Diamond-like carbon (DLC) is a metastable form of amorphous carbon with significant sp3 bonding. DLC is a semiconductor with a high mechanical hardness, chemical inertness, and optical transparency. This review will describe the deposition methods, deposition mechanisms, characterisation methods, electronic structure, gap states, defects, doping, luminescence, field emission, mechanical properties and some applications of DLCs. The films have widespread applications as protective coatings in areas, such as magnetic storage disks, optical windows and micro-electromechanical devices (MEMs).

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Diamond-like amorphous carbon

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.

Recent technical advances in the atomic-scale synthesis of oxide heterostructures have provided a fertile new ground for creating novel states at their interfaces. Different symmetry constraints can be used to design structures exhibiting phenomena not found in the bulk constituents. A characteristic feature is the reconstruction of the charge, spin and orbital states at interfaces on the nanometre scale. Examples such as interface superconductivity, magneto-electric coupling, and the quantum Hall effect in oxide heterostructures are representative of the scientific and technological opportunities in this rapidly emerging field.

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Emergent phenomena at oxide interfaces

BiVO4 photocatalysts for O2 evolution, which work under visible light irradiation, were prepared by an aqueous process. The BiVO4 photocatalysts were obtained by the reaction of layered potassium vanadate powder (KV3O8 and K3V5O14) with Bi(NO3)3 for 3 days in aqueous media at room temperature. Highly crystalline monoclinic and tetragonal BiVO4 were selectively synthesized by changing the ratio of vanadium to bismuth in the starting materials. X-ray diffraction and scanning electron microscopy measurements showed that the monoclinic BiVO4 was formed via a tetragonal BiVO4 intermediate. Tetragonal BiVO4 with a 2.9 eV band gap mainly possessed an ultraviolet absorption band while monoclinic BiVO4 with a 2.4 eV band gap had a characteristic visible light absorption band in addition to the UV band. The UV bands observed in the tetragonal and monoclinic BiVO4 were assigned to the band transition from O2p to V3d whereas the visible light absorption was due to the transition from a valence band formed by Bi6s or ...

A Novel Aqueous Process for Preparation of Crystal Form-Controlled and Highly Crystalline BiVO4 Powder from Layered Vanadates at Room Temperature and Its Photocatalytic and Photophysical Properties

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

Systemes et procedes permettant de produire des pointes de carbone a base elargie. L'un desdits procedes de production d'une pointe de carbone a base elargie consiste a fabriquer une base elargie contenant du carbone sur un substrat, puis a fabriquer une fibre contenant du carbone sur la base elargie. Un appareil selon la presente invention comporte une base elargie contenant du carbone couplee a un substrat et une fibre contenant du carbone couplee a ladite base elargie contenant du carbone.

Pointes de carbone a base elargie

L'invention concerne un systeme et des procedes pour puces a reseaux d'emission de champ adressables. Selon l'invention, le procede de realisation d'un reseau d'emission de champ adressable consiste : a generer une pluralite de faisceaux electroniques a partir d'une pluralite d'emetteurs composant le reseau d'emission de champ adressable ; et a focaliser l'un de ces faisceaux electroniques au moins au moyen d'une pile de focalisation electrostatique integree a la puce. Le systeme et les procedes selon l'invention sont avantageux en ce qu'ils permettent d'eviter les « explosions » dues aux charges d'espace.

Puces a reseaux d'emission de champ adressables a focalisation electrostatique pour gravure numerique en serie, en parallele, par faisceau electronique, sans masque et haute vitesse et microscopie electronique a balayage

Epitaxial YBa2Cu3O7−δ/PrBa2Cu3O7−δ (YBCO/PBCO) superlattices are tools for systematic, fundamental studies of high-temperature superconductivity. The variation of T c in YBCO/PBCO superlattices can be understood as arising from changes in the interlayer phase coupling between YBCO layers that are highly two-dimensional when they are very thin (∼1–2 c-axis unit cells) and completely isolated from each other. Single-cell-thick YBCO layers, containing isolated pairs of Cu02 planes, are found to be superconducting at T c ∼ 20 K, in a PBCO matrix. The resistance in the superconducting transition region scales with temperature as expected for the (flux flow) resistance produced by thermally generated 2D vortices, or for a 2D array of superconducting weak links. Relative to both thin-film and singlecrystal HTSc specimens, the thin superconducting layers in YBCO/PBCO superlattices exhibit a greatly expanded temperature range over which characteristic 2D dissipation can be observed, as a consequence of the enhanced anisotropy and reduced dimensionality of the YBCO layers. Scanning tunneling microscope studies reveal that YBCO films and YBCO/PBCO superlattices grow unit cell-by-unit cell by a terraced-island growth mechanism. On miscut, near-(001) substrates the terraces are epitaxially aligned with the substrate crystal lattice and spiral growth structures (screw dislocation-mediated growth) are not seen. These observations explain the steps or “kinks” that are seen in cross-section Z-contrast TEM images of YBCO/PBCO superlattices. The kinks may correspond physically to regions where the supercurrent must tunnel along the c-axis, and thus may be weak-link barriers.

Superconducting Properties and Microstructure of YBa2Cu3O7−δ/PrBa2Cu3O7−δ Superlattices

The principal interests in this work are energetic-beam control of carbon-film properties and the roles of doping and surface morphology in field emission.

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Field Emission from Carbon Films Deposited by Controlled-Low-Energy Beams and CVD Sources

L'invention concerne un procede pour assurer la croissance induite par catalyseurs de nanotubes de carbone, de nanofibres et d'autres nanostructures sur les pointes de nanofils, d'elements en porte-a-faux, de micro-structures/structures de nanometres, de plaquettes et similaires. Ce procede peut etre utilise pour la production d'elements en porte-a-faux ancres sur un nanotube de carbone qui peut ameliorer de maniere significative la performance des microscopes-sondes a balayage (microscopie a force atomique, microscopie a force electrostatique, etc). La presente invention peut egalement etre utilisee avec d'autres procedes de micro et/ou nanofabrication avec des nanotubes/fibres de carbone. Les elements cles de la presente invention comprennent : (1) la selection correcte d'un catalyseur metallique et le depot electrolytique programmable, par impulsions, du catalyseur specifique requis precisement a la pointe d'un substrat ; (2) la croissance induite par le catalyseur de nanotubes/fibres de carbones au niveau des pointes recouvertes par un depot de catalyseur ; (3) le controle du schema de croissance des nanotubes/fibres de carbone par manipulation de la forme de la pointe et des conditions de croissance ; et (4) l'automatisation en vue d'une production de masse.

Douglas H. Lowndes

Papers

Pointes de carbone a base elargie

Puces a reseaux d'emission de champ adressables a focalisation electrostatique pour gravure numerique en serie, en parallele, par faisceau electronique, sans masque et haute vitesse et microscopie electronique a balayage

Superconducting Properties and Microstructure of YBa2Cu3O7−δ/PrBa2Cu3O7−δ Superlattices

Field Emission from Carbon Films Deposited by Controlled-Low-Energy Beams and CVD Sources

Croissance induite par catalyseur de nanotubes de carbone sur les pointes d'elements en porte-a-faux et de nanofils