In this critical review, metal oxides-based materials for electrochemical supercapacitor (ES) electrodes are reviewed in detail together with a brief review of carbon materials and conducting polymers. Their advantages, disadvantages, and performance in ES electrodes are discussed through extensive analysis of the literature, and new trends in material development are also reviewed. Two important future research directions are indicated and summarized, based on results published in the literature: the development of composite and nanostructured ES materials to overcome the major challenge posed by the low energy density of ES (476 references).

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A review of electrode materials for electrochemical supercapacitors

Multiferroic materials, which show simultaneous ferroelectric and magnetic ordering, exhibit unusual physical properties — and in turn promise new device applications — as a result of the coupling between their dual order parameters. We review recent progress in the growth, characterization and understanding of thin-film multiferroics. The availability of high-quality thin-film multiferroics makes it easier to tailor their properties through epitaxial strain, atomic-level engineering of chemistry and interfacial coupling, and is a prerequisite for their incorporation into practical devices. We discuss novel device paradigms based on magnetoelectric coupling, and outline the key scientific challenges in the field.

Multiferroics: progress and prospects in thin films.

In this review, the technologies and working principles of different materials used in supercapacitors are explained. The most important supercapacitor active materials are discussed from both research and application perspectives, together with brief explanations of their properties, such as specific surface area and capacitance values. A review of different supercapacitor electrolytes is given and their positive and negative features are discussed. Finally, cell configurations are considered, pointing out the advantages and drawbacks of each configuration.

Review on supercapacitors: Technologies and materials

An overview of the state of art in ferroelectric thin films is presented. First, we review applications: microsystems' applications, applications in high frequency electronics, and memories based on ferroelectric materials. The second section deals with materials, structure (domains, in particular), and size effects. Properties of thin films that are important for applications are then addressed: polarization reversal and properties related to the reliability of ferroelectric memories, piezoelectric nonlinearity of ferroelectric films which is relevant to microsystems' applications, and permittivity and loss in ferroelectric films-important in all applications and essential in high frequency devices. In the context of properties we also discuss nanoscale probing of ferroelectrics. Finally, we comment on two important emerging topics: multiferroic materials and ferroelectric one-dimensional nanostructures. (c) 2006 American Institute of Physics.

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Ferroelectric thin films: Review of materials, properties, and applications

In the laser treatment of a workpiece (9), e.g. for surface hardening, melting, alloying, cladding, welding or cutting, the adverse effect of reflectivity of the surface, when a pure, monochromatic laser (6) is used, is remedied by the simultaneous application of a relatively shorter wavelength beam (1). The two beams (1)(5) may be combined by a beam coupler (4) or may reach the workpiece (9) by separate optical paths (not shown). The shorter wavelength beam (1) improves the coupling efficiency of the higher- powered laser beam (5).

Laser Material Processing

Ion-assisted, ion-beam sputter deposition is used to obtain (00l) biaxially oriented films of cubic yttria-stabilized-zirconia (YSZ) on polycrystalline metal substrates. Yttrium-barium-copper-oxide (YBCO) is then heteroepitaxially-pulse-laser deposited onto the YSZ. Phi scans of the films show the full-width-half maxima of the YSZ (202) and the YBCO(103) reflections to be 14{degree} and 10{degree} respectively. Our best dc transport critical current density measurement for the YBCO is 800,000 A/cm{sup 2} at 75K and 0T. At 75K, the total dc transport current in a 1 cm wide YBCO film is 23 A.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S1946427400304808

Fabrication of Biaxially Oriented YBCO on (00 l ) Biaxially Oriented Yttria-Stabilized-Zirconia on Polycrystalline Substrates

A processing technique is developed to fabricate single-crystal yttria-stabilized zirconia (YSZ) on amorphous SiO2 on (100) single-crystal Si. The YSZ layer shows high crystallinity with an ion beam channelling minimum of 11 % from Rutherford backscattering. Even though there is a thick intervening amorphous SiO2 layer between the Si and the YSZ, the single-crystal YSZ layer is aligned with the crystal Si. The tilt and rotation variations are 0·64° and 1·11° respectively, based on X-ray diffraction Ω-rocking curves on [100] and π scans on [202] of YSZ films. The epitaxial nature of the YSZ on the thick SiO2 layer (from 10 to 100 nm) is further confirmed by high-resolution cross-sectional transmission electron microscopy analysis. This processing and the resulting multilayer structure might provide a new option for fabricating innovative microelectronic devices.

Deposition of epitaxial yttria-stabilized zirconia on single-crystal Si and subsequent growth of an amorphous SiO2 interlayer

Epitaxial YBa2Cu3O7−δ (YBCO) thin films were deposited on (100) MgO using platinum and SrRuO3 (SRO) buffer layers by pulsed laser deposition. The films were (001) textured normal to substrate surface with a high degree of in‐plane orientation with respect to the substrate’s major axes. YBCO films showed superconducting transition temperature (Tco) at 91 K and critical current densities were found to be 2–3×106 A/cm2 at 77 K and zero field. An ion beam minimum channeling yield of 16% was obtained for YBCO films, indicating high crystallinity. The orientation relationship for this epitaxial multilayer structure was found to be (100) YBCO∥(100) SRO∥(100)Pt∥(100) MgO. This result showed that high‐quality superconducting thin films can be deposited on metal with an appropriate buffer layer.

Epitaxial YBa2Cu3O7−δ thin films on SrRuO3/Pt/MgO

We have investigated epitaxial superconducting SmBa2Cu3O7 (Sm123) films grown by pulsed-laser deposition on single-crystal SrTiO3 substrates. The deposition temperature plays an important role in determining the superconducting properties of Sm123 films. The superconducting transition temperature increases with the deposition temperature whereas the transition width decreases at deposition temperatures in the range of 700–875 °C. A Sm123 film deposited at 850 °C exhibits a transition temperature above 93 K with a transition width less than 0.5 K. Even though Sm123 films exhibit a higher transition temperature than Yba2Cu3O7 (Y123), the Sm123 shows lower critical current density at liquid-nitrogen temperature. The nominal critical current density of Sm123 film is less than 1 MA/cm2 at 75.4 K. Nevertheless, the Sm123 films have less anisotropy and stronger pinning characteristics compared to Y123. They are also much smoother with fewer particulates, as revealed by scanning electron microscopy.

Characterization of superconducting SmBa2Cu3O7 films grown by pulsed laser deposition

Highly conductive metal-oxide RuO2 thin films have been successfully grown on yttria-stabilized zirconia (YSZ) substrates by pulsed laser deposition. Epitaxial growth of RuO2 thin films on YSZ and the atomically sharp interface between the RuO2 and the YSZ substrate are clearly evident from cross-sectional transmission electron microscopy. A diagonal-type epitaxy of RuO2 on YSZ is confirmed from x-ray diffraction measurements. The crystalline RuO2 thin films, deposited at temperatures in the range of 500 °C to 700 °C, have a room-temperature resistivity of 35 ± 2 μω-cm, and the residual resistance ratio (R
300 k/R
4.2 k) is around 5 for the crystalline RuO2 thin films.

S. R. Foltyn

Papers

Fabrication of Biaxially Oriented YBCO on (00 l ) Biaxially Oriented Yttria-Stabilized-Zirconia on Polycrystalline Substrates

Deposition of epitaxial yttria-stabilized zirconia on single-crystal Si and subsequent growth of an amorphous SiO2 interlayer

Epitaxial YBa2Cu3O7−δ thin films on SrRuO3/Pt/MgO

Characterization of superconducting SmBa2Cu3O7 films grown by pulsed laser deposition

Deposition and characterization of crystalline conductive ruo2 thin films