The first-principles numerical simulation is employed to calculate the effect of replacement of carbon and silicon with boron on the electronic structure and optical properties of β-SiC. Mulliken analysis shows that the B impurity bond lengths shrink in the case of BSi, while they expand with reference to BC. In addition, BSi contains C—C, Si—Si and B—Si bonds. The calculated results show that the two systems of BC and BSi apply different dispersion. BC is in accordance with the Lorentz dispersion theory while BSi follows the Drude dispersion theory. Theoretic analysis and quantitative calculation are used for conductivity spectra in the infrared region.
Biosensors have proved immensely useful in numerous vital areas for detection and testing. Here, a novel plasmonic nanosensor, based on loaded slot cavity, is proposed and studied. We conduct a detailed analysis of the influence of the load's parameters on the transmission characteristics based on the finite element method and surface charge and current model. Simulation results reveal that the existence of the load can cause the resonant wavelength to have a linear or nonlinear red shift, and yield an enhanced plasmonic nanosensor with sensitivity about ${S}={2900}$ nm/RIU and a detection limit about 1 $\times \,\,10^{\text {-3}}$ . In addition, the proposed structure is well used in actual biosensing for blood plasma concentration, glucose concentration, ethanol temperature and diseased cell detection with high sensitivity. Finally, an extended structure with detuned loaded slot cavities is proposed to realize PIT/multi-PIT and slow light effect. The special features of our proposed structure are applicable in the realization of various integrated components for the development of high-performance plasmonic biosensor.
The highly localized field of the plasmonic nanostructures can amplify the chiroptical effects. While most efforts have been focused on spectral responses in real space for chiroptical effects of the plasmonic nanostructures, we present alternative extrinsic chiroptical effects with respect to angular emission patterns in momentum space based on the designed directional nanoantennas. First, the chiroptical effects with respect to spectral responses for the antenna are investigated and decomposed based on the multipolar expansion method. Through the traditional spectral responses, there seems to be no chirality. However, when we turn to the angular emission patterns in the momentum space for the nanoantenna, large local angular chiroptical effects are observed. The chiroptical effects assessed by the difference of azimuth angle emission lobes under left- and right-circularly polarized light illumination can reach 180°. The multipolar analysis combined with Green's function method in a stratified medium is constructed to explain the unidirectional emission and chiral phenomenon, which agrees well with the simulation results. Moreover, the local angular chiroptical effects are also highly tunable by changing the refractive index of the surrounding medium. Our study on local angular chiroptical effects provides a new perspective to understand the chirality, and the large extrinsic chirality for the nanoantenna sheds a new light for biosensing and chiral photon detection.
Abstract Pb 0.99 Nb 0.02 (Zr 0.85 Sn 0.13 Ti 0.02 )O 3 (PNZST) antiferroelectric (AFE) thick films are successfully deposited on silicon‐based Pt and LaNiO 3 electrodes by a sol‐gel method. The coexistence of ferroelectric (FE) and AFE phases are revealed in PNZST films by XRD, electric‐induced hysteresis loops, dielectric, and leakage current properties. Comparing with PNZST/Pt film, larger recoverable energy density and efficiency are obtained in PNZST/LaNiO 3 film due to the lower FE phase proportion. It is analyzed and demonstrated by a thermodynamic model of AFE and FE coexistence system. In addition, the fatigue behaviors of both AFE films are also affected by the proportion of the coexisting FE phase. PNZST/LaNiO 3 film exhibits good fatigue resistance on energy storage even after 10 10 switching cycles, which is attractive to pulsed power applications.
This paper presents a novel metamaterial constructed with wires, spheres and hollow slabs (WSHS), which simultaneously exhibits negative permittivity and permeability. An electromagnetic wave simulation is performed based on the proposed metamaterial and shows that a negative refractive index is achieved for this metamaterial. Adjusting the lattice constant of the unit cell is an easy way to manipulate the frequency of negative index of this structure. A left-hand material prism is designed composed of metamaterial unit cells and the simulation on the proposed prism proves the left-hand behavior of the designed metamaterial.
Electrical conductivity and dielectric parameters are general inherent features of materials. Controlling these characteristics through applied bias will add a new dimension to regulate the dynamic response of smart materials. Here, a fascinating electrical transport behavior is observed in topological insulator (TI) Bi2 Te3 nanorods, which will play a vital role in intelligent materials or devices as a unit for information reception, processing or feedback. The Bi2 Te3 nanorod aggregates exhibit a monotonic resistance response to voltage, with observed four-fold change of electrical conductivity in a small range electric field of 1 V mm-1 . The dielectric constant and dielectric loss of Bi2 Te3 nanorod composites also show strong dependences on bias voltage due to the unique electrical transport characteristics. The unique voltage-controlled electrical responses are attributed to the change of Fermi levels within the band structure of disordered TI nanorods, which are non-parallel to the applied electric field. The excellent controllable inherent characteristics through electric field endows Bi2 Te3 nanomaterials bright prospects for applications in smart devices and resistive random access memories.
Topological insulators exhibit great potential in the fields of electronics and semiconductors for their gapless surface states. Intriguingly, most topological insulators are possibly excellent microwave-absorbing materials because of easy adjustment of electrical transport based on conducting surface states in the nanostructure. Herein, topological insulator Bi2Te3 nanosheets are synthesized by a simple solvothermal method. The material demonstrates a unique dielectric behavior based on conducting surface states, resulting in excellent microwave-absorbing performance. Benefiting from the outstanding impedance matching, Bi2Te3 nanosheets exhibit an ultrathin microwave absorption with the qualified frequency bandwidth of 3.0 GHz at only 0.77 mm thickness, which is thinner than other absorbers in reported references. Moreover, a strong reflection loss of -41 dB at 0.8 mm is achieved. The result provides a new approach for developing ultrathin microwave absorption materials at the submillimeter scale.
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