Photosensitive properties of organometallic films of silver anthraquinone derivatives

The photosensitive characteristics of organometallic films composed of silver and anthraquinone derivatives (AQDs) were investigated. AQDs with electron-attracting substituents form charge transfer complexes in which an electron is transferred from the silver to the AQD. Film complexes were fabricated both by vacuum deposition and using an electrochemical process. The photosensitive properties were investigated using argon laser light irradiation. The complexes decomposed to form silver colloids and AQDs after irradiation. The decomposition mechanism is discussed.     

Conduction mechanism in amorphous In2III X3VI thin films

Amorphous In₂ ^IIIX₃ ^VIfilms (X = Te or Se) are obtained by vacuum thermal evaporation of bulk materials on glass substrates. The current - voltage characteristics in the temperature range 298–378 K and in the thickness range 212–652 nm exhibited a transition from an ohmic region in the lower field followed by non-ohmic region in the high field region, which has been explained by the anomalous Poole-Frenkel effect. The temperature dependence of current in the ohmic region is of thermally activated process. The variation of dielectric constant with temperature is investigated for the two compounds.     

Synthetic studies on II/VI semiconductor quantum dots

The chemical synthesis of nanocrystals associated to the study of quantum size effects on II/VI semiconductor compounds has been investigated extensively. Considerable advances in the use of chemical procedures to produce II/VI semiconductor quantum dots have been made and recent strategies to produce such materials will be reviewed here. This review is structured using a tentative classification for the most used solution chemical methods applied to II/VI semiconducting dots. Current progress on the enhancement of physical properties of these materials using chemical approaches will be reviewed.     

Thermal expansion studies of substituted CTP derivatives

Several new Na, Y and Zr substituted derivatives of Ca_0·5Ti₂(PO₄)₃ (CTP) have been synthesized. These derivatives retain the hexagonal structure of the parent (CTP) compound with minor changes in lattice parameters. Linear thermal expansion coefficients(α) have been obtained using a high sensitivity dilatometer.     

VI. Medizinhistorische Deutsch-Polnische Gemeinschaftstagung in Dresden

Ohne Zusammenfassung     

Simulation studies of the hydrodynamics in high-temperature solutions for crystal growth. VI. Temperature fluctuations at the crystal/liquid interface

The temperature fluctuations at the crystal/liquid interface have been studied using model liquids. The character of the fluctuations varied depending on whether in the liquid there was only free convection or both free and forced convections were simultaneously present. It has been established that in the second case the amplitude of fluctuations is determined mainly by the rate of the resultant convection flow and the liquid viscosity. A maximum amplitude of fluctuations is observed at a resultant flow rate w_fl = O when the free and forced convections proceed in opposite directions, and at w_fl = min when both convection flows have the same direction. Larger amplitudes of temperature fluctuations are registered in low-viscosity liquids. The conditions under which a flat crystal/liquid interface showing no temperature fluctuations should be formed have been determined for crystal diameters of 10, 15 and 20 mm, respectively.     

Conduction in thin films of r.f. reactively sputtered zinc sulphide

Experiments on d.c. electrical conduction in thin films of r.f. reactively sputtered zinc sulphide (thicknesses from 100 to 1000 Å) sandwiched between Al and Au are described. For an electric field between 10⁵ and 10⁶ V cm^-1, the plot of log J versus √V is linear; the thermal evolution of the current is described by log J ～T^-1/3. It is therefore assumed that the electrical conduction is due to the emission of electrons from defects into the conduction band of the zinc sulphide.     

Conduction in thin polymer films

Thin polymer films have been made from a variety of starting monomers and their electrical conduction has been studied.The films are produced both by ultraviolet surface photolysis and by a cold-cathode glow-discharge technique. The samples are made in the form of a capacitor sandwich on a glass substrate with aluminium electrodes. The whole sample is made in a high-vacuum system, without breaking vacuum, using out-of-contact masking techniques.Generally, depending on the starting monomer, the polymer films are short-free down to a thickness of about 100 Å, and electric fields up to 10⁷ V/cm may be sustained.The current/voltage characteristics of the films have been investigated as a function of temperature and thickness. One theory to account for the conduction in these materials is presented and compared with other approaches to the problem.     

Conduction electron spin resonance in gold

Conduction electron spin resonance has been observed in transmission through pure gold slabs of 100, 260, and 490 µm thickness covered on each side by a thin ferromagnetic film. This resonance corresponds tog=2.11±0.01 and broadens rapidly above 10 K, in agreement with spin orbit relaxation by phonons.Laboratoire associé au CNRS.     

Conduction in Mn substituted Ni-Zn ferrites

The d.c. electrical resistivity ‘ρ’ and thermoelectric power ‘α’ are studied as a function of temperature for Mn substituted ferrites with general formula Zn_0·3Ni_0·7+x Mn _x Fe_2−2x O₄. At lower Mn concentrations, the increase in d.c. resistivity is attributed to the hindering of Verwey mechanism Fe²⁺ ⇌ Fe³⁺ due to stable bonds of Mn³⁺ + Fe²⁺ pair. The decrease in resistivity at higher Mn concentrations (i.e. whenx > 0·15) is attributed to the formation of Mn³⁺ cluster and Ni²⁺ ⇌ Ni³⁺. The activation energy values show one to one correspondence with resistivity values. The compositional variation of thermoelectric power showsn-type behaviour for the samples withx < 0·2 whereasp-type behaviour for the samples withx ⩾ 0·2. Thep −n transition is attributed to the formation of Ni³⁺, Fe²⁺ + vacancies which act asp-type carriers. The temperature dependences ofα, ρ, and mobility clearly confirm the conduction mechanism to be due to polaron hopping.     

金属有机骨架材料质子传导的研究进展

金属有机骨架材料(MOFs)由于其结构多样性、骨架的可修饰性、超高比表面积和孔隙等特点,在质子传导、气体分离和吸附、催化、化学传感和生物医药领域有着独特的优势和广泛的应用。本文综述了近年来金属有机骨架材料在质子传导方面的研究进展,系统地阐述了质子传导的Grotthuss机理和Vehicel机理,并针对两种不同的机理分别总结了提高MOFs质子传导率的方法,对质子传导MOFs的设计具有显著的指导意义。此外,还介绍了质子传导MOFs最重要的应用之一——质子交换膜。质子交换膜由于其高电导率、易成膜以及优良的选择性透过等特点在燃料电池上有巨大的应用潜力。质子交换膜燃料电池的快速发展,可改善对化石燃料高度依赖的能源结构和日益恶化的环境问题。     

Hopping Conduction in Mn Ion-Implanted GaAs Nanowires

We report on temperature-dependent charge transport in heavily doped Mn(+)-implanted GaAs nanowires. The results clearly demonstrate that the transport is governed by temperature-dependent hopping processes, with a crossover between nearest neighbor hopping and Mott variable range hopping at about 180 K. From detailed analysis, we have extracted characteristic hopping energies and corresponding hopping lengths. At low temperatures, a strongly nonlinear conductivity is observed which reflects a modified hopping process driven by the high electric field at large bias.     

Conduction mechanism in codeposited AgSe thin films

Thin films of AgSe of varying compositions and thicknesses have been formed on glass substrates employing the three-temperature method.I–V characteristics and thermoelectric power, α, of annealed samples have been measured as functions of composition, thickness and temperature of the films. Films exhibitn-type conductivity. Nonohmic conduction in films of Ag _x Se_1−x (0<x<0·5) and Ag _x Se_1−x (0>x>0·5) have been accounted for on the basis of the theory of Rose of defect insulator containing shallow traps and on Schottky emission respectively.     

MgFe_2O_4尖晶石型固溶体的导电性和缺陷结构

本研究在1000～1300℃温度下,一定的氧分压范围内对 MgFe_2O_4的导电率及热重量变化进行了测定。在富 Fe_2O_3的 MgFe_2O_4中 Fe~(2+)离子的浓度随着氧分压的降低而增加,达到一定氧分压时,Fe~(2+)离子浓度达到一定值,不随氧分压变化而改变,此时存在着计量化的尖晶石相,它并不具有与组成有关的缺陷。研究中计算得该缺陷平衡反应的ΔH 为57.3kJ/mol。导电率与氧分压变化的关系与 Fe~(2+)浓度与氧分压变化关系十分相似。并求得其激活能为0.16～0.21eV;表明了在八面体配位位置的铁离子以跳跃式电导为主导的导电机理。以此为依据,计算和讨论了阳离子空位的分布。