Die räumliche verteilung der rekombination in legierten silizium-psn-gleichrichtern bei belastung in durchlassrichtung

Making use of the emitted infrared radiation, the charge carrier distribution n(x) in p-s-n diodes that were biased in forward direction was measured on cross-cuts. The sagging of this distribution depends on the lifetime and yields in conjunction with the stored charge a measure for that part i_m of the current density i which recombines in the weakly doped center region. The current density i, on the other hand, is a measure for the recombination in the entire diode. Therefore, infrared measurements in conjunction with determinations of the stored charge make it possible to determine for a given forward current density i the distribution i_m/i of the recombination between the weakly doped center region and the highly doped border regions.Since the radiation measurements are performed on small rectangular polished specimens (1 × 4 mm) that have been cut from the diode wafer, the measurements can be noticeably influenced by surface recombination. This influence is discussed in detail. As it turns out, only an upper limit can be given for the recombination distribution i_m/i. However, this is sufficient to ensure that already at current densities of 100–200 A cm^?2 the recombination takes place predominantly in the highly doped border regions. At current densities of 1000–3000 A cm^?2 the contribution of the center region to the recombination practically vanishes.     

Crystal structure and magnetic properties of Cu4NiSi2S7

The structure of the compound Cu₄NiSi₂S₇ has been determined. It crystallizes in a new, monoclinic distorted sphalerite superlattice with the parameters: $\text{a}\text{= 11.551}\text{A}\text{?}$, $\text{b}\text{= 5.313}\text{A}\text{?}$, $\text{c}\text{= 8.165}\text{A}\text{?}$, β = 98.72°, $\text{V}\text{= 495.2}\text{A}\text{?}{}^3$, Z = 2, space group C2. The analogous compound Cu₄NiGe₂S₇ is isotypic. At a Neél temperature T_N = 20.2 K, Cu₄NiSi₂S₇ becomes antiferromagnetic. The magnetic moment of the paramagnetic phase is 2.6μ_B.     

In situ studies of the decomposition of ammonium uranyl carbonate in an electron microscope

An electron microscope has been used to study the reduction of ammonium uranyl carbonate (AUC) to UO₂. The reactions could be followed both in the diffraction and the lattice image mode. The first intermediate obtained was amorphous UO₃. Depending on the experimental conditions, either crystalline UO₂ was formed directly from this phase, or several other intermediates were indicated.Properties like crystallinity and crystallite size of final UO₂ were found to be a function of experimental conditions. Comparisons with properties of UO₂ from the industrial process have been made.     

Design of an irradiation device for the determination of the in-pile creep behaviour of zircaloy cladding tubes under internal and external over-pressure,in FRG-2

The dimensional stability of fuel rods in light water reactors is influenced by the creep strength of the Zircaloy (Zry) cladding. The Gesellschaft für Kernenergieverwertung in Schiffbau und Schiffahrt m.b.H and Kraftwerk Union AG are jointly carrying out irradiation experiments in FRG-2, to determine the effect of neutron irradiation on the creep behaviour of Zry cladding. In these capsule experiments specimens can be tested in a helium environment at temperatures from 280 to 400°C in a fast neutron flux of approx. $\text{5 × 10}{}^{13}\text{/}\text{cm}{}^2\text{s}$ under biaxial tensile and compressive stresses from 70 N/mm² to 150 N/mm². In the paper the test equipment, the experimental techniques and the initial results are described.     

Boreal freshwater fish diet modifies the plasma lipids and prostanoids and membrane fatty acids in man

The effect of fish diet on 43 healthy male students was studied. They ate a fish-containing meal for 15 weeks on an average of 3.7 times per week. Twenty-one of them voluntarily restricted their lipid intake while the rest ate normally. Controls continued their usual eating habits (19 students). The meals consisted of Finnish freshwater fish (87%) (vendace, pike, perch and rainbow trout) and brackish water fish (13%) (Baltic herring) that provided about 1 g of ω-3 polyunsaturated fatty acids per day (0.25 g eicosapentaenoic acid and 0.55 g docosahexaenoic acid). During the diet, ω-3 fatty acids increased in erythrocyte ghosts and platelets at the expense of ω-6 fatty acids. The concentration of serum cholesterol diminished in those fish consumers who lowered their lipid intake. Apolipo-protein A₁ and B were lowered in both fish-consuming groups. Triglyceride levels also showed a tendency to decrease. The formation of thromboxane B₂ during incubation of whole blood decreased in both fish-consuming groups. The decrease of plasma 6-keto-PGF_1α was not statistically significant, if compared with the controls. The results obtained indicate that a moderate intake of fish-containing meals has some beneficial effects on the plasma lipid and prostanoid metabolism, when coronary heart disease risk factors are considered.     

Direct imaging of atomic steps in reflection electron microscopy

The reflection mode (REM) is used in a transmission electron microscope to demonstrate imaging of atomic steps on the surface of thin MgO single crystal platelets.