Materials Literature
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The effect of vacuum annealing on the thermal stability and phase transition of Ti 3 SiC 2 has been investigated by X‐ray diffraction (XRD), neutron diffraction, synchrotron radiation diffraction, and secondary ion mass spectroscopy (SIMS). In the presence of vacuum or a controlled atmosphere of low oxygen partial pre…
Lead-free piezoceramic potassium sodium niobate in its morphotropic composition was synthesized with abnormal grain growth. Ferroelectric domain patterns were imaged with piezoresponse force microscopy. Analysis of the domain structure at the morphotropic phase boundary revealed a coexistence of tetragonal and orthorh…
We demonstrate the use of subwavelength gratings etched into the facets of silicon-on-insulator ridge waveguides as a means of reducing facet reflectivity by the gradient-index effect. Reflectivities as low as 2.0% and 2.4% for the fundamental TE and TM modes, respectively, are demonstrated experimentally for light of…
Ternary twinned Zn2TiO4 spinel nanowires are formed by a solid-state reaction between Ti and ZnO from an amorphous Ti-coated ZnO core/shell nanowire structure. The ZnO nanowires are used as templates to spatially confine the formation of Zn2TiO4 nanowires. TEM investigations (see figure) reveal the nature of both the…
The magnetoresistance (MR) of Co/multilayer graphene/Co spin valve structures has been studied. A positive MR of up to 0.39% at 2K with switching at magnetic fields that are consistent with the magnetization orientations inferred from anisotropic MR data obtained for the Co contacts has been observed. The positive MR…
Abstract The polyaniline (PAni) is prepared electrochemically from an aqueous solution of aniline and HCl in a single compartment electrochemical cell. Different PAni samples obtained by varying monomer concentration, acid concentration, applied potential, reaction time, and reaction temperature are subjected to condu…
Growth kinetics of carbon nanofibers in a hydrocarbon plasma is studied. In addition to gas-phase and surface processes common to chemical vapor deposition, the model includes (unique to plasma-exposed catalyst surfaces) ion-induced dissociation of hydrocarbons, interaction of adsorbed species with incoming hydrogen a…
Bulk Ta 4 AlC 3 ceramic was prepared by an in situ reaction synthesis/hot‐pressing method using Ta, Al, and C powders as the starting materials. The lattice parameter and a new set of X‐ray diffraction data were obtained. The physical and mechanical properties of Ta 4 AlC 3 ceramic were investigated. Ta 4 AlC 3 is a g…
The authors report on the fabrication of a top-gate ZnO thin-film transistor (TFT) with a polymer dielectric/ferroelectric double-layer gate insulator that was formed on patterned ZnO through a sequential spin-casting process of 450-nm-thick poly-4-vinylphenol (PVP) and 200-nm-thick poly(vinylidene fluoride/trifluoroe…
We report the first analysis of the polarization and lattice dynamics in a metal/ferroelectric/metal nanolayer system by femtosecond x-ray diffraction. Two Bragg reflections provide information on the coupled dynamics of the two relevant phonon modes for ferroelectricity in perovskites, the tetragonal distortion and t…
The authors report a strong field effect observed at room temperature in epitaxially synthesized, as opposed to exfoliated, graphene. The graphene formed on the silicon face of a 4H silicon carbide substrate was photolithographically patterned into isolated active regions for the semimetal graphene-based transistors.…
A diffusion barrier layer was self-formed at the interface between Cu–Mn alloy and tetraethylorthosilicate oxide layers at 250–450°C. No interdiffusion occurred across the self-formed barrier layer during annealing at these temperatures up to 100h. The growth of the barrier layer obeyed a logarithmic law and depended…
The production of nanopatterns on the surfaces of targets irradiated by ion beams at low and intermediate energies has developed during the present decade to a salient degree of control over the main pattern features. However, there is still a wide experimental scatter in the type and relevance of various dynamic inte…
Phonons, i.e., quanta of lattice vibrations, manifest themselves practically in all electrical, thermal, optical, and noise phenomena in semiconductors and other material systems. Reduction of the size of electronic devices below the acoustic phonon mean free path creates a new situation for the phonons propagation an…
This letter reports on the metal-like conductivity down to 125K in highly crystalline transparent (⩾85% in the visible region) Al:ZnO films grown on sapphire and glass substrates by pulsed-laser deposition technique. Significantly different surface morphologies were found on both types of films. Temperature dependent…
In this paper, the mechanical properties of bulk single‐phase γ‐Y 2 Si 2 O 7 ceramic are reported. γ‐Y 2 Si 2 O 7 exhibits low shear modulus, excellent damage tolerance, and thus has a good machinability ready for metal working tools. To understand the underlying mechanism of machinability, drilling test, Hertzian con…
Simple calculations lead to a conclusion that there is an upper bound to the frequency at which magnetic refrigerators can operate, fmax∼2×102Hz. The principal factor limiting the operation frequency is a trade-off between thermal conductivity and viscous friction. The main events take place inside the magnetocaloric…
The classical theory of ion beam sputtering predicts the instability of a flat surface to uniform ion irradiation at any incidence angle. We relax the assumption of the classical theory that the average surface erosion rate is determined by a Gaussian response function representing the effect of the collision cascade…
Water molecules play a fundamental role in the physics of slow crack propagation in glasses. It is commonly understood that, during stress-corrosion, water molecules that move in the crack cavity effectively reduce the bond strength at the strained crack tip and, thus, support crack propagation. Yet the details of the…
We consider the conductivity sigma of graphene with negligible intervalley scattering at half filling. We derive the effective field theory, which, for the case of a potential disorder, is a symplectic-class sigma model including a topological term with theta=pi. As a consequence, the system is at a quantum critical p…