Defect chemistry of the high-Tc superconductors

In the high temperature superconductors the critical temperature is intimately connected to the electronic charge-carrier concentration. The absolute values of this quantity and its dependencies on the controlling parameters temperature, oxygen partial pressure and doping content, is phenomenologically determined by the thermodynamics and kinetics of reactions involving point defects. Due to the low mobility of the ionic constituents the behavior at elevated temperatures is particularly important. Here, the kinetics are controlled by the mass transport parameters, essentially by the ionic conductivity. The scientific discipline whose objective is precisely described in the above terms is called defect chemistry. It quantitatively deals with the nature of excess and lacking native ionic or electronic particles as well as with foreign species. It describes the thermodynamics and kinetics of their formation, annihilation, interaction and motion in the phase under consideration and thus determines the chemistry within this phase.     

Ohmic contacts and n-type doping on TixCr2 − xO3 films and the temperature dependence of their transport properties

A procedure to dope n-type Cr_2 − xTi_xO₃ thin films is proposed. Besides doping the material, at the same time the method forms ohmic contacts on Ti_xCr_2 − xO₃ films. It consists on the deposition of 10 nm Ti and 50 nm Au, followed by thermal annealing at 1000 °C for 20 min in N₂ atmosphere. Ohmic contacts were formed on three samples with different composition: x = 0.17, 0.41 and 1.07 in a van der Pauw geometry for Hall effect measurements. These measurements are done between 35 K and 373 K. All samples showed n-type nature, with a charge carrier density (n) on the order of 10²⁰ cm^− 3, decreasing as x increased. As a function of temperature, n shows a minimum around 150 K, while the mobilities have an almost constant value of 11, 28 and 7 cm²V^− 1 s^− 1 for x = 0.17, 0.41 and 1.07, respectively.     

Some electrical properties of diamond-like carbon thin films

Diamond-like carbon (DLC) belongs to very interesting materials used for a number of practical applications. It was noted that the electrical properties of DLC films obtained by RF PCVD discharge depend substantially on the deposition conditions. The results and discussion of the electrical properties of DLC films and DLC/Si heterostructures is presented. The electrical conductivity results are explained in terms of hopping mechanism. The relation between charge transport, structure of the energy gap and the deposition conditions is discussed.     

一大型水利渡槽爆破拆除设计与施工

针对湖北省大悟县一大型水利渡槽结构特征,采取了水压爆破法拆除。本文阐述了该渡槽不采取炮孔法而采取水压爆破法拆除的理由、水压爆破法设计与施工和爆破效果。重点指出了水压爆破药量计算与药包布置,可供类似工程参考。     

Carrier density control in the La2−x Sr1+x Cu2O6+y system

The effect of strontium and oxygen content variation is systematically studied in the La_2−x Sr_1+x Cu₂O_6+y system. The reason for the absence of superconductivity in this system is discussed.     

一大型水利渡槽爆破拆除设计与施工

针对湖北省大悟县一大型水利渡槽结构特征,采取了水压爆破法拆除。本文阐述了该渡槽不采取炮孔法而采取水压爆破法拆除的理由、水压爆破法设计与施工和爆破效果。重点指出了水压爆破药量计算与药包布置,可供类似工程参考。     

PAMELA sub-detectors capability in identifying nuclei: Status of art and perspectives

After almost three years in orbit, the statistic collected by PAMELA detector for what concern nuclei events from cosmic rays is sufficiently relevant to allow a systematic study of such a component. For this scope charge reconstruction from Time-of-Flight system, calorimeter and magnetic spectrometer is used, with different combinations, in order to cover the widest range of inspection in energy and atomic number permitted by the characteristics of the detector. Some results for performances, goals and limits from the different sub-detectors will be presented.     

Cover Picture: Microscopic Evidence for Spatially Inhomogeneous Charge Trapping in Pentacene (Adv. Mater. 11/2005)

Trapped charge has been observed in polycrystalline pentacene films by electric force microscopy in work reported by Muller and Marohn on p. 1410. The cover shows an optical fiber watching the motion of a metal‐coated cantilever hovering over a polycrystalline pentacene film. The film occupies the 6.5 μm gap in a working field‐effect transistor. Trapped charge (dark blue and black areas in the pentacene) appears as large patches randomly distributed throughout the device, implying that long‐lived traps in polycrystalline pentacene are not correlated with grain boundaries.     

Photocatalytic microreactor using TiO2/Ti plates: Formation of TiO2 nanostructure and separation of oxidation/reduction into different channels

TiO₂ is the most popular and promising high-activity photocatalyst and has many applications. Recently, photocatalysis in microreactors has attracted attention due to its effective light irradiation and short diffusion distance. This article introduces our study on the fabrication of TiO₂/Ti bilayer plates and their application in a photocatalytic microreactor. First, TiO₂ layers with controlled nanostructures were fabricated via the direct oxidation of Ti plates. A network-like and flake-like nanostructure of TiO₂ was formed on the surface of Ti plates by alkaline treatment. TiO₂ nanotube arrays were formed by anodization of the Ti plate. These TiO₂/Ti plates exhibited high photocatalytic performance in the microreactor, which was enhanced by developing the nanostructure. Second, we developed a new photocatalytic microreactor with stacked channels for oxidation and reduction employing the charge separation effect of the TiO₂/Ti plate. The UV irradiation of the TiO₂-side channel generates pairs of holes and electrons, which are separated by the TiO₂/Ti plate and contribute to oxidation and reduction in the different channels. We confirmed the feasibility of this microreactor and demonstrated that the pH difference in the two channels was the important factor enhancing the reduction induced by transferred electrons.     

Luminescence mechanism and carrier dynamic studies of InGaN-based dichromatic light emitting diodes with ultraviolet and blue emissions

In this study, to investigate the luminescence mechanism and carrier dynamics of dichromatic InGaN-based light emitting diodes (LEDs) with two active regions, an ultraviolet (UV)-blue LED (UV active region above the blue one) and a blue-UV LED (blue active region above the UV one) were prepared. Photoluminescence (PL), cathodoluminescence (CL), and time-resolved photoluminescence measurements were performed. For the PL spectra of both LEDs, the blue emissions are stronger than the UV emissions. This trend shows that the higher degree of carrier localization of the blue active region, in either the upper or lower portions of the LEDs, can enhance carrier capture and recombination efficiency. Due to the large and bright light spots emitted from indium-rich clusters in the blue active region, CL images showed that the blue emission is dominant in the image shape for both samples. Furthermore, it was shown that the optical properties and carrier dynamics of dichromatic InGaN-based LEDs could be well explained by the combined effects of the carrier localization effect, structures, extraction efficiency, defect density, and carrier capture efficiency in the UV and blue active regions. Also, thermal effect plays an important role in carrier transport behavior in such dichromatic LEDs. The research results provide important information for operation mechanisms and device designs of dichromatic LEDs.     

航空炸弹的技术与装药

总结了国外航空炸弹采用的新技术（主要包括低阻技术、减速技术、集束化技术、制导技术、装药技术）和装药情况。     

深孔阶段崩矿孔端后冲带炮原因分析及对策

深孔柱状装药阶段崩矿炮孔的上下端部附近的矿岩处于侧向崩矿空区和凿岩硐室底板或拉底空间两个自由面状态下，不合理的装药结构将在硐室底板和拉底空间引起后冲带炮。后冲带炮在硐室底板形成的斜面影响后续装药施工，在拉底空间产生大块。结合工程实践分析了后冲带炮的原因及对策。     

炭纤维生物膜的形成机制Ⅱ. 炭纤维表面特性对微生物活性与增殖的影响

采用对比方法,借助化学分析、表面形态分析、微生物活性测定等技术首次系统地研究了以活性炭纤维、表面改性活性炭纤维作为细胞固着化用载体及载体表面特性对生物膜活性、菌液中微生物活性及增殖等的影响。重点考察了纤维表面官能团、比表面积、润湿性等表面特性对生物膜活性以及菌液中微生物活性及增殖等的影响。研究结果表明:(1)改善炭纤维表面的吸附特性有益于微生物固着及挂膜;增加活性炭纤维比表面积有利于提高其表面微生物的活性。(2)与其他有机高分子材料相比炭纤维可以促进微生物的生长。(3)炭纤维表面润湿性与某些酸性官能团的增加,有助于载体表面微生物的生长。     

Mechanisms of carrier generation and transport in Ni-doped Cu2O

The density and mobility of hole carriers in Ni-doped and undoped cuprous oxide (Cu₂O) films prepared by pulsed laser deposition (PLD) from Ni-doped and undoped CuO targets, respectively, were measured in order to examine the mechanisms of carrier generation and transport in doped films. The temperature dependence of the carrier density of the films revealed that regardless of the Ni content, the activation energies of the acceptor level of the films are 0.22-0.25 eV. The temperature dependence of the mobility of the films changed from −0.58 to ∼0 by doping with Ni. These results evidenced that hole carriers in Ni-doped Cu₂O as well as in undoped Cu₂O were generated by Cu vacancies and were primarily scattered by neutral impurity scattering centers. X-ray diffraction (XRD) measurements of the films showed that the mass fraction of Cu₂O in the films decreased with increasing Ni content, while that of CuO increased. It was also found that the reduction process of CuO to Cu₂O was suppressed by the Ni doping.     

Electroluminescence and electron transport characteristics of aromatic polyimides containing 1,3,4-oxadiazole moiety

Single and double layer polymer light-emitting diodes (LEDs) were fabricated by using 2,5-bis(4-aminophenyl)-1,3,4-oxadiazole (BAO)-based aromatic polyimides (APIs). All the resultant APIs have high glass transition temperatures (T_g > 250 °C) and high thermal decomposition temperatures (T_d > 510 °C). The APIs exhibit broad fluorescent characteristic, and the fluorescent intensity is related to the intermolecular chain's orientation. BAO-3,3′-oxydiphthalic anhydride (ODPA) and BAO-4,4′-(hexafluoro-iso-propylidene) diphthalic anhydride show electroluminescent property in single layer LED devices. By inserting BAO-ODPA in the poly(p-phenylene vinylene)-poly(vinylalcohol) LED device to form a double layer device, the EL efficiency can be improved by two orders of magnitude.