
Bistable dark solitons of a cubicquintic Helmholtz equation
International Nuclear Information System (INIS)
Christian, J. M.; McDonald, G. S.; ChamorroPosada, P.
20100101
We provide a report on exact analytical bistable dark spatial solitons of a nonlinear Helmholtz equation with a cubicquintic refractiveindex model. Our analysis begins with an investigation of the modulational instability characteristics of Helmholtz plane waves. We then derive a dark soliton by mapping the desired asymptotic form onto a uniform background field and obtain a more general solution by deploying rotational invariance laws in the laboratory frame. The geometry of the new soliton is explored in detail, and a range of new physical predictions is uncovered. Particular attention is paid to the unified phenomena of arbitraryangle offaxis propagation and nondegenerate bistability. Crucially, the corresponding solution of paraxial theory emerges in a simultaneous multiple limit. We conclude with a set of computer simulations that examine the role of Helmholtz dark solitons as robust attractors.

G2 cubic transition between two circles with shape control
Science.gov (United States)
Habib, Zulfiqar; Sakai, Manabu
20090101
This paper describes a method for joining two circles with an Sshaped or with a broken back Cshaped transition curve, composed of at most two spiral segments. In highway and railway route design or carlike robot path planning, it is often desirable to have such a transition. It is shown that a single cubic curve can be used for blending or for a transition curve preserving G2 continuity with local shape control parameter and more flexible constraints. Provision of the shape parameter and flexibility provide freedom to modify the shape in a stable manner which is an advantage over previous work by Meek, Walton, Sakai and Habib.

Dynamic Displacement Disorder of Cubic BaTiO3
Science.gov (United States)
Paściak, M.; Welberry, T. R.; Kulda, J.; Leoni, S.; Hlinka, J.
20180401
The threedimensional distribution of the xray diffuse scattering intensity of BaTiO3 has been recorded in a synchrotron experiment and simultaneously computed using molecular dynamics simulations of a shell model. Together, these have allowed the details of the disorder in paraelectric BaTiO3 to be clarified. The narrow sheets of diffuse scattering, related to the famous anisotropic longitudinal correlations of Ti ions, are shown to be caused by the overdamped anharmonic soft phonon branch. This finding demonstrates that the occurrence of narrow sheets of diffuse scattering agrees with a displacive picture of the cubic phase of this textbook ferroelectric material. The presented methodology allows one to go beyond the harmonic approximation in the analysis of phonons and phononrelated scattering.

Principal spectra describing magnetooptic permittivity tensor in cubic crystals
Energy Technology Data Exchange (ETDEWEB)
Hamrlová, Jana [Nanotechnology Centre, VSB – Technical University of Ostrava, listopadu 15, Ostrava, 708 33 Czech Republic (Czech Republic); IT4Innovations Centre, VSB – Technical University of Ostrava, listopadu 15, Ostrava, 708 33 Czech Republic (Czech Republic); Legut, Dominik [IT4Innovations Centre, VSB – Technical University of Ostrava, listopadu 15, Ostrava, 708 33 Czech Republic (Czech Republic); Veis, Martin [Faculty of Mathematics and Physics, Charles University, Ke Karlovu 3, Prague, 121 16 Czech Republic (Czech Republic); Pištora, Jaromír [Nanotechnology Centre, VSB – Technical University of Ostrava, listopadu 15, Ostrava, 708 33 Czech Republic (Czech Republic); Hamrle, Jaroslav, Email: jaroslav.hamrle@vsb.cz [IT4Innovations Centre, VSB – Technical University of Ostrava, listopadu 15, Ostrava, 708 33 Czech Republic (Czech Republic); Faculty of Mathematics and Physics, Charles University, Ke Karlovu 3, Prague, 121 16 Czech Republic (Czech Republic); Department of Physics, VSB – Technical University of Ostrava, 17. listopadu 15, Ostrava, 708 33 Czech Republic (Czech Republic)
20161215
We provide unified phenomenological description of magnetooptic effects being linear and quadratic in magnetization. The description is based on few principal spectra, describing elements of permittivity tensor up to the second order in magnetization. Each permittivity tensor element for any magnetization direction and any sample surface orientation is simply determined by weighted summation of the principal spectra, where weights are given by crystallographic and magnetization orientations. The number of principal spectra depends on the symmetry of the crystal. In cubic crystals owning point symmetry we need only four principal spectra. Here, the principal spectra are expressed by ab initio calculations for bcc Fe, fcc Co and fcc Ni in optical range as well as in hard and soft xray energy range, i.e. at the 2p and 3pedges. We also express principal spectra analytically using modified Kubo formula.

Structure and energetics of nanotwins in cubic boron nitrides
Energy Technology Data Exchange (ETDEWEB)
Zheng, Shijian, Email: sjzheng@imr.ac.cn, Email: zrf@buaa.edu.cn; Ma, Xiuliang [Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); Zhang, Ruifeng, Email: sjzheng@imr.ac.cn, Email: zrf@buaa.edu.cn [School of Materials Science and Engineering, and International Research Institute for Multidisciplinary Science, Beihang University, Beijing 100191 (China); Huang, Rong [Key Laboratory of Polar Materials and Devices, Ministry of Education, East China Normal University, Shanghai 200062 (China); Taniguchi, Takashi [National Institute for Materials Science, Tsukuba, Ibaraki 3050044 (Japan); Ikuhara, Yuichi [Nanostructures Research Laboratory, Japan Fine Ceramics Center, Nagoya 4568587 (Japan); Institute of Engineering Innovation, The University of Tokyo, Tokyo 1138656 (Japan); Beyerlein, Irene J. [Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)
20160822
Recently, nanotwinned cubic boron nitrides (NT cBN) have demonstrated extraordinary leaps in hardness. However, an understanding of the underlying mechanisms that enable nanotwins to give orders of magnitude increases in material hardness is still lacking. Here, using transmission electron microscopy, we report that the defect density of twin boundaries depends on nanotwin thickness, becoming defectfree, and hence more stable, as it decreases below 5 nm. Using ab initio density functional theory calculations, we reveal that the Shockley partials, which may dominate plastic deformation in cBNs, show a high energetic barrier. We also report that the cBN twin boundary has an asymmetrically charged electronic structure that would resist migration of the twin boundary under stress. These results provide important insight into possible nanotwin hardening mechanisms in cBN, as well as how to design these nanostructured materials to reach their full potential in hardness and strength.

Cubic phase nanoparticles for sustained release of ibuprofen: formulation, characterization, and enhanced bioavailability study
Science.gov (United States)
Dian, Linghui; Yang, Zhiwen; Li, Feng; Wang, Zhouhua; Pan, Xin; Peng, Xinsheng; Huang, Xintian; Guo, Zhefei; Quan, Guilan; Shi, Xuan; Chen, Bao; Li, Ge; Wu, Chuanbin
20130101
In order to improve the oral bioavailability of ibuprofen, ibuprofenloaded cubic nanoparticles were prepared as a delivery system for aqueous formulations. The cubic inner structure was verified by cryogenic transmission electron microscopy. With an encapsulation efficiency greater than 85%, the ibuprofenloaded cubic nanoparticles had a narrow size distribution around a mean size of 238 nm. Differential scanning calorimetry and Xray diffraction determined that ibuprofen was in an amorphous and molecular form within the lipid matrix. The in vitro release of ibuprofen from cubic nanoparticles was greater than 80% at 24 hours, showing sustained characteristics. The pharmacokinetic study in beagle dogs showed improved absorption of ibuprofen from cubic nanoparticles compared to that of pure ibuprofen, with evidence of a longer halflife and a relative oral bioavailability of 222% (P ibuprofenloaded cubic nanoparticles provide a promising carrier candidate with an efficient drug delivery for therapeutic treatment. PMID:23468008

Genealogical electronic coupling procedure incorporating the HartreeFock interacting space and suitable for degenerate point groups. Application to excited states of BH3
International Nuclear Information System (INIS)
Swope, W.C.; Schaefer, H.F. III; Yarkony, D.R.
19800101
The use of ClebschGordantype coupling coefficients for finite point groups is applied to the problem of constructing symmetrized Nelectron wave functions (configurations) for use by the HartreeFock SCF and CI methods of determining electronic wave functions for molecular systems. The configurations are eigenfunctions of electronic spin operators, and transform according to a particular irreducible representation of the relevant group of spatial operations which leave the BornOppenheimer Hamiltonian invariant. The method proposed for constructing the configurations involves a genealogical coupling procedure. It is particularly useful for studies of molecules which belong to a group which has multiply degenerate irreducible representations. The advantage of the method is that it results in configurations which are real linear combinations of determinants of real symmetry orbitals. This procedure for constructing configurations also allows for the identification of configurations which have no matrix element of the Hamiltonian with a reference configuration. It is therefore possible to construct a HartreeFock interacting space of configurations which can speed the convergence of a CI wave function. The coupling method is applied to a study of the ground and two excited electronic states of BH 3 in its D/sub 3h/ geometry. The theoretical approach involved HartreeFock SCF calculations followed by single and double substitution CI calculations, both of which employed doublezeta plus polarization quality basis sets

Targetspace duality between simple compact Lie groups and Lie algebras under the Hamiltonian formalism. Pt. 1. Remnants of duality at the classic level
International Nuclear Information System (INIS)
Alvarez, O.; Liu Chienhao
19960101
It has been suggested that a possible classical remnant of the phenomenon of targetspace duality (Tduality) would be the equivalence of the classical string Hamiltonian systems. Given a simple compact Lie group G with a biinvariant metric and a generating function Γ suggested in the physics literature, we follow the above line of thought and work out the canonical transformation Φ generated by Γ together with an Adinvariant metric and a Bfield on the associated Lie algebra g of G so that G and g form a string targetspace dual pair at the classical level under the Hamiltonian formalism. In this article, some general features of this Hamiltonian setting are discussed. We study properties of the canonical transformation Φ including a careful analysis of its domain and image. The geometry of the Tdual structure on g is lightly touched. We leave the task of tracing back the Hamiltonian formalism at the quantum level to the sequel of this paper. (orig.). With 4 figs

Electric quadrupole interaction in cubic BCC αFe
Energy Technology Data Exchange (ETDEWEB)
Błachowski, A.; Komędera, K. [Mössbauer Spectroscopy Division, Institute of Physics, Pedagogical University, ul. Podchorążych 2, PL30084 Kraków (Poland); Ruebenbauer, K., Email: sfrueben@cyfkr.edu.pl [Mössbauer Spectroscopy Division, Institute of Physics, Pedagogical University, ul. Podchorążych 2, PL30084 Kraków (Poland); Cios, G.; Żukrowski, J. [AGH University of Science and Technology, Academic Center for Materials and Nanotechnology, Av. A. Mickiewicza 30, PL30059 Kraków (Poland); Górnicki, R. [RENON, ul. Gliniana 15/15, PL30732 Kraków (Poland)
20160715
Mössbauer transmission spectra for the 14.41keV resonant line in {sup 57}Fe have been collected at room temperature by using {sup 57}Co(Rh) commercial source and αFe strainfree single crystal as an absorber. The absorber was magnetized to saturation in the absorber plane perpendicular to the γray beam axis applying small external magnetic field. Spectra were collected for various orientations of the magnetizing field, the latter lying close to the [110] crystal plane. A positive electric quadrupole coupling constant was found practically independent on the field orientation. One obtains the following value V{sub zz} = +1.61(4) × 10{sup 19} Vm{sup −2} for the (average) principal component of the electric field gradient (EFG) tensor under assumption that the EFG tensor is axially symmetric and the principal axis is aligned with the magnetic hyperfine field acting on the {sup 57}Fe nucleus. The nuclear spectroscopic electric quadrupole moment for the first excited state of the {sup 57}Fe nucleus was adopted as +0.17 b. Similar measurement was performed at room temperature using asrolled polycrystalline αFe foil of high purity in the zero external field. Corresponding value for the principal component of the EFG was found as V{sub zz} = +1.92(4) × 10{sup 19} Vm{sup −2}. Hence, it seems that the origin of the EFG is primarily due to the local (atomic) electronic wave function distortion caused by the spin–orbit interaction between effective electronic spin S and incompletely quenched electronic angular momentum L. It seems as well that the lowest order term proportional to the product L·λ·S dominates, as no direction dependence of the EFG principal component is seen. The lowest order term is isotropic for a cubic symmetry as one has λ=λ 1 for cubic systems with the symbol 1 denoting unit operator and λ being the coupling parameter.  Highlights: • Precision of MS the same as MAPON • Real scans versus magnetization direction • A challenge

Electric quadrupole interaction in cubic BCC αFe
International Nuclear Information System (INIS)
Błachowski, A.; Komędera, K.; Ruebenbauer, K.; Cios, G.; Żukrowski, J.; Górnicki, R.
20160101
Mössbauer transmission spectra for the 14.41keV resonant line in "5"7Fe have been collected at room temperature by using "5"7Co(Rh) commercial source and αFe strainfree single crystal as an absorber. The absorber was magnetized to saturation in the absorber plane perpendicular to the γray beam axis applying small external magnetic field. Spectra were collected for various orientations of the magnetizing field, the latter lying close to the [110] crystal plane. A positive electric quadrupole coupling constant was found practically independent on the field orientation. One obtains the following value V_z_z = +1.61(4) × 10"1"9 Vm"−"2 for the (average) principal component of the electric field gradient (EFG) tensor under assumption that the EFG tensor is axially symmetric and the principal axis is aligned with the magnetic hyperfine field acting on the "5"7Fe nucleus. The nuclear spectroscopic electric quadrupole moment for the first excited state of the "5"7Fe nucleus was adopted as +0.17 b. Similar measurement was performed at room temperature using asrolled polycrystalline αFe foil of high purity in the zero external field. Corresponding value for the principal component of the EFG was found as V_z_z = +1.92(4) × 10"1"9 Vm"−"2. Hence, it seems that the origin of the EFG is primarily due to the local (atomic) electronic wave function distortion caused by the spin–orbit interaction between effective electronic spin S and incompletely quenched electronic angular momentum L. It seems as well that the lowest order term proportional to the product L·λ·S dominates, as no direction dependence of the EFG principal component is seen. The lowest order term is isotropic for a cubic symmetry as one has λ=λ 1 for cubic systems with the symbol 1 denoting unit operator and λ being the coupling parameter.  Highlights: • Precision of MS the same as MAPON • Real scans versus magnetization direction • A challenge for ab initio calculations

Characterization, Microstructure, and Dielectric properties of cubic pyrochlore structural ceramics
KAUST Repository
Li, Yangyang
20130501
The (BMN) bulk materials were sintered at 1050°C, 1100°C, 1150°C, 1200°C by the conventional ceramic process, and their microstructure and dielectric properties were investigated by Scanning electron microscopy (SEM), Xray diffraction (XRD), Raman spectroscopy, Transmission electron microscopy (TEM) (including the Xray energy dispersive spectrometry EDS and high resolution transmission electron microscopy HRTEM) and dielectric impedance analyzer. We systematically investigated the structure, dielectric properties and voltage tunable property of the ceramics prepared at different sintering temperatures. The XRD patterns demonstrated that the synthesized BMN solid solutions had cubic phase pyrochloretype structure when sintered at 1050°C or higher, and the lattice parameter (a) of the unit cell in BMN solid solution was calculated to be about 10.56Å. The vibrational peaks observed in the Raman spectra of BMN solid solutions also confirmed the cubic phase pyrochloretype structure of the synthesized BMN. According to the Scanning Electron Microscope (SEM) images, the grain size increased with increasing sintering temperature. Additionally, it was shown that the densities of the BMN ceramic tablets vary with sintering temperature. The calculated theoretical density for the BMN ceramic tablets sintered at different temperatures is about 6.7521 . The density of the respective measured tablets is usually amounting more than 91% and 5 approaching a maximum value of 96.5% for sintering temperature of 1150°C. The microstructure was investigated by using Scanning Transmission Electron Microscope (STEM), Xray diffraction (XRD). Combined with the results obtained from the STEM and XRD, the impact of sintering temperature on the macroscopic and microscopic structure was discussed. The relative dielectric constant ( ) and dielectric loss ( ) of the BMN solid solutions were measured to be 161200 and (at room temperature and 100Hz1MHz), respectively. The BMN solid

Transformation of topologically closepacked βW to bodycentered cubic αW: Comparison of experiments and computations.
Science.gov (United States)
Barmak, Katayun; Liu, Jiaxing; Harlan, Liam; Xiao, Penghao; Duncan, Juliana; Henkelman, Graeme
20171021
The enthalpy and activation energy for the transformation of the metastable form of tungsten, βW, which has the topologically closepacked A15 structure (space group Pm3¯n), to equilibrium αW, which is bodycentered cubic (A2, space group Im3¯m), was measured using differential scanning calorimetry. The βW films were 1 μmthick and were prepared by sputter deposition in argon with a small amount of nitrogen. The transformation enthalpy was measured as 8.3 ± 0.4 kJ/mol (86 ± 4 meV/atom) and the transformation activation energy as 2.2 ± 0.1 eV. The measured enthalpy was found to agree well with the difference in energies of α and β tungsten computed using density functional theory, which gave a value of 82 meV/atom for the transformation enthalpy. A calculated concerted transformation mechanism with a barrier of 0.4 eV/atom, in which all the atoms in an A15 unit cell transform into A2, was found to be inconsistent with the experimentally measured activation energy for any critical nucleus larger than two A2 unit cells. Larger calculations of eight A15 unit cells spontaneously relax to a mechanism in which part of the supercell first transforms from A15 to A2, creating a phase boundary, before the remaining A15 transforms into the A2 phase. Both calculations indicate that a nucleation and growth mechanism is favored over a concerted transformation. More consistent with the experimental activation energy was that of a calculated local transformation mechanism at the A15A2 phase boundary, computed as 1.7 eV using molecular dynamics simulations. This calculated phase transformation mechanism involves collective rearrangements of W atoms in the disordered interface separating the A15 and A2 phases.

Quantum isometry groups
Indian Academy of Sciences (India)
Jyotishman Bhowmick
20151107
Nov 7, 2015 ... Classical. Quantum. Background. Compact Hausdorff space. Unital C∗ algebra. GelfandNaimark. Compact Group. Compact Quantum Group. Woronowicz. Group Action. Coaction. Woronowicz. Riemannian manifold. Spectral triple. Connes. Isometry group. Quantum Isometry Group. To be discussed.

The timedependence of the defective nature of ice Ic (cubic ice) and its implications for atmospheric science
Science.gov (United States)
Sippel, Christian; Koza, Michael M.; Hansen, Thomas C.; Kuhs, Werner F.
20100501
The possible atmospheric implication of ice Ic (cubic ice) has already been suggested some time ago in the context of snow crystal formation [1]. New findings from airborne measurements in cirrus clouds and contrails have put ice Ic into the focus of interest to understand the socalled "supersaturation puzzle" [2,3,4]. Our recent microstructural work on ice Ic [5,6] appears to be highly relevant in this context. We have found that ice Ic is characterized by a complex stacking fault pattern, which changes as a function of temperature as well as time. Indeed, from our own [7] and other group's work [8] one knows that (in contrast to earlier believe) ice Ic can form up to temperatures at least as high as 240K  thus in the relevant range for cirrus clouds. We have good preliminary evidence that the "cubicity" (which can be related to stacking fault probabilities) as well as the particle size of ice Ic are the relevant parameters for this correlation. The "cubicity" of stacking faulty ice Ic (established by diffraction) correlates nicely with the increased supersaturation at decreasing temperatures observed in cirrus clouds and contrails, a fact, which may be considered as further evidence for the presence of ice Ic. Recently, we have studied the timedependency of the changes in both "cubicity" and particle size at various temperatures of relevance for cirrus clouds and contrails by insitu neutron powder diffraction. The timescales over which changes occur (several to many hours) are similar to the lifetime of cirrus clouds and contrails and suggest that the supersaturation situation may change within this time span in the natural environment too. Some accompanying results obtained by cryoSEM (scanning electron microscopy) work will also be presented and suggest that stackingfaulty ice Ic has kinky surfaces providing many more active centres for heterogeneous reactions on the surface than in the usually assumed stable hexagonal form of ice Ih with its rather

Reflection of electromagnetic wave from the boundary of the piezoelectric halfspace with cubic symmetry
Science.gov (United States)
Berberyan, A. Kh; Garakov, V. G.
20180401
A large number of works have been devoted to investigation of the influence of the piezoelectric properties of a material on the propagation of elastic waves [1–3]. Herewith, the quasistatic piezoelasticity model was mainly used. In the problem of an electromagnetic wave reflection from an elastic medium with piezoelectric properties, it is necessary to consider hyperbolic equations [4].

Experimental evidence of body centered cubic iron in Earth's core
Science.gov (United States)
Hrubiak, R.; Meng, Y.; Shen, G.
20171201
The Earth's core is mainly composed of iron. While seismic evidence has shown a liquid outer core and a solid inner core, the crystalline nature of the solid iron at the core condition remains debated, largely due to the difficulties in experimental determination of exact polymorphs at corresponding pressuretemperature conditions. We have examined crystal structures of iron up to 220 GPa and 6000 K with xray diffraction using a doublesided laser heating system at HPCAT, Advanced Photon Source. The iron sample is confined in a small chamber surrounded by single crystal MgO. The laser power can be modulated together with temperature measurements. The modulated heating of iron in an MgO single crystal matrix allows for microstructure analysis during heating and after the sample is quenched. We present experimental evidence of a bodycenteredcubic (BCC) iron from about 100 GPa and 3000 K to at least 220 GPa and 4000 K. The observed BCC phase may be consistent with a theoretically predicted BCC phase that is dynamically stable in similar pressuretemperature conditions [1]. We will discuss the stability region of the BCC phase and the melting curve of iron and their implications in the nature of the Earth's inner core. References: A. B. Belonoshko et al., Nat. Geosci., 16 (2017).

Cubicquintic solitons in the checkerboard potential
International Nuclear Information System (INIS)
Driben, Rodislav; Zyss, Joseph; Malomed, Boris A.; Gubeskys, Arthur
20070101
We introduce a twodimensional (2D) model which combines a checkerboard potential, alias the KronigPenney (KP) lattice, with the selffocusing cubic and selfdefocusing quintic nonlinear terms. The beamsplitting mechanism and soliton multistability are explored in this setting, following the recently considered 1D version of the model. Families of single and multipeak solitons (in particular, five and ninepeak species naturally emerge in the 2D setting) are found in the semiinfinite gap, with both branches of bistable families being robust against perturbations. For singlepeak solitons, the variational approximation (VA) is developed, providing for a qualitatively correct description of the transition from monostability to the bistability. 2D solitons found in finite band gaps are unstable. Also constructed are two different species of stable vortex solitons, arranged as fourpeak patterns ('oblique' and 'straight' ones). Unlike them, compact 'cratershaped' vortices are unstable, transforming themselves into randomly walking fundamental beams

Tunable surface configuration of skyrmion lattices in cubic helimagnets
Science.gov (United States)
Wan, Xuejin; Hu, Yangfan; Wang, Biao
20180601
In bulk helimagnets, the presence of magnetic skyrmion lattices is always accompanied by a periodic stress field due to the intrinsic magnetoelastic coupling. The release of this nontrivial stress field at the surface causes a periodic displacement field, which characterizes a novel particlelike property of skyrmion: its surface configuration. Here, we derive the analytical solution of this displacement field for semiinfinite cubic helimagnet with the skyrmion magnetization approximated by the tripleQ representation. For MnSi, we show that the skyrmion lattices have a bumpy surface configuration characterized by periodically arranged peaks with a characteristic height of about 10‑13 m. The pattern of the peaks can be controlled by varying the strength of the applied magnetic field. Moreover, we prove that the surface configuration varies together with the motion and deformation of the skyrmion lattices. As a result, the surface configuration can be tuned by application of electric current, mechanical loads, as well as any other effective external fields for skyrmion lattices.

Plasmon polaritons in cubic lattices of spherical metallic nanoparticles
Science.gov (United States)
Lamowski, Simon; Mann, CharlieRay; Hellbach, Felicitas; Mariani, Eros; Weick, Guillaume; Pauly, Fabian
20180301
We theoretically investigate plasmon polaritons in cubic lattices of spherical metallic nanoparticles. The nanoparticles, each supporting triplydegenerate localized surface plasmons, couple through the Coulomb dipoledipole interaction, giving rise to collective plasmons that extend over the whole metamaterial. The latter hybridize with photons forming plasmon polaritons, which are the hybrid lightmatter eigenmodes of the system. We derive general analytical expressions to evaluate both plasmon and plasmonpolariton dispersions and the corresponding eigenstates. These are obtained within a Hamiltonian formalism, which takes into account retardation effects in the dipolar interaction between the nanoparticles and considers the dielectric properties of the nanoparticles as well as their surrounding. Within this model we predict polaritonic splittings in the nearinfrared to the visible range of the electromagnetic spectrum that depend on polarization, lattice symmetry, and wavevector direction. Finally, we show that the predictions of our model are in excellent quantitative agreement with conventional finitedifference frequencydomain simulations, but with the advantages of analytical insight and significantly reduced computational cost.

Electrical leakage phenomenon in heteroepitaxial cubic silicon carbide on silicon
Science.gov (United States)
Pradeepkumar, Aiswarya; Zielinski, Marcin; Bosi, Matteo; Verzellesi, Giovanni; Gaskill, D. Kurt; Iacopi, Francesca
20180601
Heteroepitaxial 3CSiC films on silicon substrates are of technological interest as enablers to integrate the excellent electrical, electronic, mechanical, thermal, and epitaxial properties of bulk silicon carbide into wellestablished silicon technologies. One critical bottleneck of this integration is the establishment of a stable and reliable electronic junction at the heteroepitaxial interface of the ntype SiC with the silicon substrate. We have thus investigated in detail the electrical and transport properties of heteroepitaxial cubic silicon carbide films grown via different methods on lowdoped and highresistivity silicon substrates by using van der Pauw Hall and transfer length measurements as test vehicles. We have found that Si and C intermixing upon or after growth, particularly by the diffusion of carbon into the silicon matrix, creates extensive interstitial carbon traps and hampers the formation of a stable rectifying or insulating junction at the SiC/Si interface. Although a reliable pn junction may not be realistic in the SiC/Si system, we can achieve, from a point of view of the electrical isolation of inplane SiC structures, leakage suppression through the substrate by using a highresistivity silicon substrate coupled with deep recess etching in between the SiC structures.