Amorphous and highly nonstoichiometric titania (TiOx) thin films close to metal-like conductivity

Leichtweiß, Thomas; Henning, Ralph A.; Koettgen, Julius; Schmidt, Rüdiger; Holländer, B.; Martin, Manfred; Wuttig, Matthias; Janek, Jürgen

doi:10.1039/c3ta14816e

Cited by 59 publications

(39 citation statements)

References 54 publications

(54 reference statements)

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“…For the sample with the band gap corresponding to TiO 2 (P7), the resistivity was in the order of 10 5 Ω cm. Similar results has been reported in the literature [20], where the samples with dark color exhibit low electrical resistivity; after a thermal annealing at 600°C the samples become transparent (due to the full oxidation of the TiO x film), increasing electrical resistivity in four orders of magnitude.…”

Section: Resultssupporting

confidence: 86%

“…Nakano et al [23] reported visible light photocatalytic activity of of oxygen deficient TiO 2 films obtained by Ar/H 2 plasma surface treatment; Dong et al [24] anodization for visible light photocatalysis; Lee et al [26] grew N-doped TiO x films using reactive sputtering reporting a red-shift band gap; and Leichweiss et al [20] grewn highly nonstoichiometric TiO x thin films, that shown high efficiency for water splitting reaction, using pulsed laser deposition at room temperature. Related to the activation of TiO 2 by infrared radiation, we only found the work of Gannoruwa et al [28], they reported that the nanocomposite Ag 2 O/TiO 2 was infrared active in the range from 800 nm to 1200 nm.…”

Section: Introductionmentioning

confidence: 98%

“…However, for practical application, TiO x thin films are more adequate than powders. Several methods can be used to prepare TiO x thin films, such as blow arc discharge [19], pulsed laser deposition [20], plasma assisted chemical vapor deposition [21,22], plasma surface treatment [23], anodization [24] and reactive magnetron sputtering [25][26][27]. Among these methods, the magnetron sputtering method allows an easy control of the films structure and composition besides provides many advantages in reproducibility, high mechanical durability, strong adhesion and uniformity and it is applicable to large area deposition.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Visible and infrared photocatalytic activity of TiO thin films prepared by reactive sputtering

Zapata‐Torres

Hernández-Rodríguez

Mis-Fernández

et al. 2015

Materials Science in Semiconductor Processing

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Section: Resultssupporting

confidence: 86%

Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Visible and infrared photocatalytic activity of TiO thin films prepared by reactive sputtering

Zapata‐Torres

Hernández-Rodríguez

Mis-Fernández

et al. 2015

Materials Science in Semiconductor Processing

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“…The compositions of the pellets were successfully verified using energy dispersive X‐ray spectroscopy measurements (Oxford INCA, Oxford Instruments). Using X‐ray diffraction measurements (

θ / θ

‐diffractometer, STOE & Cie GmbH with secondary monochromator or X'Pert Pro diffractometer, PANalytical, Almelo, Netherlands, with Ni‐Filter), the phase purity was investigated and the lattice parameters are in agreement to literature for Sm‐ and Gd‐doped ceria . Especially, the long‐lasting measurements with the X'Pert Pro diffractometer feature an outstanding resolution and signal‐to‐noise ratio ensuring the highly sensitive detection limit for impurities, which is required in this work.…”

Section: Methodsmentioning

confidence: 62%

The ionic conductivity of Sm‐doped ceria

Koettgen

Martin

2020

J Am Ceram Soc

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The oxygen ion conductivity of polycrystalline samples of Sm‐doped ceria and of Gd‐doped ceria is studied as a function of doping fraction and temperature using impedance spectroscopy allowing the separation of bulk and grain boundary conductivity. The introduction of a fine spacing for the Sm dopant fraction allows the clear identification of the dopant fraction leading to the largest bulk conductivity. At 267°C, the largest bulk conductivity is shown for Ce0.93Sm0.07O1.965. With increasing temperature, indications of an increase in the dopant fraction, which leads to the maximum in conductivity, are found. For the grain boundary conductivity, the maximum appears at larger dopant fractions compared to the bulk conductivity. The largest total conductivity for both dopants is again found for Sm‐doped ceria. In literature, different syntheses and sample preparation methods led to larger total conductivities for Gd‐doped ceria. In this work, we demonstrate that the variation of sintering conditions leads to scattering in the conductivity over one order of magnitude. Finally, we demonstrate that, in nominally pure cerium oxide, impurities dominate the ionic conductivity.

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“…In either case, the existence of off‐stoichiometry metal oxide surface may be used for redox‐based chemical catalysis. It is also interesting to note that thin epitaxial layers of cubic TiO have been characterized as superconductors with T C up to 7.4 K . Thus, the coverage of the BaTiO 3 crystals with a functional TiO x surface and the ability to pattern this phase locally may help nanoscale fabrication of superconducting‐based technologies.…”

Section: Resultsmentioning

confidence: 99%

Epitaxial TiO_x Surface in Ferroelectric BaTiO₃: Native Structure and Dynamic Patterning at the Atomic Scale

Barzilay

Qiu

Rappe

et al. 2019

Adv Funct Materials

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Surfaces and interfaces of ferroelectric oxides exhibit enhanced functionality, and therefore serve as a platform for novel nano and quantum technologies. Experimental and theoretical challenges associated with examining the subtle electro-chemo-mechanical balance at metal-oxide surfaces have hindered the understanding and control of their structure and behavior. Here, combined are advanced electron-microscopy and firstprinciples thermodynamics methods to reveal the atomic-scale chemical and crystallographic structure of the surface of the seminal ferroelectric BaTiO 3 . It is shown that the surface is composed of a native <2 nm thick TiO x rock-salt layer in epitaxial registry with the BaTiO 3 . Using electronbeam irradiation, artificial TiO x sites with sub-nanometer resolution are successfully patterned, by inducing Ba escape. Therefore, this work offers electro-chemo-mechanical insights into ferroelectric surface behavior in addition to a method for scalable high-resolution beam-induced chemical lithography for selectively driving surface phase transitions, and thereby functionalizing metal-oxide surfaces.The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10. 1002/adfm.201902549. in oxidation states of the participating ions. Hence, functional-oxide surfaces and interfaces constitute a rich platform for novel phases that are attractive for high-performance miniaturized electronic devices [7,8] as well as for chemical catalyses. [9] Because ferroelectric oxides comprise regions with varying crystallographic and electric polarization orientations, there has been a growing interest in their outer surface and domain wall functionality, which is expressed as enhanced conductivity, [10][11][12] magnetism, [4] and even superconductivity. [13] The chemical origin of such a functional behavior is typically attributed to either oxygen vacancy dynamics [14][15][16][17] or cation segregation, [18] while other studies look at the effects of intrinsic symmetry breaking. [4] Despite the accumulated knowledge on domain walls, the structure and behavior of ferroelectric surfaces, which are responsible for domain stabilization and are attractive for, e.g., nano lithography [19][20][21][22][23] and catalysis, [9,[24][25][26][27] have remained elusive. Specifically, the longstanding challenge in understanding how the surface mediates between the absence of electric and mechanical fields in the vacuum and the polarization, and strain in the bulk is not merely experimental or theoretical, but even conceptual. [28] Hence, computational methods that were developed to explain the electro-chemical [29] and electro-mechanical [30] atomic-scale interactions in ferroelectrics have been adopted to describe experimental observations of the surface behavior. For example, Tsurumi et al. [31,32] combined dielectric measurements and density functional theory (DFT) calculations to demonstrate that nanoparticles (NPs) of the seminal nontoxic ferroelectric, BaTiO 3 , organize in a core-shell...

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Amorphous and highly nonstoichiometric titania (TiOx) thin films close to metal-like conductivity

Cited by 59 publications

References 54 publications

Visible and infrared photocatalytic activity of TiO thin films prepared by reactive sputtering

Visible and infrared photocatalytic activity of TiO thin films prepared by reactive sputtering

The ionic conductivity of Sm‐doped ceria

Epitaxial TiO_x Surface in Ferroelectric BaTiO₃: Native Structure and Dynamic Patterning at the Atomic Scale

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Amorphous and highly nonstoichiometric titania (TiOx) thin films close to metal-like conductivity

Cited by 59 publications

References 54 publications

Visible and infrared photocatalytic activity of TiO thin films prepared by reactive sputtering

Visible and infrared photocatalytic activity of TiO thin films prepared by reactive sputtering

The ionic conductivity of Sm‐doped ceria

Epitaxial TiOx Surface in Ferroelectric BaTiO3: Native Structure and Dynamic Patterning at the Atomic Scale

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Epitaxial TiO_x Surface in Ferroelectric BaTiO₃: Native Structure and Dynamic Patterning at the Atomic Scale