CuO nanostructures: Synthesis, characterization, growth mechanisms, fundamental properties, and applications

One dimensional nanostructured materials

Recent advances in the field of nanotechnology have led to the synthesis and characterization of an assortment of quasi-one-dimensional (Q1D) structures, such as nanowires, nanoneedles, nanobelts and nanotubes. These fascinating materials exhibit novel physical properties owing to their unique geometry with high aspect ratio. They are the potential building blocks for a wide range of nanoscale electronics, optoelectronics, magnetoelectronics, and sensing devices. Many techniques have been developed to grow these nanostructures with various compositions. Parallel to the success with group IV and groups III–V compounds semiconductor nanostructures, semiconducting metal oxide materials with typically wide band gaps are attracting increasing attention. This article provides a comprehensive review of the state-of-the-art research activities that focus on the Q1D metal oxide systems and their physical property characterizations. It begins with the synthetic mechanisms and methods that have been exploited to form these structures. A range of remarkable characteristics are then presented, organized into sections covering a number of metal oxides, such as ZnO, In2O3, SnO2 ,G a 2O3, and TiO2, etc., describing their electrical, optical, magnetic, mechanical and chemical sensing properties. These studies constitute the basis for developing versatile applications based on metal oxide Q1D systems, and the current progress in device development will be highlighted. # 2006 Elsevier B.V. All rights reserved.

Quasi-one-dimensional metal oxide materials—Synthesis, properties and applications

Wearable electronics is expected to be one of the most active research areas in the next decade; therefore, nanomaterials possessing high carrier mobility, optical transparency, mechanical robustness and flexibility, lightweight, and environmental stability will be in immense demand. Graphene is one of the nanomaterials that fulfill all these requirements, along with other inherently unique properties and convenience to fabricate into different morphological nanostructures, from atomically thin single layers to nanoribbons. Graphene-based materials have also been investigated in sensor technologies, from chemical sensing to detection of cancer biomarkers. The progress of graphene-based flexible gas and chemical sensors in terms of material preparation, sensor fabrication, and their performance are reviewed here. The article provides a brief introduction to graphene-based materials and their potential applications in flexible and stretchable wearable electronic devices. The role of graphene in fabricating ...

Flexible Graphene-Based Wearable Gas and Chemical Sensors

The surface chemistry of cerium oxide

Emerging trends in wide band gap semiconductors (SiC and GaN) technology for power devices

Recently, giant carrier mobility μ (>10(5) cm(2) V(-1) s(-1)) and micrometer electron mean free path (l) have been measured in suspended graphene or in graphene encapsulated between inert and ultraflat BN layers. Much lower μ values (10000-20000 cm(2) V(-1) s(-1)) are typically reported in graphene on common substrates (SiO(2), SiC) used for device fabrication. The debate on the factors limiting graphene electron mean free path is still open with charged impurities (CI) and resonant scatterers (RS) indicated as the most probable candidates. As a matter of fact, the inhomogeneous distribution of such scattering sources in graphene is responsible of nanoscale lateral inhomogeneities in the electronic properties, which could affect the behavior of graphene nanodevices. Hence, high resolution two-dimensional (2D) mapping of their density is very important. Here, we used scanning capacitance microscopy/spectroscopy to obtain 2D maps of l in graphene on substrates with different dielectric permittivities, that is, SiO(2) (κ(SiO2) = 3.9), 4H-SiC (0001) (κ(SiC) = 9.7) and the very-high-κ perovskite strontium titanate, SrTiO(3) (001), briefly STO (κ(STO) = 330). After measuring l versus the gate bias V(g) on an array of points on graphene, maps of the CI density (N(CI)) have been determined by the neutrality point shift from V(g) = 0 V in each curve, whereas maps of the RS density (N(RS)) have been extracted by fitting the dependence of l on the carrier density (n). Laterally inhomogeneous densities of CI and RS have been found. The RS distribution exhibits an average value ∼3 × 10(10) cm(-2) independently on the substrate. For the first time, a clear correlation between the minima in the l map and the maxima in the N(CI) map is obtained for graphene on SiO(2) and 4H-SiC, indicating that CI are the main source of the lateral inhomogeneity of l. On the contrary, the l and N(CI) maps are uncorrelated in graphene on STO, while a clear correlation is found between l and N(RS) maps. This demonstrates a very efficient dielectric screening of CI in graphene on STO and the role of RS as limiting factor for electron mean free path.

Mapping the Density of Scattering Centers Limiting the Electron Mean Free Path in Graphene

Wide band gap semiconductors, and in particular silicon carbide (4H-SiC) and gallium nitride (GaN), are very promising materials for the next generation of power electronics, to guarantee an improved energy efficiency of devices and modules. As a matter of fact, in the last decade intensive academic and industrial research efforts have resulted in the demonstration of both 4H-SiC MOSFETs and GaN HEMTs exhibiting VB2/Ron performances well beyond the silicon limits.

In this paper, some of the present scientific challenges for SiC and GaN power devices technology are reviewed. In particular, the topics selected in this work will be the SiO2/SiC interface passivation processes to improve the channel mobility in 4H-SiC MOSFETs, the current trends for gate dielectrics in GaN technology and the viable routes to obtain normally-off HEMTs.

Challenges for energy efficient wide band gap semiconductor power devices

Ordered homogeneous arrays of copper (II) oxide nanotubes have been fabricated through an MOCVD template route. SEM images of the CuO nanotubes, after removing the template, indicate the formation of well-ordered nanotube arrays. There is evidence that nanotubes are opened on both sides.

Free-Standing Copper(II) Oxide Nanotube Arrays through an MOCVD Template Process

Nanoscale imaging of the electrical properties of CaCu3Ti4O12 ceramics has been performed using scanning impedance microscopy. Two kinds of electrical inhomogeneity are detected, namely, depletion layers at grain boundaries and calcium titanate inclusions, both of which are more resistive than the bulk of the grains. Energy filtered transmission electron microscopy was used to estimate the chemical composition of the inclusions.

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Raffaella Lo Nigro

Papers

Emerging trends in wide band gap semiconductors (SiC and GaN) technology for power devices

Mapping the Density of Scattering Centers Limiting the Electron Mean Free Path in Graphene

Challenges for energy efficient wide band gap semiconductor power devices

Free-Standing Copper(II) Oxide Nanotube Arrays through an MOCVD Template Process

Localized electrical characterization of the giant permittivity effect in CaCu3Ti4O12 ceramics