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1.
The paper reviews the recent year publications concerning organic field-effect transistors (OFETs). A lot of works have been performed to help understanding the structural and electrical properties of materials used to construct OFETs. It has been established that in partially ordered systems, the charge transport mechanism is thermally activated and field-assisted hopping transport and the hopping transport between disorder-induced localized states dominate over intrinsic polaronic hopping transport seen in organic single crystals. Many research attempts have been carried out on the design of air-stable organic semiconductors with a solution process which is capable of producing OFETs with excellent properties and good stability when subjected to multiple testing cycles and under continuous electrical bias. Recent experiments have demonstrated ambipolar channel conduction and light emission in conjugated polymer FETs. These achievements are the basis for construction of OLED based displays driven by active matrix consisting of OFETs.  相似文献   
2.
From Raman data and a group-theoretical analysis, we deduce that in Bi12GeO20 and Bi12SiO20 there are four weakly bound oxygen atoms and a tightly bound unit MO4, where M = Ge or Si. Some normal modes of the tightly bound units are identified in Raman and in infrared reflection data. The kinds of interatomic binding forces in these crystals are determined. The results are compared with structure data determined by X-ray scattering.  相似文献   
3.
Absorption of Bi12GeO20 and Bi12SiO20 single crystals doped with Mn and Cr were investigated before and after illumination with visible light. Pronounced photochromic effects were found. The effects are explained in terms of light induced charge transfer Mn4+→Mn5+ and Cr3+→Cr2+.  相似文献   
4.
ABSTRACT

Raman light scattering measurements in the temperature range from 80 to 830 K were performed on a PbZr0.72Sn0.28O3 single crystal. The frequencies of the Raman lines were analyzed and discussed in terms of the sequence of structural phase transitions. It was found that Raman spectrum displays important changes near 440, 480 and 493 K. The incorporation of more than 25 mol% of Sn4+ ions into the structure of PbZrO3 enhances polar fluctuations above TC as compared to the less Sn-doped crystals. These fluctuations lead to appearance of a ferroelastic intermediate phase below TC. It is demonstrated that the structural phase transformation in PbZr0.72Sn0.28O3 can be considered as the result of softening of a number of modes.  相似文献   
5.
Abstract

We have measured the dielectric constants of 6CHBT. The results from studies of various alignments and thicknesses measured under different electric and magnetic fields are presented. We discuss how the dielectric properties depend on boundary conditions, sample thickness and the magnitudes of electric and magnetic fields. Experimental results and discussion in the terms of continuum theory make it possible to compute the diamagnetic anisotropy (Δχ), as well as the splay and bend elastic constants (K 11, K 33) of 6CHBT.  相似文献   
6.
The Ramanujan Journal - Let $$k\in \mathbb {N}_{\ge 2}$$ and for given $$m\in \mathbb {Z}{\setminus }\{0\}$$ consider the sequence $$(S_{k,m}(n))_{n\in \mathbb {N}}$$ defined by the power series...  相似文献   
7.
The magnetic investigations of potassium holmium double tungstate KHo(WO4)2 have been performed. The results of measurements of magnetic susceptibility and magnetization as a function of both temperature (T = 0.5–100 K) and magnetic field (up to 2 T) are presented.  相似文献   
8.
Doped single crystals of BGO and BSO with Cr, Mn, Cu, Ni have been grown. The conditions for the growth of doped single crystals by the Czochralski method have been determined, analyses of distributions of dopants in the crystals have been made. For the Mn, Cr, Cu, doped crystals changes of coloration after illumination with visible light have been observed.  相似文献   
9.
Abstract

Measurements of complex electric permittivity of room temperature ferroelectric liquid crystal mixtures have been made on aligned samples with the electric measuring field being parallel to the layer planes. The spontaneous polarization, the tilt angles and pitch have been measured in these mixtures. By theoretical fitting of the experimental points of electric permittivity for the Cole–Cole modification of the Debye equation dielectric parameters, the dielectric strength, relaxation frequency, and distribution parameter for the Goldstone mode have been computed. The dielectrically observed Goldstone mode in our mixtures is shown to have both DC bias field and AC field dependences.  相似文献   
10.
The optical absorption and ESR spectra of Bi12GeO20 and B12SiO20 doped with Mn have been measured before and after illumination with visible light. Uniaxial stress measurements on a sharp line observed at 8026 cm?1 were performed. The observed ESR spectrum is a superposition of six lines resulting from the hyperfine interaction of manganese ions in tetrahedral positions. The g-factor and hyperfine constant are g = 1.999 ± 0.003 and A = 78 Gs. Analysis of the light-induced absorption spectrum leads to the conclusion that a small hole polaron bound to an Mn impurity at a tetrahedral site is responsible for the very broad absorption band which appears after illumination. The sharp line is interpreted as due to a transition inside the Mn+ center in tetrahedral coordination. Bands in the region 10,000–16,000 cm?1 are due to Mn3+ centers in interstitial positions, whose symmetry can be treated to a first approximation as tetragonal. The following crystal field parameters for this center were found: B = 565 cm?1, Dq = 1400 cm?1, Dt = ?330 cm?1, Ds = 4170 cm?1 and C = 2260 cm?1. The illumination conditions which are needed for homogeneous coloration of the sample are also discussed.  相似文献   
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