Results 1 - 10 of 12960
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[en] Here, we report quantitative measurements of nanoscale permittivity and conductivity using tuning-fork (TF) based microwave impedance microscopy (MIM). The system is operated under the driving amplitude modulation mode, which ensures satisfactory feedback stability on samples with rough surfaces. The demodulated MIM signals on a series of bulk dielectrics are in good agreement with results simulated by finite-element analysis. Using the TF-MIM, we have visualized the evolution of nanoscale conductance on back-gated MoS2 field effect transistors, and the results are consistent with the transport data. Our work suggests that quantitative analysis of mesoscopic electrical properties can be achieved by near-field microwave imaging with small distance modulation.
[en] A new kind of metamaterial composed of metallic split-ring structure arranged in a two-dimensional array is designed, which shows the multipoles' resonances, especially the magnetic toroidal dipolar (MTD) resonance. The calculated scattering power proves that the resonance at 14.416 GHz is mainly excited by MTD response. Compared with the other two resonances excited by normal multipoles, MTD response has the strongest dependence on permittivity of substrate and background material, which has potential applications on permittivity sensor. (paper)
[en] Dielectric measurements of serum albumin and myoglobin in solutions of varying conductivities were performed. The results presented confirm that also for protein solutions, the Maxwell predictions of a threshold frequency in conducting materials holds. The threshold frequency of a serum albumin solution was experimentally determined. Attention should be recalled that, if the dielectric spectra of proteins solutions want to be measured, three distinct frequency regions are to be observed: a low frequency region, where the sample behaves like a conductor; an intermediate region centered around the threshold frequency, where the free charges partially screen the fixed ones; and a high frequency region where the sample behaves like a good dielectric. (author). 8 refs, 5 figs
[en] The EO10 cavity resonator technique was employed to measure the relative permittivity of corning 7070 glass at 3 GHz. xi was found to be 3.78 +- 0.08 while tan sigma was (2.29 +- 0.02) x 10-3
[en] Silver/silicon dioxide and gold/silicon multilayer imaging structures are shown to have subwavelength imaging performance. The influence of the duty cycle is presented. Imaging possibilities with a slab having isotropic negative effective dielectric constant is also explored. This system may be worthy of an experimental program to establish that subwavelength resolution is practical. Success will lead to a new class of imaging, memory, and interconnection structures
[en] Highlights: • Nano-Fe3O4/PANI composites have negative permittivity which is significantly affected with the nano-Fe3O4 content. • Improved structure model of “crystal-nano wire” is used to explain the generation mechanism of negative permittivity. • Negative dielectric phenomenon of nano-Fe3O4/PANI composites is explained from the point of structure.
[en] The purpose of this project was to better understand the 'Multiscale Dynamics of Relaxor Ferroelectrics'. The output of the project is summarized in the narrative. The results of the work were presented at a number of different conferences and four papers were written, the references to which are also indicated in the report and which have also been uploaded on e-link. The multiscale dynamics of relaxors was clearly identified in the three characteristic temperatures that were identified. In particular, we were the first group to identify an intermediate temperature, T*, at which the correlations between off-center ions in relaxor cross-over from being dynamic to being static and giving rise to the characteristic relaxor behavior in the dielectric constant. Other groups have now confirmed the existence of such an intermediate temperature. We also made and reported two other observations: (1) a coherent interference phenomena (EIT-like effect) near the transition of several relaxors, which provides information on the nature and mechanism of the transition; and (2) in a similar way, inelastic neutron scattering results were interpreted as resonant scattering of acoustic phonons by localized modes in polar nanodomains. In parallel with the neutron scattering work, we also developed a theory of the scattering of phonons by the above localized modes. The theoretical development is very formal at this point and did not allow an easy comparison with the experimental results. This work is in progress.
[en] The dielectric and electrical properties of the TlInS2 crystal implanted with protons (protons with the energy of 150 keV) were investigated both in the tetragonal c axis and in the direction perpendicular to this axis. It is shown that the numerical values of the permittivity and electrical conductivity increase sharply in the direction of the c axis and decrease in the direction perpendicular to this axis. The decrease in the anisotropy in the TlInS2 crystal under the influence of protons is associated with the amorphization of the crystal.