Open AccessReview
Novel Dilute Bismide, Epitaxy, Physical Properties and Device Application
Crystals 2017, 7(3), 63; doi:10.3390/cryst7030063 -
Abstract
Dilute bismide in which a small amount of bismuth is incorporated to host III-Vs is the least studied III-V compound semiconductor and has received steadily increasing attention since 2000. In this paper, we review theoretical predictions of physical properties of bismide alloys, epitaxial
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Dilute bismide in which a small amount of bismuth is incorporated to host III-Vs is the least studied III-V compound semiconductor and has received steadily increasing attention since 2000. In this paper, we review theoretical predictions of physical properties of bismide alloys, epitaxial growth of bismide thin films and nanostructures, surface, structural, electric, transport and optic properties of various binaries and bismide alloys, and device applications. Full article
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Open AccessEditorial
Quo Vadis Quasicrystals?
Crystals 2017, 7(3), 64; doi:10.3390/cryst7030064 -
Abstract
This Special Issue aims at gaining a deeper understanding on the relationship between the underlying structural order and the resulting physical properties in aperiodic systems, including quasicrystalline and related complex metallic alloys, photonic quasicrystals, and other structures exhibiting long-range aperiodic order. This Special
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This Special Issue aims at gaining a deeper understanding on the relationship between the underlying structural order and the resulting physical properties in aperiodic systems, including quasicrystalline and related complex metallic alloys, photonic quasicrystals, and other structures exhibiting long-range aperiodic order. This Special Issue contains 12 papers which highlight recent developments in quasiperiodic crystal structure, photonic quasicrystals and related optical devices, the intrinsic electrical, thermal, and mechanical properties of icosahedral and decagonal metallic alloys, and the nature of chemical bonding in intermetallic compounds, from a multidisciplinary perspective. In light of the results presented in the contributions collected in this Special Issue, we can confidently expect that new insights into the interdisciplinary science of quasicrystals will be gained in the years to come, providing a sharper picture of their structures and related physical properties, and spurring further progress in practical issues related to both materials engineering science and nanotechnology. Full article
Open AccessArticle
Temperature-Dependent Sellmeier Equations of IR Nonlinear Optical Crystal BaGa4Se7
Crystals 2017, 7(3), 62; doi:10.3390/cryst7030062 -
Abstract
The thermal dependent principal refractive indices of a new promising IR nonlinear optical crystal BaGa4Se7 at wavelengths of 0.546, 0.5806, 0.644, 0.7065, 1.530, 1.970, and 2.325μm were measured by using the vertical incidence method within the temperature range from 25
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The thermal dependent principal refractive indices of a new promising IR nonlinear optical crystal BaGa4Se7 at wavelengths of 0.546, 0.5806, 0.644, 0.7065, 1.530, 1.970, and 2.325μm were measured by using the vertical incidence method within the temperature range from 25 to 150 °C. We derived equations of thermal refractive index coefficients as a function of wavelength that could be used to calculate the principal thermal refractive indices at different wavelengths. The temperature-dependent Sellmeier equations were also obtained and used to calculate the phase matching angles for the optical parametric process of BaGa4Se7 crystal at different temperatures. Full article
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Open AccessArticle
Synthesis, Crystal Structure, Spectroscopic Properties, and DFT Studies of 7,9-Dibromobenzo[h]quinolin-10-ol
Crystals 2017, 7(2), 60; doi:10.3390/cryst7020060 -
Abstract
7,9-Dibromobenzo[h]quinolin-10-ol (1), a benzo[h]quinolin-10-ol derivative, was synthesized and characterized by single-crystal X-ray diffraction. The crystal belongs to monoclinic space group P21/n, with a = 3.9573(4), b = 18.0416(18), c = 15.8210(16) Å,
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7,9-Dibromobenzo[h]quinolin-10-ol (1), a benzo[h]quinolin-10-ol derivative, was synthesized and characterized by single-crystal X-ray diffraction. The crystal belongs to monoclinic space group P21/n, with a = 3.9573(4), b = 18.0416(18), c = 15.8210(16) Å, α = 90°, β = 96.139(3)°, and γ = 90°. Compound 1 exhibits an intramolecular six-membered-ring hydrogen bond, from which excited-state intramolecular proton transfer takes place, resulting in a proton-transfer tautomer emission of 625 nm in cyclohexane. The crystal structure is stabilized by intermolecular π–π interactions, which links a pair of molecules into a cyclic centrosymmetric dimer. Furthermore, the geometric structures, frontier molecular orbitals, and potential energy curves (PECs) for 1 in the ground and the first singlet excited state were fully rationalized by density functional theory (DFT) and time-dependent DFT calculations. Full article
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Open AccessArticle
Sol–Gel-Derived Glass-Ceramic Photorefractive Films for Photonic Structures
Crystals 2017, 7(2), 61; doi:10.3390/cryst7020061 -
Abstract
Glass photonics are widespread, from everyday objects around us to high-tech specialized devices. Among different technologies, sol–gel synthesis allows for nanoscale materials engineering by exploiting its unique structures, such as transparent glass-ceramics, to tailor optical and electromagnetic properties and to boost photon-management yield.
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Glass photonics are widespread, from everyday objects around us to high-tech specialized devices. Among different technologies, sol–gel synthesis allows for nanoscale materials engineering by exploiting its unique structures, such as transparent glass-ceramics, to tailor optical and electromagnetic properties and to boost photon-management yield. Here, we briefly discuss the state of the technology and show that the choice of the sol–gel as a synthesis method brings the advantage of process versatility regarding materials composition and ease of implementation. In this context, we present tin-dioxide–silica (SnO2–SiO2) glass-ceramic waveguides activated by europium ions (Eu3+). The focus is on the photorefractive properties of this system because its photoluminescence properties have already been discussed in the papers presented in the bibliography. The main findings include the high photosensitivity of sol–gel 25SnO2:75SiO2 glass-ceramic waveguides; the ultraviolet (UV)-induced refractive index change (Δn ~ −1.6 × 10−3), the easy fabrication process, and the low propagation losses (0.5 ± 0.2 dB/cm), that make this glass-ceramic an interesting photonic material for smart optical applications. Full article
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Open AccessArticle
Optimization of Enzyme-Mediated Calcite Precipitation as a Soil-Improvement Technique: The Effect of Aragonite and Gypsum on the Mechanical Properties of Treated Sand
Crystals 2017, 7(2), 59; doi:10.3390/cryst7020059 -
Abstract
The effectiveness of magnesium as a substitute material in enzyme-mediated calcite precipitation was evaluated. Magnesium sulfate was added to the injecting solution composed of urea, urease, and calcium chloride. The effect of the substitution on the amount of precipitated materials was evaluated through
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The effectiveness of magnesium as a substitute material in enzyme-mediated calcite precipitation was evaluated. Magnesium sulfate was added to the injecting solution composed of urea, urease, and calcium chloride. The effect of the substitution on the amount of precipitated materials was evaluated through precipitation tests. X-ray powder diffraction and scanning electron microscopy analyses were conducted to examine the mineralogical morphology of the precipitated minerals and to determine the effect of magnesium on the composition of the precipitated materials. In addition to calcite, aragonite and gypsum were formed as the precipitated materials. The effect of the presence of aragonite and gypsum, in addition to calcite, as a soil-improvement technique was evaluated through unconfined compressive strength tests. Soil specimens were prepared in polyvinyl chloride cylinders and treated with concentration-controlled solutions, which produced calcite, aragonite, and gypsum. The mineralogical analysis revealed that the low and high concentrations of magnesium sulfate effectively promoted the formation of aragonite and gypsum, respectively. The injecting solutions which produced aragonite and calcite brought about a significant improvement in soil strength. The presence of the precipitated materials, comprising 10% of the soil mass within a treated sand, generated a strength of 0.6 MPa. Full article
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Open AccessArticle
Molecular Dynamics Simulations of Hydroxyapatite Nanopores in Contact with Electrolyte Solutions: The Effect of Nanoconfinement and Solvated Ions on the Surface Reactivity and the Structural, Dynamical, and Vibrational Properties of Water
Crystals 2017, 7(2), 57; doi:10.3390/cryst7020057 -
Abstract
Hydroxyapatite, the main mineral phase of mammalian tooth enamel and bone, grows within nanoconfined environments and in contact with aqueous solutions that are rich in ions. Hydroxyapatite nanopores of different pore sizes (20 Å ≤ H ≤ 110 Å, where H is the
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Hydroxyapatite, the main mineral phase of mammalian tooth enamel and bone, grows within nanoconfined environments and in contact with aqueous solutions that are rich in ions. Hydroxyapatite nanopores of different pore sizes (20 Å ≤ H ≤ 110 Å, where H is the size of the nanopore) in contact with liquid water and aqueous electrolyte solutions (CaCl2 (aq) and CaF2 (aq)) were investigated using molecular dynamics simulations to quantify the effect of nanoconfinement and solvated ions on the surface reactivity and the structural and dynamical properties of water. The combined effect of solution composition and nanoconfinement significantly slows the self-diffusion coefficient of water molecules compared with bulk liquid. Analysis of the pair and angular distribution functions, distribution of hydrogen bonds, velocity autocorrelation functions, and power spectra of water shows that solution composition and nanoconfinement in particular enhance the rigidity of the water hydrogen bonding network. Calculation of the water exchange events in the coordination of calcium ions reveals that the dynamics of water molecules at the HAP–solution interface decreases substantially with the degree of confinement. Ions in solution also reduce the water dynamics at the surface calcium sites. Together, these changes in the properties of water impart an overall rigidifying effect on the solvent network and reduce the reactivity at the hydroxyapatite-solution interface. Since the process of surface-cation-dehydration governs the kinetics of the reactions occurring at mineral surfaces, such as adsorption and crystal growth, this work shows how nanoconfinement and solvation environment influence the molecular-level events surrounding the crystallization of hydroxyapatite. Full article
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Open AccessArticle
Silver Nanoprism-Loaded Eggshell Membrane: A Facile Platform for In Situ SERS Monitoring of Catalytic Reactions
Crystals 2017, 7(2), 45; doi:10.3390/cryst7020045 -
Abstract
We reported the fabrication of an in situ surface-enhanced Raman scattering (SERS) monitoring platform, comprised of a porous eggshell membrane (ESM) bioscaffold loaded with Ag nanoprism via an electrostatic self-assembly approach. The localized surface plasmon resonance (LSPR) property of silver nanoprism leads to
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We reported the fabrication of an in situ surface-enhanced Raman scattering (SERS) monitoring platform, comprised of a porous eggshell membrane (ESM) bioscaffold loaded with Ag nanoprism via an electrostatic self-assembly approach. The localized surface plasmon resonance (LSPR) property of silver nanoprism leads to the blue color of the treated ESMs. UV-vis diffuse reflectance spectroscopy, scanning electron microscope (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) measurements were employed to observe the microstructure and surface property of Ag nanoprisms on the ESMs. The silver nanoprism-loaded eggshell membrane (AgNP@ESM) exhibited strong catalytic activity for the reduction of 4-nitrophenol by sodium borohydride (NaBH4) and it can be easily recovered and reused for more than six cycles. Significantly, the composites also display excellent SERS efficiency, allowing the in situ SERS monitoring of molecular transformation in heterogeneous catalysis. The results indicate that the AgNP@ESM biocomposite can achieve both SERS and catalytic functionalities simultaneously in a single entity with high performance, which promotes the potential applications of ESM modified with functional materials. Full article
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Open AccessArticle
Anisotropic Magnetic Responses of Topological Crystalline Superconductors
Crystals 2017, 7(2), 58; doi:10.3390/cryst7020058 -
Abstract
Majorana Kramers pairs emerged on surfaces of time-reversal-invariant topological crystalline superconductors show the Ising anisotropy to an applied magnetic field. We clarify that crystalline symmetry uniquely determines the direction of the Majorana Ising spin for given irreduciblerepresentationsofpairpotential,derivingconstraintstotopologicalinvariants. In addition, necessary conditions for nontrivial
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Majorana Kramers pairs emerged on surfaces of time-reversal-invariant topological crystalline superconductors show the Ising anisotropy to an applied magnetic field. We clarify that crystalline symmetry uniquely determines the direction of the Majorana Ising spin for given irreduciblerepresentationsofpairpotential,derivingconstraintstotopologicalinvariants. In addition, necessary conditions for nontrivial topological invariants protected by the n-fold rotational symmetry are shown. Full article
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Open AccessArticle
Indium Substitution Effect on the Topological Crystalline Insulator Family (Pb1−xSnx)1−yInyTe: Topological and Superconducting Properties
Crystals 2017, 7(2), 55; doi:10.3390/cryst7020055 -
Abstract
Topological crystalline insulators (TCIs) have been of great interest in the area of condensed matter physics. We investigated the effect of indium substitution on the crystal structure and transport properties in the TCI system (Pb1−xSnx)1−yIn
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Topological crystalline insulators (TCIs) have been of great interest in the area of condensed matter physics. We investigated the effect of indium substitution on the crystal structure and transport properties in the TCI system (Pb1−xSnx)1−yInyTe. For samples with a tin concentration x50%, the low-temperature resisitivities show a dramatic variation as a function of indium concentration: with up to ∼2% indium doping, the samples show weak-metallic behavior similar to their parent compounds; with ∼6% indium doping, samples have true bulk-insulating resistivity and present evidence for nontrivial topological surface states; with higher indium doping levels, superconductivity was observed, with a transition temperature, Tc, positively correlated to the indium concentration and reaching as high as 4.7 K. We address this issue from the view of bulk electronic structure modified by the indium-induced impurity level that pins the Fermi level. The current work summarizes the indium substitution effect on (Pb,Sn)Te, and discusses the topological and superconducting aspects, which can be provide guidance for future studies on this and related systems. Full article
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Open AccessArticle
Interior Lamellar Assembly and Optical Birefringence in Poly(trimethylene terephthalate) Spherulites: Mechanisms from Past to Present
Crystals 2017, 7(2), 56; doi:10.3390/cryst7020056 -
Abstract
Poly(trimethylene terephthalate) (PTT) with its unique spherulitic morphologies, highly birefringent features, and crystal stability serves as a good candidate to study polymer crystallization and assembly. This review compiles the main findings on crystallization in PTT, including birefringence and morphology, thermal behavior, as well
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Poly(trimethylene terephthalate) (PTT) with its unique spherulitic morphologies, highly birefringent features, and crystal stability serves as a good candidate to study polymer crystallization and assembly. This review compiles the main findings on crystallization in PTT, including birefringence and morphology, thermal behavior, as well as the interior structure of PTT banded spherulites, in order to elucidate the origin and formation mechanism of banded spherulites. Interior observation through the inner anatomy of crystal assembly in banded spherulites hidden under the top surface is necessary to provide a complete picture for the unsettled arguments about formation mechanism. Careful attention should be taken when selecting the etching agent for exposing the lamellar structure of polymer spherulite, otherwise, misinterpretation could result Full article
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Open AccessArticle
Ab Initio Study of the Elastic and Mechanical Properties of B19 TiAl
Crystals 2017, 7(2), 39; doi:10.3390/cryst7020039 -
Abstract
A theoretical study of the structural, elastic, and mechanical properties of B19 TiAl intermetallic compound with orthorhombic structure has been carried out by using ab initio density functional theory calculations based on the projector augmented wave and the generalized gradient approximation. The optimized
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A theoretical study of the structural, elastic, and mechanical properties of B19 TiAl intermetallic compound with orthorhombic structure has been carried out by using ab initio density functional theory calculations based on the projector augmented wave and the generalized gradient approximation. The optimized structure parameters are found to be in agreement with the available experimental data. The orthorhombic B19 structure of TiAl is found to be mechanically stable at ground state in terms of formation energy and single crystal elastic constants. Additionally, the polycrystalline bulk, shear and Young’s moduli, Poisson’s ratio, Cauchy pressure, and anisotropy factors are obtained from the single crystal elastic constants. At ground state, the B19 TiAl is found to not only have intrinsic brittleness in terms of Pugh’s ratio, Poisson’s ratio, and Cauchy pressure, but also exhibit elastic anisotropy in terms of elastic anisotropy factors and orientation dependence of Young’s modulus. Full article
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Open AccessArticle
A Scheme for the Growth of Graphene Sheets Embedded with Nanocones
Crystals 2017, 7(2), 35; doi:10.3390/cryst7020035 -
Abstract
Based on the monolayer growth mode of graphene sheets (2D crystal) by chemical vapor deposition (CVD) on a Cu surface, it should be possible to grow the 2D crystal embedded with single wall carbon nanocones (SWCNC) if nano-conical pits are pre-fabricated on the
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Based on the monolayer growth mode of graphene sheets (2D crystal) by chemical vapor deposition (CVD) on a Cu surface, it should be possible to grow the 2D crystal embedded with single wall carbon nanocones (SWCNC) if nano-conical pits are pre-fabricated on the surface. However, a previous experiment showed that the growing graphene sheet can cross grain boundaries without bending, which seems to invalidate this route for growing SWCNCs. The criterion of Gibbs free energy was applied in the present work to address this issue, showing that the sheet can grow into the valley of a boundary if the boundary has a slope instead of a quarter-turn shape, and SWCNCs can be obtained by this route as long as the lower diameter of the pre-fabricated pit is larger than 1.6 nm and the deposition temperature is higher than 750 K. Full article
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Open AccessArticle
Atomistic Modelling of Si Nanoparticles Synthesis
Crystals 2017, 7(2), 54; doi:10.3390/cryst7020054 -
Abstract
Silicon remains the most important material for electronic technology. Presently, some efforts are focused on the use of Si nanoparticles—not only for saving material, but also for improving the efficiency of optical and electronic devices, for instance, in the case of solar cells
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Silicon remains the most important material for electronic technology. Presently, some efforts are focused on the use of Si nanoparticles—not only for saving material, but also for improving the efficiency of optical and electronic devices, for instance, in the case of solar cells coated with a film of Si nanoparticles. The synthesis by a bottom-up approach based on condensation from low temperature plasma is a promising technique for the massive production of such nanoparticles, but the knowledge of the basic processes occurring at the atomistic level is still very limited. In this perspective, numerical simulations can provide fundamental information of the nucleation and growth mechanisms ruling the bottom-up formation of Si nanoclusters. We propose to model the low temperature plasma by classical molecular dynamics by using the reactive force field (ReaxFF) proposed by van Duin, which can properly describe bond forming and breaking. In our approach, first-principles quantum calculations are used on a set of small Si clusters in order to collect all the necessary energetic and structural information to optimize the parameters of the reactive force-field for the present application. We describe in detail the procedure used for the determination of the force field and the following molecular dynamics simulations of model systems of Si gas at temperatures in the range 2000–3000 K. The results of the dynamics provide valuable information on nucleation rate, nanoparticle size distribution, and growth rate that are the basic quantities for developing a following mesoscale model. Full article
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Open AccessReview
On the Anionic Group Approximation to the Borate Nonlinear Optical Materials
Crystals 2017, 7(2), 50; doi:10.3390/cryst7020050 -
Abstract
In this mini-review type of article, a brief summary of the anionic group approximation as it relates to the borate nonlinear optical (NLO) crystals, an idea firstly proposed by Professor Chen, is presented.The basic idea, calculation method, tabulated coefficients of various common borate,
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In this mini-review type of article, a brief summary of the anionic group approximation as it relates to the borate nonlinear optical (NLO) crystals, an idea firstly proposed by Professor Chen, is presented.The basic idea, calculation method, tabulated coefficients of various common borate, as well as nitrate or carbonate groups, in their ideal geometries will be presented. New practices reveal that those parameters can still give very accurate predicted NLO coefficients for recently found NLO crystals without any adjustment of parameters. Full article
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Open AccessArticle
Kinetics and Morphology of Flow Induced Polymer Crystallization in 3D Shear Flow Investigated by Monte Carlo Simulation
Crystals 2017, 7(2), 51; doi:10.3390/cryst7020051 -
Abstract
To explore the kinetics and morphology of flow induced crystallization of polymers, a nucleation-growth evolution model for spherulites and shish-kebabs is built based on Schneider rate model and Eder model. The model considers that the spherulites are thermally induced, growing like spheres, while
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To explore the kinetics and morphology of flow induced crystallization of polymers, a nucleation-growth evolution model for spherulites and shish-kebabs is built based on Schneider rate model and Eder model. The model considers that the spherulites are thermally induced, growing like spheres, while the shish-kebabs are flow induced, growing like cylinders, with the first normal stress difference of crystallizing system being the driving force for the nucleation of shish-kebabs. A two-phase suspension model is introduced to describe the crystallizing system, which Finitely Extensible Non-linear Elastic-Peterlin (FENE-P) model and rigid dumbbell model are used to describe amorphous phase and semi-crystalline phase, respectively. Morphological Monte Carlo method is presented to simulate the polymer crystallization in 3D simple shear flow. Roles of shear rate, shear time and shear strain on the crystallization kinetics, morphology, and rheology are analyzed. Numerical results show that crystallization kinetics, morphology and rheology in shear flow are qualitatively in agreement with the theoretical, experimental and other numerical works which verifies the validity and effectiveness of our model and algorithm. To our knowledge, this is the first time that a model and an algorithm revealing the details of crystal morphology have been applied to the flow induced crystallization of polymers. Full article
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Open AccessArticle
SRG Inscription in Supramolecular Liquid Crystalline Polymer Film: Replacement of Mesogens
Crystals 2017, 7(2), 52; doi:10.3390/cryst7020052 -
Abstract
The photoinduced surface relief formation via mass transfer upon irradiation with patterned light has long been a subject of extensive investigation. In azobenzene-containing liquid crystalline materials, UV light irradiation that generates the cis isomer leads to the liquid crystal to isotropic photochemical transition.
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The photoinduced surface relief formation via mass transfer upon irradiation with patterned light has long been a subject of extensive investigation. In azobenzene-containing liquid crystalline materials, UV light irradiation that generates the cis isomer leads to the liquid crystal to isotropic photochemical transition. Due to this phase change, efficiency of the mass transfer to generate a surface relief grating (SRG) becomes markedly greater. We have previously indicated that azobenzene-colored SRG-inscribed film can be bleached by removing a hydrogen-bonded azobenzene mesogen. However, this process largely reduces the height feature of the SRG corrugation. Herein, we propose an extended procedure where a colorless mesogen is filled successively after the removal of the azobenzene side chain. The process involves four stages: (i) SRG inscription in a hydrogen-bonded supramolecular azobenzene material; (ii) crosslinking (insolubilization) of the SRG film; (iii) removal of azobenzene mesogen by rinsing with a solvent, and (iv) stuffing the hollow film with a different mesogen. Although the final stuffing stage was insufficient at the present stage, this work demonstrates the possibility and validity of the strategy of mesogen replacement. Full article
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Open AccessArticle
Optical Properties of the Fresnoite Ba2TiSi2O8 Single Crystal
Crystals 2017, 7(2), 53; doi:10.3390/cryst7020053 -
Abstract
In this work, using large-sized single crystals of high optical quality, the optical properties of Ba2TiSi2O8 were systematically investigated, including transmission spectra, refractive indices and nonlinear absorption properties. The crystal exhibits a high transmittance (>84%) over a wide
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In this work, using large-sized single crystals of high optical quality, the optical properties of Ba2TiSi2O8 were systematically investigated, including transmission spectra, refractive indices and nonlinear absorption properties. The crystal exhibits a high transmittance (>84%) over a wide wavelength range from 340 to 2500 nm. The refractive indices in the range from 0.31256 to 1.01398 μm were measured, and Sellmeier’s equations were fitted by the least squares method. The nonlinear absorption properties were studied by using the open-aperture Z-scan technique, with a nonlinear absorption coefficient measured to be on the order of 0.257 cm/GW at the peak power density of 16.4 GW/cm2. Such high transmittance and wide transparency indicate that optical devices using the Ba2TiSi2O8crystal can be applied over a wide wavelength range. Furthermore, the small nonlinear absorption observed in Ba2TiSi2O8 will effectively increase the optical conversion efficiency, decreasing the generation of laser damage of the optical device. Full article
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Open AccessArticle
Ultrathin Nanocrystalline Magnetic Wires
Crystals 2017, 7(2), 48; doi:10.3390/cryst7020048 -
Abstract
The magnetic characteristics of FINEMET type glass-coated nanowires and submicron wires are investigated by taking into account the structural evolution induced by specific annealing all the way from a fully amorphous state to a nanocrystalline structure. The differences between the magnetic properties of
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The magnetic characteristics of FINEMET type glass-coated nanowires and submicron wires are investigated by taking into account the structural evolution induced by specific annealing all the way from a fully amorphous state to a nanocrystalline structure. The differences between the magnetic properties of these ultrathin wires and those of the thicker glass-coated microwires and “conventional” wires with similar structures have been emphasized and explained phenomenologically. The domain wall propagation in these novel nanowires and submicron wires, featuring a combination between an amorphous and a crystalline structure, has also been studied, given the recent interest in the preparation and investigation of new materials suitable for the development of domain wall logic applications. Full article
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Open AccessArticle
Graphene-Hexagonal Boron Nitride Heterostructure as a Tunable Phonon–Plasmon Coupling System
Crystals 2017, 7(2), 49; doi:10.3390/cryst7020049 -
Abstract
The layered van der Waals (vdW) heterostructure, assembled from monolayer graphene, hexagonal boron nitride (h-BN) and other atomic crystals in various combinations, is emerging as a new paradigm with which to attain desired electronic and optical properties. In this paper, we study theoretically
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The layered van der Waals (vdW) heterostructure, assembled from monolayer graphene, hexagonal boron nitride (h-BN) and other atomic crystals in various combinations, is emerging as a new paradigm with which to attain desired electronic and optical properties. In this paper, we study theoretically the mid-infrared optical properties of the vdW heterostructure based on the graphene–h-BN system. The light–matter interaction of this heterostructure system is described by the hyperbolic phonon–plasmon polaritons which originate from the coupling modes of surface plasmon polaritons (SPPs) in graphene with hyperbolic phonon polaritons (HPPs) in h-BN. By numerical simulation, we find that the coupling modes are governed by the Fermi level of monolayer graphene, the thickness of the h-BN slab and the mode excitation sequence of SPPs and HPPs. Moreover, the response of the coupling modes of the graphene–h-BN heterostructure on a noble metal layer is also proposed in this paper. Full article
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