doped SnO2 have been synthesized and characterized using optical spectroscopy, XRD, RAMAN and FESEM. The band gap of Sb doped tin oxide thin film samples were found to vary from 3.26 eV to 3.7 eV. The XRD peaks showed prominent rutile SnO2 peaks with diminished intensity due to antimony doping. A wide band in the range 550-580 cm-1 was observed in raman spectra and is a feature of nano-sized SnO2. SEM images showed flower-like structures on thin film surface, a characteristic feature of antimony.

  12. Depolarization currents in Al 2O 3 and MgAl 2O 4 oxides

    NASA Astrophysics Data System (ADS)

    Carvalhaes, R. P. M.; Rocha, M. S.; de Souza, S. S.; Blak, A. R.

    2004-06-01

    In the present work, dipole defects in γ-irradiated and thermally treated samples of Al 2O 3 and MgAl 2O 4 oxides are investigated, applying the thermally stimulated depolarisation currents technique (TSDC). The TSDC spectra of MgAl 2O 4 doped with Fe 2+, Fe 3+, Co 2+, Cr 3+ and Mn 2+ show four bands at 130 K, 160 K, 250 K and 320 K, and the spectra of Al 2O 3 doped with Mg 2+, Cr 3+ and Fe 3+ show bands between 230 K and 260 K. It has been observed that the bands at 130 K, 160 K and 250 K in MgAl 2O 4 spinel and that the 230 K and 240 K bands in Al 2O 3 are related to dipole defects. The other bands are possibly related to different types of charge storage mechanisms (space-charge and interfacial polarisation) or deal with distributions in activation energies and/or in relaxation times. A thermal decrease of the TSDC bands for heat treatments above 1000 K has been observed. In MgAl 2O 4 spinel, the 250 K band could be recovered after γ-irradiation and the two dipole peaks in Al 2O 3 were partially recovered. Thermal treatments affect the dipole aggregation processes in both oxides. Optical absorption (AO) results indicate that the presence of bands of water molecules in the infrared region obstructs the appearance of the TSDC bands in both Al 2O 3 and MgAl 2O 4. The 250 K peak in MgAl 2O 4 was correlated to V-type centres and the 250 K peak in Al 2O 3 to a substitutional Mg 2+ ion near a trapped hole localised on an adjacent oxygen ion.

  13. Ultra-thin silicon oxide layers on crystalline silicon wafers: Comparison of advanced oxidation techniques with respect to chemically abrupt SiO2/Si interfaces with low defect densities

    NASA Astrophysics Data System (ADS)

    Stegemann, Bert; Gad, Karim M.; Balamou, Patrice; Sixtensson, Daniel; Vössing, Daniel; Kasemann, Martin; Angermann, Heike

    2017-02-01

    Six advanced oxidation techniques were analyzed, evaluated and compared with respect to the preparation of high-quality ultra-thin oxide layers on crystalline silicon. The resulting electronic and chemical SiO2/Si interface properties were determined by a combined x-ray photoemission (XPS) and surface photovoltage (SPV) investigation. Depending on the oxidation technique, chemically abrupt SiO2/Si interfaces with low densities of interface states were fabricated on c-Si either at low temperatures, at short times, or in wet-chemical environment, resulting in each case in excellent interface passivation. Moreover, the beneficial effect of a subsequent forming gas annealing (FGA) step for the passivation of the SiO2/Si interface of ultra-thin oxide layers has been proven. Chemically abrupt SiO2/Si interfaces have been shown to generate less interface defect states.

  14. Comparative study of structural, optical and impedance measurements on V{sub 2}O{sub 5} and V-Ce mixed oxide thin films

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Malini, D. Rachel; Sanjeeviraja, C., E-mail: sanjeeviraja@rediffmail.com

    Vanadium pentoxide (V{sub 2}O{sub 5}) and Vanadium-Cerium mixed oxide thin films at different molar ratios of V{sub 2}O{sub 5} and CeO{sub 2} have been deposited at 200 W rf power by rf planar magnetron sputtering in pure argon atmosphere. The structural and optical properties were studied by taking X-ray diffraction and transmittance and absorption spectra respectively. The amorphous thin films show an increase in transmittance and optical bandgap with increase in CeO{sub 2} content in as-prepared thin films. The impedance measurements for as-deposited thin films show an increase in electrical conductivity with increase in CeO{sub 2} material.

  15. Low-temperature fabrication of an HfO2 passivation layer for amorphous indium-gallium-zinc oxide thin film transistors using a solution process.

    PubMed

    Hong, Seonghwan; Park, Sung Pyo; Kim, Yeong-Gyu; Kang, Byung Ha; Na, Jae Won; Kim, Hyun Jae

    2017-11-24

    We report low-temperature solution processing of hafnium oxide (HfO 2 ) passivation layers for amorphous indium-gallium-zinc oxide (a-IGZO) thin-film transistors (TFTs). At 150 °C, the hafnium chloride (HfCl 4 ) precursor readily hydrolyzed in deionized (DI) water and transformed into an HfO 2 film. The fabricated HfO 2 passivation layer prevented any interaction between the back surface of an a-IGZO TFT and ambient gas. Moreover, diffused Hf 4+ in the back-channel layer of the a-IGZO TFT reduced the oxygen vacancy, which is the origin of the electrical instability in a-IGZO TFTs. Consequently, the a-IGZO TFT with the HfO 2 passivation layer exhibited improved stability, showing a decrease in the threshold voltage shift from 4.83 to 1.68 V under a positive bias stress test conducted over 10,000 s.

  16. High-Quality TiS2 For Li/TiS2 Cells

    NASA Technical Reports Server (NTRS)

    Huang, Chen-Kuo; Surampudi, Subbarao; Shen, David H.; Delgiannis, Fotios; Halpert, Gerald

    1992-01-01

    Modified process for synthesis of battery-grade titanium sulfide (TiS2) yields substantially improved material for Li/TiS2 electrochemical cells. Includes all-vapor-phase reaction between sulfur and titanium. Product less dense and more homogeneous, consists of smaller particles of higher crystalline quality, and purer. Cells have high cathode utilization and long cycle life performance. Expected to find applications in rechargeable lithium batteries for spacecraft, military equipment, telecommunication systems, automobiles, and consumer products.

  17. Synthesis and characterization of magnesium aluminate (MgAl2O4) spinel (MAS) thin films

    NASA Astrophysics Data System (ADS)

    Ahmad, Syed Muhammad; Hussain, Tousif; Ahmad, Riaz; Siddiqui, Jamil; Ali, Dilawar

    2018-01-01

    In a quest to identify more economic routes for synthesis of magnesium aluminate (MgAl2O4) spinel (MAS) thin films, dense plasma focus device was used with multiple plasma focus shots. Structural, bonding between composite films, surface morphological, compositional and hardness properties of MAS thin films were investigated by using x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive x-rays (EDX) analysis and Vickers micro hardness test respectively. In XRD graph, the presence of MgAl2O4 diffraction peaks in crystallographic orientations (222), (400) and (622) pointed out the successful formation of polycrystalline thin films of MgAl2O4 with face centered cubic structure. The FTIR spectrums showed a major common transmittance band at 697.95 cm-1 which belongs to MgAl2O4. SEM micrographs illustrated a mesh type, granular and multi layers microstructures with significant melting effects. EDX spectrum confirmed the existence of magnesium, oxygen and aluminum in MAS films. A common increasing behavior in micro-hardness of composite MgAl2O4 films by increasing number of plasma focus shots was found.

  18. Fabrication of band gap engineered nanostructured tri-metallic (Mn-Co-Ti) oxide thin films

    NASA Astrophysics Data System (ADS)

    Mansoor, Muhammad Adil; Yusof, Farazila Binti; Nay-Ming, Huang

    2018-04-01

    In continuation of our previous studies on photoelectrochemical (PEC) properties of titanium based composite oxide thin films, an effort is made to develop thin films of 1:1:2 manganese-cobalt-titanium oxide composite, Mn2O3-Co2O3-4TiO2 (MCT), using Co(OAc)2 and a bimetallic manganese-titanium complex, [Mn2Ti4(TFA)8(THF)6(OH)4(O)2].0.4THF (1), where OAc = acetato, TFA = trifluoroacetato and THF = tetrahydrofuran, via aerosol-assisted chemical vapour deposition (AACVD) technique. The X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and energy dispersive X-ray (EDX) spectroscopic analyses confirmed formation of thin film of Mn2O3-Co2O3-4TiO2 composite material with uniformly distributed agglomerated particles. The average size of 39.5 nm, of the particles embedded inside agglomerates, was estimated by Scherer's equation. Further, UV-Vis spectroscopy was used to estimate the band gap of 2.62 eV for MCT composite thin film.

  19. Dye sensitized solar cell applications of CdTiO3-TiO2 composite thin films deposited from single molecular complex

    NASA Astrophysics Data System (ADS)

    Ehsan, Muhammad Ali; Khaledi, Hamid; Pandikumar, Alagarsamy; Huang, Nay Ming; Arifin, Zainudin; Mazhar, Muhammad

    2015-10-01

    A heterobimetallic complex [Cd2Ti4(μ-O)6(TFA)8(THF)6]·1.5THF (1) (TFA=trifluoroacetato, THF=tetrahydrofuran) comprising of Cd:Ti (1:2) ratio was synthesized by a chemical reaction of cadmium (II) acetate with titanium (IV) isopropoxide and triflouroacetic acid in THF. The stoichiometry of (1) was recognized by single crystal X-ray diffraction, spectroscopic and elemental analyses. Thermal studies revealed that (1) neatly decomposes at 450 °C to furnish 1:1 ratio of cadmium titanate:titania composite oxides material. The thin films of CdTiO3-TiO2 composite oxides were deposited at 550 °C on fluorine doped tin oxide coated conducting glass substrate in air ambient. The micro-structure, crystallinity, phase identification and chemical composition of microspherical architectured CdTiO3-TiO2 composite thin film have been determined by scanning electron microscopy, X-ray diffraction, Raman spectroscopy and energy dispersive X-ray analysis. The scope of composite thin film having band gap of 3.1 eV was explored as photoanode for dye-sensitized solar cell application.

  20. Nanocrystalline Pd:NiFe2O4 thin films: A selective ethanol gas sensor

    NASA Astrophysics Data System (ADS)

    Rao, Pratibha; Godbole, R. V.; Bhagwat, Sunita

    2016-10-01

    In this work, Pd:NiFe2O4 thin films were investigated for the detection of reducing gases. These films were fabricated using spray pyrolysis technique and characterized using X-ray diffraction (XRD) to confirm the crystal structure. The surface morphology was studied using scanning electron microscopy (SEM). Magnetization measurements were carried out using SQUID VSM, which shows ferrimagnetic behavior of the samples. These thin film sensors were tested against methanol, ethanol, hydrogen sulfide and liquid petroleum gas, where they were found to be more selective to ethanol. The fabricated thin film sensors exhibited linear response signal for all the gases with concentrations up to 5 w/o Pd. Reduction in optimum operating temperature and enhancement in response was also observed. Pd:NiFe2O4 thin films exhibited faster response and recovery characteristic. These sensors have potential for industrial applications because of their long-term stability, low power requirement and low production cost.

  1. Nonenzymatic detection of glucose using BaCuO2 thin layer

    NASA Astrophysics Data System (ADS)

    Ito, Takeshi; Asada, Tsuyoshi; Asai, Naoto; Shimizu, Tomohiro; Shingubara, Shoso

    2017-01-01

    A BaCuO2 thin layer was deposited on a glassy carbon electrode and used for the direct oxidation of glucose. The crystalline, electrochemical, and physicochemical properties that depend on the deposition temperature and deposition time were studied. X-ray diffraction (XRD) analysis showed that the thin layer was amorphous even at 400 °C. The current density of the glucose oxidation using the thin layer deposited at 200 °C was higher than those at other deposition temperatures. Under this condition, the current density increased with the glucose concentration and deposition time. These results indicate that a BaCuO2 thin layer has potential for measuring the blood glucose level without enzymes.

  2. Spin Seebeck effect in insulating epitaxial γ-Fe2O3 thin films

    NASA Astrophysics Data System (ADS)

    Jiménez-Cavero, P.; Lucas, I.; Anadón, A.; Ramos, R.; Niizeki, T.; Aguirre, M. H.; Algarabel, P. A.; Uchida, K.; Ibarra, M. R.; Saitoh, E.; Morellón, L.

    2017-02-01

    We report the fabrication of high crystal quality epitaxial thin films of maghemite (γ-Fe2O3), a classic ferrimagnetic insulating iron oxide. Spin Seebeck effect (SSE) measurements in γ-Fe2O3/Pt bilayers as a function of sample preparation conditions and temperature yield a SSE coefficient of 0.5(1) μV/K at room temperature. Dependence on temperature allows us to estimate the magnon diffusion length in maghemite to be in the range of tens of nanometers, in good agreement with that of conducting iron oxide magnetite (Fe3O4), establishing the relevance of spin currents of magnonic origin in magnetic iron oxides.

  3. Electro-optical properties of the metal oxide-carbon thin film system of CdO-LCC

    NASA Astrophysics Data System (ADS)

    Kokshina, A. V.; Smirnov, A. V.; Razina, A. G.

    2016-08-01

    This article presents the results of a study electrical and optical properties of the thin film system of CdO-LCC. Cadmium oxide films were obtained by method of thermal oxidation. CdO-LCC thin film system was produced by applying on a CdO film a linear chain carbon film in thickness of 100 nm using the ion-plasma method, after which the obtained system was annealed. The studies showed that the obtained CdO-LCC films are quite transparent in the visible region; it has polycrystalline structure, thickness around 300 nm, the band gap to 2.3 eV. The obtained thin film system has photosensitive properties.

  4. Plasma assisted facile synthesis of vanadium oxide (V3O7) nanostructured thin films

    NASA Astrophysics Data System (ADS)

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

    2018-05-01

    Vanadium oxides nanostructured thin films are synthesized using plasma assisted sublimation process. The effect of temperatures on growth of V2O5 and V3O7 thin films is studied. Scanning electron micrographs shows different morphologies are obtained at different temperatures i.e. at 450 °C nano cubes-like structures are obtained, whereas at 550 °C and 650 °C nanorods are obtained. Sample deposited at 450 °C is entirely composed of V2O5 and sample at higher temperatures are composed of mixed phase of vanadium oxides i.e. V2O5 and V3O7. As temperature increased, so the content of V3O7 in the sample is increased as confirmed by XRD and Raman analyses.

  5. Y1Ba2Cu3O(6+delta) growth on thin Y-enhanced SiO2 buffer layers on silicon

    NASA Technical Reports Server (NTRS)

    Robin, T.; Mesarwi, A.; Wu, N. J.; Fan, W. C.; Espoir, L.; Ignatiev, A.; Sega, R.

    1991-01-01

    SiO2 buffer layers as thin as 2 nm have been developed for use in the growth of Y1Ba2Cu3O(6+delta) thin films on silicon substrates. The SiO2 layers are formed through Y enhancement of silicon oxidation, and are highly stoichiometric. Y1Ba2Cu3O(6+delta) film growth on silicon with thin buffer layers has shown c orientation and Tc0 = 78 K.

  6. Growth and Characteristic of Amorphous Nano-Granular TeO2-V2O5-NiO Thin Films

    NASA Astrophysics Data System (ADS)

    Hosseinzadeh, Sh.; Rahmati, A.; Bidadi, H.

    2016-12-01

    TeO2-V2O5-NiO thin films were deposited using thermal evaporation from 40TeO2-(60-y)V2O5-yNiO (y=0-30mol%) target. Structural analysis of the films was identified by X-ray diffractometry (XRD) and scanning electron microscopy (SEM). The amorphous TeO2-V2O5-NiO films have nanosized clear grain structure and sharp grain boundaries. DC conductivity and current-voltage (I-V) characteristic of TeO2-V2O5-NiO thin films were measured in the temperature range of 300-423K. As nickel oxide (NiO) content increases, the DC conductivity decreases up to two orders in value (10-9-10-11Sṡcm-1). Temperature dependence of conductivity is described using the small polaron hopping (SPH) model as well. Poole-Frenkel effect is observed at high external electric field. The optical absorption spectra of the TeO2-V2O5-NiO thin films were recorded in the wavelength range of 380-1100nm. The absorption coefficient revealed bandgap shrinkage (3.01-2.3eV) and band tail widening, due to an increase in NiO content. Energy dispersive X-ray spectroscopy (EDX) was used to determine elemental composition. In TeO2-V2O5-NiO thin films, the NiO content is around fifth of the initial target.

  7. CoFe2O4-TiO2 and CoFe2O4-ZnO thin film nanostructures elaborated from colloidal chemistry and atomic layer deposition.

    PubMed

    Clavel, Guylhaine; Marichy, Catherine; Willinger, Marc-Georg; Ravaine, Serge; Zitoun, David; Pinna, Nicola

    2010-12-07

    CoFe(2)O(4)-TiO(2) and CoFe(2)O(4)-ZnO nanoparticles/film composites were prepared from directed assembly of colloidal CoFe(2)O(4) in a Langmuir-Blodgett monolayer and atomic layer deposition (ALD) of an oxide (TiO(2) or ZnO). The combination of these two methods permits the use of well-defined nanoparticles from colloidal chemistry, their assembly on a large scale, and the control over the interface between a ferrimagnetic material (CoFe(2)O(4)) and a semiconductor (TiO(2) or ZnO). Using this approach, architectures can be assembled with a precise control from the Angstrom scale (ALD) to the micrometer scale (Langmuir-Blodgett film). The resulting heterostructures present well-calibrated thicknesses. Electron microscopy and magnetic measurement studies give evidence that the size of the nanoparticles and their intrinsic magnetic properties are not altered by the various steps involved in the synthesis process. Therefore, the approach is suitable to obtain a layered composite with a quasi-monodisperse layer of ferrimagnetic nanoparticles embedded in an ultrathin film of semiconducting material.

  8. On stoichiometry and intermixing at the spinel/perovskite interface in CoFe2O4/BaTiO3 thin films.

    PubMed

    Tileli, Vasiliki; Duchamp, Martial; Axelsson, Anna-Karin; Valant, Matjaz; Dunin-Borkowski, Rafal E; Alford, Neil McN

    2015-01-07

    The performance of complex oxide heterostructures depends primarily on the interfacial coupling of the two component structures. This interface character inherently varies with the synthesis method and conditions used since even small composition variations can alter the electronic, ferroelectric, or magnetic functional properties of the system. The focus of this article is placed on the interface character of a pulsed laser deposited CoFe2O4/BaTiO3 thin film. Using a range of state-of-the-art transmission electron microscopy methodologies, the roles of substrate morphology, interface stoichiometry, and cation intermixing are determined on the atomic level. The results reveal a surprisingly uneven BaTiO3 substrate surface formed after the film deposition and Fe atom incorporation in the top few monolayers inside the unit cell of the BaTiO3 crystal. Towards the CoFe2O4 side, a disordered region extending several nanometers from the interface was revealed and both Ba and Ti from the substrate were found to diffuse into the spinel layer. The analysis also shows that within this somehow incompatible composite interface, a different phase is formed corresponding to the compound Ba2Fe3Ti5O15, which belongs to the ilmenite crystal structure of FeTiO3 type. The results suggest a chemical activity between these two oxides, which could lead to the synthesis of complex engineered interfaces.

  9. Structural and magnetic analysis of Cu, Co substituted NiFe{sub 2}O{sub 4} thin films

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Sharma, Hakikat; Bala, Kanchan; Negi, N. S.

    2016-05-23

    In the present work we prepared NiFe{sub 2}O{sub 4}, Ni{sub 0.95}Cu{sub 0.05}Fe{sub 2}O{sub 4} and Ni{sub 0.94}Cu{sub 0.05}Co{sub 0.01} Fe{sub 2}O{sub 4} thin films by metallo-organic decomposition method (MOD) using spin coating technique. The thin films were analyzed by X-ray diffractometer (XRD) and Atomic force microscope (AFM) for structural studies. The XRD patterns confirmed the ferrite phase of thin films. From AFM, we analyzed surface morphology, calculated grain size (GS) and root mean square roughness (RMSR). Room temperature magnetic properties were investigated by vibrating sample magnetometer (VSM).

  10. Processing of La(1.8)Sr(0.2)CuO4 and YBa2Cu3O7 superconducting thin films by dual-ion-beam sputtering

    NASA Astrophysics Data System (ADS)

    Madakson, P.; Cuomo, J. J.; Yee, D. S.; Roy, R. A.; Scilla, G.

    1988-03-01

    High-quality La(1.8)Sr(0.2)CuO4 and YBa2Cu3O7 superconducting thin films, with zero resistance at 88 K, have been made by dual-ion-beam sputtering of metal and oxide targets at elevated temperatures. The films are about 1.0 micron thick and are single phase after annealing. The substrates investigated are Nd-YAP, MgO, SrF2, Si, CaF2, ZrO2-(9 pct)Y2O3, BaF2, Al2O3, and SrTiO3. Characterization of the films was carried out using Rutherford backscattering spectroscopy, resistivity measurements, TEM, X-ray diffraction, and SIMS. Substrate/film interaction was observed in every case. This generally involves diffusion of the substrate into the film, which is accompanied by, for example, the replacement of Ba by Sr in the YBa2Cu2O7 structure, in the case of SrTiO3 substrate. The best substrates were those that did not significantly diffuse into the film and which did not react chemically with the film.

  11. Dye sensitized solar cell applications of CdTiO{sub 3}–TiO{sub 2} composite thin films deposited from single molecular complex

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ehsan, Muhammad Ali; Khaledi, Hamid; Pandikumar, Alagarsamy

    2015-10-15

    A heterobimetallic complex [Cd{sub 2}Ti{sub 4}(μ-O){sub 6}(TFA){sub 8}(THF){sub 6}]·1.5THF (1) (TFA=trifluoroacetato, THF=tetrahydrofuran) comprising of Cd:Ti (1:2) ratio was synthesized by a chemical reaction of cadmium (II) acetate with titanium (IV) isopropoxide and triflouroacetic acid in THF. The stoichiometry of (1) was recognized by single crystal X-ray diffraction, spectroscopic and elemental analyses. Thermal studies revealed that (1) neatly decomposes at 450 °C to furnish 1:1 ratio of cadmium titanate:titania composite oxides material. The thin films of CdTiO{sub 3}–TiO{sub 2} composite oxides were deposited at 550 °C on fluorine doped tin oxide coated conducting glass substrate in air ambient. The micro-structure, crystallinity,more » phase identification and chemical composition of microspherical architectured CdTiO{sub 3}–TiO{sub 2} composite thin film have been determined by scanning electron microscopy, X-ray diffraction, Raman spectroscopy and energy dispersive X-ray analysis. The scope of composite thin film having band gap of 3.1 eV was explored as photoanode for dye-sensitized solar cell application. - Graphical abstarct: Microspherical designed CdTiO{sub 3}–TiO{sub 2} composite oxides photoanode film has been fabricated from single source precursor [Cd{sub 2}Ti{sub 4}(μ-O){sub 6}(TFA){sub 8}(THF){sub 6}]·1.5THF via aerosol assisted chemical vapor deposition technique for dye sensitized solar cell application. - Highlights: • Synthesis and characterization of a heterobimetallic Cd–Ti complex. • Fabrication of CdTiO{sub 3}–TiO{sub 2} thin film photoelectrode. • Application as dye sensitized photoanode for solar application.« less

  12. Magnetoelectricity in CoFe2O4 nanocrystal-P(VDF-HFP) thin films

    PubMed Central

    2013-01-01

    Transition metal ferrites such as CoFe2O4, possessing a large magnetostriction coefficient and high Curie temperature (Tc > 600 K), are excellent candidates for creating magnetic order at the nanoscale and provide a pathway to the fabrication of uniform particle-matrix films with optimized potential for magnetoelectric coupling. Here, a series of 0–3 type nanocomposite thin films composed of ferrimagnetic cobalt ferrite nanocrystals (8 to 18 nm) and a ferroelectric/piezoelectric polymer poly(vinylidene fluoride-co-hexafluoropropene), P(VDF-HFP), were prepared by multiple spin coating and cast coating over a thickness range of 200 nm to 1.6 μm. We describe the synthesis and structural characterization of the nanocrystals and composite films by XRD, TEM, HRTEM, STEM, and SEM, as well as dielectric and magnetic properties, in order to identify evidence of cooperative interactions between the two phases. The CoFe2O4 polymer nanocomposite thin films exhibit composition-dependent effective permittivity, loss tangent, and specific saturation magnetization (Ms). An enhancement of the effective permittivity and saturation magnetization of the CoFe2O4-P(VDF-HFP) films was observed and directly compared with CoFe2O4-polyvinylpyrrolidone, a non-ferroelectric polymer-based nanocomposite prepared by the same method. The comparison provided evidence for the observation of a magnetoelectric effect in the case of CoFe2O4-P(VDF-HFP), attributed to a magnetostrictive/piezoelectric interaction. An enhancement of Ms up to +20.7% was observed at room temperature in the case of the 10 wt.% CoFe2O4-P(VDF-HFP) sample. PMID:24004499

  13. Ultrahigh broadband photoresponse of SnO2 nanoparticle thin film/SiO2/p-Si heterojunction.

    PubMed

    Ling, Cuicui; Guo, Tianchao; Lu, Wenbo; Xiong, Ya; Zhu, Lei; Xue, Qingzhong

    2017-06-29

    The SnO 2 /Si heterojunction possesses a large band offset and it is easy to control the transportation of carriers in the SnO 2 /Si heterojunction to realize high-response broadband detection. Therefore, we investigated the potential of the SnO 2 nanoparticle thin film/SiO 2 /p-Si heterojunction for photodetectors. It is demonstrated that this heterojunction shows a stable, repeatable and broadband photoresponse from 365 nm to 980 nm. Meanwhile, the responsivity of the device approaches a high value in the range of 0.285-0.355 A W -1 with the outstanding detectivity of ∼2.66 × 10 12 cm H 1/2 W -1 and excellent sensitivity of ∼1.8 × 10 6 cm 2 W -1 , and its response and recovery times are extremely short (<0.1 s). This performance makes the device stand out among previously reported oxide or oxide/Si based photodetectors. In fact, the photosensitivity and detectivity of this heterojunction are an order of magnitude higher than that of 2D material based heterojunctions such as (Bi 2 Te 3 )/Si and MoS 2 /graphene (photosensitivity of 7.5 × 10 5 cm 2 W -1 and detectivity of ∼2.5 × 10 11 cm H 1/2 W -1 ). The excellent device performance is attributed to the large Fermi energy difference between the SnO 2 nanoparticle thin film and Si, SnO 2 nanostructure, oxygen vacancy defects and thin SiO 2 layer. Consequently, practical highly-responsive broadband PDs may be actualized in the future.

  14. Dilute electrodeposition of TiO2 and ZnO thin film memristors on Cu substrate

    NASA Astrophysics Data System (ADS)

    Fauzi, F. B.; Ani, M. H.; Herman, S. H.; Mohamed, M. A.

    2018-03-01

    Memristor has become one of the alternatives to replace the current memory technologies. Fabrication of titanium dioxide, TiO2 memristor has been extensively studied by using various deposition methods. However, recently more researches have been done to explore the compatibility of other transition metal oxide, TMO such as zinc oxide, ZnO to be used as the active layer of the memristor. This paper highlights the simple and easy-control electrodeposition to deposit titanium, Ti and zinc, Zn thin film at room temperature and subsequent thermal oxidation at 600 °C. Gold, Au was then sputtered as top electrode to create metal-insulator-metal, MIM sandwich of Au/TiO2-Cu2O-CuO/Cu and Au/ZnO-Cu2O-CuO/Cu memristors. The structural, morphological and memristive properties were characterized using Field Emission Scanning Electron Microscopy, FESEM, X-Ray Diffraction, XRD and current-voltage, I-V measurement. Both Au/TiO2-Cu2O-CuO/Cu and Au/ZnO-Cu2O-CuO/Cu memristivity were identified by the pinched hysteresis loop with resistive ratio of 1.2 and 1.08 respectively. Empirical study on diffusivity of Ti4+, Zn2+ and O2‑ ions in both metal oxides show that the metal vacancies were formed, thus giving rise to its memristivity. The electrodeposited Au/TiO2-Cu2O-CuO/Cu and Au/ZnO-Cu2O-CuO/Cu memristors demonstrate comparable performances to previous studies using other methods.

  15. Transparent conducting ZnO-CdO mixed oxide thin films grown by the sol-gel method.

    PubMed

    Pathak, Trilok K; Rajput, Jeevitesh K; Kumar, Vinod; Purohit, L P; Swart, H C; Kroon, R E

    2017-02-01

    Mixed oxides of zinc and cadmium with different proportions were deposited on ordinary glass substrates using the sol-gel spin coating method under optimized deposition conditions using zinc acetate dihydrate and cadmium acetate dihydrate as precursors. X-ray diffraction patterns confirmed the polycrystalline nature of the films. A combination of cubic CdO and hexagonal wurtzite ZnO phases was observed. The oxidation states of Zn, Cd and O in the deposited films were determined by X-ray photoelectron spectroscopic studies. Surface morphology was studied by scanning electron microscopy and atomic force microscopy. The compositional analysis of the thin films was studied by secondary ion mass spectroscopy. The transmittance of the thin films was measured in the range 300-800nm and the optical bandgap was calculated using Tauc's plot method. The bandgap decreased from 3.15eV to 2.15eV with increasing CdO content. The light emission properties of the ZnO:CdO thin films were studied by photoluminescence spectra recorded at room temperature. The current-voltage characteristics were also assessed and showed ohmic behaviour. The resistance decreased with increasing CdO content. Copyright © 2016 Elsevier Inc. All rights reserved.

  16. The Chemical Vapor Deposition of Thin Metal Oxide Films

    NASA Astrophysics Data System (ADS)

    Laurie, Angus Buchanan

    1990-01-01

    Chemical vapor deposition (CVD) is an important method of preparing thin films of materials. Copper (II) oxide is an important p-type semiconductor and a major component of high T_{rm c} superconducting oxides. By using a volatile copper (II) chelate precursor, copper (II) bishexafluoroacetylacetonate, it has been possible to prepare thin films of copper (II) oxide by low temperature normal pressure metalorganic chemical vapor deposition. In the metalorganic CVD (MOCVD) production of oxide thin films, oxygen gas saturated with water vapor has been used mainly to reduce residual carbon and fluorine content. This research has investigated the influence of water-saturated oxygen on the morphology of thin films of CuO produced by low temperature chemical vapor deposition onto quartz, magnesium oxide and cubic zirconia substrates. ZnO is a useful n-type semiconductor material and is commonly prepared by the MOCVD method using organometallic precursors such as dimethyl or diethylzinc. These compounds are difficult to handle under atmospheric conditions. In this research, thin polycrystalline films of zinc oxide were grown on a variety of substrates by normal pressure CVD using a zinc chelate complex with zinc(II) bishexafluoroacetylacetonate dihydrate (Zn(hfa)_2.2H _2O) as the zinc source. Zn(hfa) _2.2H_2O is not moisture - or air-sensitive and is thus more easily handled. By operating under reduced-pressure conditions (20-500 torr) it is possible to substantially reduce deposition times and improve film quality. This research has investigated the reduced-pressure CVD of thin films of CuO and ZnO. Sub-micron films of tin(IV) oxide (SnO _2) have been grown by normal pressure CVD on quartz substrates by using tetraphenyltin (TPT) as the source of tin. All CVD films were characterized by X-ray powder diffraction (XRPD), scanning electron microscopy (SEM) and electron probe microanalysis (EPMA).

  17. Preparation of LiMn{sub 2}O{sub 4} cathode thin films for thin film lithium secondary batteries by a mist CVD process

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Tadanaga, Kiyoharu, E-mail: tadanaga@chem.osakafu-u.ac.jp; Yamaguchi, Akihiro; Sakuda, Atsushi

    2014-05-01

    Highlights: • LiMn{sub 2}O{sub 4} thin films were prepared by using the mist CVD process. • An aqueous solution of lithium and manganese acetates is used for the precursor solution. • The cell with the LiMn{sub 2}O{sub 4} thin films exhibited a capacity of about 80 mAh/g. • The cell showed good cycling performance during 10 cycles. - Abstract: LiMn{sub 2}O{sub 4} cathode thin films for thin film lithium secondary batteries were prepared by using so-called the “mist CVD process”, employing an aqueous solution of lithium acetate and manganese acetate, as the source of Li and Mn, respectively. The aqueousmore » solution of starting materials was ultrasonically atomized to form mist particles, and mists were transferred by nitrogen gas to silica glass substrate to form thin films. FE-SEM observation revealed that thin films obtained by this process were dense and smooth, and thin films with a thickness of about 750 nm were obtained. The electrochemical cell with the thin films obtained by sintering at 700 °C exhibited a capacity of about 80 mAh/g, and the cell showed good cycling performance during 10 cycles.« less

  18. Study of SiO{sub 2}/4H-SiC interface nitridation by post-oxidation annealing in pure nitrogen gas

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Chanthaphan, Atthawut, E-mail: chanthaphan@asf.mls.eng.osaka-u.ac.jp; Hosoi, Takuji, E-mail: hosoi@mls.eng.osaka-u.ac.jp; Shimura, Takayoshi

    An alternative and effective method to perform interface nitridation for 4H-SiC metal-oxide-semiconductor (MOS) devices was developed. We found that the high-temperature post-oxidation annealing (POA) in N{sub 2} ambient was beneficial to incorporate a sufficient amount of nitrogen atoms directly into thermal SiO{sub 2}/SiC interfaces. Although N{sub 2}-POA was ineffective for samples with thick thermal oxide layers, interface nitridation using N{sub 2}-POA was achieved under certain conditions, i.e., thin SiO{sub 2} layers (< 15 nm) and high annealing temperatures (>1350°C). Electrical characterizations of SiC-MOS capacitors treated with high-temperature N{sub 2}-POA revealed the same evidence of slow trap passivation and fast trapmore » generation that occurred in NO-treated devices fabricated with the optimized nitridation conditions.« less

  19. TiN/Al2O3/ZnO gate stack engineering for top-gate thin film transistors by combination of post oxidation and annealing

    NASA Astrophysics Data System (ADS)

    Kato, Kimihiko; Matsui, Hiroaki; Tabata, Hitoshi; Takenaka, Mitsuru; Takagi, Shinichi

    2018-04-01

    Control of fabrication processes for a gate stack structure with a ZnO thin channel layer and an Al2O3 gate insulator has been examined for enhancing the performance of a top-gate ZnO thin film transistor (TFT). The Al2O3/ZnO interface and the ZnO layer are defective just after the Al2O3 layer formation by atomic layer deposition. Post treatments such as plasma oxidation, annealing after the Al2O3 deposition, and gate metal formation (PMA) are promising to improve the interfacial and channel layer qualities drastically. Post-plasma oxidation effectively reduces the interfacial defect density and eliminates Fermi level pinning at the Al2O3/ZnO interface, which is essential for improving the cut-off of the drain current of TFTs. A thermal effect of post-Al2O3 deposition annealing at 350 °C can improve the crystalline quality of the ZnO layer, enhancing the mobility. On the other hand, impacts of post-Al2O3 deposition annealing and PMA need to be optimized because the annealing can also accompany the increase in the shallow-level defect density and the resulting electron concentration, in addition to the reduction in the deep-level defect density. The development of the interfacial control technique has realized the excellent TFT performance with a large ON/OFF ratio, steep subthreshold characteristics, and high field-effect mobility.

  20. Hydrogen incorporation by plasma treatment gives mesoporous black TiO 2 thin films with visible photoelectrochemical water oxidation activity

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Islam, Syed Z.; Reed, Allen; Nagpure, Suraj

    In this work, we use neutron reflectometry (NR) to investigate the roles of hydrogen in plasma treated hydrogen doped mesoporous black titania thin films in their visible light absorption and enhanced photoactivity for water oxidation. The cubic ordered mesoporous TiO 2 thin films are prepared by a surfactant-templated sol-gel method and are treated with hydrogen plasma, an approach hypothesized to capitalize on the high degree of disorder in the material and the high energy of the plasma species to achieve efficient hydrogen doping. UV-vis absorbance spectra indicate that H 2 plasma treatment makes TiO 2 films black, with broad-spectrum enhancementmore » of visible light absorption, and XPS analysis shows peak for Ti 3+ state in treated films. The presence of hydrogen in black mesoporous titania (H-TiO 2) films is confirmed by the scattering length density (SLD) profiles obtained from neutron reflectometry measurements. The H-TiO 2 shows ca. 28 times and 8 times higher photocurrent for photoelectrochemical water oxidation compared to undoped TiO 2 films under UV (365 nm) and blue (455 nm) LED irradiation, respectively. These findings provide the first direct evidence that the dramatic change in visible light absorbance of H-treated black TiO 2 is accompanied by significant hydrogen uptake and not just Ti 3+ generation or surface disordering.« less

  1. Hydrogen incorporation by plasma treatment gives mesoporous black TiO 2 thin films with visible photoelectrochemical water oxidation activity

    DOE PAGES

    Islam, Syed Z.; Reed, Allen; Nagpure, Suraj; ...

    2017-10-26

    In this work, we use neutron reflectometry (NR) to investigate the roles of hydrogen in plasma treated hydrogen doped mesoporous black titania thin films in their visible light absorption and enhanced photoactivity for water oxidation. The cubic ordered mesoporous TiO 2 thin films are prepared by a surfactant-templated sol-gel method and are treated with hydrogen plasma, an approach hypothesized to capitalize on the high degree of disorder in the material and the high energy of the plasma species to achieve efficient hydrogen doping. UV-vis absorbance spectra indicate that H 2 plasma treatment makes TiO 2 films black, with broad-spectrum enhancementmore » of visible light absorption, and XPS analysis shows peak for Ti 3+ state in treated films. The presence of hydrogen in black mesoporous titania (H-TiO 2) films is confirmed by the scattering length density (SLD) profiles obtained from neutron reflectometry measurements. The H-TiO 2 shows ca. 28 times and 8 times higher photocurrent for photoelectrochemical water oxidation compared to undoped TiO 2 films under UV (365 nm) and blue (455 nm) LED irradiation, respectively. These findings provide the first direct evidence that the dramatic change in visible light absorbance of H-treated black TiO 2 is accompanied by significant hydrogen uptake and not just Ti 3+ generation or surface disordering.« less

  2. Hydrogen incorporation by plasma treatment gives mesoporous black TiO 2 thin films with visible photoelectrochemical water oxidation activity

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Islam, Syed Z.; Reed, Allen; Nagpure, Suraj

    2018-05-01

    In this work, we use neutron reflectometry (NR) to investigate the roles of hydrogen in plasma treated hydrogen doped mesoporous black titania thin films in their visible light absorption and enhanced photoactivity for water oxidation. The cubic ordered mesoporous TiO2 thin films are prepared by a surfactant-templated sol-gel method and are treated with hydrogen plasma, an approach hypothesized to capitalize on the high degree of disorder in the material and the high energy of the plasma species to achieve efficient hydrogen doping. UV-vis absorbance spectra indicate that H2 plasma treatment makes TiO2 films black, with broad-spectrum enhancement of visible lightmore » absorption, and XPS analysis shows peak for Ti3+ state in treated films. The presence of hydrogen in black mesoporous titania (H-TiO2) films is confirmed by the scattering length density (SLD) profiles obtained from neutron reflectometry measurements. The H-TiO2 shows ca. 28 times and 8 times higher photocurrent for photoelectrochemical water oxidation compared to undoped TiO2 films under UV (365 nm) and blue (455 nm) LED irradiation, respectively. These findings provide the first direct evidence that the dramatic change in visible light absorbance of H-treated black TiO2 is accompanied by significant hydrogen uptake and not just Ti3+ generation or surface disordering.« less

  3. Growth and characterization of sol-gel derived CuGaO2 semiconductor thin films for UV photodetector application

    NASA Astrophysics Data System (ADS)

    Tsay, Chien-Yie; Chen, Ching-Lien

    2017-06-01

    In this study, a p-type wide-bandgap oxide semiconductor CuGaO2 thin film was grown on quartz substrate by sol-gel method. The authors report the influence of annealing temperature on the phase transformation, structural features, and electrical properties of sol-gel derived Cu-Ga-O thin films. At relatively low annealing temperatures (≤900 °C), the films are a mixture of CuGa2O4, CuGaO2, and CuO phases. At relatively high annealing temperatures (≥925 °C), the majority phase in the films is delafossite CuGaO2. All as-prepared Cu-Ga-O thin films exhibited p-type conductivity, as confirmed by Hall measurements. The mean electrical resistivity of the Cu-Ga-O films decreased from 3.54×104 Ω-cm to 1.35×102 Ω-cm and then increased slightly to 3.51×102 Ω-cm when the annealing temperature was increased from 850 °C to 950 °C. We found that annealing the Cu-based oxide thin films at 925 °C produced nearly phase-pure CuGaO2 thin films with good densification. Such thin films exhibited the best electrical properties: a mean electrical resistivity of 1.35×102 Ω-cm, and a mean hole concentration of 1.60×1016 cm-3. In addition, we also fabricated and characterized MSM-type CuGaO2 UV photodetectors on quartz substrates.

  4. Epitaxial integration of CoFe2O4 thin films on Si (001) surfaces using TiN buffer layers

    NASA Astrophysics Data System (ADS)

    Prieto, Pilar; Marco, José F.; Prieto, José E.; Ruiz-Gomez, Sandra; Perez, Lucas; del Real, Rafael P.; Vázquez, Manuel; de la Figuera, Juan

    2018-04-01

    Epitaxial cobalt ferrite thin films with strong in-plane magnetic anisotropy have been grown on Si (001) substrates using a TiN buffer layer. The epitaxial films have been grown by ion beam sputtering using either metallic, CoFe2, or ceramic, CoFe2O4, targets. X-ray diffraction (XRD) and Rutherford spectrometry (RBS) in random and channeling configuration have been used to determine the epitaxial relationship CoFe2O4 [100]/TiN [100]/Si [100]. Mössbauer spectroscopy, in combination with XRD and RBS, has been used to determine the composition and structure of the cobalt ferrite thin films. The TiN buffer layer induces a compressive strain in the cobalt ferrite thin films giving rise to an in-plane magnetic anisotropy. The degree of in-plane anisotropy depends on the lattice mismatch between CoFe2O4 and TiN, which is larger for CoFe2O4 thin films grown on the reactive sputtering process with ceramic targets.

  5. Optimization of Al2O3/TiO2 nanolaminate thin films prepared with different oxide ratios, for use in organic light-emitting diode encapsulation, via plasma-enhanced atomic layer deposition.

    PubMed

    Kim, Lae Ho; Jeong, Yong Jin; An, Tae Kyu; Park, Seonuk; Jang, Jin Hyuk; Nam, Sooji; Jang, Jaeyoung; Kim, Se Hyun; Park, Chan Eon

    2016-01-14

    Encapsulation is essential for protecting the air-sensitive components of organic light-emitting diodes (OLEDs), such as the active layers and cathode electrodes. Thin film encapsulation approaches based on an oxide layer are suitable for flexible electronics, including OLEDs, because they provide mechanical flexibility, the layers are thin, and they are easy to prepare. This study examined the effects of the oxide ratio on the water permeation barrier properties of Al2O3/TiO2 nanolaminate films prepared by plasma-enhanced atomic layer deposition. We found that the Al2O3/TiO2 nanolaminate film exhibited optimal properties for a 1 : 1 atomic ratio of Al2O3/TiO2 with the lowest water vapor transmission rate of 9.16 × 10(-5) g m(-2) day(-1) at 60 °C and 90% RH. OLED devices that incorporated Al2O3/TiO2 nanolaminate films prepared with a 1 : 1 atomic ratio showed the longest shelf-life, in excess of 2000 hours under 60 °C and 90% RH conditions, without forming dark spots or displaying edge shrinkage.

  6. Preparation of epitaxial TlBa2Ca2Cu3O9 high Tc thin films on LaAlO3 (100) substrates

    NASA Astrophysics Data System (ADS)

    Piehler, A.; Reschauer, N.; Spreitzer, U.; Ströbel, J. P.; Schönberger, R.; Renk, K. F.; Saemann-Ischenko, G.

    1994-09-01

    Epitaxial TlBa2Ca2Cu3O9 high Tc thin films were prepared on LaAlO3 (100) substrates by a combination of laser ablation and thermal evaporation of thallium oxide. X-ray diffraction patterns of θ-2θ scans showed that the films consisted of highly c axis oriented TlBa2Ca2Cu3O9. φ scan measurements revealed an epitaxial growth of the TlBa2Ca2Cu3O9 thin films on the LaAlO3 (100) substrates. Ac inductive measurements indicated the onset of superconductivity at 110 K. At 6 K, the critical current density was 4×106 A/cm2 in zero magnetic field and 6×105 A/cm2 at a magnetic field of 3 T parallel to the c axis.

  7. Tailoring the nickel nanoparticles anchored on the surface of Fe3O4@SiO2 spheres for nanocatalysis.

    PubMed

    Ding, Lei; Zhang, Min; Zhang, Yanwei; Yang, Jinbo; Zheng, Jing; Hayat, Tasawar; Alharbi, Njud S; Xu, Jingli

    2017-08-25

    Herein, we report an efficient and universal strategy for synthesizing a unique triple-shell structured Fe 3 O 4 @SiO 2 @C-Ni hybrid composite. Firstly, the Fe 3 O 4 cores were synthesized by hydrothermal reaction, and sequentially coated with SiO 2 and a thin layer of nickel-ion-doped resin-formaldehyde (RF-Ni 2+ ) using an extended Stöber method. This was followed by carbonization to produce the Fe 3 O 4 @SiO 2 @C-Ni nanocomposites with metallic nickel nanoparticles embedded in an RF-derived thin graphic carbon layer. Interestingly, the thin SiO 2 spacer layer between RF-Ni 2+ and Fe 3 O 4 plays a critical role on adjusting the size and density of the nickel nanoparticles on the surface of Fe 3 O 4 @SiO 2 nanospheres. The detailed tailoring mechanism is explicitly discussed, and it is shown that the iron oxide core can react with the nickel nanoparticles without the SiO 2 spacer layer, and the size and density of the nickel nanoparticles can be effectively controlled when the SiO 2 layer exits. The multifunctional composites exhibit a significantly enhanced catalytic performance in the reduction of 4-nitrophenol (4-NP).

  8. Lateral assembly of oxidized graphene flakes into large-scale transparent conductive thin films with a three-dimensional surfactant 4-sulfocalix[4]arene

    PubMed Central

    Sundramoorthy, Ashok K.; Wang, Yilei; Wang, Jing; Che, Jianfei; Thong, Ya Xuan; Lu, Albert Chee W.; Chan-Park, Mary B.

    2015-01-01

    Graphene is a promising candidate material for transparent conductive films because of its excellent conductivity and one-carbon-atom thickness. Graphene oxide flakes prepared by Hummers method are typically several microns in size and must be pieced together in order to create macroscopic films. We report a macro-scale thin film fabrication method which employs a three-dimensional (3-D) surfactant, 4-sulfocalix[4]arene (SCX), as a lateral aggregating agent. After electrochemical exfoliation, the partially oxidized graphene (oGr) flakes are dispersed with SCX. The SCX forms micelles, which adsorb on the oGr flakes to enhance their dispersion, also promote aggregation into large-scale thin films under vacuum filtration. A thin oGr/SCX film can be shaved off from the aggregated oGr/SCX cake by immersing the cake in water. The oGr/SCX thin-film floating on the water can be subsequently lifted from the water surface with a substrate. The reduced oGr (red-oGr) films can be as thin as 10−20 nm with a transparency of >90% and sheet resistance of 890 ± 47 kΩ/sq. This method of electrochemical exfoliation followed by SCX-assisted suspension and hydrazine reduction, avoids using large amounts of strong acid (unlike Hummers method), is relatively simple and can easily form a large scale conductive and transparent film from oGr/SCX suspension. PMID:26040436

  9. Experimental Study of Acid Treatment Toward Characterization of Structural, Optical, and Morphological Properties of TiO2-SnO2 Composite Thin Film

    NASA Astrophysics Data System (ADS)

    Fajar, M. N.; Hidayat, R.; Triwikantoro; Endarko

    2018-04-01

    The TiO2-SnO2 thin film with single and double-layer structure has successfully synthesized on FTO (Fluorine-doped Tin Oxide) substrate using the screen printing technique. The structural, optical, and morphological properties of the film were investigated by XRD, UV-Vis, and SEM, respectively. The results showed that the single and double-layer structure of TiO2-SnO2 thin film has mixed phase with a strong formation of casseritte phase. The acid treatment effect on TiO2-SnO2 thin film decreases the peak intensity of anatase phase formation and thin film’s absorbance values. The morphological study is also revealed that the single layer TiO2-SnO2 thin film had a more porous nature and decreased particle size distribution after acid treatment, while the double-layer TiO2-SnO2 thin film Eroded due to acid treatment.

  10. Precautions toward XTEM of Si3N4/SiO2

    NASA Technical Reports Server (NTRS)

    Ogbuji, Linus U. J. T.

    1991-01-01

    Severe difficulties are encountered in the preparation of oxidized Si3N4 specimens for XTEM transmission electromicroscopic inspection, in virtue of the extreme difference between Si3N4 and SiO2 mechanical properties. Attention is presently given to a preparation method in which an overlayer of the nitride is always occluded; this protects the oxide through most of the thinning that specimen preparation entails. An XTEM image of the oxide/nitride interface is presented.

  11. β-Ga2O3 versus ε-Ga2O3: Control of the crystal phase composition of gallium oxide thin film prepared by metal-organic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Zhuo, Yi; Chen, Zimin; Tu, Wenbin; Ma, Xuejin; Pei, Yanli; Wang, Gang

    2017-10-01

    Gallium oxide thin films of β and ε phase were grown on c-plane sapphire using metal-organic chemical vapor deposition and the phase compositions were analyzed using X-ray diffraction. The epitaxial phase diagram was constructed as a function of the growth temperature and VI/III ratio. A low growth temperature and low VI/III ratio were beneficial for the formation of hexagonal-type ε-Ga2O3. Further structure analysis revealed that the epitaxial relationship between ε-Ga2O3 and c-plane sapphire is ε-Ga2O3 (0001) || Al2O3 (0001) and ε-Ga2O3 || Al2O3 . The structural evolution of the mixed-phase sample during film thickening was investigated. By reducing the growth rate, the film evolved from a mixed phase to the energetically favored ε phase. Based on these results, a Ga2O3 thin film with a phase-pure ε-Ga2O3 upper layer was successfully obtained.

  12. Microfabrication of SrRuO3 thin films on various oxide substrates using LaAlO3/BaOx sacrificial bilayers

    NASA Astrophysics Data System (ADS)

    Harada, Takayuki; Tsukazaki, Atsushi

    2018-02-01

    Oxides provide various fascinating physical properties that could find use in future device applications. However, the physical properties of oxides are often affected by formation of oxygen vacancies during device fabrication processes. In this study, to develop a damage-free patterning process for oxides, we focus on a lift-off process using a sacrificial template layer, by which we can pattern oxide thin films without severe chemical treatment or plasma bombardment. As oxides need high thin-film growth temperature, a sacrificial template needs to be made of thermally stable and easily etchable materials. To meet these requirements, we develop a sacrificial template with a carefully designed bilayer structure. Combining a thermally and chemically stable LaAlO3 and a water-soluble BaOx, we fabricated a LaAlO3/BaOx sacrificial bilayer. The patterned LaAlO3/BaOx sacrificial bilayers were prepared on oxide substrates by room-temperature pulsed laser deposition and standard photolithography process. The structure of the sacrificial bilayer can be maintained even in rather tough conditions needed for oxide thin film growth: several hundred degrees Celsius under high oxygen pressure. Indeed, the LaAlO3/BaOx bilayer is easily removable by sonication in water. We applied the lift-off method using the LaAlO3/BaOx sacrificial bilayer to a representative oxide conductor SrRuO3 and fabricated micron-scale Hall-bar devices. The SrRuO3 channels with the narrowest line width of 5 μm exhibit an almost identical transport property to that of the pristine film, evidencing that the developed process is beneficial for patterning oxides. We show that the LaAlO3/BaOx lift-off process is applicable to various oxide substrates: SrTiO3, MgO, and Al2O3. The new versatile patterning process will expand the range of application of oxide thin films in electronic and photonic devices.

  13. Comparative analysis of breakdown mechanism in thin SiO2 oxide films in metal-oxide-semiconductor structures under the action of heavy charged particles and a pulsed voltage

    NASA Astrophysics Data System (ADS)

    Zinchenko, V. F.; Lavrent'ev, K. V.; Emel'yanov, V. V.; Vatuev, A. S.

    2016-02-01

    Regularities in the breakdown of thin SiO2 oxide films in metal-oxide-semiconductors structures of power field-effect transistors under the action of single heavy charged particles and a pulsed voltage are studied experimentally. Using a phenomenological approach, we carry out comparative analysis of physical mechanisms and energy criteria of the SiO2 breakdown in extreme conditions of excitation of the electron subsystem in the subpicosecond time range.

  14. Determination of oxygen diffusion kinetics during thin film ruthenium oxidation

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Coloma Ribera, R., E-mail: r.colomaribera@utwente.nl; Kruijs, R. W. E. van de; Yakshin, A. E.

    2015-08-07

    In situ X-ray reflectivity was used to reveal oxygen diffusion kinetics for thermal oxidation of polycrystalline ruthenium thin films and accurate determination of activation energies for this process. Diffusion rates in nanometer thin RuO{sub 2} films were found to show Arrhenius behaviour. However, a gradual decrease in diffusion rates was observed with oxide growth, with the activation energy increasing from about 2.1 to 2.4 eV. Further exploration of the Arrhenius pre-exponential factor for diffusion process revealed that oxidation of polycrystalline ruthenium joins the class of materials that obey the Meyer-Neldel rule.

  15. Enhanced magnetoelectric response in 2-2 bilayer 0.50Pb(Ni1/3Nb2/3)O3-0.35PbTiO3-0.15PbZrO3/NiFe2O4 thin films

    NASA Astrophysics Data System (ADS)

    Ade, Ramesh; Sambasiva, V.; Kolte, Jayant; Karthik, T.; Kulkarni, Ajit R.; Venkataramani, N.

    2018-03-01

    In this work, room temperature magnetoelectric (ME) properties of 0.50Pb(Ni1/3Nb2/3)O3-0.35PbTiO3-0.15PbZrO3 (PNNZT)/NiFe2O4 (NFO) 2-2 bilayer thin films grown on Pt/Ti/SiO2/Si substrate, using pulsed laser deposition technique, are reported. Structural studies confirm single phase PNNZT/NFO 2-2 bilayer structure formation. PNNZT/NFO 2-2 bilayer thin film shows a maximum ME voltage coefficient (α E ) of ~0.70 V cm-1. Oe-1 at a frequency of 1 kHz. The present study reveals that PNNZT/NFO bilayer thin film can be a potential candidate for technological applications.

  16. Bandgap-Engineered Zinc-Tin-Oxide Thin Films for Ultraviolet Sensors.

    PubMed

    Cheng, Tien-Hung; Chang, Sheng-Po; Chang, Shoou-Jinn

    2018-07-01

    Zinc-tin-oxide thin-film transistors were prepared by radio frequency magnetron co-sputtering, while an identical zinc-tin-oxide thin film was deposited simultaneously on a clear glass substrate to facilitate measurements of the optical properties. When we adjusted the deposition power of ZnO and SnO2, the bandgap of the amorphous thin film was dominated by the deposition power of SnO2. Since the thin-film transistor has obvious absorption in the ultraviolet region owing to the wide bandgap, the drain current increases with the generation of electron-hole pairs. As part of these investigations, a zinc-tin-oxide thin-film transistor has been fabricated that appears to be very promising for ultraviolet applications.

  17. Preparation and Ferroelectric Property of (100)-ORIENTED Ca0.4Sr0.6Bi4Ti4O15 Thin Film on Pt/Ti/SiO2/Si Substrate

    NASA Astrophysics Data System (ADS)

    Fan, Suhua; Che, Quande; Zhang, Fengqing

    The (100)-oriented Ca0.4Sr0.6Bi4Ti4O15(C0.4S0.6BTi) thin film was successfully prepared by a sol-gel method on Pt/Ti/SiO2/Si substrate. The orientation and formation of thin films under different annealing schedules were studied using XRD and SEM. XRD analysis indicated that (100)-oriented C0.4S0.6BTi thin film with degree of orientation of I(200)/I(119) = 1.60 was prepared by preannealing the film at 400°C for 3 min followed by rapid thermal annealing at 800°C for 5 min. SEM analysis further indicated that the (100)-oriented C0.4S0.6BTi thin film with a thickness of about 800 nm was mainly composed of equiaxed grains. The remanent polarization and coercive field of the film were 16.1 μC/cm2 and 85 kV/cm, respectively.

  18. Twin-induced phase transition from β-Ga2O3 to α-Ga2O3 in Ga2O3 thin films

    NASA Astrophysics Data System (ADS)

    Choi, Byeongdae; Allabergenov, Bunyod; Lyu, Hong-Kun; Lee, Seong Eui

    2018-06-01

    We deposited a 300-nm-thick Ga2O3 thin film on an amorphous SiO2/Si substrate via pulsed laser deposition. X-ray diffraction patterns revealed the formation of β-Ga2O3 phase at a substrate temperature of 700 °C. X-ray photoelectron spectra indicated that the degree of oxidation increased after annealing at 700 °C. Further annealings at higher temperatures led to a transition of the β-Ga2O3 phase to the α-Ga2O3 phase; this transition was caused by the twin structure formed during the crystallinity improvement process. In addition, we discuss the mechanism of the transition from the β phase to the α phase in the β-Ga2O3 thin films.

  19. Electrochemical properties of thin films of V2O5 doped with TiO2

    NASA Astrophysics Data System (ADS)

    Moura, E. A.; Cholant, C. M.; Balboni, R. D. C.; Westphal, T. M.; Lemos, R. M. J.; Azevedo, C. F.; Gündel, A.; Flores, W. H.; Gomez, J. A.; Ely, F.; Pawlicka, A.; Avellaneda, C. O.

    2018-08-01

    The paper presents a systematic study of the electrochromic properties of thin films of V2O5:TiO2 for a possible utilization as counter-electrode in electrochromic devices. The V2O5:TiO2 thin films were prepared by the sol-gel process and deposited on a substrate of fluorine-tin oxide transparent electrode (FTO) using the dip coating technique and heat treatment at 350 °C for 30 min. The films were characterized by chronocoulometry, cyclic voltammetry (CV), UV-Vis, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), atomic force microscopy (AFM), profilometry, and X-ray diffraction (XRD). The best results were obtained for the film of V2O5 with 7.5 mol% of TiO2, which presented highest ion storage capacity of ∼106 mC cm-2 and redox reversibility of 1. The diffusion of the Li+ ions into the thin films was modeled by solving Fick equations with appropriate boundary conditions for a plane sheet geometry. Besides that, these films showed optical modulation of 35% at 633 nm after coloration and bleaching. The XRD patterns revealed that the films have an orthorhombic crystal structure; the AFM and the profilometry confirmed roughness and thickness of 16.76 and 617 nm, respectively.

  20. Thickness measurement of a thin hetero-oxide film with an interfacial oxide layer by X-ray photoelectron spectroscopy

    NASA Astrophysics Data System (ADS)

    Kim, Kyung Joong; Lee, Seung Mi; Jang, Jong Shik; Moret, Mona

    2012-02-01

    The general equation Tove = L cos θ ln(Rexp/R0 + 1) for the thickness measurement of thin oxide films by X-ray photoelectron spectroscopy (XPS) was applied to a HfO2/SiO2/Si(1 0 0) as a thin hetero-oxide film system with an interfacial oxide layer. The contribution of the thick interfacial SiO2 layer to the thickness of the HfO2 overlayer was counterbalanced by multiplying the ratio between the intensity of Si4+ from a thick SiO2 film and that of Si0 from a Si(1 0 0) substrate to the intensity of Si4+ from the HfO2/SiO2/Si(1 0 0) film. With this approximation, the thickness levels of the HfO2 overlayers showed a small standard deviation of 0.03 nm in a series of HfO2 (2 nm)/SiO2 (2-6 nm)/Si(1 0 0) films. Mutual calibration with XPS and transmission electron microscopy (TEM) was used to verify the thickness of HfO2 overlayers in a series of HfO2 (1-4 nm)/SiO2 (3 nm)/Si(1 0 0) films. From the linear relation between the thickness values derived from XPS and TEM, the effective attenuation length of the photoelectrons and the thickness of the HfO2 overlayer could be determined.

  1. Effects of channel thickness on oxide thin film transistor with double-stacked channel layer

    NASA Astrophysics Data System (ADS)

    Lee, Kimoon; Kim, Yong-Hoon; Yoon, Sung-Min; Kim, Jiwan; Oh, Min Suk

    2017-11-01

    To improve the field effect mobility and control the threshold voltage ( V th ) of oxide thin film transistors (TFTs), we fabricated the oxide TFTs with double-stacked channel layers which consist of thick Zn-Sn-O (ZTO) and very thin In-Zn-O (IZO) layers. We investigated the effects of the thickness of thin conductive layer and the conductivity of thick layer on oxide TFTs with doublestacked channel layer. When we changed the thickness of thin conductive IZO channel layer, the resistivity values were changed. This resistivity of thin channel layer affected on the saturation field effect mobility and the off current of TFTs. In case of the thick ZTO channel layer which was deposited by sputtering in Ar: O2 = 10: 1, the device showed better performances than that which was deposited in Ar: O2 = 1: 1. Our TFTs showed high mobility ( μ FE ) of 40.7 cm2/Vs and V th of 4.3 V. We assumed that high mobility and the controlled V th were caused by thin conductive IZO layer and thick stable ZTO layer. Therefore, this double-stacked channel structure can be very promising way to improve the electrical characteristics of various oxide thin film transistors.

  2. Characterization of ZnO:SnO{sub 2} (50:50) thin film deposited by RF magnetron sputtering technique

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Cynthia, S. R.; Sanjeeviraja, C.; Ponmudi, S.

    2016-05-06

    Zinc oxide (ZnO) and tin oxide (SnO{sub 2}) thin films have attracted significant interest recently for use in optoelectronic application such as solar cells, flat panel displays, photonic devices, laser diodes and gas sensors because of their desirable electrical and optical properties and wide band gap. In the present study, thin films of ZnO:SnO{sub 2} (50:50) were deposited on pre-cleaned microscopic glass substrate by RF magnetron sputtering technique. The substrate temperature and RF power induced changes in structural, surface morphological, compositional and optical properties of the films have been studied.

  3. Synthesis and catalytic activity of electrospun NiO/NiCo2O4 nanotubes for CO and acetaldehyde oxidation

    NASA Astrophysics Data System (ADS)

    Kim, Il Hee; Lee, Hyerim; Yu, Areum; Jeong, Jae Hwan; Lee, Youngmi; Kim, Myung Hwa; Lee, Chongmok; Dok Kim, Young

    2018-04-01

    NiO/NiCo2O4 nanotubes with a diameter of approximately 100 nm are synthesized using Ni and Co precursors via electro-spinning and subsequent calcination processes. The tubular structure is confirmed via transmission electron microscopy imaging, whereas the structures and elemental compositions of the nanotubes are determined using x-ray diffraction, energy dispersive x-ray spectroscopy, and x-ray photoelectron spectroscopy. N2 adsorption isotherm data reveal that the surface of the nanotubes consists of micropores, thereby resulting in a significantly higher surface area (˜20 m2 g-1) than expected for a flat-surface structure (<15 m2 g-1). Herein, we present a study of the catalytic activity of our novel NiO/NiCo2O4 nanotubes for CO and acetaldehyde oxidation. The catalytic activity of NiO/NiCo2O4 is superior to Pt below 100 °C for CO oxidation. For acetaldehyde oxidation, the total oxidation activity of NiO/NiCo2O4 for acetaldehyde is comparable with that of Pt. Coexistence of many under-coordinated Co and Ni active sites in our structure is suggested be related to the high catalytic activity. It is suggested that our novel NiO/NiCo2O4 tubular structures with surface microporosity can be of interest for a variety of applications, including the catalytic oxidation of harmful gases.

  4. Synthesis and catalytic activity of electrospun NiO/NiCo2O4 nanotubes for CO and acetaldehyde oxidation.

    PubMed

    Kim, Il Hee; Lee, Hyerim; Yu, Areum; Jeong, Jae Hwan; Lee, Youngmi; Kim, Myung Hwa; Lee, Chongmok; Kim, Young Dok

    2018-04-27

    NiO/NiCo 2 O 4 nanotubes with a diameter of approximately 100 nm are synthesized using Ni and Co precursors via electro-spinning and subsequent calcination processes. The tubular structure is confirmed via transmission electron microscopy imaging, whereas the structures and elemental compositions of the nanotubes are determined using x-ray diffraction, energy dispersive x-ray spectroscopy, and x-ray photoelectron spectroscopy. N 2 adsorption isotherm data reveal that the surface of the nanotubes consists of micropores, thereby resulting in a significantly higher surface area (∼20 m 2 g -1 ) than expected for a flat-surface structure (<15 m 2 g -1 ). Herein, we present a study of the catalytic activity of our novel NiO/NiCo 2 O 4 nanotubes for CO and acetaldehyde oxidation. The catalytic activity of NiO/NiCo 2 O 4 is superior to Pt below 100 °C for CO oxidation. For acetaldehyde oxidation, the total oxidation activity of NiO/NiCo 2 O 4 for acetaldehyde is comparable with that of Pt. Coexistence of many under-coordinated Co and Ni active sites in our structure is suggested be related to the high catalytic activity. It is suggested that our novel NiO/NiCo 2 O 4 tubular structures with surface microporosity can be of interest for a variety of applications, including the catalytic oxidation of harmful gases.

  5. Self-organization in complex oxide thin films: from 2D to 0D nanostructures of SrRuO3 and CoCr2O4

    NASA Astrophysics Data System (ADS)

    Sánchez, F.; Lüders, U.; Herranz, G.; Infante, I. C.; Fontcuberta, J.; García-Cuenca, M. V.; Ferrater, C.; Varela, M.

    2005-05-01

    We report here on the controlled fabrication of nanostructures of varied dimensionality by self-organization processes in the heteroepitaxial growth of SrRuO3 (SRO) and CoCr2O4 (CCO) films. The surface of SRO films on SrTiO3(001) substrates can show extremely smooth terraces (2D objects) separated by atomic steps, a structure of faceted islands (0D objects), a cross-hatch morphology (1D objects), an array of finger-like units (1D objects), or an array of giant bunched steps (1D objects). The surface can be tailored to a particular structure by controlling the vicinality of the substrate and the growth rate and nominal thickness of the film. In the case of CCO films, grown on (001)-oriented MgAl2O4 or MgO substrates, high aspect ratio {111}-faceted pyramids and hut clusters (0D objects), highly oriented and having a similar size, appear above a critical thickness. The size and spatial density can be tuned by varying deposition temperature, nominal thickness, and substrate. This dependence allows the fabrication of surfaces being fully faceted (2D objects), or having arrays of dislocated pyramids of up to micrometric size, or small coherently lattice strained pyramids having a nanometric size. We discuss the driving forces that originate the peculiar SRO and CCO nanostructures. The findings illustrate that the growth of complex oxides can promote a variety of novel self-organized morphologies, and suggest original strategies to fabricate templates or hybrid structures of oxides combining varied functionalities.

  6. Intermixing and thermal oxidation of ZrO2 thin films grown on a-Si, SiN, and SiO2 by metallic and oxidic mode magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Coloma Ribera, R.; van de Kruijs, R. W. E.; Sturm, J. M.; Yakshin, A. E.; Bijkerk, F.

    2017-03-01

    The initial growth of DC sputtered ZrO2 on top of a-Si, SiN, and SiO2 layers has been studied by in vacuo high-sensitivity low energy ion scattering for two gas deposition conditions with different oxygen contents (high-O and low-O conditions). This unique surface sensitive technique allowed the determination of surface composition and thicknesses required to close the ZrO2 layer on all three substrates for both conditions. The ZrO2 layer closes similarly on all substrates due to more favorable enthalpies of formation for ZrO2 and ZrSiO4, resulting in passivation of the Si from the substrate. However, this layer closes at about half of the thickness (˜1.7 nm) for low-O conditions due to less oxidative conditions and less energetic particles arriving at the sample, which leads to less intermixing via silicate formation. In contrast, for high-O conditions, there is more ZrSiO4 and/or SiOx formation, giving more intermixing (˜3.4 nm). In vacuo X-ray photoelectron spectroscopy (XPS) measurements revealed similar stoichiometric ZrO2 layers deposited by both conditions and a higher interaction of the ZrO2 layer with the underlying a-Si for high-O conditions. In addition, oxygen diffusion through low-O ZrO2 films on a-Si has been investigated by ex situ angular-resolved XPS of samples annealed in atmospheric oxygen. For temperatures below 400 °C, no additional oxidation of the underlying a-Si was observed. This, together with the amorphous nature and smoothness of these samples, makes ZrO2 a good candidate as an oxidation protective layer on top of a-Si.

  7. Interface composition of InAs nanowires with Al2O3 and HfO2 thin films

    NASA Astrophysics Data System (ADS)

    Timm, R.; Hjort, M.; Fian, A.; Borg, B. M.; Thelander, C.; Andersen, J. N.; Wernersson, L.-E.; Mikkelsen, A.

    2011-11-01

    Vertical InAs nanowires (NWs) wrapped by a thin high-κ dielectric layer may be a key to the next generation of high-speed metal-oxide-semiconductor devices. Here, we have investigated the structure and chemical composition of the interface between InAs NWs and 2 nm thick Al2O3 and HfO2 films. The native oxide on the NWs is significantly reduced upon high-κ deposition, although less effective than for corresponding planar samples, resulting in a 0.8 nm thick interface layer with an In-/As-oxide composition of about 0.7/0.3. The exact oxide reduction and composition including As-suboxides and the role of the NW geometry are discussed in detail.

  8. Influences of annealing temperature on sprayed CuFeO2 thin films

    NASA Astrophysics Data System (ADS)

    Abdelwahab, H. M.; Ratep, A.; Abo Elsoud, A. M.; Boshta, M.; Osman, M. B. S.

    2018-06-01

    Delafossite CuFeO2 thin films were successfully prepared onto quartz substrates using simple spray pyrolysis technique. Post annealing under nitrogen atmosphere for 2 h was necessary to form delafossite CuFeO2 phase. The effect of alteration in annealing temperature (TA) 800, 850 and 900 °C was study on structural, morphology and optical properties. The XRD results for thin film annealed at TA = 850 °C show single phase CuFeO2 with rhombohedral crystal system and R 3 bar m space group with preferred orientation along (0 1 2). The prepared copper iron oxide thin films have an optical transmission ranged ∼40% in the visible region. The optical direct optical band gap of the prepared thin films was ranged ∼2.9 eV.

  9. Investigation of phase transition properties of ZrO2 thin films

    NASA Astrophysics Data System (ADS)

    Kumar, Davinder; Singh, Avtar; Kaur, Manpreet; Rana, Vikrant Singh; Kaur, Raminder

    2018-05-01

    This paper presents the synthesis of transparent thin films of zirconium oxide (ZrO2) deposited on glass substrates by sol-gel dip coating technique. Synthesized films were characterized for different annealing time and withdrawal speed. Change in crystallographic properties of thin films was investigated by using X-ray diffraction. Surface morphology of transparent thin films was estimated by using scanning electron microscope.

  10. Amorphous nickel incorporated tin oxide thin film transistors

    NASA Astrophysics Data System (ADS)

    Yang, Jianwen; Ren, Jinhua; Lin, Dong; Han, Yanbing; Qu, Mingyue; Pi, Shubin; Fu, Ruofan; Zhang, Qun

    2017-09-01

    Nickel as a dopant has been proposed to suppress excess carrier concentration in n-type tin oxide based thin film transistors (TFTs). The influences of Ni content on nickel doped tin oxide (TNO) thin films and their corresponding TFTs were investigated with experimental results showing that the TNO thin films are amorphous. Through the comparison of the transfer characteristic curves of the TNO TFTs with different Ni contents, it was observed that Ni doping is useful to improve the performance of SnO2-based TFTs by suppressing the off-state current and shifting the threshold voltage to 0 V. The amorphous TNO TFT with 3.3 at.% Ni content shows optimum performance, with field effect mobility of 8.4 cm2 V-1 s-1, saturation mobility of 6.8 cm2 V-1 s-1, subthreshold swing value of 0.8 V/decade, and an on-off current ratio of 2.1  ×  107. Nevertheless, the bias stress stability of SnO2-based TFTs deteriorate.

  11. The effect of solution pH on the electrochemical performance of nanocrystalline metal ferrites MFe2O4 (M=Cu, Zn, and Ni) thin films

    NASA Astrophysics Data System (ADS)

    Elsayed, E. M.; Rashad, M. M.; Khalil, H. F. Y.; Ibrahim, I. A.; Hussein, M. R.; El-Sabbah, M. M. B.

    2016-04-01

    Nanocrystalline metal ferrite MFe2O4 (M=Cu, Zn, and Ni) thin films have been synthesized via electrodeposition-anodization process. Electrodeposited (M)Fe2 alloys were obtained from aqueous sulfate bath. The formed alloys were electrochemically oxidized (anodized) in aqueous (1 M KOH) solution, at room temperature, to the corresponding hydroxides. The parameters controlling the current efficiency of the electrodeposition of (M)Fe2 alloys such as the bath composition and the current density were studied and optimized. The anodized (M)Fe2 alloy films were annealed in air at 400 °C for 2 h. The results revealed the formation of three ferrite thin films were formed. The crystallite sizes of the produced films were in the range between 45 and 60 nm. The microstructure of the formed film was ferrite type dependent. The corrosion behavior of ferrite thin films in different pH solutions was investigated using open circuit potential (OCP) and potentiodynamic polarization measurements. The open circuit potential indicates that the initial potential E im of ZnFe2O4 thin films remained constant for a short time, then sharply increased in the less negative direction in acidic and alkaline medium compared with Ni and Cu ferrite films. The values of the corrosion current density I corr were higher for the ZnFe2O4 films at pH values of 1 and 12 compared with that of NiFe2O4 and CuFe2O4 which were higher only at pH value 1. The corrosion rate was very low for the three ferrite films when immersion in the neutral medium. The surface morphology recommended that Ni and Cu ferrite films were safely used in neutral and alkaline medium, whereas Zn ferrite film was only used in neutral atmospheres.

  12. Ferroelectricity emerging in strained (111)-textured ZrO{sub 2} thin films

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Fan, Zhen, E-mail: a0082709@u.nus.edu, E-mail: msecj@nus.edu.sg; Deng, Jinyu; Liu, Ziyan

    2016-01-04

    (Anti-)ferroelectricity in complementary metal-oxide-semiconductor (CMOS)-compatible binary oxides have attracted considerable research interest recently. Here, we show that by using substrate-induced strain, the orthorhombic phase and the desired ferroelectricity could be achieved in ZrO{sub 2} thin films. Our theoretical analyses suggest that the strain imposed on the ZrO{sub 2} (111) film by the TiN/MgO (001) substrate would energetically favor the tetragonal (t) and orthorhombic (o) phases over the monoclinic (m) phase of ZrO{sub 2}, and the compressive strain along certain 〈11-2〉 directions may further stabilize the o-phase. Experimentally ZrO{sub 2} thin films are sputtered onto the MgO (001) substrates buffered bymore » epitaxial TiN layers. ZrO{sub 2} thin films exhibit t- and o-phases, which are highly (111)-textured and strained, as evidenced by X-ray diffraction and transmission electron microscopy. Both polarization-electric field (P-E) loops and corresponding current responses to voltage stimulations measured with appropriate applied fields reveal the ferroelectric sub-loop behavior of the ZrO{sub 2} films at certain thicknesses, confirming that the ferroelectric o-phase has been developed in the strained (111)-textured ZrO{sub 2} films. However, further increasing the applied field leads to the disappearance of ferroelectric hysteresis, the possible reasons of which are discussed.« less

  13. Magnetically retrievable nickel hydroxide functionalised AFe2O4 (A = Mn, Ni) spinel nanocatalyst for alcohol oxidation

    NASA Astrophysics Data System (ADS)

    Bhat, Pooja B.; Bhat, Badekai Ramachandra

    2016-03-01

    Ultrasmall nickel hydroxide functionalised AFe2O4 (A = Mn, Ni) nanocatalyst was synthesized by traditional co-precipitation method and was examined for oxidation of aromatic alcohols to carbonyls using hydrogen peroxide as terminal oxidant. A very high surface area of 104.55 m2 g-1 was achieved for ferromagnetic MnFe2O4 and 100.50 m2 g-1 for superparamagnetic NiFe2O4, respectively. Efficient oxidation was observed due to the synergized effect of nickel hydroxide (bronsted base) on Lewis center (Fe) of the nanocatalyst. Catalyst recycling experiments revealed that the ultrasmall nanocatalyst can be easily recovered by external magnet and applied for nearly complete oxidation of alcohols for at least five successive cycles. Furthermore, the nickel hydroxide functionalised ultrasmall nanocatalyst exhibited higher efficiency for benzyl alcohol oxidation compared to Ni(OH)2, bare MnFe2O4 and NiFe2O4. Higher conversion rate was observed for nickel hydroxide functionalised NiFe2O4 compared to MnFe2O4. Ultrasmall magnetic nickel hydroxide functionalised nanocatalyst showed environmental friendly, greener route for the oxidation of alcohols without significant loss in activity and selectivity within successive runs.

  14. Nanostructural origin of semiconductivity and large magnetoresistance in epitaxial NiCo2O4/Al2O3 thin films

    NASA Astrophysics Data System (ADS)

    Zhen, Congmian; Zhang, XiaoZhe; Wei, Wengang; Guo, Wenzhe; Pant, Ankit; Xu, Xiaoshan; Shen, Jian; Ma, Li; Hou, Denglu

    2018-04-01

    Despite low resistivity (~1 mΩ cm), metallic electrical transport has not been commonly observed in inverse spinel NiCo2O4, except in certain epitaxial thin films. Previous studies have stressed the effect of valence mixing and the degree of spinel inversion on the electrical conduction of NiCo2O4 films. In this work, we studied the effect of nanostructural disorder by comparing the NiCo2O4 epitaxial films grown on MgAl2O4 (1 1 1) and on Al2O3 (0 0 1) substrates. Although the optimal growth conditions are similar for the NiCo2O4 (1 1 1)/MgAl2O4 (1 1 1) and the NiCo2O4 (1 1 1)/Al2O3 (0 0 1) films, they show metallic and semiconducting electrical transport, respectively. Post-growth annealing decreases the resistivity of NiCo2O4 (1 1 1)/Al2O3 (0 0 1) films, but the annealed films are still semiconducting. While the semiconductivity and the large magnetoresistance in NiCo2O4 (1 1 1)/Al2O3 (0 0 1) films cannot be accounted for in terms of non-optimal valence mixing and spinel inversion, the presence of anti-phase boundaries between nano-sized crystallites, generated by the structural mismatch between NiCo2O4 and Al2O3, may explain all the experimental observations in this work. These results reveal nanostructural disorder as being another key factor for controlling the electrical transport of NiCo2O4, with potentially large magnetoresistance for spintronics applications.

  15. Degradation of 2,4-dichlorophenol with a novel TiO2/Ti-Fe-graphite felt photoelectrocatalytic oxidation process.

    PubMed

    Zhao, Bao-xiu; Li, Xiang-zhong; Wang, Peng

    2007-01-01

    Degradation of 2,4-dichlorophenol (2,4-DCP) was studied in a novel three-electrode photoelectrocatalytic (PEC) integrative oxidation process, and the factors influencing the degradation rate, such as applied current, flow speed of O2, pH, adscititious voltage and initial 2,4-DCP concentration were investigated and optimized. H2O2 was produced nearby cathode and Fe2+ continuously generated from Fe anode in solution when current and O2 were applied, so, main reactions, H2O2-assisted TiO2 PEC oxidation and E-Fenton reaction, occurred during degradation of 2,4-DCP in this integrative system. The degradation ratio of 2,4-DCP was 93% in this integrative oxidation process, while it was only 31% in E-Fenton process and 46% in H2O2-assisted TiO2 PEC process. So, it revealed that the degradation of 2,4-DCP was improved greatly by photoelectrical cooperation effect. By the investigation of pH, it showed that this integrative process could work well in a wide pH range from pH 3 to pH 9.

  16. Scavenging of oxygen from SrTiO3 by metals and its implications for oxide thin film deposition

    NASA Astrophysics Data System (ADS)

    Posadas, Agham; Kormondy, Kristy; Guo, Wei; Ponath, Patrick; Kremer, Jacqueline; Hadamek, Tobias; Demkov, Alexander

    SrTiO3 is a widely used substrate for the growth of other functional oxide thin films. However, SrTiO3 loses oxygen very easily during oxide thin film deposition even under relatively high oxygen pressures. In some cases, there will be an interfacial layer of oxygen-deficient SrTiO3 formed at the interface with the deposited oxide film, depending on the metals present in the film. By depositing a variety of metals layer by layer and measuring the evolution of the core level spectra of both the deposited metal and SrTiO3 using x-ray photoelectron spectroscopy, we show that there are three distinct types of behavior that occur for thin metal films on SrTiO3. We discuss the implications of these types of behavior for the growth of complex oxide thin films on SrTiO3, and which oxide thin films are expected to produce an interfacial oxygen-deficient layer depending on their elemental constituents.

  17. The crystal structure of ianthinite, [U 24+(UO 2) 4O 6(OH) 4(H 2O) 4](H 2O) 5: a possible phase for Pu 4+ incorporation during the oxidation of spent nuclear fuel

    NASA Astrophysics Data System (ADS)

    Burns, Peter C.; Finch, Robert J.; Hawthorne, Frank C.; Miller, Mark L.; Ewing, Rodney C.

    1997-10-01

    Ianthinite, [U 24+(UO 2) 4O 6(OH) 4(H 2O) 4](H 2O) 5, is the only known uranyl oxide hydrate mineral that contains U 4+, and it has been proposed that ianthinite may be an important Pu 4+-bearing phase during the oxidative dissolution of spent nuclear fuel. The crystal structure of ianthinite, orthorhombic, a = 0.7178(2), b = 1.1473(2), c = 3.039(1) nm, V = 2.5027 nm 3Z = 4, space group P2 1cn, has been solved by direct methods and refined by least-squares methods to an R index of 9.7% and a wR index of 12.6% using 888 unique observed [| F| ≥ 5 σ | F|] reflections. The structure contains both U 4+. The U 6+ cations are present as roughly linear (U 6+O 2) 2+ uranyl ion (Ur) that are in turn coordinated by five O 2- and OH - located at the equatorial positions of pentagonal bipyramids. The U 4+ cations are coordinated by O 2-, OH - and H 2O in a distorted octahedral arrangement. The Ur φ5and U 4+| 6 (φ: O 2-, OH -, H 2O) polyhedra l sharing edges to for two symmetrically distinct sheets at z ≈ 0.0 and z ≈ 0.25 that are parallel to (001). The sheets have the β-U 3O 8 sheet anion-topology. There are five symmetrically distinct H 2O groips located at z ≈ 0.125 between the sheets of U φn polyhedra, and the sheets of U φn polyhedra are linked together only by hydrogen bonding to the intersheet H 2O groups. The crystal-chemical requirements of U 4+ and Pu 4+ are very similar, suggesting that extensive Pu 4+ ↔ U 4+ substitution may occur within the sheets of U φn polyhedra in trh structure of ianthinine.

  18. Three dimensional-stacked complementary thin-film transistors using n-type Al:ZnO and p-type NiO thin-film transistors.

    PubMed

    Lee, Ching-Ting; Chen, Chia-Chi; Lee, Hsin-Ying

    2018-03-05

    The three dimensional inverters were fabricated using novel complementary structure of stacked bottom n-type aluminum-doped zinc oxide (Al:ZnO) thin-film transistor and top p-type nickel oxide (NiO) thin-film transistor. When the inverter operated at the direct voltage (V DD ) of 10 V and the input voltage from 0 V to 10 V, the obtained high performances included the output swing of 9.9 V, the high noise margin of 2.7 V, and the low noise margin of 2.2 V. Furthermore, the high performances of unskenwed inverter were demonstrated by using the novel complementary structure of the stacked n-type Al:ZnO thin-film transistor and p-type nickel oxide (NiO) thin-film transistor.

  19. A comparative study of heterostructured CuO/CuWO4 nanowires and thin films

    NASA Astrophysics Data System (ADS)

    Polyakov, Boris; Kuzmin, Alexei; Vlassov, Sergei; Butanovs, Edgars; Zideluns, Janis; Butikova, Jelena; Kalendarev, Robert; Zubkins, Martins

    2017-12-01

    A comparative study of heterostructured CuO/CuWO4 core/shell nanowires and double-layer thin films was performed through X-ray diffraction, confocal micro-Raman spectroscopy and electron (SEM and TEM) microscopies. The heterostructures were produced using a two-step process, starting from a deposition of amorphous WO3 layer on top of CuO nanowires and thin films by reactive DC magnetron sputtering and followed by annealing at 650 °C in air. The second step induced a solid-state reaction between CuO and WO3 oxides through a thermal diffusion process, revealed by SEM-EDX analysis. Morphology evolution of core/shell nanowires and double-layer thin films upon heating was studied by electron (SEM and TEM) microscopies. A formation of CuWO4 phase was confirmed by X-ray diffraction and confocal micro-Raman spectroscopy.

  20. Growth and giant coercive field of spinel-structured Co3- x Mn x O4 thin films

    NASA Astrophysics Data System (ADS)

    Kwak, Yongsu; Song, Jonghyun; Koo, Taeyeong

    2016-08-01

    We grew epitaxial thin films of CoMn2O4 and Co2MnO4 on Nb-doped SrTiO3(011) and SrTiO3(001) single crystal substrates using pulsed laser deposition. The magnetic Curie temperature ( T c ) of the Co2MnO4 thin films was ~176 K, which is higher than that of the bulk whereas CoMn2O4 thin films exhibited a value of T c (~151 K) lower than that of the bulk. For the Co2MnO4 thin films, the M - H loop showed a coercive field of ~0.7 T at 10 K, similar to the value for the bulk. However, the M -H loop of the CoMn2O4(0 ll) thin film grown on a Nb-doped SrTiO3(011) substrate exhibited a coercive field of ~4.5 T at 30 K, which is significantly higher than those of the Co2MnO4 thin film and bulk. This giant coercive field, only observed for the CoMn2O4(0 ll) thin film, can be attributed to the shape anisotropy and strong spin-orbit coupling.

  1. Structural and morphological study of ZrO2 thin films

    NASA Astrophysics Data System (ADS)

    Kumar, Davinder; Singh, Avtar; Kaur, Manpreet; Rana, Vikrant Singh; Kaur, Raminder

    2018-05-01

    In this paper we discuss the fabrication of transparent thin films of Zirconium Oxide (ZrO2) deposited on glass substrates by sol-gel dip coating technique. Further these fabricated films were characterized for different annealing temperatures and withdrawal speed. X-ray diffraction is used to study the structural properties of deposited thin films and it reveals the change in crystallographic properties with the change in annealing temperature. Thickness of thin films is estimated by using scanning electron microscope.

  2. Optimization of a Solution-Processed SiO2 Gate Insulator by Plasma Treatment for Zinc Oxide Thin Film Transistors.

    PubMed

    Jeong, Yesul; Pearson, Christopher; Kim, Hyun-Gwan; Park, Man-Young; Kim, Hongdoo; Do, Lee-Mi; Petty, Michael C

    2016-01-27

    We report on the optimization of the plasma treatment conditions for a solution-processed silicon dioxide gate insulator for application in zinc oxide thin film transistors (TFTs). The SiO2 layer was formed by spin coating a perhydropolysilazane (PHPS) precursor. This thin film was subsequently thermally annealed, followed by exposure to an oxygen plasma, to form an insulating (leakage current density of ∼10(-7) A/cm(2)) SiO2 layer. Optimized ZnO TFTs (40 W plasma treatment of the gate insulator for 10 s) possessed a carrier mobility of 3.2 cm(2)/(V s), an on/off ratio of ∼10(7), a threshold voltage of -1.3 V, and a subthreshold swing of 0.2 V/decade. In addition, long-term exposure (150 min) of the pre-annealed PHPS to the oxygen plasma enabled the maximum processing temperature to be reduced from 180 to 150 °C. The resulting ZnO TFT exhibited a carrier mobility of 1.3 cm(2)/(V s) and on/off ratio of ∼10(7).

  3. Growth and characterization of single phase Cu{sub 2}O by thermal oxidation of thin copper films

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Choudhary, Sumita; Sarma, J. V. N.; Gangopadhyay, Subhashis, E-mail: subhagan@yahoo.com

    2016-04-13

    We report a simple and efficient technique to form high quality single phase cuprous oxide films on glass substrate using thermal evaporation of thin copper films followed by controlled thermal oxidation in air ambient. Crystallographic analysis and oxide phase determination, as well as grain size distribution have been studied using X-ray diffraction (XRD) method, while scanning electron microscopy (SEM) has been utilized to investigate the surface morphology of the as grown oxide films. The formation of various copper oxide phases is found to be highly sensitive to the oxidation temperature and a crystalline, single phase cuprous oxide film can bemore » achieved for oxidation temperatures between 250°C to 320°C. Cu{sub 2}O film surface appeared in a faceted morphology in SEM imaging and a direct band gap of about 2.1 eV has been observed in UV-visible spectroscopy. X-ray photoelectron spectroscopy (XPS) confirmed a single oxide phase formation. Finally, a growth mechanism of the oxide film has also been discussed.« less

  4. GeO2 Thin Film Deposition on Graphene Oxide by the Hydrogen Peroxide Route: Evaluation for Lithium-Ion Battery Anode.

    PubMed

    Medvedev, Alexander G; Mikhaylov, Alexey A; Grishanov, Dmitry A; Yu, Denis Y W; Gun, Jenny; Sladkevich, Sergey; Lev, Ovadia; Prikhodchenko, Petr V

    2017-03-15

    A peroxogermanate thin film was deposited in high yield at room temperature on graphene oxide (GO) from peroxogermanate sols. The deposition of the peroxo-precursor onto GO and the transformations to amorphous GeO 2 , crystalline tetragonal GeO 2 , and then to cubic elemental germanium were followed by electron microscopy, XRD, and XPS. All of these transformations are influenced by the GO support. The initial deposition is explained in view of the sol composition and the presence of GO, and the different thermal transformations are explained by reactions with the graphene support acting as a reducing agent. As a test case, the evaluation of the different materials as lithium ion battery anodes was carried out revealing that the best performance is obtained by amorphous germanium oxide@GO with >1000 mAh g -1 at 250 mA g -1 (between 0 and 2.5 V vs Li/Li + cathode), despite the fact that the material contained only 51 wt % germanium. This is the first demonstration of the peroxide route to produce peroxogermanate thin films and thereby supported germanium and germanium oxide coatings. The advantages of the process over alternative methodologies are discussed.

  5. Nanostructured ZnO-TiO2 thin film oxide as anode material in electrooxidation of organic pollutants. Application to the removal of dye Amido black 10B from water.

    PubMed

    El-Kacemi, Sana; Zazou, Hicham; Oturan, Nihal; Dietze, Matthias; Hamdani, Mohamed; Es-Souni, Mohammed; Oturan, Mehmet A

    2017-01-01

    Electrochemical oxidative degradation of diazo dye Amido black 10B (AB10B) as model pollutant in water has been studied using nanostructured ZnO-TiO 2 thin films deposited on graphite felt (GrF) substrate as anode. The influence of various operating parameters, namely the current intensity, the nature and concentration of catalyst, the nature of electrode materials (anode/cathode), and the adsorption of dye and ambient light were investigated. It was found that the oxidative degradation of AB10B followed pseudo first-order kinetics. The optimal operating conditions for the degradation of 0.12 mM (74 mg L -1 ) dye concentration and mineralization of its aqueous solution were determined as GrF-ZnO-TiO 2 thin film anode, 100 mA current intensity, and 0.1 mM Fe 2+ (catalyst) concentration. Under these operating conditions, discoloration of AB10B solution was reached at 60 min while 6 h treatment needed for a mineralization degree of 91 %. Therefore, this study confirmed that the electrochemical process is effective for the degradation of AB10B in water using nanostructured ZnO-TiO 2 thin film anodes.

  6. Spray deposited MnFe2O4 thin films for detection of ethanol and acetone vapors

    NASA Astrophysics Data System (ADS)

    Nagarajan, V.; Thayumanavan, A.

    2018-01-01

    Spinel MnFe2O4 films were synthesized with the help of spray pyrolysis technique. The morphology study shows fine crushed sand grain morphology of the film. The structural investigation verifies the polycrystalline nature of prepared MnFe2O4 films, which possess the spinel structure. Crystalline size is found to be around 23.5 nm-37.4 nm morphology analyses. Energy dispersive spectroscopy validates the presence of oxygen, iron and manganese in MnFe2O4 film. The prepared MnFe2O4 film is extremely sensitive towards ethanol molecules at 300 K. The electrical resistance of MnFe2O4 thin film decreases quickly when ethanol and acetone vapor molecules are adsorbed on base material. The synthesized MnFe2O4 film is also highly sensitive towards acetone molecules at ambient temperature. The selectivity, sensing response, stability and recovery time of MnFe2O4 film towards acetone and ethanol detection are analyzed in the present work.

  7. Structural phase diagram for ultra-thin epitaxial Fe 3O 4 / MgO(0 01) films: thickness and oxygen pressure dependence

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Alraddadi, S.; Hines, W.; Yilmaz, T.

    2016-02-19

    A systematic investigation of the thickness and oxygen pressure dependence for the structural properties of ultra-thin epitaxial magnetite (Fe 3O 4) films has been carried out; for such films, the structural properties generally differ from those for the bulk when the thickness ≤10 nm. Iron oxide ultra-thin films with thicknesses varying from 3 nm to 20 nm were grown on MgO (001) substrates using molecular beam epitaxy under different oxygen pressures ranging from 1 × 10 -7 torr to 1 × 10 -5 torr. The crystallographic and electronic structures of the films were characterized using low energy electron diffraction (LEED)more » and x-ray photoemission spectroscopy (XPS), respectively. Moreover, the quality of the epitaxial Fe 3O 4 ultra-thin films was judged by magnetic measurements of the Verwey transition, along with complementary XPS spectra. We observed that under the same growth conditions the stoichiometry of ultra-thin films under 10 nm transforms from the Fe 3O 4 phase to the FeO phase. In this work, a phase diagram based on thickness and oxygen pressure has been constructed to explain the structural phase transformation. It was found that high-quality magnetite films with thicknesses ≤20 nm formed within a narrow range of oxygen pressure. An optimal and controlled growth process is a crucial requirement for the accurate study of the magnetic and electronic properties for ultra-thin Fe 3O 4 films. Furthermore, these results are significant because they may indicate a general trend in the growth of other oxide films, which has not been previously observed or considered.« less

  8. Electrical and structural properties of TiO2thin film with oxygen vacancies prepared by RF magnetron sputtering using oxygen radical

    NASA Astrophysics Data System (ADS)

    Kawamura, Kinya; Suzuki, Naoya; Tsuchiya, Takashi; Shimazu, Yuichi; Minohara, Makoto; Kobayashi, Masaki; Horiba, Koji; Kumigashira, Hiroshi; Higuchi, Tohru

    2016-06-01

    Anatase TiO2thin film was prepared by RF magnetron sputtering using oxygen radical and Ti-metal target. Degrees of the TiO2-δ crystal orientation in the thin film depends of the oxygen gas pressure (P\\text{O2}) in the radical gun. The (004)- and (112)-oriented TiO2thin films crystallized without postannealing have the mixed valence Ti4+/Ti3+ state. The electrical conductivities, which corresponds to n-type oxide semiconductor, is higher in the case of (004)-oriented TiO2thin film containing with high concentration of oxygen vacancy. The donor band of TiO2thin film is observed at ˜1.0 eV from the Fermi level (E F). The density-of-state at E F is higher in (004)-oriented TiO2thin film. The above results indicate that the oxygen vacancies can control by changing the P\\text{O2} of the oxygen radical.

  9. Mechanistic insight into peroxydisulfate reactivity: Oxidation of the cis,cis-[Ru(bpy) 2(OH 2)] 2O 4+ "Blue Dimmer"

    DOE PAGES

    Hurst, James K.; Roemeling, Margo D.; Lymar, Sergei V.

    2015-04-10

    One-electron oxidation of the μ-oxo dimer (cis,cis-[Ru III(bpy) 2(OH 2)] 2O 4+, {3,3}) to {3,4} by S 2O 8 2- can be described by three concurrent reaction pathways corresponding to the three protic forms of {3,3}. Free energy correlations of the rate constants, transient species dynamics determined by pulse radiolysis, and medium and temperature dependencies of the alkaline pathway all suggest that the rate determining step in these reactions is a strongly non-adiabatic dissociative electron transfer within a precursor ion pair leading to the {3,4}|SO 4 2-|SO 4 •- ion triple. As deduced from the SO 4 •- scavenging experimentsmore » with 2-propanol, the SO 4 •- radical then either oxidizes {3,4} to {4,4} within the ion triple, effecting a net two-electron oxidation of {3,3}, or escapes in solution with ~25 % probability to react with additional {3,3} and {3,4}, that is, effecting sequential one-electron oxidations. The reaction model presented also invokes rapid {3,3} + {4,4} → 2 {3,4} comproportionation, for which k com ~5×10 7 M -1 s -1 was independently measured. The model provides an explanation for the observation that despite favorable energetics, no oxidation beyond the {3,4} state was detected. As a result, the indiscriminate nature of oxidation by SO 4 •- indicates that its fate must be quantitatively determined when using S 2O 8 2- as an oxidant« less

  10. Microstructure of epitaxial ferroelectric/metal oxide electrode thin film heterostructures on LaAlO{sub 3} and silicon

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ghonge, S.G.; Goo, E.; Ramesh, R.

    1994-12-31

    TEM and X-ray diffraction studies of PZT, PLZT, lead titanate and bismuth titanate ferroelectric thin films and YBa{sub 2}Cu{sub 3}O{sub 7{minus}x}(YBCO), Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8}(BSCCO) and La{sub 0.5}Sr{sub 0.5}CoO{sub 3}(LSCO) electrically conductive oxide thin films, that are sequentially deposited by pulsed laser ablation, show that these films may be deposited epitaxially onto LaAlO{sub 3}(LAO) or Si substrates. The conductive oxides are promising candidates for use is electrodes in place of metal electrodes in integrated ferroelectric device applications. The oxide electrodes are more chemically compatible with the ferroelectric films. High resolution electron microscopy his been used to investigate the interfacemore » between the ferroelectric and metal oxide thin films and no reaction was detected. Epitaxial growth is possible due to the similar crystal structures and the small lattice mismatch. The lattice mismatch that is present causes the domains in the ferroelectric films to be preferentially oriented and in the case of lead titanate, the film is single domain. These films may also have potential applications in integrated optical devices.« less

  11. Electronic Devices Based on Oxide Thin Films Fabricated by Fiber-to-Film Process.

    PubMed

    Meng, You; Liu, Ao; Guo, Zidong; Liu, Guoxia; Shin, Byoungchul; Noh, Yong-Young; Fortunato, Elvira; Martins, Rodrigo; Shan, Fukai

    2018-05-30

    Technical development for thin-film fabrication is essential for emerging metal-oxide (MO) electronics. Although impressive progress has been achieved in fabricating MO thin films, the challenges still remain. Here, we report a versatile and general thermal-induced nanomelting technique for fabricating MO thin films from the fiber networks, briefly called fiber-to-film (FTF) process. The high quality of the FTF-processed MO thin films was confirmed by various investigations. The FTF process is generally applicable to numerous technologically relevant MO thin films, including semiconducting thin films (e.g., In 2 O 3 , InZnO, and InZrZnO), conducting thin films (e.g., InSnO), and insulating thin films (e.g., AlO x ). By optimizing the fabrication process, In 2 O 3 /AlO x thin-film transistors (TFTs) were successfully integrated by fully FTF processes. High-performance TFT was achieved with an average mobility of ∼25 cm 2 /(Vs), an on/off current ratio of ∼10 7 , a threshold voltage of ∼1 V, and a device yield of 100%. As a proof of concept, one-transistor-driven pixel circuit was constructed, which exhibited high controllability over the light-emitting diodes. Logic gates based on fully FTF-processed In 2 O 3 /AlO x TFTs were further realized, which exhibited good dynamic logic responses and voltage amplification by a factor of ∼4. The FTF technique presented here offers great potential in large-area and low-cost manufacturing for flexible oxide electronics.

  12. The effect of Mg dopants on magnetic and structural properties of iron oxide and zinc ferrite thin films

    NASA Astrophysics Data System (ADS)

    Saritaş, Sevda; Ceviz Sakar, Betul; Kundakci, Mutlu; Yildirim, Muhammet

    2018-06-01

    Iron oxide thin films have been obtained significant interest as a material that put forwards applications in photovoltaics, gas sensors, biosensors, optoelectronic and especially in spintronics. Iron oxide is one of the considerable interest due to its chemical and thermal stability. Metallic ion dopant influenced superexchange interactions and thus changed the structural, electrical and magnetic properties of the thin film. Mg dopped zinc ferrite (Mg:ZnxFe3-xO4) crystal was used to avoid the damage of Fe3O4 (magnetite) crystal instead of Zn2+ in this study. Because the radius of the Mg2+ ion in the A-site (tetrahedral) is almost equal to that of the replaced Fe3+ ion. Inverse-spinel structure in which oxygen ions (O2-) are arranged to form a face-centered cubic (FCC) lattice where there are two kinds of sublattices, namely, A-site and B-site (octahedral) interstitial sites and in which the super exchange interactions occur. In this study, to increase the saturation of magnetization (Ms) value for iron oxide, inverse-spinal ferrite materials have been prepared, in which the iron oxide was doped by multifarious divalent metallic elements including Zn and Mg. Triple and quaternary; iron oxide and zinc ferrite thin films with Mg metal dopants were grown by using Spray Pyrolysis (SP) technique. The structural, electrical and magnetic properties of Mg dopped iron oxide (Fe2O3) and zinc ferrite (ZnxFe3-xO4) thin films have been investigated. Vibrating Sample Magnetometer (VSM) technique was used to study for the magnetic properties. As a result, we can say that Mg dopped iron oxide thin film has huge diamagnetic and of Mg dopped zinc ferrite thin film has paramagnetic property at bigger magnetic field.

  13. Structural and magnetic properties of nanocrystalline NiFe2O4 thin film prepared by spray pyrolysis technique

    NASA Astrophysics Data System (ADS)

    Chavan, Apparao R.; Chilwar, R. R.; Shisode, M. V.; Hivrekar, Mahesh M.; Mande, V. K.; Jadhav, K. M.

    2018-05-01

    The nanocrystalline NiFe2O4 thin film has been prepared using a spray pyrolysis technique on glass substrate. The prepared thin film was characterized by using X-ray diffraction (XRD), Fourier transform Infrared spectroscopy (FTIR), and Field Emission-Scanning Electron Microscopy (FE-SEM) characterization techniques for the structural and microstructural analysis. The magnetic property was measured using vibrating sample magnetometer (VSM) at room temperature. X-ray diffraction studies show the formation of single phase spinel structure of the thin film. The octahedral and tetrahedral vibration in the sample was studied by Fourier transform infrared (FT-IR) spectra. Magnetic hysteresis loop was recorded for thin film at room temperature. At 15 kOe, saturation magnetization (Ms) was found to increase while coercivity (Hc) decreases with thickness of the NiFe2O4 thin film.

  14. Soot oxidation and NO{sub x} reduction over BaAl{sub 2}O{sub 4} catalyst

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Lin, He; Li, Yingjie; Shangguan, Wenfeng

    2009-11-15

    This study addresses soot oxidation and NO{sub x} reduction over a BaAl{sub 2}O{sub 4} catalyst. By XRD analysis, the catalyst was shown to be of spinel structure. Temperature Programmed Oxidation (TPO) and Constant Temperature Oxidation (CTO) at 673 K show that the presence of O{sub 2} decreases the ignition temperature of soot, and it enhances the conversion of NO{sub x} to N{sub 2} and N{sub 2}O. The kinetic features of soot oxidation in the TPO test are similar to that in the TG-DTA analysis. Analysis by Diffuse Reflectance Fourier Infrared Transform Spectroscopy (DRIFTS) indicates that the nitrates formed from NO{submore » x} adsorption and the C(O) intermediates from soot oxidation are the key precursors of the redox process between soot and NO{sub x} over surfaces of the BaAl{sub 2}O{sub 4} catalyst. Moreover, DRIFTS tests suggest that nitrates act as the principal oxidants for C(O) oxidation, through which nitrates are reduced to N{sub 2} and N{sub 2}O. The O{sub 2} in the gas mixture presents a positive effect on the conversion of NO{sub x} to N{sub 2} and N{sub 2}O by promoting the oxidation of nitrites into nitrates species. (author)« less

  15. DFT studies of elemental mercury oxidation mechanism by gaseous advanced oxidation method: Co-interaction with H2O2 on Fe3O4 (111) surface

    NASA Astrophysics Data System (ADS)

    Zhou, Changsong; Song, Zijian; Zhang, Zhiyue; Yang, Hongmin; Wang, Ben; Yu, Jie; Sun, Lushi

    2017-12-01

    Density functional theory calculations have been carried out for H2O2 and Hg0 co-interaction on Fe3O4 (111) surface. On the Fetet1-terminated Fe3O4 (111) surface, the most favored configurations are H2O2 decomposition and produce two OH groups, which have strong interaction with Hg atom to form an OHsbnd Hgsbnd OH intermediate. The adsorbed OHsbnd Hgsbnd OH is stable and hardly detaches from the catalyst surface due to the highly endothermic process. A large amount of electron transfer has been found from Hg to the produced OH groups and has little irreversible effect on the Fe3O4 (111) surface. On the Feoct2-terminated Fe3O4 (111) surface, the Feoct2 site is more active than Fetet1 site. H2O2 decomposition and Hg0 oxidation processes are more likely to occur due to that the Feoct2 site both contains Fe2+ and Fe3+ cations. The calculations reveal that Hg0 oxidation by the OH radical produced from H2O2 is energetically favored. Additionally, Hg0 and H2O2 co-interaction mechanism on the Fe3O4 (111) interface has been investigated on the basis of partial local density of state calculation.

  16. Highly efficient alkane oxidation catalyzed by [Mn(V)(N)(CN)4](2-). Evidence for [Mn(VII)(N)(O)(CN)4](2-) as an active intermediate.

    PubMed

    Ma, Li; Pan, Yi; Man, Wai-Lun; Kwong, Hoi-Ki; Lam, William W Y; Chen, Gui; Lau, Kai-Chung; Lau, Tai-Chu

    2014-05-28

    The oxidation of various alkanes catalyzed by [Mn(V)(N)(CN)4](2-) using various terminal oxidants at room temperature has been investigated. Excellent yields of alcohols and ketones (>95%) are obtained using H2O2 as oxidant and CF3CH2OH as solvent. Good yields (>80%) are also obtained using (NH4)2[Ce(NO3)6] in CF3CH2OH/H2O. Kinetic isotope effects (KIEs) are determined by using an equimolar mixture of cyclohexane (c-C6H12) and cyclohexane-d12 (c-C6D12) as substrate. The KIEs are 3.1 ± 0.3 and 3.6 ± 0.2 for oxidation by H2O2 and Ce(IV), respectively. On the other hand, the rate constants for the formation of products using c-C6H12 or c-C6D12 as single substrate are the same. These results are consistent with initial rate-limiting formation of an active intermediate between [Mn(N)(CN)4](2-) and H2O2 or Ce(IV), followed by H-atom abstraction from cyclohexane by the active intermediate. When PhCH2C(CH3)2OOH (MPPH) is used as oxidant for the oxidation of c-C6H12, the major products are c-C6H11OH, c-C6H10O, and PhCH2C(CH3)2OH (MPPOH), suggesting heterolytic cleavage of MPPH to generate a Mn═O intermediate. In the reaction of H2O2 with [Mn(N)(CN)4](2-) in CF3CH2OH, a peak at m/z 628.1 was observed in the electrospray ionization mass spectrometry, which is assigned to the solvated manganese nitrido oxo species, (PPh4)[Mn(N)(O)(CN)4](-)·CF3CH2OH. On the basis of the experimental results the proposed mechanism for catalytic alkane oxidation by [Mn(V)(N)(CN)4](2-)/ROOH involves initial rate-limiting O-atom transfer from ROOH to [Mn(N)(CN)4](2-) to generate a manganese(VII) nitrido oxo active species, [Mn(VII)(N)(O)(CN)4](2-), which then oxidizes alkanes (R'H) via a H-atom abstraction/O-rebound mechanism. The proposed mechanism is also supported by density functional theory calculations.

  17. Formation mechanisms of Si3N4 and Si2N2O in silicon powder nitridation

    NASA Astrophysics Data System (ADS)

    Yao, Guisheng; Li, Yong; Jiang, Peng; Jin, Xiuming; Long, Menglong; Qin, Haixia; Kumar, R. Vasant

    2017-04-01

    Commercial silicon powders are nitrided at constant temperatures (1453 K; 1513 K; 1633 K; 1693 K). The X-ray diffraction results show that small amounts of Si3N4 and Si2N2O are formed as the nitridation products in the samples. Fibroid and short columnar Si3N4 are detected in the samples. The formation mechanisms of Si3N4 and Si2N2O are analyzed. During the initial stage of silicon powder nitridation, Si on the outside of sample captures slight amount of O2 in N2 atmosphere, forming a thin film of SiO2 on the surface which seals the residual silicon inside. And the oxygen partial pressure between the SiO2 film and free silicon is decreasing gradually, so passive oxidation transforms to active oxidation and metastable SiO(g) is produced. When the SiO(g) partial pressure is high enough, the SiO2 film will crack, and N2 is infiltrated into the central section of the sample through cracks, generating Si2N2O and short columnar Si3N4 in situ. At the same time, metastable SiO(g) reacts with N2 and form fibroid Si3N4. In the regions where the oxygen partial pressure is high, Si3N4 is oxidized into Si2N2O.

  18. Enhancement of photoelectrochemical activity of SnS thin-film photoelectrodes using TiO2, Nb2O5, and Ta2O5 metal oxide layers

    NASA Astrophysics Data System (ADS)

    Vequizo, Junie Jhon M.; Yokoyama, Masanori; Ichimura, Masaya; Yamakata, Akira

    2016-06-01

    Tin sulfide (SnS) fine photoelectrodes fabricated by three-step pulsed electrodeposition were active for H2 evolution. The incident-photon-conversion-efficiency increases from 900 nm and offers a good fit with the absorption spectrum. The activity was enhanced by 3.4, 3.0, and 1.8 times compared to bare SnS by loading Nb2O5, TiO2, and Ta2O5, respectively. Nb2O5 was most efficient because its conduction band is low enough to facilitate effective electron transfer from SnS; it also has sufficiently high potential for H2 evolution. The overall activity is determined by the competitive interfacial electron transfer between SnS/metal-oxide and metal-oxide/water. Therefore, constructing appropriate heterojunctions is necessary for further improving photoelectrochemical systems.

  19. High-pressure synthesis, crystal structure, and electromagnetic properties of CdRh2O4: an analogous oxide of the postspinel mineral MgAl2O4.

    PubMed

    Wang, Xia; Guo, Yanfeng; Shi, Youguo; Belik, Alexei A; Tsujimoto, Yoshihiro; Yi, Wei; Sun, Ying; Shirako, Yuichi; Arai, Masao; Akaogi, Masaki; Matsushita, Yoshitaka; Yamaura, Kazunari

    2012-06-18

    The postspinel mineral MgAl(2)O(4) exists only under the severe pressure conditions in the subducted oceanic lithosphere in the Earth's deep interior. Here we report that its analogous oxide CdRh(2)O(4) exhibits a structural transition to a quenchable postspinel phase under a high pressure of 6 GPa at 1400 °C, which is within the general pressure range of a conventional single-stage multianvil system. In addition, the complex magnetic contributions to the lattice and metal nonstoichiometry that often complicate investigations of other analogues of MgAl(2)O(4) are absent in CdRh(2)O(4). X-ray crystallography revealed that this postspinel phase has an orthorhombic CaFe(2)O(4) structure, thus making it a practical analogue for investigations into the geophysical role of postspinel MgAl(2)O(4). Replacement of Mg(2+) with Cd(2+) appears to be effective in lowering the pressure required for transition, as was suggested for CdGeO(3). In addition, Rh(3+) could also contribute to this reduction, as many analogous Rh oxides of aluminous and silicic minerals have been quenched from lower-pressure conditions.

  20. Electrical compensation by Ga vacancies in Ga2O3 thin films

    NASA Astrophysics Data System (ADS)

    Korhonen, E.; Tuomisto, F.; Gogova, D.; Wagner, G.; Baldini, M.; Galazka, Z.; Schewski, R.; Albrecht, M.

    2015-06-01

    The authors have applied positron annihilation spectroscopy to study the vacancy defects in undoped and Si-doped Ga2O3 thin films. The results show that Ga vacancies are formed efficiently during metal-organic vapor phase epitaxy growth of Ga2O3 thin films. Their concentrations are high enough to fully account for the electrical compensation of Si doping. This is in clear contrast to another n-type transparent semiconducting oxide In2O3, where recent results show that n-type conductivity is not limited by cation vacancies but by other intrinsic defects such as Oi.

  1. Efficient removal of arsenite through photocatalytic oxidation and adsorption by ZrO2-Fe3O4 magnetic nanoparticles

    NASA Astrophysics Data System (ADS)

    Sun, Tianyi; Zhao, Zhiwei; Liang, Zhijie; Liu, Jie; Shi, Wenxin; Cui, Fuyi

    2017-09-01

    Bifunctional ZrO2-Fe3O4 magnetic nanoparticles were synthesized and characterized, to remove As(III) through photocatalyic oxidation and adsorption. With a saturation magnetization of 27.39 emu/g, ZrO2-Fe3O4 nanoparticles with size of 10-30 nm could be easily separated from solutions with a simple magnetic process. Under UV light, As(III) could be completely oxidized to less toxic As(V) by ZrO2-Fe3O4 nanoparticles within 40 min in the photocatalytic reaction. Simultaneously, As(V) could be adsorbed onto the surface of nanoparticles with high efficiency. The adsorption of As(V) was well fitted by the pseudo-second-order model and the Freundlich isotherm model, respectively, and the maximum adsorption capacities of the nanoparticles was 133.48 mg/g at pH 7.0. As(III) could be effectively removed by ZrO2-Fe3O4 nanoparticles at initial pH range from 4 to 8. Among all the common coexisting ions investigated, except for chloride and sulfate, carbonate, silicate and phosphate decreased the As(III) removal by competing with arsenic species for adsorption sites. The synthesized magnetic ZrO2-Fe3O4 combined the photocatalytic oxidation property of ZrO2 and the high adsorption capacity of both ZrO2 and Fe3O4, which make it have significant potential applications in the As(III)-contaminated water treatment.

  2. Enhanced antibacterial performance of hybrid semiconductor nanomaterials: ZnO/SnO 2 nanocomposite thin films

    NASA Astrophysics Data System (ADS)

    Talebian, Nasrin; Nilforoushan, Mohammad Reza; Zargar, Elahe Badri

    2011-10-01

    The nano-sized coupled oxides ZnO/SnO 2 thin films in a molar ratio of 2:1 (Z2S), 1:1 (ZS) and 1:2 (ZS2) were prepared using sol-gel dip coating method and characterized with X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV-vis spectroscopy. Escherichia coli ( E. coli, ATCC 25922) was selected as a model for the Gram-negative bacteria to evaluate antibacterial property of composite samples compared with single ZnO (Z) and single SnO 2 (S) films. The antibacterial activity has been studied applying the so-called antibacterial drop test under UV illumination. The bactericidal activity was estimated by relative number of bacteria survived calculated from the number of viable cells which form colonies on the nutrient agar plates. The influence of the SnO 2-ZnO nanocomposite composition on the structural features and on the antibacterial properties of the thin films are reported and discussed. It is found that all coatings exhibited a high antibacterial activity. The coupled oxide photocatalyst Z2S has better photocatalytic activity to bacteria inactivation than ZS, ZS2, Z and S films. Furthermore, nanostructured films were active even in the absence of irradiation.

  3. X-Ray Spectroscopy of Ultra-Thin Oxide/Oxide Heteroepitaxial Films: A Case Study of Single-Nanometer VO2/TiO2

    PubMed Central

    Quackenbush, Nicholas F.; Paik, Hanjong; Woicik, Joseph C.; Arena, Dario A.; Schlom, Darrell G.; Piper, Louis F. J.

    2015-01-01

    Epitaxial ultra-thin oxide films can support large percent level strains well beyond their bulk counterparts, thereby enabling strain-engineering in oxides that can tailor various phenomena. At these reduced dimensions (typically < 10 nm), contributions from the substrate can dwarf the signal from the epilayer, making it difficult to distinguish the properties of the epilayer from the bulk. This is especially true for oxide on oxide systems. Here, we have employed a combination of hard X-ray photoelectron spectroscopy (HAXPES) and angular soft X-ray absorption spectroscopy (XAS) to study epitaxial VO2/TiO2 (100) films ranging from 7.5 to 1 nm. We observe a low-temperature (300 K) insulating phase with evidence of vanadium-vanadium (V-V) dimers and a high-temperature (400 K) metallic phase absent of V-V dimers irrespective of film thickness. Our results confirm that the metal insulator transition can exist at atomic dimensions and that biaxial strain can still be used to control the temperature of its transition when the interfaces are atomically sharp. More generally, our case study highlights the benefits of using non-destructive XAS and HAXPES to extract out information regarding the interfacial quality of the epilayers and spectroscopic signatures associated with exotic phenomena at these dimensions. PMID:28793516

  4. X-Ray Spectroscopy of Ultra-Thin Oxide/Oxide Heteroepitaxial Films: A Case Study of Single-Nanometer VO2/TiO2.

    PubMed

    Quackenbush, Nicholas F; Paik, Hanjong; Woicik, Joseph C; Arena, Dario A; Schlom, Darrell G; Piper, Louis F J

    2015-08-21

    Epitaxial ultra-thin oxide films can support large percent level strains well beyond their bulk counterparts, thereby enabling strain-engineering in oxides that can tailor various phenomena. At these reduced dimensions (typically < 10 nm), contributions from the substrate can dwarf the signal from the epilayer, making it difficult to distinguish the properties of the epilayer from the bulk. This is especially true for oxide on oxide systems. Here, we have employed a combination of hard X-ray photoelectron spectroscopy (HAXPES) and angular soft X-ray absorption spectroscopy (XAS) to study epitaxial VO2/TiO2 (100) films ranging from 7.5 to 1 nm. We observe a low-temperature (300 K) insulating phase with evidence of vanadium-vanadium (V-V) dimers and a high-temperature (400 K) metallic phase absent of V-V dimers irrespective of film thickness. Our results confirm that the metal insulator transition can exist at atomic dimensions and that biaxial strain can still be used to control the temperature of its transition when the interfaces are atomically sharp. More generally, our case study highlights the benefits of using non-destructive XAS and HAXPES to extract out information regarding the interfacial quality of the epilayers and spectroscopic signatures associated with exotic phenomena at these dimensions.

  5. X-ray Spectroscopy of Ultra-thin Oxide/oxide Heteroepitaxial Films: A Case Study of Single-nanometer VO2/TiO2

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Quackenbush, Nicholas F.; Paik, Hanjong; Woicik, Joseph C.

    2015-08-21

    Epitaxial ultra-thin oxide films can support large percent level strains well beyond their bulk counterparts, thereby enabling strain-engineering in oxides that can tailor various phenomena. At these reduced dimensions (typically < 10 nm), contributions from the substrate can dwarf the signal from the epilayer, making it difficult to distinguish the properties of the epilayer from the bulk. This is especially true for oxide on oxide systems. Here, we have employed a combination of hard X-ray photoelectron spectroscopy (HAXPES) and angular soft X-ray absorption spectroscopy (XAS) to study epitaxial VO2/TiO2 (100) films ranging from 7.5 to 1 nm. We observe amore » low-temperature (300 K) insulating phase with evidence of vanadium-vanadium (V-V) dimers and a high-temperature (400 K) metallic phase absent of V-V dimers irrespective of film thickness. Results confirm that the metal insulator transition can exist at atomic dimensions and that biaxial strain can still be used to control the temperature of its transition when the interfaces are atomically sharp. Generally, our case study highlights the benefits of using non-destructive XAS and HAXPES to extract out information regarding the interfacial quality of the epilayers and spectroscopic signatures associated with exotic phenomena at these dimensions.« less

  6. Local Anodic Oxidation of Thin GeO Films and Formation of Nanostructures Based on Them

    NASA Astrophysics Data System (ADS)

    Astankova, K. N.; Kozhukhov, A. S.; Azarov, I. A.; Gorokhov, E. B.; Sheglov, D. V.; Latyshev, A. V.

    2018-04-01

    The process of local anodic oxidation of thin GeO films has been studied using an atomic force microscope. The electron-probe microanalysis showed that oxidized areas of a GeO film were germanium dioxide. The effect of the voltage pulse duration applied to the probe-substrate system and the atmospheric humidity on the height of the oxide structures has been studied. The kinetics of the local anodic oxidation (LAO) in a semi-contact mode obeys the Cabrera-Mott model for large times. The initial growth rate of the oxide ( R 0) significantly increases and the time of starting the oxidation ( t 0) decreases as the atmospheric humidity increases by 20%, which is related to an increase in the concentration of oxygen-containing ions at the surface of the oxidized GeO film. It was shown that nanostructures in thin GeO layers can be formed by the LAO method.

  7. Growth and interface engineering in thin-film Ba0.6Sr0.4TiO3 /SrMoO3 heterostructures

    NASA Astrophysics Data System (ADS)

    Radetinac, Aldin; Ziegler, Jürgen; Vafaee, Mehran; Alff, Lambert; Komissinskiy, Philipp

    2017-04-01

    Epitaxial heterostructures of ferroelectric Ba0.6Sr0.4TiO3 and highly conducting SrMoO3 were grown by pulsed laser deposition on SrTiO3 (0 0 1) substrates. Surface oxidation of the SrMoO3 film is suppressed using a thin cap interlayer of Ba0.6Sr0.4TiO3-δ grown in reduced atmosphere. As shown by X-ray photoelectron spectroscopy, the Mo4+ valence state of the SrMoO3 films is stable upon annealing of the sample in oxygen up to 600 °C. The described oxygen interface engineering enables utilization of the highly conducting material SrMoO3 in multilayer oxide ferroelectric varactors.

  8. Fabrication of Co3O4 mesoporous thin films by using cobalt/chitosan precursor on fluorine-doped tin oxide glass

    NASA Astrophysics Data System (ADS)

    Yang, Hui-Chia; Tsai, Jung-Che

    2017-06-01

    For the development of high-performance and low-cost electrode materials, many alternative materials have been fabricated by various groups. Among these materials, Co3O4 has been demonstrated to be a promising candidate for pseudocapacitors because of its low potential environmental pollution, low cost, and extremely high theoretical specific capacitance. Chitosan, a linear polysaccharide produced by the deacetylation of chitin, is a nontoxic, tissue-compatible polymeric biomaterial. It is usually used to eliminate or filter the heavy metals in wastewater. That is, chitosan can act as a deliverer of metal ions and a nanostructure constructer of metals (or metal oxides). In this study, a facile approach is developed to synthesize mesoporous cobalt oxide thin films on fluorine-doped tin oxide (FTO)-coated glass with environmentally friendly chitosan, which chelates cobalt ions.

  9. Bi-layer channel structure-based oxide thin-film transistors consisting of ZnO and Al-doped ZnO with different Al compositions and stacking sequences

    NASA Astrophysics Data System (ADS)

    Cho, Sung Woon; Yun, Myeong Gu; Ahn, Cheol Hyoun; Kim, So Hee; Cho, Hyung Koun

    2015-03-01

    Zinc oxide (ZnO)-based bi-layers, consisting of ZnO and Al-doped ZnO (AZO) layers grown by atomic layer deposition, were utilized as the channels of oxide thin-film transistors (TFTs). Thin AZO layers (5 nm) with different Al compositions (5 and 14 at. %) were deposited on top of and beneath the ZnO layers in a bi-layer channel structure. All of the bi-layer channel TFTs that included the AZO layers showed enhanced stability (Δ V Th ≤ 3.2 V) under a positive bias stress compared to the ZnO single-layer channel TFT (Δ V Th = 4.0 V). However, the AZO/ZnO bi-layer channel TFTs with an AZO interlayer between the gate dielectric and the ZnO showed a degraded field effect mobility (0.3 cm2/V·s for 5 at. % and 1.8 cm2/V·s for 14 at. %) compared to the ZnO single-layer channel TFT (5.5 cm2/V·s) due to increased scattering caused by Al-related impurities near the gate dielectric/channel interface. In contrast, the ZnO/AZO bi-layer channel TFTs with an AZO layer on top of the ZnO layer exhibited an improved field effect mobility (7.8 cm2/V·s for 14 at. %) and better stability. [Figure not available: see fulltext.

  10. Coexisting nanoscale inverse spinel and rock salt crystallographic phases in NiCo2O4 epitaxial thin films grown by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Sharona, H.; Loukya, B.; Bhat, U.; Sahu, R.; Vishal, B.; Silwal, P.; Gupta, A.; Datta, R.

    2017-12-01

    The origin of alternating wavy dark-bright stripe-like contrast in strain contrast transmission electron microscopy images of NiCo2O4 (NCO) epitaxial thin films grown by pulsed laser deposition has been investigated. The nanoscale stripe-like pattern is determined to be associated with coexisting rock salt (RS) and inverse spinel crystal phases. The presence of two different phases, not addressed in previous reports, is experimentally confirmed by both electron diffraction and high resolution transmission electron microscopy imaging. First principles based calculations, together with compressive strain present in the films, support the formation of such coexisting crystallographic phases in NCO. Similar microstructural patterns and RS structure are not observed in epitaxial films of two other oxides of the spinel family, namely, NiFe2O4 and CoFe2O4. A correlation between the coexisting structures and the macroscopic physical properties of NCO is discussed.

  11. Biocompatible Nb2O5 thin films prepared by means of the sol-gel process.

    PubMed

    Velten, D; Eisenbarth, E; Schanne, N; Breme, J

    2004-04-01

    Thin biocompatible oxide films with an optimised composition and structure on the surface of titanium and its alloys can improve the implant integration. The preparation of these thin oxide layers with the intended improvement of the surface properties can be realised by means of the sol-gel process. Nb2O5 is a promising coating material for this application because of its extremely high corrosion resistance and thermodynamic stability. In this study, thin Nb2O5 layers ( < 200 nm) were prepared by spin coating of polished discs of cp-titanium with a sol consisting of a mixture of niobium ethoxide, butanol and acetylacetone. The thickness, phase composition, corrosion resistance and the wettability of the oxide layers were determined after an optimisation of the processing parameters for deposition of oxide without any organic impurities. The purity of the oxide layer is an important aspect in order to avoid a negative response to the cell adhesion. The biocompatibility of the oxide layers which was investigated by in vitro tests (morphology, proliferation rate, WST-1, cell spreading) is improved as compared to uncoated and TiO2 sol-gel coated cp-titanium concerning the spreading of cells, collagen I synthesis and wettability.

  12. CuAlO2 and CuAl2O4 thin films obtained by stacking Cu and Al films using physical vapor deposition

    NASA Astrophysics Data System (ADS)

    Castillo-Hernández, G.; Mayén-Hernández, S.; Castaño-Tostado, E.; DeMoure-Flores, F.; Campos-González, E.; Martínez-Alonso, C.; Santos-Cruz, J.

    2018-06-01

    CuAlO2 and CuAl2O4 thin films were synthesized by the deposition of the precursor metals using the physical vapor deposition technique and subsequent annealing. Annealing was carried out for 4-6 h in open and nitrogen atmospheres respectively at temperatures of 900-1000 °C with control of heating and cooling ramps. The band gap measurements ranged from 3.3 to 4.5 eV. Electrical properties were measured using the van der Pauw technique. The preferred orientations of CuAlO2 and CuAl2O4 were found to be along the (1 1 2) and (3 1 1) planes, respectively. The phase percentages were quantified using a Rietveld refinement simulation and the energy dispersive X-ray spectroscopy indicated that the composition is very close to the stoichiometry of CuAlO2 samples and with excess of aluminum and deficiency of copper for CuAl2O4 respectively. High resolution transmission electron microscopy identified the principal planes in CuAlO2 and in CuAl2O4. Higher purities were achieved in nitrogen atmosphere with the control of the cooling ramps.

  13. Structural and optical properties of SiC-SiO2 nanocomposite thin films

    NASA Astrophysics Data System (ADS)

    Bozetine, I.; Keffous, A.; Kaci, S.; Menari, H.; Manseri, A.

    2018-03-01

    This study deals with the deposition of thin films of a SiC-SiO2nanocomposite deposited on silicon substrates. The deposition is carried out by a co-sputtering RF magnetron 13.56 MHz, using two targets a polycristallin 6H-SiC and sprigs of SiO2. In order to study the influence of the deposition time on the morphology, the structural and optical properties of the thin films produced, two series of samples were prepared, namely a series A with a 30 min deposition time and a series B of one hour duration. The samples were investigated using different characterization techniques such as Scanning Electron Microscope (SEM), X-ray Diffraction (DRX), Fourier Transform Infrared Spectroscopy (FTIR), Secondary Ion Mass Spectrometry (SIMS) and photoluminescence. The results obtained, reveal an optical gap varies between 1.4 and 2.4 eV depending on the thickness of the film; thus depending on the deposition time. The SIMS profile recorded the presence of oxygen (16O) on the surface, which the signal beneath the silicon signal (28Si) and carbon (12C) signals, which confirms that the oxide (SiO2) is the first material deposited at the interface film - substrate with an a-OSiC structure. The photoluminescence (PL) measurement exhibits two peaks, centred at 390 nm due to the oxide and at 416 nm due probably to the nanocrystals of SiC crystals, note that when the deposition time increases, the intensity of the PL drops drastically, result in agreement with dense and smooth film.

  14. Reaction mechanisms at 4H-SiC/SiO2 interface during wet SiC oxidation

    NASA Astrophysics Data System (ADS)

    Akiyama, Toru; Hori, Shinsuke; Nakamura, Kohji; Ito, Tomonori; Kageshima, Hiroyuki; Uematsu, Masashi; Shiraishi, Kenji

    2018-04-01

    The reaction processes at the interface between SiC with 4H structure (4H-SiC) and SiO2 during wet oxidation are investigated by electronic structure calculations within the density functional theory. Our calculations for 4H-SiC/SiO2 interfaces with various orientations demonstrate characteristic features of the reaction depending on the crystal orientation of SiC: On the Si-face, the H2O molecule is stable in SiO2 and hardly reacts with the SiC substrate, while the O atom of H2O can form Si-O bonds at the C-face interface. Two OH groups are found to be at least necessary for forming new Si-O bonds at the Si-face interface, indicating that the oxidation rate on the Si-face is very low compared with that on the C-face. On the other hand, both the H2O molecule and the OH group are incorporated into the C-face interface, and the energy barrier for OH is similar to that for H2O. By comparing the calculated energy barriers for these reactants with the activation energies of oxide growth rate, we suggest the orientation-dependent rate-limiting processes during wet SiC oxidation.

  15. Acetaldehyde Adsorption and Reaction onCeO2(100) Thin Films

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Mullins, David R; Albrecht, Peter M

    2013-01-01

    This study reports and compares the adsorption and dissociation of acetaldehyde on oxidized and reduced CeOX(100) thin films. Acetaldehyde reacts and decomposes on fully oxidized CeO2(100) whereas it desorbs molecularly at low temperature on CeO2(111). The primary products are CO, CO2 and water along with trace amounts of crotonaldehyde and acetylene. The acetaldehyde adsorbs as the 2-acetaldehyde species, dioxyethylene. Decomposition proceeds by dehydrogenation through acetate and enolate intermediates. The reaction pathway is similar on the reduced CeO2-X(100) surface however the inability to react with surface O on the reduced surface results in H2 rather than H2O desorption and C ismore » left on the surface rather than producing CO and CO2. C-O bond cleavage in the enolate intermediate followed by reaction with surface H results in ethylene desorption.« less

  16. XPS and EELS characterization of Mn2SiO4, MnSiO3 and MnAl2O4

    NASA Astrophysics Data System (ADS)

    Grosvenor, A. P.; Bellhouse, E. M.; Korinek, A.; Bugnet, M.; McDermid, J. R.

    2016-08-01

    X-ray Photoelectron Spectroscopy (XPS) and Electron Energy Loss Spectroscopy (EELS) are strong candidate techniques for characterizing steel surfaces and substrate-coating interfaces when investigating the selective oxidation and reactive wetting of advanced high strength steels (AHSS) during the continuous galvanizing process. However, unambiguous identification of ternary oxides such as Mn2SiO4, MnSiO3, and MnAl2O4 by XPS or EELS, which can play a significant role in substrate reactive wetting, is difficult due to the lack of fully characterized standards in the literature. To resolve this issue, samples of Mn2SiO4, MnSiO3 and MnAl2O4 were synthesized and characterized by XPS and EELS. The unique features of the XPS and EELS spectra for the Mn2SiO4, MnSiO3 and MnAl2O4 standards were successfully derived, thereby allowing investigators to fully differentiate and identify these oxides at the surface and subsurface of Mn, Si and Al alloyed AHSS using these techniques.

  17. Investigation of microstructure, micro-mechanical and optical properties of HfTiO{sub 4} thin films prepared by magnetron co-sputtering

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Mazur, Michal, E-mail: michal.mazur@pwr.edu.pl; Wojcieszak, Damian; Domaradzki, Jaroslaw

    2015-12-15

    Highlights: • HfTiO{sub 4} thin films were deposited by magnetron co-sputtering. • As-prepared and annealed at 800 °C thin films were nanocrystalline. • Optical properties and hardness were investigated in relation to thin films structure. • Hardness was 3-times higher in the case of as-deposited thin films. • HfTiO{sub 4} thin films are suitable for use as optical coatings with protective properties. - Abstract: Titania (TiO{sub 2}) and hafnium oxide (HfO{sub 2}) thin films are in the focus of interest to the microelectronics community from a dozen years. Because of their outstanding properties like, among the others, high stability, highmore » refractive index, high electric permittivity, they found applications in many optical and electronics domains. In this work discussion on the hardness, microstructure and optical properties of as-deposited and annealed HfTiO{sub 4} thin films has been presented. Deposited films were prepared using magnetron co-sputtering method. Performed investigations revealed that as-deposited coatings were nanocrystalline with HfTiO{sub 4} structure. Deposited films were built from crystallites of ca. 4–12 nm in size and after additional annealing an increase in crystallites size up to 16 nm was observed. Micro-mechanical properties, i.e., hardness and elastic modulus were determined using conventional load-controlled nanoindentation testing. the annealed films had 3-times lower hardness as-compared to as-deposited ones (∼9 GPa). Based on optical investigations real and imaginary components of refractive index were calculated, both for as-deposited and annealed thin films. The real refractive index component increased after annealing from 2.03 to 2.16, while extinction coefficient increased by an order from 10{sup −4} to 10{sup −3}. Structure modification was analyzed together with optical energy band-gap, Urbach energy and using Wemple–DiDomenico model.« less

  18. Investigation of interface property in Al/SiO2/ n-SiC structure with thin gate oxide by illumination

    NASA Astrophysics Data System (ADS)

    Chang, P. K.; Hwu, J. G.

    2017-04-01

    The reverse tunneling current of Al/SiO2/ n-SiC structure employing thin gate oxide is introduced to examine the interface property by illumination. The gate current at negative bias decreases under blue LED illumination, yet increases under UV lamp illumination. Light-induced electrons captured by interface states may be emitted after the light sources are off, leading to the recovery of gate currents. Based on transient characteristics of gate current, the extracted trap level is close to the light energy for blue LED, indicating that electron capture induced by lighting may result in the reduction of gate current. Furthermore, bidirectional C- V measurements exhibit a positive voltage shift caused by electron trapping under blue LED illumination, while a negative voltage shift is observed under UV lamp illumination. Distinct trapping and detrapping behaviors can be observed from variations in I- V and C- V curves utilizing different light sources for 4H-SiC MOS capacitors with thin insulators.

  19. Thickness-modulated anisotropic ferromagnetism in Fe-doped epitaxial HfO2 thin films

    NASA Astrophysics Data System (ADS)

    Liu, Wenlong; Liu, Ming; Zhang, Ruyi; Ma, Rong; Wang, Hong

    2017-10-01

    Epitaxial tetragonal Fe-doped Hf0.95Fe0.05O2 (FHO) thin films with various thicknesses were deposited on (001)-oriented NdCaAlO4 (NCAO) substrates by using a pulsed laser deposition (PLD) system. The crystal structure and epitaxial nature of the FHO thin films were confirmed by typical x-ray diffraction (XRD) θ-2θ scan and reciprocal space mapping (RSM). The results indicate that two sets of lattice sites exist with two different crystal orientations [(001) and (100)] in the thicker FHO thin films. Further, the intensity of the (100) direction increases with the increase in thicknesses, which should have a significant effect on the anisotropic magnetization of the FHO thin films. Meanwhile, all the FHO thin films possess a tetragonal phase structure. An anisotropy behavior in magnetization has been observed in the FHO thin films. The anisotropic magnetization of the FHO thin films is slowly weakened as the thickness increases. Meanwhile, the saturation magnetization (Ms) of both in-plane and out-of-plane decreases with the increase in the thickness. The change in the anisotropic magnetization and Ms is attributed to the crystal lattice and the variation in the valence of Fe ions. These results indicate that the thickness-modulated anisotropic ferromagnetism of the tetragonal FHO epitaxial thin films is of potential use for the integration of metal-oxide semiconductors with spintronics.

  20. Ultrahigh-Performance Cu2ZnSnS4 Thin Film and Its Application in Microscale Thin-Film Lithium-Ion Battery: Comparison with SnO2.

    PubMed

    Lin, Jie; Guo, Jianlai; Liu, Chang; Guo, Hang

    2016-12-21

    To develop a high-performance anode for thin-film lithium-ion batteries (TFBs, with a total thickness on the scale of micrometers), a Cu 2 ZnSnS 4 (CZTS) thin film is fabricated by magnetron sputtering and exhibits an ultrahigh performance of 950 mAh g -1 even after 500 cycles, which is the highest among the reported CZTS for lithium storage so far. The characterization and electrochemical tests reveal that the thin-film structure and additional reactions both contribute to the excellent properties. Furthermore, the microscale TFBs with effective footprints of 0.52 mm 2 utilizing the CZTS thin film as anode are manufactured by microfabrication techniques, showing superior capability than the analogous TFBs with the SnO 2 thin film as anode. This work demonstrates the advantages of exploiting thin-film electrodes and novel materials into micropower sources by electronic manufacture methods.

  1. Effect of oxygen deficiency on electronic properties and local structure of amorphous tantalum oxide thin films

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Denny, Yus Rama; Firmansyah, Teguh; Oh, Suhk Kun

    2016-10-15

    Highlights: • The effect of oxygen flow rate on electronic properties and local structure of tantalum oxide thin films was studied. • The oxygen deficiency induced the nonstoichiometric state a-TaOx. • A small peak at 1.97 eV above the valence band side appeared on nonstoichiometric Ta{sub 2}O{sub 5} thin films. • The oxygen flow rate can change the local electronic structure of tantalum oxide thin films. - Abstract: The dependence of electronic properties and local structure of tantalum oxide thin film on oxygen deficiency have been investigated by means of X-ray photoelectron spectroscopy (XPS), Reflection Electron Energy Loss Spectroscopy (REELS),more » and X-ray absorption spectroscopy (XAS). The XPS results showed that the oxygen flow rate change results in the appearance of features in the Ta 4f at the binding energies of 23.2 eV, 24.4 eV, 25.8, and 27.3 eV whose peaks are attributed to Ta{sup 1+}, Ta{sup 2+}, Ta{sup 3+}/Ta{sup 4+}, and Ta{sup 5+}, respectively. The presence of nonstoichiometric state from tantalum oxide (TaOx) thin films could be generated by the oxygen vacancies. In addition, XAS spectra manifested both the increase of coordination number of the first Ta-O shell and a considerable reduction of the Ta-O bond distance with the decrease of oxygen deficiency.« less

  2. Improvement of Self-Heating of Indium Gallium Zinc Aluminum Oxide Thin-Film Transistors Using Al2O3 Barrier Layer

    NASA Astrophysics Data System (ADS)

    Jian, Li-Yi; Lee, Hsin-Ying; Lin, Yung-Hao; Lee, Ching-Ting

    2018-02-01

    To study the self-heating effect, aluminum oxide (Al2O3) barrier layers of various thicknesses have been inserted between the channel layer and insulator layer in bottom-gate-type indium gallium zinc aluminum oxide (IGZAO) thin-film transistors (TFTs). Each IGZAO channel layer was deposited on indium tin oxide (ITO)-coated glass substrate by using a magnetron radiofrequency cosputtering system with dual targets composed of indium gallium zinc oxide (IGZO) and Al. The 3 s orbital of Al cation provided an extra transport pathway and widened the conduction-band bottom, thus increasing the electron mobility of the IGZAO films. The Al-O bonds were able to sustain the oxygen stability of the IGZAO films. The self-heating behavior of the resulting IGZAO TFTs was studied by Hall measurements on the IGZAO films as well as the electrical performance of the IGZAO TFTs with Al2O3 barrier layers of various thicknesses at different temperatures. IGZAO TFTs with 50-nm-thick Al2O3 barrier layer were stressed by positive gate bias stress (PGBS, at gate-source voltage V GS = 5 V and drain-source voltage V DS = 0 V); at V GS = 5 V and V DS = 10 V, the threshold voltage shifts were 0.04 V and 0.2 V, respectively, much smaller than for the other IGZAO TFTs without Al2O3 barrier layer, which shifted by 0.2 V and 1.0 V when stressed under the same conditions.

  3. Direct observation of pure pentavalent uranium in U2O5 thin films by high resolution photoemission spectroscopy.

    PubMed

    Gouder, T; Eloirdi, R; Caciuffo, R

    2018-05-29

    Thin films of the elusive intermediate uranium oxide U 2 O 5 have been prepared by exposing UO 3 precursor multilayers to atomic hydrogen. Electron photoemission spectra measured about the uranium 4f core-level doublet contain sharp satellites separated by 7.9(1) eV from the 4f main lines, whilst satellites characteristics of the U(IV) and U(VI) oxidation states, expected respectively at 6.9(1) and 9.7(1) eV from the main 4f lines, are absent. This shows that uranium ions in the films are in a pure pentavalent oxidation state, in contrast to previous investigations of binary oxides claiming that U(V) occurs only as a metastable intermediate state coexisting with U(IV) and U(VI) species. The ratio between the 5f valence band and 4f core-level uranium photoemission intensities decreases by about 50% from UO 2 to U 2 O 5 , which is consistent with the 5f  2 (UO 2 ) and 5f  1 (U 2 O 5 ) electronic configurations of the initial state. Our studies conclusively establish the stability of uranium pentoxide.

  4. A highly efficient Li2O2 oxidation system in Li-O2 batteries.

    PubMed

    Hase, Yoko; Seki, Juntaro; Shiga, Tohru; Mizuno, Fuminori; Nishikoori, Hidetaka; Iba, Hideki; Takechi, Kensuke

    2016-10-06

    A novel indirect charging system that uses a redox mediator was demonstrated for Li-O 2 batteries. 4-Methoxy-2,2,6,6-tetramethylpiperidinyl-1-oxyl (MeO-TEMPO) was applied as a mediator to enable the oxidation of Li 2 O 2 , even though Li 2 O 2 is electrochemically isolated. This system promotes the oxidation of Li 2 O 2 without parasitic reactions attributed to electrochemical charging and reduces the charging time.

  5. The Relationship of the Silicon Surface Roughness and Gate Oxide Integrity in NH4OH/H2O2 Mixtures

    NASA Astrophysics Data System (ADS)

    Meuris, M.; Verhaverbeke, S.; Mertens, P. W.; Heyns, M. M.; Hellemans, L.; Bruynseraede, Y.; Philipossian, A.

    1992-11-01

    In this study some recent findings on the cleaning action of the NH4OH/H2O2 (SC1) step in a pre-gate oxidation cleaning (RCA cleaning) are given. An important parameter in this mixture is the NH4OH/H2O2 ratio. The Fe contamination on the silicon surface after this cleaning step is found to increase upon decreasing the NH4OH/H2O2 ratio. This can be attributed to the incorporation of Fe in the chemical oxide, grown by the hydrogen peroxide. The particle removal efficiency of the cleaning step is found to decrease upon decreasing the NH4OH/H2O2 ratio. On the other hand, using a lower NH4OH concentration results in a less severe silicon surface roughening. It is demonstrated in this study that the NH4OH/H2O2 ratio during the SC1 step of the cleaning is the determining parameter for the breakdown properties of a gate oxide. A (0.25/1/5) NH4OH/H2O2/H2O mixture at 75°C in our experimental conditions is suggested to be the best compromise between particle removal and surface roughness during the SC1 step.

  6. Mechanisms of LiCoO2 Cathode Degradation by Reaction with HF and Protection by Thin Oxide Coatings.

    PubMed

    Tebbe, Jonathon L; Holder, Aaron M; Musgrave, Charles B

    2015-11-04

    Reactions of HF with uncoated and Al and Zn oxide-coated surfaces of LiCoO2 cathodes were studied using density functional theory. Cathode degradation caused by reaction of HF with the hydroxylated (101̅4) LiCoO2 surface is dominated by formation of H2O and a LiF precipitate via a barrierless reaction that is exothermic by 1.53 eV. We present a detailed mechanism where HF reacts at the alumina coating to create a partially fluorinated alumina surface rather than forming AlF3 and H2O and thus alumina films reduce cathode degradation by scavenging HF and avoiding H2O formation. In contrast, we find that HF etches monolayer zinc oxide coatings, which thus fail to prevent capacity fading. However, thicker zinc oxide films mitigate capacity loss by reacting with HF to form a partially fluorinated zinc oxide surface. Metal oxide coatings that react with HF to form hydroxyl groups over H2O, like the alumina monolayer, will significantly reduce cathode degradation.

  7. Ni: Fe2O3, Mg: Fe2O3 and Fe2O3 thin films gas sensor application

    NASA Astrophysics Data System (ADS)

    Saritas, Sevda; Kundakci, Mutlu; Coban, Omer; Tuzemen, Sebahattin; Yildirim, Muhammet

    2018-07-01

    Iron oxide is a widely used sensitive material for gas sensor applications. They have fascinated much attention in the field of gas sensing and detecting under atmospheric conditions and at 200 °C temperature due to their low cost in production; simplicity and fast of their use; large number of detectable gases. Iron oxide gas sensors constitute investigated for hazardous gases used in various fields. The morphological structure (particle size, pore size, etc.), optical, magnetic and electrical properties of Ni:Fe2O3, Mg:Fe2O3 and Fe2O3 thin films which grown by Spray pyrolysis (SP) have been investigated. XRD, Raman and AFM techniques have been used for structural analysis. AFM measurements have been provided very useful information about surface topography. I-V (Van der Pauw) technique has been used for response of gas sensor. These devices offer a wide variety of advantages over traditional analytical instruments such as low cost, short response time, easy manufacturing, and small size.

  8. Fabrication and characterization of {110}-oriented Pb(Zr,Ti)O3 thin films on Pt/SiO2/Si substrates using PdO//Pd buffer layer

    NASA Astrophysics Data System (ADS)

    Oshima, Naoya; Uchiyama, Kiyoshi; Ehara, Yoshitaka; Oikawa, Takahiro; Ichinose, Daichi; Tanaka, Hiroki; Sato, Tomoya; Uchida, Hiroshi; Funakubo, Hiroshi

    2017-10-01

    A strongly {110}-oriented perovskite-type thin film of tetragonal Pb(Zr0.4Ti0.6)O3 (PZT) was successfully obtained on a (100)Si substrate using a {101}PdO//{111}Pd thin film as a buffer layer. The {101}PdO//{111}Pd thin film buffer layer was obtained by oxidizing {111}Pd after depositing {111}Pd on a {111}Pt/TiO x /SiO2/{100}Si substrate. Using this buffer layer, a {110} c -oriented SrRuO3 (SRO) thin film was deposited by sputtering as a bottom electrode of PZT thin films. Subsequently, the {110}-oriented PZT thin film can be deposited on a (110) c SRO thin film by metal-organic chemical deposition (MOCVD) and its properties can be compared with those of PZT thin films with other orientations of {100} and {111}. Among the {100}, {110}, {111}-oriented PZT films, the {100}-oriented one showed the largest remnant polarization, which is in good agreement with those of the PZTs epitaxially grown in the 〈100〉, 〈110〉, and 〈111〉 directions. The other properties, i.e., piezoelectricity and dielectric constants, also showed similar anisotropic tendencies, which is in good agreement with the data reported in the epitaxially grown PZTs.

  9. Strain Effects in Epitaxial VO2 Thin Films on Columnar Buffer-Layer TiO2/Al2O3 Virtual Substrates.

    PubMed

    Breckenfeld, Eric; Kim, Heungsoo; Burgess, Katherine; Charipar, Nicholas; Cheng, Shu-Fan; Stroud, Rhonda; Piqué, Alberto

    2017-01-18

    Epitaxial VO 2 /TiO 2 thin film heterostructures were grown on (100) (m-cut) Al 2 O 3 substrates via pulsed laser deposition. We have demonstrated the ability to reduce the semiconductor-metal transition (SMT) temperature of VO 2 to ∼44 °C while retaining a 4 order of magnitude SMT using the TiO 2 buffer layer. A combination of electrical transport and X-ray diffraction reciprocal space mapping studies help examine the specific strain states of VO 2 /TiO 2 /Al 2 O 3 heterostructures as a function of TiO 2 film growth temperatures. Atomic force microscopy and transmission electron microscopy analyses show that the columnar microstructure present in TiO 2 buffer films is responsible for the partially strained VO 2 film behavior and subsequently favorable transport characteristics with a lower SMT temperature. Such findings are of crucial importance for both the technological implementation of the VO 2 system, where reduction of its SMT temperature is widely sought, as well as the broader complex oxide community, where greater understanding of the evolution of microstructure, strain, and functional properties is a high priority.

  10. Nanoporous structures on ZnO thin films

    NASA Astrophysics Data System (ADS)

    Gür, Emre; Kılıç, Bayram; Coşkun, C.; Tüzemen, S.; Bayrakçeken, Fatma

    2010-01-01

    Porous structures were formed on ZnO thin films which were grown by an electrochemical deposition (ECD) method. The growth processes were carried out in a solution of dimethylsulfoxide (DMSO) zinc perchlorate, Zn(ClO 4) 2, at 120 ∘C on indium tin oxide (ITO) substrates. Optical and structural characterizations of electrochemically grown ZnO thin films have shown that the films possess high (0002) c-axis orientation, high nucleation, high intensity and low FWHM of UV emission at the band edge region and a sharp UV absorption edge. Nanoporous structures were formed via self-assembled monolayers (SAMs) of hexanethiol (C 6SH) and dodecanethiol (C 12SH). Scanning electron microscope (SEM) measurements showed that while a nanoporous structure (pore radius 20 nm) is formed on the ZnO thin films by hexanathiol solution, a macroporous structure (pore radius 360 nm) is formed by dodecanethiol solution. No significant variation is observed in X-ray diffraction (XRD) measurements on the ZnO thin films after pore formation. However, photoluminescence (PL) measurements showed that green emission is observed as the dominant emission for the macroporous structures, while no variation is observed for the thin film nanoporous ZnO sample.

  11. Optical characterization of sputtered YBaCo 4O 7+ δ thin films

    NASA Astrophysics Data System (ADS)

    Montoya, J. F.; Izquierdo, J. L.; Causado, J. D.; Bastidas, A.; Nisperuza, D.; Gómez, A.; Arnache, O.; Osorio, J.; Marín, J.; Paucar, C.; Morán, O.

    2011-02-01

    Thin films of YBaCo 4O 7+ δ were deposited on r (1012)-oriented Al 2O 3 substrates by dc magnetron sputtering. The as-grown films were characterized after their structural, morphological and optical properties. Special attention is devoted to the analysis of the optical response of these films as reports on optical properties of YBaCo 4O 7+ δ, especially in thin film form, are not frequently reported in the literature. Transmittance/absorbance measurements allow for determining two well defined energy gaps at 3.7 and 2.2 eV. In turn, infrared (IR) measurements show infrared transparency in the wave length range 4000-2500 nm with a sharp absorption edge at wave lengths less than 2500 nm. Complementary Raman spectra measurements on the thin films allowed for identifying bands associated with vibrating modes of CoO 4 and YO 6 in tetrahedral and octahedral oxygen coordination, respectively. Additional bands which seemed to stem from Co ions in octahedral oxygen coordination were also clearly identified.

  12. Nanomechanical study of amorphous and polycrystalline ALD HfO2 thin films

    Treesearch

    K. Tapily; J.E. Jakes; D. Gu; H. Baumgart; A.A. Elmustafa

    2011-01-01

    Thin films of hafnium oxide (HfO2) were deposited by atomic layer deposition (ALD). The structural properties of the deposited films were characterised by transmission electron microscopy (TEM) and X-ray diffraction (XRD). We investigated the effect of phase transformations induced by thermal treatments on the mechanical properties of ALD HfO

  13. Zirconium doped TiO{sub 2} thin films: A promising dielectric layer

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kumar, Arvind; Mondal, Sandip, E-mail: sandipmondal@physics.iisc.ernet.in; Rao, K. S. R. Koteswara

    2016-05-06

    In the present work, we have fabricated the zirconium doped TiO{sub 2} thin (ZTO) films from a facile spin – coating method. The addition of Zirconium in TiO{sub 2} offers conduction band offset to Si and consequently decreased the leakage current density by approximately two orders as compared to pure TiO{sub 2} thin (TO) films. The ZTO thin film shows a high dielectric constant 27 with a very low leakage current density ∼10{sup −8} A/cm{sup 2}. The oxide capacitate, flat band voltage and change in flat band voltage are 172 pF, -1.19 V and 54 mV. The AFM analysis confirmed the compactmore » and pore free flat surface. The RMS surface roughness is found to be 1.5 Å. The ellipsometry analysis also verified the fact with a high refractive index 2.21.« less

  14. Nanoporous cerium oxide thin film for glucose biosensor.

    PubMed

    Saha, Shibu; Arya, Sunil K; Singh, S P; Sreenivas, K; Malhotra, B D; Gupta, Vinay

    2009-03-15

    Nanoporous cerium oxide (CeO(2)) thin film deposited onto platinum (Pt) coated glass plate using pulsed laser deposition (PLD) has been utilized for immobilization of glucose oxidase (GOx). Atomic force microscopy studies reveal the formation of nanoporous surface morphology of CeO(2) thin film. Response studies carried out using differential pulsed voltammetry (DPV) and optical measurements show that the GOx/CeO(2)/Pt bio-electrode shows linearity in the range of 25-300 mg/dl of glucose concentration. The low value of Michaelis-Menten constant (1.01 mM) indicates enhanced enzyme affinity of GOx to glucose. The observed results show promising application of the nanoporous CeO(2) thin film for glucose sensing application without any surface functionalization or mediator.

  15. Optimization of NO oxidation by H2O2 thermal decomposition at moderate temperatures.

    PubMed

    Zhao, Hai-Qian; Wang, Zhong-Hua; Gao, Xing-Cun; Liu, Cheng-Hao; Qi, Han-Bing

    2018-01-01

    H2O2 was adopted to oxidize NO in simulated flue gas at 100-500°C. The effects of the H2O2 evaporation conditions, gas temperature, initial NO concentration, H2O2 concentration, and H2O2:NO molar ratio on the oxidation efficiency of NO were investigated. The reason for the narrow NO oxidation temperature range near 500°C was determined. The NO oxidation products were analyzed. The removal of NOx using NaOH solution at a moderate oxidation ratio was studied. It was proven that rapid evaporation of the H2O2 solution was critical to increase the NO oxidation efficiency and broaden the oxidation temperature range. the NO oxidation efficiency was above 50% at 300-500°C by contacting the outlet of the syringe needle and the stainless-steel gas pipe together to spread H2O2 solution into a thin film on the surface of the stainless-steel gas pipe, which greatly accelerated the evaporation of H2O2. The NO oxidation efficiency and the NO oxidation rate increased with increasing initial NO concentration. This method was more effective for the oxidation of NO at high concentrations. H2O2 solution with a concentration higher than 15% was more efficient in oxidizing NO. High temperatures decreased the influence of the H2O2 concentration on the NO oxidation efficiency. The oxidation efficiency of NO increased with an increase in the H2O2:NO molar ratio, but the ratio of H2O2 to oxidized NO decreased. Over 80% of the NO oxidation product was NO2, which indicated that the oxidation ratio of NO did not need to be very high. An 86.7% NO removal efficiency was obtained at an oxidation ratio of only 53.8% when combined with alkali absorption.

  16. Optimization of NO oxidation by H2O2 thermal decomposition at moderate temperatures

    PubMed Central

    Wang, Zhong-hua; Gao, Xing-cun; Liu, Cheng-hao; Qi, Han-bing

    2018-01-01

    H2O2 was adopted to oxidize NO in simulated flue gas at 100–500°C. The effects of the H2O2 evaporation conditions, gas temperature, initial NO concentration, H2O2 concentration, and H2O2:NO molar ratio on the oxidation efficiency of NO were investigated. The reason for the narrow NO oxidation temperature range near 500°C was determined. The NO oxidation products were analyzed. The removal of NOx using NaOH solution at a moderate oxidation ratio was studied. It was proven that rapid evaporation of the H2O2 solution was critical to increase the NO oxidation efficiency and broaden the oxidation temperature range. the NO oxidation efficiency was above 50% at 300–500°C by contacting the outlet of the syringe needle and the stainless-steel gas pipe together to spread H2O2 solution into a thin film on the surface of the stainless-steel gas pipe, which greatly accelerated the evaporation of H2O2. The NO oxidation efficiency and the NO oxidation rate increased with increasing initial NO concentration. This method was more effective for the oxidation of NO at high concentrations. H2O2 solution with a concentration higher than 15% was more efficient in oxidizing NO. High temperatures decreased the influence of the H2O2 concentration on the NO oxidation efficiency. The oxidation efficiency of NO increased with an increase in the H2O2:NO molar ratio, but the ratio of H2O2 to oxidized NO decreased. Over 80% of the NO oxidation product was NO2, which indicated that the oxidation ratio of NO did not need to be very high. An 86.7% NO removal efficiency was obtained at an oxidation ratio of only 53.8% when combined with alkali absorption. PMID:29668672

  17. Sc-substituted La0.6Sr0.4FeO3-δ mixed conducting oxides as promising electrodes for symmetrical solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Liu, Xuejiao; Han, Da; Zhou, Yucun; Meng, Xie; Wu, Hao; Li, Junliang; Zeng, Fanrong; Zhan, Zhongliang

    2014-01-01

    The main barrier to symmetrical solid oxide fuel cells (SOFCs), where the same catalytic materials are used simultaneously as the anodes and the cathodes, is to identify a redox-stable catalyst that exhibits superior catalytic activities for both fuel oxidation and oxygen reduction reactions. Here we report a Sc-substituted La0.6Sr0.4FeO3-δ oxide, La0.6Sr0.4Fe0.9Sc0.1O3-δ, that shows great promise as a new symmetrical electrode material with good structural stability and reasonable conductivities in air and hydrogen. We further demonstrate that nano-scale La0.6Sr0.4Fe0.9Sc0.1O3-δ catalysts impregnated into the porous La0.9Sr0.1Ga0.8Mg0.2O3-δ backbones exhibit good catalytic activities for oxygen reduction and hydrogen oxidation reactions and thereby yield low polarization resistances, e.g., 0.015 Ω cm2 in air and 0.29 Ω cm2 in hydrogen with appropriate current collection at 800 °C. Thin La0.9Sr0.1Ga0.8Mg0.2O3-δ electrolyte fuel cells with such symmetrical La0.6Sr0.4Fe0.9Sc0.1O3-δ catalysts showed maximum power densities of 0.56 and 0.32 W cm-2 when operating on 97% H2-3% H2O at 800 and 700 °C, respectively.

  18. The decomposition of mixed oxide Ag2Cu2O3: Structural features and the catalytic properties in CO and C2H4 oxidation

    NASA Astrophysics Data System (ADS)

    Svintsitskiy, Dmitry A.; Kardash, Tatyana Yu.; Slavinskaya, Elena M.; Stonkus, Olga A.; Koscheev, Sergei V.; Boronin, Andrei I.

    2018-01-01

    The mixed silver-copper oxide Ag2Cu2O3 with a paramelaconite crystal structure is a promising material for catalytic applications. The as-prepared sample of Ag2Cu2O3 consisted of brick-like particles extended along the [001] direction. A combination of physicochemical techniques such as TEM, XPS and XRD was applied to investigate the structural features of this mixed silver-copper oxide. The thermal stability of Ag2Cu2O3 was investigated using in situ XRD under different reaction conditions, including a catalytic CO + O2 mixture. The first step of Ag2Cu2O3 decomposition was accompanied by the appearance of ensembles consisting of silver nanoparticles with sizes of 5-15 nm. Silver nanoparticles were strongly oriented to each other and to the surface of the initial Ag2Cu2O3 bricks. Based on the XRD data, it was shown that the release of silver occurred along the a and b axes of the paramelaconite structure. Partial decomposition of Ag2Cu2O3 accompanied by the formation of silver nanoparticles was observed during prolonged air storage under ambient conditions. The high reactivity is discussed as a reason for spontaneous decomposition during Ag2Cu2O3 storage. The full decomposition of the mixed oxide into metallic silver and copper (II) oxide took place at temperatures higher than 300 °C regardless of the nature of the reaction medium (helium, air, CO + O2). Catalytic properties of partially and fully decomposed samples of mixed silver-copper oxide were measured in low-temperature CO oxidation and C2H4 epoxidation reactions.

  19. A facile growth process of CeO2-Co3O4 composite nanotubes and its catalytic stability for CO oxidation

    NASA Astrophysics Data System (ADS)

    Oh, Hyerim; Kim, Il Hee; Lee, Nam-Suk; Dok Kim, Young; Kim, Myung Hwa

    2017-08-01

    Hybrid cerium dioxide (CeO2)-cobalt oxide (Co3O4) composite nanotubes were successfully prepared by a combination of electrospinning and thermal annealing using CeO2 and Co3O4 precursors for the first time. Electrospun CeO2-Co3O4 composite nanotubes represent relatively porous surface texture with small dimensions between 80 and 150 nm in the outer diameter. The microscopic investigations indicate that the nanoparticle like crystalline structures of CeO2 and Co3O4 are homogenously distributed and continuously connected to form the shape of nanotube in the length of a few micrometers during thermal annealing. It is expected that the different evaporation behaviors of solvents and matrix polymer between the core and the shell in as-spun nanofibers in the course of thermal annealing could be reasonably responsible for the formation of well-defined CeO2/Co3O4 hybrid nanotubes. Additionally, the general catalytic activities of electrospun CeO2/Co3O4 hybrid nanotubes toward the oxidation of carbon monoxide (CO) were carefully examined by a continuous flow system, resulting in favorable catalytic activity as well as catalytic stability for CO oxidation between 150 °C and 200 °C without the deactivation of the catalyst with time stems from accumulation of reaction intermediates such as carbonate species.

  20. MnTiO3-driven low-temperature oxidative coupling of methane over TiO2-doped Mn2O3-Na2WO4/SiO2 catalyst

    PubMed Central

    Wang, Pengwei; Zhao, Guofeng; Wang, Yu; Lu, Yong

    2017-01-01

    Oxidative coupling of methane (OCM) is a promising method for the direct conversion of methane to ethene and ethane (C2 products). Among the catalysts reported previously, Mn2O3-Na2WO4/SiO2 showed the highest conversion and selectivity, but only at 800° to 900°C, which represents a substantial challenge for commercialization. We report a TiO2-doped Mn2O3-Na2WO4/SiO2 catalyst by using Ti-MWW zeolite as TiO2 dopant as well as SiO2 support, enabling OCM with 26% conversion and 76% C2-C3 selectivity at 720°C because of MnTiO3 formation. MnTiO3 triggers the low-temperature Mn2+↔Mn3+ cycle for O2 activation while working synergistically with Na2WO4 to selectively convert methane to C2-C3. We also prepared a practical Mn2O3-TiO2-Na2WO4/SiO2 catalyst in a ball mill. This catalyst can be transformed in situ into MnTiO3-Na2WO4/SiO2, yielding 22% conversion and 62% selectivity at 650°C. Our results will stimulate attempts to understand more fully the chemistry of MnTiO3-governed low-temperature activity, which might lead to commercial exploitation of a low-temperature OCM process. PMID:28630917

  1. Thin-Film Photoluminescent Properties and the Atomistic Model of Mg2TiO4 as a Non-rare Earth Matrix Material for Red-Emitting Phosphor

    NASA Astrophysics Data System (ADS)

    Huang, Chieh-Szu; Chang, Ming-Chuan; Huang, Cheng-Liang; Lin, Shih-kang

    2016-12-01

    Thin-film electroluminescent devices are promising solid-state lighting devices. Red light-emitting phosphor is the key component to be integrated with the well-established blue light-emitting diode chips for stimulating natural sunlight. However, environmentally hazardous rare-earth (RE) dopants, e.g. Eu2+ and Ce2+, are commonly used for red-emitting phosphors. Mg2TiO4 inverse spinel has been reported as a promising matrix material for "RE-free" red light luminescent material. In this paper, Mg2TiO4 inverse spinel is investigated using both experimental and theoretical approaches. The Mg2TiO4 thin films were deposited on Si (100) substrates using either spin-coating with the sol-gel process, or radio frequency sputtering, and annealed at various temperatures ranging from 600°C to 900°C. The crystallinity, microstructures, and photoluminescent properties of the Mg2TiO4 thin films were characterized. In addition, the atomistic model of the Mg2TiO4 inverse spinel was constructed, and the electronic band structure of Mg2TiO4 was calculated based on density functional theory. Essential physical and optoelectronic properties of the Mg2TiO4 luminance material as well as its optimal thin-film processing conditions were comprehensively reported.

  2. Formation of Fe2SiO4 thin films on Si substrates and influence of substrate to its thermoelectric transport properties

    NASA Astrophysics Data System (ADS)

    Choi, Jeongyong; Nguyen, Van Quang; Duong, Van Thiet; Shin, Yooleemi; Duong, Anh Tuan; Cho, Sunglae

    2018-03-01

    Fe2SiO4 thin films have been grown on n-type, p-type and semi-insulating Si(100) substrates by molecular beam epitaxy. When Fe-O thin films were deposited on Si(100) substrate at 300 °C, the film reacted with Si, resulting in a Fe2SiO4 film because of the high reactivity between Fe and Si. The electrical resistance and Seebeck coefficient of Fe2SiO4 thin films grown were different in different doping states. On n-type and p-type Si(100), the electrical resistance decreased suddenly and increased again at 350 and 250 K, respectively, while on semi-insulating Si(100), it exhibited typical semiconducting resistance behavior. We observed similar crossovers at 350 and 250 K in temperature dependent Seebeck coefficients on n-type and p-type Si(100), respectively. These results suggest that the measured electrical and thermoelectric properties originate from Si substrate.

  3. Tuning the Curie temperature of epitaxial Nd0.6Sr0.4MnO3 thin films

    NASA Astrophysics Data System (ADS)

    Bhat, Shwetha G.; Kumar, P. S. Anil

    2018-02-01

    NdxSr1-xMnO3 (0.2 ≤ x ≤ 0.5) systems are widely studied in magnetism, popular for high colossal magnetoresistance and are ferromagnetic oxides with TC ranging from 200 K to 300 K. Recently, many of such compounds are re-visited for exploring the correlation of spin, charge and lattice degrees of freedom. Although, manganite thin films are the ideal candidates for studying the electron-correlation effects, the puzzle of obtaining a high quality epitaxial thin films of NdxSr1-xMnO3 are still unsolved contrary to its sister compound LaxSr1-xMnO3. Hence, in this study, we demonstrate the growth of best quality of Nd0.6Sr0.4MnO3 (NSMO) epitaxial thin films. This is evident from the TC and a sharp insulator-to-metal transition (IMT) coinciding at as high as ∼255 K against the bulk TC (∼270 K). It is the highest reported TC in Nd0.6Sr0.4MnO3 thin films to date. Moreover, as-deposited films with in situ oxygen annealing are not enough to relax the lattice of NSMO films due to the significant Jahn-Teller distortion in the film. With ex situ annealing processes alongside the various deposition and in situ annealing conditions, we have extensively studied the growth of epitaxial NSMO thin films on LaAlO3 (0 0 1) and SrTiO3 (0 0 1) to investigate the evolution of lattice and its one-to-one correspondence with the magnetism and the electrical properties of thin films. Accordingly, the enhanced magnetization, reduced resistivity and the higher TC and IMT of the NSMO films obtained from our extensive growth analysis looks promising for the future applications across the TC and IMT.

  4. Comparison of the agglomeration behavior of thin metallic films on SiO2

    NASA Astrophysics Data System (ADS)

    Gadkari, P. R.; Warren, A. P.; Todi, R. M.; Petrova, R. V.; Coffey, K. R.

    2005-07-01

    The stability of continuous metallic thin films on insulating oxide surfaces is of interest to applications such as semiconductor interconnections and gate engineering. In this work, we report the study of the formation of voids and agglomeration of initially continuous Cu, Au, Ru and Pt thin films deposited on amorphous thermally grown SiO2 surfaces. Polycrystalline thin films having thicknesses in the range of 10-100 nm were ultrahigh vacuum sputter deposited on thermally grown SiO2 surfaces. The films were annealed at temperatures in the range of 150-800 °C in argon and argon+3% hydrogen gases. Scanning electron microscopy was used to investigate the agglomeration behavior, and transmission electron microscopy was used to characterize the microstructure of the as-deposited and annealed films. The agglomeration sequence in all of the films is found to follow a two step process of void nucleation and void growth. However, void growth in Au and Pt thin films is different from Cu and Ru thin films. Residual stress and adhesion were observed to play an important part in deciding the mode of void growth in Au and Pt thin films. Last, it is also observed that the tendency for agglomeration can be reduced by encapsulating the metal film with an oxide overlayer.

  5. Chlorination of UO 2, PuO 2 and rare earth oxides using ZrCl 4 in LiCl-KCl eutectic melt

    NASA Astrophysics Data System (ADS)

    Sakamura, Yoshiharu; Inoue, Tadashi; Iwai, Takashi; Moriyama, Hirotake

    2005-04-01

    A new chlorination method using ZrCl 4 in a molten salt bath has been investigated for the pyrometallurgical reprocessing of nuclear fuels. ZrCl 4 has a high reactivity with oxygen but is not corrosive to refractory metals such as steel. Rare earth oxides (La 2O 3, CeO 2, Nd 2O 3 and Y 2O 3) and actinide oxides (UO 2 and PuO 2) were allowed to react with ZrCl 4 in a LiCl-KCl eutectic salt at 773 K to give a metal chloride solution and a precipitate of ZrO 2. An addition of zirconium metal as a reductant was effective in chlorinating the dioxides. When the oxides were in powder form, the reaction was observed to progress rapidly. Cyclic voltammetry provided a convenient way of establishing when the reaction was completed. It was demonstrated that the ZrCl 4 chlorination method, free from corrosive gas, was very simple and useful.

  6. Stable Water Oxidation in Acid Using Manganese-Modified TiO2 Protective Coatings.

    PubMed

    Siddiqi, Georges; Luo, Zhenya; Xie, Yujun; Pan, Zhenhua; Zhu, Qianhong; Röhr, Jason A; Cha, Judy J; Hu, Shu

    2018-06-06

    Accomplishing acid-stable water oxidation is a critical matter for achieving both long-lasting water-splitting devices and other fuel-forming electro- and photocatalytic processes. Because water oxidation releases protons into the local electrolytic environment, it becomes increasingly acidic during device operation, which leads to corrosion of the photoactive component and hence loss in device performance and lifetime. In this work, we show that thin films of manganese-modified titania, (Ti,Mn)O x , topped with an iridium catalyst, can be used in a coating stabilization scheme for acid-stable water oxidation. We achieved a device lifetime of more than 100 h in pH = 0 acid. We successfully grew (Ti,Mn)O x coatings with uniform elemental distributions over a wide range of manganese compositions using atomic layer deposition (ALD), and using X-ray photoelectron spectroscopy, we show that (Ti,Mn)O x films grown in this manner give rise to closer-to-valence-band Fermi levels, which can be further tuned with annealing. In contrast to the normally n-type or intrinsic TiO 2 coatings, annealed (Ti,Mn)O x films can make direct charge transfer to a Fe(CN) 6 3-/4- redox couple dissolved in aqueous electrolytes. Using the Fe(CN) 6 3-/4- redox, we further demonstrated anodic charge transfer through the (Ti,Mn)O x films to high work function metals, such as iridium and gold, which is not previously possible with ALD-grown TiO 2 . We correlated changes in the crystallinity (amorphous to rutile TiO 2 ) and oxidation state (2+ to 3+) of the annealed (Ti,Mn)O x films to their hole conductivity and electrochemical stability in acid. Finally, by combining (Ti,Mn)O x coatings with iridium, an acid-stable water-oxidation anode, using acid-sensitive conductive fluorine-doped tin oxides, was achieved.

  7. Pyroelectric response in crystalline hafnium zirconium oxide (Hf 1- x Zr x O 2 ) thin films

    DOE PAGES

    Smith, S. W.; Kitahara, A. R.; Rodriguez, M. A.; ...

    2017-02-13

    Pyroelectric coefficients were measured for 20 nm thick crystalline hafnium zirconium oxide (Hf 1-xZr xO 2) thin films across a composition range of 0 ≤ x ≤ 1. Pyroelectric currents were collected near room temperature under zero applied bias and a sinusoidal oscillating temperature profile to separate the influence of non-pyroelectric currents. The pyroelectric coefficient was observed to correlate with zirconium content, increased orthorhombic/tetragonal phase content, and maximum polarization response. The largest measured absolute value was 48 μCm -2K -1 for a composition with x = 0.64, while no pyroelectric response was measured for compositions which displayed no remanent polarizationmore » (x = 0, 0.91, 1).« less

  8. Electrochemical oxidation of 4-chlorophenol for wastewater treatment using highly active UV treated TiO2 nanotubes.

    PubMed

    Tian, Min; Thind, Sapanbir S; Dondapati, Jesse S; Li, Xinyong; Chen, Aicheng

    2018-06-07

    In the present work, we report on a facile UV treatment approach for enhancing the electrocatalytic activity of TiO 2 nanotubes. The TiO 2 nanotubes were prepared using an anodization oxidation method by applying a voltage of 40 V for 8 h in a DMSO + 2% HF solution, and further treated under UV light irradiation. Compared with Pt and untreated TiO 2 nanotubes, the UV treated electrode exhibited a superior electrocatalytic activity toward the oxidation of 4-chlorophenol (4-ClPh). The effects of current density and temperature on the electrochemical oxidation of the 4-ClPh were also systematically investigated. The high electrocatalytic activity of the UV treated TiO 2 nanotubes was further confirmed by the electrochemical oxidation of other persistent organic pollutants including phenol, 2-, 3-, 4-nitrophenol, and 4-aminophenol. The total organic carbon (TOC) analysis revealed that over 90% 4-ClPh was removed when the UV treated TiO 2 electrode was employed and the rate constant was 16 times faster than that of the untreated TiO 2 electrode; whereas only 60% 4-ClPh was eliminated at the Pt electrode under the same conditions. This dramatically improved electrocatalytic activity might be attributed to the enhanced donor density, conductivity, and high overpotential for oxygen evolution. Our results demonstrated that the application of the UV treatment to the TiO 2 nanotubes enhanced their electrochemical activity and energy consumption efficiency significantly, which is highly desirable for the abatement of persistent organic pollutants. Copyright © 2018 Elsevier Ltd. All rights reserved.

  9. High-Performance Asymmetric Supercapacitors of MnCo2O4 Nanofibers and N-Doped Reduced Graphene Oxide Aerogel.

    PubMed

    Pettong, Tanut; Iamprasertkun, Pawin; Krittayavathananon, Atiweena; Sukha, Phansiri; Sirisinudomkit, Pichamon; Seubsai, Anusorn; Chareonpanich, Metta; Kongkachuichay, Paisan; Limtrakul, Jumras; Sawangphruk, Montree

    2016-12-14

    The working potential of symmetric supercapacitors is not so wide because one type of material used for the supercapacitor electrodes prefers either positive or negative charge to both charges. To address this problem, a novel asymmetrical supercapacitor (ASC) of battery-type MnCo 2 O 4 nanofibers (NFs)//N-doped reduced graphene oxide aerogel (N-rGO AE ) was fabricated in this work. The MnCo 2 O 4 NFs at the positive electrode store the negative charges, i.e., solvated OH - , while the N-rGO AE at the negative electrode stores the positive charges, i.e., solvated K + . An as-fabricated aqueous-based MnCo 2 O 4 //N-rGO AE ASC device can provide a wide operating potential of 1.8 V and high energy density and power density at 54 W h kg -1 and 9851 W kg -1 , respectively, with 85.2% capacity retention over 3000 cycles. To understand the charge storage reaction mechanism of the MnCo 2 O 4 , the synchrotron-based X-ray absorption spectroscopy (XAS) technique was also used to determine the oxidation states of Co and Mn at the MnCo 2 O 4 electrode after being electrochemically tested. The oxidation number of Co is oxidized from +2.76 to +2.85 after charging and reduced back to +2.75 after discharging. On the other hand, the oxidation state of Mn is reduced from +3.62 to +3.44 after charging and oxidized to +3.58 after discharging. Understanding in the oxidation states of Co and Mn at the MnCo 2 O 4 electrode here leads to the awareness of the uncertain charge storage mechanism of the spinel-type oxide materials. High-performance ASC here in this work may be practically used in high-power applications.

  10. Pulsed laser deposited metal oxide thin films mediated controlled adsorption of proteins

    NASA Astrophysics Data System (ADS)

    Kim, Se Jin

    Several metal oxide thin films were grown on Si substrate by pulsed laser deposition for controlling adsorption of proteins. No intentional heating of substrate and introduction of oxygen gas during growth were employed. Additionally, fibrinogen, bovine serum albumin (BSA), and lysozyme were used as model protein in this study. The film properties such as cyratllinity, surface roughness, surface electrical charge and chemistry were investigated by many techniques in order to obtain the relationship with protein adsorption. Firstly, as grown Ta2O5 and ZnO thin film were used to study the effects of surface charge on the behaviors of BSA and lysozyme adsorption. The protein thickness results by ellipsometry showed that negatively charged Ta2O5 had a stronger affinity to positively charged lysozyme, while positively charged ZnO had a stronger affinity to negatively charged BSA. The results confirmed electrostatic interaction due to surface charge is one of main factors for determining adsorption of proteins. Furthermore, annealing studies were performed by heat treatment of as grown Ta2O5 and ZnO at 800°C in air ambience. Annealed Ta2O5 thin film had almost wetting property (from 10.02° to less than 1˜2°) and the change of cystallinity (from amorphous to cyrsalline) while annealed ZnO thin film had a reduced contact angle (from 75.65° to 39.41°) and remained to crystalline structure. The fibrinogen thickness on annealed Ta2O5 film was increased compared with as grown sample, while heat treated ZnO film showed much reduction of fibrinogen adsorption. Binary Ta-Zn oxide thin films (TZ) were grown by preparing PLD target composed of 50 wt% Ta2O5 and 50 wt% ZnO. This binary film had IEP pH 7.1 indicating nearly neutral charge in pH 7.4 PBS solution, and hydrophilic property. Ellipsometrical results showed that TZ film had the lowest fibrinogen, BSA and lysozyme thickness after 120 min adsorption compared with Ta2O5 and ZnO. Other samples, bilayer oxide films in

  11. Effect of composition on properties of In2O3-Ga2O3 thin films

    NASA Astrophysics Data System (ADS)

    Demin, I. E.; Kozlov, A. G.

    2017-06-01

    The In2O3-Ga2O3 mixed oxide polycrystalline thin films with various ratios of components were obtained by pulsed laser deposition. The effect of films composition on surface morphology, electrophysical and gas sensing properties and energies of adsorption and desorption of combustible gases was studied. The films with50%In2O3-50%Ga2O3 composition showed maximum gas response (˜25 times) combined with minimum optimal working temperature (˜530 °C) as compared with the other films. The optical transmittance of the films in visible range was investigated. For 50%In2O3-50%Ga2O3 films, the transmittance is higher in comparison with the other films. The explanation of the dependency of films behaviors on their composition was presented.The In2O3-Ga2O3 films were assumed to have perspectives as gas sensing material for semiconducting gas sensors.

  12. Thin film hydrous metal oxide catalysts

    DOEpatents

    Dosch, Robert G.; Stephens, Howard P.

    1995-01-01

    Thin film (<100 nm) hydrous metal oxide catalysts are prepared by 1) synthesis of a hydrous metal oxide, 2) deposition of the hydrous metal oxide upon an inert support surface, 3) ion exchange with catalytically active metals, and 4) activating the hydrous metal oxide catalysts.

  13. NiFe2O4 Spinel Protection Coating for High-Temperature Solid Oxide Fuel Cell Interconnect Application

    NASA Astrophysics Data System (ADS)

    Irankhah, Reza; Raissi, Babak; Maghsoudipour, Amir; Irankhah, Abdullah; Ghashghai, Sasan

    2016-04-01

    In the present study, Ni-Fe spinel powder was synthesized via a solid state reaction. In the next step, the electrophoretic deposition (EPD) method was used to apply the NiFe2O4 spinel, as an oxidation-resistant layer, on a commercially available stainless steel (SUS 430) in a potential range of 100 to 300 V. Microscopic studies of the deposited layers showed that crack-free NiFe2O4 films were obtained at 100 V. The coated and uncoated samples were then pre-sintered in air and 5% H2 bal Ar atmospheres at 900 °C for 3 h followed by cyclic oxidation at 800 °C for 500 h. The investigation of the oxidation resistance of the samples using Energy Dispersive Spectroscopy (EDS) revealed that the NiFe2O4 coating acted as an effective barrier against chromium migration into the coating. The oxidation resistance of 5% H2 bal Ar pre-sintered sample was enhanced with an oxidation rate constant ( K P) of 8.9 × 10-15 g2 cm-4 s-1.

  14. Detection of interstellar ethylene oxide (c-C2H4O).

    PubMed

    Dickens, J E; Irvine, W M; Ohishi, M; Ikeda, M; Ishikawa, S; Nummelin, A; Hjalmarson, A

    1997-11-10

    We report the identification of 10 transitions that support the detection of the small cyclic molecule ethylene oxide (c-C2H4O) in Sgr B2N. Although one of these transitions is severely blended, so that an accurate intensity and line width could not be determined, and two other lines are only marginally detected, we have done Gaussian fits to the remaining seven lines and have performed a rotation diagram analysis. Our results indicate a rotation temperature T(rot) = 18 K and a molecular column density N(c-C2H4O) = 3.3 x 10(14) cm-2, corresponding to a fractional abundance relative to molecular hydrogen of order 6 x 10(-11). This is a factor of more than 200 higher than the abundance for this molecule suggested by the "new standard" chemistry model of Lee, Bettens, & Herbst. This result suggests that grain chemistry might play an effective role in the production of c-C2H4O. No transitions of this molecule were detected in either Sgr B2M or Sgr B2NW.

  15. Investigation of physicochemical and tribological properties of transparent oxide semiconducting thin films based on Ti-V oxides

    NASA Astrophysics Data System (ADS)

    Mazur, M.; Sieradzka, K.; Kaczmarek, D.; Domaradzki, J.; Wojcieszak, D.; Domanowski, P.

    2013-08-01

    In this paper investigations of structural and optical properties of nanocrystalline Ti-V oxide thin films are described. The films were deposited onto Corning 7059 glass using a modified reactive magnetron sputtering method. Structural investigations of prepared Ti-V oxides with vanadium addition of 19 at. % revealed amorphous structure, while incorporation of 21 and 23 at. % of vanadium resulted in V2O5 formation with crystallites sizes of 12.7 and 32.4 nm, respectively. All prepared thin films belong to transparent oxide semiconductors due to their high transmission level of ca. 60-75 % in the visible light range, and resistivity in the range of 3.3·102-1.4·105 Ωcm. Additionally, wettability and hardness tests were performed in order to evaluate the usefulness of the films for functional coatings.

  16. TiO2-based (Fe3O4, SiO2, reduced graphene oxide) magnetically recoverable photocatalysts for imazalil degradation in a synthetic wastewater.

    PubMed

    Santiago, Dunia E; Pastrana-Martínez, Luisa M; Pulido-Melián, Elisenda; Araña, Javier; Faria, Joaquim L; Silva, Adrián M T; González-Díaz, Óscar; Doña-Rodríguez, José M

    2018-03-02

    Magnetite (Fe 3 O 4 ), a core-shell material (SiO 2 @Fe 3 O 4 ), and reduced graphene oxide-Fe 3 O 4 (referred as rGO-MN) were used as supports of a specific highly active TiO 2 photocatalyst. Thermal treatments at 200 or 450 °C, different atmospheres (air or N 2 ), and TiO 2 :support weight ratios (1.0, 1.5, or 2.0) were investigated. X-ray diffractograms revealed that magnetite is not oxidized to hematite when the core-shell SiO 2 @Fe 3 O 4 material-or a N 2 atmosphere (instead of air) in the thermal treatment-was employed to prepare the TiO 2 -based catalysts (the magnetic properties being preserved). The materials treated with N 2 were first tested for degradation of imazalil (a well-known fungicide) in deionized water. The best compromise between the photocatalytic activity, magnetic separation, and Fe leached (1.61 mg L -1 , i.e., below the threshold for water reuse in irrigation) was found for the magnetic catalyst prepared with SiO 2 @Fe 3 O 4 , an intermediate TiO 2 :support ratio (1.5), and treated at 200 °C under N 2 atmosphere (i.e., SiO 2 @Fe 3 O 4 -EST-1.5-200-N 2 ). This material was then tested for the treatment of imazalil in a synthetic wastewater, SW (with a chemical composition simulating an effluent resulting from fruit postharvest activity). This SW has a pH of 4.2 and the experiments were carried out at this natural pH 0 and at neutral conditions (keeping pH at 7 along the reaction). The magnetic catalyst was more active than bare TiO 2 for the treatment of imazalil in SW at natural pH. Since Fe leaching was observed (3.53 mg L -1 ), added H 2 O 2 enhanced both imazalil degradation and mineralization. Conveniently, these catalysts can be readily recovered by using a conventional magnetic field, as demonstrated over three consecutive recycling runs. Graphical abstract % Imazalil conversion using different magnetic catalysts and comparison with bare TiO 2 .

  17. Three new d10 transition metal selenites containing PO4 tetrahedron: Cd7(HPO4)2(PO4)2(SeO3)2, Cd6(PO4)1.34(SeO3)4.66 and Zn3(HPO4)(SeO3)2(H2O)

    NASA Astrophysics Data System (ADS)

    Ma, Yun-Xiang; Gong, Ya-Ping; Hu, Chun-li; Mao, Jiang-Gao; Kong, Fang

    2018-06-01

    Three new d10 transition metal selenites containing PO4 tetrahedron, namely, Cd7(HPO4)2(PO4)2(SeO3)2 (1), Cd6(PO4)1.34(SeO3)4.66 (2) and Zn3(HPO4)(SeO3)2(H2O) (3), have been synthesized by hydrothermal reaction. They feature three different structural types. Compound 1 exhibits a novel 3D network composed of 3D cadmium selenite open framework with phosphate groups filled in the 1D helical tunnels. The structure of compound 2 displays a new 3D framework consisted of 2D cadmium oxide layers bridged by SeO3 and PO4 groups. Compound 3 is isostructural with the reported solids of Co3(SeO3)3-x(PO3OH)x(H2O) when x is equal to 1.0. Its structure could be viewed as a 3D zinc oxide open skeleton with SeO3 and HPO4 polyhedra attached on the wall of the tunnels. They represent the only examples in metal selenite phosphates in addition to the above cobalt compounds. Optical diffuse reflectance spectra revealed that these solids are insulators, which are consistent with the results of band structure computations based on DFT algorithm.

  18. Demonstration of high-performance p-type tin oxide thin-film transistors using argon-plasma surface treatments

    NASA Astrophysics Data System (ADS)

    Bae, Sang-Dae; Kwon, Soo-Hun; Jeong, Hwan-Seok; Kwon, Hyuck-In

    2017-07-01

    In this work, we investigated the effects of low-temperature argon (Ar)-plasma surface treatments on the physical and chemical structures of p-type tin oxide thin-films and the electrical performance of p-type tin oxide thin-film transistors (TFTs). From the x-ray photoelectron spectroscopy measurement, we found that SnO was the dominant phase in the deposited tin oxide thin-film, and the Ar-plasma treatment partially transformed the tin oxide phase from SnO to SnO2 by oxidation. The resistivity of the tin oxide thin-film increased with the plasma-treatment time because of the reduced hole concentration. In addition, the root-mean-square roughness of the tin oxide thin-film decreased as the plasma-treatment time increased. The p-type oxide TFT with an Ar-plasma-treated tin oxide thin-film exhibited excellent electrical performance with a high current on-off ratio (5.2 × 106) and a low off-current (1.2 × 10-12 A), which demonstrates that the low-temperature Ar-plasma treatment is a simple and effective method for improving the electrical performance of p-type tin oxide TFTs.

  19. Study of electrochemical reduced graphene oxide and MnO2 heterostructure for supercapacitor application

    NASA Astrophysics Data System (ADS)

    Jana, S. K.; Rao, V. P.; Banerjee, S.

    2013-02-01

    In this paper we have shown enhanced supercapacitive property of electrochemically reduced graphene oxide (ERGO) and manganese dioxide (MnO2) based heterostructure over single MnO2 thin film grown by electrochemical deposition on indium tin oxide (ITO). ERGO improves the electrical conduction leading to decrease of the internal resistance of the heterostructure.

  20. Effect of thin oxide layers incorporated in spin valve structures

    NASA Astrophysics Data System (ADS)

    Gillies, M. F.; Kuiper, A. E. T.; Leibbrandt, G. W. R.

    2001-06-01

    The enhancement of the magnetoresistance effect, induced by incorporating nano-oxide layers (NOLs) in a bottom-type spin valve, was studied for various preparation conditions. The effect of a NOL in the Co90Fe10 pinned layer was found to depend critically on the oxygen pressure applied to form the thin oxide film. Pressures over 10-3 Torr O2 yield oxides thicker than about 0.7 nm, which apparently deteriorate the biasing field which exists over the oxide. The magnetoresistance values can further be raised by forming a specular reflecting oxide on top of the sense layer. Promising results were obtained with an Al2O3 capping layer formed in a solid-state oxidation reaction that occurs spontaneously when a thin Al layer is deposited on the oxidized surface of the Co90Fe10 sense layer.

  1. Temperature dependence of gas sensing behaviour of TiO2 doped PANI composite thin films

    NASA Astrophysics Data System (ADS)

    Srivastava, Subodh; Sharma, S. S.; Sharma, Preetam; Sharma, Vinay; Rajura, Rajveer Singh; Singh, M.; Vijay, Y. K.

    2014-04-01

    In the present work we have reported the effect of temperature on the gas sensing properties of TiO2 doped PANI composite thin film based chemiresistor type gas sensors for hydrogen gas sensing application. PANI and TiO2 doped PANI composite were synthesized by in situ chemical oxidative polymerization of aniline at low temperature. The electrical properties of these composite thin films were characterized by I-V measurements as function of temperature. The I-V measurement revealed that conductivity of composite thin films increased as the temperature increased. The changes in resistance of the composite thin film sensor were utilized for detection of hydrogen gas. It was observed that at room temperature TiO2 doped PANI composite sensor shows higher response value and showed unstable behavior as the temperature increased. The surface morphology of these composite thin films has also been characterized by scanning electron microscopy (SEM) measurement.

  2. Improved Optical Transmittance and Crystal Characteristics of ZnS:TbOF Thin Film on Bi4Ti3O12/Indium Tin Oxide/Glass Substrate by Using a SiO2 Buffer Layer

    NASA Astrophysics Data System (ADS)

    Chia, Wei‑Kuo; Yokoyama, Meiso; Yang, Cheng‑Fu; Chiang, Wang‑Ta; Chen, Ying‑Chung

    2006-07-01

    Bi4Ti3O12 thin films are deposited on indium tin oxide (ITO)/glass substrates using RF magnetron sputtering technology and are annealed at 675 °C in a rapid thermal annealing furnace in an oxygen atmosphere. The resulting films have high optical transmittances and good crystalline characteristics. ZnS:TbOF films are then deposited on the Bi4Ti3O12 films, causing the originally highly transparent specimens to blacken and to resemble a glass surface coated with carbon powder. The optical transmittance of the specimen is less than 15% under the visible wavelength range, and neither a crystalline phase nor a distinct ZnS grain structure is evident in X-ray diffractometer (XRD) and scanning electronic microscope (SEM). Secondary ion mass spectrometer (SIMS) analysis reveals the occurrence of interdiffusion between the ZnS and Bi4Ti3O12 layers. This suggests that one or more unknown chemical reactions take place among the elements Bi, S, and O at the interface during the deposition of ZnS:TbOF film on a Bi4Ti3O12/ITO/glass substrate. These reactions cause the visible transmittance of the specimens to deteriorate dramatically. To prevent interdiffusion, a silicon dioxide (SiO2) buffer layer 100 nm thick was grown on the Bi4Ti3O12/ITO/glass substrate using plasma-enhanced chemical vapor deposition (PECVD), then the ZnS:TbOF film was grown on the SiO2 buffer layer. The transmittance of the resulting specimen is enhanced approximately 8-fold in the visible region. XRD patterns reveal the ZnS(111)-oriented phase is dominant. Furthermore, dense, crack-free ZnS:TbOF grains are observed by SEM. The results imply that the SiO2 buffer layer sandwiched between the ZnS:TbOF and Bi4Ti3O2 layers effectively separates the two layers. Therefore, interdiffusion and chemical reactions are prevented at the interface of the two layers, and the crystalline characteristics of the ZnS:TbOF layer and the optical transmittance of the specimen are improved as a result. Finally, the dielectric

  3. Surface Passivation of Silicon Using HfO2 Thin Films Deposited by Remote Plasma Atomic Layer Deposition System.

    PubMed

    Zhang, Xiao-Ying; Hsu, Chia-Hsun; Lien, Shui-Yang; Chen, Song-Yan; Huang, Wei; Yang, Chih-Hsiang; Kung, Chung-Yuan; Zhu, Wen-Zhang; Xiong, Fei-Bing; Meng, Xian-Guo

    2017-12-01

    Hafnium oxide (HfO 2 ) thin films have attracted much attention owing to their usefulness in equivalent oxide thickness scaling in microelectronics, which arises from their high dielectric constant and thermodynamic stability with silicon. However, the surface passivation properties of such films, particularly on crystalline silicon (c-Si), have rarely been reported upon. In this study, the HfO 2 thin films were deposited on c-Si substrates with and without oxygen plasma pretreatments, using a remote plasma atomic layer deposition system. Post-annealing was performed using a rapid thermal processing system at different temperatures in N 2 ambient for 10 min. The effects of oxygen plasma pretreatment and post-annealing on the properties of the HfO 2 thin films were investigated. They indicate that the in situ remote plasma pretreatment of Si substrate can result in the formation of better SiO 2 , resulting in a better chemical passivation. The deposited HfO 2 thin films with oxygen plasma pretreatment and post-annealing at 500 °C for 10 min were effective in improving the lifetime of c-Si (original lifetime of 1 μs) to up to 67 μs.

  4. Synthesis from separate oxide targets of high quality La2-xSrxCuO4 thin films and dependence with doping of their superconducting transition width

    NASA Astrophysics Data System (ADS)

    Cotón, N.; Mercey, B.; Mosqueira, J.; Ramallo, M. V.; Vidal, F.

    2013-07-01

    A series of superconducting La2-xSrxCuO4 thin films, with 0.09 ≲ x ≲ 0.22, is grown over (100)SrTiO3 substrates by means of a novel pulsed laser deposition method devised to increase the homogeneity and control of doping. We employ two separate parent oxide targets that receive ablation shots at arbitrary computer-controlled relative rates, instead of the conventional procedure that uses a single target whose doping determines the one of the film. We characterize the films both through conventional techniques (XRD, SEM, AFM and EDX) and by measuring their superconducting transition with a high-sensitivity SQUID magnetometer. The latter allows one to determine not only their average critical temperatures {\\bar {T}}_{{c}}(x) but also their dispersions due to inhomogeneities, ΔTc(x). For {\\bar {T}}_{{c}}(x) we obtain the conventional parabolic law centered at x = 0.16, plus a Gaussian depression near x = 1/8 with a {\\bar {T}}_{{c}}-height of about 5 K and x-width about 0.03. For ΔTc(x) we obtain, for all the dopings, values among the lowest reported up to now for La2-xSrxCuO4. The ΔTc(x) dependence can be explained in terms of the unavoidable randomness of the positioning of the Sr ions (the so-called intrinsic chemical inhomogeneity) and a separate residual Tc-inhomogeneity contribution of the order of 0.5 K, this last associated with the samples’ structural inhomogeneities and films’ substrate.

  5. Highly-efficient forward osmosis membrane tailored by magnetically responsive graphene oxide/Fe3O4 nanohybrid

    NASA Astrophysics Data System (ADS)

    Rastgar, Masoud; Shakeri, Alireza; Bozorg, Ali; Salehi, Hasan; Saadattalab, Vahid

    2018-05-01

    Emerging forward osmosis (FO) process as a potentially more energy efficient method has recently gained remarkable attention. Herein, considering the unique features of graphene oxide (GO), a new facile method has been proposed to magnetically modify GO within the polyamide active layer to obtain highly efficient osmotically driven membranes. While exposed to magnetic field, thin film nanocomposite membranes modified by GO/Fe3O4 nanohybrids (TFN-MMGO/Fe3O4) were synthesized by in-situ interfacial polymerization of the prepared monomer solution and organic trimesoyl chloride. Water permeability, salt rejection, and fouling tendency of the modified membranes were then evaluated and compared with both pristine thin film composite (TFC) membrane and the ones modified by GO/Fe3O4 nanohybrides in the absence of magnetic field (TFN-GO/Fe3O4). According to the experimental results, when compared to the TFC and TFN-GO/Fe3O4 membranes, respectively, 117.4% and 63.2% water flux enhancements were achieved in TFN-MMGO/Fe3O4 membrane with optimal GO/Fe3O4 nanohybrid concentration of 100 ppm. In spite of such improvements in water flux, little compromise in reverse salt leakages were observed in the TFN-MMGO/Fe3O4 membranes compared to the TFC one. As well, the TFN-MMGO/Fe3O4 and TFN-GO/Fe3O4 membranes revealed higher fouling resistances than the TFC membrane due to their distinguished manipulated surface characteristics.

  6. A Fe3O4/FeAl2O4 composite coating via plasma electrolytic oxidation on Q235 carbon steel for Fenton-like degradation of phenol.

    PubMed

    Wang, Jiankang; Yao, Zhongping; Yang, Min; Wang, Yajing; Xia, Qixing; Jiang, Zhaohua

    2016-08-01

    The Fe3O4/FeAl2O4 composite coatings were successfully fabricated on Q235 carbon steel by plasma electrolytic oxidation technique and used to degrade phenol by Fenton-like system. XRD, SEM, and XPS indicated that Fe3O4 and FeAl2O4 composite coating had a hierarchical porous structure. The effects of various parameters such as pH, phenol concentration, and H2O2 dosage on catalytic activity were investigated. The results indicated that with increasing of pH and phenol content, the phenol degradation efficiency was reduced significantly. However, the degradation rate was improved with the addition of H2O2, but dropped with further increasing of H2O2. Moreover, 100 % removal efficiency with 35 mg/L phenol was obtained within 60 min at 303 K and pH 4.0 with 6.0 mmol/L H2O2 on 6-cm(2) iron oxide coating. The degradation process consisted of induction period and rapid degradation period; both of them followed pseudo-first-order reaction. Hydroxyl radicals were the mainly oxidizing species during phenol degradation by using n-butanol as hydroxyl radical scavenger. Based on Fe leaching and the reaction kinetics, a possible phenol degradation mechanism was proposed. The catalyst exhibited excellent stability.

  7. Electro deposition of cuprous oxide for thin film solar cell applications

    NASA Astrophysics Data System (ADS)

    Shahrestani, Seyed Mohammad

    electro-deposition of Cu2O n-type were identified consistently for the first time. The electro-deposition electrolyte is based 0.01M acetate copper and 0.1 M sodium acetate: it has a pH between 6.3 and 4, a potential of from 0 to -0.25 V vs. Ag / AgCl and a temperature of 60oC. The optimum annealing temperature of the n-type Cu2O layers is between 120-150oC for the annealing time of 30 to 120 minutes. Resistivity of the n-type films varies between 5 x 103 and 5 x 104 at pH 4 to pH 6.4. We have shown for the first time that bubbling nitrogen gas in the electroplating cell improves significantly the spectral response of the electro-deposited n-type thin film. A two steps electro-deposition process was implemented to make the p-n homojunction cuprous oxide. Indium tin oxide (ITO) was used as a transparent conductive oxide substrate. A p-Cu2O was electrodeposited on ITO. After heat treatment a thin film layer of n-Cu 2O was electrodeposited on top of previous layer. The performance of a p-n homojunction photovoltaic solar cell of Cu2O was determined. The short-circuit current and the open circuit voltage were respectively determined to be as 0.35 volts and 235 muA/cm2. The fill factor (FF) and conversion efficiency of light into electricity were respectively measured to be 0.305 and 0.082%.

  8. Graphene oxide (rGO)-metal oxide (TiO2/Fe3O4) based nanocomposites for the removal of methylene blue

    NASA Astrophysics Data System (ADS)

    Banerjee, Soma; Benjwal, Poonam; Singh, Milan; Kar, Kamal K.

    2018-05-01

    Herein, ternary nanocomposites based on titanium dioxide, ferric oxide and reduced graphene oxide (GO) have been developed for photocatalytic degradation of methylene blue. The nanocomposites are prepared by simple sol-gel and wet assembly methods with varying weight ratio of each components to obtain efficient photocatalytic degradation. Due to the synergistic effect among the three components, a swift removal of methylene blue becomes possible under visible and UV light. The rGO-Fe3O4-TiO2 nanocomposite having composition 1:1:2 has achieved maximum degradation of methylene blue from the aqueous solution. About 99% of the dye has been removed within 6 min under UV irradiation, while in presence of visible light, 94% has been degraded from the wastewater. The enhancement of photocatalytic activity in this ternary system is attributed to the efficient separation of charge carriers from TiO2 to rGO under the exposure of light and the initiation of photo-Fenton reaction due to the incorporated Fe3O4 nanoparticles in presence of H2O2, which provides highly reactive hydroxyl ions that mineralize the pollutants. All these results indicate that these ternary nanocomposites possess great potential for both UV and visible light driven methylene blue destruction from the wastewater.

  9. Surface electronic properties of polycrystalline bulk and thin film In2O3(ZnO)k compounds

    NASA Astrophysics Data System (ADS)

    Hopper, E. Mitchell; Zhu, Qimin; Gassmann, Jürgen; Klein, Andreas; Mason, Thomas O.

    2013-01-01

    The surface electronic potentials of In2O3(ZnO)k compounds were measured by X-ray and ultraviolet photoelectron spectroscopy. Both thin film (k = 2) and bulk specimens (k = 3, 5, 7, 9) were studied. All bulk specimens exhibited In enrichment at the surface. All samples showed an increase of In core level binding energies compared to pure and Sn-doped In2O3. The work functions and Fermi levels spanned a range similar to those of the basis oxides In2O3 and ZnO, and the ionization potential was similar to that of both In2O3 and ZnO processed under similar conditions (7.7 eV). This ionization potential was independent of both composition and post-deposition oxidation and reduction treatments. Kelvin probe measurements of cleaned and UV-ozone treated specimens under ambient conditions were in agreement with the photoelectron spectroscopy measurements.

  10. Realization of write-once-read-many-times memory device with O{sub 2} plasma-treated indium gallium zinc oxide thin film

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Liu, P., E-mail: liup0013@ntu.edu.sg; Chen, T. P., E-mail: echentp@ntu.edu.sg; Li, X. D.

    2014-01-20

    A write-once-read-many-times (WORM) memory devices based on O{sub 2} plasma-treated indium gallium zinc oxide (IGZO) thin films has been demonstrated. The device has a simple Al/IGZO/Al structure. The device has a normally OFF state with a very high resistance (e.g., the resistance at 2 V is ∼10{sup 9} Ω for a device with the radius of 50 μm) as a result of the O{sub 2} plasma treatment on the IGZO thin films. The device could be switched to an ON state with a low resistance (e.g., the resistance at 2 V is ∼10{sup 3} Ω for the radius of 50 μm) by applying amore » voltage pulse (e.g., 10 V/1 μs). The WORM device has good data-retention and reading-endurance capabilities.« less

  11. Multi-layer thin-film electrolytes for metal supported solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Haydn, Markus; Ortner, Kai; Franco, Thomas; Uhlenbruck, Sven; Menzler, Norbert H.; Stöver, Detlev; Bräuer, Günter; Venskutonis, Andreas; Sigl, Lorenz S.; Buchkremer, Hans-Peter; Vaßen, Robert

    2014-06-01

    A key to the development of metal-supported solid oxide fuel cells (MSCs) is the manufacturing of gas-tight thin-film electrolytes, which separate the cathode from the anode. This paper focuses the electrolyte manufacturing on the basis of 8YSZ (8 mol.-% Y2O3 stabilized ZrO2). The electrolyte layers are applied by a physical vapor deposition (PVD) gas flow sputtering (GFS) process. The gas-tightness of the electrolyte is significantly improved when sequential oxidic and metallic thin-film multi-layers are deposited, which interrupt the columnar grain structure of single-layer electrolytes. Such electrolytes with two or eight oxide/metal layers and a total thickness of about 4 μm obtain leakage rates of less than 3 × 10-4 hPa dm3 s-1 cm-2 (Δp: 100 hPa) at room temperature and therefore fulfill the gas tightness requirements. They are also highly tolerant with respect to surface flaws and particulate impurities which can be present on the graded anode underground. MSC cell tests with double-layer and multilayer electrolytes feature high power densities more than 1.4 W cm-2 at 850 °C and underline the high potential of MSC cells.

  12. Combustion synthesized indium-tin-oxide (ITO) thin film for source/drain electrodes in all solution-processed oxide thin-film transistors

    NASA Astrophysics Data System (ADS)

    Tue, Phan Trong; Inoue, Satoshi; Takamura, Yuzuru; Shimoda, Tatsuya

    2016-06-01

    We report combustion solution synthesized (SCS) indium-tin-oxide (ITO) thin film, which is a well-known transparent conductive oxide, for source/drain (S/D) electrodes in solution-processed amorphous zirconium-indium-zinc-oxide TFT. A redox-based combustion synthetic approach is applied to ITO thin film using acetylacetone as a fuel and metal nitrate as oxidizer. The structural and electrical properties of SCS-ITO precursor solution and thin films were systematically investigated with changes in tin concentration, indium metal precursors, and annealing conditions such as temperature, time, and ambient. It was found that at optimal conditions the SCS-ITO thin film exhibited high crystalline quality, atomically smooth surface (RMS ~ 4.1 Å), and low electrical resistivity (4.2 × 10-4 Ω cm). The TFT using SCS-ITO film as the S/D electrodes showed excellent electrical properties with negligible hysteresis. The obtained "on/off" current ratio, subthreshold swing factor, subthreshold voltage, and field-effect mobility were 5 × 107, 0.43 V/decade, 0.7 V, and 2.1 cm2/V s, respectively. The performance and stability of the SCS-ITO TFT are comparable to those of the sputtered-ITO TFT, emphasizing that the SCS-ITO film is a promising candidate for totally solution-processed oxide TFTs.

  13. Nanocolumnar Crystalline Vanadium Oxide-Molybdenum Oxide Antireflective Smart Thin Films with Superior Nanomechanical Properties.

    PubMed

    Dey, Arjun; Nayak, Manish Kumar; Esther, A Carmel Mary; Pradeepkumar, Maurya Sandeep; Porwal, Deeksha; Gupta, A K; Bera, Parthasarathi; Barshilia, Harish C; Mukhopadhyay, Anoop Kumar; Pandey, Ajoy Kumar; Khan, Kallol; Bhattacharya, Manjima; Kumar, D Raghavendra; Sridhara, N; Sharma, Anand Kumar

    2016-11-17

    Vanadium oxide-molybdenum oxide (VO-MO) thin (21-475 nm) films were grown on quartz and silicon substrates by pulsed RF magnetron sputtering technique by altering the RF power from 100 to 600 W. Crystalline VO-MO thin films showed the mixed phases of vanadium oxides e.g., V 2 O 5 , V 2 O 3 and VO 2 along with MoO 3 . Reversible or smart transition was found to occur just above the room temperature i.e., at ~45-50 °C. The VO-MO films deposited on quartz showed a gradual decrease in transmittance with increase in film thickness. But, the VO-MO films on silicon exhibited reflectance that was significantly lower than that of the substrate. Further, the effect of low temperature (i.e., 100 °C) vacuum (10 -5 mbar) annealing on optical properties e.g., solar absorptance, transmittance and reflectance as well as the optical constants e.g., optical band gap, refractive index and extinction coefficient were studied. Sheet resistance, oxidation state and nanomechanical properties e.g., nanohardness and elastic modulus of the VO-MO thin films were also investigated in as-deposited condition as well as after the vacuum annealing treatment. Finally, the combination of the nanoindentation technique and the finite element modeling (FEM) was employed to investigate yield stress and von Mises stress distribution of the VO-MO thin films.

  14. Nanocolumnar Crystalline Vanadium Oxide-Molybdenum Oxide Antireflective Smart Thin Films with Superior Nanomechanical Properties

    NASA Astrophysics Data System (ADS)

    Dey, Arjun; Nayak, Manish Kumar; Esther, A. Carmel Mary; Pradeepkumar, Maurya Sandeep; Porwal, Deeksha; Gupta, A. K.; Bera, Parthasarathi; Barshilia, Harish C.; Mukhopadhyay, Anoop Kumar; Pandey, Ajoy Kumar; Khan, Kallol; Bhattacharya, Manjima; Kumar, D. Raghavendra; Sridhara, N.; Sharma, Anand Kumar

    2016-11-01

    Vanadium oxide-molybdenum oxide (VO-MO) thin (21-475 nm) films were grown on quartz and silicon substrates by pulsed RF magnetron sputtering technique by altering the RF power from 100 to 600 W. Crystalline VO-MO thin films showed the mixed phases of vanadium oxides e.g., V2O5, V2O3 and VO2 along with MoO3. Reversible or smart transition was found to occur just above the room temperature i.e., at ~45-50 °C. The VO-MO films deposited on quartz showed a gradual decrease in transmittance with increase in film thickness. But, the VO-MO films on silicon exhibited reflectance that was significantly lower than that of the substrate. Further, the effect of low temperature (i.e., 100 °C) vacuum (10-5 mbar) annealing on optical properties e.g., solar absorptance, transmittance and reflectance as well as the optical constants e.g., optical band gap, refractive index and extinction coefficient were studied. Sheet resistance, oxidation state and nanomechanical properties e.g., nanohardness and elastic modulus of the VO-MO thin films were also investigated in as-deposited condition as well as after the vacuum annealing treatment. Finally, the combination of the nanoindentation technique and the finite element modeling (FEM) was employed to investigate yield stress and von Mises stress distribution of the VO-MO thin films.

  15. Nanocolumnar Crystalline Vanadium Oxide-Molybdenum Oxide Antireflective Smart Thin Films with Superior Nanomechanical Properties

    PubMed Central

    Dey, Arjun; Nayak, Manish Kumar; Esther, A. Carmel Mary; Pradeepkumar, Maurya Sandeep; Porwal, Deeksha; Gupta, A. K.; Bera, Parthasarathi; Barshilia, Harish C.; Mukhopadhyay, Anoop Kumar; Pandey, Ajoy Kumar; Khan, Kallol; Bhattacharya, Manjima; Kumar, D. Raghavendra; Sridhara, N.; Sharma, Anand Kumar

    2016-01-01

    Vanadium oxide-molybdenum oxide (VO-MO) thin (21–475 nm) films were grown on quartz and silicon substrates by pulsed RF magnetron sputtering technique by altering the RF power from 100 to 600 W. Crystalline VO-MO thin films showed the mixed phases of vanadium oxides e.g., V2O5, V2O3 and VO2 along with MoO3. Reversible or smart transition was found to occur just above the room temperature i.e., at ~45–50 °C. The VO-MO films deposited on quartz showed a gradual decrease in transmittance with increase in film thickness. But, the VO-MO films on silicon exhibited reflectance that was significantly lower than that of the substrate. Further, the effect of low temperature (i.e., 100 °C) vacuum (10−5 mbar) annealing on optical properties e.g., solar absorptance, transmittance and reflectance as well as the optical constants e.g., optical band gap, refractive index and extinction coefficient were studied. Sheet resistance, oxidation state and nanomechanical properties e.g., nanohardness and elastic modulus of the VO-MO thin films were also investigated in as-deposited condition as well as after the vacuum annealing treatment. Finally, the combination of the nanoindentation technique and the finite element modeling (FEM) was employed to investigate yield stress and von Mises stress distribution of the VO-MO thin films. PMID:27853234

  16. Fabrication of graphene oxide decorated with Fe3O4@SiO2 for immobilization of cellulase

    NASA Astrophysics Data System (ADS)

    Li, Yue; Wang, Xiang-Yu; Jiang, Xiao-Ping; Ye, Jing-Jing; Zhang, Ye-Wang; Zhang, Xiao-Yun

    2015-01-01

    Fe3O4@SiO2-graphene oxide (GO) composites were successfully fabricated by chemical binding of functional Fe3O4@SiO2 and GO and applied to immobilization of cellulase via covalent attachment. The prepared composites were further characterized by transmission electron microscopy and Fourier transform infrared spectroscopy. Fe3O4 nanoparticles (NPs) were monodisperse spheres with a mean diameter of 17 ± 0.2 nm. The thickness of SiO2 layer was calculated as being 6.5 ± 0.2 nm. The size of Fe3O4@SiO2 NPs was 24 ± 0.3 nm, similar to that of Fe3O4@SiO2-NH2. Fe3O4@SiO2-GO composites were synthesized by linking of Fe3O4@SiO2-NH2 NPs to GO with the catalysis of EDC and NHS. The prepared composites were used for immobilization of cellulase. A high immobilization yield and efficiency of above 90 % were obtained after the optimization. The half-life of immobilized cellulase (722 min) was 3.34-fold higher than that of free enzyme (216 min) at 50 °C. Compared with the free cellulase, the optimal temperature of the immobilized enzyme was not changed; but the optimal pH was shifted from 5.0 to 4.0, and the thermal stability was enhanced. The immobilized cellulase could be easily separated and reused under magnetic field. These results strongly indicate that the cellulase immobilized onto the Fe3O4@SiO2-GO composite has potential applications in the production of bioethanol.

  17. Development of an E-H2O2/TiO2 photoelectrocatalytic oxidation system for water and wastewater treatment.

    PubMed

    Li, X Z; Liu, H S

    2005-06-15

    In this study, an innovative E-H2O2/TiO2 (E-H2O2 = electrogenerated hydrogen peroxide) photoelectrocatalytic (PEC) oxidation system was successfully developed for water and wastewater treatment. A TiO2/Ti mesh electrode was applied in this photoreactor as the anode to conduct PEC oxidation, and a reticulated vitreous carbon (RVC) electrode was used as the cathode to electrogenerate hydrogen peroxide simultaneously. The TiO2/Ti mesh electrode was prepared with a modified anodic oxidation process in a quadrielectrolyte (H2SO4-H3PO4-H2O2-HF) solution. The crystal structure, surface morphology, and film thickness of the TiO2/Ti mesh electrode were characterized by X-ray diffraction and scanning electron microscopy. The analytical results showed that a honeycomb-type anatase film with a thickness of 5 microm was formed. Photocatalytic oxidation (PC) and PEC oxidation of 2,4,6-trichlorophenol (TCP) in an aqueous solution were performed under various experimental conditions. Experimental results showed that the TiO2/Ti electrode, anodized in the H2SO4-H3PO4-H2O2-HF solution, had higher photocatalytic activity than the TiO2/Ti electrode anodized in the H2SO4 solution. It was found that the maximum applied potential would be around 2.5 V, corresponding to an optimum applied current density of 50 microA cm(-2) under UV-A illumination. The experiments confirmed that the E-H2O2 on the RVC electrode can significantly enhance the PEC oxidation of TCP in aqueous solution. The rate of TCP degradation in such an E-H2O2-assisted TiO2 PEC reaction was 5.0 times that of the TiO2 PC reaction and 2.3 times that of the TiO2 PEC reaction. The variation of pH during the E-H2O2-assisted TiO2 PEC reaction, affected by individual reactions, was also investigated. It was found that pH was well maintained during the TCP degradation in such an E-H2O2/TiO2 reaction system. This is beneficial to TCP degradation in an aqueous solution.

  18. Fe2O3/Reduced Graphene Oxide/Fe3O4 Composite in Situ Grown on Fe Foil for High-Performance Supercapacitors.

    PubMed

    Zhao, Chongjun; Shao, Xiaoxiao; Zhang, Yuxiao; Qian, Xiuzhen

    2016-11-09

    A Fe 2 O 3 /reduced graphene oxide (RGO)/Fe 3 O 4 nanocomposite in situ grown on Fe foil was synthesized via a simple one-step hydrothermal growth process, where the iron foil served as support, reductant of graphene oxide, Fe source of Fe 3 O 4 , and also the current collector of the electrode. When it directly acted as the electrode of a supercapacitor, as-synthesized Fe 2 O 3 /RGO/Fe 3 O 4 @Fe exhibited excellent electrochemical performance with a high capability of 337.5 mF/cm 2 at 20 mA/cm 2 and a superior cyclability with 2.3% capacity loss from the 600th to the 2000th cycle.

  19. Microstructure and dielectric properties of pyrochlore Bi2Ti2O7 thin films

    NASA Astrophysics Data System (ADS)

    Cagnon, Joël; Boesch, Damien S.; Finstrom, Nicholas H.; Nergiz, Saide Z.; Keane, Sean P.; Stemmer, Susanne

    2007-08-01

    Bi2Ti2O7 thin films were grown by radio-frequency magnetron sputtering on bare and Pt-coated sapphire substrates at low substrate temperatures (˜200 °C). Postdeposition anneals were carried out at different temperatures to crystallize the films. Nearly phase-pure Bi2Ti2O7 thin films with the cubic pyrochlore structure were obtained at annealing temperatures up to 800 °C. Impurity phases, in particular Bi4Ti3O12, formed at higher temperatures. At 1 MHz, the dielectric constants were about 140-150 with a very small tunability and the dielectric loss was about 4×10-3. The dielectric loss increased with frequency. The dielectric properties of Bi2Ti2O7 films are compared to those of pyrochlore bismuth zinc niobate films.

  20. Thermoelectric Properties and Microstructure of Ca3 Co 4 O 9 thin films on SrTiO3 and Al2 O 3 Substrates

    NASA Astrophysics Data System (ADS)

    Paulauskas, T.; Qiao, Q.; Gulec, A.; Klie, R. F.; Ozdemir, M.; Boyraz, C.; Mazumdar, D.; Gupta, A.

    2011-03-01

    Ca 3 Co 4 O9 (CCO), a misfit layered structure exhibiting large Seebeck coefficient at temperatures up to 1000K has attracted increasing attention as a novel high-temperature thermoelectric material. In this work, we investigate CCO thin films grown on SrTi O3 (001) and Al 2 O3 (0001) using pulsed laser deposition. Quality of the thin films was examined using high-resolution transmission electron microscopy and thermoelectric transport measurements. HRTEM images show incommensurate stacks of Cd I2 -type Co O2 layer alternating with rock-salt-type Ca 2 Co O3 layer along the c-axis. Perovskite buffer layer about 10nm thick was found present between CCO and SrTi O3 accompanied by higher density of stacking faults. The CCO grown on Al 2 O3 exhibited numerous misoriented grains and presence of Ca x Co O2 phase. Seebeck coefficient measurements yield an improvement for both samples compared to the bulk value. We suggest that thermoelectric properties of CCO increase due to additional phonon scattering at the stacking faults as well as at the film surfaces/interfaces. This research was supported by the US Army Research Office (W911NF-10-1-0147) and the Sivananthan Undergraduate Research Fellowship.

  1. Influences of the residual argon gas and thermal annealing on Ta2O5 and SiO2 thin film filters

    NASA Astrophysics Data System (ADS)

    Liu, Wen-Jen; Chen, Chih-Min; Lai, Yin-Chieh

    2005-04-01

    Ion beam assisted deposition (IBAD) technique had widely used for improving stacking density and atomic mobility of thin films in many applications, especially adopted in optical film industries. Tantalum pentaoxide (Ta2O5) and silicon oxides (SiO2) optical thin films were deposited on the quartz glass substrate by using argon ion beam assisted deposition, and the influences of the residual argon gas and thermal annealing processes on the optical property, stress, compositional and microstructure evolution of the thin films were investigated in this study. Ta2O5 thin films were analyzed by XPS indicated that the ratio value of oxygen to tantalum was insufficient, at the same time, the residual argon gas in the thin films might result in film and device instabilities. Adopting oxygen-thermal annealing treatment at the temperature of 425°C, the thin films not only decreased the residual argon gas and the surface roughness, but also provided the sufficient stoichiometric ratio. Simultaneously, microstructure examination indicated few nano-crystallized structures and voids existed in Ta2O5 thin films, and possessed reasonable refractive index and lower extinction coefficient. By the way, we also suggested the IBAD system using the film compositional gas ion beam to replace the argon ion beam for assisting deposited optical films. The designed (HL)6H6LH(LH)6 multi-layers indicated higher insertion loss than the designed (HL)68H(LH)6 multi-layers. Therefore, using the high refractive index as spacer material represented lower insertion loss.

  2. DFT studies on H 2O adsorption and its effect on CO oxidation over spinel Co 3O 4 (110) surface

    NASA Astrophysics Data System (ADS)

    Xu, Xiang Lan; Li, Jun Qian

    2011-12-01

    Adsorption of H2O and its effect on CO oxidation over spinel Co3O4 (110) surface were studied by density functional theory calculations. H2O is adsorbed favorably at the octahedral cobalt (Cooct) site through O atom on the surface. Hydrogen bonding interaction between 1s orbitals of H atoms in H2O and the 2p orbitals of surface active oxygen sites plays a key role for H2O adsorption. The inhibition effect of H2O adsorption on the CO oxidation over the surfaces is attributed to the competition between H2O and CO molecules for the surface twofold coordinated oxygen site.

  3. Growth and characterization of β-Ga2O3 thin films by molecular beam epitaxy for deep-UV photodetectors

    NASA Astrophysics Data System (ADS)

    Ghose, Susmita; Rahman, Shafiqur; Hong, Liang; Rojas-Ramirez, Juan Salvador; Jin, Hanbyul; Park, Kibog; Klie, Robert; Droopad, Ravi

    2017-09-01

    The growth of high quality epitaxial beta-gallium oxide (β-Ga2O3) using a compound source by molecular beam epitaxy has been demonstrated on c-plane sapphire (Al2O3) substrates. The compound source provides oxidized gallium molecules in addition to oxygen when heated from an iridium crucible in a high temperature effusion cell enabling a lower heat of formation for the growth of Ga2O3, resulting in a more efficient growth process. This source also enabled the growth of crystalline β-Ga2O3 without the need for additional oxygen. The influence of the substrate temperatures on the crystal structure and quality, chemical bonding, surface morphology, and optical properties has been systematically evaluated by x-ray diffraction, scanning transmission electron microscopy, x-ray photoelectron spectroscopy, atomic force microscopy, spectroscopic ellipsometry, and UV-vis spectroscopy. Under optimized growth conditions, all films exhibited pure (" separators="|2 ¯01 ) oriented β-Ga2O3 thin films with six-fold rotational symmetry when grown on a sapphire substrate. The thin films demonstrated significant absorption in the deep-ultraviolet (UV) region with an optical bandgap around 5.0 eV and a refractive index of 1.9. A deep-UV photodetector fabricated on the high quality β-Ga2O3 thin film exhibits high resistance and small dark current (4.25 nA) with expected photoresponse for 254 nm UV light irradiation suggesting that the material grown using the compound source is a potential candidate for deep-ultraviolet photodetectors.

  4. Negative charge trapping effects in Al{sub 2}O{sub 3} films grown by atomic layer deposition onto thermally oxidized 4H-SiC

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Schilirò, Emanuela, E-mail: emanuela.schiliro@imm.cnr.it; Dipartimento di Scienze Chimiche, Università degli Studi di Catania, and INSTM udr Catania, viale Andrea Doria 6, 95125, Catania; Lo Nigro, Raffaella

    This letter reports on the negative charge trapping in Al{sub 2}O{sub 3} thin films grown by atomic layer deposition onto oxidized silicon carbide (4H-SiC). The films exhibited a permittivity of 8.4, a breakdown field of 9.2 MV/cm and small hysteresis under moderate bias cycles. However, severe electron trapping inside the Al{sub 2}O{sub 3} film (1 × 10{sup 12} cm{sup −2}) occurs upon high positive bias stress (>10 V). Capacitance-voltage measurements at different temperatures and stress conditions have been used to determine an activation energy of 0.1 eV. The results provide indications on the possible nature of the trapping defects and,more » hence, on the strategies to improve this technology for 4H-SiC devices.« less

  5. Metal-Organic Framework-Derived Reduced Graphene Oxide-Supported ZnO/ZnCo2O4/C Hollow Nanocages as Cathode Catalysts for Aluminum-O2 Batteries.

    PubMed

    Liu, Yisi; Jiang, Hao; Hao, Jiayu; Liu, Yulong; Shen, Haibo; Li, Wenzhang; Li, Jie

    2017-09-20

    Aluminum-air battery is a promising candidate for large-scale energy applications because of its low cost and high energy density. Remarkably, tremendous efforts have been concentrated on developing efficient and stable cathode electrocatalysts toward the oxygen reduction reaction. In this work, a hydrothermal-calcination approach was utilized to prepare novel reduced graphene oxide (rGO)-supported hollow ZnO/ZnCo 2 O 4 nanoparticle-embedded carbon nanocages (ZnO/ZnCo 2 O 4 /C@rGO) using a zeolitic imidazolate framework (ZIF-67)/graphene oxide/zinc nitrate composite as the precursor. The ZnO/ZnCo 2 O 4 /C@rGO hybrid exhibits remarkable electrocatalytic performance for oxygen reduction reaction under alkaline conditions and superior stability and methanol tolerance to those of the commercial Pt/C catalyst. Furthermore, novel and simple Al-air coin cells were first fabricated using the hybrid materials as cathode catalysts under ambient air conditions to further investigate their catalytic performance. The coin cell with the ZnO/ZnCo 2 O 4 /C@rGO cathode catalyst displays a higher open circuit voltage and discharge voltage and more sluggish potential drop than those of the cell with the ZnO/ZnCo 2 O 4 /C cathode catalyst, which confirms that rGO can enhance the electrocatalytic activity and stability of the catalyst system. The excellent electrocatalytic performance of the ZnO/ZnCo 2 O 4 /C@rGO hybrid is attributed to the prominent conductivity and high specific surface area resulting from rGO, the more accessible catalytic active sites induced by the unique porous hollow nanocage structure, and synergic covalent coupling between rGO sheets and ZnO/ZnCo 2 O 4 /C nanocages.

  6. Effect of Na4O7P2 on Cu powder preparation from Cu2O-water slurry system.

    PubMed

    Ahn, J G; Hoang, T H; Kim, D J; Kim, M S; Kim, C O; Chung, H S

    2008-03-01

    A unique approach is presented for preparing highly dispersed ultrafine copper particles from cuprous oxide slurry using a wet chemical reaction with hydrazine (N2H4) as a reductant along with an appropriate addition of sodium pyrophosphate (Na4O7P2) as a surfactant. It was found that very thin oxidized surfaces on the copper particles are formed during the reaction in the solution and subsequently sodium pyrophosphate plays an important role in the zeta potential of the particles, affecting their dispersion and growth significantly. The copper particles at low zeta potential easily aggregate and grow to bigger ones, whereas they at high zeta potential keep away each other and grew individually to ultrafine size. Additionally, a model for the copper particles growth in accordance with dispersion is proposed.

  7. Structural and optical characterization of terbium doped ZnGa{sub 2}O{sub 4} thin films deposited by RF magnetron sputtering

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Somasundaram, K.; Department of Physics, Nallamuthu Gounder Mahalingam College, Pollachi-642001; Girija, K. G., E-mail: kgirija@barc.gov.in

    2016-05-23

    Tb{sup 3+} doped ZnGa{sub 2}O{sub 4} nanophosphor (21 nm) has been synthesized via low temperature polyol route and subsequently thin films of the same were deposited on glass and ITO substrates by RF magnetron sputtering. The films were characterized by X-ray Diffraction and luminescence measurements. The XRD pattern showed that Tb{sup 3+} doped ZnGa{sub 2}O{sub 4} nanophosphor has a cubic spinel phase. Luminescence behavior of the nanophosphor and as deposited sputtered film was investigated. The PL emission spectra of nanophosphor gave a broad ZnGa{sub 2}O{sub 4} host emission band along with a strong terbium emission and the thin films showedmore » only broad host emission band and there was no terbium ion emission.« less

  8. Electro-thermal control of aluminum-doped zinc oxide/vanadium dioxide multilayered thin films for smart-device applications

    PubMed Central

    Skuza, J. R.; Scott, D. W.; Mundle, R. M.; Pradhan, A. K.

    2016-01-01

    We demonstrate the electro-thermal control of aluminum-doped zinc oxide (Al:ZnO) /vanadium dioxide (VO2) multilayered thin films, where the application of a small electric field enables precise control of the applied heat to the VO2 thin film to induce its semiconductor-metal transition (SMT). The transparent conducting oxide nature of the top Al:ZnO film can be tuned to facilitate the fine control of the SMT of the VO2 thin film and its associated properties. In addition, the Al:ZnO film provides a capping layer to the VO2 thin film, which inhibits oxidation to a more energetically favorable and stable V2O5 phase. It also decreases the SMT of the VO2 thin film by approximately 5–10 °C because of an additional stress induced on the VO2 thin film and/or an alteration of the oxygen vacancy concentration in the VO2 thin film. These results have significant impacts on technological applications for both passive and active devices by exploiting this near-room-temperature SMT. PMID:26884225

  9. Epitaxial growth and dielectric properties of Pb0.4Sr0.6TiO3 thin films on (00l)-oriented metallic Li0.3Ni0.7O2 coated MgO substrates

    NASA Astrophysics Data System (ADS)

    Li, X. T.; Du, P. Y.; Mak, C. L.; Wong, K. H.

    2007-06-01

    Highly (00l)-oriented Li0.3Ni0.7O2 thin films have been fabricated on (001) MgO substrates by pulsed laser deposition. The Pb0.4Sr0.6TiO3 (PST40) thin film deposited subsequently also shows a significant (00l)-oriented texture. Both the PST40 and Li0.3Ni0.7O2 have good epitaxial behavior. The epitaxial growth of the PST40 thin film is more perfect with the Li0.3Ni0.7O2 buffer layer due to the less distortion in the film. The dielectric tunability of the PST40 thin film with Li0.3Ni0.7O2 buffer layer therefore reaches 70%, which is 75% higher than that without Li0.3Ni0.7O2 buffer layer, and the dielectric loss of the PST40 thin film is 0.06.

  10. Electromagnetic characteristics of manganese oxide-coated Fe3O4 nanoparticles at 2-18 GHz

    NASA Astrophysics Data System (ADS)

    Yang, R. B.; Liang, W. F.; Lin, C. K.

    2011-04-01

    The dielectric and magnetic properties of manganese oxide-coated Fe3O4 nanoparticles (NPs) were measured by the transmission/reflection method in 2-18 GHz. MnOx-coated Fe3O4 NPs were prepared by sol-gel method followed by heat-treating at 300, 400, and 500 °C, respectively. The heat-treated powders were then used as magnetic fillers and added to an epoxy resin to prepare MnOx-coated Fe3O4 composites for the complex permittivity (ɛ'-jɛ″) and permeability (μ'-jμ″) measurements. After the sol-gel process, the coating of manganese oxide (mixture of major Mn2O3 and minor Mn3O4) reduced the value of ɛ'. The lower the heat-treating temperature, the larger the decrease in ɛ'. The relative decrease in ɛ', compared with uncoated Fe3O4 nanoparticles, is 28.7, 23.5, and 20.0% for coated MnOx heat-treated at 300, 400, and 500 °C, respectively, while the relative decrease in ɛ″ is 74.1, 68.8, and 65.2%, respectively. In the present study, MnOx-coated Fe3O4 exhibited a significant decrease in dielectric loss tangent of ˜100% compared to that of uncoated NPs and can be of practical use for microwave components.

  11. Graphene oxide coated with porous iron oxide ribbons for 2, 4-Dichlorophenoxyacetic acid (2,4-D) removal.

    PubMed

    Nethaji, S; Sivasamy, A

    2017-04-01

    Graphene oxide (GO) was prepared from commercially available graphite powder. Porous iron oxide ribbons were grown on the surface of GO by solvothermal process. The prepared GO-Fe 3 O 4 nanocomposites are characterized by FT-IR, XRD, VSM, SEM, TEM, Raman spectroscopy, surface functionality and zero point charge studies. The morphology of the iron oxide ribbons grown on GO is demonstrated with TEM at various magnifications. The presence of magnetite nanoparticles is evident from XRD peaks and the magnetization value is found to be 37.28emu/g. The ratio of intensity of D-peak to G-peak from Raman spectrum is 0.995. The synthesized Graphene oxide-Fe 3 O 4 nanocomposites (GO-Fe 3 O 4 ) were explored for its surface adsorptive properties by using a model organic compound, 2,4-Dichlorophenoxy acetic acid (2,4-D) from aqueous solution. Batch adsorption studies were performed and the equilibrium data are modelled with Langmuir, Freundlich and Temkin isotherms. The maximum monolayer capacity from Langmuir isotherm is 67.26mg/g. Kinetic studies were also carried out and the studied adsorption process followed pseudo second-order rate equation. Mechanism of the adsorption process is studied by fitting the data with intraparticle diffusion model and Boyd plot. The studied adsorption process is both by film diffusion and intraparticle diffusion. Copyright © 2017 Elsevier Inc. All rights reserved.

  12. Oxidation of benzyl alcohol by K2FeO4 to benzaldehyde over zeolites

    NASA Astrophysics Data System (ADS)

    Wang, Yuan-Yuan; Song, Hua; Song, Hua-Lin; Jin, Zai-Shun

    2016-10-01

    A novel and green procedure for benzaldehyde synthesis by potassium ferrate oxidation of benzyl alcohol employing zeolite catalysts was studied. The prepared oxidant was characterized by SEM and XRD. The catalytic activity of various solid catalysts was studied using benzyl alcohol as a model compound. USY was found to be a very efficient catalyst for this particular oxidation process. Benzaldehyde yields up to 96.0% could be obtained at the following optimal conditions: 0.2 mL of benzyl alcohol, 4 mmol of K2FeO4, 0.5 g of USY zeolite; 20 mL of cyclohexene, 0.3 mL of acetic acid (36 wt %), 30°C temperature, 4 h reaction time.

  13. Ultra-thin solid oxide fuel cells: Materials and devices

    NASA Astrophysics Data System (ADS)

    Kerman, Kian

    Solid oxide fuel cells are electrochemical energy conversion devices utilizing solid electrolytes transporting O2- that typically operate in the 800 -- 1000 °C temperature range due to the large activation barrier for ionic transport. Reducing electrolyte thickness or increasing ionic conductivity can enable lower temperature operation for both stationary and portable applications. This thesis is focused on the fabrication of free standing ultrathin (<100 nm) oxide membranes of prototypical O 2- conducting electrolytes, namely Y2O3-doped ZrO2 and Gd2O3-doped CeO2. Fabrication of such membranes requires an understanding of thin plate mechanics coupled with controllable thin film deposition processes. Integration of free standing membranes into proof-of-concept fuel cell devices necessitates ideal electrode assemblies as well as creative processing schemes to experimentally test devices in a high temperature dual environment chamber. We present a simple elastic model to determine stable buckling configurations for free standing oxide membranes. This guides the experimental methodology for Y 2O3-doped ZrO2 film processing, which enables tunable internal stress in the films. Using these criteria, we fabricate robust Y2O3-doped ZrO2 membranes on Si and composite polymeric substrates by semiconductor and micro-machining processes, respectively. Fuel cell devices integrating these membranes with metallic electrodes are demonstrated to operate in the 300 -- 500 °C range, exhibiting record performance at such temperatures. A model combining physical transport of electronic carriers in an insulating film and electrochemical aspects of transport is developed to determine the limits of performance enhancement expected via electrolyte thickness reduction. Free standing oxide heterostructures, i.e. electrolyte membrane and oxide electrodes, are demonstrated. Lastly, using Y2O3-doped ZrO2 and Gd2O 3-doped CeO2, novel electrolyte fabrication schemes are explored to develop oxide

  14. Growth and Characterization of Wide Bandgap Semiconductor Oxide Thin Films

    NASA Astrophysics Data System (ADS)

    Ghose, Susmita

    Wide bandgap semiconductors are receiving extensive attention due to their exceptional physical and chemical properties making them useful for high efficiency and high power electronic devices. Comparing other conventional wide bandgap materials, monoclinic beta-Ga2O3 also represents an outstanding semiconductor oxide for next generation of UV optoelectronics and high temperature sensors due to its wide band gap ( 4.9eV). This new semiconductor material has higher breakdown voltage (8MV/cm) and n-type conductivity which make it more suitable for potential application as high power electronics. The properties and potential applications of these wide bandgap materials have not yet fully explored. In this study, the growth and characterization of single crystal beta-Ga2O3 thin films grown on c-plane sapphire (Al2O3) substrate using two different techniques; molecular beam epitaxy (MBE) and pulsed laser deposition (PLD) techniques has been investigated. The influence of the growth parameters of MBE and PLD on crystalline quality and surface has been explored. Two methods have been used to grow Ga2O3 using MBE; one method is to use elemental Ga and the second is the use of a polycrystalline Ga2O3 compound source with and without an oxygen source. Using the elemental Ga source, growth rate of beta-Ga2O3 thin films was limited due to the formation and desorption of Ga2O molecules. In order to mitigate this problem, a compound Ga2O3 source has been introduced and used for the growth of crystalline beta-Ga2O 3 thin films without the need for additional oxygen since this source produces Ga-O molecules and additional oxygen. Two different alloys (InGa) 2O3 and (AlGa)2O3 has been grown on c-plane sapphire substrate by pulsed laser deposition technique to tune the bandgap of the oxide thin films from 3.5-8.6 eV suitable for applications such as wavelength-tunable optical devices, solid-state lighting and high electron mobility transistors (HEMTs). The crystallinity, chemical

  15. Electrical and Infrared Optical Properties of Vanadium Oxide Semiconducting Thin-Film Thermometers

    NASA Astrophysics Data System (ADS)

    Zia, Muhammad Fakhar; Abdel-Rahman, Mohamed; Alduraibi, Mohammad; Ilahi, Bouraoui; Awad, Ehab; Majzoub, Sohaib

    2017-10-01

    A synthesis method has been developed for preparation of vanadium oxide thermometer thin film for microbolometer application. The structure presented is a 95-nm thin film prepared by sputter-depositing nine alternating multilayer thin films of vanadium pentoxide (V2O5) with thickness of 15 nm and vanadium with thickness of 5 nm followed by postdeposition annealing at 300°C in nitrogen (N2) and oxygen (O2) atmospheres. The resulting vanadium oxide (V x O y ) thermometer thin films exhibited temperature coefficient of resistance (TCR) of -3.55%/°C with room-temperature resistivity of 2.68 Ω cm for structures annealed in N2 atmosphere, and TCR of -3.06%/°C with room-temperature resistivity of 0.84 Ω cm for structures annealed in O2 atmosphere. Furthermore, optical measurements of N2- and O2-annealed samples were performed by Fourier-transform infrared ellipsometry to determine their dispersion curves, refractive index ( n), and extinction coefficient ( k) at wavelength from 7000 nm to 14,000 nm. The results indicate the possibility of applying the developed materials in thermometers for microbolometers.

  16. Zirconium doped TiO2 thin films deposited by chemical spray pyrolysis

    NASA Astrophysics Data System (ADS)

    Juma, A.; Oja Acik, I.; Oluwabi, A. T.; Mere, A.; Mikli, V.; Danilson, M.; Krunks, M.

    2016-11-01

    Chemical spray pyrolysis (CSP) is a flexible deposition technique that allows for mixing of the precursor solutions in different proportions suitable for doping thin films. The CSP method was used to dope TiO2 thin films with Zr by adding zirconium(IV) acetylacetonate into a solution of titanium(IV) isopropoxide in ethanol stabilized by acetylacetone at [Zr]/[Ti] of 0, 5, 10 and 20 at%. The Zr-doped TiO2 thin films were uniform and homogeneous showing much smaller grains than the undoped TiO2 films. Zr stabilized the anatase phase to temperatures above 800 °C depending on Zr concentration in the spray solution. The concentration of Zr determined by XPS was 6.4 at% for the thin film deposited from the 20 at% solution. According to AFM studies, Zr doping decreased the root mean square roughness of TiO2 film from 5.9 to 1.1 nm. An XRD study of samples with the highest Zr amount showed the ZrTiO4 phase started forming after annealing at 800 °C. The optical band gap for TiO2 decreased from 3.3 eV to 3.0 eV after annealing at 800 °C but for the TiO2:Zr(20) film it remained at 3.4 eV. The dielectric constant increased by more than four times with Zr-doping and this was associated with the change in the bond formations caused by substitution of Ti by Zr in the lattice.

  17. Atomically layer-by-layer diffusion of oxygen/hydrogen in highly epitaxial PrBaCo2O5.5+δ thin films

    NASA Astrophysics Data System (ADS)

    Bao, Shanyong; Xu, Xing; Enriquez, Erik; Mace, Brennan E.; Chen, Garry; Kelliher, Sean P.; Chen, Chonglin; Zhang, Yamei; Whangbo, Myung-Hwan; Dong, Chuang; Zhang, Qinyu

    2015-12-01

    Single-crystalline epitaxial thin films of PrBaCo2O5.5+δ (PrBCO) were prepared, and their resistance R(t) under a switching flow of oxidizing and reducing gases were measured as a function of the gas flow time t in the temperature range of 200-800 °C. During the oxidation cycle under O2, the PrBCO films exhibit fast oscillations in their dR(t)/dt vs. t plots, which reflect the oxidation processes, Co2+/Co3+ → Co3+ and Co3+ → Co3+/Co4+, that the Co atoms of PrBCO undergo. Each oscillation consists of two peaks, with larger and smaller peaks representing the oxygen/hydrogen diffusion through the (BaO)(CoO2)(PrO)(CoO2) layers of PrBCO via the oxygen-vacancy-exchange mechanism. This finding paves a significant avenue for cathode materials operating in low-temperature solid-oxide-fuel-cell devices and for chemical sensors with wide range of operating temperature.

  18. Thermo-Optical Properties of Thin-Film TiO2–Al2O3 Bilayers Fabricated by Atomic Layer Deposition

    PubMed Central

    Ali, Rizwan; Saleem, Muhammad Rizwan; Pääkkönen, Pertti; Honkanen, Seppo

    2015-01-01

    We investigate the optical and thermo-optical properties of amorphous TiO2–Al2O3 thin-film bilayers fabricated by atomic layer deposition (ALD). Seven samples of TiO2–Al2O3 bilayers are fabricated by growing Al2O3 films of different thicknesses on the surface of TiO2 films of constant thickness (100 nm). Temperature-induced changes in the optical refractive indices of these thin-film bilayers are measured by a variable angle spectroscopic ellipsometer VASE®. The optical data and the thermo-optic coefficients of the films are retrieved and calculated by applying the Cauchy model and the linear fitting regression algorithm, in order to evaluate the surface porosity model of TiO2 films. The effects of TiO2 surface defects on the films’ thermo-optic properties are reduced and modified by depositing ultra-thin ALD-Al2O3 diffusion barrier layers. Increasing the ALD-Al2O3 thickness from 20 nm to 30 nm results in a sign change of the thermo-optic coefficient of the ALD-TiO2. The thermo-optic coefficients of the 100 nm-thick ALD-TiO2 film and 30 nm-thick ALD-Al2O3 film in a bilayer are (0.048 ± 0.134) × 10−4 °C−1 and (0.680 ± 0.313) × 10−4 °C−1, respectively, at a temperature T = 62 °C.

  19. Thermogravimetric, Calorimetric, and Structural Studies of the Co3 O4 /CoO Oxidation/Reduction Reaction

    NASA Astrophysics Data System (ADS)

    Unruh, Karl; Cichocki, Ronald; Kelly, Brian; Poirier, Gerald

    2015-03-01

    To better assess the potential of cobalt oxide for thermal energy storage (TES), the Co3O4/CoO oxidation/reduction reaction has been studied by thermogravimetric (TGA), calorimetric (DSC), and x-ray diffraction (XRD) measurements in N2 and atmospheric air environments. TGA measurements showed an abrupt mass loss of about 6.6% in both N2 and air, consistent with the stoichiometric reduction of Co3O4 to CoO and structural measurements. The onset temperature of the reduction of Co3O4 in air was only weakly dependent on the sample heating rate and occurred at about 910 °C. The onset temperature for the oxidation of CoO varied between about 850 and 875 °C for cooling rates between 1 and 20 °C/min, but complete re-conversion to Co3O4 could only be achieved at the slowest cooling rates. Due to the dependence of the rate constant on the oxygen partial pressure, the oxidation of Co3O4 in a N2 environment occurred at temperatures between about 775 and 825 °C for heating rates between 1 and 20 °C/min and no subsequent re-oxidation of the reduced Co3O4 was observed on cooling to room temperature. In conjunction with a measured transition heat of about 600 J/g of Co3O4, these measurements indicate that cobalt oxide is a viable TES material.

  20. Fabrication and electrochemical performance of a stable, anode supported thin BaCe0.4Zr0.4Y0.2O3-δ electrolyte Protonic Ceramic Fuel Cell

    NASA Astrophysics Data System (ADS)

    Nasani, Narendar; Ramasamy, Devaraj; Mikhalev, Sergey; Kovalevsky, Andrei V.; Fagg, Duncan P.

    2015-03-01

    The present work deals with the fabrication and electrochemical characterisation of a potential protonic ceramic fuel cell based on a Ni-BaZr0.85Y0.15O3-δ anode supported thin film proton conducting BaCe0.4Zr0.4Y0.2O3-δ electrolyte with a Pr2NiO4+δ cathode. Anode and electrolyte materials were prepared by an acetate-H2O2 combustion method. A thin (∼5 μm), dense and crack free BaCe0.4Zr0.4Y0.2O3-δ electrolyte film was successfully obtained on a porous anode support by spin coating and firing at 1450 °C. Maximum power densities of 234, 158, 102 and 63 mW cm-2 at 700, 650, 600 and 550 °C, respectively were achieved for the Ni-BaZr0.85Y0.15O3-δ/BaCe0.4Zr0.4Y0.2O3-δ/Pr2NiO4+δ single cell under fuel cell testing conditions. Electrode polarisation resistance was assessed at open circuit conditions by use of electrochemical impedance spectroscopy (EIS) and is shown to dominate the area specific resistance at low temperatures. Postmortem analysis by scanning electron microscopy (SEM), reveals that no delamination occurs at anode/electrolyte or electrolyte/cathode interfaces upon cell operation.

  1. Growth and physical investigations of sprayed ZnMoO4 thin films along with wettability tests

    NASA Astrophysics Data System (ADS)

    Askri, Besma; Mhamdi, Ammar; Mahdhi, Noureddine; Amlouk, Mosbah

    2018-06-01

    Ternary oxides based on zinc and molybdenum elements have known as semiconductor oxides with large band gap energies. With the focus mainly on their synthesis by cost-effective process as thin films, the aspect of their stability and reactivity as transparent layers against both UV radiation and oxidation under wet medium due to their oxygen deficiency has so far not been investigated. This work covers the synthesis as well as the structural, electrical and the wettability properties of ZnMoO4 thin films which have been prepared by the spray pyrolysis method on glass substrates at 460 °C. First, X-ray diffraction analysis shows that this oxide crystallizes in triclinic structure with the space group P-1. The thickness value of ZnMoO4 thin film of about 1.5 μm was estimated by spectroscopic ellipsometry (SE). Moreover, a special emphasis has been focused on the photoluminescence properties of such films to reach possible presence of defaults and oxygen vacancy. Second, the electrical conductivity, conduction mechanism, relaxation model of these films were indeed studied using impedance spectroscopy technique in the frequency range 10-1-106 Hz at various temperatures (25-300 °C). At high temperature, σAC conductivity obeys to the power law established by Jonscher. Besides, the variation of σDC with the inverse of the temperature follows Arrhenius law. This evolution suggests that the conduction process is thermally activated and the activation energy of this process is equal to 0.97 eV. Finally, the wettability tests reveal that zinc molybdates loses its hydrophobic character during aging under UV radiation to become completely hydrophilic. All these physical investigations demonstrated that such ternary oxide contains oxygen deficiency which may be of interest for photocatalytic purposes and pave the way for various sensitivity applications like gas and bio-sensors.

  2. An enhancement of photoluminescence property of Ag doped La2O3 thin films at room temperature

    NASA Astrophysics Data System (ADS)

    Jbeli, R.; Boukhachem, A.; Ben Jemaa, I.; Mahdhi, N.; Saadallah, F.; Elhouichet, H.; Alleg, S.; Amlouk, M.; Ezzaouïa, H.

    2017-09-01

    Metal transition doped oxide thin films or nanocomposites have recently emerged at the forefront of potentials research. With the focus mainly on efficiency, the aspect of stability against optical irradiation of such materials has so far not been thoroughly addressed. This work covers the synthesis of silver doped lanthanum oxide thin films (La2O3:Ag) which have been prepared by the spray pyrolysis technique on glass substrates at 460 °C. Then, Ag thin films were grown on lanthanum oxide thin films by thermal evaporation. The present work aims to reach the synthesis of La2O3:Ag thin films using both the spray pyrolysis and thermal evaporation techniques. First, X-ray diffraction analysis shows that undoped and Ag doped films crystallize in a mixture of hexagonal and cubic phase with crystallites oriented along (001) direction. Raman spectroscopy shows the bands positions corresponding to hexagonal and cubic phases. On the other hand, an attempt regarding their optical properties has been carried out by means of photoluminescence measurements. Second, from electrical conductivity measurements, the activation energy decreases from 1.42 to 1.09 eV with the increase of annealing time and the charge carriers are following the CBH model as dominant charge transport mechanism. Finally, the annealing time influences the surface wettability property and transforms La2O3 character from hydrophobic (θ > 90°) to hydrophilic (θ < 90°).

  3. An enhancement of photoluminescence property of Ag doped La2O3 thin films at room temperature.

    PubMed

    Jbeli, R; Boukhachem, A; Ben Jemaa, I; Mahdhi, N; Saadallah, F; Elhouichet, H; Alleg, S; Amlouk, M; Ezzaouïa, H

    2017-09-05

    Metal transition doped oxide thin films or nanocomposites have recently emerged at the forefront of potentials research. With the focus mainly on efficiency, the aspect of stability against optical irradiation of such materials has so far not been thoroughly addressed. This work covers the synthesis of silver doped lanthanum oxide thin films (La 2 O 3 :Ag) which have been prepared by the spray pyrolysis technique on glass substrates at 460°C. Then, Ag thin films were grown on lanthanum oxide thin films by thermal evaporation. The present work aims to reach the synthesis of La 2 O 3 :Ag thin films using both the spray pyrolysis and thermal evaporation techniques. First, X-ray diffraction analysis shows that undoped and Ag doped films crystallize in a mixture of hexagonal and cubic phase with crystallites oriented along (001) direction. Raman spectroscopy shows the bands positions corresponding to hexagonal and cubic phases. On the other hand, an attempt regarding their optical properties has been carried out by means of photoluminescence measurements. Second, from electrical conductivity measurements, the activation energy decreases from 1.42 to 1.09eV with the increase of annealing time and the charge carriers are following the CBH model as dominant charge transport mechanism. Finally, the annealing time influences the surface wettability property and transforms La 2 O 3 character from hydrophobic (θ>90°) to hydrophilic (θ<90°). Copyright © 2017 Elsevier B.V. All rights reserved.

  4. TI--CR--AL--O thin film resistors

    DOEpatents

    Jankowski, Alan F.; Schmid, Anthony P.

    2000-01-01

    Thin films of Ti--Cr--Al--O are used as a resistor material. The films are rf sputter deposited from ceramic targets using a reactive working gas mixture of Ar and O.sub.2. Resistivity values from 10.sup.4 to 10.sup.10 Ohm-cm have been measured for Ti--Cr--Al--O film <1 .mu.m thick. The film resistivity can be discretely selected through control of the target composition and the deposition parameters. The application of Ti--Cr--Al--O as a thin film resistor has been found to be thermodynamically stable, unlike other metal-oxide films. The Ti--Cr--Al--O film can be used as a vertical or lateral resistor, for example, as a layer beneath a field emission cathode in a flat panel display; or used to control surface emissivity, for example, as a coating on an insulating material such as vertical wall supports in flat panel displays.

  5. Mn1.4Co1.4Cu0.2O4 spinel protective coating on ferritic stainless steels for solid oxide fuel cell interconnect applications

    NASA Astrophysics Data System (ADS)

    Chen, Guoyi; Xin, Xianshuang; Luo, Ting; Liu, Leimin; Zhou, Yuchun; Yuan, Chun; Lin, Chucheng; Zhan, Zhongliang; Wang, Shaorong

    2015-03-01

    In an attempt to reduce the oxidation and Cr evaporation rates of solid oxide fuel cells (SOFCs), Mn1.4Co1.4Cu0.2O4 spinel coating is developed on the Crofer22 APU ferritic stainless steel substrate by a powder reduction technique. Doping of Cu into Mn-Co spinels improves electrical conductivity as well as thermal expansion match with the Crofer22 APU interconnect. Good adhesion between the coating and the alloy substrate is achieved by the reactive sintering process using the reduced powders. Long-term isothermal oxidation experiment and area specific resistance (ASR) measurement are investigated. The ASR is less than 4 mΩ cm2 even though the coated alloy undergoes oxidation at 800 °C for 530 h and four thermal cycles from 800 °C to room temperature. The Mn1.4Co1.4Cu0.2O4 spinel coatings demonstrate excellent anti-oxidation performance and long-term stability. It exhibits a promising prospect for the practical application of SOFC alloy interconnect.

  6. Artificial Metalloproteins Containing Co 4O 4Cubane Active Sites

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Olshansky, Lisa; Huerta-Lavorie, Raul; Nguyen, Andy I.

    Artificial metalloproteins (ArMs) containing Co 4O 4 cubane active sites were constructed via biotin-streptavidin technology. Stabilized by hydrogen bonds (H-bonds), terminal and cofacial Co III-OH 2 moieties are observed crystallographically in a series of immobilized cubane sites. Solution electrochemistry provided correlations of oxidation potential and pH. For variants containing Ser and Phe adjacent to the metallocofactor, 1e -/1H + chemistry predominates until pH 8, above which the oxidation becomes pH-independent. Installation of Tyr proximal to the Co 4O 4 active site provided a single H-bond to one of a set of cofacial Co III-OH 2 groups. With this variant, multi-emore » - /multi-H + chemistry is observed, along with a change in mechanism at pH 9.5 that is consistent with Tyr deprotonation. Finally, with structural similarities to both the oxygen-evolving complex of photosystem II (H-bonded Tyr) and to thin film water oxidation catalysts (Co 4O 4 core), these findings bridge synthetic and biological systems for water oxidation, highlighting the importance of secondary sphere interactions in mediating multi-e - /multi-H + reactivity.« less

  7. Artificial Metalloproteins Containing Co 4O 4Cubane Active Sites

    DOE PAGES

    Olshansky, Lisa; Huerta-Lavorie, Raul; Nguyen, Andy I.; ...

    2018-02-05

    Artificial metalloproteins (ArMs) containing Co 4O 4 cubane active sites were constructed via biotin-streptavidin technology. Stabilized by hydrogen bonds (H-bonds), terminal and cofacial Co III-OH 2 moieties are observed crystallographically in a series of immobilized cubane sites. Solution electrochemistry provided correlations of oxidation potential and pH. For variants containing Ser and Phe adjacent to the metallocofactor, 1e -/1H + chemistry predominates until pH 8, above which the oxidation becomes pH-independent. Installation of Tyr proximal to the Co 4O 4 active site provided a single H-bond to one of a set of cofacial Co III-OH 2 groups. With this variant, multi-emore » - /multi-H + chemistry is observed, along with a change in mechanism at pH 9.5 that is consistent with Tyr deprotonation. Finally, with structural similarities to both the oxygen-evolving complex of photosystem II (H-bonded Tyr) and to thin film water oxidation catalysts (Co 4O 4 core), these findings bridge synthetic and biological systems for water oxidation, highlighting the importance of secondary sphere interactions in mediating multi-e - /multi-H + reactivity.« less

  8. Efficiency enhancement using a Zn1- x Ge x -O thin film as an n-type window layer in Cu2O-based heterojunction solar cells

    NASA Astrophysics Data System (ADS)

    Minami, Tadatsugu; Nishi, Yuki; Miyata, Toshihiro

    2016-05-01

    Efficiency enhancement was achieved in Cu2O-based heterojunction solar cells fabricated with a zinc-germanium-oxide (Zn1- x Ge x -O) thin film as the n-type window layer and a p-type Na-doped Cu2O (Cu2O:Na) sheet prepared by thermally oxidizing Cu sheets. The Ge content (x) dependence of the obtained photovoltaic properties of the heterojunction solar cells is mainly explained by the conduction band discontinuity that results from the electron affinity difference between Zn1- x Ge x -O and Cu2O:Na. The optimal value of x in Zn1- x Ge x -O thin films prepared by pulsed laser deposition was observed to be 0.62. An efficiency of 8.1% was obtained in a MgF2/Al-doped ZnO/Zn0.38Ge0.62-O/Cu2O:Na heterojunction solar cell.

  9. Photoconductivity in nanostructured sulfur-doped V2O5 thin films

    NASA Astrophysics Data System (ADS)

    Mousavi, M.; Yazdi, Sh. Tabatabai

    2016-03-01

    In this paper, S-doped vanadium oxide thin films with doping levels up to 40 at.% are prepared via spray pyrolysis method on glass substrates, and the effect of S-doping on the structural and photoconductivity related properties of β-V2O5 thin films is studied. The results show that most of the films have been grown in the tetragonal β-V2O5 phase structure with the preferred orientation along [200]. With increasing the doping level, the samples tend to be amorphous. The structure of the samples reveals to be nanobelt-shaped whose width decreases from nearly 100 nm to 40 nm with S concentration. The photoconductivity measurements show that by increasing the S-doping level, the photosensitivity increases, which is due to the prolonged electron’s lifetime as a result of enhanced defect states acting as trap levels.

  10. Treatment of landfill leachate biochemical effluent using the nano-Fe3O4/Na2S2O8 system: Oxidation performance, wastewater spectral analysis, and activator characterization.

    PubMed

    Liu, Zhanmeng; Li, Xian; Rao, Zhiwei; Hu, Fengping

    2018-02-15

    Nano-Fe 3 O 4 was used as heterogeneous catalyst to activate Na 2 S 2 O 8 for the generation of the sulfate radicals (SO 4 - ) to oxidize the residual pollutants in landfill leachate biochemical effluent. The oxidation performance, wastewater spectral analysis and activator characterization were discussed. Oxidation experimental result shows that nano-Fe 3 O 4 has obvious catalytic effect on Na 2 S 2 O 8 and can significantly enhance the oxidation efficiencies of Na 2 S 2 O 8 on landfill leachate biochemical effluent, with COD and color removals above 63% and 95%, respectively. Based on the analyses of three-dimensional excitation emission matrix fluorescence spectrum (3DEEM), ultraviolet-visible spectra (UV-vis), and Fourier Transform infrared spectroscopy (FTIR) of wastewater samples before and after treatment, it can be concluded that the pollution level of dissolved organic matter (DOM) declined and that the humic acid (HA) fractions were efficiently degraded into small molecules of fulvic acid (FA) fractions with less weight and stable structure. Compared to the raw wastewater sample, the aromaticity and substituent groups of the DOM were lessened in the treated wastewater sample. Moreover, the main structure of the organics and functional groups were changed by the Fe 3 O 4 /Na 2 S 2 O 8 system, with substantial decrease of conjugated double bonds. The micro morphology of nano-Fe 3 O 4 was characterized before and after reaction by the methods of scanning electron microscope spectra (SEM), X-ray diffraction pattern (XRD), and X-ray photoelectron spectroscopy (XPS). The XRD pattern analysis showed that nano-Fe 3 O 4 was oxidized into r-Fe 2 O 3 and that the particle size of it also became smaller after reaction. XPS was employed to analyze the content and iron valence on the nano-Fe 3 O 4 surface, and it can be found that the ratio of Fe 3+ /Fe 2+ decreased from 1.8 before reaction to 0.8 after reaction. From the SEM analysis after the treatment, it was

  11. Structural and electrical characteristics of high-κ Er2O3 and Er2TiO5 gate dielectrics for a-IGZO thin-film transistors

    PubMed Central

    2013-01-01

    In this letter, we investigated the structural and electrical characteristics of high-κ Er2O3 and Er2TiO5 gate dielectrics on the amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistor (TFT) devices. Compared with the Er2O3 dielectric, the a-IGZO TFT device incorporating an Er2TiO5 gate dielectric exhibited a low threshold voltage of 0.39 V, a high field-effect mobility of 8.8 cm2/Vs, a small subthreshold swing of 143 mV/decade, and a high Ion/Ioff current ratio of 4.23 × 107, presumably because of the reduction in the oxygen vacancies and the formation of the smooth surface roughness as a result of the incorporation of Ti into the Er2TiO5 film. Furthermore, the reliability of voltage stress can be improved using an Er2TiO5 gate dielectric. PMID:23294730

  12. Structural and electrical characteristics of high-κ Er2O3 and Er2TiO5 gate dielectrics for a-IGZO thin-film transistors.

    PubMed

    Chen, Fa-Hsyang; Her, Jim-Long; Shao, Yu-Hsuan; Matsuda, Yasuhiro H; Pan, Tung-Ming

    2013-01-08

    In this letter, we investigated the structural and electrical characteristics of high-κ Er2O3 and Er2TiO5 gate dielectrics on the amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistor (TFT) devices. Compared with the Er2O3 dielectric, the a-IGZO TFT device incorporating an Er2TiO5 gate dielectric exhibited a low threshold voltage of 0.39 V, a high field-effect mobility of 8.8 cm2/Vs, a small subthreshold swing of 143 mV/decade, and a high Ion/Ioff current ratio of 4.23 × 107, presumably because of the reduction in the oxygen vacancies and the formation of the smooth surface roughness as a result of the incorporation of Ti into the Er2TiO5 film. Furthermore, the reliability of voltage stress can be improved using an Er2TiO5 gate dielectric.

  13. Heterojunction oxide thin-film transistors with unprecedented electron mobility grown from solution.

    PubMed

    Faber, Hendrik; Das, Satyajit; Lin, Yen-Hung; Pliatsikas, Nikos; Zhao, Kui; Kehagias, Thomas; Dimitrakopulos, George; Amassian, Aram; Patsalas, Panos A; Anthopoulos, Thomas D

    2017-03-01

    Thin-film transistors made of solution-processed metal oxide semiconductors hold great promise for application in the emerging sector of large-area electronics. However, further advancement of the technology is hindered by limitations associated with the extrinsic electron transport properties of the often defect-prone oxides. We overcome this limitation by replacing the single-layer semiconductor channel with a low-dimensional, solution-grown In 2 O 3 /ZnO heterojunction. We find that In 2 O 3 /ZnO transistors exhibit band-like electron transport, with mobility values significantly higher than single-layer In 2 O 3 and ZnO devices by a factor of 2 to 100. This marked improvement is shown to originate from the presence of free electrons confined on the plane of the atomically sharp heterointerface induced by the large conduction band offset between In 2 O 3 and ZnO. Our finding underscores engineering of solution-grown metal oxide heterointerfaces as an alternative strategy to thin-film transistor development and has the potential for widespread technological applications.

  14. Heterojunction oxide thin-film transistors with unprecedented electron mobility grown from solution

    PubMed Central

    Faber, Hendrik; Das, Satyajit; Lin, Yen-Hung; Pliatsikas, Nikos; Zhao, Kui; Kehagias, Thomas; Dimitrakopulos, George; Amassian, Aram; Patsalas, Panos A.; Anthopoulos, Thomas D.

    2017-01-01

    Thin-film transistors made of solution-processed metal oxide semiconductors hold great promise for application in the emerging sector of large-area electronics. However, further advancement of the technology is hindered by limitations associated with the extrinsic electron transport properties of the often defect-prone oxides. We overcome this limitation by replacing the single-layer semiconductor channel with a low-dimensional, solution-grown In2O3/ZnO heterojunction. We find that In2O3/ZnO transistors exhibit band-like electron transport, with mobility values significantly higher than single-layer In2O3 and ZnO devices by a factor of 2 to 100. This marked improvement is shown to originate from the presence of free electrons confined on the plane of the atomically sharp heterointerface induced by the large conduction band offset between In2O3 and ZnO. Our finding underscores engineering of solution-grown metal oxide heterointerfaces as an alternative strategy to thin-film transistor development and has the potential for widespread technological applications. PMID:28435867

  15. Possibility of H2O2 decomposition in thin liquid films on Mars

    NASA Astrophysics Data System (ADS)

    Kereszturi, Akos; Gobi, Sandor

    2014-11-01

    In this work the pathways and possibilities of H2O2 decomposition on Mars in microscopic liquid interfacial water were analyzed by kinetic calculations. Thermal and photochemical driven decomposition, just like processes catalyzed by various metal oxides, is too slow compared to the annual duration while such microscopic liquid layers exist on Mars today, to produce substantial decomposition. The most effective analyzed process is catalyzed by Fe ions, which could decompose H2O2 under pH<4.5 with a half life of 1-2 days. This process might be important during volcanically influenced periods when sulfur release produces acidic pH, and rotational axis tilt change driven climatic changes also influence the volatile circulation and spatial occurrence just like the duration of thin liquid layer. Under current conditions, using the value of 200 K as the temperature in interfacial water (at the southern hemisphere), and applying Phoenix lander's wet chemistry laboratory results, the pH is not favorable for Fe mobility and this kind of decomposition. Despite current conditions (especially pH) being unfavorable for H2O2 decomposition, microscopic scale interfacial liquid water still might support the process. By the reaction called heterogeneous catalysis, without acidic pH and mobile Fe, but with minerals surfaces containing Fe decomposition of H2O2 with half life of 20 days can happen. This duration is still longer but not several orders than the existence of springtime interfacial liquid water on Mars today. This estimation is relevant for activation energy controlled reaction rates. The other main parameter that may influence the reaction rate is the diffusion speed. Although the available tests and theoretical calculations do not provide firm values for the diffusion speed in such a “2-dimensional” environment, using relevant estimations this parameter in the interfacial liquid layer is smaller than in bulk water. But the 20 days' duration mentioned above is still

  16. H2O2/TiO2 photocatalytic oxidation of metol. Identification of intermediates and reaction pathways.

    PubMed

    Aceituno, Mónica; Stalikas, Constantine D; Lunar, Loreto; Rubio, Soledad; Pérez-Bendito, Dolores

    2002-08-01

    The applicability of H2O2 to increase the efficiency of TiO2 photocatalytic degradations was investigated. The photographic developer metol [N-methyl-p-aminophenol] that does not adsorb on the surface of TiO2 particulates was used as a model for this purpose. It was proved that metol was mineralised under oxidation with H2O2/TiO2/UV through different thermal and photochemical reactions. Identification of intermediates by both HPLC-electron impact-MS and HPLC-electrospray ionisation-MS helped to elucidate the role of H2O2 and TiO2 in the degradation process and to establish degradation pathways. Intermediates yielded were partially oxygenated aromatic species and dimers, which were amenable to oxidation. The optimal degradation conditions found for mineralisation were 0.4 M H2O2, 5 mg/ml TiO2, pH 9 and irradiation centred at 360 nm (4.9 mW/cm2). The use of oxidants opens an interesting medium to the treatment of effluents containing a diversity of organics since they increase substantially the efficiency of TiO2 photocatalytic degradations.

  17. Structural and electrical transport properties of La2Mo2O9 thin films prepared by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Paul, T.; Ghosh, A.

    2017-04-01

    We have studied the structure and electrical properties of La2Mo2O9 thin films of different thicknesses prepared by the laser deposition technique at different substrate temperatures. The structural properties of the thin films have been investigated using XRD, XPS, AFM, TEM, SEM, and Raman spectroscopy. The electrical transport properties of the thin films have been investigated in wide temperature and frequency ranges. The cubic nature of the thin films has been confirmed from structural analysis. An enhancement of the oxygen ion conductivity of the films up to five orders of magnitude is obtained compared to that of the bulk La2Mo2O9, suggesting usefulness of the thin films as electrolytes in micro-solid oxide fuel cells. The enhanced dc ionic conductivity of the thin films has been interpreted using the rule of the mixture model, while a power law model has been used to investigate the frequency and temperature dependences of the conductivity. The analysis of the results predicts the three-dimensional oxygen ion conduction in the thin films.

  18. Influences of Indium Tin Oxide Layer on the Properties of RF Magnetron-Sputtered (BaSr)TiO3 Thin Films on Indium Tin Oxide-Coated Glass Substrate

    NASA Astrophysics Data System (ADS)

    Kim, Tae Song; Oh, Myung Hwan; Kim, Chong Hee

    1993-06-01

    Nearly stoichiometric ((Ba+Sr)/Ti=1.08-1.09) and optically transparent (BaSr)TiO3 thin films were deposited on an indium tin oxide (ITO)-coated glass substrate by means of rf magnetron sputtering for their application to the insulating layer of an electroluminescent flat panel display. The influence of the ITO layer on the properties of (BaSr)TiO3 thin films deposited on the ITO-coated substrate was investigated. The ITO layer did not affect the crystallographic orientation of (BaSr)TiO3 thin film, but enhanced the grain growth. Another effect of the ITO layer on (BaSr)TiO3 thin films was the interdiffusion phenomenon, which was studied by means of secondary ion mass spectrometry (SIMS). As the substrate temperature increased, interdiffusion intensified at the interface not only between the grown film and ITO layer but also between the ITO layer and base glass substrate. The refractive index (nf) of (BaSr)TiO3 thin film deposited on a bare glass substrate was 2.138-2.286, as a function of substrate temperature.

  19. Vacancy defects and optoelectrical properties for fluorine tin oxide thin films with various SnF2 contents

    NASA Astrophysics Data System (ADS)

    Zhou, Yawei; Xu, Wenwu; Li, Jingjing; Yin, Chongshan; Liu, Yong; Zhao, Bin; Chen, Zhiquan; He, Chunqing; Mao, Wenfeng; Ito, Kenji

    2018-01-01

    Fluorine doped tin oxide (FTO) thin films were deposited on glass substrates by e-beam evaporation. Much higher carrier concentration, broader optical band gap, and average transmittance over 80% were obtained with SnF2 doped SnO2 thin films. Positron annihilation results showed that there are two kinds of vacancy clusters with different sizes existing in the annealed FTO thin films, and the concentration of the larger vacancy clusters of VSnO in the thin films increases with increasing SnF2 contents. Meanwhile, photoluminescence spectra results indicated that the better electrical and optical properties of the FTO thin films are attributed to FO substitutions and oxygen vacancies with higher concentration, which are supported by positron annihilation Doppler broadening results and confirmed by X-ray photoelectron spectroscopy. The results showed that widening of the optical band gap of the FTO thin films strongly depends on the carrier concentration, which is interpreted for the Burstein-Moss effect and is associated with the formation of FO and oxygen vacancies with increasing SnF2 content.

  20. Origin of Active Oxygen in a Ternary CuO x /Co 3O 4–CeO 2 Catalyst for CO Oxidation

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Liu, Zhigang; Wu, Zili; Peng, Xihong

    2014-11-14

    In this paper, we have studied CO oxidation over a ternary CuO x/Co 3O 4-CeO 2 catalyst and employed the techniques of N 2 adsorption/desporption, XRD, TPR, TEM, in situ DRIFTS and QMS (Quadrupole mass spectrometer) to explore the origin of active oxygen. DRIFTS-QMS results with labeled 18O2 indicate that the origin of active oxygens in CuO x/Co 3O 4-CeO 2 obeys a model, called as queue mechanism. Namely gas-phase molecular oxygens are dissociated to atomic oxygens and then incorporate in oxygen vacancies located at the interface of Co 3O 4-CeO 2 to form active crystalline oxygens, and these activemore » oxygens diffuse to the CO-Cu + sites thanks to the oxygen vacancy concentration magnitude and react with the activated CO to form CO 2. This process, obeying a queue rule, provides active oxygens to form CO 2 from gas-phase O 2 via oxygen vacancies and crystalline oxygen at the interface of Co 3O 4-CeO 2.« less

  1. Influence of thermal treatment temperature on high-performance varistors prepared by hot-dipping tin oxide thin films in Nb2O5 powder

    NASA Astrophysics Data System (ADS)

    Wang, Qi; Peng, Zhijian; Wang, Yang; Fu, Xiuli

    2018-06-01

    SnOx-Nb2O5 thin film varistors were prepared by hot-dipping oxygen-deficient tin oxide films in Nb2O5 powder in air, and the influence of hot-dipping temperature (HDT) on the varistor performance of the samples was systematically explored. When the HDT increased from 300 to 700 °C, the nonlinear coefficient of the samples raised first and then dropped down, reaching the maximum of 14.73 at 500 °C, and the breakdown electric field exhibited a similar variation trend, gaining the peak value of 0.0201 V/nm at this temperature. Correspondingly, the leakage current decreased first and then increased with increasing HDT, reaching the minimum of 17.1 mA/cm2 at 500 °C. Besides, it was proposed that a grain-boundary defect barrier model was responsible for the nonlinear behavior of the obtained SnOx-Nb2O5 film varistors. This high-performance thin film varistor with nanoscaled thickness might be much promising in nano-devices or devices working in low voltage.

  2. Thin-film transistors with a graphene oxide nanocomposite channel.

    PubMed

    Jilani, S Mahaboob; Gamot, Tanesh D; Banerji, P

    2012-12-04

    Graphene oxide (GO) and graphene oxide-zinc oxide nanocomposites (GO-ZnO) were used as channel materials on SiO(2)/Si to fabricate thin-film transistors (TFT) with an aluminum source and drain. Pure GO-based TFT showed poor field-effect characteristics. However, GO-ZnO-nanocomposite-based TFT showed better field-effect performance because of the anchoring of ZnO nanostructures in the GO matrix, which causes a partial reduction in GO as is found from X-ray photoelectron spectroscopic data. The field-effect mobility of charge carriers at a drain voltage of 1 V was found to be 1.94 cm(2)/(V s). The transport of charge carriers in GO-ZnO was explained by a fluctuation-induced tunneling mechanism.

  3. In situ oxidation studies on /001/ copper-nickel alloy thin films

    NASA Technical Reports Server (NTRS)

    Heinemann, K.; Rao, D. B.; Douglass, D. L.

    1977-01-01

    High-resolution transmission electron microscopy studies are reported of (001)-oriented single crystalline thin films of Cu-3%Ni, Cu-4.6%Ni, and Cu-50%Ni alloy which were prepared by vapor deposition onto (001) NaCl substrates and subsequently annealed at around 1100 K and oxidized at 725 K at low oxygen partial pressure. At all alloy concentrations, Cu2O and NiO nucleated and grew independently without the formation of mixed oxides. The shape and growth rates of Cu2O nuclei were similar to rates found earlier. For low-nickel alloy concentrations, the NiO nuclei were larger and the number density of NiO was less than that of Cu-50%Ni films for which the shape and growth rates of NiO were identical to those for pure nickel films. Phenomena involving a reduced induction period, surface precipitation, and through-thickness growth are also described. The results are consistent with previously established oxidation mechanisms for pure copper and pure nickel films.

  4. Interface Properties of Atomic-Layer-Deposited Al2O3 Thin Films on Ultraviolet/Ozone-Treated Multilayer MoS2 Crystals.

    PubMed

    Park, Seonyoung; Kim, Seong Yeoul; Choi, Yura; Kim, Myungjun; Shin, Hyunjung; Kim, Jiyoung; Choi, Woong

    2016-05-11

    We report the interface properties of atomic-layer-deposited Al2O3 thin films on ultraviolet/ozone (UV/O3)-treated multilayer MoS2 crystals. The formation of S-O bonds on MoS2 after low-power UV/O3 treatment increased the surface energy, allowing the subsequent deposition of uniform Al2O3 thin films. The capacitance-voltage measurement of Au-Al2O3-MoS2 metal oxide semiconductor capacitors indicated n-type MoS2 with an electron density of ∼10(17) cm(-3) and a minimum interface trap density of ∼10(11) cm(-2) eV(-1). These results demonstrate the possibility of forming a high-quality Al2O3-MoS2 interface by proper UV/O3 treatment, providing important implications for their integration into field-effect transistors.

  5. Cation disorder and gas phase equilibrium in an YBa 2Cu 3O 7- x superconducting thin film

    NASA Astrophysics Data System (ADS)

    Shin, Dong Chan; Ki Park, Yong; Park, Jong-Chul; Kang, Suk-Joong L.; Yong Yoon, Duk

    1997-02-01

    YBa 2Cu 3O 7- x superconducting thin films have been grown by in situ off-axis rf sputtering with varying oxygen pressure, Ba/Y ratio in a target, and deposition temperature. With decreasing oxygen pressure, increasing Ba/Y ratio, increasing deposition temperature, the critical temperature of the thin films decreased and the c-axis length increased. The property change of films with the variation of deposition variables has been explained by a gas phase equilibrium of the oxidation reaction of Ba and Y. Applying Le Chatelier's principle to the oxidation reaction, we were able to predict the relation of deposition variables and the resultant properties of thin films; the prediction was in good agreement with the experimental results. From the relation between the three deposition variables and gas phase equilibrium, a 3-dimensional processing diagram was introduced. This diagram has shown that the optimum deposition condition of YBa 2Cu 3O 7- x thin films is not a fixed point but can be varied. The gas phase equilibrium can also be applied to the explanation of previous results that good quality films were obtained at low deposition temperature using active species, such as O, O 3, and O 2+.

  6. Study of structure and properties of oxide electrode materials (Fe3O4, AZO, SRO) and their device applications

    NASA Astrophysics Data System (ADS)

    Olga, Chichvarina

    Ferroelectric thin film capacitor heterostructures have attracted considerable attention in the last decade because of their potential applications in piezoelectric sensors, actuators, power generators and non-volatile memory devices. Strongly correlated all-perovskite oxide heterojunctions are of a particular interest, as their material properties (electronic, structural, magnetic and optical, etc.) can be tuned via doping, interface effect, applied electrical field, and formation of two-dimensional electron gas (2DEG), etc. The right selection of electrode material for this type of capacitor-like structures may modify and enhance the performance of a device, as the electrode/barrier layer interfaces can significantly influence its macroscopic properties. Although there is a number of reports on the effect of electrode interfaces on the properties of PZT capacitors deposited on SRO buffered STO substrate, very little is known about Fe3O4/PZT and AZO/PZT electrode interfaces. This thesis comprises two parts. In the first part we present a systematic study of the structural, transport, magnetic and optical properties of oxide thin films: AZO, Fe3O4 and SRO. These monolayers were fabricated via pulsed laser deposition technique on quartz, MgO and STO substrates respectively. The second part of this thesis elucidates the behaviour of these three oxides as electrode components in PZT/SRO/STO heteroepitaxial structures. The highlights of the work are summarized below: 1) Zinc-blende (ZB) phase of ZnO was predicted to possess higher values of conductivity and higher doping efficiency compared to its wurzite counterpart and thus has greater chances of facilitating the fabrication of ZnO-electrode-based devices. However, zinc-blende is a metastable phase, and it is challenging to obtain single-phase ZB. To tackle this challenge we tuned parameters such-as film thickness, substrate and annealing effect, and achieved a ZB phase of Ti-doped ZnO, ZB-(Zn1-xTix)O thin film. An

  7. Cation vacancies and electrical compensation in Sb-doped thin-film SnO2 and ZnO

    NASA Astrophysics Data System (ADS)

    Korhonen, E.; Prozheeva, V.; Tuomisto, F.; Bierwagen, O.; Speck, J. S.; White, M. E.; Galazka, Z.; Liu, H.; Izyumskaya, N.; Avrutin, V.; Özgür, Ü.; Morkoç, H.

    2015-02-01

    We present positron annihilation results on Sb-doped SnO2 and ZnO thin films. The vacancy types and the effect of vacancies on the electrical properties of these intrinsically n-type transparent semiconducting oxides are studied. We find that in both materials low and moderate Sb-doping leads to formation of vacancy clusters of variable sizes. However, at high doping levels cation vacancy defects dominate the positron annihilation signal. These defects, when at sufficient concentrations, can efficiently compensate the n-type doping produced by Sb. This is the case in ZnO, but in SnO2 the concentrations appear too low to cause significant compensation.

  8. Complex oxide thin films for microelectronics

    NASA Astrophysics Data System (ADS)

    Suvorova, Natalya

    The rapid scaling of the device dimensions, namely in metal oxide semiconductor field effect transistor (MOSFET), is reaching its fundamental limit which includes the increase in allowable leakage current due to direct tunneling with decrease of physical thickness of SiO2 gate dielectric. The significantly higher relative dielectric constant (in the range 9--25) of the gate dielectric beyond the 3.9 value of silicon dioxide will allow increasing the physical thickness. Among the choices for the high dielectric constant (K) materials for future generation MOSFET application, barium strontium titanate (BST) and strontium titanate (STO) possess one of the highest attainable K values making them the promising candidates for alternative gate oxide. However, the gate stack engineering does not imply the simple replacement of the SiO2 with the new dielectric. Several requirements should be met for successful integration of a new material. The major one is a production of high level of interface states (Dit) compared to that of SiO 2 on Si. An insertion of a thin SiO2 layer prior the growth of high-K thin film is a simple solution that helps to limit reaction with Si substrate and attains a high quality interface. However, the combination of two thin films reduces the overall K of the dielectric stack. An optimization of the SiO2 underlayer in order to maintain the interface quality yet minimize the effect on K is the focus of this work. The results from our study are presented with emphasis on the key process parameters that improve the dielectric film stack. For in-situ growth characterization of BST and STO films sputter deposited on thermally oxidized Si substrates spectroscopic ellipsometry in combination with time of flight ion scattering and recoil spectrometry have been employed. Studies of material properties have been complemented with analytical electron microscopy. To evaluate the interface quality the electrical characterization has been employed using

  9. Effect of Al2O3 insulator thickness on the structural integrity of amorphous indium-gallium-zinc-oxide based thin film transistors.

    PubMed

    Kim, Hak-Jun; Hwang, In-Ju; Kim, Youn-Jea

    2014-12-01

    The current transparent oxide semiconductors (TOSs) technology provides flexibility and high performance. In this study, multi-stack nano-layers of TOSs were designed for three-dimensional analysis of amorphous indium-gallium-zinc-oxide (a-IGZO) based thin film transistors (TFTs). In particular, the effects of torsional and compressive stresses on the nano-sized active layers such as the a-IGZO layer were investigated. Numerical simulations were carried out to investigate the structural integrity of a-IGZO based TFTs with three different thicknesses of the aluminum oxide (Al2O3) insulator (δ = 10, 20, and 30 nm), respectively, using a commercial code, COMSOL Multiphysics. The results are graphically depicted for operating conditions.

  10. Synthesis and electronic properties of Fe2TiO5 epitaxial thin films

    NASA Astrophysics Data System (ADS)

    Osada, Motoki; Nishio, Kazunori; Hwang, Harold Y.; Hikita, Yasuyuki

    2018-05-01

    We investigate the growth phase diagram of pseudobrookite Fe2TiO5 epitaxial thin films on LaAlO3 (001) substrates using pulsed laser deposition. Control of the oxygen partial pressure and temperature during deposition enabled selective stabilization of (100)- and (230)-oriented films. In this regime, we find an optical gap of 2.1 eV and room temperature resistivity in the range of 20-80 Ω cm, which are significantly lower than α-Fe2O3, making Fe2TiO5 potentially an ideal inexpensive visible-light harvesting semiconductor. These results provide a basis to incorporate Fe2TiO5 in oxide heterostructures for photocatalytic and photoelectrochemical applications.

  11. Electrical transport properties of spray deposited transparent conducting ortho-Zn2SnO4 thin films

    NASA Astrophysics Data System (ADS)

    Ramarajan, R.; Thangaraju, K.; Babu, R. Ramesh; Joseph, D. Paul

    2018-04-01

    Ortho Zinc Stannate (Zn2SnO4) exhibits excellent electrical and optical properties to serve as alternate transparent electrode in optoelectronic devices. Here we have optimized ortho-Zn2SnO4 thin film by spray pyrolysis method. Deposition was done onto a pre-heated glass substrate at a temperature of 400 °C. The XRD pattern indicated films to be polycrystalline with cubic structure. The surface of films had globular and twisted metal sheet like morphologies. Films were transparent in the visible region with band gap around 3.6 eV. Transport properties were studied by Hall measurements at 300 K. Activation energies were calculated from Arrhenius's plot from temperature dependent electrical measurements and the conduction mechanism is discussed.

  12. Hydrothermal Syntheses and Structures of Three-Dimensional Oxo-fluorovanadium Phosphates: [H 2N(C 2H 4) 2NH 2] 0.5[(VO) 4V(HPO 4) 2(PO 4) 2F 2(H 2O) 4] · 2H 2O and K 2[(VO) 3(PO 4) 2F 2(H 2O)] · H 2O

    NASA Astrophysics Data System (ADS)

    Bonavia, Grant; Haushalter, R. C.; Zubieta, Jon

    1996-11-01

    The hydrothermal reactions of FPO3H2with vanadium oxides result in the incorporation of fluoride into V-P-O frameworks as a consequence of metal-mediated hydrolysis of the fluorophosphoric acid to produce F-and PO3-4. By exploiting this convenient source of F-, two 3-dimensional oxo-fluorovanadium phosphate phases were isolated, [H2N(C2H4)2NH2]0.5[(VO)4V(HOP4)2(PO4)2F2(H2O)4) · 2H2O (1 · 2H2O) and K2[(VO)3(PO4)2F2(H2O)] · H2O (2 · H2O). Both anionic frameworks contain (VIVO)-F--phosphate layers, with confacial bioctahedral {(VIVO)2FO6} units as the fundamental motif. In the case of 1, the layers are linked through {VIIIO6} octahedra, while for 2 the interlayer connectivity is provided by edge-sharing {(VIVO)2F2O6} units. Crystal data are 1 · 2H2O, CH10FN0.5O13P2V2.5, monoclinicC2/m,a= 18.425(4) Å,c= 8.954(2) Å, β = 93.69(2)0,V= 1221.1(4) Å3,Z= 4,Dcalc= 2.423 g cm-3; 2 · H2O, H4F2K2O13P2V3, triclinicPoverline1,a= 7.298(1) Å,b= 8.929(2) Å,c = 10.090(2) Å, α = 104.50(2)0, β = 100.39(2)0, δ = 92.13(2)0,V= 623.8(3) Å3,Z= 2,Dcalc= 2.891 g cm-3.

  13. One-pot fabrication of NiFe2O4 nanoparticles on α-Ni(OH)2 nanosheet for enhanced water oxidation

    NASA Astrophysics Data System (ADS)

    Chen, Hong; Yan, Junqing; Wu, Huan; Zhang, Yunxia; Liu, Shengzhong (Frank)

    2016-08-01

    Water splitting has been intensively investigated as a promising solution to resolve the future environmental and energy crises. The oxygen evolution reaction (OER) of the photo- and electric field-induced water splitting limits the development of other reactions, including hydrogen evolution reaction (HER). Fe, Ni and NiFe (hydro) oxide-based catalysts are generally acknowledged among the best candidates of OER catalysts for water splitting. Herein, we developed a one-pot simple hydrothermal process to assemble NiFe2O4 nanoparticles onto the α-Ni(OH)2 nanosheets. The first formed NiFe2O4 under high temperature and pressure environment induces and assists the α-Ni(OH)2 formation without any further additives, because the distance between the neighboring Ni atoms in the cubic NiFe2O4 is similar to that in the α-Ni(OH)2 {003} facets. We have synthesized a series of NiFe2O4/α-Ni(OH)2 compounds and find that the overpotential decreases with the increase of Ni(OH)2 content while the OER kinetics stays unchanged, suggesting that Ni(OH)2 plays a major role in overpotential while NiFe2O4 mainly affects the OER kinetics. The obtained NiFe2O4/α-Ni(OH)2 compounds is also found to be a promising co-catalyst for the photocatalytic water oxidation. In fact, it is even more active than the noble PtOx with acceptable stability for the oxygen generation.

  14. Selectivity shifting behavior of Pd nanoparticles loaded zinc stannate/zinc oxide (Zn2SnO4/ZnO) nanowires sensors

    NASA Astrophysics Data System (ADS)

    Arafat, M. M.; Ong, J. Y.; Haseeb, A. S. M. A.

    2018-03-01

    In this research, the gas sensing behavior of Pd nanoparticles loaded zinc stannate/zinc oxide (Zn2SnO4/ZnO) nanowires were investigated. The Zn2SnO4/ZnO nanowires were grown on Au interdigitated alumina substrate by carbon assisted thermal evaporation process. Pd nanoparticles were loaded on the Zn2SnO4/ZnO nanowires by wet reduction process. The nanowires were characterized by X-ray diffractometer, field emission scanning electron microscope and energy dispersive X-ray spectroscope. The Zn2SnO4/ZnO and Pd nanoparticles loaded Zn2SnO4/ZnO nanowires were investigated for detecting H2, H2S and C2H5OH gases in N2 background. Results revealed that the average diameter and length of as-grown Zn2SnO4/ZnO nanowires were 74 nm and 30 μm, respectively. During wet reduction process,Pd particles having size of 20-60 nm were evenly distributed on the Zn2SnO4/ZnO nanowires. The Zn2SnO4/ZnO nanowires based sensors showed selective response towards C2H5OH whereas Pd nanoparticles loaded Zn2SnO4/ZnO nanowires showed selective response towards H2. The recovery time of the sensors reduced with Pd loading on Zn2SnO4/ZnO nanowires. A mechanism is proposed to elucidate the gas sensing mechanism of Pd nanoparticles loaded Zn2SnO4/ZnO nanowires.

  15. Manipulation of ZnO composition affecting electrical properties of MEH-PPV: ZnO nanocomposite thin film via spin coating for OLEDs application

    NASA Astrophysics Data System (ADS)

    Azhar, N. E. A.; Shariffudin, S. S.; Alrokayan, Salman A. H.; Khan, Haseeb A.; Rusop, M.

    2018-05-01

    Recent investigations of the promising materials for optoelectronic have been demonstrated by introducing n-type inorganic material into conjugated polymer. Morphology, optical and electrical of nanocomposites thin films based on poly[2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) and zinc oxide (ZnO) nanotetrapods with various ZnO composition (0 wt% to 0.4 wt%) have been investigated. The MEH-PPV: ZnO nanocomposite thin film was deposited using spin-coating method. Surface morphology was characterized using field emission scanning electron microscopy and shows the uniform dispersion of MEH-PPV and ZnO phases for sample deposited at 0.2 wt%. The photoluminescence (PL) spectra shows the visible emission intensities increased when the ZnO composition increased. The current-voltage (I-V) measurement shows the highest conductivity of nanocomposite thin film deposited at 0.2 wt% of ZnO is 7.40 × 10-1 S. cm-1. This study will provide better performance and suitable for optoelectronic device especially OLEDs application.

  16. Interfacial characteristics and multiferroic properties of ion-doped BiFeO3/NiFe2O4 thin films

    NASA Astrophysics Data System (ADS)

    Guo, Meiyou; Tan, Guoqiang; Zheng, Yujuan; Liu, Wenlong; Ren, Huijun; Xia, Ao

    2017-05-01

    Multi-ion doped BiFeO3/NiFe2O4 bilayered thin films were successfully prepared on fluorine-doped SnO2/glass (SnO2:F) substrates by sol-gel method. The crystalline structure, leakage current, interfacial characteristics, and multiferroic properties were investigated in detail. The results of Rietveld refinement showed that the structure of BSrSFMC layer is transformed from rhombohedral to tetragonal structure by the means of ion-doping. The difference of leakage current density of the BSrSFMC/NiFe2O4 (NFO) bilayered films of the -40 V to 40 V and 40 V to -40 V are 0.32 × 10-5 and 1.13 × 10-5 A/cm2, respectively. It was observed that there are obvious interface effects between BSrSFMC and NFO layers, which will cause the accumulation of space charges and the establishment of built-in internal electric field (EI) at the interface. Therefore, different EI directions will affect the dipoles reversal and migration of carriers in the BSrSFMC layer, which will result in different values of transient current with the same applied voltage in the opposite directions. The larger coercive field (Ec ˜ 750 kV/cm) of BSrSFMC/NFO film indicated that there is a tensile stress at the interface between BSrSFMC and NFO layers, making the polarization difficult. These results showed that the above interesting phenomena of the J-V are closely related to the interface effects between the layer of BiFeO3 and NiFe2O4.

  17. Drying Temperature Dependence of Sol-gel Spin Coated Bilayer Composite ZnO/TiO2 Thin Films for Extended Gate Field Effect Transistor pH Sensor

    NASA Astrophysics Data System (ADS)

    Rahman, R. A.; Zulkefle, M. A.; Yusoff, K. A.; Abdullah, W. F. H.; Rusop, M.; Herman, S. H.

    2018-03-01

    This study presents an investigation on zinc oxide (ZnO) and titanium dioxide (TiO2) bilayer film applied as the sensing membrane for extended-gate field effect transistor (EGFET) for pH sensing application. The influences of the drying temperatures on the pH sensing capability of ZnO/TiO2 were investigated. The sensing performance of the thin films were measured by connecting the thin film to a commercial MOSFET to form the extended gates. By varying the drying temperature, we found that the ZnO/TiO2 thin film dried at 150°C gave the highest sensitivity compared to other drying conditions, with the sensitivity value of 48.80 mV/pH.

  18. Effect of external magnetic field on the crystal growth of nano-structured Zn xMn 1- x+ yZr yFe 2-2 yO 4 thin films

    NASA Astrophysics Data System (ADS)

    Anjum, Safia; Rafique, M. S.; Khaleeq-ur-Rahaman, M.; Siraj, K.; Usman, Arslan; Ahsan, A.; Naseem, S.; Khan, K.

    2011-06-01

    Zn 0.2Mn 0.81Zr 0.01Fe 1.98O 4 and Zn 0.2Mn 0.83Zr 0.03Fe 1.94O 4 thin films with different concentrations of Mn and Zr have been deposited on single crystal n-Si (400) at room temperature (RT) by pulse laser deposition technique (PLD). The films have been deposited under two conditions: (i) with the applied external magnetic field across the propagation of the plume (ii) without applied external magnetic field ( B=0). XRD results show the films have spinel cubic structure when deposited in the presence of magnetic field. SEM and AFM observations clearly show the effect of external applied magnetic field on the growth of films in terms of small particle size, improved uniformity and lower r.m.s. roughness. Thin films deposited under the influence of external magnetic field exhibit higher magnetization as measured by the VSM. The optical band gap energy Eg, refractive index n, reflection, absorption and the thickness of the thin films were measured by spectroscopy ellipsometer. The reflection of Zn 0.2Mn 0.83Zr 0.03Fe 1.94O 4 thin films is higher than Zn 0.2Mn 0.81Zr 0.01Fe 1.98O 4 thin films due to the greater concentration of Zr. The thicknesses of the thin films under the influence of external magnetic field are larger than the films grown without field for both samples. The optical band gap energy Eg decreases with increasing film thickness. The films with external magnetic field are found highly absorbing in nature due to the larger film thickness.

  19. Ultraviolet emission enhancement in ZnO thin films modified by nanocrystalline TiO2

    NASA Astrophysics Data System (ADS)

    Zheng, Gaige; Lu, Xi; Qian, Liming; Xian, Fenglin

    2017-05-01

    In this study, nanocrystalline TiO2 modified ZnO thin films were prepared by electron beam evaporation. The structural, morphological and optical properties of the samples were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), UV-visible spectroscopy, fluorescence spectroscopy, respectively. The composition of the films was examined by energy dispersive X-ray spectroscopy (EDX). The photoluminescent spectrum shows that the pure ZnO thin film exhibits an ultraviolet (UV) emission peak and a strong green emission band. Surface analysis indicates that the ZnO thin film contains many oxygen vacancy defects on the surface. After the ZnO thin film is modified by the nanocrystalline TiO2 layer, the UV emission of ZnO is largely enhanced and the green emission is greatly suppressed, which suggests that the surface defects such as oxygen vacancies are passivated by the TiO2 capping layer. As for the UV emission enhancement of the ZnO thin film, the optimized thickness of the TiO2 capping layer is ∼16 nm. When the thickness is larger than 16 nm, the UV emission of the ZnO thin film will decrease because the TiO2 capping layer absorbs most of the excitation energy. The UV emission enhancement in the nanocrystalline TiO2 modified ZnO thin film can be attributed to surface passivation and flat band effect.

  20. Near-ambient pressure XPS of high-temperature surface chemistry in Sr2Co2O5 thin films

    DOE PAGES

    Hong, Wesley T.; Stoerzinger, Kelsey; Crumlin, Ethan J.; ...

    2016-02-11

    Transition metal perovskite oxides are promising electrocatalysts for the oxygen reduction reaction (ORR) in fuel cells, but a lack of fundamental understanding of oxide surfaces impedes the rational design of novel catalysts with improved device efficiencies. In particular, understanding the surface chemistry of oxides is essential for controlling both catalytic activity and long-term stability. Thus, elucidating the physical nature of species on perovskite surfaces and their catalytic enhancement would generate new insights in developing oxide electrocatalysts. In this article, we perform near-ambient pressure XPS of model brownmillerite Sr 2Co 2O 5 (SCO) epitaxial thin films with different crystallographic orientations. Detailedmore » analysis of the Co 2p spectra suggests that the films lose oxygen as a function of temperature. Moreover, deconvolution of the O 1s spectra shows distinct behavior for (114)-oriented SCO films compared to (001)-oriented SCO films, where an additional bulk oxygen species is observed. These findings indicate a change to a perovskite-like oxygen chemistry that occurs more easily in (114) SCO than (001) SCO, likely due to the orientation of oxygen vacancy channels out-of-plane with respect to the film surface. This difference in surface chemistry is responsible for the anisotropy of the oxygen surface exchange coefficient of SCO and may contribute to the enhanced ORR kinetics of La 0.8Sr 0.2CoO 3-δ thin films by SCO surface particles observed previously.« less

  1. Strain tuning of electronic structure in Bi 4Ti 3O 12-LaCoO 3 epitaxial thin films

    DOE PAGES

    Choi, Woo Seok; Lee, Ho Nyung

    2015-05-08

    In this study, we investigated the crystal and electronic structures of ferroelectric Bi 4Ti 3O 12 single-crystalline thin films site-specifically substituted with LaCoO 3 (LCO). The epitaxial films were grown by pulsed laser epitaxy on NdGaO 3 and SrTiO 3 substrates to vary the degree of strain. With increasing the LCO substitution, we observed a systematic increase in the c-axis lattice constant of the Aurivillius phase related with the modification of pseudo-orthorhombic unit cells. These compositional and structural changes resulted in a systematic decrease in the band gap, i.e., the optical transition energy between the oxygen 2p and transition-metal 3dmore » states, based on a spectroscopic ellipsometry study. In particular, the Co 3d state seems to largely overlap with the Ti t 2g state, decreasing the band gap. Interestingly, the applied tensile strain facilitates the band-gap narrowing, demonstrating that epitaxial strain is a useful tool to tune the electronic structure of ferroelectric transition-metal oxides.« less

  2. Study on the treatment of 2-sec-butyl-4,6-dinitrophenol (DNBP) wastewater by ClO2 in the presence of aluminum oxide as catalyst.

    PubMed

    Wang, Hui-Long; Dong, Jing; Jiang, Wen-Feng

    2010-11-15

    The chlorine dioxide (ClO(2)) oxidative degradation of 2-sec-butyl-4,6-dinitrophenol (DNBP) in aqueous solution was studied in detail using Al(2)O(3) as a heterogeneous catalyst. The operating parameters such as the ClO(2) concentration, catalyst dosage, initial DNBP concentration, reaction time and pH were evaluated. Compared with the conventional ClO(2) oxidation process without the catalyst, the ClO(2) catalytic oxidation system could significantly enhance the degradation efficiency. Under the optimal condition (DNBP concentration 39 mg L(-1), ClO(2) concentration 0.355 g L(-1), reaction time 60 min, catalyst dosage 10.7 g L(-1) and pH 4.66), degradation efficiency approached 99.1%. The catalyst was used at least 8 cycles without any appreciable loss of activity. The kinetic studies revealed that the ClO(2) catalytic oxidation degradation of DNBP followed pseudo-first-order kinetics with respect to DNBP concentration. The ClO(2) catalytic oxidation process was found to be very effective in the decolorization and COD(Cr) reduction of real wastewater from DNBP manufacturing. Thus, this study showed potential application of ClO(2) catalytic oxidation process in degradation of organic contaminants and industrial effluents. Copyright © 2010 Elsevier B.V. All rights reserved.

  3. The Cu2ZnSnSe4 thin films solar cells synthesized by electrodeposition route

    NASA Astrophysics Data System (ADS)

    Li, Ji; Ma, Tuteng; Wei, Ming; Liu, Weifeng; Jiang, Guoshun; Zhu, Changfei

    2012-06-01

    An electrodeposition route for preparing Cu2ZnSnSe4 thin films for thin film solar cell absorber layers is demonstrated. The Cu2ZnSnSe4 thin films are prepared by co-electrodeposition Cu-Zn-Sn metallic precursor and subsequently annealing in element selenium atmosphere. The structure, composition and optical properties of the films were investigated by X-ray diffraction (XRD), Raman spectrometry, energy dispersive spectrometry (EDS) and UV-VIS absorption spectroscopy. The Cu2ZnSnSe4 thin film with high crystalline quality was obtained, the band gap and absorption coefficient were 1.0 eV and 10-4 cm-1, which is quite suitable for solar cells fabrication. A solar cell with the structure of ZnO:Al/i-ZnO/CdS/Cu2ZnSnSe4/Mo/glass was fabricated and achieved an conversion efficiency of 1.7%.

  4. Study of nanoparticles TiO2 thin films on p-type silicon substrate using different alcoholic solvents

    NASA Astrophysics Data System (ADS)

    Muaz, A. K. M.; Hashim, U.; Arshad, M. K. Md.; Ruslinda, A. R.; Ayub, R. M.; Gopinath, Subash C. B.; Voon, C. H.; Liu, Wei-Wen; Foo, K. L.

    2016-07-01

    In this paper, sol-gel method spin coating technique is adopted to prepare nanoparticles titanium dioxide (TiO2) thin films. The prepared TiO2 sol was synthesized using titanium butoxide act as a precursor and subjected to deposited on the p-type silicon oxide (p-SiO2) and glass slide substrates under room temperature. The effect of different alcoholic solvents of methanol and ethanol on the structural, morphological, optical and electrical properties were systematically investigated. The coated TiO2 thin films were annealed in furnace at 773 K for 1 h. The structural properties of the TiO2 films were examined with X-ray Diffraction (XRD). From the XRD analysis, both solvents showing good crystallinity with anatase phase were the predominant structure. Atomic Force Microscopy (AFM) was employed to study the morphological of the thin films. The optical properties were investigated by Ultraviolet-visible (UV-Vis) spectroscopy were found that ethanol as a solvent give a higher optical transmittance if compare to the methanol solvent. The electrical properties of the nanoparticles TiO2 thin films were measured using two-point-probe technique.

  5. Nondestructive covalent functionalization of carbon nanotubes by selective oxidation of the original defects with K2FeO4

    NASA Astrophysics Data System (ADS)

    Zhang, Zhao-yang; Xu, Xue-cheng

    2015-08-01

    Chemical oxidation is still the major approach to the covalent functionalization of carbon nanotubes (CNTs). Theoretically, the defects on CNTs are more reactive than skeletal hexagons and should be preferentially oxidized, but conventional oxidation methods, e.g., HNO3/H2SO4 treatment, have poor reaction selectivity and inevitably consume the Cdbnd C bonds in the hexagonal lattices, leading to structural damage, π-electrons loss and weight decrease. In this work, we realized the nondestructive covalent functionalization of CNTs by selective oxidation of the defects. In our method, potassium ferrate K2FeVIO4 was employed as an oxidant for CNTs in H2SO4 medium. The CNT samples, before and after K2FeO4/H2SO4 treatment, were characterized with colloid dispersibility, IR, Raman spectroscopy, FESEM and XPS. The results indicated that (i) CNTs could be effectively oxidized by Fe (VI) under mild condition (60 °C, 3 h), and hydrophilic CNTs with abundant surface sbnd COOH groups were produced; and (ii) Fe (VI) oxidation of CNTs followed a defect-specific oxidation process, that is, only the sp3-hybridized carbon atoms on CNT surface were oxidized while the Cdbnd C bonds remained unaffected. This selective/nondestructive oxidation afforded oxidized CNTs in yields of above 100 wt%. This paper shows that K2FeO4/H2SO4 is an effective, nondestructive and green oxidation system for oxidative functionalization of CNTs and probably other carbon materials as well.

  6. Enhanced stability of solid oxide fuel cells by employing a modified cathode-interlayer interface with a dense La0.6Sr0.4Co0.2Fe0.8O3-δ thin film

    NASA Astrophysics Data System (ADS)

    De Vero, Jeffrey C.; Develos-Bagarinao, Katherine; Kishimoto, Haruo; Ishiyama, Tomohiro; Yamaji, Katsuhiko; Horita, Teruhisa; Yokokawa, Harumi

    2018-02-01

    In La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) cathode/Gd-doped ceria (GDC)/yttria-stabilized zirconia (YSZ)-electrolyte based solid oxide fuel cells (SOFCs), one of the key issues affecting performance and long-term stability is the apparent deactivation of LSCF cathode by the presence of secondary phases such as SrZrO3 at the interfaces. Herein, we report that by modifying the cathode-interlayer interface with a dense LSCF thin film, the severe cation interdiffusion is suppressed especially the fast gas or surface diffusion of Sr into adjacent GDC-interlayer/YSZ-electrolyte resulting in the significant reduction of SrZrO3 formation at the interfaces improving cell stability. In order to understand the present results, the interface chemistry is carefully considered and discussed. The results show that modification of cathode-interlayer interfaces is an important strategy for improving the lifetime of SOFCs.

  7. High performance cobalt-free Cu1.4Mn1.6O4 spinel oxide as an intermediate temperature solid oxide fuel cell cathode

    NASA Astrophysics Data System (ADS)

    Zhen, Shuying; Sun, Wang; Li, Peiqian; Tang, Guangze; Rooney, David; Sun, Kening; Ma, Xinxin

    2016-05-01

    In this work Cu1.4Mn1.6O4 (CMO) spinel oxide is prepared and evaluated as a novel cobalt-free cathode for intermediate temperature solid oxide fuel cells (IT-SOFCs). Single phase CMO powder with cubic structure is identified using XRD. XPS results confirm that mixed Cu+/Cu2+ and Mn3+/Mn4+ couples exist in the CMO sample, and a maximum conductivity of 78 S cm-1 is achieved at 800 °C. Meanwhile, CMO oxide shows good thermal and chemical compatibility with a 10 mol% Sc2O3 stabilized ZrO2 (ScSZ) electrolyte material. Impedance spectroscopy measurements reveals that CMO exhibits a low polarization resistance of 0.143 Ω cm2 at 800 °C. Furthermore, a Ni-ScSZ/ScSZ/CMO single cell demonstrates a maximum power density of 1076 mW cm-2 at 800 °C under H2 (3% H2O) as the fuel and ambient air as the oxidant. These results indicate that Cu1.4Mn1.6O4 is a superior and promising cathode material for IT-SOFCs.

  8. TiO2-graphene oxide nanocomposite as advanced photocatalytic materials.

    PubMed

    Stengl, Václav; Bakardjieva, Snejana; Grygar, Tomáš Matys; Bludská, Jana; Kormunda, Martin

    2013-02-27

    Graphene oxide composites with photocatalysts may exhibit better properties than pure photocatalysts via improvement of their textural and electronic properties. TiO2-Graphene Oxide (TiO2 - GO) nanocomposite was prepared by thermal hydrolysis of suspension with graphene oxide (GO) nanosheets and titania peroxo-complex. The characterization of graphene oxide nanosheets was provided by using an atomic force microscope and Raman spectroscopy. The prepared nanocomposites samples were characterized by Brunauer-Emmett-Teller surface area and Barrett-Joiner-Halenda porosity, X-ray Diffraction, Infrared Spectroscopy, Raman Spectroscopy and Transmission Electron Microscopy. UV/VIS diffuse reflectance spectroscopy was employed to estimate band-gap energies. From the TiO2 - GO samples, a 300 μm thin layer on a piece of glass 10×15 cm was created. The photocatalytic activity of the prepared layers was assessed from the kinetics of the photocatalytic degradation of butane in the gas phase. The best photocatalytic activity under UV was observed for sample denoted TiGO_100 (k = 0.03012 h-1), while sample labeled TiGO_075 (k = 0.00774 h-1) demonstrated the best activity under visible light.

  9. TiO2-graphene oxide nanocomposite as advanced photocatalytic materials

    PubMed Central

    2013-01-01

    Background Graphene oxide composites with photocatalysts may exhibit better properties than pure photocatalysts via improvement of their textural and electronic properties. Results TiO2-Graphene Oxide (TiO2 - GO) nanocomposite was prepared by thermal hydrolysis of suspension with graphene oxide (GO) nanosheets and titania peroxo-complex. The characterization of graphene oxide nanosheets was provided by using an atomic force microscope and Raman spectroscopy. The prepared nanocomposites samples were characterized by Brunauer–Emmett–Teller surface area and Barrett–Joiner–Halenda porosity, X-ray Diffraction, Infrared Spectroscopy, Raman Spectroscopy and Transmission Electron Microscopy. UV/VIS diffuse reflectance spectroscopy was employed to estimate band-gap energies. From the TiO2 - GO samples, a 300 μm thin layer on a piece of glass 10×15 cm was created. The photocatalytic activity of the prepared layers was assessed from the kinetics of the photocatalytic degradation of butane in the gas phase. Conclusions The best photocatalytic activity under UV was observed for sample denoted TiGO_100 (k = 0.03012 h-1), while sample labeled TiGO_075 (k = 0.00774 h-1) demonstrated the best activity under visible light. PMID:23445868

  10. Low temperature fabrication of CuxO thin-film transistors and investigation on the origin of low field effect mobility

    NASA Astrophysics Data System (ADS)

    Shijeesh, M. R.; Jayaraj, M. K.

    2018-04-01

    Cuprous (Cu2O) and cupric (CuO) oxide thin films have been deposited by radio frequency magnetron sputtering with two different oxygen partial pressures. The as-deposited copper oxide films were subjected to post-annealing at 300 °C for 30 min to improve the microstructural, morphological, and optical properties of thin films. Optical absorption studies revealed the existence of a large number of subgap states inside CuO films than Cu2O films. Cu2O and CuO thin film transistors (TFTs) were fabricated in an inverted staggered structure by using a post-annealed channel layer. The field effect mobility values of Cu2O and CuO TFTs were 5.20 × 10-4 cm2 V-1 s-1 and 2.33 × 10-4 cm2 V-1 s-1, respectively. The poor values of subthreshold swing, threshold voltage, and field effect mobility of the TFTs were due to the charge trap density at the copper oxide/dielectric interface as well as defect induced trap states originated from the oxygen vacancies inside the bulk copper oxide. In order to study the distribution of the trap states in the Cu2O and CuO active layer, the temperature dependent transfer characteristics of transistors in the temperature range between 310 K and 340 K were studied. The observed subgap states were found to be decreasing exponentially inside the bandgap, with CuO TFT showing higher subgap states than Cu2O TFT. The high-density hole trap states in the CuO channel are one of the plausible reasons for the lower mobility in CuO TFT than in Cu2O TFT. The origin of these subgap states was attributed to the impurities or oxygen vacancies present in the CuO channel layer.

  11. Surface modification of a polyimide gate insulator with an yttrium oxide interlayer for aqueous-solution-processed ZnO thin-film transistors.

    PubMed

    Jang, Kwang-Suk; Wee, Duyoung; Kim, Yun Ho; Kim, Jinsoo; Ahn, Taek; Ka, Jae-Won; Yi, Mi Hye

    2013-06-11

    We report a simple approach to modify the surface of a polyimide gate insulator with an yttrium oxide interlayer for aqueous-solution-processed ZnO thin-film transistors. It is expected that the yttrium oxide interlayer will provide a surface that is more chemically compatible with the ZnO semiconductor than is bare polyimde. The field-effect mobility and the on/off current ratio of the ZnO TFT with the YOx/polyimide gate insulator were 0.456 cm(2)/V·s and 2.12 × 10(6), respectively, whereas the ZnO TFT with the polyimide gate insulator was inactive.

  12. Nano-sized Mn3O4 and β-MnOOH from the decomposition of β-cyclodextrin-Mn: 2. The water-oxidizing activities.

    PubMed

    Najafpour, Mohammad Mahdi; Mostafalu, Ramin; Hołyńska, Małgorzata; Ebrahimi, Foad; Kaboudin, Babak

    2015-11-01

    Nano-sized Mn oxides contain Mn3O4, β-MnOOH and Mn2O3 have been prepared by a previously reported method using thermal decomposition of β-cyclodextrin-Mn complexes. In the next step, the water-oxidizing activities of these Mn oxides using cerium(IV) ammonium nitrate as a chemical oxidant are studied. The turnover frequencies for β-MnO(OH) and Mn3O4 are 0.24 and 0.01-0.17 (mmol O2/mol Mns), respectively. Subsequently, water-oxidizing activities of these compounds are compared to the other previously reported Mn oxides. Important factors affecting water oxidation by these Mn oxides are also discussed. Copyright © 2015 Elsevier B.V. All rights reserved.

  13. Strain-induced phenomenon in complex oxide thin films

    NASA Astrophysics Data System (ADS)

    Haislmaier, Ryan

    to deposit single monolayers of SrO and TiO2 is utilized to build the RP film structure over a time period of 5 hours. This is the first time that a thin film RP phase has been grown using hybrid MBE, where an a stable control over the fluxes is demonstrated during relatively long time periods of growth, which advantageously facilitates the synthesis of high-quality RP materials with excellent structural and chemical homogeneity. Additionally, this work demonstrates some major advancements in optical second harmonic generation (SHG) characterization techniques of ferroelectric thin film materials. The SHG characterization techniques developed here proved to be the 'bread-and-butter' for most of the work performed in this thesis, providing a powerful tool for identifying the existence of strain-induced ferroelectric phases, including their temperature dependence and polar symmetry. The work presented in this dissertation will hopefully provide a preliminary road map for future hybrid MBE growers, scientists and researchers, to develop and investigate epitaxial strain and heterostructure layering induced phenomena in other complex oxide systems.

  14. Oxygen vacancy induced room temperature ferromagnetism in (In1-xNix)2O3 thin films

    NASA Astrophysics Data System (ADS)

    Chakraborty, Deepannita; Kaleemulla, S.; Kuppan, M.; Rao, N. Madhusudhana; Krishnamoorthi, C.; Omkaram, I.; Reddy, D. Sreekantha; Rao, G. Venugopal

    2018-05-01

    Nickel doped indium oxide thin films (In1-xNix)2O3 at x = 0.00, 0.03, 0.05 and 0.07 were deposited onto glass substrates by electron beam evaporation technique. The deposited thin films were subjected to annealing in air at 250 °C, 350 °C and 450 °C for 2 h using high temperature furnace. A set of films were vacuum annealed at 450 °C to study the role of oxygen on magnetic properties of the (In1-xNix)2O3 thin films. The thin films were subjected to different characterization techniques to study their structural, chemical, surface, optical and magnetic properties. All the synthesized air annealed and vacuum annealed films exhibit body centered cubic structure without any secondary phases. No significant change in the diffraction peak position, either to lower or higher diffraction angles has been observed. The band gap of the films decreased from 3.73 eV to 3.63 eV with increase of annealing temperature from 250 °C to 450 °C, in the presence of air. From a slight decrease in strength of magnetization to a complete disappearance of hysteresis loop has been observed in pure In2O3 thin films with increasing the annealing temperature from 250 °C to 450 °C, in the presence of air. The (In1-xNix)2O3 thin films annealed under vacuum follow a trend of enhancement in the strength of magnetization to increase in temperature from 250 °C to 450 °C. The hysteresis loop does not disappear at 450 °C in (In1-xNix)2O3 thin films, as observed in the case of pure In2O3 thin films.

  15. Fe2 PO5 -Encapsulated Reverse Energetic ZnO/Fe2 O3 Heterojunction Nanowire for Enhanced Photoelectrochemical Oxidation of Water.

    PubMed

    Qin, Dong-Dong; He, Cai-Hua; Li, Yang; Trammel, Antonio C; Gu, Jing; Chen, Jing; Yan, Yong; Shan, Duo-Liang; Wang, Qiu-Hong; Quan, Jing-Jing; Tao, Chun-Lan; Lu, Xiao-Quan

    2017-07-10

    Zinc oxide is regarded as a promising candidate for application in photoelectrochemical water oxidation due to its higher electron mobility. However, its instability under alkaline conditions limits its application in a practical setting. Herein, we demonstrate an easily achieved wet-chemical route to chemically stabilize ZnO nanowires (NWs) by protecting them with a thin layer Fe 2 O 3 shell. This shell, in which the thickness can be tuned by varying reaction times, forms an intact interface with ZnO NWs, thus protecting ZnO from corrosion in a basic solution. The reverse energetic heterojunction nanowires are subsequently activated by introducing an amorphous iron phosphate, which substantially suppressed surface recombination as a passivation layer and improved photoelectrochemical performance as a potential catalyst. Compared with pure ZnO NWs (0.4 mA cm -2 ), a maximal photocurrent of 1.0 mA cm -2 is achieved with ZnO/Fe 2 O 3 core-shell NWs and 2.3 mA cm -2 was achieved for the PH 3 -treated NWs at 1.23 V versus RHE. The PH 3 low-temperature treatment creates a dual function, passivation and catalyst layer (Fe 2 PO 5 ), examined by X-ray photoelectron spectroscopy, TEM, photoelectrochemical characterization, and impedance measurements. Such a nano-composition design offers great promise to improve the overall performance of the photoanode material. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Facile synthesis of magnetic ZnFe2O4-reduced graphene oxide hybrid and its photo-Fenton-like behavior under visible iradiation.

    PubMed

    Yao, Yunjin; Qin, Jiacheng; Cai, Yunmu; Wei, Fengyu; Lu, Fang; Wang, Shaobin

    2014-06-01

    A magnetic ZnFe2O4-reduced graphene oxide (rGO) hybrid was successfully developed as a heterogeneous catalyst for photo-Fenton-like decolorization of various dyes using peroxymonosulfate (PMS) as an oxidant under visible light irradiation. Through an in situ chemical deposition and reduction, ZnFe2O4 nanoparticles (NPs) with an average size of 23.7 nm were anchored uniformly on rGO sheets to form a ZnFe2O4-rGO hybrid. The catalytic activities in oxidative decomposition of organic dyes were evaluated. The reaction kinetics, effect of ion species and strength, catalytic stability, degradation mechanism, as well as the roles of ZnFe2O4 and graphene were also studied. ZnFe2O4-rGO showed to be a promising photocatalyst with magnetism for the oxidative degradation of aqueous organic pollutants and simple separation. The combination of ZnFe2O4 NPs with graphene sheets leads to a much higher catalytic activity than pure ZnFe2O4. Graphene acted as not only a support and stabilizer for ZnFe2O4 to prevent them from aggregation, largely improving the charge separation in the hybrid material, but also a catalyst for activating PMS to produce sulfate radicals at the same time. The ZnFe2O4-rGO hybrid exhibited stable performance without losing activity after five successive runs.

  17. Nanoporous Ca3Co4O9 Thin Films for Transferable Thermoelectrics

    PubMed Central

    2018-01-01

    The development of high-performance and transferable thin-film thermoelectric materials is important for low-power applications, e.g., to power wearable electronics, and for on-chip cooling. Nanoporous films offer an opportunity to improve thermoelectric performance by selectively scattering phonons without affecting electronic transport. Here, we report the growth of nanoporous Ca3Co4O9 thin films by a sequential sputtering-annealing method. Ca3Co4O9 is promising for its high Seebeck coefficient and good electrical conductivity and important for its nontoxicity, low cost, and abundance of its constituent raw materials. To grow nanoporous films, multilayered CaO/CoO films were deposited on sapphire and mica substrates by rf-magnetron reactive sputtering from elemental Ca and Co targets, followed by annealing at 700 °C to form the final phase of Ca3Co4O9. This phase transformation is accompanied by a volume contraction causing formation of nanopores in the film. The thermoelectric propoperties of the nanoporous Ca3Co4O9 films can be altered by controlling the porosity. The lowest electrical resistivity is ∼7 mΩ cm, yielding a power factor of 2.32 × 10–4 Wm–1K–2 near room temperature. Furthermore, the films are transferable from the primary mica substrates to other arbitrary polymer platforms by simple dry transfer, which opens an opportunity of low-temperature use these materials. PMID:29905306

  18. Synthesis and electronic properties of Fe 2TiO 5 epitaxial thin films

    DOE PAGES

    Osada, Motoki; Nishio, Kazunori; Hwang, Harold Y.; ...

    2018-05-02

    Here, we investigate the growth phase diagram of pseudobrookite Fe 2TiO 5 epitaxial thin films on LaAlO 3 (001) substrates using pulsed laser deposition. Control of the oxygen partial pressure and temperature during deposition enabled selective stabilization of (100)- and (230)-oriented films. In this regime, we find an optical gap of 2.1 eV and room temperature resistivity in the range of 20–80 Ω cm, which are significantly lower than α-Fe 2O 3, making Fe 2TiO 5 potentially an ideal inexpensive visible-light harvesting semiconductor. These results provide a basis to incorporate Fe 2TiO 5 in oxide heterostructures for photocatalytic and photoelectrochemicalmore » applications.« less

  19. Fabrication of thin film TiO2 nanotube arrays on Co-28Cr-6Mo alloy by anodization.

    PubMed

    Ni, Jiahua; Frandsen, Christine J; Noh, Kunbae; Johnston, Gary W; He, Guo; Tang, Tingting; Jin, Sungho

    2013-04-01

    Titanium oxide (TiO2) nanotube arrays were prepared by anodization of Ti/Au/Ti trilayer thin film DC sputtered onto forged and cast Co-28Cr-6Mo alloy substrate at 400 °C. Two different types of deposited film structures (Ti/Au/Ti trilayer and Ti monolayer), and two deposition temperatures (room temperature and 400 °C) were compared in this work. The concentrations of ammonium fluoride (NH4F) and H2O in glycerol electrolyte were varied to study their effect on the formation of TiO2 nanotube arrays on a forged and cast Co-28Cr-6Mo alloy. The results show that Ti/Au/Ti trilayer thin film and elevated temperature sputtered films are favorable for the formation of well-ordered nanotube arrays. The optimized electrolyte concentration for the growth of TiO2 nanotube arrays on forged and cast Co-28Cr-6Mo alloy was obtained. This work contains meaningful results for the application of a TiO2 nanotube coating to a CoCr alloy implant for potential next-generation orthopedic implant surface coatings with improved osseointegrative capabilities. Copyright © 2013 Elsevier B.V. All rights reserved.

  20. (Na{sub x}k{sub 1−x}){sub 2}Ta{sub 4}O{sub 11}(x≈0.93) piezoelectric phase from the transformation of Ta{sub 2}O{sub 5} thin films of monoclinic structure

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Le Gallic, M., E-mail: Marie.Le-Gallic@grenoble-inp.fr; Roussel, H.

    2013-04-15

    A phase of trigonal structure has been reported in previous articles to be piezoelectric with a very high longitudinal d{sub 33} coefficient of several thousand pm/V (J. Solid State Chem. 184 (2011) 2023, 2033). It was observed in Ta{sub 2}O{sub 5} thin films and assumed to be the result of a reversible monoclinic–trigonal phase transition. However, new investigations are reported because the cell parameters of this phase are actually very close to those of the natrotantite mineral Na{sub 2}Ta{sub 4}O{sub 11}. From analyses by X-ray energy dispersive spectroscopy (XEDS), the chemical composition of this trigonal phase corresponds to (Na{sub x}K{submore » 1−x}){sub 2}Ta{sub 4}O{sub 11} with x≈0.93. The origin of sodium, potassium, iron and oxygen atoms is found to be due to a pollution coming from alumina crucibles used for thermal treatments. Knowing both atomic structures Ta{sub 2}O{sub 5} and Na{sub 2}Ta{sub 4}O{sub 11} and their structural relationships, observed by high resolution transmission electron microscopy (HRTEM), the mechanism of the reaction of transformation is re-examined and discussed. This mechanism implies that Ta{sup 5+} vacancies likely exist in monoclinic structures of tantalum oxide and that electrical neutrality could be due to incorporated proton H{sup +} instead of O{sup 2−} vacancies or Ta{sup 5+} interstitials. - Graphical abstract: (a, b) TEM images of interfaces between Ta{sub 2}O{sub 5} monoclinic and (Na{sub 0.93}K{sub 0.07}){sub 2}Ta{sub 4}O{sub 11} trigonal phases where it appears that the ratio of periods for the transformation monoclinic-to-trigonal is 3/2 (c, d) corresponding schema of the reaction of transformation, (a, c) viewed along the zone axes [010]{sub o}∥[1{sup ¯}21{sup ¯}]{sub R} and (b, d) along the zone axes [100]{sub o}∥[101{sup ¯}]{sub R}. Highlights: ► The formation of a piezoelectric phase in Ta{sub 2}O{sub 5} thin films, reported in previous articles, is re-examined. ► Its composition is

  1. Chemical and Electrochemical Asymmetric Dihydroxylation of Olefins in I(2)-K(2)CO(3)-K(2)OsO(2)(OH)(4) and I(2)-K(3)PO(4)/K(2)HPO(4)-K(2)OsO(2)(OH)(4) Systems with Sharpless' Ligand.

    PubMed

    Torii, Sigeru; Liu, Ping; Bhuvaneswari, Narayanaswamy; Amatore, Christian; Jutand, Anny

    1996-05-03

    Iodine-assisted chemical and electrochemical asymmetric dihydroxylation of various olefins in I(2)-K(2)CO(3)-K(2)OsO(2)(OH)(4) and I(2)-K(3)PO(4)/K(2)HPO(4)-K(2)OsO(2)(OH)(4) systems with Sharpless' ligand provided the optically active glycols in excellent isolated yields and high enantiomeric excesses. Iodine (I(2)) was used stoichiometrically for the chemical dihydroxylation, and good results were obtained with nonconjugated olefins in contrast to the case of potassium ferricyanide as a co-oxidant. The potentiality of I(2) as a co-oxidant under stoichiometric conditions has been proven to be effective as an oxidizing mediator in electrolysis systems. Iodine-assisted asymmetric electro-dihydroxylation of olefins in either a t-BuOH/H(2)O(1/1)-K(2)CO(3)/(DHQD)(2)PHAL-(Pt) or t-BuOH/H(2)O(1/1)-K(3)PO(4)/K(2)HPO(4)/(DHQD)(2)PHAL-(Pt) system in the presence of potassium osmate in an undivided cell was investigated in detail. Irrespective of the substitution pattern, all the olefins afforded the diols in high yields and excellent enantiomeric excesses. A plausible mechanism is discussed on the basis of cyclic voltammograms as well as experimental observations.

  2. High-Throughput Synthesis and Characterization of Eu Doped Ba xSr2- xSiO4 Thin Film Phosphors.

    PubMed

    Frost, Sara; Guérin, Samuel; Hayden, Brian E; Soulié, Jean-Philippe; Vian, Chris

    2018-06-20

    High-throughput techniques have been employed for the synthesis and characterization of thin film phosphors of Eu-doped Ba x Sr 2- x SiO 4 . Direct synthesis from evaporation of the constituent elements under a flux of atomic oxygen on a sapphire substrate at 850 °C was used to directly produce thin film libraries (415 nm thickness) of the crystalline orthosilicate phase with the desired compositional variation (0.24 > x > 1.86). The orthosilicate phase could be synthesized as a pure, or predominantly pure, phase. Annealing the as synthesized library in a reducing atmosphere resulted in the reduction of the Eu while retaining the orthosilicate phase, and resulted in a materials thin film library where fluorescence excited by blue light (450 nm) was observable by the naked eye. Parallel screening of the fluorescence from the combinatorial libraries of Eu doped Ba x Sr 2- x SiO 4 has been implemented by imaging the fluorescent radiation over the library using a monochrome digital camera using a series of color filters. Informatics tools have been developed to allow the 1931 CIE color coordinates and the relative quantum efficiencies of the materials library to be rapidly assessed and mapped against composition, crystal structure and phase purity. The range of compositions gave values of CIE x between 0.17 and 0.52 and CIE y between 0.48 and 0.69 with relative efficiencies in the range 2.0 × 10 -4 -7.6 × 10 -4 . Good agreement was obtained between the thin film phosphors and the fluorescence characteristics of a number of corresponding bulk phosphor powders. The thermal quenching of fluorescence in the thin film libraries was also measured in the temperature range 25-130 °C: The phase purity of the thin film was found to significantly influence both the relative quantum efficiency and the thermal quenching of the fluorescence.

  3. Growth of metal oxide thin films by laser-induced metalorganic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Tokita, Koji; Okada, Fumio

    1996-12-01

    The growth of metal oxide thin films by laser-induced metalorganic chemical vapor deposition was investigated by changing wavelength, power, repetition rate, and irradiation angle of the excimer laser. When O2 was used as an oxidizing gas with 193 or 248 nm irradiation, amorphous TiO2 and crystalline PbO films were obtained in the laser-irradiated area of Si substrates from the parent metalorganic compounds, Ti(O-iC3H7)4 and (C2H5)3PbOCH2C(CH3)3, respectively. In contrast, no ZrO2 film could be formed from Zr(O-tC4H9)4. One-photon formation of TiO2 films was confirmed from laser power dependence measurements. The maximum growth rate of 0.05 Å per laser pulse was compared with that estimated by a simple surface reaction model, according to which the slow growth rate is due to the small absorption cross section of Ti(O-iC3H7)4 and mild fluence of laser irradiation. In experiments of ozone gas excitation by KrF laser, a SiO2 film was obtained by gas-phase reactions of the oxygen radical, O(1D), with Si(O-C2H5)4. The direct patterning of TiO2 and PbO films as well as the possibility of producing patterned PbTiO3 film was demonstrated. The growth of the patterned SiO2 film was prevented by gas-phase diffusion of intermediates.

  4. Facile synthesis of mesoporous spinel NiCo2O4 nanostructures as highly efficient electrocatalysts for urea electro-oxidation

    NASA Astrophysics Data System (ADS)

    Ding, Rui; Qi, Li; Jia, Mingjun; Wang, Hongyu

    2014-01-01

    Mesoporous spinel nickel cobaltite (NiCo2O4) nanostructures were synthesized via a facile chemical deposition method coupled with a simple post-annealing process. The physicochemical properties were characterized via X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS) and nitrogen sorption measurements. The electrocatalytic performances were investigated by cyclic voltammetry (CV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS) tests. The obtained NiCo2O4 materials exhibit typical agglomerate mesoporous nanostructures with a large surface area (190.1 m2 g-1) and high mesopore volume (0.943 cm3 g-1). Remarkably, the NiCo2O4 shows much higher catalytic activity, lower overpotential, better stability and greater tolerance towards urea electro-oxidation compared to those of cobalt oxide (Co3O4) synthesized by the same procedure. The NiCo2O4 electrode delivers a current density of 136 mA cm-2 mg-1 at 0.7 V (vs. Hg/HgO) in 1 M KOH and 0.33 M urea electrolytes accompanied with a desirable stability. The impressive electrocatalytic activity is largely ascribed to the high intrinsic electronic conductivity, superior mesoporous nanostructures and rich surface Ni active species of the NiCo2O4 materials, which can largely boost the interfacial electroactive sites and charge transfer rates for urea electro-oxidation, indicating promising applications in future wastewater remediation, hydrogen production and fuel cells.Mesoporous spinel nickel cobaltite (NiCo2O4) nanostructures were synthesized via a facile chemical deposition method coupled with a simple post-annealing process. The physicochemical properties were characterized via X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS) and nitrogen sorption measurements. The electrocatalytic performances were investigated by cyclic voltammetry

  5. Dye-sensitized electron transfer from TiO 2 to oxidized triphenylamines that follows first-order kinetics

    DOE PAGES

    DiMarco, Brian N.; Troian-Gautier, Ludovic; Sampaio, Renato N.; ...

    2018-01-01

    Two sensitizers, [Ru(bpy) 2 (dcb)] 2+ ( RuC ) and [Ru(bpy) 2 (dpb)] 2+ ( RuP ), were anchored to mesoporous TiO 2 thin films and utilized to sensitize the reaction of TiO 2 electrons with oxidized triphenylamines to visible light in CH 3 CN electrolytes.

  6. Nucleation of graphene layers on magnetic oxides: Co 3O 4(111) and Cr 2O 3(0001) from theory and experiment

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Beatty, John; Cheng, Tao; Cao, Yuan

    We report directly grown strongly adherent graphene on Co 3O 4(111) by carbon molecular beam epitaxy (C MBE) at 850 K and density functional theory (DFT) findings that the first graphene layer is reconstructed to fit the Co 3O 4 surface, while subsequent layers retain normal graphene structure. This adherence to the Co 3O 4 structure results from partial bonding of half the carbons to top oxygens of the substrate. This structure is validated by X-ray photoelectron spectroscopy and low-energy electron diffraction studies, showing layer-by-layer graphene growth with ~0.08 electrons/carbon atom transferred to the oxide from the first graphene layer,more » in agreement with DFT. In contrast, for Cr 2O 3 DFT finds no strong bonding to the surface and C MBE on Cr 2O 3(0001) yields only graphite formation at 700 K, with C desorption above 800 K. As a result, strong graphene-to-oxide charge transfer aids nucleation of graphene on incommensurate oxide substrates and may have implications for spintronics.« less

  7. Nucleation of graphene layers on magnetic oxides: Co 3O 4(111) and Cr 2O 3(0001) from theory and experiment

    DOE PAGES

    Beatty, John; Cheng, Tao; Cao, Yuan; ...

    2016-12-14

    We report directly grown strongly adherent graphene on Co 3O 4(111) by carbon molecular beam epitaxy (C MBE) at 850 K and density functional theory (DFT) findings that the first graphene layer is reconstructed to fit the Co 3O 4 surface, while subsequent layers retain normal graphene structure. This adherence to the Co 3O 4 structure results from partial bonding of half the carbons to top oxygens of the substrate. This structure is validated by X-ray photoelectron spectroscopy and low-energy electron diffraction studies, showing layer-by-layer graphene growth with ~0.08 electrons/carbon atom transferred to the oxide from the first graphene layer,more » in agreement with DFT. In contrast, for Cr 2O 3 DFT finds no strong bonding to the surface and C MBE on Cr 2O 3(0001) yields only graphite formation at 700 K, with C desorption above 800 K. As a result, strong graphene-to-oxide charge transfer aids nucleation of graphene on incommensurate oxide substrates and may have implications for spintronics.« less

  8. TEM study on the initial oxidation of Zircaloy-4 thin foil specimens heated in a low vacuum air condition at 280-300 °C

    NASA Astrophysics Data System (ADS)

    Wang, Zhen; Zhou, Bang-xin; Zhu, Wei; Wen, Bang; Yao, Mei-yi; Li, Qiang; Wu, Lu; Zhang, Jin-long; Fang, Zhong-qiang

    2017-04-01

    As one of the important structural materials in nuclear industry, the corrosion resistance of zirconium alloy limits their in-pile application. Therefore, it is necessary to investigate the corrosion mechanism of zirconium alloys. The zirconium-oxygen reaction at the O/M interface is one of the factors that affect the oxidation process. There are few reports in this regard. Ideally, the reaction process at the O/M interface has certain relevance with the initiation oxidation of zirconium, which provided a new way to investigate the reaction process by observing the initiation oxidation behaviours. To investigate the oxidation behaviours of zirconium alloy at the initial stage, in this paper, zircaloy-4 TEM thin foil specimens in 3 mm diameter were studied by TEM observation after heating in air condition with a vacuum of 3 Pa at 280 °C, 290 °C and 300 °C for 30 min exposures. The results show that, ZrO2 begin to nucleate at a size of 3-5 nm at a high Zr/O ratio of 10.4 and oxide layer formed while Zr/O was 4.6. As a result of stress caused by the P.B ratio of Zr, slip bands formed and a bcc structure sub-oxide b-ZrOx (a = 0.51 nm) grew up along with the slip bands was observed. At both sides of b-ZrOx, two hcp structure sub-oxides having the same a-axis lattice parameter and different c-axis lattice parameter were detected.

  9. Isotope signatures of N2O emitted from vegetable soil: Ammonia oxidation drives N2O production in NH4(+)-fertilized soil of North China.

    PubMed

    Zhang, Wei; Li, Yuzhong; Xu, Chunying; Li, Qiaozhen; Lin, Wei

    2016-07-08

    Nitrous oxide (N2O) is a potent greenhouse gas. In North China, vegetable fields are amended with high levels of N fertilizer and irrigation water, which causes massive N2O flux. The aim of this study was to determine the contribution of microbial processes to N2O production and characterize isotopic signature effects on N2O source partitioning. We conducted a microcosm study that combined naturally abundant isotopologues and gas inhibitor techniques to analyze N2O flux and its isotopomer signatures [δ(15)N(bulk), δ(18)O, and SP (intramolecular (15)N site preference)] that emitted from vegetable soil after the addition of NH4(+) fertilizers. The results show that ammonia oxidation is the predominant process under high water content (70% water-filled pore space), and nitrifier denitrification contribution increases with increasing N content. δ(15)N(bulk) and δ(18)O of N2O may not provide information about microbial processes due to great shifts in precursor signatures and atom exchange, especially for soil treated with NH4(+) fertilizer. SP and associated two end-member mixing model are useful to distinguish N2O source and contribution. Further work is needed to explore isotopomer signature stability to improve N2O microbial process identification.

  10. Isotope signatures of N2O emitted from vegetable soil: Ammonia oxidation drives N2O production in NH4+-fertilized soil of North China

    NASA Astrophysics Data System (ADS)

    Zhang, Wei; Li, Yuzhong; Xu, Chunying; Li, Qiaozhen; Lin, Wei

    2016-07-01

    Nitrous oxide (N2O) is a potent greenhouse gas. In North China, vegetable fields are amended with high levels of N fertilizer and irrigation water, which causes massive N2O flux. The aim of this study was to determine the contribution of microbial processes to N2O production and characterize isotopic signature effects on N2O source partitioning. We conducted a microcosm study that combined naturally abundant isotopologues and gas inhibitor techniques to analyze N2O flux and its isotopomer signatures [δ15Nbulk, δ18O, and SP (intramolecular 15N site preference)] that emitted from vegetable soil after the addition of NH4+ fertilizers. The results show that ammonia oxidation is the predominant process under high water content (70% water-filled pore space), and nitrifier denitrification contribution increases with increasing N content. δ15Nbulk and δ18O of N2O may not provide information about microbial processes due to great shifts in precursor signatures and atom exchange, especially for soil treated with NH4+ fertilizer. SP and associated two end-member mixing model are useful to distinguish N2O source and contribution. Further work is needed to explore isotopomer signature stability to improve N2O microbial process identification.

  11. Fabrication and characterization of oxide-based thin film transistors, and process development for oxide heterostructures

    NASA Astrophysics Data System (ADS)

    Lim, Wantae

    2009-12-01

    This dissertation is focused on the development of thin film transistors (TFTs) using oxide materials composed of post-transitional cations with (n-1)d 10ns0 (n≥4). The goal is to achieve high performance oxide-based TFTs fabricated at low processing temperature on either glass or flexible substrates for next generation display applications. In addition, etching mechanism and Ohmic contact formation for oxide heterostructure (ZnO/CuCrO 2) system is demonstrated. The deposition and characterization of oxide semiconductors (In 2O3-ZnO, and InGaZnO4) using a RF-magnetron sputtering system are studied. The main influence on the resistivity of the films is found to be the oxygen partial pressure in the sputtering ambient. The films remained amorphous and transparent (> 70%) at all process conditions. These films showed good transmittance at suitable conductivity for transistor fabrication. The electrical characteristics of both top- and bottom-gate type Indium Zinc Oxide (InZnO) and Indium Gallium Zinc Oxide (InGaZnO4)-based TFTs are reported. The InZnO films were favorable for depletion-mode TFTs due to their tendency to form oxygen vacancies, while enhancement-mode devices were realized with InGaZnO4 films. The InGaZnO4-based TFTs fabricated on either glass or plastic substrates at low temperature (<100°C) exhibit good electrical properties: the saturation mobility of 5--12 cm2.V-1.s-1 and threshold voltage of 0.5--2.5V. The devices are also examined as a function of aging time in order to verify long-term stability in air. The effect of gate dielectric materials on electrical properties of InGaZnO 4-based TFTs was investigated. The use of SiNx film as a gate dielectric reduces the trap density and the roughness at the channel/gate dielectric interface compared to SiO2 gate dielectric, resulting in an improvement of device parameters by reducing scattering of trapped charges at the interface. The quality of interface is shown to have large effect on TFT performance

  12. Is [Co4(H2O)2(α-PW9O34)2](10-) a genuine molecular catalyst in photochemical water oxidation? Answers from time-resolved hole scavenging experiments.

    PubMed

    Natali, Mirco; Berardi, Serena; Sartorel, Andrea; Bonchio, Marcella; Campagna, Sebastiano; Scandola, Franco

    2012-09-11

    Water oxidation catalysts: evolution of [Co(4)(H(2)O)(2)(α-PW(9)O(34))(2)](10-) to catalytically active species is assessed by laser flash photolysis in sacrificial photocatalytic cycles with Ru(bpy)(3)(2+) as a photosensitizer.

  13. First-principles study on the effect of SiO{sub 2} layers during oxidation of 4H-SiC

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ono, Tomoya, E-mail: ono@ccs.tsukuba.ac.jp; JST-PRESTO, Kawaguchi, Saitama 332-0012; Saito, Shoichiro

    The effect of SiO{sub 2} layers during the thermal oxidation of a 4H-SiC(0001) substrate is examined by performing the first-principles total-energy calculations. Although it is expected that a CO molecule is the most preferable product during the oxidation, CO{sub 2} molecules are mainly emitted from the SiC surface at the initial stage of the oxidation. As the oxidation proceeds, CO{sub 2} emission becomes less favorable and CO molecules are emitted from the interface. We conclude that the interface stress due to the lattice constant mismatch between 4H-SiC(0001) and SiO{sub 2} is responsible for the removal of C during the oxidation,more » resulting in the characteristic electronic property of the interface fabricated by the thermal oxidation.« less

  14. Bi-functional anodic TiO2 oxide: Nanotubes for wettability control and barrier oxide for uniform coloring

    NASA Astrophysics Data System (ADS)

    Kim, Sunkyu; Jung, Minkyeong; Kim, Moonsu; Choi, Jinsub

    2017-06-01

    A uniformly colored TiO2, on which the surface is functionalized with nanotubes to control wettability, was prepared by a two-step anodization; the first anodization was carried out to prepare nanotubes for a super-hydrophilic or -hydrophobic surface and the second anodization was performed to fabricate a thin film barrier oxide to ensure uniform coloring. The effect of the nanotubes on barrier oxide coloring was examined by spectrophotometry and UV-vis-IR spectroscopy. We found four different regimes governing the color changes in terms of anodization voltage, indicating that the color of the duplex TiO2 was primarily determined by the thickness of the barrier oxide layer formed during the second anodization step. The surface wettability, as confirmed by the water contact angle, revealed that the single barrier TiO2 yielded 74.6° ± 2.1, whereas the nanotubes on the barrier oxide imparted super-hydrophilic properties as a result of increasing surface roughness as well as imparting a higher hydrophobicity after organic acid treatment.

  15. Photocurrent generation in SnO2 thin film by surface charged chemisorption O ions

    NASA Astrophysics Data System (ADS)

    Lee, Po-Ming; Liao, Ching-Han; Lin, Chia-Hua; Liu, Cheng-Yi

    2018-06-01

    We report a photocurrent generation mechanism in the SnO2 thin film surface layer by the charged chemisorption O ions on the SnO2 thin film surface induced by O2-annealing. A critical build-in electric field in the SnO2 surface layer resulted from the charged O ions on SnO2 surface prolongs the lifetime and reduces the recombination probability of the photo-excited electron-hole pairs by UV-laser irradiation (266 nm) in the SnO2 surface layer, which is the key for the photocurrent generation in the SnO2 thin film surface layer. The critical lifetime of prolonged photo-excited electron-hole pair is calculated to be 8.3 ms.

  16. Low temperature fabrication of metal oxide thin film transistors formed by a heated aqueous precursor solution

    NASA Astrophysics Data System (ADS)

    Lee, Keun Ho; Han, Sun Woong; Park, Jee Ho; Yoo, Young Bum; Jong Lee, Se; Baik, Hong Koo; Song, Kie Moon

    2016-01-01

    We introduce an easy process for the fabrication of solution-processed indium oxide (InO) thin film transistors (TFTs) by heating a precursor solution. InO TFTs fabricated from solutions of an InO precursor heated at 90 °C had the highest mobility of 4.61 cm2 V-1 s-1 after being annealed at 200 °C. When the InO precursor solution is heated, HNO3 may be thermally evaporated in the InO precursor solution. Nitrogen atoms can disrupt hydrolysis and condensation reactions. An InO thin film deposited from a solution of the heated InO precursor is advantageous for hydrolysis and condensation reactions due to the absence of nitrogen atoms.

  17. The effect of B 2O 3 addition on the crystallization of amorphous TiO 2-ZrO 2 mixed oxide

    NASA Astrophysics Data System (ADS)

    Mao, Dongsen; Lu, Guanzhong

    2007-02-01

    The effect of B 2O 3 addition on the crystallization of amorphous TiO 2-ZrO 2 mixed oxide was investigated by X-ray diffraction (XRD), thermogravimetric and differential thermal analysis (TG/DTA). TiO 2-ZrO 2 mixed oxide was prepared by co-precipitation method with aqueous ammonia as the precipitation reagent. Boric acid was used as a source of boria, and boria contents varied from 2 to 20 wt%. The results indicate that the addition of small amount of boria (<8 wt%) hinders the crystallization of amorphous TiO 2-ZrO 2 into a crystalline ZrTiO 4 compound, while a larger amount of boria (⩾8 wt%) promotes the crystallization process. FT-IR spectroscopy and 11B MAS NMR results show that tetrahedral borate species predominate at low boria loading, and trigonal borate species increase with increasing boria loading. Thus it is concluded that highly dispersed tetrahedral BO 4 units delay, while a build-up of trigonal BO 3 promote, the crystallization of amorphous TiO 2-ZrO 2 to form ZrTiO 4 crystals.

  18. Combinatorial study of zinc tin oxide thin-film transistors

    NASA Astrophysics Data System (ADS)

    McDowell, M. G.; Sanderson, R. J.; Hill, I. G.

    2008-01-01

    Groups of thin-film transistors using a zinc tin oxide semiconductor layer have been fabricated via a combinatorial rf sputtering technique. The ZnO :SnO2 ratio of the film varies as a function of position on the sample, from pure ZnO to SnO2, allowing for a study of zinc tin oxide transistor performance as a function of channel stoichiometry. The devices were found to have mobilities ranging from 2to12cm2/Vs, with two peaks in mobility in devices at ZnO fractions of 0.80±0.03 and 0.25±0.05, and on/off ratios as high as 107. Transistors composed predominantly of SnO2 were found to exhibit light sensitivity which affected both the on/off ratios and threshold voltages of these devices.

  19. Low-temperature preparation of GaN-SiO2 interfaces with low defect density. II. Remote plasma-assisted oxidation of GaN and nitrogen incorporation

    NASA Astrophysics Data System (ADS)

    Bae, Choelhwyi; Lucovsky, Gerald

    2004-11-01

    Low-temperature remote plasma-assisted oxidation and nitridation processes for interface formation and passivation have been extended from Si and SiC to GaN. The initial oxidation kinetics and chemical composition of thin interfacial oxide were determined from analysis of on-line Auger electron spectroscopy features associated with Ga, N, and O. The plasma-assisted oxidation process is self-limiting with power-law kinetics similar to those for the plasma-assisted oxidation of Si and SiC. Oxidation using O2/He plasma forms nearly pure GaOx, and oxidation using 1% N2O in N2 forms GaOxNy with small nitrogen content, ~4-7 at. %. The interface and dielectric layer quality was investigated using fabricated GaN metal-oxide-semiconductor capacitors. The lowest density of interface states was achieved with a two-step plasma-assisted oxidation and nitridation process before SiO2 deposition.

  20. Surface texture of single-crystal silicon oxidized under a thin V{sub 2}O{sub 5} layer

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Nikitin, S. E., E-mail: nikitin@mail.ioffe.ru; Verbitskiy, V. N.; Nashchekin, A. V.

    The process of surface texturing of single-crystal silicon oxidized under a V{sub 2}O{sub 5} layer is studied. Intense silicon oxidation at the Si–V{sub 2}O{sub 5} interface begins at a temperature of 903 K which is 200 K below than upon silicon thermal oxidation in an oxygen atmosphere. A silicon dioxide layer 30–50 nm thick with SiO{sub 2} inclusions in silicon depth up to 400 nm is formed at the V{sub 2}O{sub 5}–Si interface. The diffusion coefficient of atomic oxygen through the silicon-dioxide layer at 903 K is determined (D ≥ 2 × 10{sup –15} cm{sup 2} s{sup –1}). A modelmore » of low-temperature silicon oxidation, based on atomic oxygen diffusion from V{sub 2}O{sub 5} through the SiO{sub 2} layer to silicon, and SiO{sub x} precipitate formation in silicon is proposed. After removing the V{sub 2}O{sub 5} and silicon-dioxide layers, texture is formed on the silicon surface, which intensely scatters light in the wavelength range of 300–550 nm and is important in the texturing of the front and rear surfaces of solar cells.« less

  1. Study of nanoparticles TiO{sub 2} thin films on p-type silicon substrate using different alcoholic solvents

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Muaz, A. K. M.; Ruslinda, A. R.; Ayub, R. M.

    2016-07-06

    In this paper, sol-gel method spin coating technique is adopted to prepare nanoparticles titanium dioxide (TiO{sub 2}) thin films. The prepared TiO{sub 2} sol was synthesized using titanium butoxide act as a precursor and subjected to deposited on the p-type silicon oxide (p-SiO{sub 2}) and glass slide substrates under room temperature. The effect of different alcoholic solvents of methanol and ethanol on the structural, morphological, optical and electrical properties were systematically investigated. The coated TiO{sub 2} thin films were annealed in furnace at 773 K for 1 h. The structural properties of the TiO{sub 2} films were examined with X-raymore » Diffraction (XRD). From the XRD analysis, both solvents showing good crystallinity with anatase phase were the predominant structure. Atomic Force Microscopy (AFM) was employed to study the morphological of the thin films. The optical properties were investigated by Ultraviolet-visible (UV-Vis) spectroscopy were found that ethanol as a solvent give a higher optical transmittance if compare to the methanol solvent. The electrical properties of the nanoparticles TiO{sub 2} thin films were measured using two-point-probe technique.« less

  2. Low temperature growth of gallium oxide thin films via plasma enhanced atomic layer deposition.

    PubMed

    O'Donoghue, Richard; Rechmann, Julian; Aghaee, Morteza; Rogalla, Detlef; Becker, Hans-Werner; Creatore, Mariadriana; Wieck, Andreas Dirk; Devi, Anjana

    2017-12-21

    Herein we describe an efficient low temperature (60-160 °C) plasma enhanced atomic layer deposition (PEALD) process for gallium oxide (Ga 2 O 3 ) thin films using hexakis(dimethylamido)digallium [Ga(NMe 2 ) 3 ] 2 with oxygen (O 2 ) plasma on Si(100). The use of O 2 plasma was found to have a significant improvement on the growth rate and deposition temperature when compared to former Ga 2 O 3 processes. The process yielded the second highest growth rates (1.5 Å per cycle) in terms of Ga 2 O 3 ALD and the lowest temperature to date for the ALD growth of Ga 2 O 3 and typical ALD characteristics were determined. From in situ quartz crystal microbalance (QCM) studies and ex situ ellipsometry measurements, it was deduced that the process is initially substrate-inhibited. Complementary analytical techniques were employed to investigate the crystallinity (grazing-incidence X-ray diffraction), composition (Rutherford backscattering analysis/nuclear reaction analysis/X-ray photoelectron spectroscopy), morphology (X-ray reflectivity/atomic force microscopy) which revealed the formation of amorphous, homogeneous and nearly stoichiometric Ga 2 O 3 thin films of high purity (carbon and nitrogen <2 at.%) under optimised process conditions. Tauc plots obtained via UV-Vis spectroscopy yielded a band gap of 4.9 eV and the transmittance values were more than 80%. Upon annealing at 1000 °C, the transformation to oxygen rich polycrystalline β-gallium oxide took place, which also resulted in the densification and roughening of the layer, accompanied by a slight reduction in the band gap. This work outlines a fast and efficient method for the low temperature ALD growth of Ga 2 O 3 thin films and provides the means to deposit Ga 2 O 3 upon thermally sensitive polymers like polyethylene terephthalate.

  3. Experimental bandstructure of the 5 d transition metal oxide IrO2

    NASA Astrophysics Data System (ADS)

    Kawasaki, Jason; Nie, Yuefeng; Uchida, Masaki; Schlom, Darrell; Shen, Kyle

    2015-03-01

    In the 5 d iridium oxides the close energy scales of spin-orbit coupling and electron-electron correlations lead to emergent quantum phenomena. Much research has focused on the ternary iridium oxides, e.g. the Ruddlesden-Poppers An + 1BnO3 n + 1 , which exhibit behavior from metal to antiferromagnetic insulator ground states, share common features with the cuprates, and may host a number of topological phases. The binary rutile IrO2 is another important 5 d oxide, which has technological importance for spintronics due to its large spin Hall effect and also applications in catalysis. IrO2 is expected to share similar physics as its perovskite-based cousins; however, due to bond-length distortions of the IrO6 octahedra in the rutile structure, the extent of similarities remains an open question. Here we use angle-resolved photoemission spectroscopy to perform momentum-resolved measurements of the electronic structure of IrO2 . IrO2 thin films were grown by molecular beam epitaxy on TiO2 (110) substrates using an Ir e-beam source and distilled ozone. Films were subsequently transferred through ultrahigh vacuum to a connected ARPES system. Combined with first-principles calculations we explore the interplay of spin-orbit coupling and correlations in IrO2 .

  4. Altering properties of cerium oxide thin films by Rh doping

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ševčíková, Klára, E-mail: klarak.sevcikova@seznam.cz; NIMS Beamline Station at SPring-8, National Institute for Materials Science, Sayo, Hyogo 679-5148; Nehasil, Václav, E-mail: nehasil@mbox.troja.mff.cuni.cz

    2015-07-15

    Highlights: • Thin films of ceria doped by rhodium deposited by RF magnetron sputtering. • Concentration of rhodium has great impact on properties of Rh–CeO{sub x} thin films. • Intensive oxygen migration in films with low concentration of rhodium. • Oxygen migration suppressed in films with high amount of Rh dopants. - Abstract: Ceria containing highly dispersed ions of rhodium is a promising material for catalytic applications. The Rh–CeO{sub x} thin films with different concentrations of rhodium were deposited by RF magnetron sputtering and were studied by soft and hard X-ray photoelectron spectroscopies, Temperature programmed reaction and X-ray powder diffractionmore » techniques. The sputtered films consist of rhodium–cerium mixed oxide where cerium exhibits a mixed valency of Ce{sup 4+} and Ce{sup 3+} and rhodium occurs in two oxidation states, Rh{sup 3+} and Rh{sup n+}. We show that the concentration of rhodium has a great influence on the chemical composition, structure and reducibility of the Rh–CeO{sub x} thin films. The films with low concentrations of rhodium are polycrystalline, while the films with higher amount of Rh dopants are amorphous. The morphology of the films strongly influences the mobility of oxygen in the material. Therefore, varying the concentration of rhodium in Rh–CeO{sub x} thin films leads to preparing materials with different properties.« less

  5. Gallium oxide thin films from the AACVD of [Ga(NMe2)3]2 and donor functionalised alcohols.

    PubMed

    Basharat, Siama; Carmalt, Claire J; Binions, Russell; Palgrave, Robert; Parkin, Ivan P

    2008-02-07

    Thin films of Ga(2)O(3) have been produced from [Ga(NMe(2))(3)](2) and ROH (R = CH(2)CH(2)NMe(2), CH(CH(2)NMe(2))(2), CH(CH(3))CH(2)NMe(2), CH(2)CH(2)OMe and C(CH(3))(2)CH(2)OMe) by aerosol assisted chemical vapour deposition on glass. Transparent, unreflective films were obtained at a deposition temperature of 550 degrees C using toluene as solvent. The gallium oxide films were analyzed by Scanning electron microscopy (SEM), Raman spectroscopy, wavelength dispersive analysis of X-rays (WDX) and X-ray photoelectron spectroscopy (XPS). The gallium oxide films obtained were X-ray amorphous. Gas-sensing experiments indicated that the films showed an n-type response to ethanol at a variety of temperatures.

  6. Preparation of TlBa2Ca2Cu3O9±δ high Tc thin films by laser ablation in combination with thermal evaporation of thallium oxide

    NASA Astrophysics Data System (ADS)

    Piehler, A.; Löw, R.; Betz, J.; Schönberger, R.; Renk, K. F.

    1993-11-01

    TlBa2Ca2Cu3O9±δ high Tc thin films were prepared on MgO <100> surfaces by a combination of laser ablation from a stoichiometric Ba2Ca2Cu3Ox target and the thermal evaporation of thallium oxide. X-ray diffraction measurements showed that the films consisted of predominantly c axis oriented TlBa2Ca2Cu3O9±δ, and scanning electron microscopy revealed that the surfaces had a flat, platelike morphology. The ac inductive measurements indicated that the onset of superconductivity occurred at 117 K with a transition width (10%-90%) of ˜3 K. Zero resistivity was reached at 120 K. The critical current density was ˜3×104 A/cm2 at 110 K.

  7. Easy and General Synthesis of Large-Sized Mesoporous Rare-Earth Oxide Thin Films by 'Micelle Assembly'.

    PubMed

    Li, Yunqi; Bastakoti, Bishnu Prasad; Imura, Masataka; Dai, Pengcheng; Yamauchi, Yusuke

    2015-12-01

    Large-sized (ca. 40 nm) mesoporous Er2O3 thin films are synthesized by using a triblock copolymer poly(styrene-b-2-vinyl pyridine-b-ethylene oxide) (PS-b-P2VP-b-PEO) as a pore directing agent. Each block makes different contributions and the molar ratio of PVP/Er(3+) is crucial to guide the resultant mesoporous structure. An easy and general method is proposed and used to prepare a series of mesoporous rare-earth oxide (Sm2O3, Dy2O3, Tb2O3, Ho2O3, Yb2O3, and Lu2O3) thin films with potential uses in electronics and optical devices. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Structural characterization of niobium oxide thin films grown on SrTiO3 (111) and (La,Sr)(Al,Ta)O3 (111) substrates

    NASA Astrophysics Data System (ADS)

    Dhamdhere, Ajit R.; Hadamek, Tobias; Posadas, Agham B.; Demkov, Alexander A.; Smith, David J.

    2016-12-01

    Niobium oxide thin films have been grown by molecular beam epitaxy on SrTiO3 (STO) (111) and (La0.18Sr0.82)(Al0.59Ta0.41)O3 (LSAT) (111) substrates. Transmission electron microscopy (TEM) confirmed the formation of high quality films with coherent interfaces. Films grown with higher oxygen pressure on STO (111) resulted in a (110)-oriented NbO2 phase with a distorted rutile structure, which can be described as body-centered tetragonal. The a lattice parameter of NbO2 was determined to be ˜13.8 Å in good agreement with neutron diffraction results published in the literature. Films grown on LSAT (111) at lower oxygen pressure produced the NbO phase with a defective rock salt cubic structure. The NbO lattice parameter was determined to be a ≈ 4.26 Å. The film phase/structure identification from TEM was in good agreement with in situ x-ray photoelectron spectroscopy measurements that confirmed the dioxide and monoxide phases, respectively. The atomic structure of the NbO2/STO and NbO/LSAT interfaces was determined based on comparisons between high-resolution electron micrographs and image simulations.

  9. Improved oxidative tolerance in suspension-cultured cells of C4-pepctransgenic rice by H2O2 and Ca(2+) under PEG-6000.

    PubMed

    Qian, Baoyun; Li, Xia; Liu, Xiaolong; Wang, Man

    2015-06-01

    To understand the molecular responses of PC (Overexpressing the maize C4-pepc gene, which encodes phosphoenolpyruvate carboxylase (PEPC)), to drought stress at cell level, we analyzed changes in the levels of signaling molecules (hydrogen peroxide (H2O2), calcium ion (Ca(2+)), and nitric oxide (NO)) in suspension-cultured PC and wild-type (WT) rice (Oryza sativa L.) cell under drought stress induced by 20% polyethylene glycol 6000 (PEG-6000). Results demonstrated that PC improved drought tolerance by enhancing antioxidant defense, retaining higher relative water content, survival percentages, and dry weight of cells. In addition, PEPC activity in PC under PEG treatment was strengthened by addition of H2O2 inhibitor, dimethylthiourea (DMTU) and NO synthesis inhibitor, 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO), respectively, while that in PC was weakened by addition of free calcium chelator, ethylene glycol-bis(b-aminoethylether)-N,N,N',N'-tetraacetic acid (EGTA) + calcium channel outflow inhibitor, ruthenium red (RR) + plasma membrane channel blocker La(NO3)3, but EGTA + RR did not. Results also showed that NO and Ca(2+) was lying downstream of H2O2 in drought-induced signaling. Calcium ion was also involved in the expression of C4-pepc in PC. These results suggested that PC could improve oxidative tolerance in suspension-cultured cells and the acquisition of this tolerance required downregulation of H2O2 and the entry of extracellular Ca(2+) into cells across the plasma membrane for regulation of PEPC activity and C4-pepc expression. © 2014 Institute of Botany, Chinese Academy of Sciences.

  10. Experimental and theoretical identification of the Fe(vii) oxidation state in FeO4.

    PubMed

    Lu, Jun-Bo; Jian, Jiwen; Huang, Wei; Lin, Hailu; Li, Jun; Zhou, Mingfei

    2016-11-16

    The experimentally known highest oxidation state of iron has been determined to be Fe(vi) so far. Here we report a combined matrix-isolation infrared spectroscopic and theoretical study of two interconvertible iron oxide anions: a dioxoiron peroxide complex [(η 2 -O 2 )FeO 2 ] - with a C 2v -structure and a tetroxide FeO 4 - with a D 2d tetrahedral structure, which are formed by co-condensation of laser-ablated iron atoms and electrons with O 2 /Ar mixtures at 4 K. Quantum chemistry theoretical studies indicate that the Jahn-Teller distorted tetroxide FeO 4 - anion is a d 1 species with hereto the highest iron formal oxidation state Fe(vii).

  11. SnO2/TiO2 bilayer thin films exhibiting superhydrophilic properties

    NASA Astrophysics Data System (ADS)

    Talinungsang, Nibedita Paul; Purkayastha, Debarun Dhar

    2017-05-01

    Nanostructured thin films of TiO2, SnO2, and SnO2/TiO2 have been deposited by sol-gel method. The films are characterized by X-ray diffraction, wettability and optical properties. In the present work, we have achieved a way of converting hydrophilic to super-hydrophilic state by incorporating TiO2 buffer layer in between substrate and SnO2 film, which has its utility in anti-fogging surfaces. The decrease in contact angle of water over SnO2/TiO2 bilayer is attributed to the increase in roughness of the film as well as surface energy of the substrate.

  12. Hilarionite, Fe{2/3+}(SO4)(AsO4)(OH) · 6H2O, a new supergene mineral from Lavrion, Greece

    NASA Astrophysics Data System (ADS)

    Pekov, I. V.; Chukanov, N. V.; Yapaskurt, V. O.; Rusakov, V. S.; Belakovsky, D. I.; Turchkova, A. G.; Voudouris, P.; Magganas, A.; Katerinopoulos, A.

    2014-12-01

    A new mineral, hilarionite, ideally Fe{2/3+} (SO4)(AsO4)(OH) · 6H2O, has been found in the Hilarion Mine, Agios Konstantinos, Kamariza, Lavrion district, Attiki Prefecture, Greece. It was formed in the oxidation zone of a sulfide-rich orebody in association with goethite, gypsum, bukovskyite, jarosite, melanterite, chalcanthite, allophane, and azurite. Hilarionite occurs as light green (typically with an olive or grayish tint) to light yellowish green spherulites (up to 1 mm in size) and bunches of prismatic to acicular "individuals" up to 0.5 mm long that are in fact near-parallel or divergent aggregates of very thin, curved fibers up to 0.3 mm long and usually lesser than 2 μm thick. The luster is silky to vitreous. The Mohs' hardness is ca. 2. Hilarionite is ductile, its "individuals" are flexible and inelastic; fracture is uneven or splintery. D(meas) = 2.40(5), D(calc) = 2.486 g/cm3. IR spectrum shows the presence of arsenate and sulfate groups and H2O molecules in significant amounts. The Mössbauer spectrum indicates the presence of Fe3+ at two six-fold coordinated sites and the absence of Fe2+. Hilarionite is optically biaxial (+), α = 1.575(2), γ = 1.64(2), 2 V is large. The chemical composition (electron microprobe, average of 7 point analyses; H2O determined by modified Penfield method) is as follows, wt %: 0.03 MnO, 0.18 CuO, 0.17 ZnO, 33.83 Fe2O3, 0.22 P2O5, 18.92 As2O5, 22.19 SO3, 26.3 H2O, total is 101.82%. The empirical formula calculated on the basis of 15 O is: (Fe{1.90/3+}Cu0.01Zn0.01)Σ1.92[(SO4)1.24(AsO4)0.74(PO4)0.01]Σ1.99(OH)1.01 · 6.03H2O. The X-ray powder diffraction data show close structural relationship of hilarionite and kaňkite, Fe{2/3+}(AsO4)2 · 7H2O. Hilarionite is monoclinic, space group C2/ m, Cm or C2, a = 18.53(4), b = 17.43(3), c = 7.56(1) Å, β = 94.06(15)°, V = 2436(3) Å3, Z = 8. The strongest reflections in the X-ray powder diffraction pattern ( d, Å- I[ hkl]) are: 12.66-100[110], , 5.00-10[22l], , 4

  13. Low-cost flexible supercapacitors with high-energy density based on nanostructured MnO2 and Fe2O3 thin films directly fabricated onto stainless steel.

    PubMed

    Gund, Girish S; Dubal, Deepak P; Chodankar, Nilesh R; Cho, Jun Y; Gomez-Romero, Pedro; Park, Chan; Lokhande, Chandrakant D

    2015-07-24

    The facile and economical electrochemical and successive ionic layer adsorption and reaction (SILAR) methods have been employed in order to prepare manganese oxide (MnO2) and iron oxide (Fe2O3) thin films, respectively with the fine optimized nanostructures on highly flexible stainless steel sheet. The symmetric and asymmetric flexible-solid-state supercapacitors (FSS-SCs) of nanostructured (nanosheets for MnO2 and nanoparticles for Fe2O3) electrodes with Na2SO4/Carboxymethyl cellulose (CMC) gel as a separator and electrolyte were assembled. MnO2 as positive and negative electrodes were used to fabricate symmetric SC, while the asymmetric SC was assembled by employing MnO2 as positive and Fe2O3 as negative electrode. Furthermore, the electrochemical features of symmetric and asymmetric SCs are systematically investigated. The results verify that the fabricated symmetric and asymmetric FSS-SCs present excellent reversibility (within the voltage window of 0-1 V and 0-2 V, respectively) and good cycling stability (83 and 91%, respectively for 3000 of CV cycles). Additionally, the asymmetric SC shows maximum specific capacitance of 92 Fg(-1), about 2-fold of higher energy density (41.8 Wh kg(-1)) than symmetric SC and excellent mechanical flexibility. Furthermore, the "real-life" demonstration of fabricated SCs to the panel of SUK confirms that asymmetric SC has 2-fold higher energy density compare to symmetric SC.

  14. Low-cost flexible supercapacitors with high-energy density based on nanostructured MnO2 and Fe2O3 thin films directly fabricated onto stainless steel

    PubMed Central

    Gund, Girish S.; Dubal, Deepak P.; Chodankar, Nilesh R.; Cho, Jun Y.; Gomez-Romero, Pedro; Park, Chan; Lokhande, Chandrakant D.

    2015-01-01

    The facile and economical electrochemical and successive ionic layer adsorption and reaction (SILAR) methods have been employed in order to prepare manganese oxide (MnO2) and iron oxide (Fe2O3) thin films, respectively with the fine optimized nanostructures on highly flexible stainless steel sheet. The symmetric and asymmetric flexible-solid-state supercapacitors (FSS-SCs) of nanostructured (nanosheets for MnO2 and nanoparticles for Fe2O3) electrodes with Na2SO4/Carboxymethyl cellulose (CMC) gel as a separator and electrolyte were assembled. MnO2 as positive and negative electrodes were used to fabricate symmetric SC, while the asymmetric SC was assembled by employing MnO2 as positive and Fe2O3 as negative electrode. Furthermore, the electrochemical features of symmetric and asymmetric SCs are systematically investigated. The results verify that the fabricated symmetric and asymmetric FSS-SCs present excellent reversibility (within the voltage window of 0–1 V and 0–2 V, respectively) and good cycling stability (83 and 91%, respectively for 3000 of CV cycles). Additionally, the asymmetric SC shows maximum specific capacitance of 92 Fg−1, about 2-fold of higher energy density (41.8 Wh kg−1) than symmetric SC and excellent mechanical flexibility. Furthermore, the “real-life” demonstration of fabricated SCs to the panel of SUK confirms that asymmetric SC has 2-fold higher energy density compare to symmetric SC. PMID:26208144

  15. Low-cost flexible supercapacitors with high-energy density based on nanostructured MnO2 and Fe2O3 thin films directly fabricated onto stainless steel

    NASA Astrophysics Data System (ADS)

    Gund, Girish S.; Dubal, Deepak P.; Chodankar, Nilesh R.; Cho, Jun Y.; Gomez-Romero, Pedro; Park, Chan; Lokhande, Chandrakant D.

    2015-07-01

    The facile and economical electrochemical and successive ionic layer adsorption and reaction (SILAR) methods have been employed in order to prepare manganese oxide (MnO2) and iron oxide (Fe2O3) thin films, respectively with the fine optimized nanostructures on highly flexible stainless steel sheet. The symmetric and asymmetric flexible-solid-state supercapacitors (FSS-SCs) of nanostructured (nanosheets for MnO2 and nanoparticles for Fe2O3) electrodes with Na2SO4/Carboxymethyl cellulose (CMC) gel as a separator and electrolyte were assembled. MnO2 as positive and negative electrodes were used to fabricate symmetric SC, while the asymmetric SC was assembled by employing MnO2 as positive and Fe2O3 as negative electrode. Furthermore, the electrochemical features of symmetric and asymmetric SCs are systematically investigated. The results verify that the fabricated symmetric and asymmetric FSS-SCs present excellent reversibility (within the voltage window of 0-1 V and 0-2 V, respectively) and good cycling stability (83 and 91%, respectively for 3000 of CV cycles). Additionally, the asymmetric SC shows maximum specific capacitance of 92 Fg-1, about 2-fold of higher energy density (41.8 Wh kg-1) than symmetric SC and excellent mechanical flexibility. Furthermore, the “real-life” demonstration of fabricated SCs to the panel of SUK confirms that asymmetric SC has 2-fold higher energy density compare to symmetric SC.

  16. Synthesis and characterization of nanoporous anodic oxide film on aluminum in H3PO4 + KMnO4 electrolyte mixture at different anodization conditions

    NASA Astrophysics Data System (ADS)

    Verma, Naveen; Jindal, Jitender; Singh, Krishan Chander; Mari, Bernabe

    2016-04-01

    The micro structural properties of nanoporous anodic oxide film formed in H3PO4 were highly influenced by addition of a low concentration of KMnO4 (0.0005 M) in 1 M H3PO4 solution. The KMnO4 as additive enhanced the growth rate of oxide film formation as well as thickness of pore walls. Furthermore the growth rate was found increased with increase in applied current density. The increase in temperature and lack of stirring during anodization causes the thinness of pore wall which leads to increase in pore volume. With the decrease in concentration of H3PO4 in anodizing electrolyte from 1M to 0.3 M, keeping all other conditions constant, the decrease in porosity was observed. This might be due to the dissolution of aluminium oxide film in highly concentrated acidic solution.

  17. Stability of sputter deposited cuprous oxide (Cu2O) subjected to ageing conditions for photovoltaic applications

    NASA Astrophysics Data System (ADS)

    Camacho-Espinosa, E.; Rimmaudo, I.; Riech, I.; Mis-Fernández, R.; Peña, J. L.

    2018-02-01

    Among various metal oxide p-type semiconductors, cuprous oxide (Cu2O) stands out as a nontoxic and abundant material, which also makes it a suitable candidate as a low-cost absorber for photovoltaic applications. However, the chemical stability of the absorber layer is critical for the solar cell lifetime, in particular, for Cu-based materials, concerning to its oxidation state changes. In this paper, we addressed the Cu2O stability depositing films of 170 nm by reactive radio frequency magnetron sputtering and subsequently ageing them in conditions similar to the typical accelerated life test for the solar module, in a period of time from one to five weeks. The stability of the optical, electrical, and structural properties of the Cu2O thin films was investigated using UV-VIS-near infrared transmittance, 4-probes electrical resistance characterization, high precision profilometry, X-ray photoelectron spectroscopy, and grazing incidence X-ray diffraction. Finally, we demonstrated that the aging tests affected only the surface of the films, while the bulk remained unaltered, making Cu2O a promising candidate for production of stable devices, including solar cells.

  18. High-κ TiO{sub 2} thin film prepared by sol-gel spin-coating method

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kumar, Arvind; Mondal, Sandip; Rao, K. S. R. Koteswara, E-mail: ksrkrao@physics.iisc.ernet.in

    2015-06-24

    High-k TiO{sub 2} thin film on p-type silicon substrate was fabricated by a combined sol-gel and spin coating method. Thus deposited titania film had anatase phase with a small grain size of 16 nm and surface roughness of ≅ 0.6 nm. The oxide capacitance (C{sub ox}), flat band capacitance (C{sub FB}), flat band voltage (V{sub FB}), oxide trapped charge (Q{sub ot}), calculated from the high frequency (1 MHz) C-V curve were 0.47 nF, 0.16 nF, − 0.91 V, 4.7x10{sup −12} C, respectively. As compared to the previous reports, a high dielectric constant of 94 at 1 MHz frequency was observedmore » in the devices investigated here and an equivalent oxide thickness (EOT) was 4.1 nm. Dispersion in accumulation capacitance shows a linear relationship with AC frequencies. Leakage current density was found in acceptable limits (2.1e-5 A/cm{sup 2} for −1 V and 5.7e-7 A/cm{sup 2} for +1 V) for CMOS applications.« less

  19. Hybrid supercapacitor devices based on MnCo2O4 as the positive electrode and FeMn2O4 as the negative electrode

    NASA Astrophysics Data System (ADS)

    Nagamuthu, Sadayappan; Vijayakumar, Subbukalai; Lee, Seong-Hun; Ryu, Kwang-Sun

    2016-12-01

    MnCo2O4 nanosheets and FeMn2O4 nanospheres were synthesized using a hydrothermal method. Choline chloride was used as the capping agent during the preparation of the nanoparticles. XRD patterns confirmed the spinel structure of MnCo2O4 and FeMn2O4. XPS measurements were used to determine the oxidation state of the prepared spinel metal oxides. HRTEM images revealed the formation of hexagonal nanosheets of MnCo2O4 and nanospheres of FeMn2O4. Electrochemical measurements were made for both positive and negative electrodes using three electrode systems. MnCo2O4 Exhibits 282C g-1 and FeMn2O4 yields 110C g-1 at a specific current of 1 A g-1. Hybrid supercapacitor device was fabricated using MnCo2O4 as the positive and FeMn2O4 as the negative electrode material. The hybrid supercapacitor device was delivered a maximum power of 37.57 kW kg-1.

  20. Experimental thermochemistry of neptunium oxides: Np2O5 and NpO2

    NASA Astrophysics Data System (ADS)

    Zhang, Lei; Dzik, Ewa A.; Sigmon, Ginger E.; Szymanowski, Jennifer E. S.; Navrotsky, Alexandra; Burns, Peter C.

    2018-04-01

    Neptunium (Np) compounds are important in the nuclear fuel cycle because of the buildup and long half-life (2.14 Ma) of Np-237 in nuclear waste, especially during long-term disposal in a geological repository. Neptunium in environmental conditions exists mainly in two oxidation states (+5 and + 4) and can substitute for uranium and/or rare earths in solid phases. Yet thermochemical data for solid neptunium compounds are scarce, despite being critical for evaluating the environmental transport of this radioactive and toxic element. Although high temperature oxide melt solution calorimetry has proven very useful in obtaining thermodynamic data for the formation of uranium and thorium oxide materials, it has not yet been applied to transuranium compounds. Continuing a program at Notre Dame to study the thermodynamics of transuranium compounds, we report the first determination of the enthalpies of drop solution of well-characterized neptunium oxides (Np2O5 and NpO2) using oxide melt solution calorimetry in molten sodium molybdate solvent at 973 K. The enthalpy of the decomposition reaction, Np2O5(cr) = 2NpO2(cr) + 1/2O2(g) at 298 K, is determined to be 7.70 ± 5.86 kJ/mol, and this direct measurement is consistent with existing thermodynamic data. The calorimetric methodology is straightforward and produces reliable data using milligram quantities of radioactive materials, and can be applied to many other transuranium compounds.

  1. Atomic layer deposition and properties of ZrO2/Fe2O3 thin films

    PubMed Central

    Seemen, Helina; Ritslaid, Peeter; Rähn, Mihkel; Tamm, Aile; Kukli, Kaupo; Kasikov, Aarne; Link, Joosep; Stern, Raivo; Dueñas, Salvador; Castán, Helena; García, Héctor

    2018-01-01

    Thin solid films consisting of ZrO2 and Fe2O3 were grown by atomic layer deposition (ALD) at 400 °C. Metastable phases of ZrO2 were stabilized by Fe2O3 doping. The number of alternating ZrO2 and Fe2O3 deposition cycles were varied in order to achieve films with different cation ratios. The influence of annealing on the composition and structure of the thin films was investigated. Additionally, the influence of composition and structure on electrical and magnetic properties was studied. Several samples exhibited a measurable saturation magnetization and most of the samples exhibited a charge polarization. Both phenomena were observed in the sample with a Zr/Fe atomic ratio of 2.0. PMID:29441257

  2. Nanostructural Tailoring to Induce Flexibility in Thermoelectric Ca3Co4O9 Thin Films

    PubMed Central

    2017-01-01

    Because of their inherent rigidity and brittleness, inorganic materials have seen limited use in flexible thermoelectric applications. On the other hand, for high output power density and stability, the use of inorganic materials is required. Here, we demonstrate a concept of fully inorganic flexible thermoelectric thin films with Ca3Co4O9-on-mica. Ca3Co4O9 is promising not only because of its high Seebeck coefficient and good electrical conductivity but also because of the abundance, low cost, and nontoxicity of its constituent raw materials. We show a promising nanostructural tailoring approach to induce flexibility in inorganic thin-film materials, achieving flexibility in nanostructured Ca3Co4O9 thin films. The films were grown by thermally induced phase transformation from CaO–CoO thin films deposited by reactive rf-magnetron cosputtering from metallic targets of Ca and Co to the final phase of Ca3Co4O9 on a mica substrate. The pattern of nanostructural evolution during the solid-state phase transformation is determined by the surface energy and strain energy contributions, whereas different distributions of CaO and CoO phases in the as-deposited films promote different nanostructuring during the phase transformation. Another interesting fact is that the Ca3Co4O9 film is transferable onto an arbitrary flexible platform from the parent mica substrate by etch-free dry transfer. The highest thermoelectric power factor obtained is above 1 × 10–4 W m–1 K–2 in a wide temperature range, thus showing low-temperature applicability of this class of materials. PMID:28699345

  3. Influence of an O2 background gas on the composition and kinetic energies of species in laser induced La0.4Ca0.6MnO3 plasmas

    NASA Astrophysics Data System (ADS)

    Chen, Jikun; Stender, Dieter; Bator, Matthias; Schneider, Christof W.; Lippert, Thomas; Wokaun, Alexander

    2013-08-01

    Oxygen is one of the most commonly used background gases for pulsed laser deposition of oxide thin films. In this work the properties of a 308 nm laser-induced La0.4Ca0.6MnO3 plasma were analyzed using a quadrupole mass spectrometer combined with an energy analyzer, to investigate the interaction between the various plasma species and the background gas. The composition and kinetic energies of the plasma species were compared in vacuum and an O2 background gas at different pressures. It has been observed that the O2 background gas decreases the kinetic energy of the positively charged atomic plasma species. In addition, the interaction with the O2 background gas causes the generation of positive diatomic oxide species of LaO+, CaO+ and MnO+. The amount of negatively charged diatomic or tri-atomic oxide species decreases in the O2 background compared to vacuum, while the amount of O2- increases strongly.

  4. An innovative concept of use of redox-active electrolyte in asymmetric capacitor based on MWCNTs/MnO2 and Fe2O3 thin films

    PubMed Central

    Chodankar, Nilesh R.; Dubal, Deepak P.; Lokhande, Abhishek C.; Patil, Amar M.; Kim, Jin H.; Lokhande, Chandrakant D.

    2016-01-01

    In present investigation, we have prepared a nanocomposites of highly porous MnO2 spongy balls and multi-walled carbon nanotubes (MWCNTs) in thin film form and tested in novel redox-active electrolyte (K3[Fe(CN)6] doped aqueous Na2SO4) for supercapacitor application. Briefly, MWCNTs were deposited on stainless steel substrate by “dip and dry” method followed by electrodeposition of MnO2 spongy balls. Further, the supercapacitive properties of these hybrid thin films were evaluated in hybrid electrolyte ((K3[Fe(CN)6 doped aqueous Na2SO4). Thus, this is the first proof-of-design where redox-active electrolyte is applied to MWCNTs/MnO2 hybrid thin films. Impressively, the MWCNTs/MnO2 hybrid film showed a significant improvement in electrochemical performance with maximum specific capacitance of 1012 Fg−1 at 2 mA cm−2 current density in redox-active electrolyte, which is 1.5-fold higher than that of conventional electrolyte (Na2SO4). Further, asymmetric capacitor based on MWCNTs/MnO2 hybrid film as positive and Fe2O3 thin film as negative electrode was fabricated and tested in redox-active electrolytes. Strikingly, MWCNTs/MnO2//Fe2O3 asymmetric cell showed an excellent supercapacitive performance with maximum specific capacitance of 226 Fg−1 and specific energy of 54.39 Wh kg−1 at specific power of 667 Wkg−1. Strikingly, actual practical demonstration shows lightning of 567 red LEDs suggesting “ready-to sell” product for industries. PMID:27982087

  5. An innovative concept of use of redox-active electrolyte in asymmetric capacitor based on MWCNTs/MnO2 and Fe2O3 thin films.

    PubMed

    Chodankar, Nilesh R; Dubal, Deepak P; Lokhande, Abhishek C; Patil, Amar M; Kim, Jin H; Lokhande, Chandrakant D

    2016-12-16

    In present investigation, we have prepared a nanocomposites of highly porous MnO 2 spongy balls and multi-walled carbon nanotubes (MWCNTs) in thin film form and tested in novel redox-active electrolyte (K 3 [Fe(CN) 6 ] doped aqueous Na 2 SO 4 ) for supercapacitor application. Briefly, MWCNTs were deposited on stainless steel substrate by "dip and dry" method followed by electrodeposition of MnO 2 spongy balls. Further, the supercapacitive properties of these hybrid thin films were evaluated in hybrid electrolyte ((K 3 [Fe(CN) 6 doped aqueous Na 2 SO 4 ). Thus, this is the first proof-of-design where redox-active electrolyte is applied to MWCNTs/MnO 2 hybrid thin films. Impressively, the MWCNTs/MnO 2 hybrid film showed a significant improvement in electrochemical performance with maximum specific capacitance of 1012 Fg -1 at 2 mA cm -2 current density in redox-active electrolyte, which is 1.5-fold higher than that of conventional electrolyte (Na 2 SO 4 ). Further, asymmetric capacitor based on MWCNTs/MnO 2 hybrid film as positive and Fe 2 O 3 thin film as negative electrode was fabricated and tested in redox-active electrolytes. Strikingly, MWCNTs/MnO 2 //Fe 2 O 3 asymmetric cell showed an excellent supercapacitive performance with maximum specific capacitance of 226 Fg -1 and specific energy of 54.39 Wh kg -1 at specific power of 667 Wkg -1 . Strikingly, actual practical demonstration shows lightning of 567 red LEDs suggesting "ready-to sell" product for industries.

  6. Compact chromium oxide thin film resistors for use in nanoscale quantum circuits

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Nash, C. R.; Fenton, J. C.; Constantino, N. G. N.

    We report on the electrical characterisation of a series of thin amorphous chromium oxide (CrO{sub x}) films, grown by dc sputtering, to evaluate their suitability for use as on-chip resistors in nanoelectronics. By increasing the level of oxygen doping, the room-temperature sheet resistance of the CrO{sub x} films was varied from 28 Ω/◻ to 32.6 kΩ/◻. The variation in resistance with cooling to 4.2 K in liquid helium was investigated; the sheet resistance at 4.2 K varied with composition from 65 Ω/◻ to above 20 GΩ/◻. All of the films measured displayed linear current–voltage characteristics at all measured temperatures. For on-chip devices for quantummore » phase-slip measurements using niobium–silicon nanowires, interfaces between niobium–silicon and chromium oxide are required. We also characterised the contact resistance for one CrO{sub x} composition at an interface with niobium–silicon. We found that a gold intermediate layer is favourable: the specific contact resistivity of chromium-oxide-to-gold interfaces was 0.14 mΩcm{sup 2}, much lower than the value for direct CrO{sub x} to niobium–silicon contact. We conclude that these chromium oxide films are suitable for use in nanoscale circuits as high-value resistors, with resistivity tunable by oxygen content.« less

  7. Orbital engineering near La2 NiO 4- La2 CuO 4 superlattice interfaces

    NASA Astrophysics Data System (ADS)

    Smadici, S.; Lee, J. C. T.; Morales, J.; Abbamonte, P.; Logvenov, G.; Gozar, A.; Bozovic, I.

    2011-03-01

    Orbital states of transition metal oxides present the opportunity of adjusting material properties to a specific purpose (orbital engineering). A comparison of the resonant soft x-ray reflectivity of La 2 Ni O4 - La 2 Cu O4 superlattices at Ni L and Cu L edges shows different spatial distributions of the occupation of Ni d x 2 -y 2 and d 3z 2 -r 2 orbitals in the LNO layers. This modulation of the Ni valence is possible through a pronounced modulation of the density of oxygen interstitial dopants within the structure which does not follow exactly the structure itself. This is the first observation of orbital engineering in a 214 oxide. This work was supported by Grants DE-FG02-06ER46285, DE-AC02-98CH10886, MA-509-MACA, DE-FG02-07ER46453 and DE-FG02-07ER46471.

  8. Structural, electrical and optical properties of nanostructured ZrO2 thin film deposited by SILAR method

    NASA Astrophysics Data System (ADS)

    Salodkar, R. V.; Belkhedkar, M. R.; Nemade, S. D.

    2018-05-01

    Successive Ionic Layer Adsorption and Reaction (SILAR) method has been employed to deposit nanocrystalline ZrO2 thin film of thickness 91 nm onto glass substrates using ZrOCl2.8H2O and NaOH as cationic and anionic precursors respectively. The structural and surface morphological characterizations have been carried out by means of X-ray diffraction and field emission scanning electron microscopy confirms the nanocrystalline nature of ZrO2 thin film. The direct optical band gap and activation energy of the ZrO2 thin film are found to be 4.74 and 0.80eV respectively.

  9. Ultrafast electron-lattice coupling dynamics in VO2 and V2O3 thin films

    NASA Astrophysics Data System (ADS)

    Abreu, Elsa; Gilbert Corder, Stephanie N.; Yun, Sun Jin; Wang, Siming; Ramírez, Juan Gabriel; West, Kevin; Zhang, Jingdi; Kittiwatanakul, Salinporn; Schuller, Ivan K.; Lu, Jiwei; Wolf, Stuart A.; Kim, Hyun-Tak; Liu, Mengkun; Averitt, Richard D.

    2017-09-01

    Ultrafast optical pump-optical probe and optical pump-terahertz probe spectroscopy were performed on vanadium dioxide (VO2) and vanadium sesquioxide (V2O3 ) thin films over a wide temperature range. A comparison of the experimental data from these two different techniques and two different vanadium oxides, in particular a comparison of the spectral weight oscillations generated by the photoinduced longitudinal acoustic modulation, reveals the strong electron-phonon coupling that exists in both materials. The low-energy Drude response of V2O3 appears more amenable than VO2 to ultrafast strain control. Additionally, our results provide a measurement of the temperature dependence of the sound velocity in both systems, revealing a four- to fivefold increase in VO2 and a three- to fivefold increase in V2O3 across the insulator-to-metal phase transition. Our data also confirm observations of strong damping and phonon anharmonicity in the metallic phase of VO2, and suggest that a similar phenomenon might be at play in the metallic phase of V2O3 . More generally, our simple table-top approach provides relevant and detailed information about dynamical lattice properties of vanadium oxides, paving the way to similar studies in other complex materials.

  10. The Obtaining of Nano Oxide Systems SiO2-REE with Alkoxide Technology

    NASA Astrophysics Data System (ADS)

    Amelina, Anna; Grinberg, Evgenii

    A lot of oxides systems with REE as dopants are used in catalytic processes in organic synthesis. They are very perspectives as thermostable coating in aerospace technics. These systems are usually based on silicon or aluminium oxides and doped with rare-earth elements. This systems can be produced by different methods. One of the most perspective of them is “sol-gel”-method with silicium, aluminium and rare-earth alkoxides as a precursor of doped silica and alumina, or their derivatives. Thus the obtaining of composite SiO _{2} - REE oxide materials by the hydrolysis doped with rare-earth elements was suggested. Some of alcoholate derivatives such as El(OR)n were used in this processes. The SiO _{2}- REE oxides were precipitated during the sol-gel process, where tetraethoxysilane (TEOS) as used as SiO _{2} sources. Also it is known that alkoxides of alkali metals, including lithium alkoxides, are widely used in industry and synthetic chemistry, as well as a source of lithium in various mixed oxide compositions, such as lithium niobate, lithium tantalate or lithium silicate. Therefore, we attempted to obtain the lithium silicate, which is also doped with rare-earth elements. Lithium silicate was obtained by alkaline hydrolysis of tetraethoxysilane with lithium alkoxide. Lithium alkoxide were synthesized by dissolving at metal in the corresponding alcohol are examined. The dependence of the rate of dissolving of the metal on the method of mixing of the reaction mixture and the degree of metal dispersion was investigated. The mathematical model of the process was composed and also optimization of process was carried out. Some oxide SiO _{2}, Al _{2}O _{3} and rare-earth nanostructured systems were obtained by sol-gel-method. The size of particle was determined by electron and X-ray spectroscopy and was in the range of 5 - 15 nm. Purity of this oxide examples for contaminating of heavy metals consists n.(1E-4...1E-5) wt%. Sols obtained by this method may be used

  11. Damage evolution of ion irradiated defected-fluorite La 2 Zr 2 O 7 epitaxial thin films

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kaspar, Tiffany C.; Gigax, Jonathan G.; Shao, Lin

    2017-05-01

    Pyrochlore-structure oxides, A2B2O7, may exhibit remarkable radiation tolerance due to the ease with which they can accommodate disorder by transitioning to a defected fluorite structure. The mechanism of defect formation was explored by evaluating the radiation damage behavior of high quality epitaxial La2Zr2O7 thin films with the defected fluorite structure, irradiated with 1 MeV Zr+ at doses up to 10 displacements per atom (dpa). The level of film damage was evaluated as a function of dose by Rutherford backscattering spectrometry in the channeling geometry (RBS/c) and scanning transmission electron microscopy (STEM). At lower doses, the surface of the La2Zr2O7 filmmore » amorphized, and the amorphous fraction as a function of dose fit well to a stimulated amorphization model. As the dose increased, the surface amorphization slowed, and amorphization appeared at the interface. Even at a dose of 10 dpa, the core of the film remained crystalline, despite the prediction of amorphization from the model. To inform future ab initio simulations of La2Zr2O7, the bandgap of a thick La2Zr2O7 film was measured to be indirect at 4.96 eV, with a direct transition at 5.60 eV.« less

  12. Damage evolution of ion irradiated defected-fluorite La 2 Zr 2 O 7 epitaxial thin films

    DOE PAGES

    Kaspar, Tiffany C.; Gigax, Jonathan G.; Shao, Lin; ...

    2017-05-01

    Pyrochlore-structure oxides, A 2B 2O 7, may exhibit remarkable radiation tolerance due to the ease with which they can accommodate disorder by transitioning to a defected fluorite structure. In this paper, the mechanism of defect formation was explored by evaluating the radiation damage behavior of high quality epitaxial La 2Zr 2O 7 thin films with the defected fluorite structure, irradiated with 1 MeV Zr + at doses up to 10 displacements per atom (dpa). The level of film damage was evaluated as a function of dose by Rutherford backscattering spectrometry in the channeling geometry (RBS/c) and scanning transmission electron microscopymore » (STEM). At lower doses, the surface of the La 2Zr 2O 7 film amorphized, and the amorphous fraction as a function of dose fit well to a stimulated amorphization model. As the dose increased, the surface amorphization slowed, and amorphization appeared at the interface. Even at a dose of 10 dpa, the core of the film remained crystalline, despite the prediction of amorphization from the model. To inform future ab initio simulations of La 2Zr 2O 7, the bandgap of a thick La 2Zr 2O 7 film was measured to be indirect at 4.96 eV, with a direct transition at 5.60 eV.« less

  13. Synthesis and microstructural TEM investigation of CaCu{sub 3}Ru{sub 4}O{sub 12} ceramic and thin film

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Brize, Virginie; STMicroelectronics, 16 rue P and M Curie, 37001 Tours; Autret-Lambert, Cecile, E-mail: cecile.autret-lambert@univ-tours.fr

    2011-10-15

    CaCu{sub 3}Ru{sub 4}O{sub 12} (CCRO) is a conductive oxide having the same structure as CaCu{sub 3}Ti{sub 4}O{sub 12} (CCTO) and close lattice parameters. The later compound is strongly considered for high density parallel plates capacitors application due to its so-called colossal dielectric constant. The need for an electrode inducing CCTO epitaxial growth with a clean and sharp interface is therefore necessary, and CCRO is a good potential candidate. In this paper, the synthesis of monophasic CCRO ceramic is reported, as well as pulsed laser deposition of CCRO thin film onto (001) NdCaAlO{sub 4} substrate. Structural and physical properties of bulkmore » CCRO were studied by transmission electron microscopy and electron spin resonance. CCRO films and ceramic exhibited a metallic behavior down to low temperature. CCRO films were (001) oriented and promoted a CCTO film growth with the same orientation. - Graphical Abstract: Structure of CaCu{sub 3}Ru{sub 4}O{sub 12} showing the RuO{sub 6} octahedra and the square planar environment for Cu{sup 2+}. Highlights: > In this study, we investigate the structural properties and microstructure of ceramics CaCu{sub 3}Ru{sub 4}O{sub 12}. > We study the conduction properties of polycrystalline material. > Then we synthesize the conductive thin film which is deposited on a high K material with the same structure (CaCu{sub 3}Ti{sub 4}O{sub 12}).« less

  14. Oxidation of dimethylselenide by δMnO2: oxidation product and factors affecting oxidation rate

    USGS Publications Warehouse

    Wang, Bronwen; Burau, Richard G.

    1995-01-01

    Volatile dimethylselenide (DMSe) was transformed to a nonvolatile Se compound in a ??-MnO2 suspension. The nonvolatile product was a single compound identified as dimethylselenoxide based on its mass spectra pattern. After 24 h, 100% of the DMSe added to a ??-MnO2 suspension was converted to nonpurgable Se as opposed to 20%, 18%, and 4% conversion for chromate, permanganate, and the filtrate from the suspension, respectively. Manganese was found in solution after reaction. These results imply that the reaction between manganese oxide and DMSe was a heterogeneous redox reaction involving solid phase ??-MnO2 and solution phase DMSe. Oxidation of DMSe to dimethylselenoxide [OSe(CH3)2] by a ??-MnO2 suspension appears to be first order with respect to ??-MnO2, to DMSe, and to hydrogen ion with an overall rate law of d[OSe(CH3)2 ]/dt = 95 M-2 min-1 [MnO2]1[DMSe]1[H+]1 for the MnO2 concentration range of 0.89 ?? 10-3 - 2.46 ?? 10-3 M, the DMSe concentration range of 3.9 ?? 10-7 - 15.5 ?? 10-7 M Se, and a hydrogen ion concentation range of 7.4 ?? 10-6 -9.5 ?? 10-8 M. A general surface site adsorption model is consistent with this rate equation if the uncharged |OMnOH is the surface adsorption site. DMSe acts as a Lewis base, and the manganese oxide surface acts as a Lewis acid. DMSe adsorption to |OMnOH can be viewed as a Lewis acid/ base complex between the largely p orbitals of the DMSe lone pair and the unoccupied eg orbitals on manganese oxide. For such a complex, frontier molecular orbital theory predicts electron transfer to occur via an inner-sphere complex between the DMSe and the manganese oxide. ?? 1995 American Chemical Society.

  15. Engineering epitaxial γ-Al2O3 gate dielectric films on 4H-SiC

    NASA Astrophysics Data System (ADS)

    Tanner, Carey M.; Toney, Michael F.; Lu, Jun; Blom, Hans-Olof; Sawkar-Mathur, Monica; Tafesse, Melat A.; Chang, Jane P.

    2007-11-01

    The formation of epitaxial γ-Al2O3 thin films on 4H-SiC was found to be strongly dependent on the film thickness. An abrupt interface was observed in films up to 200 Å thick with an epitaxial relationship of γ-Al2O3(111)‖4H-SiC(0001) and γ-Al2O3(44¯0)‖4H-SiC(112¯0). The in-plane alignment between the film and the substrate is nearly complete for γ-Al2O3 films up to 115 Å thick, but quickly diminishes in thicker films. The films are found to be slightly strained laterally in tension; the strain increases with thickness and then decreases in films thicker than 200 Å, indicating strain relaxation which is accompanied by increased misorientation. By controlling the structure of ultrathin Al2O3 films, metal-oxide-semiconductor capacitors with Al2O3 gate dielectrics on 4H-SiC were found to have a very low leakage current density, suggesting suitability of Al2O3 for SiC device integration.

  16. Room temperature multiferroic properties of (Bi{sub 0.95}La{sub 0.05})(Fe{sub 0.97}Mn{sub 0.03})O{sub 3}/NiFe{sub 2}O{sub 4} double layered thin film

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Raghavan, C.M.; Kim, H.J.; Kim, J.W.

    2013-11-15

    Graphical abstract: - Highlights: • Chemical solution deposition of (Bi{sub 0.95}La{sub 0.05})(Fe{sub 0.97}Mn{sub 0.03})O{sub 3}–NiFe{sub 2}O{sub 4} double layered thin film. • Studies on structural, electrical and multiferroic properties. • NiFe{sub 2}O{sub 4} acts as both resistive buffer layer and magnetic source. - Abstract: (Bi{sub 0.95}La{sub 0.05})(Fe{sub 0.97}Mn{sub 0.03})O{sub 3}/NiFe{sub 2}O{sub 4} double layered thin film was prepared on a Pt(111)/Ti/SiO{sub 2}/Si(100) substrate by a chemical solution deposition method. X-ray diffraction and Raman scattering spectroscopy studies confirmed the formation of the distorted rhombohedral perovskite and the inverse spinel cubic structures for the (Bi{sub 0.95}La{sub 0.05})(Fe{sub 0.97}Mn{sub 0.03})O{sub 3}/NiFe{sub 2}O{sub 4}more » double layered thin film. The (Bi{sub 0.95}La{sub 0.05})(Fe{sub 0.97}Mn{sub 0.03})O{sub 3}/NiFe{sub 2}O{sub 4} double layered thin film exhibited well saturated ferromagnetic (2 M{sub r} of 18.1 emu/cm{sup 3} and 2H{sub c} of 0.32 kOe at 20 kOe) and ferroelectric (2P{sub r} of 60 μC/cm{sup 2} and 2E{sub c} of 813 kV/cm at 866 kV/cm) hysteresis loops with low order of leakage current density (4.5 × 10{sup −6} A/cm{sup 2} at an applied electric field of 100 kV/cm), which suggest the ferroelectric and ferromagnetic multi-layers applications in real devices.« less

  17. Chemical obtaining of LiMO2 and LiM2O4 (M=Co, Mn) oxides, for cathodic applications in Li-ion batteries

    NASA Astrophysics Data System (ADS)

    Y Neira-Guio, A.; Gómez Cuaspud, J. A.; López, E. Vera; Pineda Triana, Y.

    2017-12-01

    This paper describes the synthesis and characterization of two spinel and olivine-type multicomponent oxides based on LiMO2 and LiM2O4 systems (M=Co and Mn), which represent the current state of the art in the development of cathodes for Li-ion batteries. A simple combustion synthesis process was employed to obtain the nanometric oxides in powder form (crystal sizes around 5-8nm), with a number of improved surface characteristics. The characterization by X-Ray Diffraction (XRD), Scanning and Transmission Electron Microscopy (SEM, TEM) and X-Ray Fluorescence (XRF), allowed to evaluate the morphology and the stoichiometric compositions of solids, obtaining a concordant pure crystalline phase of LiCoO2 and LiMn2O4 oxides identified in a rhombohedral and cubic phase with punctual group R-3m (1 6 6) and Fm-3m (2 2 5) respectively. The electrical characterization of materials developed by impedance spectroscopy solid state, allowed to determine a p-type semiconducting behaviour with conductivity values of 6.2×10-3 and 2.7×10-7 S for LiCoO2 and LiMn2O4 systems, consistent with the state of the art for such materials.

  18. Mechanistic analysis of temperature-dependent current conduction through thin tunnel oxide in n+-polySi/SiO2/n+-Si structures

    NASA Astrophysics Data System (ADS)

    Samanta, Piyas

    2017-09-01

    We present a detailed investigation on temperature-dependent current conduction through thin tunnel oxides grown on degenerately doped n-type silicon (n+-Si) under positive bias ( VG ) on heavily doped n-type polycrystalline silicon (n+-polySi) gate in metal-oxide-semiconductor devices. The leakage current measured between 298 and 573 K and at oxide fields ranging from 6 to 10 MV/cm is primarily attributed to Poole-Frenkel (PF) emission of trapped electrons from the neutral electron traps located in the silicon dioxide (SiO2) band gap in addition to Fowler-Nordheim (FN) tunneling of electrons from n+-Si acting as the drain node in FLOating gate Tunnel OXide Electrically Erasable Programmable Read-Only Memory devices. Process-induced neutral electron traps are located at 0.18 eV and 0.9 eV below the SiO2 conduction band. Throughout the temperature range studied here, PF emission current IPF dominates FN electron tunneling current IFN at oxide electric fields Eox between 6 and 10 MV/cm. A physics based new analytical formula has been developed for FN tunneling of electrons from the accumulation layer of degenerate semiconductors at a wide range of temperatures incorporating the image force barrier rounding effect. FN tunneling has been formulated in the framework of Wentzel-Kramers-Brilloiun taking into account the correction factor due to abrupt variation of the energy barrier at the cathode/oxide interface. The effect of interfacial and near-interfacial trapped-oxide charges on FN tunneling has also been investigated in detail at positive VG . The mechanism of leakage current conduction through SiO2 films plays a crucial role in simulation of time-dependent dielectric breakdown of the memory devices and to precisely predict the normal operating field or applied floating gate (FG) voltage for lifetime projection of the devices. In addition, we present theoretical results showing the effect of drain doping concentration on the FG leakage current.

  19. Oxidation and hot corrosion of hot-pressed Si3N4 at 1000 deg C

    NASA Technical Reports Server (NTRS)

    Fielder, W. L.

    1985-01-01

    The oxidation and hot corrosion of a commercial, hot-pressed Si3N4 were investigated at 1000 C under an atmosphere of flowing O2. For the hot corrosion studies, thin films of Na2SO4 were airbrushed on the Si3N4 surface. The hot corrosion attack was monitored by the following techniques: continuous weight measurements, SO2 evolution, film morphology, and chemical analyses. Even though the hot corrosion weight changes after 25 hr were relatively small, the formation of SiO2 from oxidation of Si3N4 was an order of magnitude greater in the presence of molten Na2SO4. The formation of a protective SiO2 phase at the Si3N4 surface is minimized by the fluxing action of the molten Na2SO4 thereby allowing the oxidation of the Si3N4 to proceed more rapidly. A simple process is proposed to account for the hot corrosion process.

  20. Electrochemical oxidation of 2,4,5-trichlorophenoxyacetic acid by metal-oxide-coated Ti electrodes.

    PubMed

    Maharana, Dusmant; Xu, Zesheng; Niu, Junfeng; Rao, Neti Nageswara

    2015-10-01

    Electrochemical oxidation of 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) over metal-oxide-coated Ti anodes, i.e., Ti/SnO2-Sb/Ce-PbO2, Ti/SnO2-Sb and Ti/RuO2, was examined. The degradation efficiency of over 90% was attained at 20 min at different initial concentrations (0.5-20 mg L(-1)) and initial pH values (3.1-11.2). The degradation efficiencies of 2,4,5-T on Ti/SnO2-Sb/Ce-PbO2, Ti/SnO2-Sb and Ti/RuO2 anodes were higher than 99.9%, 97.2% and 91.5% at 30 min, respectively, and the respective total organic carbon removal ratios were 65.7%, 54.6% and 37.2%. The electrochemical degradation of 2,4,5-T in aqueous solution followed pseudo-first-order kinetics. The compounds, i.e., 2,5-dichlorohydroquinone and 2,5-dihydroxy-p-benzoquinone, have been identified as the main aromatic intermediates by liquid chromatography-mass spectrometry. The results showed that the energy efficiencies of 2,4,5-T (20 mg L(-1)) degradation with Ti/SnO2-Sb/Ce-PbO2 anode at the optimal current densities from 2 to 16 mA cm(-2) ranged from 8.21 to 18.73 kWh m(-3). Copyright © 2015 Elsevier Ltd. All rights reserved.

  1. Structural, XPS and magnetic studies of pulsed laser deposited Fe doped Eu{sub 2}O{sub 3} thin film

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kumar, Sandeep; Prakash, Ram, E-mail: rpgiuc@gmail.com; Choudhary, R.J.

    2015-10-15

    Highlights: • Growth of Fe doped Eu{sub 2}O{sub 3} thin films by PLD. • XRD and Raman’s spectroscopy used for structure confirmation. • The electronic states of Eu and Fe are confirmed by XPS. • Magnetic properties reveals room temperature magnetic ordering in deposited film. - Abstract: Fe (4 at.%) doped europium (III) oxide thin film was deposited on silicon (1 0 0) substrate by pulsed laser deposition technique. Structural, spectral and magnetic properties were studied by X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and magnetization measurements. XRD and Raman spectroscopy reveal that the grown film is singlemore » phased and belongs to the cubic structure of Eu{sub 2}O{sub 3}. XPS study of the Eu{sub 1.92}Fe{sub 0.08}O{sub 3} film shows that Fe exists in Fe{sup 3+} ionic state in the film. The film exhibits magnetic ordering at room temperature.« less

  2. Rapid fabrication of mesoporous TiO2 thin films by pulsed fibre laser for dye sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Hadi, Aseel; Alhabradi, Mansour; Chen, Qian; Liu, Hong; Guo, Wei; Curioni, Michele; Cernik, Robert; Liu, Zhu

    2018-01-01

    In this paper we demonstrate for the first time that a fibre laser with a wavelength of 1070 nm and a pulse width of milliseconds can be applied to generate mesoporous nanocrystalline (nc) TiO2 thin films on ITO coated glass in ambient atmosphere, by complete vaporisation of organic binder and inter-connection of TiO2 nanoparticles, without thermally damaging the ITO layer and the glass substrate. The fabrication of the mesoporous TiO2 thin films was achieved by stationary laser beam irradiation of 1 min. The dye sensitized solar cell (DSSC) with the laser-sintered TiO2 photoanode reached higher power conversion efficiency (PCE) of 3.20% for the TiO2 film thickness of 6 μm compared with 2.99% for the furnace-sintered. Electrochemical impedance spectroscopy studies revealed that the laser sintering under the optimised condition effectively decreased charge transfer resistance and increased electron lifetime of the TiO2 thin films. The use of the fibre laser with over 40% wall-plug efficiency offers an economically-feasible, industrial viable solution to the major challenge of rapid fabrication of large scale, mass production of mesoporous metal oxide thin film based solar energy systems, potentially for perovskite and monolithic tandem solar cells, in the future.

  3. Ultra-thin Oxide Membranes: Synthesis and Carrier Transport

    NASA Astrophysics Data System (ADS)

    Sim, Jai Sung

    Self-supported freestanding membranes are films that are devoid of any underlying supporting layers. The key advantage of such structures is that, due to the lack of substrate effects - both mechanical and chemical, the true native properties of the material can be probed. This is crucial since many of the studies done on materials that are used as freestanding membranes are done as films clamped to substrates or in the bulk form. This thesis focuses on the synthesis and fabrication as well as electrical studies of free standing ultrathin < 40nm oxide membranes. It also is one of the first demonstrations for electrically probing nanoscale freestanding oxide membranes. Fabrication of such membranes is non-trivial as oxide materials are often brittle and difficult to handle. Therefore, it requires an understanding of thin plate mechanics coupled with controllable thin film deposition process. Taking things a step further, to electrically probe these membranes required design of complex device architecture and extensive optimization of nano-fabrication processes. The challenges and optimized fabrication method of such membranes are demonstrated. Three materials are probed in this study, VO2, TiO2, and CeO2. VO2 for understanding structural considerations for electronic phase change and nature of ionic liquid gating, TiO2 and CeO2 for understanding surface conduction properties and surface chemistry. The VO2 study shows shift in metal-insulator transition (MIT) temperature arising from stress relaxation and opening of the hysteresis. The ionic liquid gating studies showed reversible modulation of channel resistance and allowed distinguishing bulk process from the surface effects. Comparing the ionic liquid gating experiments to hydrogen doping experiments illustrated that ionic liquid gating can be a surface limited electrostatic effect, if the critical voltage threshold is not exceeded. TiO2 study shows creation of non-stoichiometric forms under ion milling. Utilizing

  4. High Mobility Thin Film Transistors Based on Amorphous Indium Zinc Tin Oxide

    PubMed Central

    Noviyana, Imas; Lestari, Annisa Dwi; Putri, Maryane; Won, Mi-Sook; Bae, Jong-Seong; Heo, Young-Woo; Lee, Hee Young

    2017-01-01

    Top-contact bottom-gate thin film transistors (TFTs) with zinc-rich indium zinc tin oxide (IZTO) active layer were prepared at room temperature by radio frequency magnetron sputtering. Sintered ceramic target was prepared and used for deposition from oxide powder mixture having the molar ratio of In2O3:ZnO:SnO2 = 2:5:1. Annealing treatment was carried out for as-deposited films at various temperatures to investigate its effect on TFT performances. It was found that annealing treatment at 350 °C for 30 min in air atmosphere yielded the best result, with the high field effect mobility value of 34 cm2/Vs and the minimum subthreshold swing value of 0.12 V/dec. All IZTO thin films were amorphous, even after annealing treatment of up to 350 °C. PMID:28773058

  5. Heptavalent Actinide Tetroxides NpO 4 – and PuO 4 –: Oxidation of Pu(V) to Pu(VII) by Adding an Electron to PuO 4

    DOE PAGES

    Gibson, John K.; de Jong, Wibe A.; Dau, Phuong D.; ...

    2017-11-14

    The highest known actinide oxidation states are Np(VII) and Pu(VII), both of which have been identified in solution and solid compounds. Recently a molecular Np(VII) complex, NpO 3(NO 3) 2-, was prepared and characterized in the gas phase. In accord with the lower stability of heptavalent Pu, no Pu(VII) molecular species has been identified. Reported here are the gas-phase syntheses and characterizations of NpO 4 - and PuO 4 -. Reactivity studies and density functional theory computations indicate the heptavalent metal oxidation state in both. This is the first instance of Pu(VII) in the absence of stabilizing effects due tomore » condensed phase solvation or crystal fields. Here, the results indicate that addition of an electron to neutral PuO 4, which has a computed electron affinity of 2.56 eV, counterintuitively results in oxidation of Pu(V) to Pu(VII), concomitant with superoxide reduction.« less

  6. Heptavalent Actinide Tetroxides NpO 4 – and PuO 4 –: Oxidation of Pu(V) to Pu(VII) by Adding an Electron to PuO 4

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Gibson, John K.; de Jong, Wibe A.; Dau, Phuong D.

    The highest known actinide oxidation states are Np(VII) and Pu(VII), both of which have been identified in solution and solid compounds. Recently a molecular Np(VII) complex, NpO 3(NO 3) 2-, was prepared and characterized in the gas phase. In accord with the lower stability of heptavalent Pu, no Pu(VII) molecular species has been identified. Reported here are the gas-phase syntheses and characterizations of NpO 4 - and PuO 4 -. Reactivity studies and density functional theory computations indicate the heptavalent metal oxidation state in both. This is the first instance of Pu(VII) in the absence of stabilizing effects due tomore » condensed phase solvation or crystal fields. Here, the results indicate that addition of an electron to neutral PuO 4, which has a computed electron affinity of 2.56 eV, counterintuitively results in oxidation of Pu(V) to Pu(VII), concomitant with superoxide reduction.« less

  7. Scanning Probe Microscopy on heterogeneous CaCu3Ti4O12 thin films

    PubMed Central

    2011-01-01

    The conductive atomic force microscopy provided a local characterization of the dielectric heterogeneities in CaCu3Ti4O12 (CCTO) thin films deposited by MOCVD on IrO2 bottom electrode. In particular, both techniques have been employed to clarify the role of the inter- and sub-granular features in terms of conductive and insulating regions. The microstructure and the dielectric properties of CCTO thin films have been studied and the evidence of internal barriers in CCTO thin films has been provided. The role of internal barriers and the possible explanation for the extrinsic origin of the giant dielectric response in CCTO has been evaluated. PMID:21711646

  8. Scanning Probe Microscopy on heterogeneous CaCu3Ti4O12 thin films

    NASA Astrophysics Data System (ADS)

    Fiorenza, Patrick; Lo Nigro, Raffaella; Raineri, Vito

    2011-12-01

    The conductive atomic force microscopy provided a local characterization of the dielectric heterogeneities in CaCu3Ti4O12 (CCTO) thin films deposited by MOCVD on IrO2 bottom electrode. In particular, both techniques have been employed to clarify the role of the inter- and sub-granular features in terms of conductive and insulating regions. The microstructure and the dielectric properties of CCTO thin films have been studied and the evidence of internal barriers in CCTO thin films has been provided. The role of internal barriers and the possible explanation for the extrinsic origin of the giant dielectric response in CCTO has been evaluated.

  9. Scanning Probe Microscopy on heterogeneous CaCu3Ti4O12 thin films.

    PubMed

    Fiorenza, Patrick; Lo Nigro, Raffaella; Raineri, Vito

    2011-02-04

    The conductive atomic force microscopy provided a local characterization of the dielectric heterogeneities in CaCu3Ti4O12 (CCTO) thin films deposited by MOCVD on IrO2 bottom electrode. In particular, both techniques have been employed to clarify the role of the inter- and sub-granular features in terms of conductive and insulating regions. The microstructure and the dielectric properties of CCTO thin films have been studied and the evidence of internal barriers in CCTO thin films has been provided. The role of internal barriers and the possible explanation for the extrinsic origin of the giant dielectric response in CCTO has been evaluated.

  10. Degradation product analysis from the photocatalytic oxidation/reduction of 2,4-dichlorophenol in the presence of mesoporous silica encapsulated TiO2 particles and TiO2 dispersions (presentation)

    EPA Science Inventory

    Thin films of Degussa P-25 TiO2 encapsulated in an SBA-15 mesoporous silica matrix were prepared. The TiO2/SBA-15 thin film structure was verified using transmission electron microscopy (TEM) and small angle X-ray diffraction (XRD). During irradiation with 350 nm light, the TiO...

  11. Influence of growth time on crystalline structure, morphologic and optical properties of In2O3 thin films

    NASA Astrophysics Data System (ADS)

    Attaf, A.; Bouhdjar, A.; Saidi, H.; Benkhetta, Y.; Bendjedidi, H.; Nouadji, M.; Lehraki, N.

    2015-03-01

    Indium oxide (In2O3) thin films are successfully deposited on glass substrate at different deposition timings by ultrasonic spray technique using Indium chloride (InCl3) material source witch is prepared with dissolvent Ethanol (C2H5-OH), the physical properties of these films are characterized by XRD, MEB,UV-visible. XRD analysis revealed that the films are polycrystalline in nature having centered cubic crystal structure and symmetry space group I213 with a preferred grain orientation along to (222) plane when the deposition time changes from 4 to 10 min but after t = 10 min, especially when t = 13 min we found that the majority of grains preferred the plane (400). The maximum value of grain size D = 61,51 nm is attained for In2O3 films grown at t =10 min. the average transmittance is about 72%, The optical gap energy is found to decrease from 3.8 to 3.66 eV with growth time Increased from 4 to 10 min but after t = 10 min the value of Eg will increase to 3.72 eV. A systematic study on the influence of growth time on the properties of In2O3 thin films deposited by ultrasonic spray at 400 °C has been reported.

  12. Facile fabrication of a well-ordered porous Cu-doped SnO2 thin film for H2S sensing.

    PubMed

    Zhang, Shumin; Zhang, Pingping; Wang, Yun; Ma, Yanyun; Zhong, Jun; Sun, Xuhui

    2014-09-10

    Well-ordered Cu-doped and undoped SnO2 porous thin films with large specific surface areas have been fabricated on a desired substrate using a self-assembled soft template combined with simple physical cosputtering deposition. The Cu-doped SnO2 porous film gas sensor shows a significant enhancement in its sensing performance, including a high sensitivity, selectivity, and a fast response and recovery time. The sensitivity of the Cu-doped SnO2 porous sensor is 1 order of magnitude higher than that of the undoped SnO2 sensor, with average response and recovery times to 100 ppm of H2S of ∼ 10.1 and ∼ 42.4 s, respectively, at the optimal operating temperature of 180 °C. The well-defined porous sensors fabricated by the method also exhibit high reproducibility because of the accurately controlled fabrication process. The facile process can be easily extended to the fabrication of other semiconductor oxide gas sensors with easy doping and multilayer porous nanostructure for practical sensing applications.

  13. Electrical Conducting and Mechanism of Oxygen-Deficient Tin Oxide Films Deposited by RF Magnetron Sputtering at Various O2/Ar Ratios

    NASA Astrophysics Data System (ADS)

    Wang, Qi; Wang, Chengbiao; Lv, Changchun; Wang, Yang; Peng, Zhijian; Fu, Xiuli

    Oxygen-deficient tin oxide thin films were prepared by radiofrequency magnetron sputtering with a sintered non-stoichiometric tin oxide ceramic target under an atmosphere of various ratios of O2/Ar from pure Ar to 1:1. X-ray diffraction analysis showed that the thin films were polycrystalline with relatively strong (1 1 0), (1 0 1) and (2 1 1) diffraction peaks. Scanning electron microscopy observation revealed that the thin films prepared at different O2/Ar ratios were all of relatively dense and homogeneous structure. With increasing O2/Ar ratio, the grain size of the films decreased slightly, and their chemical composition became close to the stoichiometric SnO2; but the deposition rate as well as film thickness increased first and then decreased sharply. It was revealed that the main defect in obtained films was oxygen vacancy (VO), and as the O2/Ar ratio increased, the concentration of VO fell down monotonously, which would lead to an increased electrical resistivity.

  14. Consequence of oxidant to monomer ratio on optical and structural properties of Polypyrrole thin film deposited by oxidation polymerization technique

    NASA Astrophysics Data System (ADS)

    Jatratkar, Aviraj A.; Yadav, Jyotiprakash B.; Kamat, Sandip V.; Patil, Vaishali S.; Mahadik, D. B.; Barshilia, Harish C.; Puri, Vijaya; Puri, R. K.

    2015-05-01

    This paper reports the effect of oxidant to monomer (O/M) ratio on optical and structural properties of Polypyrrole (PPy) thin film deposited by chemical oxidation polymerization technique. Noticeable changes have observed in the properties of PPy thin films with O/M ratio. Cauliflower structure have been observed in FE-SEM images, wherein grain size is observed to decrease with increase in O/M ratio. AFM results are in good agreement with FE-SEM results. From FTIR spectra it is found that, PPy is in highly oxidized form at low O/M ratio but oxidation decreased with increase in O/M ratio. Also C-C stretching vibrations of PPy ring is decreased whereas C=C stretching is increased with ratio. Absorption peak around 450 nm corresponds to π-π* transition and around 800 nm for polarons and bipolarons. The intensity of such peaks confirms the conductivity of PPy, which is observed maximum at low O/M ratio and found to decrease with increase in ratio. Optical band gap (BG) is found to increase from 2.07 eV to 2.11 eV with increase in the O/M ratio.

  15. High-performance varistors simply by hot-dipping zinc oxide thin films in Pr6O11: Influence of temperature

    PubMed Central

    Wang, Yang; Peng, Zhijian; Wang, Qi; Wang, Chengbiao; Fu, Xiuli

    2017-01-01

    High-performance ZnO-Pr6O11 thin-film varistors were fabricated simply by hot-dipping oxygen-deficient zinc oxide thin films in Pr6O11 powder. The films had a composition of ZnO0.81 and a thickness of about 200 nm, which were deposited by radio frequency magnetron sputtering a sintered zinc oxide ceramic target. Special attention was paid on the temperature dependence of the varistors. In 50 min with hot-dipping temperature increased from 300–700 °C, the nonlinear coefficient (α) of the varistors increased, but with higher temperature it decreased again. Correspondingly, the leakage current (IL) decreased first and then increased, owing mainly to the formation and destroying of complete zinc oxide/Pr6O11 grain boundaries. The breakdown field (E1mA) decreased monotonously from 0.02217 to 0.01623 V/nm with increasing temperature (300–800 °C), due to the decreased number of effective grain boundaries in the varistors. The varistors prepared at 700 °C exhibited the optimum nonlinear properties with the highest α = 39.29, lowest IL = 0.02736 mA/cm2, and E1mA = 0.01757 V/nm. And after charge-discharge at room temperature for 1000 times, heating at 100 or 250 °C for up to 100 h, or applying at up to 250 °C, the varistors still performed well. Such nanoscaled thin-film varistors will be very promising in electrical/electronic devices working at low voltage. PMID:28155890

  16. Operando and in situ X-ray spectroscopies of degradation in La0.6Sr0.4Co0.2Fe0.8O(3-δ) thin film cathodes in fuel cells.

    PubMed

    Lai, Samson Y; Ding, Dong; Liu, Mingfei; Liu, Meilin; Alamgir, Faisal M

    2014-11-01

    Information from ex situ characterization can fall short in describing complex materials systems simultaneously exposed to multiple external stimuli. Operando X-ray absorption spectroscopy (XAS) was used to probe the local atomistic and electronic structure of specific elements in a La0.6Sr0.4Co0.2Fe0.8O(3-δ) (LSCF) thin film cathode exposed to air contaminated with H2O and CO2 under operating conditions. While impedance spectroscopy showed that the polarization resistance of the LSCF cathode increased upon exposure to both contaminants at 750 °C, XAS near-edge and extended fine structure showed that the degree of oxidation for Fe and Co decreases with increasing temperature. Synchrotron-based X-ray photoelectron spectroscopy tracked the formation and removal of a carbonate species, a Co phase, and different oxygen moieties as functions of temperature and gas. The combined information provides insight into the fundamental mechanism by which H2O and CO2 cause degradation in the cathode of solid oxide fuel cells. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. LaCrO3/CuFe2O4 Composite-Coated Crofer 22 APU Stainless Steel Interconnect of Solid Oxide Fuel Cells

    NASA Astrophysics Data System (ADS)

    Hosseini, Seyedeh Narjes; Enayati, Mohammad Hossein; Karimzadeh, Fathallah; Dayaghi, Amir Masoud

    2017-07-01

    Rapidly rising contact resistance and cathode Cr poisoning are the major problems associated with unavoidable chromia scale growth on ferritic stainless steel (FSS) interconnects of solid oxide fuel cells. This work investigates the performance of the novel screen-printed composite coatings consisting of dispersed conductive LaCrO3 particles in a CuFe2O4 spinel matrix for Crofer 22 APU FSS, with emphasis on the oxidation behavior and electrical conductivity of these coatings. The results show that the presence of protective spinel coating, accompanied by the effective role of LaCrO3 particle incorporation, prevents the Cr2O3 subscale growth as well as chromium migration into the coating surface at the end of 400 hours of oxidation at 1073 K (800 °C) in air. In addition, the composite coatings decreased the area specific resistance (ASR) from 51.7 and 13.8 mΩ cm2 for uncoated and spinel-coated samples, respectively, to a maximum of 7.7 mΩ cm2 for composite-coated samples after 400 hours of oxidation.

  18. Magnetoelectric effect in Cr2O3 thin films

    NASA Astrophysics Data System (ADS)

    He, Xi; Wang, Yi; Sahoo, Sarbeswar; Binek, Christian

    2008-03-01

    Magnetoelectric materials experienced a recent revival as promising components of novel spintronic devices [1, 2, 3]. Since the magnetoelectric (ME) effect is relativistically small in traditional antiferromagnetic compounds like Cr2O3 (max. αzz 4ps/m ) and also cross- coupling between ferroic order parameters is typically small in the modern multiferroics, it is a challenge to electrically induce sufficient magnetization required for the envisioned device applications. A straightforward approach is to increase the electric field at constant voltage by reducing the thickness of the ME material to thin films of a few nm. Since magnetism is known to be affected by geometrical confinement thickness dependence of the ME effect in thin film Cr2O3 is expected. We grow (111) textured Cr2O3 films with various thicknesses below 500 nm and study the ME effect for various ME annealing conditions as a function of temperature with the help of Kerr-magnetometry. [1] P. Borisov et al. Phys. Rev. Lett. 94, 117203 (2005). [2] Ch. Binek, B.Doudin, J. Phys. Condens. Matter 17, L39 (2005). [3] R. Ramesh and Nicola A. Spaldin 2007 Nature Materials 6 21.

  19. Parameters controlling microstructures and resistance switching of electrodeposited cuprous oxide thin films

    NASA Astrophysics Data System (ADS)

    Yazdanparast, Sanaz

    2016-12-01

    Cuprous oxide (Cu2O) thin films were electrodeposited cathodically from a highly alkaline bath using tartrate as complexing agent. Different microstructures for Cu2O thin films were achieved by varying the applied potential from -0.285 to -0.395 V versus a reference electrode of Ag/AgCl at 50 °C in potentiostatic mode, and separately by changing the bath temperature from 25 to 50 °C in galvanostatic mode. Characterization experiments showed that both grain size and orientation of Cu2O can be controlled by changing the applied potential. Applying a high negative potential of -0.395 V resulted in smaller grain size of Cu2O thin films with a preferred orientation in [111] direction. An increase in the bath temperature in galvanostatic electrodeposition increased the grain size of Cu2O thin films. All the films in Au/Cu2O/Au-Pd cell showed unipolar resistance switching behavior after an initial FORMING process. Increasing the grain size of Cu2O thin films and decreasing the top electrode area increased the FORMING voltage and decreased the current level of high resistance state (HRS). The current in low resistance state (LRS) was independent of the top electrode area and the grain size of deposited films, suggesting a filamentary conduction mechanism in unipolar resistance switching of Cu2O.

  20. Stabilization of scandium rich spinel ferrite CoFe{sub 2−x}Sc{sub x}O{sub 4} (x≤1) in thin films

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Lefevre, Christophe, E-mail: christophe.lefevre@ipcms.unistra.fr; Roulland, François; Thomasson, Alexandre

    2015-12-15

    Scandium rich cobalt ferrites Co{sub y}Fe{sub 3−x−y}Sc{sub x}O{sub 4} with y~1 never obtained in bulk could be stabilized in pulsed laser deposited thin films. Scandium contents of up to x=1 are reached. The cell parameter increases versus x as awaited when considering the size of scandium. It is equal to 0.8620 nm for x=1, significantly higher than that of CoFe{sub 2}O{sub 4} (0.8396 nm). The lattice mismatch between the MgO (100) substrate and the scandium-containing spinel leads to an increased roughness. Cobalt is displaced from the octahedral site by Sc and mainly occupies the tetrahedral sites for high x values.more » - Graphical abstract: Magnification of the XRD patterns recorded on thin films of CoFe{sub 2-x}Sc{sub x}O{sub 4} for x=0, 0.45, 1 and 1.2, the arrows denote the (004) and (008) diffraction lines of the spinel phase.« less

  1. Bright Lu2O3:Eu thin-film scintillators for high-resolution radioluminescence microscopy

    PubMed Central

    Sengupta, Debanti; Miller, Stuart; Marton, Zsolt; Chin, Frederick; Nagarkar, Vivek

    2015-01-01

    We investigate the performance of a new thin-film Lu2O3:Eu scintillator for single-cell radionuclide imaging. Imaging the metabolic properties of heterogeneous cell populations in real time is an important challenge with clinical implications. We have developed an innovative technique called radioluminescence microscopy, to quantitatively and sensitively measure radionuclide uptake in single cells. The most important component of this technique is the scintillator, which converts the energy released during radioactive decay into luminescent signals. The sensitivity and spatial resolution of the imaging system depend critically on the characteristics of the scintillator, i.e. the material used and its geometrical configuration. Scintillators fabricated using conventional methods are relatively thick, and therefore do not provide optimal spatial resolution. We compare a thin-film Lu2O3:Eu scintillator to a conventional 500 μm thick CdWO4 scintillator for radioluminescence imaging. Despite its thinness, the unique scintillation properties of the Lu2O3:Eu scintillator allow us to capture single positron decays with over fourfold higher sensitivity, a significant achievement. The thin-film Lu2O3:Eu scintillators also yield radioluminescence images where individual cells appear smaller and better resolved on average than with the CdWO4 scintillators. Coupled with the thin-film scintillator technology, radioluminescence microscopy can yield valuable and clinically relevant data on the metabolism of single cells. PMID:26183115

  2. Hierarchically Structured Co3O4@Pt@MnO2 Nanowire Arrays for High-Performance Supercapacitors

    NASA Astrophysics Data System (ADS)

    Xia, Hui; Zhu, Dongdong; Luo, Zhentao; Yu, Yue; Shi, Xiaoqin; Yuan, Guoliang; Xie, Jianping

    2013-10-01

    Here we proposed a novel architectural design of a ternary MnO2-based electrode - a hierarchical Co3O4@Pt@MnO2 core-shell-shell structure, where the complemental features of the three key components (a well-defined Co3O4 nanowire array on the conductive Ti substrate, an ultrathin layer of small Pt nanoparticles, and a thin layer of MnO2 nanoflakes) are strategically combined into a single entity to synergize and construct a high-performance electrode for supercapacitors. Owing to the high conductivity of the well-defined Co3O4 nanowire arrays, in which the conductivity was further enhanced by a thin metal (Pt) coating layer, in combination with the large surface area provided by the small MnO2 nanoflakes, the as-fabricated Co3O4@Pt@MnO2 nanowire arrays have exhibited high specific capacitances, good rate capability, and excellent cycling stability. The architectural design demonstrated in this study provides a new approach to fabricate high-performance MnO2-based nanowire arrays for constructing next-generation supercapacitors.

  3. Improvement of bias-stability in amorphous-indium-gallium-zinc-oxide thin-film transistors by using solution-processed Y{sub 2}O{sub 3} passivation

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    An, Sungjin; Mativenga, Mallory; Kim, Youngoo

    2014-08-04

    We demonstrate back channel improvement of back-channel-etch amorphous-indium-gallium-zinc-oxide (a-IGZO) thin-film transistors by using solution-processed yttrium oxide (Y{sub 2}O{sub 3}) passivation. Two different solvents, which are acetonitrile (35%) + ethylene glycol (65%), solvent A and deionized water, solvent B are investigated for the spin-on process of the Y{sub 2}O{sub 3} passivation—performed after patterning source/drain (S/D) Mo electrodes by a conventional HNO{sub 3}-based wet-etch process. Both solvents yield devices with good performance but those passivated by using solvent B exhibit better light and bias stability. Presence of yttrium at the a-IGZO back interface, where it occupies metal vacancy sites, is confirmed by X-ray photoelectronmore » spectroscopy. The passivation effect of yttrium is more significant when solvent A is used because of the existence of more metal vacancies, given that the alcohol (65% ethylene glycol) in solvent A may dissolve the metal oxide (a-IGZO) through the formation of alkoxides and water.« less

  4. Remarkably high mobility ultra-thin-film metal-oxide transistor with strongly overlapped orbitals

    NASA Astrophysics Data System (ADS)

    Wei Shih, Chen; Chin, Albert; Fu Lu, Chun; Fang Su, Wei

    2016-01-01

    High mobility channel thin-film-transistor (TFT) is crucial for both display and future generation integrated circuit. We report a new metal-oxide TFT that has an ultra-thin 4.5 nm SnO2 thickness for both active channel and source-drain regions, very high 147 cm2/Vs field-effect mobility, high ION/IOFF of 2.3 × 107, small 110 mV/dec sub-threshold slope, and a low VD of 2.5 V for low power operation. This mobility is already better than chemical-vapor-deposition grown multi-layers MoS2 TFT. From first principle quantum-mechanical calculation, the high mobility TFT is due to strongly overlapped orbitals.

  5. Water oxidation by size selected Co 27 clusters supported on Fe 2O 3

    DOE PAGES

    Pellin, Michael J.; Riha, Shannon C.; Tyo, Eric C.; ...

    2016-09-22

    The complexity of the water oxidation reaction makes understanding the role of individual catalytic sites critical to improving the process. Here, size-selected 27-atom cobalt clusters (Co 27) deposited on hematite (Fe 2O 3) anodes were tested for water oxidation activity. The uniformity of these anodes allows measurement of the activity of catalytic sites of well-defined nuclearity and known density. Grazing incidence X-ray absorption near-edge spectroscopy (GIXANES) characterization of the anodes before and after electrochemical cycling demonstrates that these Co 27 clusters are stable to dissolution even in the harsh water oxidation electrochemical environment. They are also stable under illumination atmore » the equivalent of 0.4suns irradiation. The clusters show turnover rates for water oxidation that are comparable or higher than those reported for Pd- and Co-based materials or for hematite. The support for the Co 27 clusters is Fe 2O 3 grown by atomic layer deposition on a Si chip. We have chosen to deposit a Fe2O3 layer that is only a few unit cells thick (2nm), to remove complications related to exciton diffusion. We find that the electrocatalytic and the photoelectrocatalytic activity of the Co 27/Fe 2O 3 material is significantly improved when the samples are annealed (with the clusters already deposited). Lastly, given that the support is thin and that the cluster deposition density is equivalent to approximately 5% of an atomic monolayer, we suggest that annealing may significantly improve the exciton diffusion from the support to the catalytic moiety.« less

  6. Sputtered boron indium oxide thin-film transistors

    NASA Astrophysics Data System (ADS)

    Stewart, Kevin A.; Gouliouk, Vasily; Keszler, Douglas A.; Wager, John F.

    2017-11-01

    Boron indium oxide (BIO) is studied for thin-film transistor (TFT) channel layer applications. Sputtered BIO thin films exhibit an amorphous phase over a wide range of B2O3/In2O3 ratios and remain amorphous up to 500 °C. The band gap decreases linearly with decreasing boron content, whereas device performance generally improves with decreasing boron content. The best amorphous BIO TFT exhibits a field-effect mobility of 10 cm2 V-1 s-1, turn-on voltage of 2.5 V, and sub-threshold swing of 0.72 V/dec. Decreasing the boron content to 12.5% leads to a polycrystalline phase, but further increases the mobility up to 20-40 cm2 V-1 s-1. TCAD simulation results suggest that the reason for higher performance after increasing the anneal temperature from 200 to 400 °C is due to a lower defect density in the sub-bandgap region of the BIO channel layer.

  7. Structural, electrical, optical and magnetic properties of NiO/ZnO thin films

    NASA Astrophysics Data System (ADS)

    Sushmitha, V.; Maragatham, V.; Raj, P. Deepak; Sridharan, M.

    2018-02-01

    Nickel oxide/Zinc oxide (NiO/ZnO) thin films have been deposited onto thoroughly cleaned glass substrates by reactive direct current (DC) magnetron sputtering technique and subsequently annealed at 300 °C for 3 h in vacuum. The NiO/ZnO thin films were then studied for their structural, optical and electrical properties. X-ray diffraction (XRD) pattern of ZnO and NiO showed the diffraction planes corresponding to hexagonal and cubic phase respectively. The optical properties showed that with the increase in the deposition time of NiO the energy band gap varied between 3.1 to 3.24 eV. Hence, by changing the deposition time of NiO the tuning of band gap and conductivity were achieved. The magnetic studies revealed the diamagnetic nature of the NiO/ZnO thin films.

  8. Synthesis of MoS2-reduced graphene oxide/Fe3O4 nanocomposite for enhanced electromagnetic interference shielding effectiveness

    NASA Astrophysics Data System (ADS)

    Prasad, Jagdees; Singh, Ashwani Kumar; Shah, Jyoti; Kotnala, R. K.; Singh, Kedar

    2018-05-01

    This article presents a facile two step hydrothermal process for the synthesis of MoS2-reduced graphene oxide/Fe3O4 (MoS2-rGO/Fe3O4) nanocomposite and its application as an excellent electromagnetic interference shielding material. Characterization tools like; scanning electron microscope, transmission electron microscope, x-ray diffraction, and Raman spectroscopy were used to confirm the formation of nanocomposite and found that spherical Fe3O4 nanoparticles are well dispersed over MoS2-rGO composite with average particle size ∼25–30 nm was confirmed by TEM. Structural characterization done by XRD was found inconsistent with the known lattice parameter of MoS2 nanosheet, reduced graphene oxide and Fe3O4 nanoparticles. Electromagnetic shielding effectiveness of MoS2-rGO/Fe3O4 nanocomposite was evaluated and found to be an excellent EMI shielding material in X-band range (8.0–12.0 GHz). MoS2-rGO composite shows poor shielding capacity (SET ∼ 3.81 dB) in entire range as compared to MoS2-rGO/Fe3O4 nanocomposite (SET ∼ 8.27 dB). It is due to interfacial polarization in the presence of EM field. The result indicates that MoS2-rGO/Fe3O4 nanocomposite provide a new stage for the next generation in high-performance EM wave absorption and EMI shielding effectiveness.

  9. Core-shell CoFe2O4@Co-Fe-Bi nanoarray: a surface-amorphization water oxidation catalyst operating at near-neutral pH.

    PubMed

    Ji, Xuqiang; Hao, Shuai; Qu, Fengli; Liu, Jingquan; Du, Gu; Asiri, Abdullah M; Chen, Liang; Sun, Xuping

    2017-06-14

    The exploration of high-performance and earth-abundant water oxidation catalysts operating under mild conditions is highly attractive and challenging. In this communication, core-shell CoFe 2 O 4 @Co-Fe-Bi nanoarray on carbon cloth (CoFe 2 O 4 @Co-Fe-Bi/CC) was successfully fabricated by in situ surface amorphization of CoFe 2 O 4 nanoarray on CC (CoFe 2 O 4 /CC). As a 3D water oxidation electrode, CoFe 2 O 4 @Co-Fe-Bi/CC shows outstanding activity with an overpotential of 460 mV to drive a geometrical catalytic current density of 10 mA cm -2 in 0.1 M potassium borate (pH 9.2). Notably, it also demonstrates superior long-term durability for at least 20 h with 96% Faradic efficiency. Density functional theory calculations indicate that the conversion from OOH* to O 2 is the rate-limiting step and the high water oxidation activity of CoFe 2 O 4 @Co-Fe-Bi/CC is associated with the lower free energy of 1.84 eV on a Co-Fe-Bi shell.

  10. Multivalent Mn-doped TiO2 thin films

    NASA Astrophysics Data System (ADS)

    Lin, C. Y. W.; Channei, D.; Koshy, P.; Nakaruk, A.; Sorrell, C. C.

    2012-07-01

    Thin films of TiO2 doped with Mn were deposited on F-doped SnO2-coated glass using spin coating. The concentration of the dopant was in the range 0-7 wt% Mn (metal basis). The films were examined in terms of the structural, chemical, and optical properties. Glancing angle X-ray diffraction data show that the films consisted of the anatase polymorph of TiO2, without any contaminant phases. The X-ray photoelectron spectroscopy data indicate the presence of Mn3+ and Mn4+ in the doped films as well as atomic disorder and associated structural distortion. Ultraviolet-visible spectrophotometry data show that the optical indirect band gap of the films decreased significantly with increasing manganese doping, from 3.32 eV for the undoped composition to 2.90 eV for that doped with 7 wt% Mn.

  11. Effect of annealing temperature on optical and electrical properties of ZrO2-SnO2 based nanocomposite thin films

    NASA Astrophysics Data System (ADS)

    Anitha, V. S.; Lekshmy, S. Sujatha; Berlin, I. John; Joy, K.

    2014-01-01

    Transparent nanocomposite ZrO2-SnO2 thin films were prepared by sol-gel dip-coating technique. Films were annealed at 500°C, 800°C and 1200°C respectively. X-ray diffraction(XRD) spectra showed a mixture of three phases: tetragonal ZrO2 and SnO2 and orthorhombic ZrSnO4. The grain size of all the three phases' increased with annealing temperature. An average transmittance greater than 85%(in UV-Visible region) is observed for all the films. The band gap for the films decreased from 4.79 eV to 4.62 eV with increase in annealing temperature from 500 to 1200 °C. The electrical resistivity increased with increase in annealing temperature. Such composite ZrO2-SnO2 films can be used in many applications and in optoelectronic devices.

  12. Fabrication of assembled ZnO/TiO2 heterojunction thin film transistors using solution processing technique

    NASA Astrophysics Data System (ADS)

    Liau, Leo Chau-Kuang; Lin, Yun-Guo

    2015-01-01

    Ceramic-based metal-oxide-semiconductor (MOS) field-effect thin film transistors (TFTs), which were assembled by ZnO and TiO2 heterojunction films coated using solution processing technique, were fabricated and characterized. The fabrication of the device began with the preparation of ZnO and TiO2 films by spin coating. The ZnO and TiO2 films that were stacked together and annealed at 450 °C were characterized as a p-n junction diode. Two types of the devices, p-channel and n-channel TFTs, were produced using different assemblies of ZnO and TiO2 films. Results show that the p-channel TFTs (p-TFTs) and n-channel TFTs (n-TFTs) using the assemblies of ZnO and TiO2 films were demonstrated by source-drain current vs. drain voltage (IDS-VDS) measurements. Several electronic properties of the p- and n- TFTs, such as threshold voltage (Vth), on-off ratio, channel mobility, and subthreshold swing (SS), were determined by current-voltage (I-V) data analysis. The ZnO/TiO2-based TFTs can be produced using solution processing technique and an assembly approach.

  13. Synthesis of KMnO4-treated magnetic graphene oxide nanocomposite (Fe3O4@GO/MnO x ) and its application for removing of Cu2+ ions from aqueous solution

    NASA Astrophysics Data System (ADS)

    Zhang, Huining; Chang, Qing; Jiang, Yu; Li, Huili; Yang, Yahong

    2018-04-01

    A magnetic KMnO4-treated graphene-oxide-based nanocomposite, Fe3O4@GO/MnO x , was synthesized through a facile hydrothermal technique. The properties of the Fe3O4@GO/MnO x nanocomposite were characterized by SEM, XRD and FTIR. Batch experiments showed that the maximum adsorption capacity calculated by the Langmuir model for Cu2+ was 62.65 mg g-1 at T = 303.15 K. Kinetics and XPS analysis also revealed that the mechanism of Cu2+ removal was mainly a chemical adsorption process involving both the MnO x particles and oxygen functional groups. The prepared Fe3O4@GO/MnO x was found to be an ideal adsorbent for the removal of Cu2+ ions due to the MnO x particle coating, and was easily separated using a magnetic field after utilization. Reusability studies imply that Fe3O4@GO/MnO x is a suitable material for heavy metal ion removal from aqueous solutions in real applications.

  14. Mesoporous xEr 2O 3·CoTiO 3 composite oxide catalysts for low temperature dehydrogenation of ethylbenzene to styrene using CO 2 as a soft oxidant

    DOE PAGES

    Yue, Yanfeng; Zhang, Li; Chen, Jihua; ...

    2016-01-01

    A series of mesoporous xEr 2O 3·CoTiO 3 composite oxide catalysts have been prepared using template method and tested as a new type of catalyst for the oxidative dehydrogenation of ethylbenzene to styrene by using CO 2 as a soft oxidant. Among the catalysts tested, the 0.25Er 2O 3 CoTiO 3 sample with a ratio of 1:4:4 content and calcined at 600 oC exhibited the highest ethylbenzene conversion (58%) and remarkable styrene selectivity (95%) at low temperature (450 °C).

  15. Influence of precursor concentration on the structural, optical and electrical properties of indium oxide thin film prepared by a sol-gel method

    NASA Astrophysics Data System (ADS)

    Lau, L. N.; Ibrahim, N. B.; Baqiah, H.

    2015-08-01

    This research was carried out to study the effect of different precursor concentrations on the physical properties of indium oxide (In2O3) thin film. In2O3 is a promising n-type semiconductor material that has been used in optoelectronic applications because of its highly transparent properties. It is a transparent conducting oxide with a wide band gap (∼3.7 eV). The experiment was started by preparing different precursor concentrations of indium nitrate hydrate (In (NO3)·H2O) solution and followed by the spin coating technique prior to an annealing process at 500 °C. Indium oxide thin films were characterized using an X-ray diffractometer, an ultraviolet-visible spectroscopy, a field emission scanning electron microscope and a Hall Effect Measurement System in order to determine the influence caused by the different molarities of indium oxide. The result showed that the film thickness increased with the indium oxide molarity. Film thicknesses were in the range of 0.3-135.1 nm and optical transparency of films was over 94%. Lowest resistivity of 2.52 Ω cm with a mobility of 26.60 cm2 V-1 S-1 and carrier concentration of 4.27 × 1017 cm-3 was observed for the indium oxide thin film prepared at 0.30 M.

  16. Removal of 4-Nitrophenol from Water Using Ag–N–P-Tridoped TiO2 by Photocatalytic Oxidation Technique

    PubMed Central

    Achamo, Temesgen; Yadav, O. P.

    2016-01-01

    Photocatalytic oxidation using semiconductor nanoparticles is an efficient, eco-friendly, and cost-effective process for the removal of organic pollutants, such as dyes, pesticides, phenols, and their derivatives in water. In the present study, nanosize Ag–N–P-tridoped titanium(IV) oxide (TiO2) was prepared by using sol–gel-synthesized Ag-doped TiO2 and soybean (Glycine max) or chickpea (Cicer arietinum) seeds as nonmetallic bioprecursors. As-synthesized photocatalysts were characterized using X-ray diffraction, Fourier transform infrared, and ultra violet (UV)–visible spectroscopic techniques. Average crystallite size of the studied photocatalysts was within 39–46 nm. Whereas doped Ag in TiO2 minimized the photogenerated electron–hole recombination, doped N and P extended its photoabsorption edge to visible region. Tridoping of Ag, N, and P in TiO2 exhibited synergetic effect toward enhancing its photocatalytic degradation of 4-nitrophenol (4-NP), separately, under UV and visible irradiations. At three hours, degradations of 4-NP over Ag–N–P-tridoped TiO2 under UV and visible radiations were 73.8 and 98.1%, respectively. PMID:27081309

  17. The role of reduced graphene oxide on the electrochemical activity of MFe2O4 (M = Fe, Co, Ni and Zn) nanohybrids

    NASA Astrophysics Data System (ADS)

    Suresh, Shravan; Prakash, Anand; Bahadur, D.

    2018-02-01

    In this work, a comparative study of electrochemical performance of reduced graphene oxide-ferrites (RGO-MFe2O4, M = Fe, Co, Ni, and Zn) nanohybrids synthesized by hydrothermal method was done. The structural morphology and investigation of other physical properties of nanohybrids confirm the cubic spinel phase of the MFe2O4, reduction of graphene oxide and the distribution of ferrite nanoparticles (NPs) on RGO nanosheets. The role of RGO on the electrochemical behavior of nanohybrids was understood by quantifying the charge storage capacitance and charging-discharging behavior in a 0.1 M Na2SO4 electrolyte. The specific capacitance values of pristine Fe3O4, CoFe2O4, NiFe2O4, and ZnFe2O4 are 128, 117, 15.2 and 9.1 F g-1 respectively whereas specific capacitance of RGO-Fe3O4, RGO-CoFe2O4, RGO-NiFe2O4 and RGO-ZnFe2O4 are 233, 200, 25 and 66.8 F g-1 respectively. Our investigation suggests that apart from specific surface area of nanohybrids other factors such as structural morphology determine interaction between nanohybrids and electrolyte ions which play critical role in elevating the performance of electrodes.

  18. Facile synthesis of hierarchical mesoporous weirds-like morphological MnO2 thin films on carbon cloth for high performance supercapacitor application.

    PubMed

    Shinde, Pragati A; Lokhande, Vaibhav C; Ji, Taeksoo; Lokhande, Chandrakant D

    2017-07-15

    The mesoporous nanostructured metal oxides have a lot of capabilities to upsurge the energy storing capacity of the supercapacitor. In present work, different nanostructured morphologies of MnO 2 have been successfully fabricated on flexible carbon cloth by simple but capable hydrothermal method at different deposition temperatures. The deposition temperature has strong influence on reaction kinetics, which subsequently alters the morphology and electrochemical performance. Among different nanostructured MnO 2 thin films, the mesoporous weirds composed thin film obtained at temperature of 453K exhibits excellent physical and electrochemical features for supercapacitor application. The weirds composed MnO 2 thin film exhibits specific surface area of 109m 2 g -1 , high specific capacitance of 595Fg -1 with areal capacitance of 4.16Fcm -2 at a scan rate of 5mVs -1 and high specific energy of 56.32Whkg -1 . In addition to this, MnO 2 weirds attain capacity retention of 87 % over 2000 CV cycles, representing better cycling stability. The enhanced electrochemical performance could be ascribed to direct growth of highly porous MnO 2 weirds on carbon cloth which provide more pathways for easy diffusion of electrolyte into the interior of electroactive material. The as-fabricated electrode with improved performance could be ascribed as a potential electrode material for energy storage devices. Copyright © 2017 Elsevier Inc. All rights reserved.

  19. Synergistic approach to high-performance oxide thin film transistors using a bilayer channel architecture.

    PubMed

    Yu, Xinge; Zhou, Nanjia; Smith, Jeremy; Lin, Hui; Stallings, Katie; Yu, Junsheng; Marks, Tobin J; Facchetti, Antonio

    2013-08-28

    We report here a bilayer metal oxide thin film transistor concept (bMO TFT) where the channel has the structure: dielectric/semiconducting indium oxide (In2O3) layer/semiconducting indium gallium oxide (IGO) layer. Both semiconducting layers are grown from solution via a low-temperature combustion process. The TFT mobilities of bottom-gate/top-contact bMO TFTs processed at T = 250 °C are ~5tmex larger (~2.6 cm(2)/(V s)) than those of single-layer IGO TFTs (~0.5 cm(2)/(V s)), reaching values comparable to single-layer combustion-processed In2O3 TFTs (~3.2 cm(2)/(V s)). More importantly, and unlike single-layer In2O3 TFTs, the threshold voltage of the bMO TFTs is ~0.0 V, and the current on/off ratio is significantly enhanced to ~1 × 10(8) (vs ~1 × 10(4) for In2O3). The microstructure and morphology of the In2O3/IGO bilayers are analyzed by X-ray diffraction, atomic force microscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy, revealing the polycrystalline nature of the In2O3 layer and the amorphous nature of the IGO layer. This work demonstrates that solution-processed metal oxides can be implemented in bilayer TFT architectures with significantly enhanced performance.

  20. Amorphous Mixed-Metal Oxide Thin Films from Aqueous Solution Precursors with Near-Atomic Smoothness.

    PubMed

    Kast, Matthew G; Cochran, Elizabeth A; Enman, Lisa J; Mitchson, Gavin; Ditto, Jeffrey; Siefe, Chris; Plassmeyer, Paul N; Greenaway, Ann L; Johnson, David C; Page, Catherine J; Boettcher, Shannon W

    2016-12-28

    Thin films with tunable and homogeneous composition are required for many applications. We report the synthesis and characterization of a new class of compositionally homogeneous thin films that are amorphous solid solutions of Al 2 O 3 and transition metal oxides (TMO x ) including VO x , CrO x , MnO x , Fe 2 O 3 , CoO x , NiO, CuO x , and ZnO. The synthesis is enabled by the rapid decomposition of molecular transition-metal nitrates TM(NO 3 ) x at low temperature along with precondensed oligomeric Al(OH) x (NO 3 ) 3-x cluster species, both of which can be processed from aq solution. The films are dense, ultrasmooth (R rms < 1 nm, near 0.1 nm in many cases), and atomically mixed amorphous metal-oxide alloys over a large composition range. We assess the chemical principles that favor the formation of amorphous homogeneous films over rougher phase-segregated nanocrystalline films. The synthesis is easily extended to other compositions of transition and main-group metal oxides. To demonstrate versatility, we synthesized amorphous V 0.1 Cr 0.1 Mn 0.1 Fe 0.1 Zn 0.1 Al 0.5 O x and V 0.2 Cr 0.2 Fe 0.2 Al 0.4 O x with R rms ≈ 0.1 nm and uniform composition. The combination of ideal physical properties (dense, smooth, uniform) and broad composition tunability provides a platform for film synthesis that can be used to study fundamental phenomena when the effects of transition metal cation identity, solid-state concentration of d-electrons or d-states, and/or crystallinity need to be controlled. The new platform has broad potential use in controlling interfacial phenomena such as electron transfer in solar-cell contacts or surface reactivity in heterogeneous catalysis.

  1. Indium oxide thin film as potential photoanodes for corrosion protection of stainless steel under visible light

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Zhang, Yan; Yu, Jianqiang, E-mail: jianqyu@qdu.edu.cn; Sun, Kai

    Graphical abstract: If the conduction band potential of In{sub 2}O{sub 3} is more negative than the corrosion potential of stainless steel, photo-induced electrons will be transferred from In{sub 2}O{sub 3} to the steel, thus shifting the potential of the steel into a corrosion immunity region and preventing the steel from the corrosion. - Highlights: • Indium oxide performed novel application under visible light. • Indium oxide by sol–gel method behaved better photoelectrochemical properties. • Electrons were transferred to stainless steel from indium oxide once light on. - Abstract: This paper reports the photoelectrochemical cathodic protection of 304 stainless steel bymore » In{sub 2}O{sub 3} thin-film under visible-light. The films were fabricated with In{sub 2}O{sub 3} powders, synthesized by both sol–gel (In{sub 2}O{sub 3}-sg) and solid-state (In{sub 2}O{sub 3}-ss) processes. The photo-induced open circuit potential and the photo-to-current efficiency measurements suggested that In{sub 2}O{sub 3} could be a promising candidate material for photoelectrochemical cathodic protection of metallic alloys under visible light. Moreover, the polarization curve experimental results indicated that In{sub 2}O{sub 3}-sg thin-film can mitigate the corrosion potential of 304 stainless steel to much more negative values with a higher photocurrent density than the In{sub 2}O{sub 3}-ss film under visible-light illumination. All the results demonstrated that the In{sub 2}O{sub 3}-sg thin-film provides a better photoelectrochemical cathodic protection for 304 stainless steel than In{sub 2}O{sub 3}-ss thin-film under visible-light illumination. The higher photoelectrochemical efficiency is possibly due to the uniform thin films produced with the smaller particle size of In{sub 2}O{sub 3}-sg, which facilitates the transfer of the photo-induced electrons from bulk to the surface and suppresses the charge recombination of the electrons and holes.« less

  2. Cr:SnO2 thin films-synthesis and characterization

    NASA Astrophysics Data System (ADS)

    Varghese, Anitta Rose; B. Bhadrapriya, C.; Amarendra, G.; Hussain, Shamima

    2018-04-01

    Thin films of pure and Chromium doped SnO2 were synthesized using sol-gel method by spin coating technique. XRD studies confirmed the formation of tetragonal structure for SnO2 thin films. Variations in peak width and position were identified with doping. The optical band gap of the undoped films was found to be 3.8eV and varied with doping. Raman spectrum gave signature peaks of Sn-O and Cr-O bonds for undoped and doped films. The uniformity of the samples and formation of aggregates were observed from FESEM analysis.

  3. Effect of substrate on the atomic structure and physical properties of thermoelectric Ca3Co4O9 thin films

    NASA Astrophysics Data System (ADS)

    Qiao, Q.; Gulec, A.; Paulauskas, T.; Kolesnik, S.; Dabrowski, B.; Ozdemir, M.; Boyraz, C.; Mazumdar, D.; Gupta, A.; Klie, R. F.

    2011-08-01

    The incommensurately layered cobalt oxide Ca3Co4O9 exhibits an unusually high Seebeck coefficient as a polycrystalline bulk material, making it ideally suited for many high temperature thermoelectric applications. In this paper, we investigate properties of Ca3Co4O9 thin films grown on cubic perovskite SrTiO3, LaAlO3, and (La0.3Sr0.7)(Al0.65Ta0.35)O3 substrates and on hexagonal Al2O3 (sapphire) substrates using the pulsed laser deposition technique. X-ray diffraction and transmission electron microscopy analysis indicate strain-free growth of films, irrespective of the substrate. However, depending on the lattice and symmetry mismatch, defect-free growth of the hexagonal CoO2 layer is stabilized only after a critical thickness and, in general, we observe the formation of a stable Ca2CoO3 buffer layer near the substrate-film interface. Beyond this critical thickness, a large concentration of CoO2 stacking faults is observed, possibly due to weak interlayer interaction in this layered material. We propose that these stacking faults have a significant impact on the Seebeck coefficient and we report higher values in thinner Ca3Co4O9 films due to additional phonon scattering sites, necessary for improved thermoelectric properties.

  4. The oxidation of 2,6-di-tert-butyl-4-methylphenol

    USGS Publications Warehouse

    Yohe, G.R.; Dunbar, J.E.; Pedrotti, R.L.; Scheidt, F.M.; Lee, F.G.H.; Smith, E.C.

    1956-01-01

    The products formed in the oxidation of 2,6-di-tert-butyl-4-methylphenol with oxygen and sodium hydroxide at about 100?? are 3,5-di-tert-butyl-4-hydroxybenzaldehyde, trimethylacetic acid, an acidic compound C14H22O3, and probably 2,6-di-tert-butylbenzoquinone (which was actually isolated in the similar oxidation of the above-named benzaldehyde), in addition to compounds previously reported. Some of the properties of C14H22O3 are given, and the oxidation of it to 2,3-di-tert-butylsuccinic anhydride is described, but assignment of structure is reserved pending the completion of more experimental work.

  5. Effect of betaine in the successful synthesis of CoFe2O4 containing octahedron nanoparticles for electrocatalytic water oxidation

    NASA Astrophysics Data System (ADS)

    Valdez, R.; Olivas, A.; Grotjahn, D. B.; Barrios, E.; Arjona, N.; Antaño, R.; Oropeza-Guzman, M. T.

    2017-12-01

    The development of robust catalysts that oxidize water is necessary for their application in artificial photosynthesis cells. Here we report the synthesis and characterization of octahedral CoFe2O4 nanoparticles obtained through a novel aqueous method that employs betaine, (CH3)3+NCH2COO-, as the stabilizer agent. The synthetic conditions are modified changing the betaine content and the metal precursor ratios. These conditions modify the shape of CoFe2O4 finding both, octahedral and semi-spherical nanoparticles. Linear voltammetry measurements show the octahedral CoFe2O4 lead to an overpotential of ∼390 mV at the onset potential for water oxidation at alkaline conditions. Among the as-synthesized cobalt-ferrite nanomaterials, the CoFe(1:2)-C in the form of tiny nanoparticles performed a superior electrocatalytic water oxidation in alkaline conditions, showing an overpotential of ∼335 mV, which is lower than other similar catalysts in literature.

  6. Flexible and High-Performance Amorphous Indium Zinc Oxide Thin-Film Transistor Using Low-Temperature Atomic Layer Deposition.

    PubMed

    Sheng, Jiazhen; Lee, Hwan-Jae; Oh, Saeroonter; Park, Jin-Seong

    2016-12-14

    Amorphous indium zinc oxide (IZO) thin films were deposited at different temperatures, by atomic layer deposition (ALD) using [1,1,1-trimethyl-N-(trimethylsilyl)silanaminato]indium (INCA-1) as the indium precursor, diethlzinc (DEZ) as the zinc precursor, and hydrogen peroxide (H 2 O 2 ) as the reactant. The ALD process of IZO deposition was carried by repeated supercycles, including one cycle of indium oxide (In 2 O 3 ) and one cycle of zinc oxide (ZnO). The IZO growth rate deviates from the sum of the respective In 2 O 3 and ZnO growth rates at ALD growth temperatures of 150, 175, and 200 °C. We propose growth temperature-dependent surface reactions during the In 2 O 3 cycle that correspond with the growth-rate results. Thin-film transistors (TFTs) were fabricated with the ALD-grown IZO thin films as the active layer. The amorphous IZO TFTs exhibited high mobility of 42.1 cm 2 V -1 s -1 and good positive bias temperature stress stability. Finally, flexible IZO TFT was successfully fabricated on a polyimide substrate without performance degradation, showing the great potential of ALD-grown TFTs for flexible display applications.

  7. Bulk and Thin Film Synthesis of Compositionally Variant Entropy-stabilized Oxides.

    PubMed

    Sivakumar, Sai; Zwier, Elizabeth; Meisenheimer, Peter Benjamin; Heron, John T

    2018-05-29

    Here, we present a procedure for the synthesis of bulk and thin film multicomponent (Mg0.25(1-x)CoxNi0.25(1-x)Cu0.25(1-x)Zn0.25(1-x))O (Co variant) and (Mg0.25(1-x)Co0.25(1-x)Ni0.25(1-x)CuxZn0.25(1-x))O (Cu variant) entropy-stabilized oxides. Phase pure and chemically homogeneous (Mg0.25(1-x)CoxNi0.25(1-x)Cu0.25(1-x)Zn0.25(1-x))O (x = 0.20, 0.27, 0.33) and (Mg0.25(1-x)Co0.25(1-x)Ni0.25(1-x)CuxZn0.25(1-x))O (x = 0.11, 0.27) ceramic pellets are synthesized and used in the deposition of ultra-high quality, phase pure, single crystalline thin films of the target stoichiometry. A detailed methodology for the deposition of smooth, chemically homogeneous, entropy-stabilized oxide thin films by pulsed laser deposition on (001)-oriented MgO substrates is described. The phase and crystallinity of bulk and thin film materials are confirmed using X-ray diffraction. Composition and chemical homogeneity are confirmed by X-ray photoelectron spectroscopy and energy dispersive X-ray spectroscopy. The surface topography of thin films is measured with scanning probe microscopy. The synthesis of high quality, single crystalline, entropy-stabilized oxide thin films enables the study of interface, size, strain, and disorder effects on the properties in this new class of highly disordered oxide materials.

  8. Misfit layered Ca{sub 3}Co{sub 4}O{sub 9} as a high figure of merit p-type transparent conducting oxide film through solution processing

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Aksit, M.; Kolli, S. K.; Slauch, I. M.

    Ca{sub 3}Co{sub 4}O{sub 9} thin films synthesized through solution processing are shown to be high-performing, p-type transparent conducting oxides (TCOs). The synthesis method is a cost-effective and scalable process that consists of sol-gel chemistry, spin coating, and heat treatments. The process parameters can be varied to produce TCO thin films with sheet resistance as low as 5.7 kΩ/sq (ρ ≈ 57 mΩ cm) or with average visible range transparency as high as 67%. The most conductive Ca{sub 3}Co{sub 4}O{sub 9} TCO thin film has near infrared region optical transmission as high as 85%. The figure of merit (FOM) for the top-performing Ca{sub 3}Co{submore » 4}O{sub 9} thin film (151 MΩ{sup −1}) is higher than FOM values reported in the literature for all other solution processed, p-type TCO thin films and higher than most others prepared by physical vapor deposition and chemical vapor deposition. Transparent conductivity in misfit layered oxides presents new opportunities for TCO compositions.« less

  9. High-temperature deformation and microstructural analysis for Si3N4-Sc2O3

    NASA Technical Reports Server (NTRS)

    Cheong, Deock-Soo; Sanders, William A.

    1990-01-01

    It was indicated that Si3N4 doped with Sc2O3 may exhibit high temperature mechanical properties superior to Si3N4 systems with various other oxide sintered additives. High temperature deformation of samples was studied by characterizing the microstructures before and after deformation. It was found that elements of the additive, such as Sc and O, exist in small amounts at very thin grain boundary layers and most of them stay in secondary phases at triple and multiple grain boundary junctions. These secondary phases are devitrified as crystalline Sc2Si2O7. Deformation of the samples was dominated by cavitational processes rather than movements of dislocations. Thus the excellent deformation resistance of the samples at high temperature can be attributed to the very small thickness of the grain boundary layers and the crystalline secondary phase.

  10. Facile One-pot Transformation of Iron Oxides from Fe2O3 Nanoparticles to Nanostructured Fe3O4@C Core-Shell Composites via Combustion Waves

    PubMed Central

    Shin, Jungho; Lee, Kang Yeol; Yeo, Taehan; Choi, Wonjoon

    2016-01-01

    The development of a low-cost, fast, and large-scale process for the synthesis and manipulation of nanostructured metal oxides is essential for incorporating materials with diverse practical applications. Herein, we present a facile one-pot synthesis method using combustion waves that simultaneously achieves fast reduction and direct formation of carbon coating layers on metal oxide nanostructures. Hybrid composites of Fe2O3 nanoparticles and nitrocellulose on the cm scale were fabricated by a wet impregnation process. We demonstrated that self-propagating combustion waves along interfacial boundaries between the surface of the metal oxide and the chemical fuels enabled the release of oxygen from Fe2O3. This accelerated reaction directly transformed Fe2O3 into Fe3O4 nanostructures. The distinctive color change from reddish-brown Fe2O3 to dark-gray Fe3O4 confirmed the transition of oxidation states and the change in the fundamental properties of the material. Furthermore, it simultaneously formed carbon layers of 5–20 nm thickness coating the surfaces of the resulting Fe3O4 nanoparticles, which may aid in maintaining the nanostructures and improving the conductivity of the composites. This newly developed use of combustion waves in hybridized nanostructures may permit the precise manipulation of the chemical compositions of other metal oxide nanostructures, as well as the formation of organic/inorganic hybrid nanostructures. PMID:26902260

  11. Sensitization of Nanocrystalline Metal Oxides with a Phosphonate-Functionalized Perylene Diimide for Photoelectrochemical Water Oxidation with a CoO x Catalyst

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kirner, Joel T.; Finke, Richard G.

    A planar organic thin film composed of a perylene diimide dye (N,N'-bis(phosphonomethyl)-3,4,9,10-perylenediimide, PMPDI) with photoelectrochemically deposited cobalt oxide (CoO x) catalyst was previously shown to photoelectrochemically oxidize water (DOI: 10.1021/am405598w). Herein, the same PMPDI dye is studied for the sensitization of different nanostructured metal oxide (nano-MO x) films in a dye-sensitized photoelectrochemical cell architecture. Dye adsorption kinetics and saturation decreases in the order TiO 2 > SnO 2 >> WO 3. Despite highest initial dye loading on TiO 2 films, photocurrent with hydroquinone (H 2Q) sacrificial reductant in pH 7 aqueous solution is much higher on SnO 2 films, likelymore » due to a higher driving force for charge injection into the more positive conduction band energy of SnO 2. Dyeing conditions and SnO 2 film thickness were subsequently optimized to achieve light-harvesting efficiency >99% at the λmax of the dye, and absorbed photon-to-current efficiency of 13% with H 2Q, a 2-fold improvement over the previous thin-film architecture. A CoO x water-oxidation catalyst was photoelectrochemically deposited, allowing for photoelectrochemical water oxidation with a faradaic efficiency of 31 ± 7%, thus demonstrating the second example of a water-oxidizing, dye-sensitized photoelectrolysis cell composed entirely of earth-abundant materials. However, deposition of CoO x always results in lower photocurrent due to enhanced recombination between catalyst and photoinjected electrons in SnO 2, as confirmed by open-circuit photovoltage measurements. Possible future studies to enhance photoanode performance are also discussed, including alternative catalyst deposition strategies or structural derivatization of the perylene dye.« less

  12. Sensitization of Nanocrystalline Metal Oxides with a Phosphonate-Functionalized Perylene Diimide for Photoelectrochemical Water Oxidation with a CoO x Catalyst

    DOE PAGES

    Kirner, Joel T.; Finke, Richard G.

    2017-07-20

    A planar organic thin film composed of a perylene diimide dye (N,N'-bis(phosphonomethyl)-3,4,9,10-perylenediimide, PMPDI) with photoelectrochemically deposited cobalt oxide (CoO x) catalyst was previously shown to photoelectrochemically oxidize water (DOI: 10.1021/am405598w). Herein, the same PMPDI dye is studied for the sensitization of different nanostructured metal oxide (nano-MO x) films in a dye-sensitized photoelectrochemical cell architecture. Dye adsorption kinetics and saturation decreases in the order TiO 2 > SnO 2 >> WO 3. Despite highest initial dye loading on TiO 2 films, photocurrent with hydroquinone (H 2Q) sacrificial reductant in pH 7 aqueous solution is much higher on SnO 2 films, likelymore » due to a higher driving force for charge injection into the more positive conduction band energy of SnO 2. Dyeing conditions and SnO 2 film thickness were subsequently optimized to achieve light-harvesting efficiency >99% at the λmax of the dye, and absorbed photon-to-current efficiency of 13% with H 2Q, a 2-fold improvement over the previous thin-film architecture. A CoO x water-oxidation catalyst was photoelectrochemically deposited, allowing for photoelectrochemical water oxidation with a faradaic efficiency of 31 ± 7%, thus demonstrating the second example of a water-oxidizing, dye-sensitized photoelectrolysis cell composed entirely of earth-abundant materials. However, deposition of CoO x always results in lower photocurrent due to enhanced recombination between catalyst and photoinjected electrons in SnO 2, as confirmed by open-circuit photovoltage measurements. Possible future studies to enhance photoanode performance are also discussed, including alternative catalyst deposition strategies or structural derivatization of the perylene dye.« less

  13. Process for producing Ti-Cr-Al-O thin film resistors

    DOEpatents

    Jankowski, Alan F.; Schmid, Anthony P.

    2001-01-01

    Thin films of Ti-Cr-Al-O are used as a resistor material. The films are rf sputter deposited from ceramic targets using a reactive working gas mixture of Ar and O.sub.2. Resistivity values from 10.sup.4 to 10.sup.10 Ohm-cm have been measured for Ti-Cr-Al-O film <1 .mu.m thick. The film resistivity can be discretely selected through control of the target composition and the deposition parameters. The application of Ti-Cr-Al-O as a thin film resistor has been found to be thermodynamically stable, unlike other metal-oxide films. The Ti-Cr-Al-O film can be used as a vertical or lateral resistor, for example, as a layer beneath a field emission cathode in a flat panel display; or used to control surface emissivity, for example, as a coating on an insulating material such as vertical wall supports in flat panel displays.

  14. Flat panel display using Ti-Cr-Al-O thin film

    DOEpatents

    Jankowski, Alan F.; Schmid, Anthony P.

    2002-01-01

    Thin films of Ti--Cr--Al--O are used as a resistor material. The films are rf sputter deposited from ceramic targets using a reactive working gas mixture of Ar and O.sub.2. Resistivity values from 10.sup.4 to 10.sup.10 Ohm-cm have been measured for Ti--Cr--Al--O film <1 .mu.m thick. The film resistivity can be discretely selected through control of the target composition and the deposition parameters. The application of Ti--Cr--Al--O as a thin film resistor has been found to be thermodynamically stable, unlike other metal-oxide films. The Ti--Cr--Al--O film can be used as a vertical or lateral resistor, for example, as a layer beneath a field emission cathode in a flat panel display; or used to control surface emissivity, for example, as a coating on an insulating material such as vertical wall supports in flat panel displays.

  15. Coaxial metal-oxide-semiconductor (MOS) Au/Ga2O3/GaN nanowires.

    PubMed

    Hsieh, Chin-Hua; Chang, Mu-Tung; Chien, Yu-Jen; Chou, Li-Jen; Chen, Lih-Juann; Chen, Chii-Dong

    2008-10-01

    Coaxial metal-oxide-semiconductor (MOS) Au-Ga2O3-GaN heterostructure nanowires were successfully fabricated by an in situ two-step process. The Au-Ga2O3 core-shell nanowires were first synthesized by the reaction of Ga powder, a mediated Au thin layer, and a SiO2 substrate at 800 degrees C. Subsequently, these core-shell nanowires were nitridized in ambient ammonia to form a GaN coating layer at 600 degrees C. The GaN shell is a single crystal, an atomic flat interface between the oxide and semiconductor that ensures that the high quality of the MOS device is achieved. These novel 1D nitride-based MOS nanowires may have promise as building blocks to the future nitride-based vertical nanodevices.

  16. Role of flue gas components in mercury oxidation over TiO2 supported MnOx-CeO2 mixed-oxide at low temperature.

    PubMed

    Li, Hailong; Wu, Chang-Yu; Li, Ying; Li, Liqing; Zhao, Yongchun; Zhang, Junying

    2012-12-01

    MnO(x)-CeO(2) mixed-oxide supported on TiO(2) (Mn-Ce/Ti) was synthesized by an ultrasound-assisted impregnation method and employed to oxidize elemental mercury (Hg(0)) at 200°C in simulated coal combustion flue gas. Over 90% of Hg(0) oxidation was achieved on the Mn-Ce/Ti catalyst at 200°C under simulated flue gas representing those from burning low-rank coals with a high gas hourly space velocity of 60,000 h(-1). Gas-phase O(2) regenerated the lattice oxygen and replenished the chemisorbed oxygen, which facilitated Hg(0) oxidation. HCl was the most effective flue gas component responsible for Hg(0) oxidation. 10 ppm HCl plus 4% O(2) resulted in 100% Hg(0) oxidation under the experimental conditions. SO(2) competed with Hg(0) for active sites, thus deactivating the catalyst's capability in oxidizing Hg(0). NO covered the active sites and consumed surface oxygen active for Hg(0) oxidation, hence limiting Hg(0) oxidation. Water vapor showed prohibitive effect on Hg(0) oxidation due to its competition with HCl and Hg(0) for active adsorption sites. This study provides information about the promotional or inhibitory effects of individual flue gas components on Hg(0) oxidation over a highly effective Mn-Ce/Ti catalyst. Such knowledge is of fundamental importance for industrial applications of the Mn-Ce/Ti catalyst in coal-fired power plants. Copyright © 2012 Elsevier B.V. All rights reserved.

  17. QCM gas sensor characterization of ALD-grown very thin TiO2 films

    NASA Astrophysics Data System (ADS)

    Boyadjiev, S.; Georgieva, V.; Vergov, L.; Szilágyi, I. M.

    2018-03-01

    The paper presents a technology for preparation and characterization of titanium dioxide (TiO2) thin films suitable for gas sensor applications. Applying atomic layer deposition (ALD), very thin TiO2 films were deposited on quartz resonators, and their gas sensing properties were studied using the quartz crystal microbalance (QCM) method. The TiO2 thin films were grown using Ti(iOPr)4 and water as precursors. The surface of the films was observed by scanning electron microscopy (SEM), coupled with energy dispersive X-ray analysis (EDX) used for a composition study. The research was focused on the gas-sensing properties of the films. Films of 10-nm thickness were deposited on quartz resonators with Au electrodes and the QCMs were used to build highly sensitive gas sensors, which were tested for detecting NO2. Although very thin, these ALD-grown TiO2 films were sensitive to NO2 already at room temperature and could register as low concentrations as 50 ppm, while the sorption was fully reversible, and the sensors could be fully recovered. With the technology presented, the manufacturing of gas sensors is simple, fast and cost-effective, and suitable for energy-effective portable equipment for real-time environmental monitoring of NO2.

  18. Synthesis of ZnO thin film by sol-gel spin coating technique for H2S gas sensing application

    NASA Astrophysics Data System (ADS)

    Nimbalkar, Amol R.; Patil, Maruti G.

    2017-12-01

    In this present work, zinc oxide (ZnO) thin film synthesized by a simple sol-gel spin coating technique. The structural, morphology, compositional, microstructural, optical, electrical and gas sensing properties of the film were studied by using XRD, FESEM, EDS, XPS, HRTEM, Raman, FTIR and UV-vis techniques. The ZnO thin film shows hexagonal wurtzite structure with a porous structured morphology. Gas sensing performance of synthesized ZnO thin film was tested initially for H2S gas at different operating temperatures as well as concentrations. The maximum gas response is achieved towards H2S gas at 300 °C operating temperature, at 100 ppm gas concentration as compared to other gases like CH3OH, Cl2, NH3, LPG, CH3COCH3, and C2H5OH with a good stability.

  19. Preparation and Characterization of PbO-SrO-Na2O-Nb2O5-SiO2 Glass Ceramics Thin Film for High-Energy Storage Application

    NASA Astrophysics Data System (ADS)

    Tan, Feihu; Zhang, Qingmeng; Zhao, Hongbin; Wei, Feng; Du, Jun

    2018-03-01

    PbO-SrO-Na2O-Nb2O5-SiO2 (PSNNS) glass ceramic thin films were prepared by pulsed laser deposition technology on heavily doped silicon substrates. The influence of annealing temperatures on microstructures, dielectric properties and energy storage performances of the as-prepared films were investigated in detail. X-ray diffraction studies indicate that Pb2Nb2O7 crystallizes at 800°C and disappears at 900°C, while NaNbO3 and PbNb2O6 are formed at the higher temperature of 900°C. The dielectric properties of the glass ceramics thin films have a strong dependence on the phase assemblages that are developed during heat treatment. The maximum dielectric constant value of 171 was obtained for the film annealed at 800°C, owing to the high electric breakdown field strength, The energy storage densities of the PSNNS films annealed at 800°C were as large as 36.9 J/cm3, These results suggest that PSNNS thin films are promising for energy storage applications.

  20. Preparation of Hollow CuO@SiO2 Spheres and Its Catalytic Performances for the NO + CO and CO Oxidation

    PubMed Central

    Niu, Xiaoyu; Zhao, Tieying; Yuan, Fulong; Zhu, Yujun

    2015-01-01

    The hollow CuO@SiO2 spheres with a mean diameter of 240 nm and a thin shell layer of about 30 nm in thickness was synthesized using an inorganic SiO2 shell coating on the surface of Cu@C composite that was prepared by a two-step hydrothermal method. The obtained hollow CuO@SiO2 spheres were characterized by ICP-AES, nitrogen adsorption-desorption, SEM, TEM, XRD, H2-TPR, CO-TPR, CO-TPD and NO-TPD. The results revealed that the hollow CuO@SiO2 spheres consist of CuO uniformly inserted into SiO2 layer. The CuO@SiO2 sample exhibits particular catalytic activities for CO oxidation and NO + CO reactions compared with CuO supported on SiO2 (CuO/SiO2). The higher catalytic activity is attributed to the special hollow shell structure that possesses much more highly dispersed CuO nanocluster that can be easy toward the CO and NO adsorption and the oxidation of CO on its surface. PMID:25777579

  1. Incommensurate spin correlations in highly oxidized cobaltates La2−xSrxCoO4

    PubMed Central

    Li, Z. W.; Drees, Y.; Kuo, C. Y.; Guo, H.; Ricci, A.; Lamago, D.; Sobolev, O.; Rütt, U.; Gutowski, O.; Pi, T. W.; Piovano, A.; Schmidt, W.; Mogare, K.; Hu, Z.; Tjeng, L. H.; Komarek, A. C.

    2016-01-01

    We observe quasi-static incommensurate magnetic peaks in neutron scattering experiments on layered cobalt oxides La2−xSrxCoO4 with high Co oxidation states that have been reported to be paramagnetic. This enables us to measure the magnetic excitations in this highly hole-doped incommensurate regime and compare our results with those found in the low-doped incommensurate regime that exhibit hourglass magnetic spectra. The hourglass shape of magnetic excitations completely disappears given a high Sr doping. Moreover, broad low-energy excitations are found, which are not centered at the incommensurate magnetic peak positions but around the quarter-integer values that are typically exhibited by excitations in the checkerboard charge ordered phase. Our findings suggest that the strong inter-site exchange interactions in the undoped islands are critical for the emergence of hourglass spectra in the incommensurate magnetic phases of La2−xSrxCoO4. PMID:27117928

  2. Highly efficient extraction and oxidative desulfurization system using Na7H2LaW10O36⋅32 H2O in [bmim]BF4 at room temperature.

    PubMed

    Xu, Junhua; Zhao, Shen; Chen, Wei; Wang, Miao; Song, Yu-Fei

    2012-04-10

    Highly efficient, deep desulfurization of model oil containing dibenzothiophene (DBT), benzothiophene (BT), or 4,6-dimethyldibenzothiophene (4,6-DMDBT) has been achieved under mild conditions by using an extraction and catalytic oxidative desulfurization system (ECODS) in which a lanthanide-containing polyoxometalate Na(7)H(2)LnW(10)O(36)⋅32 H(2)O (LnW(10); Ln = Eu, La) acts as catalyst, [bmim]BF(4) (bmim = 1-butyl-3-methylimidazolium) as extractant, and H(2)O(2) as oxidant. Sulfur removal follows the order DBT>4,6-DMDBT>BT at 30 °C. DBT can be completely oxidized to the corresponding sulfone in 25 min under mild conditions, and the LaW(10)/[bmim]BF(4) system could be recycled for ten times with only slight decrease in activity. Thus, LaW(10) in [bmim]BF(4) is one of the most efficient systems for desulfurization using ionic liquids as extractant reported so far. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Nanocrystalline SnO2:F thin films for liquid petroleum gas sensors.

    PubMed

    Chaisitsak, Sutichai

    2011-01-01

    This paper reports the improvement in the sensing performance of nanocrystalline SnO(2)-based liquid petroleum gas (LPG) sensors by doping with fluorine (F). Un-doped and F-doped tin oxide films were prepared on glass substrates by the dip-coating technique using a layer-by-layer deposition cycle (alternating between dip-coating a thin layer followed by a drying in air after each new layer). The results showed that this technique is superior to the conventional technique for both improving the film thickness uniformity and film transparency. The effect of F concentration on the structural, surface morphological and LPG sensing properties of the SnO(2) films was investigated. Atomic Force Microscopy (AFM) and X-ray diffraction pattern measurements showed that the obtained thin films are nanocrystalline SnO(2) with nanoscale-textured surfaces. Gas sensing characteristics (sensor response and response/recovery time) of the SnO(2):F sensors based on a planar interdigital structure were investigated at different operating temperatures and at different LPG concentrations. The addition of fluorine to SnO(2) was found to be advantageous for efficient detection of LPG gases, e.g., F-doped sensors are more stable at a low operating temperature (300 °C) with higher sensor response and faster response/recovery time, compared to un-doped sensor materials. The sensors based on SnO(2):F films could detect LPG even at a low level of 25% LEL, showing the possibility of using this transparent material for LPG leak detection.

  4. Nanocrystalline SnO2:F Thin Films for Liquid Petroleum Gas Sensors

    PubMed Central

    Chaisitsak, Sutichai

    2011-01-01

    This paper reports the improvement in the sensing performance of nanocrystalline SnO2-based liquid petroleum gas (LPG) sensors by doping with fluorine (F). Un-doped and F-doped tin oxide films were prepared on glass substrates by the dip-coating technique using a layer-by-layer deposition cycle (alternating between dip-coating a thin layer followed by a drying in air after each new layer). The results showed that this technique is superior to the conventional technique for both improving the film thickness uniformity and film transparency. The effect of F concentration on the structural, surface morphological and LPG sensing properties of the SnO2 films was investigated. Atomic Force Microscopy (AFM) and X-ray diffraction pattern measurements showed that the obtained thin films are nanocrystalline SnO2 with nanoscale-textured surfaces. Gas sensing characteristics (sensor response and response/recovery time) of the SnO2:F sensors based on a planar interdigital structure were investigated at different operating temperatures and at different LPG concentrations. The addition of fluorine to SnO2 was found to be advantageous for efficient detection of LPG gases, e.g., F-doped sensors are more stable at a low operating temperature (300 °C) with higher sensor response and faster response/recovery time, compared to un-doped sensor materials. The sensors based on SnO2:F films could detect LPG even at a low level of 25% LEL, showing the possibility of using this transparent material for LPG leak detection. PMID:22164007

  5. Development and Research on the Mechanism of Novel Mist Etching Method for Oxide Thin Films

    NASA Astrophysics Data System (ADS)

    Kawaharamura, Toshiyuki; Hirao, Takashi

    2012-03-01

    A novel etching process with etchant mist was developed and applied to oxide thin films such as zinc oxide (ZnO), zinc magnesium oxide (ZnMgO), and indium tin oxide (ITO). By using this process, it was shown that precise control of the etching characteristics is possible with a reasonable etching rate, for example, in the range of 10-100 nm/min, and a fine pattern of high accuracy can also be realized, even though this is usually very difficult by conventional wet etching processes, for ZnO and ZnMgO. The mist etching process was found to be similarly and successfully applied to ITO. The mechanism of mist etching has been studied by examining the etching temperature dependence of pattern accuracy, and it was shown that the mechanism was different from that of conventional liquid-phase spray etching. It was ascertained that fine pattern etching was attained using mist droplets completely (or partly) gasified by the heat applied to the substrate. This technique was applied to the fabrication of a ZnO thin-film transistor (TFT) with a ZnO active channel length of 4 µm. The electrical properties of the TFT were found to be excellent with fine uniformity over the entire 4-in. wafer.

  6. Optical and structural properties of Al-doped ZnO thin films by sol gel process.

    PubMed

    Jun, Min-Chul; Koh, Jung-Hyuk

    2013-05-01

    Transparent conducting oxide (TCO) materials with high transmittance and good electrical conductivity have been attracted much attention due to the development of electronic display and devices such as organic light emitting diodes (OLEDs), and dye-sensitized solar cells (DSSCs). Aluminum doped zinc oxide thin films (AZO) have been well known for their use as TCO materials due to its stability, cost-effectiveness, good optical transmittance and electrical properties. Especially, AZO thin film, which have low resistivity of 2-4 x 10(-4) omega x cm which is similar to that of ITO films with wide band gap semiconductors. The AZO thin films were deposited on glass substrates by sol-gel spin-coating process. As a starting material, zinc acetate dihydrate (Zn(CH3COO)2 x 2H2O) and aluminum chloride hexahydrate (AlCl3 6H2O) were used. 2-methoxyethanol and monoethanolamine (MEA) were used as solvent and stabilizer, respectively. After deposited, the films were preheated at 300 degrees C on a hotplate and post-heated at 650 degrees C for 1.5 hrs in the furnace. We have studied the structural and optical properties as a function of Al concentration (0-2.5 mol.%).

  7. V2O5 thin film deposition for application in organic solar cells

    NASA Astrophysics Data System (ADS)

    Arbab, Elhadi A. A.; Mola, Genene Tessema

    2016-04-01

    Vanadium pentoxide V2O5 films were fabricated by way of electrochemical deposition technique for application as hole transport buffer layer in organic solar cell. A thin and uniform V2O5 films were successfully deposited on indium tin oxide-coated glass substrate. The characterization of surface morphology and optical properties of the deposition suggest that the films are suitable for photovoltaic application. Organic solar cell fabricated using V2O5 as hole transport buffer layer showed better devices performance and environmental stability than those devices fabricated with PEDOT:PSS. In an ambient device preparation condition, the power conversion efficiency increases by nearly 80 % compared with PEDOT:PSS-based devices. The devices lifetime using V2O5 buffer layer has improved by a factor of 10 over those devices with PEDOT:PSS.

  8. Enhanced photoelectrochemical and photocatalytic activity of WO3-surface modified TiO2 thin film

    NASA Astrophysics Data System (ADS)

    Qamar, Mohammad; Drmosh, Qasem; Ahmed, Muhammad I.; Qamaruddin, Muhammad; Yamani, Zain H.

    2015-02-01

    Development of nanostructured photocatalysts for harnessing solar energy in energy-efficient and environmentally benign way remains an important area of research. Pure and WO3-surface modified thin films of TiO2 were prepared by magnetron sputtering on indium tin oxide glass, and photoelectrochemical and photocatalytic activities of these films were studied. TiO2 particles were <50 nm, while deposited WO3 particles were <20 nm in size. An enhancement in the photocurrent was observed when the TiO2 surface was modified WO3 nanoparticles. Effect of potential, WO3 amount, and radiations of different wavelengths on the photoelectrochemical activity of TiO2 electrodes was investigated. Photocatalytic activity of TiO2 and WO3-modified TiO2 for the decolorization of methyl orange was tested.

  9. Hot-Pressed Versus Sintered LiTi2(PO4)3

    DTIC Science & Technology

    2009-02-01

    Goretta, K. J. Mat. Lett. 1988, 6, 217. 30. Nieh, T.-G.; Wadsworth, J. J. Am. Ceram. Soc. 1989, 72, 1469. 31. Carry, C.; Mocellin , A. Ceram. Inter...1987, 13, 89. 32. Fridez, C. D.; Carry, C.; Mocellin , A. in Advances in Ceramics Vol. 10, Structure and Property of MgO and Al2O3 Ceramics. ed. W.D

  10. Microstructure of ZnO Thin Films Deposited by High Power Impulse Magnetron Sputtering (Postprint)

    DTIC Science & Technology

    2015-03-01

    AFRL-RX-WP-JA-2015-0185 MICROSTRUCTURE OF ZNO THIN FILMS DEPOSITED BY HIGH POWER IMPULSE MAGNETRON SPUTTERING (POSTPRINT) A. N. Reed...COVERED (From – To) 29 January 2013 – 16 February 2015 4. TITLE AND SUBTITLE MICROSTRUCTURE OF ZNO THIN FILMS DEPOSITED BY HIGH POWER IMPULSE MAGNETRON...ABSTRACT High power impulse magnetron sputtering was used to deposit thin (~100 nm) zinc oxide (ZnO) films from a ceramic ZnO target onto substrates

  11. Epitaxial growth of YBa2Cu3O7 - delta films on oxidized silicon with yttria- and zirconia-based buffer layers

    NASA Astrophysics Data System (ADS)

    Pechen, E. V.; Schoenberger, R.; Brunner, B.; Ritzinger, S.; Renk, K. F.; Sidorov, M. V.; Oktyabrsky, S. R.

    1993-09-01

    A study of epitaxial growth of YBa2Cu3O7-δ films on oxidized Si with yttria- and zirconia-based buffer layers is reported. Using substrates with either SiO2 free or naturally oxidized (100) surfaces of Si it was found that a thin SiO2 layer on top of the Si favors high-quality superconducting film formation. Compared to yttria-stabilized ZrO2 (YSZ) single layers, YSZY2O3 double and YSZ/Y2O3YSZ triple layers allows the deposition of thin YBa2Cu3O7-δ films with improved properties including reduced aging effects. In epitaxial YBa2Cu3O7-δ films grown on the double buffer layers a critical temperature Tc(R=0)=89.5 K and critical current densities of 3.5×106 A/cm2 at 77 K and 1×107 A/cm2 at 66 K were reached.

  12. Morphology, composition and electrical properties of SnO{sub 2}:Cl thin films grown by atomic layer deposition

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Cheng, Hsyi-En, E-mail: sean@mail.stust.edu.tw; Wen, Chia-Hui; Hsu, Ching-Ming

    2016-01-15

    Chlorine doped SnO{sub 2} thin films were prepared using atomic layer deposition at temperatures between 300 and 450 °C using SnCl{sub 4} and H{sub 2}O as the reactants. Composition, structure, surface morphology, and electrical properties of the as-deposited films were examined. Results showed that the as-deposited SnO{sub 2} films all exhibited rutile structure with [O]/[Sn] ratios between 1.35 and 1.40. The electrical conductivity was found independent on [O]/[Sn] ratio but dependent on chlorine doping concentration, grain size, and surface morphology. The 300 °C-deposited film performed a higher electrical conductivity of 315 S/cm due to its higher chlorine doping level, larger grain size, andmore » smoother film surface. The existence of Sn{sup 2+} oxidation state was demonstrated to minimize the effects of chlorine on raising the electrical conductivity of films.« less

  13. Hierarchically Structured Co3O4@Pt@MnO2 Nanowire Arrays for High-Performance Supercapacitors

    PubMed Central

    Xia, Hui; Zhu, Dongdong; Luo, Zhentao; Yu, Yue; Shi, Xiaoqin; Yuan, Guoliang; Xie, Jianping

    2013-01-01

    Here we proposed a novel architectural design of a ternary MnO2-based electrode – a hierarchical Co3O4@Pt@MnO2 core-shell-shell structure, where the complemental features of the three key components (a well-defined Co3O4 nanowire array on the conductive Ti substrate, an ultrathin layer of small Pt nanoparticles, and a thin layer of MnO2 nanoflakes) are strategically combined into a single entity to synergize and construct a high-performance electrode for supercapacitors. Owing to the high conductivity of the well-defined Co3O4 nanowire arrays, in which the conductivity was further enhanced by a thin metal (Pt) coating layer, in combination with the large surface area provided by the small MnO2 nanoflakes, the as-fabricated Co3O4@Pt@MnO2 nanowire arrays have exhibited high specific capacitances, good rate capability, and excellent cycling stability. The architectural design demonstrated in this study provides a new approach to fabricate high-performance MnO2–based nanowire arrays for constructing next-generation supercapacitors. PMID:24132040

  14. Evolution of magnetic properties in the vicinity of the Verwey transition in Fe3O4 thin films

    NASA Astrophysics Data System (ADS)

    Liu, X. H.; Liu, W.; Zhang, Z. D.

    2017-09-01

    We have systematically studied the evolution of magnetic properties, especially the coercivity and the remanence ratio in the vicinity of the Verwey transition temperature (TV), of high-quality epitaxial Fe3O4 thin films grown on MgO (001), MgAl2O4 (MAO) (001), and SrTiO3 (STO) (001) substrates. We observed rapid change of magnetization, coercivity, and remanence ratio at TV, which are consistent with the behaviors of resistivity versus temperature [ρ (T )] curves for the different thin films. In particular, we found quite different magnetic behaviors for the thin films on MgO from those on MAO and STO, in which the domain size and the strain state play very important roles. The coercivity is mainly determined by the domain size but the demagnetization process is mainly dependent on the strain state. Furthermore, we observed a reversal of remanence ratio at TV with thickness for the thin films grown on MgO: from a rapid enhancement for 40-nm- to a sharp drop for 200-nm-thick film, and the critical thickness is about 80 nm. Finally, we found an obvious hysteretic loop of coercivity (or remanence ratio) with temperature around TV, corresponding to the hysteretic loop of the ρ (T ) curve, in Fe3O4 thin film grown on MgO.

  15. Spray pyrolysed Ru:TiO2 thin film electrodes prepared for electrochemical supercapacitor

    NASA Astrophysics Data System (ADS)

    Fugare, B. Y.; Thakur, A. V.; Kore, R. M.; Lokhande, B. J.

    2018-04-01

    Ru doped TiO2 thin films are prepared by using 0.06 M aqueous solution of potassium titanium oxalate (pto), and 0.005 M aqueous solution of ruthenium tri chloride (RuCl3) precursors. The deposition was carried on stainless steel (SS) by using well known ultrasonic spray pyrolysis technique (USPT) at 723° K by maintaining the spray rate 12 cc/min and compressed air flow rate 10 Lmin-1. Prepared Ru:TiO2 thin films were characterized by structurally, morphologically and electrochemically. Deposited RuO2 shows amorphous structure and TiO2 shows tetragonal crystal structure with rutile as prominent phase at very low decomposition temperature. SEM micrographs of RuO2 exhibits porous, interconnected, spherical grains type morphology and TiO2 shows porous, nanorods and nanoplates like morphology and also Ru doped TiO2 shows porous, spherical, granular and nanorods type morphology. The electrochemical cyclic voltammetery shows mixed capacitive behavior. The achieved highest value of specific capacitance 2692 F/g was Ru doped TiO2 electrode in 0.5 M H2SO4.

  16. Micropatterning of TiO2 thin films by MOCVD and study of their growth tendency.

    PubMed

    Hwang, Ki-Hwan; Kang, Byung-Chang; Jung, Duk Young; Kim, Youn Jea; Boo, Jin-Hyo

    2015-03-23

    In this work, we studied the growth tendency of TiO2 thin films deposited on a narrow-stripe area (<10 μm). TiO2 thin films were selectively deposited on OTS patterned Si(100) substrates by MOCVD. The experimental data showed that the film growth tendency was divided into two behaviors above and below a line patterning width of 4 μm. The relationship between the film thickness and the deposited area was obtained as a function of f(x) = a[1 - e((-bx))]c. To find the tendency of the deposition rate of the TiO2 thin films onto the various linewidth areas, the relationship between the thickness of the TiO2 thin film and deposited linewidth was also studied. The thickness of the deposited TiO2 films was measured from the alpha-step profile analyses and cross-sectional SEM images. At the same time, a computer simulation was carried out to reveal the relationship between the TiO2 film thickness and deposited line width. The theoretical results suggest that the mass (velocity) flux in flow direction is directly affected to the film thickness.

  17. Switching of magnetic easy-axis using crystal orientation for large perpendicular coercivity in CoFe2O4 thin film

    PubMed Central

    Shirsath, Sagar E.; Liu, Xiaoxi; Yasukawa, Yukiko; Li, Sean; Morisako, Akimitsu

    2016-01-01

    Perpendicular magnetization and precise control over the magnetic easy axis in magnetic thin film is necessary for a variety of applications, particularly in magnetic recording media. A strong (111) orientation is successfully achieved in the CoFe2O4 (CFO) thin film at relatively low substrate temperature of 100 °C, whereas the (311)-preferred randomly oriented CFO is prepared at room temperature by the DC magnetron sputtering technique. The oxygen-deficient porous CFO film after post-annealing gives rise to compressive strain perpendicular to the film surface, which induces large perpendicular coercivity. We observe the coercivity of 11.3 kOe in the 40-nm CFO thin film, which is the highest perpendicular coercivity ever achieved on an amorphous SiO2/Si substrate. The present approach can guide the systematic tuning of the magnetic easy axis and coercivity in the desired direction with respect to crystal orientation in the nanoscale regime. Importantly, this can be achieved on virtually any type of substrate. PMID:27435010

  18. Comparative optical studies of ZnO and ZnO-TiO2 - Metal oxide nanoparticle

    NASA Astrophysics Data System (ADS)

    Vijayalakshmi, R. Vanathi; Asvini, V.; Kumar, P. Praveen; Ravichandran, K.

    2018-05-01

    A comparative study was carried out to show the enhancement in optical activity of bimetal oxide nanoparticle (ZnO - TiO2) than metal oxide nanoparticle (ZnO), which can preferably be used for optical applications. The samples were prepared by wet chemical method and crystalline structure of the samples as hexagonal - primitive for ZnO and tetragonal - bcc for ZnO-TiO2 was confirmed by XRD measurements. The average grain size of ZnO - 19.89nm and ZnO-TiO2- 49.89 nm was calculated by Debye- Scherrer formula. The structure and particle size of the sample was analyzed by FESEM images. The direct band gap energy of ZnO (3.9eV) and ZnO - TiO2(4.68eV) was calculated by Kubelka-Munk Function, from which it is clear that the band gap energy increases in bimetal oxide to a desired level than in its pure form. The photoluminescence study shows that the emitted wavelength of the samples lies exactly around the visible region.

  19. Decomposition of 3,5-dinitrobenzamide in aqueous solution during UV/H2O2 and UV/TiO2 oxidation processes.

    PubMed

    Yan, Yingjie; Liao, Qi-Nan; Ji, Feng; Wang, Wei; Yuan, Shoujun; Hu, Zhen-Hu

    2017-02-01

    3,5-Dinitrobenzamide has been widely used as a feed additive to control coccidiosis in poultry, and part of the added 3,5-dinitrobenzamide is excreted into wastewater and surface water. The removal of 3,5-dinitrobenzamide from wastewater and surface water has not been reported in previous studies. Highly reactive hydroxyl radicals from UV/hydrogen peroxide (H 2 O 2 ) and UV/titanium dioxide (TiO 2 ) advanced oxidation processes (AOPs) can decompose organic contaminants efficiently. In this study, the decomposition of 3,5-dinitrobenzamide in aqueous solution during UV/H 2 O 2 and UV/TiO 2 oxidation processes was investigated. The decomposition of 3,5-dinitrobenzamide fits well with a fluence-based pseudo-first-order kinetics model. The decomposition in both two oxidation processes was affected by solution pH, and was inhibited under alkaline conditions. Inorganic anions such as NO 3 - , Cl - , SO 4 2- , HCO 3 - , and CO 3 2- inhibited the degradation of 3,5-dinitrobenzamide during the UV/H 2 O 2 and UV/TiO 2 oxidation processes. After complete decomposition in both oxidation processes, approximately 50% of 3,5-dinitrobenzamide was decomposed into organic intermediates, and the rest was mineralized to CO 2 , H 2 O, and other inorganic anions. Ions such as NH 4 + , NO 3 - , and NO 2 - were released into aqueous solution during the degradation. The primary decomposition products of 3,5-dinitrobenzamide were identified using time-of-flight mass spectrometry (LCMS-IT-TOF). Based on these products and ions release, a possible decomposition pathway of 3,5-dinitrobenzamide in both UV/H 2 O 2 and UV/TiO 2 processes was proposed.

  20. Regulation of the forming process and the set voltage distribution of unipolar resistance switching in spin-coated CoFe2O4 thin films.

    PubMed

    Mustaqima, Millaty; Yoo, Pilsun; Huang, Wei; Lee, Bo Wha; Liu, Chunli

    2015-01-01

    We report the preparation of (111) preferentially oriented CoFe2O4 thin films on Pt(111)/TiO2/SiO2/Si substrates using a spin-coating process. The post-annealing conditions and film thickness were varied for cobalt ferrite (CFO) thin films, and Pt/CFO/Pt structures were prepared to investigate the resistance switching behaviors. Our results showed that resistance switching without a forming process is preferred to obtain less fluctuation in the set voltage, which can be regulated directly from the preparation conditions of the CFO thin films. Therefore, instead of thicker film, CFO thin films deposited by two times spin-coating with a thickness about 100 nm gave stable resistance switching with the most stable set voltage. Since the forming process and the large variation in set voltage have been considered as serious obstacles for the practical application of resistance switching for non-volatile memory devices, our results could provide meaningful insights in improving the performance of ferrite material-based resistance switching memory devices.

  1. Excision of uranium oxide chains and ribbons in the novel one-dimensional uranyl iodates K(2)[(UO(2))3(IO(3))(4)O(2)] and Ba[(UO(2)2(IO(3))(2)O(2)](H(2)O).

    PubMed

    Bean, A C; Ruf, M; Albrecht-Schmitt, T E

    2001-07-30

    The alkali metal and alkaline-earth metal uranyl iodates K(2)[(UO(2))(3)(IO(3))(4)O(2)] and Ba[(UO(2))(2)(IO(3))(2)O(2)](H(2)O) have been prepared from the hydrothermal reactions of KCl or BaCl(2) with UO(3) and I(2)O(5) at 425 and 180 degrees C, respectively. While K(2)[(UO(2))(3)(IO(3))(4)O(2)] can be synthesized under both mild and supercritical conditions, the yield increases from <5% to 73% as the temperature is raised from 180 to 425 degrees C. Ba[(UO(2))(2)(IO(3))(2)O(2)](H(2)O), however, has only been isolated from reactions performed in the mild temperature regime. Thermal measurements (DSC) indicate that K(2)[(UO(2))(3)(IO(3))(4)O(2)] is more stable than Ba[(UO(2))(2)(IO(3))(2)O(2)](H(2)O) and that both compounds decompose through thermal disproportionation at 579 and 575 degrees C, respectively. The difference in the thermal behavior of these compounds provides a basis for the divergence of their preparation temperatures. The structure of K(2)[(UO(2))(3)(IO(3))(4)O(2)] is composed of [(UO(2))(3)(IO(3))(4)O(2)](2)(-) chains built from the edge-sharing UO(7) pentagonal bipyramids and UO(6) octahedra. Ba[(UO(2))(2)(IO(3))(2)O(2)](H(2)O) consists of one-dimensional [(UO(2))(2)(IO(3))(2)O(2)](2)(-) ribbons formed from the edge sharing of distorted UO(7) pentagonal bipyramids. In both compounds the iodate groups occur in both bridging and monodentate binding modes and further serve to terminate the edges of the uranium oxide chains. The K(+) or Ba(2+) cations separate the chains or ribbons in these compounds forming bonds with terminal oxygen atoms from the iodate ligands. Crystallographic data: K(2)[(UO(2))(3)(IO(3))(4)O(2)], triclinic, space group P_1, a = 7.0372(5) A, b = 7.7727(5) A, c = 8.9851(6) A, alpha = 93.386(1) degrees, beta = 105.668(1) degrees, gamma = 91.339(1) degrees, Z = 1; Ba[(UO(2))(2)(IO(3))(2)O(2)](H(2)O), monoclinic, space group P2(1)/c, a = 8.062(4) A, b = 6.940(3) A, c = 21.67(1), beta= 98.05(1) degrees, Z = 4.

  2. Ferroelectricity and antiferroelectricity of doped thin HfO2-based films.

    PubMed

    Park, Min Hyuk; Lee, Young Hwan; Kim, Han Joon; Kim, Yu Jin; Moon, Taehwan; Kim, Keum Do; Müller, Johannes; Kersch, Alfred; Schroeder, Uwe; Mikolajick, Thomas; Hwang, Cheol Seong

    2015-03-18

    The recent progress in ferroelectricity and antiferroelectricity in HfO2-based thin films is reported. Most ferroelectric thin film research focuses on perovskite structure materials, such as Pb(Zr,Ti)O3, BaTiO3, and SrBi2Ta2O9, which are considered to be feasible candidate materials for non-volatile semiconductor memory devices. However, these conventional ferroelectrics suffer from various problems including poor Si-compatibility, environmental issues related to Pb, large physical thickness, low resistance to hydrogen, and small bandgap. In 2011, ferroelectricity in Si-doped HfO2 thin films was first reported. Various dopants, such as Si, Zr, Al, Y, Gd, Sr, and La can induce ferro-electricity or antiferroelectricity in thin HfO2 films. They have large remanent polarization of up to 45 μC cm(-2), and their coercive field (≈1-2 MV cm(-1)) is larger than conventional ferroelectric films by approximately one order of magnitude. Furthermore, they can be extremely thin (<10 nm) and have a large bandgap (>5 eV). These differences are believed to overcome the barriers of conventional ferroelectrics in memory applications, including ferroelectric field-effect-transistors and three-dimensional capacitors. Moreover, the coupling of electric and thermal properties of the antiferroelectric thin films is expected to be useful for various applications, including energy harvesting/storage, solid-state-cooling, and infrared sensors. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Superparamagnetic Fe3O4 particles formed by oxidation of pyrite heated in an anoxic atmosphere

    USGS Publications Warehouse

    Thorpe, A.N.; Senftle, F.E.; Talley, R.; Hetherington, S.; Dulong, F.

    1990-01-01

    As a follow-up to previous gas analysis experiments in which pyrite was heated to 681 K in an anoxic (oxygen starved) atmosphere, the first oxidation product, FeSO4, was studied as a bulk material. No decomposition of FeSO4 to Fe3O4 was observed in the temperature range studied. The lack of decomposition of bulk FeSO4 to Fe3O4 suggests that FeS2 oxidizes directly to Fe3O4, or that FeSO4, FeS2 and O2 react together to form Fe3O4. Magnetic susceptibility and magnetization measurements, along with magnetic hysteresis curves, show that small particles of Fe3O4 form on the pyrite surface, rather than a continuous layer of bulk Fe3O4. A working model describing the oxidation steps is presented. ?? 1990.

  4. Structural, Electrical and Optical Properties of TiO2 Thin Film Deposited on the Nano Porous Silicon Template

    NASA Astrophysics Data System (ADS)

    Bahar, Mahmood; Dermani, Ensieh Khalili

    The porous silicon (PSi), which is produced by the electrochemical etching, has been used as a substrate for the growth of the titanium oxide (TiO2) thin films. By using the EBPVD method, TiO2 thin films have been deposited on the surface of the PSi substrate. TiO2/PSi layers were annealed at the temperature of 400∘C, 500∘C and 600∘C for different tests. The morphology and structures of layers were investigated by the scanning electron microscopy (SEM) and X-ray diffraction (XRD). The current-voltage characteristic curves of samples and the ideality factor of heterojunction were studied. The results showed that the electrical properties of the samples change with increase in the annealing temperature. The optical properties of the prepared samples were investigated by using UV-Vis and photoluminescence (PL) spectroscopy. Green light emission of the PSi combined with the blue light and violet-blue emission obtained from the TiO2/PSi PL spectra. The results showed that the optical band gap energy of the PSi has increased from 1.86eV to 2.93eV due to the deposition of TiO2 thin film.

  5. Catalysis of nickel ferrite for photocatalytic water oxidation using [Ru(bpy)3]2+ and S2O8(2-).

    PubMed

    Hong, Dachao; Yamada, Yusuke; Nagatomi, Takaharu; Takai, Yoshizo; Fukuzumi, Shunichi

    2012-12-05

    Single or mixed oxides of iron and nickel have been examined as catalysts in photocatalytic water oxidation using [Ru(bpy)(3)](2+) as a photosensitizer and S(2)O(8)(2-) as a sacrificial oxidant. The catalytic activity of nickel ferrite (NiFe(2)O(4)) is comparable to that of a catalyst containing Ir, Ru, or Co in terms of O(2) yield and O(2) evolution rate under ambient reaction conditions. NiFe(2)O(4) also possesses robustness and ferromagnetic properties, which are beneficial for easy recovery from the solution after reaction. Water oxidation catalysis achieved by a composite of earth-abundant elements will contribute to a new approach to the design of catalysts for artificial photosynthesis.

  6. Desulfurization from thiophene by SO(4)(2-)/ZrO(2) catalytic oxidation at room temperature and atmospheric pressure.

    PubMed

    Wang, Bo; Zhu, Jianpeng; Ma, Hongzhu

    2009-05-15

    Thiophene, due to its poison, together with its combustion products which causes air pollution and highly toxic characteristic itself, attracted more and more attention to remove from gasoline and some high concentration systems. As the purpose of achieving the novel method of de-thiophene assisted by SO(4)(2-)/ZrO(2) (SZ), three reactions about thiophene in different atmosphere at room temperature and atmospheric pressure were investigated. SO(4)(2-)/ZrO(2) catalyst were synthesized and characterized by X-ray photoelectron spectroscopy (XPS), Fourier transformation infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and scanning electron microscope (SEM). The products were detected by gas chromatography-mass spectrometry (GC-MS). XP spectra show that ozone-catalyst system (SZO) have two forms of sulfur element (S(6+) and S(2-)) on the catalyst surface, which distinguished from that of air-catalyst system (SZA) and blank-catalyst system (SZB) (S(6+)). And the results of GC-MS exhibited that some new compounds has been produced under this extremely mild condition. Especially, many kinds of sulfur compounds containing oxygen, that is easier to be extracted by oxidative desulfurization (ODS), have been detected in the SZA-1.5h and SZB-3h system. In addition, some long chain hydrocarbons have also been detected. While in SZO-0.5h system, only long chain hydrocarbons were found. The results show that total efficiency of desulfurization from thiophene with ozone near to 100% can be obtained with the SO(4)(2-)/ZrO(2) catalytic oxidation reaction.

  7. Remarkably high mobility ultra-thin-film metal-oxide transistor with strongly overlapped orbitals

    PubMed Central

    Wei Shih, Chen; Chin, Albert; Fu Lu, Chun; Fang Su, Wei

    2016-01-01

    High mobility channel thin-film-transistor (TFT) is crucial for both display and future generation integrated circuit. We report a new metal-oxide TFT that has an ultra-thin 4.5 nm SnO2 thickness for both active channel and source-drain regions, very high 147 cm2/Vs field-effect mobility, high ION/IOFF of 2.3 × 107, small 110 mV/dec sub-threshold slope, and a low VD of 2.5 V for low power operation. This mobility is already better than chemical-vapor-deposition grown multi-layers MoS2 TFT. From first principle quantum-mechanical calculation, the high mobility TFT is due to strongly overlapped orbitals. PMID:26744240

  8. Surface reactions of ethanol over UO 2(100) thin film

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    S. D. Senanayake; Mudiyanselage, K.; Burrell, A. K.

    2015-10-08

    The study of the reactions of oxygenates on well-defined oxide surfaces is important for the fundamental understanding of heterogeneous chemical pathways that are influenced by atomic geometry, electronic structure, and chemical composition. In this work, an ordered uranium oxide thin film surface terminated in the (100) orientation is prepared on a LaAlO 3 substrate and studied for its reactivity with a C-2 oxygenate, ethanol (CH 3CH 2OH). With the use of synchrotron X-ray photoelectron spectroscopy (XPS), we have probed the adsorption and desorption processes observed in the valence band, C 1s, O 1s, and U 4f to investigate the bondingmore » mode, surface composition, electronic structure, and probable chemical changes to the stoichiometric-UO 2(100) [smooth-UO 2(100)] and Ar +-sputtered UO 2(100) [rough-UO 2(100)] surfaces. Unlike UO 2(111) single crystal and UO 2 thin film, Ar-ion-sputtering of this UO 2(100) did not result in noticeable reduction of U cations. Upon ethanol adsorption (saturation occurred at 0.5 ML), only the ethoxy (CH 3CH 2O –) species is formed on smooth-UO 2(100) whereas initially formed ethoxy species are partially oxidized to surface acetate (CH3COO–) on the Ar +-sputtered UO 2(100) surface. Furthermore, all ethoxy and acetate species are removed from the surface between 600 and 700 K.« less

  9. CO oxidation and O2 removal on meteoric material in Venus' atmosphere

    NASA Astrophysics Data System (ADS)

    Frankland, Victoria L.; James, Alexander D.; Carrillo-Sánchez, Juan Diego; Nesvorný, David; Pokorný, Petr; Plane, John M. C.

    2017-11-01

    The heterogeneous oxidation of CO by O2 on olivine, Fe sulfate and Fe oxide particles was studied using a flow tube apparatus between 300 and 680 K. These particles were chosen as possible analogues of unablated cosmic dust and meteoric smoke in Venus' atmosphere. On olivine and Fe oxides, the rate of CO oxidation to CO2 only becomes significant above 450 K. For iron sulfates, CO2 production was not observed until these dust analogues had decomposed into iron oxides at ∼ 540 K. The CO oxidation rate increases significantly with a higher Fe content in the dust, implying that oxidation occurs through Fe active sites (no reaction was observed on Mg2SiO4). The oxidation kinetics can be explained by CO reacting with chemi-sorbed O2 through an Eley-Rideal mechanism, which is supported by electronic structure calculations. Uptake coefficients were measured from 450 to 680 K, yielding: log10(γ (CO on MgFeSiO4)) = (2.9 ± 0.1) × 10-3 T(K) - (8.2 ± 0.1); log10(γ (CO on Fe2SiO4)) = (2.3 ± 0.3) × 10-3 T(K) - (7.7 ± 0.2); log10(γ (CO on FeOOH/Fe2O3)) = (5.6 ± 0.8) × 10-3T(K) - (9.3 ± 0.4). A 1-D atmospheric model of Venus was then constructed to explore the role of heterogeneous oxidation. The cosmic dust input to Venus, mostly originating from Jupiter Family Comets, is around 32 tonnes per Earth day. A chemical ablation model was used to show that ∼34% of this incoming mass ablates, forming meteoric smoke particles which, together with unablated dust particles, provide a significant surface for the heterogeneous oxidation of CO to CO2 in Venus' troposphere. This process should cause almost complete removal of O2 below 40 km, but have a relatively small impact on the CO mixing ratio (since CO is in large excess over O2). Theoretical quantum calculations indicate that the gas-phase oxidation of CO by SO2 in the lower troposphere is not competitive with the heterogeneous oxidation of CO. Finally, the substantial number density of meteoric smoke particles predicted

  10. ZnO transparent conductive oxide for thin film silicon solar cells

    NASA Astrophysics Data System (ADS)

    Söderström, T.; Dominé, D.; Feltrin, A.; Despeisse, M.; Meillaud, F.; Bugnon, G.; Boccard, M.; Cuony, P.; Haug, F.-J.; Faÿ, S.; Nicolay, S.; Ballif, C.

    2010-03-01

    There is general agreement that the future production of electric energy has to be renewable and sustainable in the long term. Photovoltaic (PV) is booming with more than 7GW produced in 2008 and will therefore play an important role in the future electricity supply mix. Currently, crystalline silicon (c-Si) dominates the market with a share of about 90%. Reducing the cost per watt peak and energy pay back time of PV was the major concern of the last decade and remains the main challenge today. For that, thin film silicon solar cells has a strong potential because it allies the strength of c-Si (i.e. durability, abundancy, non toxicity) together with reduced material usage, lower temperature processes and monolithic interconnection. One of the technological key points is the transparent conductive oxide (TCO) used for front contact, barrier layer or intermediate reflector. In this paper, we report on the versatility of ZnO grown by low pressure chemical vapor deposition (ZnO LP-CVD) and its application in thin film silicon solar cells. In particular, we focus on the transparency, the morphology of the textured surface and its effects on the light in-coupling for micromorph tandem cells in both the substrate (n-i-p) and superstrate (p-i-n) configurations. The stabilized efficiencies achieved in Neuchâtel are 11.2% and 9.8% for p-i-n (without ARC) and n-i-p (plastic substrate), respectively.

  11. Effect of film thickness on NO2 gas sensing properties of sprayed orthorhombic nanocrystalline V2O5 thin films

    NASA Astrophysics Data System (ADS)

    Mane, A. A.; Moholkar, A. V.

    2017-09-01

    The nanocrystalline V2O5 thin films with different thicknesses have been grown onto the glass substrates using chemical spray pyrolysis (CSP) deposition method. The XRD study shows that the films exhibit an orthorhombic crystal structure. The narrow scan X-ray photoelectron spectrum of V-2p core level doublet gives the binding energy difference of 7.3 eV, indicating that the V5+ oxidation state of vanadium. The FE-SEM micrographs show the formation of nanorods-like morphology. The AFM micrographs show the high surface area to volume ratio of nanocrystalline V2O5 thin films. The optical study gives the band gap energy values of 2.41 eV, 2.44 eV, 2.47 eV and 2.38 eV for V2O5 thin films deposited with the thicknesses of 423 nm, 559 nm, 694 nm and 730 nm, respectively. The V2O5 film of thickness 559 nm shows the NO2 gas response of 41% for 100 ppm concentration at operating temperature of 200 °C with response and recovery times of 20 s and 150 s, respectively. Further, it shows the rapid response and reproducibility towards 10 ppm NO2 gas concentration at 200 °C. Finally, NO2 gas sensing mechanism based on chemisorption process is discussed.

  12. Electrical properties of radio-frequency sputtered HfO2 thin films for advanced CMOS technology

    NASA Astrophysics Data System (ADS)

    Sarkar, Pranab Kumar; Roy, Asim

    2015-08-01

    The Hafnium oxide (HfO2) high-k thin films have been deposited by radio frequency (rf) sputtering technique on p-type Si (100) substrate. The thickness, composition and phases of films in relation to annealing temperatures have been investigated by using cross sectional FE-SEM (Field Emission Scanning Electron Microscope) and grazing incidence x-ray diffraction (GI-XRD), respectively. GI-XRD analysis revealed that at annealing temperatures of 350°C, films phases change to crystalline from amorphous. The capacitance-voltage (C-V) and current-voltage (I-V) characteristics of the annealed HfO2 film have been studied employing Al/HfO2/p-Si metal-oxide-semiconductor (MOS) structures. The electrical properties such as dielectric constant, interface trap density and leakage current density have been also extracted from C-V and I-V Measurements. The value of dielectric constant, interface trap density and leakage current density of annealed HfO2 film is obtained as 23,7.57×1011eV-1 cm-2 and 2.7×10-5 Acm-2, respectively. In this work we also reported the influence of post deposition annealing onto the trapping properties of hafnium oxide and optimized conditions under which no charge trapping is observed into the dielectric stack.

  13. Suggestion for search of ethylene oxide (c-C2H4O) in a cosmic object

    NASA Astrophysics Data System (ADS)

    Sharma, M. K.; Sharma, M.; Chandra, S.

    2018-05-01

    Ethylene oxide (c-C2H4O) and its isomer acetaldehyde (CH3CHO) are important organic molecules because of their potential role in the formation of amino acids. The c-C2H4O molecule is a b-type asymmetric top molecule and owing to half-spin of each of the four hydrogen atoms, it has two distinct ortho (nuclear spin one) and para (nuclear spin zero and two) species. It has been detected in the Sgr B2N. Using the rotational and centrifugal distortion constants along with the electric dipole moment, we have calculated energies of 100 rotational levels of each of the ortho and para species of c-C2H4O molecule and the Einstein A-coefficients for radiative transitions between the levels. The values of Einstein A-coefficients along with the scaled values for the collisional rate coefficients are used for solving a set of statistical equilibrium equations coupled with the equations of radiative transfer. Brightness-temperatures of five rotational transitions of each of the ortho and para species of c-C2H4O molecule are investigated. Out of these ten transitions, three transitions are found to show the anomalous absorption and rest seven are found to show the emission feature. We have also investigated seven transitions observed unblended in the Sgr B2(N). We have found that the transitions 3_{3 0} - 3_{2 1} (23.134 GHz), 2_{2 0} - 2_{1 1} (15.603 GHz), 3_{3 1} - 3_{2 2} (39.680 GHz) and 1_{1 1} - 0_{0 0} (39.582 GHz) may play important role for the identification of ethylene oxide in a cosmic object.

  14. Degradation of sulfamethazine using Fe3O4-Mn3O4/reduced graphene oxide hybrid as Fenton-like catalyst.

    PubMed

    Wan, Zhong; Wang, Jianlong

    2017-02-15

    In this paper, Fe 3 O 4 -Mn 3 O 4 /reduced graphene oxide (RGO) hybrid was synthesized through polyol process and impregnation method and used as heterogeneous Fenton-like catalyst for degradation of sulfamethazine (SMT) in aqueous solution. The hybrid catalyst had higher catalytic efficiency compared with Fe 3 O 4 -Mn 3 O 4 and Mn 3 O 4 as catalyst for degradation of SMT . The effects of pH value, H 2 O 2 concentration, catalyst dosage, initial SMT concentration and temperature on SMT degradation were investigated. The removal efficiency of SMT was about 98% at following optimal conditions: pH=3, T=35°C, Fe 3 O 4 /Mn 3 O 4 -RGO composites=0.5g/L, H 2 O 2 =6mM. The inhibitor experiments indicated that the main active species was hydroxyl radicals (·OH) on catalyst surface. At last, the possible catalytic mechanism was proposed. Copyright © 2016 Elsevier B.V. All rights reserved.

  15. Ceramic oxide reactions with V2O5 and SO3

    NASA Technical Reports Server (NTRS)

    Jones, R. L.; Williams, C. E.

    1985-01-01

    Ceramic oxides are not inert in combustion environments, but can react with, inter alia, SO3, and Na2SO4 to yield low melting mixed sulfate eutectics, and with vanadium compounds to produce vanadates. Assuming ceramic degradation to become severe only when molten phases are generated in the surface salt (as found for metallic hot corrosion), the reactivity of ceramic oxides can be quantified by determining the SO3 partial pressure necessary for molten mixed sulfate formation with Na2SO3. Vanadium pentoxide is an acidic oxide that reacts with Na2O, SO3, and the different ceramic oxides in a series of Lux-Flood type of acid-base displacement reactions. To elucidate the various possible vanadium compound-ceramic oxide interactions, a study was made of the reactions of a matrix involving, on the one axis, ceramix oxides of increasing acidity, and on the other axis, vanadium compounds of increasing acidity. Resistance to vanadium compound reaction increased as the oxide acidity increased. Oxides more acidic than ZrO2 displaced V2O5. Examination of Y2O3- and CeO2-stabilized ZrO2 sintered ceramics which were degraded in 700 C NaVO3 has shown good agreement with the reactions predicted above, except that the CeO2-ZrO2 ceramic appears to be inexplicably degraded by NaVO3.

  16. NiCo2O4 surface coating Li[Ni0.03Mn1.97]O4 micro-/nano- spheres as cathode material for high-performance lithium ion battery

    NASA Astrophysics Data System (ADS)

    Ye, Pan; Dong, Hui; Xu, Yunlong; Zhao, Chongjun; Liu, Dong

    2018-01-01

    Here we report a novel transitional metal oxide (NiCo2O4) coated Li[Ni0.03Mn1.97]O4 micro-/nano- spheres as high-performance Li-ion battery cathode material. A thin layer of ∼10 nm NiCo2O4 was formed by simple wet-chemistry approach adjacent to the surface of Li[Ni0.03Mn1.97]O4 micro-/nano- spheres, leading to significantly enhanced battery electrochemical performance. The optimized sample(1 wt%) not only delivers excellent discharge capacity and cycling stability improvement at both room temperature and elevated temperatures, but also effectively prevents Mn dissolution while retaining its coating structure intact according to XRF and TEM results. The CV and EIS break-down analysis indicated a much faster electrochemical reaction kinetics, more reversible electrode process and greatly reduced charge transfer and Warburg resistance, clearly illustrating the dual role of NiCo2O4 coating to boost electron transport and Li+ diffusion, and alleviation of manganese dissolving. This approach may render as an efficient technique to realize high-performance lithium ion battery cathode material.

  17. Reduced graphene oxide wrapped Cu2O supported on C3N4: An efficient visible light responsive semiconductor photocatalyst

    NASA Astrophysics Data System (ADS)

    Ganesh Babu, S.; Vinoth, R.; Surya Narayana, P.; Bahnemann, Detlef; Neppolian, B.

    2015-10-01

    Herein, Cu2O spheres were prepared and encapsulated with reduced graphene oxide (rGO). The Cu2O-rGO-C3N4 composite covered the whole solar spectrum with significant absorption intensity. rGO wrapped Cu2O loading caused a red shift in the absorption with respect to considering the absorption of bare C3N4. The photoluminescence study confirms that rGO exploited as an electron transport layer at the interface of Cu2O and C3N4 heterojunction. Utmost, ˜2 fold synergistic effect was achieved with Cu2O-rGO-C3N4 for the photocatalytic reduction of 4-nitrophenol to 4-aminophenol in comparison with Cu2O-rGO and C3N4. The Cu2O-rGO-C3N4 photocatalyst was reused for four times without loss in its activity.

  18. Effects of (NH4)2S x treatment on the surface properties of SiO2 as a gate dielectric for pentacene thin-film transistor applications

    NASA Astrophysics Data System (ADS)

    Hung, Cheng-Chun; Lin, Yow-Jon

    2018-01-01

    The effect of (NH4)2S x treatment on the surface properties of SiO2 is studied. (NH4)2S x treatment leads to the formation of S-Si bonds on the SiO2 surface that serves to reduce the number of donor-like trap states, inducing the shift of the Fermi level toward the conduction band minimum. A finding in this case is the noticeably reduced value of the SiO2 capacitance as the sulfurated layer is formed at the SiO2 surface. The effect of SiO2 layers with (NH4)2S x treatment on the carrier transport behaviors for the pentacene/SiO2-based organic thin-film transistor (OTFT) is also studied. The pentacene/as-cleaned SiO2-based OTFT shows depletion-mode behavior, whereas the pentacene/(NH4)2S x -treated SiO2-based OTFT exhibits enhancement-mode behavior. Experimental identification confirms that the depletion-/enhancement-mode conversion is due to the dominance competition between donor-like trap states in SiO2 near the pentacene/SiO2 interface and acceptor-like trap states in the pentacene channel. A sulfurated layer between pentacene and SiO2 is expected to give significant contributions to carrier transport for pentacene/SiO2-based OTFTs.

  19. Diffusion reaction of oxygen in HfO2/SiO2/Si stacks.

    PubMed

    Ferrari, S; Fanciulli, M

    2006-08-03

    We study the oxidation mechanism of silicon in the presence of a thin HfO2 layer. We performed a set of annealing in 18O2 atmosphere on HfO2/SiO2/Si stacks observing the 18O distribution in the SiO2 layer with time-of-flight secondary ion mass spectrometry (ToF-SIMS). The 18O distribution in HfO2/SiO2/Si stacks upon 18O2 annealing suggests that what is responsible for SiO2 growth is the molecular O2, whereas no contribution is found of the atomic oxygen to the oxidation. By studying the dependence of the oxidation velocity from oxygen partial pressure and annealing temperature, we demonstrate that the rate-determining step of the oxidation is the oxygen exchange at the HfO2/SiO2 interface. When moisture is chemisorbed in HfO2 films, the oxidation of the underlying silicon substrate becomes extremely fast and its kinetics can be described as a wet silicon oxidation process. The silicon oxidation during O2 annealing of the atomic layer deposited HfO2/Si is fast in its early stage due to chemisorbed moisture and becomes slow after the first 10 s.

  20. Designing MgFe2O4 decorated on green mediated reduced graphene oxide sheets showing photocatalytic performance and luminescence property

    NASA Astrophysics Data System (ADS)

    Shetty, Krushitha; Lokesh, S. V.; Rangappa, Dinesh; Nagaswarupa, H. P.; Nagabhushana, H.; Anantharaju, K. S.; Prashantha, S. C.; Vidya, Y. S.; Sharma, S. C.

    2017-02-01

    Here, a green route has been reported to convert Graphene Oxide (GO) to reduced graphene oxide (RGO) using clove extract. A modest and eco-accommodating sol-gel strategy has been employed to prepare MgFe2O4 nanoparticles, MgFe2O4-RGO nanocomposite samples. The samples were analyzed by Powder X-ray diffraction (PXRD), Fourier Transform Infrared Spectroscopy (FTIR), UV-Visible Spectroscopy, Scanning Electron Microcopy (SEM), Transmission Electron Microscopy (TEM), Photoluminescence (PL) and Electrochemical Impedance Spectroscopy (EIS). PXRD result revealed that the prepared samples were cubic spinel in nature. SEM results uncovered flake like surface morphology of the prepared nanomaterial. Better PL emission signature was observed when excited at 329 nm. PL studies demonstrated that the present samples were potential for the fabrication of white component of white light emitting diodes (WLEDs). Further, MgFe2O4-RGO nanocomposite showed enhanced photocatalytic movement (PCM) and photostability under Sunlight in the decomposition of Malachite Green (MG) compared to MgFe2O4. This can be attributed to the interaction of MgFe2O4 surface with RGO sheets which results in PL quenching, demonstrates that the recombination of photo-induced electrons and holes in MgFe2O4-RGO nanocomposite is more effectively inhibited. A possible mechanism for the enhanced properties of MgFe2O4-RGO nanocomposite was discussed. Moreover, MgFe2O4-RGO photocatalyst also showed easy magnetic separation with high reusability. These results unveil that the synthesized sample can be used in display applications and also as a potential photocatalyst.

  1. Resonant photoemission spectroscopic studies of SnO2 thin films

    NASA Astrophysics Data System (ADS)

    Kumar, Sunil; Chauhan, R. S.; Panchal, Gyanendra; Singh, C. P.; Dar, Tanveer A.; Phase, D. M.; Choudhary, R. J.

    2017-09-01

    We report the structural and electronic properties of single phase, polycrystalline rutile tetragonal SnO2 thin film grown on Si (100) substrate by pulsed laser deposition technique. X-ray photoelectron and resonant photoemission spectroscopic (RPES) studies divulge that Sn is present in 4+ (˜91%) valence state with a very small involvement of 2+ (˜9%) valence state at the surface. Valence band spectrum of the film shows prominent contribution due to the Sn4+ valence state. RPES measurements were performed in the Sn 4d→5p photo absorption region. This study shows that O-2p, Sn-5s, and Sn-5p partial density of states are the main contributions to the valence band of this material. The resonance behavior of these three contributions has been analyzed. Constant initial state versus photon energy plots suggest that the low binding energy feature at ˜2.8 eV results from the hybridization of the O-2p and mixed valence states of Sn, while remaining features at higher binding energies are due to the hybridization between O-2p (bonding) orbitals and Sn4+ valence state.

  2. Photoelectrochemical Properties and Photostabilities of High Surface Area CuBi 2O 4 and Ag-Doped CuBi 2O 4 Photocathodes

    DOE PAGES

    Kang, Donghyeon; Hill, James C.; Park, Yiseul; ...

    2016-06-09

    Here, electrochemical synthesis methods were developed to produce CuBi 2O 4, a promising p-type oxide for use in solar water splitting, as high surface area electrodes with uniform coverage. These methods involved electrodepositing nanoporous Cu/Bi films with a Cu:Bi ratio of 1:2 from dimethyl sulfoxide or ethylene glycol solutions, and thermally oxidizing them to CuBi 2O 4 at 450°C in air. Ag-doped CuBi 2O 4 electrodes were also prepared by adding a trace amount of Ag+ in the plating medium and codepositing Ag with the Cu/Bi films. In the Ag-doped CuBi 2O 4, Ag+ ions substitutionally replaced Bi3+ ions andmore » increased the hole concentration in CuBi 2O 4. As a result, photocurrent enhancements for both O 2 reduction and water reduction were achieved. Furthermore, while undoped CuBi 2O 4 electrodes suffered from anodic photocorrosion during O 2 reduction due to poor hole transport, Ag-doped CuBiO 4 effectively suppressed anodic photocorrosion. The flat-band potentials of CuBi 2O 4 and Ag-doped CuBi 2O 4 electrodes prepared in this study were found to be more positive than 1.3 V vs RHE in a 0.1 M NaOH solution (pH 12.8), which make these photocathodes highly attractive for use in solar hydrogen production. The optimized CuBi 2O 4/Ag-doped CuBi 2O 4 photocathode showed a photocurrent onset for water reduction at 1.1 V vs RHE, achieving a photovoltage higher than 1 V for water reduction. The thermodynamic feasibility of photoexcited electrons in the conduction band of CuBi 2O 4 to reduce water was also confirmed by detection of H 2 during photocurrent generation. This study provides new understanding for constructing improved CuBi 2O 4 photocathodes by systematically investigating photocorrosion as well as photoelectrochemical properties of high-quality CuBi 2O 4 and Ag-doped CuBi 2O 4 photoelectrodes for photoreduction of both O 2 and water.« less

  3. Photoelectrochemical Properties and Photostabilities of High Surface Area CuBi 2O 4 and Ag-Doped CuBi 2O 4 Photocathodes

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kang, Donghyeon; Hill, James C.; Park, Yiseul

    Here, electrochemical synthesis methods were developed to produce CuBi 2O 4, a promising p-type oxide for use in solar water splitting, as high surface area electrodes with uniform coverage. These methods involved electrodepositing nanoporous Cu/Bi films with a Cu:Bi ratio of 1:2 from dimethyl sulfoxide or ethylene glycol solutions, and thermally oxidizing them to CuBi 2O 4 at 450°C in air. Ag-doped CuBi 2O 4 electrodes were also prepared by adding a trace amount of Ag+ in the plating medium and codepositing Ag with the Cu/Bi films. In the Ag-doped CuBi 2O 4, Ag+ ions substitutionally replaced Bi3+ ions andmore » increased the hole concentration in CuBi 2O 4. As a result, photocurrent enhancements for both O 2 reduction and water reduction were achieved. Furthermore, while undoped CuBi 2O 4 electrodes suffered from anodic photocorrosion during O 2 reduction due to poor hole transport, Ag-doped CuBiO 4 effectively suppressed anodic photocorrosion. The flat-band potentials of CuBi 2O 4 and Ag-doped CuBi 2O 4 electrodes prepared in this study were found to be more positive than 1.3 V vs RHE in a 0.1 M NaOH solution (pH 12.8), which make these photocathodes highly attractive for use in solar hydrogen production. The optimized CuBi 2O 4/Ag-doped CuBi 2O 4 photocathode showed a photocurrent onset for water reduction at 1.1 V vs RHE, achieving a photovoltage higher than 1 V for water reduction. The thermodynamic feasibility of photoexcited electrons in the conduction band of CuBi 2O 4 to reduce water was also confirmed by detection of H 2 during photocurrent generation. This study provides new understanding for constructing improved CuBi 2O 4 photocathodes by systematically investigating photocorrosion as well as photoelectrochemical properties of high-quality CuBi 2O 4 and Ag-doped CuBi 2O 4 photoelectrodes for photoreduction of both O 2 and water.« less

  4. Electrochemical and physical properties of electroplated CuO thin films.

    PubMed

    Dhanasekaran, V; Mahalingam, T

    2013-01-01

    Cupric oxide thin films have been prepared on ITO glass substrates from an aqueous electrolytic bath containing CuSO4 and tartaric acid. Growth mechanism has been analyzed using cyclic voltammetry. The role of pH on the structural, morphological, compositional, electrical and optical properties of CuO films is investigated. The structural studies revealed that the deposited films are polycrystalline in nature with a cubic structure. The preferential orientation of CuO thin films is found to be along (111) plane. X-ray line profile analysis has been carried out to determine the microstructural parameters of CuO thin films. The pyramid shaped grains are observed from SEM and AFM images. The optical band gap energy and electrical activation energy is found to be 1.45 and 0.37 eV, respectively. Also, the optical constants of CuO thin films such as refractive index (n), complex dielectric constant (epsilon) extinction coefficient (k) and optical conductivity (sigma) are evaluated.

  5. Efficient removal of herbicide 2,4-dichlorophenoxyacetic acid from water using Ag/reduced graphene oxide co-decorated TiO2 nanotube arrays.

    PubMed

    Tang, Yanhong; Luo, Shenglian; Teng, Yarong; Liu, Chengbin; Xu, Xiangli; Zhang, Xilin; Chen, Liang

    2012-11-30

    A new photocatalyst, Ag nanoparticles (NPs) and reduced graphene oxide (RGO) co-decorated TiO(2) nanotube arrays (NTs) (Ag/RGO-TiO(2) NTs), was designed and facilely produced by combining electrodeposition and photoreduction processes. The structures and properties of the photocatalysts were characterized. The ternary catalyst exhibited almost 100% photocatalytic removal efficiency of typical herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) from water under simulated solar light irradiation. The photodegradation rate toward 2,4-D over Ag/RGO-TiO(2) NTs is 11.3 times that over bare TiO(2) NTs. After 10 successive cycles with 1600 min of irradiation, Ag/RGO-TiO(2) NTs maintained as high 2,4-D removal efficiency as 97.3% with excellent stability and easy recovery, which justifies the photocatalytic system a promising application for herbicide removal from water. Copyright © 2012 Elsevier B.V. All rights reserved.

  6. Effects of post-deposition annealing on sputtered SiO2/4H-SiC metal-oxide-semiconductor

    NASA Astrophysics Data System (ADS)

    Lee, Suhyeong; Kim, Young Seok; Kang, Hong Jeon; Kim, Hyunwoo; Ha, Min-Woo; Kim, Hyeong Joon

    2018-01-01

    Reactive sputtering followed by N2, NH3, O2, and NO post-deposition annealing (PDA) of SiO2 on 4H-SiC was investigated in this study. The results of ellipsometry, an etching test, and X-ray photoemission spectroscopy showed that N2 and NH3 PDA nitrified the SiO2. Devices using N2 and NH3 PDA exhibited a high gate leakage current and low breakdown field due to oxygen vacancies and incomplete oxynitride. SiO2/4H-SiC MOS capacitors were also fabricated and their electrical characteristics measured. The average breakdown fields of the devices using N2, NH3, O2, and NO PDA were 0.12, 0.17, 4.71 and 2.63 MV/cm, respectively. The shifts in the flat-band voltage after O2 and NO PDA were 0.95 and -2.56 V, respectively, compared with the theoretical value. The extracted effective oxide charge was -4.11 × 1011 cm-2 for O2 PDA and 1.11 × 1012 cm-2 for NO PDA. NO PDA for 2 h at 1200 °C shifted the capacitance-voltage curve in the negative direction. The oxygen containing PDA showed better electrical properties than non-oxygen PDA. The sputtering method described can be applied to 4H-SiC MOS fabrication.

  7. Intensity analysis of XPS spectra to determine oxide uniformity - Application to SiO2/Si interfaces

    NASA Technical Reports Server (NTRS)

    Vasquez, R. P.; Grunthaner, F. J.

    1980-01-01

    A simple method of determining oxide uniformity is derived which requires no knowlege of film thickness, escape depth, or film composition. The method involves only the measurement of oxide and substrate intensities and is illustrated by analysis of XPS spectral data for thin SiO2 films grown both thermally and by low-temperature chemical vapor deposition on monocrystalline Si. A region 20-30 A thick is found near the SiO2/Si interface on thermally oxidized samples which has an inelastic mean free path 35% less than that found in the bulk oxide. This is interpreted as being due to lattice mismatch resulting in a strained region which is structurally, but not stoichiometrically, distinct from the bulk oxide.

  8. Fenton-like oxidation of 4-chlorophenol using H2O2 in situ generated by Zn-Fe-CNTs composite.

    PubMed

    Liu, Yong; Fan, Qing; Liu, Yanlan; Wang, Jianlong

    2018-05-15

    In this paper, a zinc-iron-carbon nanotubes (Zn-Fe-CNTs) composite was prepared, characterized and used to develop a Fenton-like system of Zn-Fe-CNTs/O 2 for the degradation of 4-chlorophenol (4-CP), in which H 2 O 2 was generated in situ from zinc-carbon galvanic cells and oxygen in aqueous solution was activated by iron attached on the surface of CNTs to produce ·OH radicals for the oxidation of 4-CP. The experimental results showed that the particles of Zn and Fe in Zn-Fe-CNTs composite were adhered to the surface of CNTs, which accelerated the electron transfer process. The BET area of Zn-Fe-CNTs composite was 32.9 m 2 /g. The contents of Zn and Fe (% w) in the composite were 44.7% and 4.2%, respectively. The removal efficiency of 4-CP and TOC in Zn-Fe-CNTs/O 2 system was 90.8% and 52.9%, respectively, with the initial pH of 2.0, O 2 flow rate of 800 mL/min, Zn-Fe-CNTs dosage of 1.0 g/L, 4-CP concentration of 50 mg/L and reaction time of 20 min. Based on the analysis of the degradation intermediate products with LC-MS and IC, a possible degradation pathway of 4-CP in Zn-Fe-CNTs/O 2 system was proposed. Copyright © 2018 Elsevier Ltd. All rights reserved.

  9. Enhanced visible light activity on direct contact Z-scheme g-C3N4-TiO2 photocatalyst

    NASA Astrophysics Data System (ADS)

    Li, Juan; Zhang, Min; Li, Qiuye; Yang, Jianjun

    2017-01-01

    Direct contact Z-scheme g-C3N4-TiO2 nanocomposites without an electron mediator are prepared via simple annealing the mixture of bulk g-C3N4 and nanotube titanic acid (NTA) in air at 600 °C for 2 h. In the process of annealing, the bulk g-C3N4 transformed to ultra-thin g-C3N4 nanosheets, and NTA converted to a novel anatase TiO2, then the two components formed a close interaction. The XPS result reveals that some amount of nitrogen is doped into this novel-TiO2, and g-C3N4 nanosheets exist in the composites. The results of XRD, TEM and TG indicate that the thickness of g-C3N4 nanosheets is very thin. The ESR spectrum shows the existence of Ti3+ and single-electron-trapped oxygen vacancy in the 30%g-C3N4-TiO2 composites. In photocatalytic activity test, the 30%g-C3N4-TiO2 nanocomposites showed an excellent photo-oxidation activity of propylene under visible light irradiation (λ≥ 420 nm), and the removal efficiency of propylene reached as high as 56.6%, and the activity kept nearly 82% after four consecutive recycles. Photoluminescence (PL) result using terephthalic acid (TA) as a probe molecule indicated that the g-C3N4-TiO2 nanocomposites displayed a Z-sheme photocatalytic reaction system and this should be the main reason for the high photocatalytic activity. A possible photocatalytic mechanism was proposed on the basis of PL result and transient photocurrent-time curves.

  10. Solid state reactions of CeO 2, PuO 2, (U,Ce)O 2 and (U,Pu)O 2 with K 2S 2O 8

    NASA Astrophysics Data System (ADS)

    Keskar, Meera; Kasar, U. M.; Mudher, K. D. Singh; Venugopal, V.

    2004-09-01

    Solid state reactions of CeO 2, PuO 2 and mixed oxides (U,Ce)O 2 and (U,Pu)O 2 containing different mol.% of Ce and Pu, were carried out with K 2S 2O 8 at different temperatures to identify the formation of various products and to investigate their dissolution behaviour. X-ray, chemical and thermal analysis methods were used to characterise the products formed at various temperatures. The products obtained by heating two moles of K 2S 2O 8 with one mole each of CeO 2, PuO 2, (U,Ce)O 2 and (U,Pu)O 2 at 400 °C were identified as K 4Ce(SO 4) 4, K 4Pu(SO 4) 4, K 4(U,Ce)(SO 4) 4 and K 4(U,Pu)(SO 4) 4, respectively. K 4Ce(SO 4) 4 further decomposed to form K 4Ce(SO 4) 3.5 at 600 °C and mixture of K 2SO 4 and CeO 2 at 950 °C. Thus the products formed during the reaction of 2K 2S 2O 8 + CeO 2 show that cerium undergoes changes in oxidation state from +4 to +3 and again to +4. XRD data of K 4Ce(SO 4) 4 and K 4Ce(SO 4) 3.5 were indexed on triclinic and monoclinic system, respectively. PuO 2 + 2K 2S 2O 8 reacts at 400 °C to form K 4Pu(SO 4) 4 which was stable upto 750 °C and further decomposes to form K 2SO 4 + PuO 2 at 1000 °C. The products formed at 400 °C during the reactions of the oxides and mixed oxides were found to be readily soluble in 1-2 M HNO 3.

  11. On the thermal stability of physical vapor deposited oxide-hardened nanocrystalline gold thin films

    DOE PAGES

    Argibay, Nicolas; Mogonye, J. E.; Michael, Joseph R.; ...

    2015-04-08

    We describe a correlation between electrical resistivity and grain size for PVD synthesized polycrystalline oxide-hardened metal-matrix thin films in oxide-dilute (<5 vol. % oxide phase) compositions. The correlation is based on the Mayadas-Shatzkes (M-S) electron scattering model, predictive of grain size evolution as a function of composition in the oxide-dilute regime for 2 μm thick Au-ZnO films. We describe a technique to investigate grain boundary (GB) mobility and the thermal stability of GBs based on in situelectrical resistivity measurements during annealing experiments, interpreted using a combination of the M-S model and the Michels et al. model describing solute drag stabilizedmore » grain growth kinetics. Using this technique, activation energy and pre-exponential Arrhenius parameter values of E a = 21.6 kJ/mol and A o = 2.3 × 10 -17 m 2/s for Au-1 vol. % ZnO and E a =12.7 kJ/mol and A o = 3.1 × 10 -18 m 2/s for Au-2 vol.% ZnO were determined. In the oxide-dilute regime, the grain size reduction of the Au matrix yielded a maximum hardness of 2.6 GPa for 5 vol. % ZnO. A combined model including percolation behavior and grain refinement is presented that accurately describes the composition dependent change in electrical resistivity throughout the entire composition range for Au-ZnO thin films. As a result, the proposed correlations are supported by microstructural characterization using transmission electron microscopy and electron diffraction mapping for grain size determination.« less

  12. Atomically Defined Templates for Epitaxial Growth of Complex Oxide Thin Films

    PubMed Central

    Dral, A. Petra; Dubbink, David; Nijland, Maarten; ten Elshof, Johan E.; Rijnders, Guus; Koster, Gertjan

    2014-01-01

    Atomically defined substrate surfaces are prerequisite for the epitaxial growth of complex oxide thin films. In this protocol, two approaches to obtain such surfaces are described. The first approach is the preparation of single terminated perovskite SrTiO3 (001) and DyScO3 (110) substrates. Wet etching was used to selectively remove one of the two possible surface terminations, while an annealing step was used to increase the smoothness of the surface. The resulting single terminated surfaces allow for the heteroepitaxial growth of perovskite oxide thin films with high crystalline quality and well-defined interfaces between substrate and film. In the second approach, seed layers for epitaxial film growth on arbitrary substrates were created by Langmuir-Blodgett (LB) deposition of nanosheets. As model system Ca2Nb3O10- nanosheets were used, prepared by delamination of their layered parent compound HCa2Nb3O10. A key advantage of creating seed layers with nanosheets is that relatively expensive and size-limited single crystalline substrates can be replaced by virtually any substrate material. PMID:25549000

  13. Photoelectrochemical enhancement of ZnO/BiVO4/ZnFe2O4/rare earth oxide hetero-nanostructures

    NASA Astrophysics Data System (ADS)

    She, Xuefeng; Zhang, Zhuo; Baek, Minki; Yong, Kijung

    2018-01-01

    Over the decades, researchers have made great efforts to turn the world into a cleaner place through efficient recycling of industrial waste and developing of green energy. Here we demonstrate a prototype heterostructure photoelectrochemical (PEC) cell fabricated using recycled industrial waste. ZnFe2O4 (ZFO) nanorod (NR) clusters were synthesized on the BiVO4@ZnO hetero-nanostructures using recycled rare earth oxide (REO) slags as Fe source. The NR-based PEC cell exhibited a significantly enhanced photon to hydrogen conversion efficiency over the entire UV and visible spectrum. Further study demonstrates that the photo-carrier separation and migration processes can be facilitated by the cascade band alignment of the heterostructure and the clustered nanostructure network. In addition, the life-time of the photo-carriers can be enhanced by the REO passivation layer, leading to a further increased PEC performance. Our results present a novel approach for high efficiency PEC cells, and offer great promises to the efficient recycling of industrial waste for clean renewable energy applications.

  14. Low-Temperature UV-Assisted Fabrication of Metal Oxide Thin Film Transistor

    NASA Astrophysics Data System (ADS)

    Zhu, Shuanglin

    Solution processed metal oxide semiconductors have attracted intensive attention in the last several decades and have emerged as a promising candidate for the application of thin film transistor (TFT) due to their nature of transparency, flexibility, high mobility, simple processing technique and potential low manufacturing cost. However, metal oxide thin film fabricated by solution process usually requires a high temperature (over 300 °C), which is above the glass transition temperature of some conventional polymer substrates. In order to fabricate the flexible electronic device on polymer substrates, it is necessary to find a facile approach to lower the fabrication temperature and minimize defects in metal oxide thin film. In this thesis, the electrical properties dependency on temperature is discussed and an UV-assisted annealing method incorporating Deep ultraviolet (DUV)-decomposable additives is demonstrated, which can effectively improve electrical properties solution processed metal oxide semiconductors processed at temperature as low as 220 °C. By studying a widely used indium oxide (In2O3) TFT as a model system, it is worth noted that compared with the sample without UV treatment, the linear mobility and saturation mobility of UV-annealing sample are improved by 56% and 40% respectively. Meanwhile, the subthreshold swing is decreased by 32%, indicating UV-treated device could turn on and off more efficiently. In addition to pure In2O3 film, the similar phenomena have also been observed in indium oxide based Indium-Gallium-Zinc Oxide (IGZO) system. These finding presented in this thesis suggest that the UV assisted annealing process open a new route to fabricate high performance metal oxide semiconductors under low temperatures.

  15. Electrochemical performance of La2O3/Li2O/TiO2 nano-particle coated cathode material LiFePO4.

    PubMed

    Wang, Hong; Yang, Chi; Liu, Shu-Xin

    2014-09-01

    Cathode material, LiFePO4 was modified by coating with a thin layer of La2O3/Li2O/TiO2 nano-particles for improving its performance for lithium ion batteries. The morphology and structure of the modified cathode material were characterized by powder X-ray diffraction, scanning electron microcopy and AES. The performance of the battery with the modified cathode material, including cycling stability, C-rate discharge was examined. The results show that the battery composed of the coated cathode materials can discharge at a large current density and show stable cycling performance in the range from 2.5 to 4.0 V. The rate of Li ion diffusion increases in the battery with the La2O3/Li2O/TiO2-coated LiFePO4 as a cathode and the coating layer may acts as a faster ion conductor (La(2/3-x)Li(3x)TiO3).

  16. Effects of TiO2 and Co3O4 Nanoparticles on Circulating Angiogenic Cells

    PubMed Central

    Spigoni, Valentina; Cito, Monia; Alinovi, Rossella; Pinelli, Silvana; Passeri, Giovanni; Zavaroni, Ivana; Goldoni, Matteo; Campanini, Marco; Aliatis, Irene; Mutti, Antonio

    2015-01-01

    Background and Aim Sparse evidence suggests a possible link between exposure to airborne nanoparticles (NPs) and cardiovascular (CV) risk, perhaps through mechanisms involving oxidative stress and inflammation. We assessed the effects of TiO2 and Co3O4 NPs in human circulating angiogenic cells (CACs), which take part in vascular endothelium repair/replacement. Methods CACs were isolated from healthy donors’ buffy coats after culturing lymphomonocytes on fibronectin-coated dishes in endothelial medium for 7 days. CACs were pre-incubated with increasing concentration of TiO2 and Co3O4 (from 1 to 100 μg/ml) to test the effects of NP – characterized by Transmission Electron Microscopy – on CAC viability, apoptosis (caspase 3/7 activation), function (fibronectin adhesion assay), oxidative stress and inflammatory cytokine gene expression. Results Neither oxidative stress nor cell death were associated with exposure to TiO2 NP (except at the highest concentration tested), which, however, induced a higher pro-inflammatory effect compared to Co3O4 NPs (p<0.01). Exposure to Co3O4 NPs significantly reduced cell viability (p<0.01) and increased caspase activity (p<0.01), lipid peroxidation end-products (p<0.05) and pro-inflammatory cytokine gene expression (p<0.05 or lower). Notably, CAC functional activity was impaired after exposure to both TiO2 (p<0.05 or lower) and Co3O4 (p<0.01) NPs. Conclusions In vitro exposure to TiO2 and Co3O4 NPs exerts detrimental effects on CAC viability and function, possibly mediated by accelerated apoptosis, increased oxidant stress (Co3O4 NPs only) and enhancement of inflammatory pathways (both TiO2 and Co3O4 NPs). Such adverse effects may be relevant for a potential role of exposure to TiO2 and Co3O4 NPs in enhancing CV risk in humans. PMID:25803285

  17. Electrical characteristics of SiO2/ZrO2 hybrid tunnel barrier for charge trap flash memory

    NASA Astrophysics Data System (ADS)

    Choi, Jaeho; Bae, Juhyun; Ahn, Jaeyoung; Hwang, Kihyun; Chung, Ilsub

    2017-08-01

    In this paper, we investigate the electrical characteristics of SiO2/ZrO2 hybrid tunnel oxide in metal-Al2O3-SiO2-Si3N4-SiO2-silicon (MAONOS) structure in an effort to improve program and erase speed as well as retention characteristics. Inserting ZrO2 into the conventional MAONOS structure increased the programmed V th variation to 6.8 V, and increased the erased V th variation to -3.7 V at 17 MV/cm. The results can be understood in terms of reducing the Fowler-Nordheim (F/N) tunneling barrier due to high-k ZrO2 in the tunneling oxide. In addition, Zr diffusion in SiO2 caused the formation of Zr x Si1- x O2 at the interface region, which reduced the energy band gap of SiO2. The retention property of the hybrid tunnel oxide varied depending on the thickness of SiO2. For thin SiO2 less than 30 Å, the retention properties of the tunneling oxides were poor compared with those of the SiO2 only tunneling oxides. However, the hybrid tunneling oxides with SiO2 thickness thicker than 40 Å yielded improved retention behavior compared with those of the SiO2-only tunneling oxides. The detailed analysis in charge density of ZrO2 was carried out by ISPP test. The obtained charge density was quite small compared to that of the total charge density, which indicates that the inserted ZrO2 layer serves as a tunneling material rather than charge storage dielectric.

  18. Polymer thin film as coating layer to prevent corrosion of metal/metal oxide film

    NASA Astrophysics Data System (ADS)

    Sarkar, Suman; Kundu, Sarathi

    2018-04-01

    Thin film of polymer is used as coating layer and the corrosion of metal/metal oxide layer is studied with the variation of the thickness of the coating layer. The thin layer of polystyrene is fabricated using spin coating method on copper oxide (CuO) film which is deposited on glass substrate using DC magnetron sputtering technique. Thickness of the polystyrene and the CuO layers are determined using X-ray reflectivity (XRR) technique. CuO thin films coated with the polystyrene layer are exposed to acetic acid (2.5 v/v% aqueous CH3COOH solution) environments and are subsequently analyzed using UV-Vis spectroscopy and atomic force microscopy (AFM). Surface morphology of the film before and after interaction with the acidic environment is determined using AFM. Results obtained from the XRR and UV-Vis spectroscopy confirm that the thin film of polystyrene acts as an anticorrosion coating layer and the strength of the coating depends upon the polymer layer thickness at a constant acid concentration.

  19. Free-Standing β-Ga2O3 Thin Diaphragms

    NASA Astrophysics Data System (ADS)

    Zheng, Xu-Qian; Lee, Jaesung; Rafique, Subrina; Han, Lu; Zorman, Christian A.; Zhao, Hongping; Feng, Philip X.-L.

    2018-02-01

    Free-standing, very thin, single-crystal β-gallium oxide (β-Ga2O3) diaphragms have been constructed and their dynamical mechanical properties characterized by noncontact, noninvasive optical measurements harnessing the multimode nanomechanical resonances of these suspended nanostructures. We synthesized single-crystal β-Ga2O3 using low-pressure chemical vapor deposition (LPCVD) on a 3C-SiC epilayer grown on Si substrate at temperature of 950°C for 1.5 h. The synthesized single-crystal nanoflakes had widths of ˜ 2 μm to 30 μm and thicknesses of ˜ 20 nm to 140 nm, from which we fabricated free-standing circular drumhead β-Ga2O3 diaphragms with thicknesses of ˜ 23 nm to 73 nm and diameters of ˜ 3.2 μm and ˜ 5.2 μm using a dry stamp-transfer technique. Based on measurements of multiple flexural-mode mechanical resonances using ultrasensitive laser interferometric detection and performing thermal annealing at 250°C for 1.5 h, we quantified the effects of annealing and adsorption of atmospheric gas molecules on the resonant characteristics of the diaphragms. Furthermore, we studied the effects of structural nonidealities on these free-standing β-Ga2O3 nanoscale diaphragms. We present extensive characterization of the mechanical and optical properties of free-standing β-Ga2O3 diaphragms, paving the way for realization of resonant transducers using such nanomechanical structures for use in applications including gas sensing and ultraviolet radiation detection.

  20. Synthesis and microstructural TEM investigation of CaCu 3Ru 4O 12 ceramic and thin film

    NASA Astrophysics Data System (ADS)

    Brizé, Virginie; Autret-Lambert, Cécile; Wolfman, Jérôme; Gervais, Monique; Gervais, François

    2011-10-01

    CaCu 3Ru 4O 12 (CCRO) is a conductive oxide having the same structure as CaCu 3Ti 4O 12 (CCTO) and close lattice parameters. The later compound is strongly considered for high density parallel plates capacitors application due to its so-called colossal dielectric constant. The need for an electrode inducing CCTO epitaxial growth with a clean and sharp interface is therefore necessary, and CCRO is a good potential candidate. In this paper, the synthesis of monophasic CCRO ceramic is reported, as well as pulsed laser deposition of CCRO thin film onto (001) NdCaAlO 4 substrate. Structural and physical properties of bulk CCRO were studied by transmission electron microscopy and electron spin resonance. CCRO films and ceramic exhibited a metallic behavior down to low temperature. CCRO films were (001) oriented and promoted a CCTO film growth with the same orientation.

  1. Fabrication of novel ternary Au/CeO2@g-C3N4 nanocomposite: kinetics and mechanism investigation of 4-nitrophenol reduction, and benzyl alcohol oxidation

    NASA Astrophysics Data System (ADS)

    Kohantorabi, Mona; Gholami, Mohammad Reza

    2018-06-01

    Au nanoparticles supported on cerium oxide/graphitic carbon nitride (CeO2@g-C3N4) was synthesized and used as heterogeneous catalyst in redox reaction. The catalyst was characterized by different techniques such as FT-IR, XRD, FE-SEM, EDS, TEM, BET, TGA, and ICP. The as-prepared ternary nanocomposite was used as an effective catalyst for the reduction of toxic 4-nitrophenol to useful 4-aminophenol by NaBH4. The rate constant value of reduction reaction reached up to 0.106 s-1 by Au/CeO2@g-C3N4, which was 3.8, and 8.8 times higher than that of Au@CeO2 (0.028 s-1), and Au@g-C3N4 (0.012 s-1) nanocomposites, respectively. The superior catalytic performance of as-prepared catalyst in 4-NP reduction can be attributed to synergistic effect between Au nanoparticles and CeO2@g-C3N4 support, and efficient electron transfer. The reduction reaction was carried out at different temperatures, and the energy of activation ({Ea}), and thermodynamic parameters including, activation of entropy (Δ S^ ≠), enthalpy (Δ H^ ≠), and Gibbs free energy (Δ G^ ≠) were determined. Additionally, the mechanism of reaction was studied in details, and equilibrium constants of 4-NP ( K 4-NP), and {BH}4^{ - } ({K_{{BH}4^{{ - }} }}) were calculated using Langmuir-Hinshelwood model. Furthermore, this nanocomposite exhibited excellent catalytic activity in oxidation of benzyl alcohol by molecular oxygen as a green oxidant. This study revealed that the ternary Au/CeO2@g-C3N4 nanocomposite is an attractive candidate for catalytic applications.

  2. Interfacial stability of ultrathin films of magnetite Fe3O4 (111) on Al2O3(001) grown by ozone-assisted molecular-beam epitaxy

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Hong, Hawoong; Kim, Jongjin; Fang, Xinyue

    Thin films of iron oxides including magnetite (Fe3O4) and hematite (α-Fe2O3) have many important applications. Both forms of oxide can occur naturally during film growth by iron deposition under various oxidation environment; an important issue is to understand and control the process resulting in a single-phase film. We have performed in-situ real-time studies using x-ray diffraction of such film growth on sapphire (001) under pure ozone by monitoring the (00L) rod. Stable magnetite growth can be maintained at growth temperatures below 600° C up to a certain critical film thickness, beyond which the growth becomes hematite. The results demonstrate themore » importance of interfacial interaction in stabilizing the magnetite phase.« less

  3. Graphene oxide-MnO2 nanocomposite for supercapacitor application

    NASA Astrophysics Data System (ADS)

    Muhammed Shafi, P.; Vishal, Jose K.; Chandra Bose, A.

    2016-09-01

    Increased depletion of fossil fuels along with global warming and climate change made the society to think about alternate green and sustainable energy sources and better energy storage devices. Extensive research has been performed on the development of solar cells, fuel cells, Lithium- ion battery and supercapacitors to combat the green house effect and its consequences, and to meet the increased energy crisis. Supercapacitors, also known as electrochemical capacitors are gained a great attention because of their pulse power supply, long cycle life (>100,000), simple principle and high dynamic of charge propagation. Its greater power density than lithium- ion battery and much larger energy density than conventional capacitors brought super capacitors to a promising energy storage device to meet the increased energy demands. Here we demonstrate supercapacitor electrode materials with graphene oxide (electric double layer capacitor) and α-MnO2 nanomaterial (pseudo-capacitor), as well as composite of these materials, which means that the bulk of the material undergoes a fast redox reaction to provide the capacitive response and they exhibit superior specific energies in addition to the carbon-based supercapacitors (double-layer capacitors). A simple soft chemical route is utilized to synthesize graphene oxide, α-MnO2 and graphene oxide-MnO2 composite. The phase and the structure of the synthesized materials are studied using X-ray diffractometry (XRD). The functional group and the presence of impurities are understood from Fourier transform infrared (FTIR) spectra. The capacitive properties of the graphene oxide, graphene oxide - MnO2 nanocomposite and α-MnO2 are tested with the help of cyclic voltammetry (CV) and galvanostatic charge - discharge techniques using 1 M Na2SO4 in aqueous solution as electrolyte. It was found that graphene oxide - MnO2 nanocomposite shows better electrochemical behaviour compared to individual graphene oxide and α-MnO2 nanomaterial.

  4. Optical, mechanical and structural properties of PMMA/SiO2 nanocomposite thin films

    NASA Astrophysics Data System (ADS)

    Soni, Gyanesh; Srivastava, Subodh; Soni, Purushottam; Kalotra, Pankaj; Vijay, Y. K.

    2018-01-01

    We have fabricated PMMA/SiO2 nanocomposite flexible thin films of 60 μm thicknesses by using solution casting method in the presence of transverse electric field. In this paper, we have investigated the effect of SiO2 nanoparticle (NP) loading on optical and mechanical properties of the composite thin film. The SEM images show that nanocomposite thin films have a smoother and uniform morphology. The transmittance peak near 1103 cm-1 in FT-IR spectrum confirms the presence of SiO2 NPs in the composite thin film. It is observed that optical bandgap decreases with an increase in the SiO2 NP concentration. Dynamic mechanical analysis shows that presence of SiO2 NP enhances the mechanical strength of the composite thin film.

  5. LiCoO2 and SnO2 Thin Film Electrodes for Lithium-Ion Battery Applications

    NASA Technical Reports Server (NTRS)

    Maranchi, Jeffrey P.; Hepp, Aloysius F.; Kumta, Prashant N.

    2004-01-01

    There is an increasing need for small dimension, ultra-lightweight, portable power supplies due to the miniaturization of consumer electronic devices. Rechargeable thin film lithium-ion batteries have the potential to fulfill the growing demands for micro-energy storage devices. However, rechargeable battery technology and fabrication processes have not kept paced with the advances made in device technology. Economical fabrication methods lending excellent microstructural and compositional control in the thin film battery electrodes have yet to be fully developed. In this study, spin coating has been used to demonstrate the flexibility of the approach to produce both anode (SnO2) and cathode (LiCoO2) thin films. Results on the microstructure crystal structure and electrochemical properties of the thin film electrodes are described and discussed.

  6. Dye-sensitized electron transfer from TiO2 to oxidized triphenylamines that follows first-order kinetics

    PubMed Central

    DiMarco, Brian N.; Troian-Gautier, Ludovic; Sampaio, Renato N.

    2017-01-01

    Two sensitizers, [Ru(bpy)2(dcb)]2+ (RuC) and [Ru(bpy)2(dpb)]2+ (RuP), where bpy is 2,2′-bipyridine, dcb is 4,4′-dicarboxylic acid-2,2′-bipyridine and dpb is 4,4′-diphosphonic acid-2,2′-bipyridine, were anchored to mesoporous TiO2 thin films and utilized to sensitize the reaction of TiO2 electrons with oxidized triphenylamines, TiO2(e–) + TPA+ → TiO2 + TPA, to visible light in CH3CN electrolytes. A family of four symmetrically substituted triphenylamines (TPAs) with formal Eo(TPA+/0) reduction potentials that spanned a 0.5 eV range was investigated. Surprisingly, the reaction followed first-order kinetics for two TPAs that provided the largest thermodynamic driving force. Such first-order reactivity indicates a strong Coulombic interaction between TPA+ and TiO2 that enables the injected electron to tunnel back in one concerted step. The kinetics for the other TPA derivatives were non-exponential and were modelled with the Kohlrausch–William–Watts (KWW) function. A Perrin-like reaction sphere model is proposed to rationalize the kinetic data. The activation energies were the same for all of the TPAs, within experimental error. The average rate constants were found to increase with the thermodynamic driving force, consistent with electron transfer in the Marcus normal region. PMID:29629161

  7. Crystallographic and magnetic properties of sol-gel synthesized T xCo 1-xFe 2O 4 (T=Mn and Cr) thin films

    NASA Astrophysics Data System (ADS)

    Kim, Kwang Joo; Kyung Kim, Hee; Ran Park, Young; Choi, Seung-li; Eun Kim, Sung; Jung Lee, Hee; Yun Park, Jae; Jin Kim, Sam

    Effects of Mn and Cr substitution for Co on crystallographic and magnetic properties of inverse-spinel CoFe 2O 4 thin films were investigated. The crystal structure of the samples remain cubic for x<1 with the lattice constant ( a0) increasing with x for Mn doping and remaining constant for Cr doping. Tetrahedral Fe 2+ ions were detected in Cr xCo 1-xFe 2O 4 by Mössbauer spectroscopy while no such ions existed in Mn xCo 1-xFe 2O 4. The appearance of the tetrahedral Fe 2+ ions can be explained in terms of the Cr 3+ substitution for the octahedral Co 2+ sites with the resultant charge imbalance being compensated by a reduction of the tetrahedral Fe 3+ into Fe 2+. The observed variation in a0 and magnetic properties can be partly explained in terms of Mn 2+ and Cr 3+ substitution of octahedral sites in Mn xCo 1-xFe 2O 4 and Cr xCo 1-xFe 2O 4, respectively.

  8. Formation of homologous In{sub 2}O{sub 3}(ZnO){sub m} thin films and its thermoelectric properties

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Jia, Junjun; Nakamura, Shin-ichi; Shigesato, Yuzo, E-mail: yuzo@chem.aoyama.ac.jp

    Homologous In{sub 2}O{sub 3}(ZnO){sub 5} thin films were produced on a synthetic quartz glass substrate by thermal annealing of magnetron sputtered In{sub 2}O{sub 3}-ZnO compound films. When the annealing temperature was increased to 700 °C, the sputtered In{sub 2}O{sub 3}-ZnO film with In{sub 2}O{sub 3} microcrystalline changed to a c-oriented homologous In{sub 2}O{sub 3}(ZnO){sub 5} structure, for which the crystallization is suggested to begin from the surface and proceed along with the film thickness. The annealing temperature of 700 °C to form the In{sub 2}O{sub 3}(ZnO){sub 5} structure was substantially lower than temperatures of conventional solid state synthesis from In{sub 2}O{sub 3}more » and ZnO powders, which is attributed to the rapid diffusional transport of In and Zn due to the mixing of In{sub 2}O{sub 3} and ZnO in the atomic level for sputtered In{sub 2}O{sub 3}-ZnO compound films. The homologous structure collapsed at temperatures above 900 °C, which is attributed to (1) zinc vaporization from the surface and (2) a gradual increase of zinc silicate phase at the interface. This c-oriented layer structure of homologous In{sub 2}O{sub 3}(ZnO){sub 5} thin films along the film thickness allowed the thin film to reach a power factor of 1.3 × 10{sup −4} W/m K{sup 2} at 670 °C, which is comparable with the reported maximum value for the textured In{sub 2}O{sub 3}(ZnO){sub 5} powder (about 1.6 × 10{sup −4} W/m K{sup 2} at 650 °C).« less

  9. Crystal Structures and Thermal Properties of Two Transition-Metal Compounds {[Ni(DNI)2(H2O)3][Ni(DNI)2 (H2O)4]}·6H2O and Pb(DNI)2(H2O)4 (DNI = 2,4-Dinitroimidazolate)

    PubMed Central

    Zhang, Guo-Fang; Cai, Mei-Yu; Jing, Ping; He, Chong; Li, Ping; Zhao, Feng-Qi; Li, Ji-Zhen; Fan, Xue-Zhong; Ng, Seik Weng

    2010-01-01

    Two transition-metal compounds derived from 2,4-dinitroimidazole, {[Ni(DNI)2(H2O)3][Ni(DNI)2 (H2O)4]}·6H2O, 1, and Pb(DNI)2(H2O)4, 2, were characterized by elemental analysis, FT-IR, TG-DSC and X-ray single-crystal diffraction analysis. Crystal data for 1: monoclinic, space group C2/c, a = 26.826(3), b = 7.7199(10), c = 18.579(2) Å, β = 111.241(2)° and Z = 4; 2: monoclinic, space group C2/c, a = 6.5347(6), b = 17.1727(17), c = 14.1011(14) Å, β = 97.7248(10) and Z = 4. Compound 1 contains two isolated nickel centers in its structure, one being six-coordinate and another five-coordinate. The structure of 2 contains a lead (II) center surrounded by two chelating DNI ligands and four water molecules in distorted square-antiprism geometry. The abundant hydrogen bonds in two compounds link the molecules into three-dimensional network and stabilize the molecules. The TG-DSC analysis reveals that the first step is the loss of water molecules and the final residue is the corresponding metal oxides and carbon. PMID:20526419

  10. Pulsed laser deposited MnCo{sub 2}O{sub 4} protective layer on SS430 for solid oxide fuel cell application

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Gaur, Anshu, E-mail: gauranshu20@gmail.com, E-mail: ahamed.vza@gmail.com; Mohiddon, Md. Ahamad, E-mail: gauranshu20@gmail.com, E-mail: ahamed.vza@gmail.com; Prasad, Muvva D.

    2016-05-23

    The growth and oxidation study of pulsed laser deposited MnCo{sub 2}O{sub 4} protective layer on SS430 substrate for solid oxide fuel cell application is demonstrated. MnCo{sub 2}O{sub 4} has been achieved in three different ways including, deposition at higher substrate temperature (700°C), and deposition at room temperature on pre-oxidized and untreated SS430 substrate followed by annealing at 700°C for 2 hrs. X-ray diffraction and Raman spectroscopy has been applied to demonstrate the kind of phases developed in each case. These three samples were subjected to heat treatment at 750°C for 5 hr. The extent of undesired Fe{sub 2}O{sub 3} phasemore » formation in the post deposition heat treated samples is discussed based on Raman spectroscopic results.« less

  11. Water Oxidation Catalysis by Co(II) Impurities in Co(III) 4O 4 Cubanes

    DOE PAGES

    Ullman, Andrew M.; Liu, Yi; Huynh, Michael; ...

    2014-11-18

    Here, the observed water oxidation activity of the compound class Co 4O 4(OAc) 4(Py–X) 4 emanates from a Co(II) impurity. This impurity is oxidized to produce the well-known Co-OEC heterogeneous cobaltate catalyst, which is an active water oxidation catalyst. We present results from electron paramagnetic resonance spectroscopy, nuclear magnetic resonance line broadening analysis, and electrochemical titrations to establish the existence of the Co(II) impurity as the major source of water oxidation activity that has been reported for Co 4O 4 molecular cubanes. Differential electrochemical mass spectrometry is used to characterize the fate of glassy carbon at water oxidizing potentials andmore » demonstrate that such electrode materials should be used with caution for the study of water oxidation catalysis.« less

  12. Formation of Fe3O4@SiO2@C/Ni hybrids with enhanced catalytic activity and histidine-rich protein separation.

    PubMed

    Zhang, Yanwei; Zhang, Min; Yang, Jinbo; Ding, Lei; Zheng, Jing; Xu, Jingli; Xiong, Shenglin

    2016-09-21

    In this paper, we have developed an extended Stöber method to construct a Ni(2+)-polydopamine (PDA) complex thin coating on Fe3O4@SiO2 spheres, which can be carbonized to produce hybrid composites with metallic nickel nanoparticles embedded in a PDA-derived thin graphitic carbon layer (named Fe3O4@SiO2@C/Ni). Interestingly, by introducing a thin SiO2 spacer layer between PDA-Ni(2+) and Fe3O4, the reverse electron transfer from PDA to Fe3O4 is probably able to be suppressed in the calcination process, which leads to the in situ reduction of only Ni(2+) by PDA instead of Fe3O4 and Ni(2+). Consequently, the size and density of nickel nanoparticles on the surface of SiO2@Fe3O4 can be finely adjusted. Moreover, it is found that the ability of tuning nickel nanoparticles is mainly dependent on the thickness of the spacer layer. When the thickness of the SiO2 spacer is beyond the electron penetration depth, the size and density of nickel nanoparticles can be exactly tuned. The as-prepared Fe3O4@SiO2@C/Ni was employed as the catalyst to investigate the catalytic performance in the reduction of 4-nitrophenol (4-NP); furthermore, nickel nanoparticles decorated on Fe3O4@SiO2@C spheres display a strong affinity to His-tagged proteins (BHb and BSA) via a specific metal affinity force between polyhistidine groups and nickel nanoparticles.

  13. Single-Crystal Thin Films of Cesium Lead Bromide Perovskite Epitaxially Grown on Metal Oxide Perovskite (SrTiO 3)

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Chen, Jie; Morrow, Darien J.; Fu, Yongping

    High-quality metal halide perovskite single crystals have low defect densities and excellent photophysical properties, yet thin films are the most sought after material geometry for optoelectronic devices. Perovskite single-crystal thin films (SCTFs) would be highly desirable for high-performance devices, but their growth remains challenging, particularly for inorganic metal halide perovskites. Herein, we report the facile vapor-phase epitaxial growth of cesium lead bromide perovskite (CsPbBr 3) continuous SCTFs with controllable micrometer thickness, as well as nanoplate arrays, on traditional oxide perovskite SrTiO 3(100) substrates. Heteroepitaxial single-crystal growth is enabled by the serendipitous incommensurate lattice match between these two perovskites, and overcomingmore » the limitation of island-forming Volmer–Weber crystal growth is critical for growing large-area continuous thin films. Time-resolved photoluminescence, transient reflection spectroscopy, and electrical transport measurements show that the CsPbBr 3 epitaxial thin film has a slow charge carrier recombination rate, low surface recombination velocity (10 4 cm s –1), and low defect density of 10 12 cm –3, which are comparable to those of CsPbBr 3 single crystals. This work suggests a general approach using oxide perovskites as substrates for heteroepitaxial growth of halide perovskites. Furthermore, the high-quality halide perovskite SCTFs epitaxially integrated with multifunctional oxide perovskites could open up opportunities for a variety of high-performance optoelectronics devices.« less

  14. Single-Crystal Thin Films of Cesium Lead Bromide Perovskite Epitaxially Grown on Metal Oxide Perovskite (SrTiO 3)

    DOE PAGES

    Chen, Jie; Morrow, Darien J.; Fu, Yongping; ...

    2017-09-05

    High-quality metal halide perovskite single crystals have low defect densities and excellent photophysical properties, yet thin films are the most sought after material geometry for optoelectronic devices. Perovskite single-crystal thin films (SCTFs) would be highly desirable for high-performance devices, but their growth remains challenging, particularly for inorganic metal halide perovskites. Herein, we report the facile vapor-phase epitaxial growth of cesium lead bromide perovskite (CsPbBr 3) continuous SCTFs with controllable micrometer thickness, as well as nanoplate arrays, on traditional oxide perovskite SrTiO 3(100) substrates. Heteroepitaxial single-crystal growth is enabled by the serendipitous incommensurate lattice match between these two perovskites, and overcomingmore » the limitation of island-forming Volmer–Weber crystal growth is critical for growing large-area continuous thin films. Time-resolved photoluminescence, transient reflection spectroscopy, and electrical transport measurements show that the CsPbBr 3 epitaxial thin film has a slow charge carrier recombination rate, low surface recombination velocity (10 4 cm s –1), and low defect density of 10 12 cm –3, which are comparable to those of CsPbBr 3 single crystals. This work suggests a general approach using oxide perovskites as substrates for heteroepitaxial growth of halide perovskites. Furthermore, the high-quality halide perovskite SCTFs epitaxially integrated with multifunctional oxide perovskites could open up opportunities for a variety of high-performance optoelectronics devices.« less

  15. Inkjet-printed p-type nickel oxide thin-film transistor

    NASA Astrophysics Data System (ADS)

    Hu, Hailong; Zhu, Jingguang; Chen, Maosheng; Guo, Tailiang; Li, Fushan

    2018-05-01

    High-performance inkjet-printed nickel oxide thin-film transistors (TFTs) with Al2O3 high-k dielectric have been fabricated using a sol-gel precursor ink. The "coffee ring" effect during the printing process was facilely restrained by modifying the viscosity of the ink to control the outward capillary flow. The impacts on the device performance was studied in detail in consideration of annealing temperature of the nickel oxide film and the properties of dielectric layer. The optimized switching ability of the device were achieved at an annealing temperature of 280 °C on a 50-nm-thick Al2O3 dielectric layer, with a hole mobility of 0.78 cm2/V·s, threshold voltage of -0.6 V and on/off current ratio of 5.3 × 104. The as-printed p-type oxide TFTs show potential application in low-cost, large-area complementary electronic devices.

  16. Polydopamine-Coated TiO2 Nanotubes for Selective Photocatalytic Oxidation of Benzyl Alcohol to Benzaldehyde Under Visible Light.

    PubMed

    Tripathy, Jyotsna; Loget, Gabriel; Altomare, Marco; Schmuki, Patrik

    2016-05-01

    TiO2 nanotube arrays grown by anodization were coated with thin layers of polydopamine as visible light sensitizer. The PDA-coated TiO2 scaffolds were used as photocatalyst for selective oxidation of benzyl alcohol under monochromatic irradiation at 473 nm. Benzaldehyde was selectively formed and no by-products could be detected. A maximized reaction yield was obtained in O2-saturated acetonitrile. A mechanism is proposed that implies firstly the charge carrier generation in polydopamine as a consequence of visible light absorption. Secondly, photo-promoted electrons are injected in TiO2 conduction band, and subsequently transferred to dissolved O2 to form O*2- radicals. These radicals react with benzyl alcohol and lead to its selective dehydrogenation oxidation towards benzaldehyde.

  17. Dip coated TiO2 nanostructured thin film: synthesis and application

    NASA Astrophysics Data System (ADS)

    Vanaraja, Manoj; Muthukrishnan, Karthika; Boomadevi, Shanmugam; Karn, Rakesh Kumar; Singh, Vijay; Singh, Pramod K.; Pandiyan, Krishnamoorthy

    2016-02-01

    TiO2 thin film was fabricated by dip coating method using titanium IV chloride as precursor and sodium carboxymethyl cellulose as thickening as well as capping agent. Structural and morphological features of TiO2 thin film were characterized by X-ray diffractometer and field emission scanning electron microscope, respectively. Crystallinity of the film was confirmed with high-intensity peak at (101) plane, and its average crystallite size was found to be 28 nm. The ethanol-sensing properties of TiO2 thin film was studied by the chemiresistive method. Furthermore, various gases were tested in order to verify the selectivity of the sensor. Among the several gases, the fabricated TiO2 sensor showed very high selectivity towards ethanol at room temperature.

  18. Unusual Ferroelectricity in Two-Dimensional Perovskite Oxide Thin Films.

    PubMed

    Lu, Jinlian; Luo, Wei; Feng, Junsheng; Xiang, Hongjun

    2018-01-10

    Two-dimensional (2D) ferroelectricity have attracted much attention due to their applications in novel miniaturized devices such as nonvolatile memories, field effect transistors, and sensors. Since most of the commercial ferroelectric (FE) devices are based on ABO 3 perovskite oxides, it is important to investigate the properties of 2D ferroelectricity in perovskite oxide thin films. Here, based on density functional theory (DFT) calculations, we find that there exist three kinds of in-plane FE states that originate from different microscopic mechanisms: (i) a proper FE state with the polarization along [110] due to the second-order Jahn-Teller effect related to the B ion with empty d-orbitals; (ii) a robust FE state with the polarization along [100] induced by the surface effect; (iii) a hybrid improper FE state with the polarization along [110] that is induced by the trilinear coupling between two rotational modes and the A-site displacement. Interestingly, the ferroelectricity in the latter two cases becomes stronger along with decreasing the thin film thickness, in contrast to the usual behavior. Moreover, the latter two FE states are compatible with magnetism since their stability does not depend on the occupation of the d-orbitals of the B-ion. These two novel 2D FE mechanisms provide new avenues to design 2D multiferroics, as we demonstrated in SrVO and CaFeO thin film cases. Our work not only reveals new physical mechanisms of 2D ferroelectricity in perovskite oxide thin films but also provides a new route to design the high-performance 2D FE and multiferroics.

  19. ZnO Nanoparticles/Reduced Graphene Oxide Bilayer Thin Films for Improved NH3-Sensing Performances at Room Temperature

    NASA Astrophysics Data System (ADS)

    Tai, Huiling; Yuan, Zhen; Zheng, Weijian; Ye, Zongbiao; Liu, Chunhua; Du, Xiaosong

    2016-03-01

    ZnO nanoparticles and graphene oxide (GO) thin film were deposited on gold interdigital electrodes (IDEs) in sequence via simple spraying process, which was further restored to ZnO/reduced graphene oxide (rGO) bilayer thin film by the thermal reduction treatment and employed for ammonia (NH3) detection at room temperature. rGO was identified by UV-vis absorption spectra and X-ray photoelectron spectroscope (XPS) analyses, and the adhesion between ZnO nanoparticles and rGO nanosheets might also be formed. The NH3-sensing performances of pure rGO film and ZnO/rGO bilayer films with different sprayed GO amounts were compared. The results showed that ZnO/rGO film sensors exhibited enhanced response properties, and the optimal GO amount of 1.5 ml was achieved. Furthermore, the optimal ZnO/rGO film sensor showed an excellent reversibility and fast response/recovery rate within the detection range of 10-50 ppm. Meanwhile, the sensor also displayed good repeatability and selectivity to NH3. However, the interference of water molecules on the prepared sensor is non-ignorable; some techniques should be researched to eliminate the effect of moisture in the further work. The remarkably enhanced NH3-sensing characteristics were speculated to be attributed to both the supporting role of ZnO nanoparticles film and accumulation heterojunction at the interface between ZnO and rGO. Thus, the proposed ZnO/rGO bilayer thin film sensor might give a promise for high-performance NH3-sensing applications.

  20. Interaction mechanisms between α-Fe2O3, γ-Fe2O3 and Fe3O4 nanoparticles and Citrus maxima seedlings.

    PubMed

    Li, Junli; Hu, Jing; Xiao, Lian; Wang, Yunqiang; Wang, Xilong

    2018-06-01

    The interactions between α-Fe 2 O 3 , γ-Fe 2 O 3 , and Fe 3 O 4 nanoparticles (NPs) and Citrus maxima seedlings were examined so as to better understand possible particle applications as an Fe source for crop plants. NPs toxicity to the exposed plant was investigated as well. The α- and γ-Fe 2 O 3 NPs were accumulated by plant root cells through diapirism and endocytosis, respectively, but translocation to the shoots was negligible. Analysis of malondialdehyde (MDA), soluble protein content, and antioxidant enzyme activity revealed that Fe deficiency induced strong oxidative stress in Citrus maxima seedlings, which followed an order of Fe deficiency>Fe 3+ >α-Fe 2 O 3 , γ-Fe 2 O 3 NPs>Fe 3 O 4 NPs. However, the chlorophyll leaf content of plants exposed to α-Fe 2 O 3 , γ-Fe 2 O 3 , Fe 3 O 4 NPs and Fe 3+ were significantly reduced by 31.1%, 14.8%, 18.8% and 22.0%, respectively, relative to the control. Furthermore, RT-PCR analysis revealed no up-regulation of AHA and Nramp3 genes in Citrus maxima roots; however, the relative FRO2 gene expression upon exposure to iron oxide NPs was 1.4-2.8-fold higher than the control. Ferric reductase activity was consistently enhanced upon iron oxide NPs exposure. These findings advance understanding of the interaction mechanisms between metal oxide NPs and plants, and provide important knowledge need for the possible application of these materials in agriculture. Copyright © 2017 Elsevier B.V. All rights reserved.