552 results on '"Perpendicular"'
Search Results
2. Controllable Nonclassical Conductance Switching in Nanoscale Phase‐Separated (PbI 2 ) 1− x (BiI 3 ) x Layered Crystals
- Author
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Hee Joon Jung, Yaobin Xu, Vinayak P. Dravid, Patrick Krantz, Grant C. B. Alexander, Mercouri G. Kanatzidis, Venkat Chandrasekhar, and Samuel Davis
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Phase boundary ,Materials science ,Condensed matter physics ,Mechanics of Materials ,Transmission electron microscopy ,Mechanical Engineering ,Phase (matter) ,Perpendicular ,Conductance ,Ionic bonding ,General Materials Science ,Electrical measurements ,Nanoscopic scale - Abstract
Layered 2D (PbI2 )1-x (BiI3 )x materials exhibit a nonlinear dependence in structural and charge transport properties unanticipated from the combination of PbI2 and BiI3 . Within (PbI2 )1-x (BiI3 )x crystals, phase integration yields deceptive structural features, while phase boundary separation leads to new conductance switching behavior observed as large peaks in current during current-voltage (I-V) measurements (±100 V). Temperature- and time-dependent electrical measurements demonstrate that the behavior is attributed to ionic transport perpendicular to the layers. High-resolution transmission electron microscopy reveals that the structure of (PbI2 )1-x (BiI3 )x is a "brick wall" consisting of two phases, Pb-rich and Bi-rich. These brick-like features are 10s nm a side and it is posited that iodide ion transport at the interfaces of these regions is responsible for the conductance switching action.
- Published
- 2021
3. Effects of the Annealing Temperature before Cooling under Magnetic Field on Perpendicular Exchange Coupling in (Pt/Co)5/NiO
- Author
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Rachid Belhi
- Subjects
Materials science ,Condensed matter physics ,Annealing (metallurgy) ,Non-blocking I/O ,Magnetization reversal ,Surfaces and Interfaces ,Condensed Matter Physics ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Magnetic field ,Coupling (electronics) ,Exchange bias ,Materials Chemistry ,Perpendicular ,Electrical and Electronic Engineering - Published
- 2021
4. Behaviour of two-dimensional liquid dusty plasmas under perpendicular magnetic fields
- Author
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Yan Feng, Qiaoling Wang, and Kang Wang
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Physics ,Condensed matter physics ,0103 physical sciences ,Perpendicular ,Probability density function ,Plasma ,010306 general physics ,Condensed Matter Physics ,01 natural sciences ,010305 fluids & plasmas ,Magnetic field - Published
- 2017
5. Spin‐Torque Memristors: Spin‐Torque Memristors Based on Perpendicular Magnetic Tunnel Junctions for Neuromorphic Computing (Adv. Sci. 10/2021)
- Author
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Maosen Guo, Wang Lin, Biao Pan, Houyi Cheng, Daoqian Zhu, Jiangfeng Du, Shaoxin Li, Kaihua Cao, Tianrui Zhang, Wenlong Cai, Xueying Zhang, Mengxing Wang, Weisheng Zhao, and Fazhan Shi
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Physics ,Condensed matter physics ,Inside Back Cover ,General Chemical Engineering ,General Engineering ,General Physics and Astronomy ,Medicine (miscellaneous) ,Memristor ,Biochemistry, Genetics and Molecular Biology (miscellaneous) ,law.invention ,Neuromorphic engineering ,law ,Perpendicular ,Torque ,General Materials Science ,Spin-½ - Abstract
In article number 2004645, Weisheng Zhao and co‐workers develop a nano‐scale memristor device based on magnetic tunneling junction. A kind of chiral vortex spin texture plays a key role in forming the multi‐level magnetoresistance. Thanks to its advantages such as long endurance and high speed, this spintronic device may take neuromorphic computing one step further. [Image: see text]
- Published
- 2021
6. Influence of oriented β-lamellae on deformation and pore formation in β-nucleated polypropylene
- Author
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Ming Xiang, Guan Xu, Tong Wu, Feng Yang, Qian Ge, and Lei Ding
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Polypropylene ,Materials science ,Polymers and Plastics ,Isotropy ,02 engineering and technology ,Deformation (meteorology) ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,0104 chemical sciences ,Stress (mechanics) ,chemistry.chemical_compound ,Crystallinity ,chemistry ,Materials Chemistry ,Perpendicular ,Physical and Theoretical Chemistry ,Composite material ,0210 nano-technology ,Anisotropy ,Tensile testing - Abstract
Four β-nucleated polypropylene samples with increasing die draw ratio (DDR) were prepared to modify lamellae arrangement. The DSC, SEM, and 2D-XRD results show that all four cast films had similar crystallinity, high contents of β-crystal but lowering stability of β-lamellae with ascending DDR. Meanwhile, the anisotropy of β-lamellae distribution strengthens gently and the stacked lamellae structure perpendicular to the machine direction (MD) predominates dramatically. Tensile testing at 25 °C and 90 °C were conducted along MD and transverse direction (TD), respectively. The markedly expanding difference of deformation indicates the anisotropy highlighted significantly. Additionally, when the samples stretched along MD, a more homogeneous deformation occurs with ascending anisotropy, which is completely opposite to the β-lamellae stability. But samples deformed more heterogeneous when stretched along TD. The characterization of morphological evolutions during stretching shows that the stacked lamellae debonds uniformly and abundant microvoids formed when the sample stretched along MD with higher anisotropy, resulting in evenly dispersion of stress, consequently making a more uniform distribution of defects and a better isotropic deformation. Moreover, the microfibrils and defects distributed uniformly within higher orientation sample after longitudinal stretching stretched along MD, leading to the dramatic improvement of pore size distribution of the membrane after biaxial stretching. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017
- Published
- 2017
7. The capacity of active heat method in evaluation of seepage
- Author
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Chunju Zhao, Yihong Zhou, and Q. Cuong Bui
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Fluid Flow and Transfer Processes ,Void (astronomy) ,Computer simulation ,020209 energy ,0211 other engineering and technologies ,Electrical wire ,02 engineering and technology ,Condensed Matter Physics ,Temperature measurement ,Fiber optic sensor ,0202 electrical engineering, electronic engineering, information engineering ,Perpendicular ,Geotechnical engineering ,Embankment dam ,Geology ,021101 geological & geomatics engineering - Abstract
The analysis of temperature variation inside an embankment dam is known as a feasible approach for seepage estimation in an embankment dam. The time needed for temperature surveillance could be considerably reduced when it is implemented under the condition of heat injection. However, a detailed description about the method as well as its capability has not been sufficiently presented in previous research. To fill this void, a realistic scale finite-element modeling was conducted to explain and assess the abilities of the approach. A 15 m dam segment containing a suffusion layer was simulated with 11 scenarios, where it was found that the applications of temperature measurement with the complement of high-power line heat sources in standpipes could give a solution for seepage determination in a dam segment with length up to 6 m, and the combination of fiber optic sensors and electrical wires provides an ability to assess seepage in a long dam distance. It is noteworthy that the efficiency in the perpendicular plane to the fiber optic sensor and electrical wire is limited.
- Published
- 2017
8. Hydrothermal synthesis of dendritic BaTiO3 ceramic powders and its application in BaTiO3 /P(VDF-TrFE) composites
- Author
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Peng Qu, Cheng Li, Sijing Wang, and Xiaolin Liu
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010302 applied physics ,Marketing ,Materials science ,02 engineering and technology ,Dielectric ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Casting ,Hydrothermal circulation ,visual_art ,Electric field ,0103 physical sciences ,Materials Chemistry ,Ceramics and Composites ,Perpendicular ,visual_art.visual_art_medium ,Hydrothermal synthesis ,Particle ,Ceramic ,Composite material ,0210 nano-technology - Abstract
Dendritic BaTiO3 ceramic powders (d-BT) were prepared by hydrothermal method in order to improve the dielectric properties of d-BT/P(VDF-TrFE) composites, in which, KOH was used as the branch-directing agent. The effect of hydrothermal time on the branch length of d-BT particle was mainly studied. The results showed that 1.0-2.5 μm d-BT particles were obtained after hydrothermal treating for 12 hours. The particle was composed of two kinds of branches, one was primary branch with about 800 nm in length and another with150-250 nm. A d-BT/P(VDF-TrFE) composites were formed by solution casting, in which d-BT powders as dielectric fillers and the composites exhibited high-energy storage performance. Its maximum energy density reached to 9.78 J/cm3, twice as compared with pure P(VDF-TrFE). The branches of d-BT particles may act as key roles when the composites existed in electric field. Some branches perpendicular to the external electric field provided the increase in the breakdown strength and others parallel to the external electric field brought the enhancement of the dielectric constant, which simultaneously resulted in high energy density of the composites.
- Published
- 2017
9. Position dependent surface quality in selective laser melting
- Author
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Wayne Hall, Andreas Öchsner, Johann Hirsch, Markus Merkel, and Leonhard Hitzler
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0209 industrial biotechnology ,Materials science ,Fabrication ,Plane (geometry) ,Mechanical Engineering ,02 engineering and technology ,Surface finish ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,020901 industrial engineering & automation ,Mechanics of Materials ,Perpendicular ,Surface roughness ,General Materials Science ,Selective laser melting ,Composite material ,0210 nano-technology ,Inert gas ,Volatility (chemistry) - Abstract
Additive manufacturing receives nowadays opulent attention in both media and ongoing research. In particular, the techniques involving full melting of the raw material, enabling the fabrication of directly deployable components, are of high interest. To date, there are still secondary influences which are yet to be considered, leading to substantial, mainly directional dependent, deviations. The study at hand investigated the surface roughness dependencies in plane, focusing on the interaction of the unidirectional inert gas stream with the irradiation sequence; more precisely the weld splashes emerging from the melt pool, and the resulting in plane pattern. The surface roughness of the upwards orientated faces revealed clear fluctuations, being lowest close to the gas-inlet and also in the back area of the machine. Perpendicular to the fabrication plane aligned surfaces did not reveal any volatility regarding the inert gas stream. Increasing the energy density of the irradiation led to an increase in the surface roughness of all side faces, but to an improved roughness of the upwards facing surfaces coupled with a significant reduction in evident weld splashes.
- Published
- 2017
10. 3D Dislocation structure evolution in strontium titanate: Spherical indentation experiments and MD simulations
- Author
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Alexander Stukowski, Farhan Javaid, and Karsten Durst
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010302 applied physics ,Materials science ,Condensed matter physics ,Mineralogy ,Polishing ,02 engineering and technology ,Plasticity ,021001 nanoscience & nanotechnology ,01 natural sciences ,chemistry.chemical_compound ,Glide plane ,chemistry ,Peierls stress ,Indentation ,0103 physical sciences ,Materials Chemistry ,Ceramics and Composites ,Perpendicular ,Strontium titanate ,Dislocation ,0210 nano-technology - Abstract
In the present work, the dislocation structure evolution around and underneath the spherical indentations in (001) oriented single crystalline strontium titanate (STO) was revealed by using an etch-pit technique and molecular dynamics (MD) simulations. The 3D defect structure at various length scales and subsurface depths was resolved with the help of a sequential polishing, etching, and imaging technique. This analysis, combined with load–displacement data, shows that the incipient plasticity (manifested as sudden indenter displacement bursts) is strongly influenced by preexisting dislocations. In the early stage of plastic deformation, the dislocation pile-ups are all aligned in 〈100〉 directions, lying on {110}45 planes, inclined at 45° to the (001) surface. At higher mean contact pressure and larger indentation depth, however, dislocation pile-ups along 〈110〉 directions appear, lying on {110}90 planes, perpendicular to the (100) surface. MD simulations confirm the glide plane nature and provide further insights into the dislocation formation mechanisms by tracing the evolution of the complete dislocation line network as function of indentation depth.
- Published
- 2016
11. Formation of abnormal dual-peak profiles in large tilt angle boron implantation
- Author
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Jeffrey Lam, Zhihong Mai, and Lei Zhu
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010302 applied physics ,Range (particle radiation) ,Materials science ,Silicon ,Doping ,chemistry.chemical_element ,02 engineering and technology ,Surfaces and Interfaces ,General Chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Molecular physics ,Surfaces, Coatings and Films ,Ion ,Tilt (optics) ,chemistry ,Sputtering ,0103 physical sciences ,Materials Chemistry ,Perpendicular ,0210 nano-technology ,Boron - Abstract
Large tilt angle (LTA) implantation has been employed in Si manufacturing processes in many applications, such as lightly doped drain and halo implant. The depth profile of boron ions usually consists of only single peak at incident angle of 0° with respect to the perpendicular of the silicon surface. However, an abnormal dual-peak profile was observed at LTA (>40°) with incident energy of 160 keV. By using a Monte Carlo method to simulate the ion implant process, it was found that the projected range of boron ions agrees completely with the formation of the first peak position that is shallower in depth, while the cause for the second peak that corresponds with a depth much deeper in the Si substrate was unknown. During the simulation, it was also found that when the tilt angle was increased, the sputtering yields and Si displacements increased significantly, and this phenomenon indicates that during LTA implantation, Si damage may not be negligible anymore. The Si damage effect that was as due to either low Si density or transient Si displacement in the simulation could have led to partial incident boron ions penetrating much deeper into the Si substrate and thus, caused the emergence of the second peak. Copyright © 2016 John Wiley & Sons, Ltd.
- Published
- 2016
12. Anisotropic Elliott-Yafet theory and application to KC8potassium intercalated graphite
- Author
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Bálint Náfrádi, Bence G. Márkus, Dávid Iván, Ferenc Simon, Balázs Dóra, Péter Szirmai, Lénárd Szolnoki, and László Forró
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Materials science ,Condensed matter physics ,Plane (geometry) ,Graphene ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Electronic, Optical and Magnetic Materials ,law.invention ,Magnetic field ,symbols.namesake ,law ,0103 physical sciences ,symbols ,Perpendicular ,Condensed Matter::Strongly Correlated Electrons ,Graphite ,010306 general physics ,0210 nano-technology ,Hamiltonian (quantum mechanics) ,Electron paramagnetic resonance ,Anisotropy - Abstract
We report Electron Spin Resonance (ESR) measurements on stage-I potassium intercalated graphite (KC$_8$). Angular dependent measurements show that the spin-lattice relaxation time is longer when the magnetic field is perpendicular to the graphene layer as compared to when the magnetic field is in the plane. This anisotropy is analyzed in the framework of the Elliott-Yafet theory of spin-relaxation in metals. The analysis considers an anisotropic spin-orbit Hamiltonian and the first order perturbative treatment of Elliott is reproduced for this model Hamiltonian. The result provides an experimental input for the first-principles theories of spin-orbit interaction in layered carbon and thus to a better understanding of spin-relaxation phenomena in graphene and in other layered materials as well.
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- 2016
13. Interactions between temozolomide and guanine and its S and Se-substituted analogues
- Author
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Steve Scheiner, Aristote Matondo, Okuma Emile Kasende, and Jules Tshishimbi Muya
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010405 organic chemistry ,Guanine ,010402 general chemistry ,Condensed Matter Physics ,01 natural sciences ,Tautomer ,Atomic and Molecular Physics, and Optics ,0104 chemical sciences ,chemistry.chemical_compound ,Crystallography ,chemistry ,Potential energy surface ,Perpendicular ,Molecule ,Density functional theory ,Physical and Theoretical Chemistry ,Dispersion (chemistry) ,Natural bond orbital - Abstract
Temozolomide was paired with guanine, 6-selenoguanine, and 6-thioguanine, as well as the SH tautomer of the latter. The potential energy surface of each heterodimer was searched for all minima, using Dispersion-Corrected Density Functional Theory and MP2 methods. Among the dozens of minima, three categories were observed. Stacked geometries place the aromatic systems of the two molecules parallel to one another, while the two systems are roughly perpendicular to one another in a second category. Also found are coplanar structures held together by H-bonds. Dispersion proves to be a dominating attractive force for the stacked structures, less so for perpendicular, and smallest for the coplanar dimers. Geometries and energetics are relatively insensitive to S and Se substitution, but tautomerization reverses relative stabilities of different geometries.
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- 2016
14. Inducing Elasticity through Oligo-Siloxane Crosslinks for Intrinsically Stretchable Semiconducting Polymers
- Author
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Tadanori Kurosawa, Jin Young Oh, Jie Xu, Bob C. Schroeder, Leo Shaw, Ging-Ji Nathan Wang, Stephanie J. Benight, and Zhenan Bao
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Materials science ,Nanotechnology ,Young's modulus ,02 engineering and technology ,Conjugated system ,010402 general chemistry ,01 natural sciences ,Biomaterials ,chemistry.chemical_compound ,symbols.namesake ,Electrochemistry ,Perpendicular ,Composite material ,chemistry.chemical_classification ,Polymer ,Elasticity (physics) ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,0104 chemical sciences ,Electronic, Optical and Magnetic Materials ,Organic semiconductor ,chemistry ,Buckling ,Siloxane ,symbols ,0210 nano-technology - Abstract
The promise of wearable and implantable devices has made stretchable organic semiconductors highly desirable. Though there are increasing attempts to design intrinsically stretchable conjugated polymers, their performance in terms of charge carrier mobility and maximum fracture strain is still lacking behind extrinsic approaches (i.e., buckling, Kirigami interconnects). Here, polymer crosslinking with flexible oligomers is applied as a strategy to reduce the tensile modulus and improve fracture strain, as well as fatigue resistance for a high mobility diketopyrrolopyrrole polymer. These polymers are crosslinked with siloxane oligomers to give stretchable films stable up to a strain e = 150% and 500 strain-and-release cycles of 100% strain without the formation of nanocracks. Organic field-effect transistors are prepared to assess the electrical properties of the crosslinked film under cyclic strain loading. An initial average mobility (μavg) of 0.66 cm2 V−1 s−1 is measured at 0% strain. A steady μavg above 0.40 cm2 V−1 s−1 is obtained in the direction perpendicular to the strain direction after 500 strain-and-release cycles of 20% strain. The μavg in the direction parallel to strain, however, is compromised due to the formation of wrinkles.
- Published
- 2016
15. Modified coffee rings for quasi-1D interconnects
- Author
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Christina K. Michaels, Andrew Blyskal, and Luz J. Martinez-Miranda
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Materials science ,Condensed matter physics ,business.industry ,Nanowire ,Coffee ring effect ,Physics::Optics ,02 engineering and technology ,Grating ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,0104 chemical sciences ,Electronic, Optical and Magnetic Materials ,Optics ,Percolation ,Perpendicular ,Electrical measurements ,Current (fluid) ,0210 nano-technology ,Anisotropy ,business - Abstract
Silver nanowires (AgNW) in solution with isopropyl alcohol are deposited on photolithographed gratings of varying depth. The deposition results in a modified coffee ring where the flow is redirected along the grating direction. We investigate the anisotropic character of the flow by performing electrical measurements at different concentrations of the nanowires, and for each of the grating depths used. We measure the electrical current along the directions perpendicular and parallel to the gratings. The current anisotropy tends to disappear at higher concentrations. The flow arranges the NW's into a 2D anisotropic arrangement by analyzing how the electrical percolation behaves. By observing the properties this 2D anisotropic arrangement as a function of concentration and grating depth, we can predict where a quasi-1D interconnect can be obtained.
- Published
- 2016
16. Two-Dimensional Skyrmion Lattice Formation in a Nematic Liquid Crystal Consisting of Highly Bent Banana Molecules
- Author
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Sungmin Kang, Tianqi Li, Xiaobin Liang, Eun-Woo Lee, Junji Watanabe, Masatoshi Tokita, and Ken Nakajima
- Subjects
Phase transition ,Biaxial nematic ,Condensed matter physics ,Chemistry ,Skyrmion ,Bent molecular geometry ,General Medicine ,02 engineering and technology ,General Chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Catalysis ,Condensed Matter::Soft Condensed Matter ,Tetragonal crystal system ,Crystallography ,Liquid crystal ,Lattice (order) ,0103 physical sciences ,Perpendicular ,010306 general physics ,0210 nano-technology - Abstract
We synthesized a novel banana-shaped molecule based on a 1,7-naphthalene central core that exhibits a distinct mesomorphism of the nematic-to-nematic phase transition. Both the X-ray profile and direct imaging of atomic force microscopy (AFM) investigations clearly indicates the formation of an anomalous nematic phase possessing a two-dimensional (2D) tetragonal lattice with a large edge (ca. 59 Å) directed perpendicular to the director in the low-temperature nematic phase. One plausible model is proposed by an analogy of skyrmion lattice in which two types of cylinders formed from left- and right-handed twist-bend helices stack into a 2D tetragonal lattice, diminishing the inversion domain wall.
- Published
- 2016
17. Field emission patterns showing symmetry of electronic states in graphene edges
- Author
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Kazuya Nakakubo, Yahachi Saito, Kohji Iwata, Noboru Yokoyama, Koji Asaka, and Hitoshi Nakahara
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Materials science ,Graphene ,02 engineering and technology ,Surfaces and Interfaces ,General Chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Molecular physics ,Surfaces, Coatings and Films ,law.invention ,Field emission microscopy ,Field electron emission ,Delocalized electron ,Atomic orbital ,Zigzag ,law ,0103 physical sciences ,Physics::Atomic and Molecular Clusters ,Materials Chemistry ,Perpendicular ,Cluster (physics) ,Atomic physics ,010306 general physics ,0210 nano-technology - Abstract
Intriguing field emission microscopy (FEM) images reflecting subnanometer-sized structures of emitting sites and/or electronic orbitals have been observed from graphene edges. Graphene emitters with free edges (i.e. open edges) show a striped pattern (dubbed as a ‘lip pattern’) consisting of an array of streaked spots (or oval-shaped spots); the direction of striation is perpendicular to the graphene sheet, and each stripe is divided into two wings by a central dark band running parallel to the graphene sheet. The dark band may be due to the distractive interference of electrons emitted from π orbitals with a phase difference of π on either side of the graphene. From the magnification calibration using FEM images of an aluminum cluster with atomic resolution, the spacing of the streaked spots is found to be close to the distance between adjacent carbon atoms aligned along the zigzag and armchair edges. These observations suggest that the lip pattern reflects the symmetry of π states strongly delocalized at edge atoms. Copyright © 2016 John Wiley & Sons, Ltd.
- Published
- 2016
18. Effects of Classical and Neo-classical Cross-field Transport of Tungsten Impurity in Realistic Tokamak Geometry
- Author
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R. Schneider, H. Inoue, Akiyoshi Hatayama, S. Yamoto, Kazuo Hoshino, Xavier Bonnin, D. P. Coster, Y. Homma, and Y. Sawada
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Physics ,Guiding center ,Tokamak ,Divertor ,Geometry ,Plasma ,Condensed Matter Physics ,01 natural sciences ,010305 fluids & plasmas ,law.invention ,Physics::Plasma Physics ,law ,0103 physical sciences ,Orbit (dynamics) ,Coulomb ,Perpendicular ,Test particle ,010306 general physics - Abstract
The initial simulation study of the neoclassical perpendicular self-diffusion transport in the SOL/Divertor regions for a realistic tokamak geometry with the IMPGYRO code has been performed in this paper. One of the most unique features of the IMPGYRO code is calculating exact Larmor orbit of the test particle instead of assuming guiding center approximation. Therefore, effects of the magnetic drifts in realistic tokamaks are naturally taken into account in the IMPGYRO code. This feature makes it possible to calculate neoclassical transport processes, which possibly become large in the SOL/divertor plasma. Indeed, neoclassical self-diffusion process, the resultant effect of the combination of magnetic drift and Coulomb collisions with background ions, has already been included in the IMPGYRO model. In the present paper, prior to implementing the detailed model of neoclassical transport process into IMPGYRO, we have investigated the effect of neoclassical selfdiffusion in a realistic tokamak geometry with lower single null X-point. We also use a model with guiding center approximation in order to compare with the IMPGYRO full orbit model. The preliminary calculation results of each model have shown differences in the perpendicular average velocity of impurity ions at the top region of the SOL. The mechanism which leads to the difference has been discussed. (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
- Published
- 2016
19. Effect of molecular weight on microcrystalline structure formation in polymer with perylenediimide side chain
- Author
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Shiki Nojima, Kevin L. White, Atsushi Takahara, Ryohei Ishige, Noboru Ohta, Kazutaka Kamitani, Tomoyasu Hirai, and Makoto Kido
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chemistry.chemical_classification ,Materials science ,Polymers and Plastics ,02 engineering and technology ,Polymer ,Crystal structure ,Substrate (electronics) ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,0104 chemical sciences ,Crystallography ,chemistry ,Chain (algebraic topology) ,Polymer chemistry ,Materials Chemistry ,Perpendicular ,Side chain ,Fiber ,Physical and Theoretical Chemistry ,Thin film ,0210 nano-technology - Abstract
The effect of molecular weight on the molecular aggregation structure of polymers bearing a pendant perylenediimide (PDI) side chain, designated PAc12PDI, was investigated using synchrotron radiation X-ray diffraction measurements. It was found that depending on molecular weight, either the main chain axis or the side chain axis behaves as the longitudinal axis in fiber samples and was aligned parallel to the fiber axis. A similar phenomenon is present in thin film samples, but was complicated by the additional influence of the interfacial free energy of the side chain group. Even in the case of the polymer with lower molecular weight, the face plane of PDI was found to show both parallel and perpendicular orientations to the substrate (i.e., flat-on and edge-on orientations). On the other hand, if the length of the main chain is sufficiently long with respect to the length of the side chain, the face plane of PDI was oriented perpendicular to the substrate, leading to an edge-on orientation in the thin film. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 2275–2283
- Published
- 2016
20. Design of split ring antennas for WLAN and WiMAX applications
- Author
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S. Imaculate Rosaline and Singaravelu Raghavan
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Engineering ,business.industry ,020208 electrical & electronic engineering ,Electrical engineering ,Metamaterial ,020206 networking & telecommunications ,02 engineering and technology ,Condensed Matter Physics ,Atomic and Molecular Physics, and Optics ,Radio spectrum ,Microstrip ,Electronic, Optical and Magnetic Materials ,Radiation pattern ,Optics ,0202 electrical engineering, electronic engineering, information engineering ,Perpendicular ,Electrical and Electronic Engineering ,Antenna (radio) ,business ,Microwave ,Ground plane - Abstract
This paper compares the design of two compact monopole antennas based on metamaterial inspired split ring structures. The effect of orientation of split axis to the direction of an incident EM wave is discussed. When the axis of the split is parallel to the direction of EM wave propagation, it results in a narrow band creation and when it is perpendicular, it leads to a notch frequency. Antenna 1 is intended for WLAN (2.4/5.2/5.8 GHz) application whereas antenna 2 operates on both WLAN and WiMAX (3.5 GHz) frequency bands. Both the antennas are printed on a 30 × 30 × 0.8 mm3 FR-4 substrate with a partial ground plane and is fed by a microstrip line. The structures mainly differ in their split positions. Analysis of the split ring structures is also discussed. Prototype of the proposed structures are fabricated and the measured results comply greatly with the simulated results. The antenna has consistent radiation pattern over all the working region. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:2117–2122, 2016
- Published
- 2016
21. Investigation of Interfacial Reaction Products and Stress Distribution in Selective Laser Melted Al12Si/SiC Composite Using Confocal Raman Microscopy
- Author
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Charlie Kong, Thomas Becker, Xiaopeng Li, and Timothy B. Sercombe
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010302 applied physics ,Equiaxed crystals ,Materials science ,Confocal ,Composite number ,Analytical chemistry ,02 engineering and technology ,Molar absorptivity ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Laser ,01 natural sciences ,law.invention ,symbols.namesake ,stomatognathic system ,law ,0103 physical sciences ,Microscopy ,Perpendicular ,symbols ,General Materials Science ,0210 nano-technology ,Raman spectroscopy - Abstract
The interfacial reaction products and stress distribution in a selective laser melted Al12Si/SiC composite are studied using confocal Raman microscopy. Results reveal that needle-like Al4C3 and equiaxed Si are located at the interface between the Al matrix and SiC particles. This reaction is triggered by the high temperature within the SiC due to its high laser absorptivity. Raman frequency shifts to lower wavenumber are observed in both the SiC and Si, suggesting the existence of tensile stress within the interface. The tensile stress in SiC is higher in the build direction than in the direction perpendicular to the build direction. No such difference is observed in the Si. The reason is ascribed to the Gaussian distribution of the laser energy density and stress relief through the interfacial reaction.
- Published
- 2016
22. A broadband perpendicularE-plane waveguide-to-suspended stripline transition
- Author
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M. A. Nikravan and Do-Hoon Kwon
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Coupling ,Materials science ,business.industry ,Electrical engineering ,020206 networking & telecommunications ,Topology (electrical circuits) ,02 engineering and technology ,Condensed Matter Physics ,Waveguide (optics) ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials ,Resonator ,0202 electrical engineering, electronic engineering, information engineering ,Perpendicular ,Optoelectronics ,Insertion loss ,Electrical and Electronic Engineering ,business ,Microwave ,Stripline - Abstract
A perpendicular E-plane transition between rectangular waveguide (WG) and suspended stripline (SSL) in the Ku-band is presented. The topology of coupling network is studied and design guidelines are provided. A 10-dB return loss bandwidth (BW) of 12% was obtained using a patch resonator on a double-sided single-layer dielectric substrate combined with a cavity behind the resonator of a very shallow depth as low as 1 mm for a compact design. An insertion loss of 0.18 dB at 13.8 GHz was achieved in the measurement of a back-to-back SSL–WG–SSL transition. Comparison of the measured performances with the state-of-the-art WG transitions to SSL shows a 1.5 times improvement in frequency bandwidth and a three times reduction in electrical dimensions. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1831–1834, 2016
- Published
- 2016
23. Correlation of sapphire off-cut and reduction of defect density in MOVPE grown AlN
- Author
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Michael Kneissl, Markus Weyers, Anna Mogilatenko, Tim Wernicke, Arne Knauer, S. Hagedorn, and Johannes Enslin
- Subjects
010302 applied physics ,Diffraction ,Coalescence (physics) ,Materials science ,Condensed matter physics ,business.industry ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Epitaxy ,01 natural sciences ,Electronic, Optical and Magnetic Materials ,Condensed Matter::Materials Science ,Optics ,0103 physical sciences ,Perpendicular ,Sapphire ,Grain boundary ,Metalorganic vapour phase epitaxy ,Dislocation ,0210 nano-technology ,business - Abstract
X-ray diffraction and TEM investigations of MOVPE grown AlN on sapphire with small off-cuts to a- and m-plane reveal the influence of the off-cut direction and angle on the reduction of threading dislocation density by annihilation during growth. Higher off-cut angles as well as off-cut to a-plane seem to facilitate the annihilation, with the main reduction taking place within the first 300 nm layer thickness. On planar substrate the thickness is limited by cracking to below 2 μm which also limits the ability to further reduce the defect density. By epitaxial lateral overgrowth on stripe patterned substrates the crack-free thickness is increased and further reduction of the defect density is possible. This process is effective up to 3–5 μm layer thickness. Using templates with off-cuts ≥0.2° to m-plane, step bunching perpendicular to the stripe direction occurs and bends the vertically directed threading dislocations into inclined grain boundaries starting from the point of coalescence. These partially block/incline threading dislocations over the ridge areas and thus further reduce the dislocation density. The dislocations are concentrated in stripes over the ridges and the coalescence areas. For smaller off-cut to m or especially for off-cut to a-plane, the dislocation distribution is more homogeneous but nevertheless stripe-like with alternating densities of low 108 cm−2 in the laterally overgrown areas and low 109 cm−2 in the areas over the ridges and the coalescence lines.
- Published
- 2016
24. Negative Poisson's ratio in cubic materials along principal directions
- Author
-
Duc Tam Ho, Sung Youb Kim, Soon-Yong Kwon, Soon-Dong Park, and Tong Seok Han
- Subjects
Materials science ,Auxetics ,Mathematical analysis ,Magnitude (mathematics) ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Poisson distribution ,01 natural sciences ,Poisson's ratio ,Electronic, Optical and Magnetic Materials ,Stress (mechanics) ,symbols.namesake ,Transverse plane ,Computational chemistry ,Finite strain theory ,0103 physical sciences ,symbols ,Perpendicular ,010306 general physics ,0210 nano-technology - Abstract
This report employed molecular statics simulation and density-functional-theory calculation to study the Poisson's ratios of face-centered-cubic materials. We provide numerical and theoretical evidences to show that cubic materials can exhibit auxetic behavior in a principal direction under proper loading conditions. When a stress perpendicular to the loading direction is applied, cubic materials can exhibit a negative Poisson's ratio at finite strain. The negative Poisson's ratio behavior, including its direction and value, is highly dependent on the direction and magnitude of the transversely applied stresses. As a result, we show that it is possible to tune the direction and magnitude of the negative Poisson's ratio behavior of cubic materials by controlling the transverse loadings.
- Published
- 2016
25. Determination of lateral block size and mosaicity of crystals using X‐ray diffraction from the edge of the sample
- Author
-
Jarosław Serafińczuk
- Subjects
010302 applied physics ,Materials science ,business.industry ,02 engineering and technology ,General Chemistry ,Substrate (electronics) ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Mosaicity ,Crystal ,Reciprocal lattice ,Optics ,Tilt (optics) ,0103 physical sciences ,X-ray crystallography ,Perpendicular ,General Materials Science ,0210 nano-technology ,business ,Scherrer equation - Abstract
In this paper a novel lateral block size characterization method based on X-ray diffractometry (XRD) is presented. The developed method based on scans of plans perpendicular to the surface visible from the edge of the sample and subconsequent numerical analysis based on Scherrer equation. In presented investigations as a reference sample bulk GaN substrate fabricated by AMMONO Ltd. was used. The GaN layers deposited on sapphire substrate were investigated as a case of study. Moreover, a method of analyzing the magnitude of the tilt and twist mosaicity based on the scans of rocking curves and reciprocal lattice maps (RLM) from the edge of sample is presented. As an example for this methodology highly mosaicited SiC crystal was used. Presented approach allows to directly determine the value of the angular deviation of mosaicity in a direction perpendicular and parallel to the sample surface.
- Published
- 2016
26. The Impact of Interlayer Electronic Coupling on Charge Transport in Organic Semiconductors: A Case Study on Titanylphthalocyanine Single Crystals
- Author
-
Yuanping Yi, Lang Jiang, Yonggang Zhen, Liqiang Li, Zhigang Shuai, Zhang Zongpeng, Changli Cheng, Guangyao Zhao, Hua Geng, Huanli Dong, and Wenping Hu
- Subjects
Coupling ,Work (thermodynamics) ,Condensed matter physics ,Chemistry ,Transistor ,Nanotechnology ,Charge (physics) ,General Medicine ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Catalysis ,0104 chemical sciences ,law.invention ,Organic semiconductor ,chemistry.chemical_compound ,law ,Perpendicular ,Phthalocyanine ,0210 nano-technology ,Curse of dimensionality - Abstract
Traditionally, it is believed that three-dimensional transport networks are preferable to those of lower dimensions. We demonstrate that inter-layer electronic couplings may result in a drastic decrease of charge mobilities by utilizing field-effect transistors (FET) based on two phases of titanyl phthalocyanine (TiOPc) crystals. The α-phase crystals with electronic couplings along two dimensions show a maximum mobility up to 26.8 cm(2) V(-1) s(-1) . In sharp contrast, the β-phase crystals with extra significant inter-layer electronic couplings show a maximum mobility of only 0.1 cm(2) V(-1) s(-1) . Theoretical calculations on the bulk crystals and model slabs reveal that the inter-layer electronic couplings for the β-phase devices will diminish remarkably the device charge transport abilities owing to the coupling direction perpendicular to the current direction. This work provides new insights into the impact of the dimensionality and directionality of the packing arrangements on charge transport in organic semiconductors.
- Published
- 2016
27. Determination of 1:2 Ordered Domain Boundaries in Ba[(Co, Zn, Mg)1/3 Nb2/3 ]O3 Dielectric Ceramics
- Author
-
Xiang Ming Chen, Hui Gu, and Pian Pian Ma
- Subjects
010302 applied physics ,Materials science ,Condensed matter physics ,Superlattice ,Perturbation (astronomy) ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Dielectric ceramics ,Crystallography ,Transmission electron microscopy ,visual_art ,0103 physical sciences ,Materials Chemistry ,Ceramics and Composites ,Perpendicular ,visual_art.visual_art_medium ,Ceramic ,0210 nano-technology ,High-resolution transmission electron microscopy ,Crystal twinning - Abstract
The boundaries of 1:2 ordered domains in Ba[(Co, Zn, Mg)1/3Nb2/3]O3 perovskite ceramics are comprehensively studied by high-resolution transmission electron microscopy (HRTEM) on the base of atomic position simulation. The atomic configurations for four types of twin boundaries are determined. A-type and B-type boundary, which lie along (001)c and (110)c planes, respectively, are conservative. C-type boundary parallels to (111)c plane, while Г-type boundary is perpendicular to (111)c plane. At C-type and Г-type boundary, atomic intersection leads to a buffer layer, among which the B-site cations are generally disordered. The width of Г-type boundary is larger than that of C-type boundary, so is the perturbation to the system. The energy of four types of twin boundaries is proved to be “A-type & B-type < C-type < Г-type” according to the magnitude of the destabilization to the system. Single antiphase boundary (APB) is considered to be nonconservative. However, when combined with conservative twin boundary, an extra ordered structure with a periodicity of 1.24 nm along [001]c direction and a periodicity of 0.87 nm along [110]c direction forms. The boundary regions are indeed stabilized by the new superlattice.
- Published
- 2016
28. Magnetic-Field-Directed Self-Assembly of Programmable Mesoscale Shapes
- Author
-
O. Thompson Mefford, Longfei Ye, Philip Pstrak, A. R. Mohtasebzadeh, Cory Dolbashian, Ben Fellows, Thomas M. Crawford, and Tanner Pearson
- Subjects
Materials science ,Field (physics) ,Nanoparticle ,Nanotechnology ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Molecular physics ,0104 chemical sciences ,Electronic, Optical and Magnetic Materials ,Magnetic field ,Biomaterials ,Electrochemistry ,Perpendicular ,Magnetic nanoparticles ,Self-assembly ,0210 nano-technology ,Layer (electronics) ,Microscale chemistry - Abstract
User-programmed meso- to microscale 2D shapes using magnetic nanoparticles as building blocks with magnetic-field-directed self-assembly are created. The assembly templates are magnetically recorded using perpendicular magnetic recording (PMR) media. The results demonstrate that PMR can template user-designed features in two dimensions down to 30 nm in size, i.e., the nanoparticle diameter. It has been also shown that the nanoparticles assemble onto transitions between oppositely magnetized regions in the medium. At these transitions, the magnetic field gradients are extremely large (25 MT m−1 2 nm above the medium) and change rapidly with height (≈1015 T/m/m within 20 nm of the surface). It is found that 30 nm diameter particles assemble into 1–2 layers with feature widths ranging from 30 to 350 nm. It is hypothesized that large lateral growth can occur because the magnetic forces parallel to the disk extend up to 150 nm on either side of a recorded transition, falling off more slowly with distance than the vertical magnetic forces. Once lateral growth saturates, a second layer of nanoparticles begins to assemble on top of the first layer, suggesting strong potential for controlling layer-by-layer assembly through appropriate design of the medium and its resulting field gradient profiles.
- Published
- 2016
29. An Unusual Extrusion Texture in Mg-Gd-Y-Zr Alloys
- Author
-
Terence G. Langdon, Reza Alizadeh, Reza Mahmudi, and Alfonso H.W. Ngan
- Subjects
010302 applied physics ,Materials science ,Metallurgy ,Alloy ,Recrystallization (metallurgy) ,02 engineering and technology ,engineering.material ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Solvent drag ,0103 physical sciences ,Perpendicular ,engineering ,General Materials Science ,Extrusion ,Grain boundary ,0210 nano-technology ,Electron backscatter diffraction - Abstract
Texture evolution is studied by EBSD in Mg–9Gd–4Y–0.4Zr (GW94), Mg–5Gd–4Y–0.4Zr (GW54), and Mg–5Gd–0.4Zr (GW50) alloys after processing with two extrusion-ratios of 19:1 and 8:1. While the alloys show common extrusion textures at the low extrusion-ratio of 8:1, an unusual extrusion texture is observed in the GW94 alloy at the high extrusion-ratio of 19:1 with the (0001) basal planes aligned perpendicular to the extrusion axis. This unusual texture decreases at lower extrusion-ratios and/or lower alloy contents. It is proposed that rare-earth (RE) elements modify the texture by retarding recrystallization in solute drag effects on grain boundaries and pinning effects of RE-rich precipitates.
- Published
- 2016
30. Beam matching: A method to study phonon transport through interfaces and multilayer structures
- Author
-
Debanjan Basu and Peter E. Blöchl
- Subjects
Coupling ,Materials science ,Condensed matter physics ,Scattering ,Phonon ,02 engineering and technology ,Surfaces and Interfaces ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Condensed Matter::Materials Science ,Thermal conductivity ,Condensed Matter::Superconductivity ,0103 physical sciences ,Materials Chemistry ,Perpendicular ,Condensed Matter::Strongly Correlated Electrons ,Transmission coefficient ,Electrical and Electronic Engineering ,010306 general physics ,0210 nano-technology ,Electronic band structure ,Complex plane - Abstract
authoren Abstractauthoren Structuring materials is one mechanism to influence the thermal conductivity and thus thermoelectric efficiency. In order to investigate the scattering of phonons in multilayer structures we developed a beam matching technique, which is based on the concept of individual phonons and their scattering at interfaces. One of the major goals is to efficiently determine the complex band structure of the bulk materials. The complex band structure is determined using selected k-points on a triangulated grid in the complex plane of wave vectors perpendicular to the interface. Matching the phonon modes at an interface is translated to a singular value problem. Its null-vectors provide the coupling coefficients of the phonon modes across the interface. Besides giving explicit access to the modes as they scatter at the interface, the technique provides the transfer matrices, that provide the transmission coefficient of any multilayer structure. The transmission coefficient, in turn, yields the phononic thermal conductance for coherent transport. The knowledge of the matched phonons forms the basis of investigating incoherent transport under the influence of phonon–phonon or impurity scattering.
- Published
- 2015
31. Network Mesh Nanostructures in Cross‐Linked Poly(Dimethylsiloxane) Visualized by AFM
- Author
-
Viktoriia Drebezghova, Mark A. Hempenius, Corinne Nardin, G. Julius Vancso, Hubert Gojzewski, Ahmed Allal, Institut des sciences analytiques et de physico-chimie pour l'environnement et les materiaux (IPREM), Université de Pau et des Pays de l'Adour (UPPA)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), University of Twente [Netherlands], and Materials Science and Technology of Polymers
- Subjects
Materials science ,Nanostructure ,mesh nanostructure ,Polymers and Plastics ,Mesh networking ,UT-Hybrid-D ,02 engineering and technology ,010402 general chemistry ,Elastomer ,01 natural sciences ,Stress (mechanics) ,speak force AFM ,Polymer chemistry ,Materials Chemistry ,Perpendicular ,Peak force AFM ,Physical and Theoretical Chemistry ,Composite material ,Nanoscopic scale ,elastomers ,Organic Chemistry ,technology, industry, and agriculture ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,0104 chemical sciences ,[CHIM.POLY]Chemical Sciences/Polymers ,poly(dimethylsiloxane) ,Free surface ,Mesh nanostructures ,mesh deformation ,Deformation (engineering) ,0210 nano-technology - Abstract
International audience; Mesh network structures are visualized by peak force tapping atomic force microscopy on cross-linked poly(dimethylsiloxane) (PDMS) at the nanometer length scale. The images directly capture network mesh structures with mesh diameter values, from 10 to 16 nm at the free surface of PDMS. Perpendicular to the free surface, in cross-sectional areas exposed by cryo-fracturing, similar mesh structures are observed. When exposed to uniaxial stress, the circular mesh features become elongated, showing network deformation at the nanoscale, as a result of mechanical stress. Following Soxhlet solvent extraction the mesh-like appearance remains unchanged, but mesh diameter values decrease, which are attributed to the removal of non-crosslinked chains and silica filler.
- Published
- 2020
32. External‐Field‐Free Spin Hall Switching of Perpendicular Magnetic Nanopillar with a Dipole‐Coupled Composite Structure
- Author
-
Mahdi Jamali, Jian-Ping Wang, Smith Angeline K, and Zhengyang Zhao
- Subjects
Magnetoresistive random-access memory ,Materials science ,Condensed matter physics ,Spintronics ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Nanomagnet ,0104 chemical sciences ,Electronic, Optical and Magnetic Materials ,Magnetic field ,Dipole ,Spin Hall effect ,Perpendicular ,0210 nano-technology ,Nanopillar - Abstract
Spin Hall effect (SHE) induced reversal of perpendicular magnetization has attracted significant interest, due to its potential to lead to low power memory and logic devices. However, the switching requires an assisted in-plane magnetic field, which hampers its practical applications. Here, we introduce a novel approach for external-field-free spin Hall switching of a perpendicular nanomagnet by utilizing a local dipolar field arising from an adjacent in-plane magnetic layer. Robust switching of perpendicular CoFeB nanopillars in a dipole-coupled composite stack is experimentally demonstrated in the absence of any external magnetic field, in consistent with the results of micromagnetic simulation. Large in-plane compensation field of about 135 Oe and out-of-plane loop shift of about 45 Oe / 10 7 A cm-2 are obtained in the nanopillar devices with composite structure. By performing micromagnetic simulations, we confirm the composite external-field-free switching strategy can also work for a 10 x 10 nm2 circular pillar. Compared with other proposed methods for external-field-free spin Hall switching of perpendicular magnetization, the dipole-coupled composite structure is compatible with a wide range of spin Hall systems and perpendicular magnetic tunnel junctions, paving the way towards practical SHE-based MRAM and logic applications.
- Published
- 2020
33. Perpendicular MXene Arrays with Periodic Interspaces toward Dendrite‐Free Lithium Metal Anodes with High‐Rate Capabilities
- Author
-
Di Zhang, Hao Chen, Zhiguo Du, Shuai Wang, Qi Zhu, Bin Li, Shubin Yang, and Zhenjiang Cao
- Subjects
Biomaterials ,High rate ,Dendrite (crystal) ,Materials science ,Electrochemistry ,Perpendicular ,Composite material ,Lithium metal ,Condensed Matter Physics ,MXenes ,Electronic, Optical and Magnetic Materials ,Anode - Published
- 2019
34. Current and field driven domain wall motion under influence of the Dzyaloshinsky-Moriya interaction
- Author
-
Robert Wieser
- Subjects
Physics ,Field (physics) ,Condensed matter physics ,Dynamics (mechanics) ,Condensed Matter Physics ,01 natural sciences ,010305 fluids & plasmas ,Electronic, Optical and Magnetic Materials ,Transverse plane ,Magnetic anisotropy ,Domain wall (magnetism) ,0103 physical sciences ,Domain (ring theory) ,Perpendicular ,Condensed Matter::Strongly Correlated Electrons ,010306 general physics ,Anisotropy - Abstract
A complete analytical description of the dynamics of current and field driven transverse domain walls under the influence of the Dzyaloshinsky–Moriya interaction using the q– model will be given. Five different scenarios will be observed where the Dzyaloshinsky–Moriya vector is either parallel or perpendicular to the easy axis anisotropy of the system and a direct reversal, respectively, precessional motion will be assumed.
- Published
- 2015
35. Doping efficiency and limits in (Mg,Zn)O:Al,Ga thin films with two-dimensional lateral composition spread
- Author
-
Steffen Richter, Rüdiger Schmidt-Grund, Michael Lorenz, Abdurashid Mavlonov, Marius Grundmann, Jörg Lenzner, and Holger von Wenckstern
- Subjects
Materials science ,Dopant ,Doping ,Analytical chemistry ,Surfaces and Interfaces ,Condensed Matter Physics ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Pulsed laser deposition ,Materials Chemistry ,Perpendicular ,Sapphire ,Degradation (geology) ,Electrical and Electronic Engineering ,Thin film ,Deposition (law) - Abstract
We have investigated structural, optical, and electrical properties of MgZnO:(Al/Ga) thin films in dependence on Mg and Al/Ga concentrations. For this purpose, thin films with two perpendicular, lateral composition gradients, i.e., the Mg composition is varied in one direction whereas the Al/Ga concentration is varied in a perpendicular direction were grown at by pulsed-laser deposition (PLD) using a threefold segmented PLD target and 2-inch in diameter c-plane sapphire substrates. It has been found that compensation by intrinsic acceptors limits efficient doping to dopant concentrations of about . Further, the electrical data suggests, that the compensating defect is doubly chargeable hinting to the zinc vacancy as microscopic origin. Increasing the dopant concentration above leads to a degradation of electrical and structural properties.
- Published
- 2015
36. Elucidating the Morphological Complexities of Linear Symmetric Triblock Polymers Confined Between Two Parallel Plates: A Self-Consistent Field Theoretic Approach
- Author
-
Bamin Khomami and Mouge Mohagheghi
- Subjects
chemistry.chemical_classification ,Materials science ,Morphology (linguistics) ,Polymers and Plastics ,Organic Chemistry ,Nanotechnology ,Substrate (electronics) ,Polymer ,Condensed Matter Physics ,Surface energy ,Inorganic Chemistry ,Core (optical fiber) ,Lamella (surface anatomy) ,chemistry ,Chemical physics ,Materials Chemistry ,Perpendicular ,Thin film - Abstract
Three dimensional self-consistent field theoretic simulations have been performed to determine the equilibrium morphologies formed by linear ABC triblock polymer melts confined between two parallel plates that favor the middle block. Our primary goal is to elucidate the conditions under which the perpendicular lamella is stabilized, since this morphology plays a central role in many nanotechnology applications. Key factors, namely, the chain architecture, surface energy and the mismatch between the film thickness d and the bulk lamella period, L0, determine the final morphologies, e.g., perpendicular and parallel lamella, perforated lamella and wet substrate with parallel cylinders in the core, have been identified. Overall, our findings are fully consistent with the results of limited experimental studies focused on morphology development in thin films of triblock polymer melts. Finally, we have clearly demonstrated that ABC triblocks hold technological advantages over diblocks for nano-lithographic fabrications.
- Published
- 2015
37. Photodetachment of hydrogen negative ion near inelastic surfaces: Arbitrary laser polarization direction
- Author
-
Afaq Ahmad, Azmat Iqbal, and Raja J. Amjad
- Subjects
Physics ,Hydrogen ,Oscillation ,chemistry.chemical_element ,Semiclassical physics ,Condensed Matter Physics ,Atomic and Molecular Physics, and Optics ,Ion ,Cross section (physics) ,Amplitude ,chemistry ,Perpendicular ,Physics::Atomic Physics ,Physical and Theoretical Chemistry ,Atomic physics ,Reflection coefficient - Abstract
The photodetachment of hydrogen negative ion near different inelastic surfaces is investigated by the semiclassical closed orbit theory for arbitrary laser polarization direction . A two-term formula of photodetachment cross section consisting of a smooth background term and an oscillatory term is derived. The oscillatory term contains an extra angular factor that describes the dependence of oscillations in total cross section on the laser polarization direction. It is observed that the amplitude of oscillations in cross section reaches maximum at when laser polarization is parallel to the z-axis and it approaches zero as the laser polarization direction becomes perpendicular to the z-axis. It is also observed that as the reflection coefficient , which accounts for the inelastic behavior of the surfaces, increases the amplitude of oscillation also increases. © 2015 Wiley Periodicals, Inc.
- Published
- 2015
38. Nanoparticle-Structured Highly Sensitive and Anisotropic Gauge Sensors
- Author
-
Jin Luo, Wei Zhao, Yvonne Xu, Shiyao Shan, Susan Lu, Chuan-Jian Zhong, Kelly Cartwright, Jack P. Lombardi, and Mark D. Poliks
- Subjects
Materials science ,Condensed matter physics ,Orders of magnitude (temperature) ,Metal Nanoparticles ,Nanoparticle ,Nanotechnology ,Biosensing Techniques ,General Chemistry ,Gauge (firearms) ,Biomaterials ,Percolation ,Perpendicular ,Anisotropy ,General Materials Science ,Gold ,Deformation (engineering) ,Thin film ,Biotechnology - Abstract
The ability to tune gauge factors in terms of magnitude and orientation is important for wearable and conformal electronics. Herein, a sensor device is described which is fabricated by assembling and printing molecularly linked thin films of gold nanoparticles on flexible microelectrodes with unusually high and anisotropic gauge factors. A sharp difference in gauge factors up to two to three orders of magnitude between bending perpendicular (B(⊥)) and parallel (B(||)) to the current flow directions is observed. The origin of the unusual high and anisotropic gauge factors is analyzed in terms of nanoparticle size, interparticle spacing, interparticle structure, and other parameters, and by considering the theoretical aspects of electron conduction mechanism and percolation pathway. A critical range of resistivity where a very small change in strain and the strain orientation is identified to impact the percolation pathway in a significant way, leading to the high and anisotropic gauge factors. The gauge anisotropy stems from molecular and nanoscale fine tuning of interparticle properties of molecularly linked nanoparticle assembly on flexible microelectrodes, which has important implication for the design of gauge sensors for highly sensitive detection of deformation in complex sensing environment or on complex curved surfaces such as wearable electronics and skin sensors.
- Published
- 2015
39. Epitaxial growth of strained Mn5Ge3nanoislands on Ge(001)
- Author
-
Lisa Michez, Aurélie Spiesser, Sion F. Olive Méndez, and Vinh LeThanh
- Subjects
Materials science ,Condensed matter physics ,Magnetometer ,Condensed Matter Physics ,Epitaxy ,Electronic, Optical and Magnetic Materials ,law.invention ,Magnetic anisotropy ,Magnetization ,Electron diffraction ,law ,Perpendicular ,Curie temperature ,Molecular beam epitaxy - Abstract
We report on the epitaxial growth of Mn5Ge3 on Ge(001) by molecular beam epitaxy using solid phase epitaxy method. Mn5Ge3 grows as nanoislands, which are randomly distributed over the substrate surface. Select area electron diffraction analysis was used to determine the epitaxial relationship Mn5Ge3(001)[110]//Ge(001)[110], as well as to detect an induced tensile strain along [110] Mn5Ge3 direction to fit the Ge lattice, while the observation of Moire patterns indicates a complete relaxation along the direction. In-plane and out-of-plane M(H) loops were obtained at 200 K using a vibrating sample magnetometer, it was found that the easy axis of magnetization is perpendicular to the substrate surface and that the crystal magnetic anisotropy is K1 = 9.27 × 105 erg cm−3. The enhancement of the Curie temperature of the nanoislands ∼340 K, which is higher than 296 K of the bulk Mn5Ge3, is attributed to the induced strains.
- Published
- 2015
40. Anisotropy of Unsaturated Layered Soils: Impact of Layer Composition and Domain Size
- Author
-
Jianting Zhu and Peng Deng
- Subjects
Capillary pressure ,Hydraulic head ,Materials science ,Condensed matter physics ,Perpendicular ,Soil Science ,Geotechnical engineering ,Layering ,Saturation (chemistry) ,Anisotropy ,Bulk density ,Arithmetic mean - Abstract
Soils commonly exhibit hydraulic anisotropy under field conditions due to layering. Previous studies on saturation-dependent anisotropy were mostly focused on the impact of saturation degree, bulk density, and soil texture. In this study, the impact of layer composition and domain size on the anisotropy of unsaturated soils was investigated. We applied the same capillary pressure at top and bottom of the layered domain to simulate a mean unit hydraulic gradient condition and determined the anisotropy factor by the ratio of fluxes in the directions parallel and perpendicular to the layering. The anisotropy factors were then examined in relation to the layer composition, domain size, and mean capillary pressure for both two- and three-layer formations. In addition, the performance of the conveniently used conceptual anisotropy based on the harmonic and arithmetic mean hydraulic conductivities was also investigated for comparison. The maximum anisotropy is reached when the more permeable layer thickness is
- Published
- 2015
41. Torrent Frog-Inspired Adhesives: Attachment to Flooded Surfaces
- Author
-
Luis García-Fernández, W. J. P. Barnes, Jagoba Iturri, Longjian Xue, Michael Kappl, Aránzazu del Campo, and Hans-Jürgen Butt
- Subjects
musculoskeletal diseases ,Long axis ,Materials science ,Polydimethylsiloxane ,Edge density ,Hexagonal crystal system ,Pillar ,Condensed Matter Physics ,Electronic, Optical and Magnetic Materials ,body regions ,Biomaterials ,chemistry.chemical_compound ,chemistry ,Bending stiffness ,Electrochemistry ,Perpendicular ,Adhesive ,Composite material - Abstract
Anatomic differences on the toe pad epithelial cells of torrent and tree frogs (elongated versus regular geometry) are believed to account for superior ability of torrent frogs to attach to surfaces in the presence of running water. Here, the friction properties of artificial hexagonal arrays of polydimethylsiloxane (PDMS) pillars (elongated and regular) in the presence of water are compared. Elongated pillar patterns show significantly higher friction in a direction perpendicular to the long axis. A low bending stiffness of the pillars and a high edge density of the pattern in the sliding direction are the key design criteria for the enhanced friction. The elongated patterns also favor orientation-dependent friction. These findings have important implications for the development of new reversible adhesives for wet conditions.
- Published
- 2015
42. Stretchable Conductive Composites Based on Metal Wools for Use as Electrical Vias in Soft Devices
- Author
-
George M. Whitesides, Stephen A. Morin, Alok S. Tayi, Christoph Keplinger, and Joshua Aaron Lessing
- Subjects
chemistry.chemical_classification ,Materials science ,Composite number ,Soft robotics ,Steel wool ,Polymer ,Condensed Matter Physics ,Elastomer ,Electronic, Optical and Magnetic Materials ,Biomaterials ,chemistry ,Electrochemistry ,Perpendicular ,Electrical wiring ,Composite material ,Strain gauge - Abstract
Soft devices can be bent, stretched, and compressed reversibly, but conventional wires are rigid. This work describes stretchable composites that are easily fabricated with simple tools and commodity materials, and that can provide a strategy for electrical wiring that meets certain needs of soft devices. These composites are made by combining metal wool and elastomeric polymers. Embedding fi ne (average fi ber width ≈25 µm) steel wool (or other metal wools) in a silicone polymer creates an electrically conductive path through the nonconductive elastomer. This composite is fl stretchable, compressible, inexpensive, and simple to incorporate into the bodies of soft devices. It is also electrically anisotropic, and shows maximum conductivity along the majority axis of the fi bers, but maximum extension perpendicular to this axis. The utility of this composite for creating an electrically conductive path through an elastomer was demonstrated in several devices, including: a soft, solderless breadboard, a soft touch sensor, and a soft strain gauge.
- Published
- 2015
43. Selective area growth of Ga-polar GaN nanowire arrays by continuous-flow MOVPE: A systematic study on the effect of growth conditions on the array properties
- Author
-
Pierre-Marie Coulon, Blandine Alloing, Jesús Zúñiga-Pérez, Sébastien Chenot, Denis Lefebvre, and Virginie Brandli
- Subjects
Materials science ,business.industry ,Nanowire ,Nanotechnology ,Condensed Matter Physics ,Epitaxy ,Electronic, Optical and Magnetic Materials ,Volumetric flow rate ,Homogeneity (physics) ,Perpendicular ,Optoelectronics ,Polar ,Growth rate ,Metalorganic vapour phase epitaxy ,business - Abstract
Site-controlled growth of GaN nanowires (NWs) on GaN-on-sapphire templates with a patterned SiN mask has been carried out by metalorganic vapor phase epitaxy using a continuous-flow growth mode. A low V/III ratio compared to that used for GaN layer growth, combined with low precursor flow rates for both Ga and N precursors, has been used to promote the nanowire growth on Ga-polar substrates. The lateral growth rate, that is, perpendicular to the c-axis, could be further controlled using appropriate growth temperatures and H2/N2 ratios. Besides, the influence of the pattern geometry on the nanowire aspect ratio and size homogeneity has been addressed.
- Published
- 2015
44. Twinning in GaAs nanowires on patterned GaAs(111)B
- Author
-
Thomas Walther and Andrey B. Krysa
- Subjects
Materials science ,business.industry ,Electron energy loss spectroscopy ,Nanowire ,General Chemistry ,Condensed Matter Physics ,Epitaxy ,Crystallography ,Transmission electron microscopy ,Scanning transmission electron microscopy ,Perpendicular ,Optoelectronics ,General Materials Science ,business ,Crystal twinning ,Plasmon - Abstract
We have studied twinning in GaAs nanowires grown via holes in a silica mask deposited on GaAs(111)B substrates by metal-organic chemical vapour epitaxy without catalysts. Twins perpendicular to the growth direction form in the nanowires, their {111}-type side facets leading to corrugation of their {110} side walls. The top facets are almost atomically smooth. Aberration corrected annular dark-field scanning transmission electron microscopy reveals all twins are rotational, commencing with layers of Ga and finishing with As atoms. Energy-loss spectroscopic profiling has shown no significant changes in the band-gap or bulk plasmon energy at those twin boundaries, and the observed reduction of the interface plasmon energy by ∼0.13 eV is close to the detection limit of the technique, reflecting the very low energetic electronic changes related to twin formation.
- Published
- 2014
45. A Top Coat with Solvent Annealing Enables Perpendicular Orientation of Sub-10 nm Microdomains in Si-Containing Block Copolymer Thin Films
- Author
-
Caroline A. Ross, Jeong Gon Son, Wonjung Kim, Eunjin Kim, and Kwang Hee Lee
- Subjects
Materials science ,Annealing (metallurgy) ,Flory–Huggins solution theory ,Condensed Matter Physics ,Polyvinyl alcohol ,Surface energy ,Electronic, Optical and Magnetic Materials ,Biomaterials ,chemistry.chemical_compound ,Chemical engineering ,chemistry ,Polymer chemistry ,Electrochemistry ,Perpendicular ,Copolymer ,Self-assembly ,Thin film - Abstract
Achieving sub-10 nm high-aspect-ratio patterns from diblock copolymer self-assembly requires both a high interaction parameter (χ, which is determined by the incompatibility between the two blocks) and a perpendicular orientation of microdomains. However, these two conditions are extremely difficult to achieve simultaneously because the blocks in a high-χ copolymer typically have very different surface energies, favoring in-plane microdomain orientations. A fully perpendicular orientation of a high-χ block copolymer, poly(styrene-block-dimethylsiloxane) (PS-b-PDMS) is realized here using partially hydrolyzed polyvinyl alcohol (PVA) top coats with a solvent annealing process, despite the large surface energy differences between PS and PDMS. The PVA top coat on the block copolymer films under a solvent vapor atmosphere significantly reduces the interfacial energy difference between two blocks at the top surface and provides sufficient solvent concentration gradient in the through-thickness direction and appropriate solvent evaporation rates within the film to promote a perpendicular microdomain orientation. The effects of interfacial energy differences and the swellability of PVA top coats controlled by the degree of hydrolysis on the orientation of microdomains are examined. The thickness of the BCP film and top coats also affects the orientation of the BCP film.
- Published
- 2014
46. Investigation of mixing effects of silicon isotopes under shave-off condition using atom probe tomography
- Author
-
Makiko Fujii, Masato Morita, Satoshi Ishimura, Yoko Kawamura, Hiroshi Uchida, Masanobu Karasawa, Norihito Mayama, Kohei M. Itoh, and Masanori Owari
- Subjects
integumentary system ,Ion beam ,Chemistry ,business.industry ,Surfaces and Interfaces ,General Chemistry ,Atom probe ,Condensed Matter Physics ,Focused ion beam ,Surfaces, Coatings and Films ,law.invention ,Ion ,Molecular dynamics ,Optics ,law ,Materials Chemistry ,Perpendicular ,Mixing effect ,Isotopes of silicon ,business - Abstract
Shave-off depth profiling uses a Ga focused ion beam micro-machining process to provide highly precise depth profiles with nanometer-scale resolution. This method is a very unique process for acquiring a depth profile using the shave-off scan mode, in which the primary ion beam perpendicular to the direction of depth irradiates the sample. In our previous study, we confirmed by molecular dynamics simulation that the shave-off scan mode has a low mixing effect compared with the conventional scan mode, which uses the normal incident angle. However, the current understanding of measurement using the shave-off scan mode is insufficient. In this study, in order to estimate the sample damage in the shave-off scan mode, we investigated the degree of mixing effects after the primary ion bombardment under shave-off conditions using atom probe tomography. To evaluate the mixing effects, the intermixing of silicon isotope multilayers induced by ion beam irradiation was investigated. The depth of the damage from the sample surface caused by Ga focused ion beams was analyzed for both the shave-off scan mode and the conventional scan mode using the normal incident angle. Results showed that the shave-off scan mode has a significantly smaller mixing effect thanthe conventionalscanmode. Inaddition, results showed that the attenuations of the damage and the Ga concentration exhibited almost the same tendency. Copyright © 2014 John Wiley & Sons, Ltd.
- Published
- 2014
47. Use of tunable second-harmonic signal from KNbO3 nanoneedles to find optimal wavelength for deep-tissue imaging
- Author
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Fuhong Cai, Sailing He, Zhong Chen, Ye Wang, Jingyun Huang, Jiaxin Yu, Zhizhen Ye, and Jun Qian
- Subjects
Materials science ,business.industry ,Nonlinear optics ,Condensed Matter Physics ,Ray ,Signal ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials ,Wavelength ,Cardinal point ,Optics ,Harmonic ,Perpendicular ,Optoelectronics ,business ,Nanoneedle - Abstract
Nonlinear optical (NLO) responses of perovskite-type nanostructures have a variety of potential applications owing to the highly efficient frequency conversion guaranteed by both the material itself and the nanometer-scale configuration. KNbO3 (KN) nanoneedles have been identified as a promising NLO material because of the superior broadband frequency conversion efficiency, and if incident light is propagating in a direction perpendicular to the axis of a nanoneedle, then the phase-matching constraint can be relaxed. Here, the second-harmonic generation (SHG) and third-harmonic generation (THG) responses of both individual and clustered KN nanoneedles are reported. Based on these results, a novel method is proposed for determining the optimal excitation wavelength for NLO imaging of several biological samples, with KN nanoneedles acting as NLO agents. The method is shown to provide the optical features in the focal plane and a more reliable estimation of the optimal excitation wavelength for deep-tissue imaging.
- Published
- 2014
48. Surface topology caused by dislocations in polar, semipolar, and nonpolar InGaN/GaN heterostructures
- Author
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Markus Weyers, Tim Wernicke, Michael Kneissl, Ulrich T. Schwarz, J. Raß, Simon Ploch, and Lukas Schade
- Subjects
Materials science ,Condensed matter physics ,business.industry ,Hexagonal crystal system ,Heterojunction ,Surfaces and Interfaces ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,Condensed Matter Physics ,Surface (topology) ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Condensed Matter::Materials Science ,Materials Chemistry ,Perpendicular ,Optoelectronics ,Polar ,Electrical and Electronic Engineering ,business ,Striation ,Quantum well ,Hillock - Abstract
The impact of dislocations on surface topology as well as on quantum well emission in c-plane, semipolar, and nonpolar InGaN/GaN heterostructures is being analyzed by micro-photoluminescence and white-light-interferometry. V-pits with (101) and (10) side facets are identified in a (102) semipolar heterostructure. Hillocks formed by spiral growth around screw dislocations change from hexagonal to triangular to rectangular shape in polar, semipolar, and nonpolar heterostructures, respectively, reflecting the symmetry of the individual surface. The emission in semipolar quantum wells, grown homoepitaxially on bulk GaN substrates, show dark stripes aligned with misfit dislocations. For (112) and (201) orientation, these dark stripes are perpendicular and parallel, respectively, to surface striation.
- Published
- 2014
49. Defect-Tolerant Nanocomposites through Bio-Inspired Stiffness Modulation
- Author
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S. Shiva P. Nathamgari, Zhi An, Horacio D. Espinosa, SonBinh T. Nguyen, Allison M. Beese, and Sourangsu Sarkar
- Subjects
Materials science ,Nanocomposite ,Graphene ,Linear elasticity ,Oxide ,Stiffness ,Condensed Matter Physics ,Electronic, Optical and Magnetic Materials ,law.invention ,Biomaterials ,chemistry.chemical_compound ,chemistry ,Deflection (engineering) ,law ,Ultimate tensile strength ,Electrochemistry ,Perpendicular ,medicine ,Composite material ,medicine.symptom - Abstract
A biologically inspired, multilayer laminate structural design is deployed into nanocomposite films of graphene oxide-poly(methyl methacrylate) (GO-PMMA). The resulting multilayer GO-PMMA films show greatly enhanced mechanical properties compared to pure-graphene-oxide films, with up to 100% increases in stiffness and strength when optimized. Notably, a new morphology is observed at fracture surfaces: whereas pure-graphene-oxide films show clean fracture surfaces consistent with crack initiation and propagation perpendicular to the applied tensile load, the GO-PMMA multilayer laminates show terracing consistent with crack stopping and deflection mechanisms. As a consequence, these macroscopic GO-PMMA films become defect-tolerant and can maintain their tensile strengths as their sample volumes increase. Linear elastic fracture analysis supports these observations by showing that the stiffness modulation introduced by including PMMA layers within a graphene oxide film can act to shield or deflect cracks, thereby delaying failure and allowing the material to access more of its inherent strength. Together, these data clearly demonstrate that desirable defect-tolerant traits of structural biomaterials can indeed be incorporated into graphene- oxide-based nanocomposites.
- Published
- 2014
50. Numerical simulation of heat conduction in a random ballistic deposited grain aggregate
- Author
-
Sin-iti Sirono
- Subjects
Geophysics ,Thermal conductivity ,Materials science ,Aggregate (composite) ,Condensed matter physics ,Space and Planetary Science ,Perpendicular ,Deposition (phase transition) ,Anisotropy ,Thermal conduction ,Atomic packing factor ,Exponential function - Abstract
A numerical simulation of heat conduction in a grain aggregate is carried out to determine the packing fraction (the spatial fraction occupied by grains or 1-porosity) dependence of the thermal conductivity of the aggregate. Arrangements of grains are given by random ballistic deposition. It is found that the packing fraction dependence is well approximated by an exponential function. The number of contacts between grains is the crucial quantity in the conduction, and its packing fraction dependence is exponential. Heat conduction is found to be anisotropic, where the conduction along the deposition direction is more efficient than that perpendicular to the deposition direction.
- Published
- 2014
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