Despite intensive studies on Pb(Mg(1/3)Nb(2/3))O(3) (PMN) relaxor, understanding the exact nature of its giant dielectric response and of its physical ground state is a fundamental issue that has remained unresolved for decades. Here, we report a comprehensive study of PMN relaxor crystal, and show that (i) its anomalous dielectric behavior in a broad temperature range results from the reorientation of polarization in the crystal, and (ii) the PMN relaxor is essentially a nanosized ferroelectric material with multiscale inhomogeneities of domain structure in addition to the well-known inhomogeneities of chemical composition and local symmetry. Such inhomogeneities are believed to play a crucial role in producing the huge and enigmatic physical effects in relaxor system, and may be used to design other new systems with giant effects such as a relaxor system.
Photon emission spectra from submicron silver particles induced by an electron beam have been measured using a light detection system combined with a 200-kV transmission electron microscope. Multiple peaks appear in the spectra associated with collective plasmon excitations produced in the particles by the incident electrons. The wavelengths of these peaks are observed to shift towards larger values with increasing particle diameter, as predicted by Mie theory. Moreover, photon maps have been obtained in a scanning mode and they indicate that those peaks correspond to the multipole modes of electromagnetic oscillations in metallic spheres ͑Mie resonances͒. The spectral shape of the emission and the dependence on particle size, impact parameter, and electron energy are well explained from theoretical calculations of the photon emission probability derived from a fully retarded analytical treatment of the interaction of fast electrons with metallic spheres.
We study the plasmons confined at the gap between silver nanospheres and silver planar surfaces by means of angle- and space-resolved spectral cathodoluminescence. Plasmons in individual nanoparticles are excited by an electron beam, giving rise to light emission that is analyzed as a function of photon-energy, emission direction, and position of the beam spot. Gap plasmons are significantly red shifted due to the interaction between the particles and the metal substrate, and they are preferentially excited by positioning the beam close to the sphere centers, which results in an angular emission pattern similar to that of a dipole oriented along the surface normal. In contrast, weaker emission features are observed at higher-energies when the beam is grazing to the spheres, corresponding to the excitation of Mie plasmons like those of isolated particles, which display an angular pattern approximately mimicking a dipole parallel to the surface. Our measurements are in excellent agreement with simulations, thus providing useful insight into gap plasmons arising from the interaction between metal particles and metal substrates that are relevant for molecular sensing applications.
Transparent conducting polycrystalline Ga-doped ZnO (GZO) films with different thicknesses were deposited on glass substrates at a substrate temperature of 200 °C by ion-plating deposition with direct current arc-discharge. The dependences of crystal structure, electrical, and optical properties of the GZO films on thickness have been systematically studied. Optical response due to free electrons of the GZO films was characterized in the photon energy range from 0.73 to 3.8 eV by spectroscopic ellipsometry (SE). The free electron response was expressed by the simple Drude model combined with the Tauc–Lorentz model. From the SE analysis and the results of Hall measurements, electron effective mass, m∗, and optical mobility, μopt, of the GZO films were determined, based on the assumptions that the films are homogeneous and optically isotropic. By comparing the μopt and Hall mobility, μHall, an indication on the effect of ingrain and grain boundary scattering limiting the electron mobility has been obtained. Moreover, the variation in scattering mechanism causing thickness dependence of μHall was correlated with the development of polycrystalline grain structure.
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