Phase response of omnidirectional reflection one-dimensional photonic crystals and defect modes

In this paper, we investigate the phase properties of light reflected from one-dimensional omnidirectional reflection photonic crystal. We observe that the phase changes drastically at large incident angles. This asymmetrical phase change should be considered at oblique incidence, and various phase compensators and retarders can be designed by this nonlinear curved surface of phase shift. Furthermore, for the coupled defect 1D PC, the phase change depends mainly on the top of the sharp peak of the weak undulation within the rectangular defect band, because the top of the peak of the undulation is very sharp, i.e. large phase change look like within almost a single frequency. This drastic phase change can be used to design phase controllers.     

Eine Dichtigkeitsprüfanlage für Halbleiterbauelemente auf der Grundlage von 85Kr

Auf der Basis von ⁸⁵Kr wurde ein Prüfstand für die routinemäßge Dichtigkeitsprüfung von Halbleiterbauelementen entwickelt und gebaut. Die Anlage arbeitet mit einer Aktivkohlepumpe und ist für einen Maximaldruck ion 13 kp/cm² und eine Maximalaktivität von 40Ci⁸⁵Kr ausgelegt. Es werden einige theoretische Angaben zur Methode gemacht und der Auf ban sowie die Funktionsweise des Prüfstandes beschrieben. Die erhaltenen Ergebnisse werden mit denen anderer Methoden verglichen.     

Critical behaviour of the smectic A*–C* phase transition and electroclinic effect of ferroelectric liquid crystals with terphenyl rigid core

The SmA*–SmC* phase transition was studied by measuring the temperature and electric field dependences of the optical tilt angle, the electric polarisation and the dielectric spectra collected in a wide frequency range. Critical behaviour of the phase transition was analysed by varying the length of the fluorinated part of the alkyl terminal chain and by differing fluorine substitution in the terphenyl core. Both tilt and polarisation show tricritical mean-field behaviour for all homologues with n?>?2. Almost all coefficients that describe the SmA*–SmC* transition in the frame of the Landau theory were derived for homologue series. Double fluorine substitution in the central ring of the core seems to promote the ‘de Vries'-type smectic A*–C* phase transition with a little layer shrinkage. These well correspond with the lower tilt angle and smaller changes of the birefringence at the phase transition compared to the other homologues.     

Investigation of patch antennas based on drilled PBG structure

The method of finite-difference-time domain (FDTD) was used to study the characteristics of the patch antenna based on drilling air holes in the PBG substrate. The results obtained show that the waves propagating along the substrate surface can be suppressed by the drilled photonic crystal band gap (PBG) structure due to the influence of its forbidden band. The energy of the electromagnetic waves is concentrated mainly in the substrate. As a result, patch antennas based on drilling air holes in the PBG substrate have lower return losses (S11) in comparison with the conventional patch antennas; thus, a high gain is reached and the performance is improved. Due to such the advantages, the use of patch antennas can be extended to such fields as mobile communication, satellite communication, aviation, etc.     

Short range orientational order in nematic liquid crystals

The different approximations that have been used in applying Bethe’s cluster model to the nematic-isotropic phase transition are examined. It is shown that the introduction of a higher order term in the mean field potential of an outer molecule of the cluster improves the consistency of the theory considerably. In particular, the importance of satisfying Chang’s relation is emphasized. Calculations are presented of the long and short range order parameters, heat of transition and specific heat for different values ofz, the number of nearest neighbours around any given molecule, for both nonpolar and antiparallel near neighbour correlations. Even the new mean field potential appears to be inadequate forz=3.     

以陶瓷厚膜为绝缘层的红色ZnS:Sm,Cl电致发光器件

报道采用高介电常数的陶瓷厚膜作绝缘层、ＺｎＳ：Ｓｍ,Ｃｌ作为发光层的红色薄膜电致发光器件。测量了器件的电致发光光谱和亮度电压曲线,研究了发光机理和效率电压等特性。制备的器件在电驱动下１６Ｖ启亮,最大亮度为１８．４ｃｄ／ｍ＾２,最大效率为０．０６１ｍ／Ｗ。     

卢瑟福散射实验装置的研制

研制了一种鼎瑟福散的实验装置,并介绍了其实验结果,由于要用了步进电机和半导体探测器,该装置具有结构紧凑,操作简便等优点。     

X-ray emission spectroscopy with EPMA applied to high Tc Superconductors using new spectrometer crystals

The High Temperature Superconductors are characterized by a very anisotropical structure and by typical arrangements of Cu- and O-atoms within CuO₂-planes. In studying the electronic structure of these compounds there is a strong demand for high resolution valence band spectroscopy. Using an electron probe microanalyzer we study the X-ray emission of O-K_ga and Cu-L emerging from polycrystalline YBa₂Cu₃O₇ and Tl₂Ba₂Ca₂Cu₃O₁₀. The O-K emission band is analyzed using a chlinochlore crystal in (001) orientation (2d = 28.4 Å). For the Cu-L emission band we use a beryl crystal in (10¯10) orientation (2d = 15.9 Å). Furthermore, orientation dependent X-ray emission spectroscopy of single-crystalline YBa₂Cu₃O₇ and Tl₂Ba₂Ca₁Cu₂O₈ specimens was performed. We present the partial O-K spectra which represent the O-2p ( = x, y, z) electronic densities of states of the valence band and compare them with calculated data.     

Atmosphere effects in the processing of silicon carbide and silicon oxycarbide thin films and coatings

Silicon carbide and silicon oxycarbide films were prepared from solutions of polycarbosilane and methyldimethoxysilane + tetraethoxysilane, respectively, and deposited on different substrates (Si wafers, stainless steel plates, sapphire and SiC fibers). The coatings were heated at different temperatures and in different atmospheres, such as regular grade argon, ultra high purity and argon vacuum. The films were characterized using different techniques (FT-IR, XRD, SIMS, Ellipsometry).The influence of the processing parameters (heat treatment temperature and atmosphere) on the final microstructure of the coatings is discussed in this article.