We show theoretically how constant-energy maps of the angle-resolved photoemission intensity can be used to test wave function symmetry in graphene. For monolayer graphene, we demonstrate that the observed anisotropy of ARPES spectra is a manifestation of what has been recently branded as electronic chirality. For bilayer graphene, we show that the anisotropy of the constant-energy maps may be used to extract information about the magnitude and sign of interlayer coupling parameters and about symmetry breaking inflicted on a bilayer by the underlying substrate.
Highly [100]-axis oriented single-phase Na0.5K0.5NbO3 (NKN) thin films have been grown on polycrystalline Pt80Ir20 (Pt) and SiO2 (native oxide)/Si (111) substrates using KrF excimer laser ablation of a stoichiometric ceramic target. X-ray diffraction θ–2θ scan and rocking curve data are evidence of the strong effect of film self-assembling along the [100] direction regardless of the substrate texture. Furthermore, multiple-cell structuring along the polar axis has been observed in NKN films grown onto the Pt substrate. Ferroelectric measurements yield remnant polarization Pr of 10 μC/cm2 and spontaneous polarization Ps of 17.5 μC/cm2 at 80 kV/cm. The electrical resistivity of the Na0.5K0.5NbO3 film was in the order of 1010 Ω cm at 10 kV/cm. Dielectric permittivity ε′ and dissipation factor tan δ have been found to vary 480–440 and 0.028–0.024, respectively, in the frequency range 0.4–100 kHz.
Epitaxial ferroelectric/giant magnetoresistive Pb(Zr0.52Ti0.48)O3/La0.67Ca0.33MnO3 (PZT/LCMO) heterostructures have been grown onto LaAlO3 (001) single crystal by KrF pulsed laser deposition. Main processing parameters have been optimized to preserve giant magnetoresitivity in the LCMO film after deposition of the top ferroelectric layer. High degree of c-axis orientation and strong in-plane texture, coherent with the substrate, both in template LCMO and PZT layers, high dielectric permittivity of 720, remnant polarization of 17 μC/cm2 of PZT, and magnetoresistivity in LCMO of 28% at H=0.5 T indicate excellent characteristics of coexisting magnetoresistive and ferroelectric properties. We compare the performance of magnetosensitive memory cells with La0.67Ca0.33MnO3 and La0.75Sr0.25MnO3 giant magnetoresistive electrodes.
The long-standing goal of computer aided design (CAD)/computer aided engineering (CAE) integration demands seamless interfaces between geometric design and engineering analysis/simulation tasks. The key challenge to this integration stems from the distinct and often incompatible roles geometric representations play, respectively, in design and analysis. This paper critically examines and compares known mesh-based and meshfree approaches to CAD/CAE integration, focusing on the basic tasks and components required for building fully integrated engineering applications. For each task, we identify the fundamental requirements and challenges and discuss how they may be met by known techniques and proposed solutions.
Perfectly c-axis oriented micrometer thick Na0.5K0.5NbO3(NKN) films have been prepared on a thermally grown ultrathin SiO2 template layer onto a Si(001) wafer by the pulsed laser deposition technique. A x-ray diffraction θ–2θ scan reveals multiple-cell structuring of single phase NKN film along the polar axis, while films grown onto amorphous ceramic (Corning) glass show a mixture of slightly c-axis oriented NKN and pyrochlore phases. This implies a small amount of SiO2 crystallites distributed in an amorphous matrix inherit Si(001) orientation and promotes highly oriented NKN film growth. NKN film dielectric permittivity ε′ was found to vary from 114.0 to 107.2 in the frequency range 1 kHz–1 MHz, while the resistivity was on the order of 2.6×1010 Ω cm @ 20 kV/cm. The planar interdigital variable reactance device (varactor) based on the NKN/SiO2/Si thin film structure possesses a dissipation factor of 0.8% at 1 MHz and zero bias, electrical tunability of 3.1%, and nA order leakage current at 20 V bias at room temperature.
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