Dynamic Magnetic Properties of Ferroic Films,Multilayers, and Patterned Elements

Modification and control of material properties through careful manipulation of geometry on nano‐ and sub‐nanometer length scales is a cornerstone of modern materials science and technology. An exciting area in which these concepts have provided exceptional advances has been magnetoelectronics and nanomagnetism. Important scales in magnetic metals are conduction spin diffusion lengths and distances over which local moments correlate. Advanced techniques now allow for the creation of structures patterned on these length scales in three dimensions. The focus of this article is on magnetic structures whose dynamic properties can be strongly modified by ion bombardment and lithographic patterning. Examples are given of how microwave frequency properties can be tuned with external fields, how factors controlling magnetic switching can be controlled, and how manipulation of magnetic domain walls can be used to reveal new and surprising phenomena.     

Covalent functionalization of metal oxide and carbon nanostructures with polyoctasilsesquioxane (POSS) and their incorporation in polymer composites

Polyoctasilsesquioxane (POSS) has been employed to covalently functionalize nanostructures of TiO₂, ZnO and Fe₂O₃ as well as carbon nanotubes, nanodiamond and graphene to enable their dispersion in polar solvents. Covalent functionalization of these nanostructures with POSS has been established by electron microscopy, EDAX analysis and infrared spectroscopy. On heating the POSS-functionalized nanostructures, silica-coated nanostructures are obtained. POSS-functionalized nanoparticles of TiO₂, Fe₂O₃ and graphite were utilized to prepare polymer-nanostructure composites based on PVA and nylon-6,6.     

New Vanadium Oxide Nanostructures: Controlled Synthesis and Their Smart Electrical Switching Properties

Control over the different polymorphs of vanadium oxide that possess electrical switching properties is advancing rapidly as a result of the need to address energy‐efficiency issues; an example of which is the intelligent regulation of infrared light demonstrated by these polymorphs. Recent advances in the development of new vanadium oxide structures as well as their promising electrical switching properties are summarized here. Theoretical analysis and experimental results suggest that the presence of infinite vanadium ion chains in the crystal structure plays a decisive role in determining the electrical properties of vanadium oxides. The successful synthesis of new vanadium oxide materials and their nanostructures not only promotes a mechanistic understanding of the temperature‐driven electrical switching properties but also provides the right materials for constructing smart devices that can selectively filter out infrared light.     

‘Laser chemistry’ synthesis,physicochemical properties,and chemical processing of nanostructured carbon foams

Laser ablation of selected coordination complexes can lead to the production of metal-carbon hybrid materials, whose composition and structure can be tailored by suitably choosing the chemical composition of the irradiated targets. This ‘laser chemistry’ approach, initially applied by our group to the synthesis of P-containing nanostructured carbon foams (NCFs) from triphenylphosphine-based Au and Cu compounds, is broadened in this study to the production of other metal-NCFs and P-free NCFs. Thus, our results show that P-free coordination compounds and commercial organic precursors can act as efficient carbon source for the growth of NCFs. Physicochemical characterization reveals that NCFs are low-density mesoporous materials with relatively low specific surface areas and thermally stable in air up to around 600°C. Moreover, NCFs disperse well in a variety of solvents and can be successfully chemically processed to enable their handling and provide NCF-containing biocomposite fibers by a wet-chemical spinning process. These promising results may open new and interesting avenues toward the use of NCFs for technological applications.     

Size-dependent Fano Interaction in the Laser-etched Silicon Nanostructures

Photo-excitation and size-dependent Raman scattering studies on the silicon (Si) nanostructures (NSs) prepared by laser-induced etching are presented here. Asymmetric and red-shifted Raman line-shapes are observed due to photo-excited Fano interaction in the quantum confined nanoparticles. The Fano interaction is observed between photo-excited electronic transitions and discrete phonons in Si NSs. Photo-excited Fano studies on different Si NSs show that the Fano interaction is high for smaller size of Si NSs. Higher Fano interaction for smaller Si NSs is attributed to the enhanced interference between photo-excited electronic Raman scattering and phonon Raman scattering.     

Annealing textures of copper damascene interconnects for ultra-large-scale integration

The annealing textures of copper interconnects depend upon their deposition textures and geometries. The copper interconnects are subjected to tensile stresses even at room temperature, which in turn gives rise to strain energies. The stress distributions in interconnects are not homogeneous due to trenches, resulting in non-fiber-type textures after annealing. To better understand the formation of the non-fiber-type textures, the textures of specimens of 0.2–6 μm in trench width with 0.2 μm in space were measured, and the strain energy and stress distributions have been simulated. The simulation results indicate that strain energy density is highest at the upper corners of trench. Therefore, the grain growth rate at the upper corners is fastest, resulting in the {111}〈110〉 annealing texture. As the trench width increases, the influence of stresses in the trench increases, even though the strain energy density in the trench is relatively low. In this case the {111}〈112〉 component increases, even though the formation of the {111}〈110〉 orientation cannot be excluded.     

A Microbial‐Mineralization‐Inspired Approach for Synthesis of Manganese Oxide Nanostructures with Controlled Oxidation States and Morphologies

Manganese oxide nanostructures are synthesized by a route inspired by microbial mineralization in nature. The combination of organic molecules, which include antioxidizing and chelating agents, facilitates the parallel control of oxidation states and morphologies in an aqueous solution at room temperature. Divalent manganese hydroxide (Mn(OH)₂) is selectively obtained as a stable dried powder by using a combination of ascorbic acid as an antioxidizing agent and other organic molecules with the ability to chelate to manganese ions. The topotactic oxidation of the resultant Mn(OH)₂ leads to the selective formation of trivalent manganese oxyhydroxide (β‐MnOOH) and trivalent/tetravalent sodium manganese oxide (birnessite, Na_0.55Mn₂O₄·1.5H₂O). For microbial mineralization in nature, similar synthetic routes via intermediates have been proposed in earlier works. Therefore, these synthetic routes, which include in the present study the parallel control over oxidation states and morphologies of manganese oxides, can be regarded as new biomimetic routes for synthesis of transition metal oxide nanostructures. As a potential application, it is demonstrated that the resultant β‐MnOOH nanostructures perform as a cathode material for lithium ion batteries.