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

Gated field emission devices and systems and methods for their fabrication are described. A method includes growing a substantially vertically aligned carbon nanostructure, the substantially vertically aligned carbon nanostructure coupled to a substrate; covering at least a portion of the substantially vertically aligned carbon nanostructure with a dielectric; forming a gate, the gate coupled to the dielectric; and releasing the substantially vertically aligned carbon nanostructure by forming an aperture in the gate and removing a portion of the dielectric.

Gated fabrication of nanostructure field emission cathode material within a device

Both (001)‐ and (111)‐oriented CeO2 thin films have been grown on amorphous fused silica (SiO2) substrates by ion‐beam assisted pulsed laser ablation of a polycrystalline CeO2 target. Using 200 eV Ar+ ions incident at 55° to the substrate normal, the preferred orientation for CeO2 film growth is (001) at room temperature, but changes to (111) for temperatures ≥300 °C. Furthermore, the ion‐beam assisted CeO2 films exhibit strong in‐plane crystallographic alignment. In contrast, CeO2 films grown without ion‐beam assistance exhibit a mixture of polycrystalline orientations with the relative amounts depending on growth temperature. Under optimum conditions, off‐normal‐incidence Ar+ ions produce a (111)‐oriented crystalline CeO2 film that is aligned with respect to a single in‐plane axis, on an amorphous substrate.

In‐plane aligned CeO2 films grown on amorphous SiO2 substrates by ion‐beam assisted pulsed laser deposition

Field emission properties of dense and sparse “forests” of randomly placed, vertically aligned carbon nanofibers (VACNFs) were studied using a scanned probe with a small tip diameter of ∼1 μm. The probe was scanned in directions perpendicular and parallel to the sample plane, which allowed for measuring not only the emission turn-on field at fixed locations but also the emission site density over large surface areas. The results show that dense forests of VACNFs are not good field emitters as they require high extracting (turn-on) fields. This is attributed to the screening of the local electric field by the neighboring VACNFs. In contrast, sparse forests of VACNFs exhibit moderate-to-low turn-on fields as well as high emission site and current densities, and long emission lifetime, which makes them very promising for various field emission applications.

Scanned-Probe Field-Emission Studies of Vertically Aligned Carbon Nanofibers

Systems and methods are described for addressable field emission array (AFEA) chips. A method of operating an addressable field-emission array, includes: generating a plurality of electron beams from a pluralitly of emitters that compose the addressable field-emission array; and focusing at least one of the plurality of electron beams with an on-chip electrostatic focusing stack. The systems and methods provide advantages including the avoidance of space-charge blow-up.

Electrostatically focused addressable field emission array chips (AFEA's) for high-speed massively parallel maskless digital E-beam direct write lithography and scanning electron microscopy

We demonstrate the growth of silicon oxide nanowires through a sandwich-like configuration, i.e., Ga ball/Si polyhedrons/silicon oxide nanowires, by using Ga as the catalyst and SiO powder as the source material. The sandwich-like structures have a carrot-like morphology, consisting of three materials with different morphologies, states, and crystallographic structures. The “carrot” top is a liquid Ga ball with diameter of ∼10–30 μm; the middle part is a Si ring usually composed of about 10 μm-sized, clearly faceted, and crystalline Si polyhedrons that are arranged sequentially in a band around the lower hemisphere surface of the Ga ball; the bottom part is a carrot-shaped bunch of highly aligned silicon oxide nanowires that grow out from the downward facing facets of the Si polyhedrons. This study reveals several interesting nanowire growth phenomena that enrich the conventional vapor-liquid-solid nanowire growth mechanism.

Douglas H. Lowndes

Papers

Gated fabrication of nanostructure field emission cathode material within a device

In‐plane aligned CeO2 films grown on amorphous SiO2 substrates by ion‐beam assisted pulsed laser deposition

Scanned-Probe Field-Emission Studies of Vertically Aligned Carbon Nanofibers

Electrostatically focused addressable field emission array chips (AFEA's) for high-speed massively parallel maskless digital E-beam direct write lithography and scanning electron microscopy

Liquid gallium ball/crystalline silicon polyhedrons/aligned silicon oxide nanowires sandwich structure: An interesting nanowire growth route