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The c-axis-aligned crystalline (CAAC) rare earth gadolinium doped aluminum-zinc-oxide (Gd-AZO) thin films sputtered at room temperature are investigated in this work. It is found that the polycrystalline AZO is restructured into CAAC Gd-AZO through gadolinium doping. The X-ray diffraction spectrum and high-resolution transmission electron microscopy images indicate the (002) crystalline orientation of the local Gd-AZO grains. The film-formation mechanism of room-temperature sputtered CAAC Gd-AZO thin films is analyzed. Bottom gate oxide thin film transistors with a Gd-AZO active layer are fabricated by low temperature processes. The devices show preferable electrical properties, such as good I-V characteristics, high uniformity, and excellent bias stress stability.

Coupled magnetic–mechanical–electric effects in a composite with ferromagnetic rare-earth–iron alloys (e.g., Tb1−xDyxFe2) filled in ferroelectric polymers [e.g, poly(vinylidene-fluoride–trifluoroethylene) copolymer] are studied by using the Green’s function technique. Numerical results suggest a possible giant linear magnetoelectric effect in the ferroic polymer–matrix composite, which is markedly larger than that in the best-known magnetoelectric materials. In addition, the mechanically flexible composite exhibits large magnetostriction. The present results may stimulate further interest in the area of magnetoelectric materials for technological applications.

Surface wrinkling of animal mucosas is crucial for the biological functions of some tissues, and the change in their surface patterns is a phenotypic characteristic of certain diseases. Here we develop a biomechanical model to study the relationship between morphogenesis and volumetric growth, either physiological or pathological, of mucosas. Theoretical analysis and numerical simulations are performed to unravel the critical characteristics of mucosal wrinkling in a spherical antrum. It is shown that the thicknesses and elastic moduli of mucosal and submucosal layers dictate the surface buckling morphology. The results hold clinical relevance for such diseases as inflammation and gastritis.

The authors demonstrate superior crystal quality of a-plane GaN grown on r-plane sapphire substrate based on the flow modulation epitaxy (FME) technique, in which the Ga atom supply is alternatively switched on and off with continuous nitrogen supply. With the FME technique, a high growth rate of 2.3μm∕h can still be achieved. With or without epitaxial lateral overgrowth (ELOG), either c- or m-mosaic condition is significantly improved in the samples of using FME. With ELOG, the surface roughness can be reduced from 1.58to0.647nm in an area of 10×10μm2 microns by using the FME technique. Based on the results of photoluminescence measurement, one can also conclude the better optical property of the FME-grown a-plane GaN thin films. Besides, it is shown that tensile strain is more relaxed in the FME samples.

Many natural and synthetic quasi-one-dimensional materials are of helical or twisting shape and understanding the physical mechanisms underlying the asymmetric shape is of both theoretical and technological significances. In this letter, we pointed out that anisotropic surface stresses present as a possible reason for the formation of some micro-/nanohelices. Using Gurtin’s theory of surface elasticity, we quantitatively investigated the twisting deformation of nanowires due to anisotropic surface stresses. The present model can also elucidate the formation of some other helical materials at micro- and nanoscales, e.g., twisting lamellae in polymer spherulites, spiraled bacteria, and flagella.

High-phase-purity zinc-blende (zb) InN thin film has been grown by plasma-assisted molecular-beam epitaxy on r -plane sapphire substrate pretreated with nitridation. X-ray diffraction analysis shows that the phase of the InN films changes from wurtzite (w) InN to a mixture of w-InN and zb-InN, to zb-InN with increasing nitridation time. High-resolution transmission electron microscopy reveals an ultrathin crystallized interlayer produced by substrate nitridation, which plays an important role in controlling the InN phase. Photoluminescence emission of zb-InN measured at 20 K shows a peak at a very low energy, 0.636 eV, and an absorption edge at ∼0.62 eV is observed at 2 K, which is the lowest bandgap reported to date among the III-nitride semiconductors. © 2008 American Institute of Physics.

Molecular dynamics simulations have been performed to study the mechanical properties and deformation mechanisms of the so-called super carbon tubes (SCTs), a recently developed network material made by conjoined single- or multiwalled carbon nanotubes. It is found that such SCTs exhibit some unusual mechanical properties distinctly different from individual carbon nanotubes. The rupture strain of SCTs reaches more than 30%, more than three times that of single-walled carbon nanotubes. This study suggests that SCTs might be used as advanced materials with extremely low mass density and high flexibility.

First-principles calculations on the electronic and magnetic properties of BiNiO3 reveal that the G-type antiferromagnetic structure with the insulating ground state is more stable than other possible configurations. The hybridization of Ni–O and Bi–O leads to the reduction of the spin magnetic moment to 1.67μB in comparison with the Ni2+ d8 configuration of 2μB. The band gap of the antiferromagnetic insulating ground state is predicted to be 0.68eV. The antiferromagnetic interaction induces the localized spins to be S=1 in the G-antiferromagnetic structure of BiNiO3.

The authors demonstrate the spectral redshift of the quantum wells (QWs) designated for green emission into the orange range in a light-emitting diode by adding a violet-emitting QW at the bottom in metal-organic chemical vapor deposition. An electroluminescence redshift of 53nm was obtained. The cathodoluminescence spectra indicated that the long-wavelength QWs close to the violet one were strongly influenced by this added QW and mainly emitted the orange photons. Those near the top were less affected. This influence is supposed to originate from the prestrained effect in the barrier layer right above the violet QW. Such a prestrained effect is expected to be more effective when the underlying QW is well shaped and the heterojunction strain is strong, like the case of the violet QW. This effect is weak between the high-indium QWs, in which the formation of indium-rich clusters releases the strain.

A model, where the interaction between adsorbates and the cantilever and that between the adsorbates themselves have been explicitly taken into account through Lennard-Jones potential, is developed to explain the adsorption-induced fundamental resonance frequency change of a cantilever. With the model, one can obtain results comparable to some experimental observations and predict results with implications for certain applications of resonant behavior of small-dimensioned cantilevers.