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Metamaterials are broadly defined as artificial, electromagnetically homogeneous structures that exhibit unusual physical properties that are not present in nature. They possess extraordinary capabilities to bend electromagnetic waves. Their size, shape and composition can be engineered to modify their characteristics, such as iridescence, color shift, absorbance at different wavelengths, etc., and harness them as biosensors. Metamaterial construction from biological sources such as carbohydrates, proteins and nucleic acids represents a low-cost alternative, rendering high quantities and yields. In addition, the malleability of these biomaterials makes it possible to fabricate an endless number of structured materials such as composited nanoparticles, biofilms, nanofibers, quantum dots, and many others, with very specific, invaluable and tremendously useful optical characteristics. The intrinsic characteristics observed in biomaterials make them suitable for biomedical applications. This review addresses the optical characteristics of metamaterials obtained from the major macromolecules found in nature: carbohydrates, proteins and DNA, highlighting their biosensor field use, and pointing out their physical properties and production paths. [ABSTRACT FROM AUTHOR]

Metamaterials are broadly defined as artificial, electromagnetically homogeneous structures that exhibit unusual physical properties that are not present in nature. They possess extraordinary capabilities to bend electromagnetic waves. Their size, shape and composition can be engineered to modify their characteristics, such as iridescence, color shift, absorbance at different wavelengths, etc., and harness them as biosensors. Metamaterial construction from biological sources such as carbohydrates, proteins and nucleic acids represents a low-cost alternative, rendering high quantities and yields. In addition, the malleability of these biomaterials makes it possible to fabricate an endless number of structured materials such as composited nanoparticles, biofilms, nanofibers, quantum dots, and many others, with very specific, invaluable and tremendously useful optical characteristics. The intrinsic characteristics observed in biomaterials make them suitable for biomedical applications. This review addresses the optical characteristics of metamaterials obtained from the major macromolecules found in nature: carbohydrates, proteins and DNA, highlighting their biosensor field use, and pointing out their physical properties and production paths.

This letter reports the fabrication of high performance polycrystalline InGaSnO (IGTO) thin-film transistors (TFTs) at a low temperature of 400 °C. The microstructure of IGTO films was analyzed using X-ray diffraction and high-resolution transmission electron microscopy. The fabricated polycrystalline IGTO TFTs exhibited an unexpected high mobility of 116.5 cm2/Vs, threshold voltage of 0.47 V, low subthreshold gate swing of 134 mV/decade, and ${I}_{ON/OFF}$ ratio of $> 1\times 10^{9}$. Moreover, the stable behavior against external gate bias stress was observed for crystalline IGTO TFTs, which was attributed to the high degree of metal-oxygen lattice ordering. [ABSTRACT FROM AUTHOR]

Strained oxygen-deficient perovskite SrFeO $_{3 - \delta }$ (SFO) films have been epitaxially grown by pulsed laser deposition (PLD) on SrTiO3 (STO) (001) substrates. Oxygen deficiency of the films in comparison with the stoichiometric perovskite SrFeO3 is manifested in the increased lattice parameter, $c = 3.97$ Å, the decreased mass density, $\rho = 4.825$ gcm−3, and the presence of Fe3+ cations. The SFO perovskite structure is monoclinically distorted with an increase of the film thickness, resulting in the reduction of the total magnetic moment. A wasp-waisted hysteresis loop and a negative exchange bias are observed for the 69 nm thick film due to the possible magnetic sublayers arising from a proper monoclinically distorted surface layer and a substrate-locked core layer. [ABSTRACT FROM AUTHOR]

A Talbot effect is observed in a Kagome lattice photonic crystal (KPC) at the Dirac-like cone. The Dirac-like cone and Dirac-like point are achieved at the center of the Brillouin zone (BZ) with triply degenerate bands with two linear bands and one flat band intersecting the cone at the same frequency. Using band-structure calculations, it is shown that the Dirac-like cone is formed in a relatively high-frequency region and composed of interchangeable but opposite cones which are formed by two linear dispersion curves of the KPC in the vicinity of the Dirac-like point. Near the point of degeneracy, in addition to Talbot effect, unique wave propagation phenomena such as defect-insensitive propagation characteristics and cloaking of objects are observed. [ABSTRACT FROM AUTHOR]

Structures of Coulomb crystals were analyzed in cylindrical discharge plasmas under gravity and microgravity by using an apparatus similar to the PK-4 on the International Space Station (ISS). Under gravity, layers of cylindrical dust clouds were found to locally form the lattices of the face-centered orthorhombic (FCO) structure, which is a deformation from the face-centered-cubic structure. We also observed that the average density increases with the size of dust clouds. Under microgravity, the structure could be regarded as an assembly of linear chains along the cylinder axes. At the same time, the interparticle distance and the plasma parameters measured by a double-probe method indicated that the structure was formed not only from the wake potential but also from mutual interactions between dust particles in neighboring chains. [ABSTRACT FROM AUTHOR]

The proposed method is based on the first principles of density functional theory to calculate the electronic structure of SnO2 and rare-earth elements-doped SnO2. The energy band and density of state of undoped SnO2 and SnO2-X (La, Ce, and Y) are calculated and apply Origin Pro 9.0 for quantitative calculation. Conducting experimental verification of AgSnO2 and AgSnO2-X (La, Ce, and Y), contact materials prepared by sol–gel and powder metallurgy methods and the contact resistance and arcing energy are measured by the simulated electrical contact test. In the simulation results of SnO2-X (La, Ce, and Y), the relative electrical conductivity of Y-doped SnO2 is the largest. In the experimental results, the minimum and maximum values and the range of the variation of the arc energy and contact resistance after AgSnO2-X (La, Ce, and Y) are reduced. The effect of Y-doped AgSnO2 is more obvious and has the highest density. The final simulation and experimental results can be well matched. The best electrical performance is Y-doped AgSnO2, followed by La-doped AgSnO2. [ABSTRACT FROM AUTHOR]

Mn3O4 nanoparticles with particle sizes of 7.8, 11.4, and 18.3 nm were synthesized in the pores of mesoporous silica, and their crystal structure and magnetic properties were investigated. The powder X-ray diffractions at room temperature indicated that the crystal structural symmetry was the same as that for bulk crystal, and the lattice constants deviated from those for bulk crystal, which depended on the particle size. In addition, compared with the bulk crystal, the Jahn–Teller distortion for the nanoparticles was suppressed and decreased with decreasing the particle size. The coercive field for 7.8 nm was rather smaller than those for 11.4 and 18.3 nm. The nanoparticles with 11.4 and 18.3 nm exhibited pronounced three kinds of magnetic transition temperatures, whereas the susceptibility for 7.8 nm indicated the existence of two transition temperatures. These experimental results suggested that the Mn3O4 nanoparticles have a strong correlation between crystallographic structure and magnetic property, and the characteristic magnetic size effects are attributed to the reduction of Jahn–Teller distortion. [ABSTRACT FROM AUTHOR]

The interplay among charge, spin, and orbital degrees of freedom in electrons gives rise to a variety of electronic states and topological properties. We here report our theoretical study of the instability toward multiple-Q magnetic ordering with noncollinear and noncoplanar spin textures in spin–orbit coupled metals. By simulated annealing for an effective spin model, which incorporates the spin–charge coupling and the Rashba spin–orbit coupling, we elucidate the phase diagram while changing the anisotropic exchange interactions, the antisymmetric Dzyaloshinskii–Moriya interaction, and the external magnetic field. We show that the model exhibits a plethora of multiple-Q states including Néel-type and Bloch-type vortex crystals. Our systematic analysis will provide a guide for complex spin textures observed in spin–orbit coupled metals, such as monolayer metals on substrates. [ABSTRACT FROM AUTHOR]

The field of perovskite heterostructures (PHSs) has seen considerable progress in recent years. Particularly, these structures have attracted interest because of their remarkably efficient photovoltaic and optoelectronic properties. This paper reviews a wide range of potential applications of PHSs. The review begins by introducing and summarizing the fundamental theory of PHSs and pays special attention to their basic properties. The optical and electronic properties of PHSs are subsequently described in detail, with an emphasis on the approaches that were followed to discover these properties. The crystal structures of heterostructures are examined by observing representative studies of the perovskite crystal. Recent progress in research involving PHSs demonstrates the important role of the optoelectronic devices. [ABSTRACT FROM AUTHOR]

Mechanical behaviors and especially the strain-rate responses at the nanoscales of low melting temperature metals, such as indium, have not been studied much. Indium is one of the key materials or alloy components in advanced microelectronics and the nanotechnology industry, and understanding their mechanical behaviors at nanoscales becomes increasingly important to ensure lifetime reliability of their applications in novel nanoscale devices or advanced systems (for packaging at the nanoscales, for instance). Synchrotron X-ray microdiffraction has been utilized to examine defect structures of nanoscale materials as well as their strain-rate responses. Nanoscale or advanced microelectronics packaging, for instance, require acceptable levels of drop test results. For these low melting temperature materials especially, this technique offers a unique advantage as conventional methods such as transmission electron microscope and EBSD will expose the structure to high-energy electron beams that may significantly alter the microstructure and defect structure during analysis. Using this approach, we found interesting differences in term of X-ray peak broadening after deformation with different strain rates, which could indicate differences in plasticity mechanisms in the submicron pillars of indium, which could be important for their applications in nanodevices. Understanding these differences could lead to better control of mechanical properties of low melting temperature metals at the nanoscales and, thus, have important implications for nanodevice reliability. [ABSTRACT FROM AUTHOR]

Effects of stress and strain in FePt thin film on $L 1_{0}$ ordering are investigated by employing single-crystal substrate of which lattice mismatch with FePt crystal is varied in a range from −10.3% to +0.8% for 10 nm thick FePt thin film. Thin films are prepared under different conditions; direct deposition at 600 °C, two-step process consisting of 200 °C deposition followed by 600 °C annealing, and the two-step process with MgO cap layer formed on top of the FePt layer at 200 °C. Formation of $L 1_{0}$ -FePt(001) crystal and $L 1_{0}$ ordering is enhanced on a substrate with larger negative lattice mismatch, though the lattice mismatch with substrate is decreased greatly by introduction of misfit dislocation and by lattice bending in FePt material. The lateral in-plane strain in FePt material associated with several factors: substrate material, film morphology, and cap layer has given a strong influence in $L 1_{0}$ -ordered phase formation in FePt thin film. [ABSTRACT FROM AUTHOR]

(K,Na)NbO3-based ferroelectric single crystals have recently undergone a substantial development, resulting in improved crystal quality and large piezoelectric coefficients, exceeding 700 pC/N, over a broad temperature range. However, further development necessitates a detailed understanding of the mechanisms defining the domain structure and its temperature evolution. This paper presents the investigation into the crystallographic structure and domain configurations of a (K,Na,Li)(Ta,Nb)O3 single crystal over a broad temperature range. The crystal was grown by the submerged-seed solution growth technique and investigated using in situ transmission electron microscopy, X-ray diffraction, dielectric measurements, and polarized light microscopy. The lattice distortion, structural phase transitions, and domain configurations are reported. A transition from the lamellar orthorhombic to the rectangular tetragonal domain structure is observed upon heating. Moreover, the milky optical appearance of the crystal was investigated and found to result from the presence of regions with different domain configurations and domain sizes. The formation of these regions is related to the growth defects, which govern the domain formation when cooling below the Curie temperature. [ABSTRACT FROM AUTHOR]

Recently, an interesting superconductivity of the transition temperatures range from 7.2 to 43 K and then to 123 K in K-doped ${p}$ -terphenyl was reported, which attracts much attention. In this paper, to identify the superconducting phase from chemical component, we have investigated the crystal structures and electronic and magnetic properties in the cases of K-doped biphenyl and ${p}$ -terphenyl based on the first-principles calculations. We found that the change of doping concentration results in a series of magnetic transitions. Pristine biphenyl and ${p}$ -terphenyl are both nonmagnetic (NM) semiconductors. Doping one K atom for each organic molecule, the system exhibits the antiferromagnetism. With increasing the doping concentration of K atoms, however, the spin ordering disappears and the compound behaviors as the NM metal. Thus, we suggest that the superconducting phases observed experimentally are corresponding to the highly doping levels, which will deepen the understanding of the superconductivity of aromatic hydrocarbons. [ABSTRACT FROM AUTHOR]

In III–nitride nanowire (NW)-based solar cells, efficient utilization of polarization charges is essential in order to achieve high performance. In this paper, the polarization behavior of a GaN/InxGa1–xN/GaN core/shell/shell triangular NW solar cell with {000-1} or {0001} as one of the facets is intensively studied through numerical simulations. An analysis of defect density, strain profile, and polarization charges at different facets of NWs with different “In” compositions is considered carefully. It is observed that an NW solar cell with a N-polar {000-1} facet is good enough to enhance carrier collection efficiency as compared with Ga-polar {0001} facet. This numerical study provides an innovative aspect of implementation of fundamental device physics with respect to recent growth techniques in order to realize the application of III–nitride NWs toward photovoltaic applications. The effect of an InxGa1–xN layer with different “In” compositions in all crystallographic orientations of NW solar cells is also discussed. It is interesting to observe that a maximum conversion efficiency of ~3.85% with the 93.38% fill factor is achieved from an n-GaN/i-InxGa1–xN/p-GaN nanowire solar cell considering 10% of “In” content under one Sun AM1.5 illumination. [ABSTRACT FROM PUBLISHER]

In this paper, the Ga2Se3 crystals are used to design a Yb/Ga2Se3/C Schottky barrier. The device structure is investigated by the X-ray diffraction technique, which reveals a monoclinic-face-centered cubic interfacing type of structure. The barrier is studied by means of current ( $I$ )–voltage ( V$ ) characteristics in the dark and under light through photoexcitation from tungsten lamp and from the He–Ne laser. In addition, the impedance spectroscopy of these devices is studied in the frequency range of 10–1400 MHz. The photoexcited I-V$ curve analysis allowed investigating the biasing voltage, illumination power, and energy effects on the diode physical parameters, which are presented by the rectification ratio, the Schottky barrier height, the ideality factor, the series resistance, the photosensitivity, the responsivity, and the external quantum efficiency (EQE). While a maximum photosensitivity of 42 was observed for laser excitation with a wavelength of 632 nm at a reverse bias of 4.4 V, the EQE reached value of 1652% at 19.0 V. On the other hand, the ac current conduction analysis of the electrical conductivity, which was determined from the impedance spectral analysis, indicated that the ac signal processing through the Yb/Ga2Se3/C samples is due to the correlated hopping conduction through localized states of Fermi density of . The high-and biasing-dependent EQE% nominates the Yb/Ga2Se3/C as a tunable optoelectronic device. [ABSTRACT FROM PUBLISHER]

The uniformity of the lattice spacing of silicon crystals was evaluated by the self-referenced lattice comparator with a resolution of 3 × 10−9. Lattice strain measurements were performed for the sample 10.5 cut from 28Si ingot (Avo28), which was used to determine the Avogadro constant. The mapping results for samples 4.R1, XINT, and 9.R1 performed in the previous works have also been re-evaluated. The 4.R1 in the seed side of the ingot and the XINT in the middle of the ingot have small distribution of lattice spacing. The standard deviations of the lattice spacing distribution for the 4.R1 and XINT were 4.8 × 10−9 and 5.5 ×10−9, respectively. In contrast, the 9.R1 and the 10.5 samples cut from the tail side of the ingot have a larger distribution of lattice spacing. These lattice spacing distributions in the ingot are consistent with the impurity distribution in the ingot. [ABSTRACT FROM AUTHOR]

In recent times, the neodymium-doped gadolinium vanadate (Nd:GdVO4) crystal has attracted significant attention as one of the most valuable functional materials, but its lattice structure can be easily modified in an irradiation environment, which determines its related optical properties and affects the performance of devices based on the Nd:GdVO4 crystal. The near-surface lattice structure change and damage are studied through the displacement per atom (dpa), X-Ray diffraction, hardness and elastic (Young's) modulus, and micro-Raman spectroscopy techniques. We discover that the intensity and peak position of micro-Raman have obvious changes between waveguide and substrate region in Nd:GdVO4 crystal. The related optical properties induced by the structural changes, including the absorption bands and refractive index profiles, are investigated. A new absorption peak was observed after irradiation of the Nd:GdVO4 crystals by C3+ ions. Thus, waveguide optical-coupling techniques identified that the ion- irradiated Nd:GdVO4 crystal can support single-mode or multimode propagation at 633 nm. The fabricated waveguide structures emerge as promising candidate for photonic design and integrated optical devices, which will have a huge application prospect in multimedia and internet. [ABSTRACT FROM PUBLISHER]

In this letter, we report a novel approach in demultiplexer design by performing wavelength separation in hetero photonic crystal (HPC) with an oblique boundary. First step, demultiplexing action is considered like ordinary demultiplexers using wavelength dispersion in photonic crystals. Contrary to ordinary demultiplexers, the oblique boundary in HPC causes components of Bloch wave-vectors of different wavelengths not to be equal in the second step. This change in Bloch wave-vector results in ultra-high separation angles for incident wavelengths. A beam divergence of 133° is obtained for an input range from \lambda 1= 1521 to \lambda 4= 1550 nm. [ABSTRACT FROM PUBLISHER]

Recently, negative-capacitance FETs (NCFETs) have been proposed to reduce subthreshold slope and help continue supply-voltage scaling alongside channel-length scaling. We investigate the high-frequency switching behavior of NCFETs using the Landau–Khalatnikov equation to model ferroelectric materials. Multidomain interactions in the ferroelectric are considered, resulting in strong agreement with experimental measurements. Operation of NCFETs at gigahertz frequencies is investigated with this experimentally validated multidomain model. We find that the effectiveness of the voltage amplification in NCFETs is strongly dependent on the viscosity coefficient $\rho $ of the ferroelectric, and that a low \rho $ ( <0.1~\Omega \cdot \text {m} ) is required for the operation at the high gigahertz frequencies. [ABSTRACT FROM PUBLISHER]

Deep-level defects are usually considered undesirable in semiconductors as they typically interfere with the performance of present-day electronic and optoelectronic devices. However, the electronic spin states of certain atomic-scale defects have recently been shown to be promising quantum bits for quantum information processing as well as exquisite nanoscale sensors due to their local environmental sensitivity. In this review, we will discuss recent advances in quantum control protocols of several of these spin defects, the negatively charged nitrogen-vacancy (NV ^-) center in diamond and a variety of forms of the neutral divacancy (\textVV^0) complex in silicon carbide (SiC). These defects exhibit a spin-triplet ground state that can be controlled through a variety of techniques, several of which allow for room temperature operation. Microwave control has enabled sophisticated decoupling schemes to extend coherence times as well as nanoscale sensing of temperature along with magnetic and electric fields. On the other hand, photonic control of these spin states has provided initial steps toward integration into quantum networks, including entanglement, quantum state teleportation, and all-optical control. Electrical and mechanical control also suggest pathways to develop quantum transducers and quantum hybrid systems. The versatility of the control mechanisms demonstrated should facilitate the development of quantum technologies based on these spin defects. [ABSTRACT FROM PUBLISHER]

The paper is dedicated to development of the novel scintillating screens based on single crystalline films (SCF) of Ce doped Lu3 - x{Tb_x}{Al5 - y}{Ga_y}{O12} multicomponent garnets at x = 2 - 3 and y = 0 - 2.5 onto Y_3Al_5O12 (YAG) and Gd_3Al2.5{Ga2.5}{O12} (GAGG) substrates using the liquid phase epitaxy (LPE) method. We report the optimized content and high scintillation figure of merit of SCF of these garnets grown by the LPE method with using PbO based flux. Namely, the Tb_3Al2.5{Ga2.5}{O12}:Ce SCFs possess the highest values of light yield (LY) compared to all earlier investigated SCF samples, with their LY exceeding by 2.35 and 1.15 times the LY values for YAG:Ce and LuAG:Ce SCF scintillators, respectively. The SCFs of the mentioned compounds show very lower thermoluminescence in the above room temperature range and relatively fast scintillation decay. [ABSTRACT FROM AUTHOR]

We present a numerical investigation of the magnonic band structure of spin waves (SWs) in a novel magnonic crystal consisting of a waveguide with a linear array of periodically spaced skyrmions created along its center by micromagnetic simulations. The interfacial Dzyaloshinskii–Moriya interaction (DMI) induced the presence of skyrmions causes a periodical magnetization modulation of the waveguide, which can be dynamically controlled by changing either the strength of the external magnetic field or the period of the skyrmion lattice. The diameters of the skyrmions are highly dependent on the strength of the applied magnetic field, and they can exist for a wide magnetic field range depending on the density of the DMI. The calculated dispersion relation of SWs in the proposed skyrmion magnonic crystal, frequency versus wave vector, exhibits a periodical property, which is the characteristic feature of the band structure of conventional magnonic crystals. Similarly, the calculated magnonic spectra exhibits allowed frequency band and forbidden frequency bandgaps. Our findings could stimulate further exploration on multiple functionalities provided by magnonic crystals based on periodic skyrmion lattices. [ABSTRACT FROM AUTHOR]

Resonant body transistors (RBTs) are solid state, actively sensed microelectromechanical systems (MEMS) resonators that can be implemented in commercial CMOS technologies. With small footprint, high- $Q$ , and scalability to gigahertz frequencies, they form basic building blocks for radio frequency (RF) front-ends and timing applications. Toward the goal of seamless CMOS integration, this paper presents the design and implementation of phononic crystals (PnCs) in the back-end-of-line (BEOL) of commercial CMOS technologies with bandgaps in the gigahertz frequencies to be used for enhanced acoustical confinement in CMOS-RBTs. Lithographically defined PnC dimensions allow for bandgap engineering, providing flexibility in resonator design, and allowing for multiple frequencies on a single chip. The theoretical basis for analyzing generic PnCs is presented, with focus on the special case of implementing PnCs in CMOS BEOL layers. The effect of CMOS process variations on the performance of such PnCs is also considered. The analysis presented in this paper establishes a methodology for assessing different CMOS technologies for the integration of unreleased CMOS-MEMS resonators. This paper also discusses the importance of uniformity of the acoustical cavity in the nonresonant dimension and its effect on overall resonator performance. A PnC implementation in IBM 32-nm silicon on insulator (SOI) BEOL layers is demonstrated to achieve 85% fractional-bandgap \sim 4.5$ -GHz frequency. With better energy confinement, the proposed CMOS-RBTs achieve a quality factor Q$ of 252, which corresponds to 8\times . This paper concludes with a discussion of the properties required of a CMOS technology for high performance RBT implementation. [2014-0364] [ABSTRACT FROM PUBLISHER]

Carrier energy and momentum engineering design concepts have been utilized to realize higher intensity, up to 200 nW. \mu \textm -2 in p+nn+ silicon avalanche-based LEDs in a silicon 0.35- \mu \textm RF bipolar process. The spectral range is from 600- to 850-nm wavelength region. Best performance are up to 600-nW vertical emission in a 3- \mu \textm square active area at 10 V and 1 mA (200 nW.um-2). The achieved emitted optical intensity is about 100 fold better as compared with other published work for nearest related devices. In particular, evidence has been obtained that light emission in silicon are strongly related to scattering mechanisms in a high density n+ dopant matrix of phosphorous atoms in silicon that has been exposed to successive thermal cycles, as well on the optimization of the carrier energy and momentum distributions during such interactions. [ABSTRACT FROM AUTHOR]

The homogeneity of the lattice spacing of silicon single crystals was investigated by a self-referenced lattice comparator. Strain measurements were performed on single crystals from an ^28 Si ingot (Avo28), which was used to determine the Avogadro constant. A swirl pattern was observed for sample 9.R1 cut from the tail side of the Avo28 ingot. The lattice spacing distribution of seed-side sample 4.R1 was smooth and homogeneous. The lattice spacing distribution was larger for the sample with higher impurities of carbon and oxygen. [ABSTRACT FROM PUBLISHER]

We report piezoelectric materials composed of charge-compensated co-doped (Mg, β)ξAl1?xN (β = Zr or Hf) thin films. The effect of the dopant element into AlN on the crystal structure, and piezoelectric properties of co-doped AlN was determined on the basis of a first-principles calculation, and the theoretical piezoelectric properties were confirmed by experimentally depositing thin films of magnesium (Mg) and zirconium (Zr) co-doped AlN (Mg-Zr-doped AlN). The Mg-Zrdoped AlN thin films were prepared on Si (100) substrates by using a triple-radio-frequency magnetron reactive co-sputtering system. The crystal structures and piezoelectric coefficients (d33) were investigated as a function of the concentrations, which were measured by X-ray diffraction and a piezometer. The results show that the d33 of Mg-Zr-doped AlN at total Mg and Zr concentrations (both expressed as β) of 0.35 was 280% larger than that of pure AlN. The experimentally measured parameter of the crystal structure and d33 of Mg-Zr-doped AlN (plotted as functions of total Mg and Zr concentrations) were in very close agreement with the corresponding values obtained by the first-principle calculations. Thin film bulk acoustic wave resonators (FBAR) employing (Mg,Zr)0.13Al0.87N and (Mg, Hf)0.13 Al0.87N as a piezoelectric thin film were fabricated, and their resonant characteristics were evaluated. The measured electromechanical coupling coefficient increased from 7.1% for pure AlN to 8.5% for Mg-Zr-doped AlN and 10.0% for Mg- Hf-doped AlN. These results indicate that co-doped (Mg, β)ξ Al1?ξN (β = Zr or Hf) films have potential as piezoelectric thin films for wideband RF applications. [ABSTRACT FROM PUBLISHER]

We simulate spin wave (SW) dynamics in a thin film antidot magnonic crystal (MC) with a ring defect. An external magnetic field is applied perpendicular to the film plane in a forward volume configuration. We initially use the plane wave method to obtain the SW band diagram for the antidot MC structure (without the defect), which gives us an idea of modes that are trapped in the crystal. We then use finite element micromagnetic simulations to study the SW propagation in the MC with the ring defect. The power spectral density of the magnetization at the top of the ring shows peaks that fall within the band gap of the MC. The SW energy in other frequency components is dissipated in the MC and do not reach the other end of the ring. [ABSTRACT FROM AUTHOR]

The dc magnetization and ac spin susceptibility measurement results of MnxSi single crystals with x \(\boldsymbol \approx ~0.96\) –1 are reported. Magnetic phase diagrams for MnxSi of different Mn deficiency levels are mapped and compared. We provide strong evidence that the existence of manganese deficiency is common in the MnSi single crystals due to the high Mn vapor loss during growth, and the Mn deficiencies could be used as pinning centers to stabilize the Skyrmion phase within the magnetic field–temperature phase space. [ABSTRACT FROM AUTHOR]

Abstract?The nature of intrinsic and impurity point defects in lead zirconate titanate (PZT) ceramics has been explored. Using electron paramagnetic resonance (EPR), nuclear magnetic resonance (NMR), and X-ray photoelectron spectroscopy (XPS) methods, several impurity sites have been identified in the materials, including the Fe3+–oxygen vacancy (VO) complex and Pb ions. Both of these centers are incorporated into the PZT lattice. The Fe3+%#x2013;V paramagnetic complex serves as a sensitive probe of the local crystal field in the ceramic; the symmetry of this defect roughly correlates with PZT phase diagram as the composition is varied from PbTiO3 to PbZrO3. NMR spectra 207Pb in PbTiO3, PbZrO3, and PZT with iron content from 0 to 0.4 wt% showed that increasing the iron concentration leads to a distortion of the crystal structure and to improvement of the electrophysical parameters of the piezoceramics. This is due to the formation of a phase which has a higher symmetry, but at high concentrations of iron (>0.4 wt%), it leads to sharp degradation of electrophysical parameters. [ABSTRACT FROM PUBLISHER]

This paper reports the crystal structures and piezoelectric properties of Mg and Zr co-doped AlN (MgZrdoped AlN) thin films. MgZr-doped AlN thin films on Si (100) substrates were fabricated by using a radio-frequency magnetron reactive cosputtering system. The relations between dopant concentration and the crystal structures measured by X-ray diffraction, transmission electron microscopy, and the piezoelectric constant d33 measured with a piezometer were investigated. Up to total Mg and Zr concentrations of 34.8 at%, the MgZr-doped AlN films maintained the c-axis-oriented wurtzite structure and were likely formed by substituting Mg and Zr atoms into Al atom sites. The d33 of the MgZr-doped AlN with a total Mg and Zr concentration (Mg + Zr) of 34.8 at% was about three times that of pure AlN. The experimental results on the relation between total Mg and Zr concentration and the crystal structure and the d33 were in close agreement with the results of first-principles calculations. Finally, thin film bulk acoustic wave resonators (FBARs) that used MgZr-doped AlN as a piezoelectric thin film were fabricated and compared with the AlN-based FBAR. A total Mg and Zr concentration of 13 at% was found to improve the electromechanical coupling coefficient of AlN from 7.1% (for pure AlN) to 8.5%. The results from this study suggest that the MgZr-doped AlN films have potential as piezoelectric thin films for wideband and high-frequency RF applications. [ABSTRACT FROM AUTHOR]

Green-light nanocolumn light emitting diodes (LEDs) consisting of triangular-lattice uniform arrays of InGaN-based nanocolumns with lattice constants of 245-350 nm were fabricated with TiO2 mask selective-area growth by RF-plasma-assisted molecular beam epitaxy. The built-in core/shell structure of InGaN/GaN multiple quantum wells was self-assembled, confining carriers in the core of the nanocolumns. The characteristics of the nanocolumn LEDs were evaluated at room temperature under dc current injection in the range from 4.5 to 450 A/cm2. The emission wavelengths were 515 to 550 nm, and small current-induced spectral blueshifts of 2-11 nm were observed. The linewidth narrowing at a low current density was very small for the nanocolumn LEDs, in which nanocolumns with the same size were homogeneously arranged. The sidewalls of the nanocolumns were passivated by the deposition of Al2O3, contributing to the elimination of current leakage paths. The external quantum efficiency was improved with the passivation. Radiation beam angular profiles of the nanocolumn LEDs were evaluated and directional beam radiation was observed at specific wavelengths, which was attributed to the photonic band edge of the periodic nanocolumn arrangement. [ABSTRACT FROM AUTHOR]

New single crystals of Ce-doped Cs2NaGdCl6 are investigated under x-ray and \gamma-ray excitation. These scintillation crystals are grown by two zone vertical Bridgman technique and belong to elpasolite crystal family. Energy resolution, scintillation light yield, non-proportionality, energy resolution as a function of \gamma-rays energies and scintillation decay time measurements are presented. Ce^3+-related x-ray excited emission is observed between 360 and 450 nm wavelength region at room temperature. At higher Ce-concentration both self-trapped exciton (STE) and Gd^3+ emissions are disappeared and enhance Ce^3+ emission. Under 662 keV \gamma-rays excitation, Cs2NaGdCl6 shows an energy resolution of 5.2%, (FWHM) at 1% Ce-concentration. Best energy resolution of 4.8% (FWHM) is obtained for 10% Ce-concentration. No significant improvement is observed in the energy resolution of Cs2NaGdCl6 with the increase of Ce-concentration. The highest light yield of about 21,000 ph/MeV is obtained for 10% Ce-doped crystal. At room temperature three decay time components are found under \gamma-ray excitation for all Ce-doped samples. This material is highly hygroscopic. [ABSTRACT FROM PUBLISHER]

Transparent cerium doped lutetium aluminum garnet (Ce:LuAG) ceramic scintillantors with different Ce^3 + concentrations were densified successfully from synthetical nanosized Ce:LuAG powders using co-precipitation method. It was found that the 0.5 mol% Ce: LuAG ceramic exhibited the highest luminescent emission intensity under synchrotron radiation excitation which could be divided into two components centered at 505 and 540 nm under low temperature (50–150 K) conditions originated from the 5\d^1 excited level (^1D) to the 4f ground state of Ce^3 + (^2F5 / 2; ^2F7 / 2). The quantum efficiency (QE) of the optimized Ce:LuAG ceramic could reach 66.3% under UV excitation of 345 nm. Typical absorption at 170 nm related to possible LuAl^3 + antisite defect (AD) was observed both in Ce^3 + doped and undoped LuAG ceramics which formed electron traps disturbing the energy transfer from host lattice to Ce^3 + centers, leading to a slow decay component of 109.4 ns in the 0.5 mol% Ce:LuAG transparent ceramic under ^137Cs (662 keV) irradiation. [ABSTRACT FROM PUBLISHER]