Zhong Zhiyong

Charge Transport and Electrical Properties in Poly(3-hexylthiophene) Polymer Layers

A systematic study of the charge transport and electrical properties in poly(3-hexylthiophene) (P3HT) polymer layers is performed. We demonstrate that the temperature-dependent current-voltage J(V, T) characteristics of hole-only devices based on P3HT can be accurately described using the recently introduced extended Gaussian disorder model (EGDM). A particular numerical method adopting the uneven discretization and Newton iteration method is used to solve the coupled equations describing the space-charge limited (SCL) current in conjugated polymers. For the polymer studied, we find the width of the density of states σ = 0.1 eV and the lattice constant a = 1.15 nm. Based on the numerical method and EGDM, we further calculate and analyze some important electrical properties for P3HT in detail, including the variation of current-voltage characteristics with the boundary carrier density and the distribution of charge-carrier density and electric field with the distance from interface.

Flexible tuning microwave permeability spectrum in [ferromagnet/antiferromagnet]n exchange-biased multilayer stack structure

NiFe/[IrMn/NiFe/IrMn]5/[NiFe/IrMn]4/NiFe structured exchange-biased multilayer films are designed and prepared by magnetron sputtering. The static and the microwave magnetic properties are systematically investigated. The results reveal that adding a partially pinned ferromagnetic layer can effectively broaden the ferromagnetic resonance linewidth toward the low frequency domain. Moreover, a wideband multi-peak permeability spectrum with a 3.1-GHz linewidth is obtained by overlapping the spectra of different partially pinned ferromagnetic layers and [antiferromagnet/ferromagnet/antiferromagnet]n stacks. Our results show that the linewidth of the sample can be feasibly tuned through controlling the proper exchange bias fields of different stacks. The designed multilayered thin films have potential application for a tunable wideband high frequency noise filter.

Theoretical Investigations on the Off-Center Displacement of Co2+ in SrO by Analyzing Its Anisotropic g Factors

The off-center displacement of Co2+ ion in SrO crystal is investigated by analyzing its anisotropic g factors gx, gy and gz through diagonalization of the 6 × 6 energy matrix within 4T1 ground state for a 3d7 ion under rhombic symmetry. In the matrix, the contributions from the admixtures of various J( = 1/2, 3/2, 5/2) states and the fourth-order term Dη of rhombic crystal-fields and the ligand orbitals and spin-orbit coupling interactions, which are usually ignored in the previous studies, are considered. Both g factors (gx = 4.172, gy = 5.004 and gz = 2.133) and the off-displacement value (ΔR ≈ 0.023 nm) show good agreement with the experimental data.

Electric and Magnetic Properties of a New Ferrite-Ceramic Composite Material

We have investigated a new ferrite-ceramic composite material with inductive and capacitive properties fabricated by a solid-state reaction method. We analyse the effects of the composite mechanism and microstructure on the magnetic and electric properties. The results show that the new materials can be used not only as inductor materials, but also as capacitor materials in the wide frequency range of 1 kHz-1.8 GHz. The real part of permeability of the composite material is between 10 and 5.6, the imaginary part of permeability is between 1.2 and 0.5, and the dielectric constant is about ten times larger than that of ordinary ferrite materials. It is suggested that the new composite materials will be widely used in anti-electromagnetic interference fields and radio frequency communication fields

Influence of structure of integrated optical thin-film filter on performance

Thermo-optic tunable thin-film filter based on Fabry-Perot (F-P) cavity structure is a very attractive alternative integrated optical device. In this simulation-based paper, the key performance of typical thermo-optic tunable F-P filter is discussed by analyzing the structure of Distributed Bragger Reflectors (DBR) and the thermo-optic property of cavity thin-film material. The results indicate a negative correlation between the number of DBR periodical layers and full width at half maximum (FWHM), and a proportional relation between thermal-optic coefficient of material and tuning range. In addition, the cavity is more sensitive to the optical property than the reflection layers according to the analysis of thickness error of the film. And to solve slow thermal response without incurring other performance loss, a novel structure of the suspended cavity is proposed, in which only the cavity is heated.

The fluorescence transformation characteristics research of the CsI(Tl) thin film

This article proposed a new X-ray detector structure using Al as the separation and protection material based on thin layer CsI(Tl) crystal arrays coupled CCD. In this paper, an improved physical model is established, based on which a comprehensive discussion was performed on transmission and conversion factor of various types of fluorescence throughout the process of excitation and transfer. The results showed that, the crystal columns best diameter is generally in 10um magnitudes.

Influences of Bi2O3/V2O5 Additives on the Microstructure and Magnetic Properties of Lithium Ferrite

Lithium ferrite materials with different concentrations of Bi2O3 and V2O5 additives are prepared by the conventional ceramic technique. The x-ray diffraction analysis proves that the additives do not affect the final crystal phase of the lithium ferrite in our testing range. Both Bi2O3 and V2O5 additives could promote densification and lower sintering temperature of the lithium ferrite. The average grain size first increases, and then gradually decreases with the Bi2O3 content. The maximal grain size appears with 0.25 wt% Bi2O3. The average grain size first increases, and then is kept almost unchanged with the V2O5 content. The maximal average grain size of the samples with V2O5 additive is much smaller than that of the samples with Bi2O3 additive. Furthermore, the V2O5 additive more easily enters the crystal lattice of the lithium ferrite than the Bi2O3 additive. These characteristics evidently affect the magnetic properties, such as saturation flux density, ratio of remanence Br to saturation flux density Bs, and coercive force of the lithium ferrite. The mechanisms involved are discussed.

Study on Dispersions of Width Mode of Magnetostatic Surface Wave Propagating in Periodic Multilayer Films

The general dispersion relation of width mode of the magneto-static surface wave (MSSW) propagating in YIG multilayer films with finite sample width and arbitrary parameters is established. The theory includes all the situations of MSSW dispersion control by multilayer films and is in a better agreement with the actual situation. The dispersion of MSSW width mode in [(YIG/GGG) 10 /metal] periodic multilayer films were numerically investigated by applying the theory. Numerical results showed that the main working mode of MSSW propagating in multilayer YIG films is the first order width mode, the dispersion of MSSW can be controlled efficiently by the multilayer periods and the parameters of each layer. It also is influenced by the sample width.