On the structural features of doped amorphous chalcogenide semiconductors

A study of Bi-doped amorphous (Ge42S58)100−xBix and Ge20S80−xBix has been carried out by differential thermal analysis (DTA) and X-ray diffraction methods so as to elucidate the impurity-induced modifications in the semiconductors. Thermal analysis reveals the presence of complex structural units in the modified material. An interesting feature of this study is the existence of a double glass transition in Ge20S80−xBix, which is reported for the first time in this system.

Minority-Carrier Lifetime In Polycrystalline Semiconductors

A model is described for grain boundary recombination in polycrystalline semiconductors. This model enables the evaluation of minority carrier lifetime in these materials. Es vvird ein Modell fur die Korngrenzenrekombination in polykristallinen Halbleitern beschrieben. Das Modell ermoglicht die Bestimmung der Minoritiitsladungstragerlebensdauer in diesen Materialien.

The nature of hydrogen induced amorphization of SmNi2 laves compound

Abstract is not available.

Electrical transport in layered crystalline semiconductors GeS doped with Ag, P impurities at high pressure

A study of the transport properties of layered crystalline semiconductors GeS (undoped and doped with Ag, P impurity) under quasihydrostatic pressure using Bridgman anvil system is made for the first time. Pressure-induced effects in undoped crystals reveal initial rise in resistivity followed by two broad peaks at higher pressures. Silver doping induces only minor changes in the behaviour except removing the second peak. Phosphorous impurity is found to have drastic effect on the transport properties. Temperature dependence of the resistivity exhibits two activation energies having opposite pressure coefficients. Results are discussed in the light of intrinsic features of the layered semiconductors.

Pressure induced effects in bulk amorphous n-type semiconductors(GeSe3.5)100âxBix

The effect of pressure on the electrical resistivity of amorphous n-type (GeSe3.5)100�xBix been studied in a Bridgeman anvil system up to a pressure of 90 kbar down to liquid nitrogen temperature. A continuous amorphous semiconductor to metal-like solid transition in the undoped GeSe3.5 is observed at room temperature. Incorporation of Bi in the GeSe3.5 network is found to significantly disturb the behaviour of the resistivity with pressure. With increasing Bi concentration a much broader variation in resistivity with pressure is observed. The temperature dependence of the resistivity and activation energy at different pressures is also measured and they are found to be composition dependent. Results are discussed in the light of the Phillips Model of ordered clusters in chalcogenide semiconductors.

Study of effects of dopants on structure of vitreous semiconductors (GeSe3.5)100-xMx (M = Bi, Sb) using high pressure techniques

An investigation of the problem of controlled doping of amorphous chalcogenide semiconductors utilizing a Bridgman anvil high pressure technique, has been undertaken. Bulk amorphous semiconducting materials (GeSe3.5)100-x doped with M = Bi (x = 2, 4, 10) and M = Sb (x = 10) respectively are studied up to a pressure of 100 kbar down to liquid nitrogen temperature, with a view to observe the impurity induced modifications. Measurement of the electrical conductivity of the doped samples under quasi-hydrostatic pressure reveals that the pressure induced effects in lightly doped (2 at % Bi) and heavily doped (x = 4, 10) semiconductors are markedly different. The pressure effects in Sb-doped semiconductors are quite different from those in Bi-doped material.

A study on the nature of the compound layer formed during the ion nitriding of En40B steel

Commercial-grade En40B steel has been ion nitrided in the temperature range 475–550°C in a 25%N2–75%H2 gas mixture. The nature of the compound layer formed was studied by the X-ray diffraction technique and optical metallography. It was observed that the structure of the compound layer gradually transforms from a predominantly epsilon (Porson) nitride to a predominantly γ′ nitride structure with increasing treatment time. Optical metallography studies on sections orthogonal to the nitrided surface showed that, after about 5 h of treatment, the thickness of the compound layer decreases with further increase in treatment time.

Evidence for a new metastable crystalline compound in Ge---Te system

Pressure dependence of the electrical resistivity of bulk, melt quenched GexTe100−x glasses (15 less-than-or-equals, slant x less-than-or-equals, slant 28) has been studied up to 8GPa pressure. All the glasses exhibit a sharp, discontinuous glass to crystal transition under pressure. The high pressure crystalline phases are identified to have a face centered cubic structure. The value of the cell constant is 0.779nm for 15 less-than-or-equals, slant x less-than-or-equals, slant 17, 0.642nm for x=20 and 0.55lnm for 22 ≤ x ≤ 28 samples respectively. The cell constants of the high pressure crystalline phases suggest the possible existance of a new metastable crystalline compound in the Ge---Te system with F.C.C. structure and cell constant equal to 1.109nm as reported by Moore et al.

Odour, dust and non-methane volatile organic-compound emissions from tunnel-ventilated layer-chicken sheds: a case study of two farms

An observational study was undertaken to measure odour and dust (PM10 and PM2.5) emission rates and identify non-methane volatile organic compounds (NMVOCs) and odorants in the exhaust air from two tunnel-ventilated layer-chicken sheds that were configured with multi-tiered cages and manure belts. The study sites were located in south-eastern Queensland and the West Gippsland region of Victoria, Australia. Samples were collected in summer and winter on sequential days across the manure-belt cleaning cycle. Odour emissions ranged from 58 to 512 ou/s per 1000 birds (0.03-0.27 ou/s.kg) and dust emission rates ranged 0.014-0.184 mg/s per 1000 birds for PM10 and 0.001-0.190 mg/s per 1000 birds for PM2.5. Twenty NMVOCs were identified, including three that were also identified as odorants using thermal desorption-gas chromatography-mass spectrometry/olfactometry analysis. Odour emission rates were observed to vary with the amount of manure accumulation on the manure belts, being lowest 2-4 days after removing manure. Odour emission rates were also observed to vary with diurnal and seasonal changes in ventilation rate. Dust emissions were observed to increase with ventilation rate but not with manure accumulation. Some NMVOCs were identified at both farms and in different seasons whereas others were observed only at one farm or in one season, indicating that odorant composition was influenced by farm-specific practices and season.

Terezin: Barrack "Dresden" compound, barracks women's activities.

Initialed and dated lower right. Inscription attached paper: "Court of Dresden barracks for ladies only"

A New Rare-Gas Compound: HXeOXeH

Rare-gas chemistry is of growing interest, and the recent advances include the "insertion" of a Xe atom into OH and water in the rare-gas hydrides HXeO and HXeOH. The insertion of Xe atoms into the H-C bonds of hydrocarbons was also demonstrated for HXeCC, HXeCCH and HXeCCXeH, the last of which was the first rare-gas hydride containing two rare-gas atoms. We describe the preparation and characterization of a new rare-gas compound, HXeOXeH. HXeOXeH was prepared in solid xenon by photolysis of a suitable precursor, for example water, and subsequent mobilization of the photoproducts. The experimental identification was carried out by FTIR spectroscopy, isotopic substitution and by use of various precursors. The photolytical and thermal stability of the new rare-gas hydride was also studied. The experimental work was supported by extensive quantum chemical calculations provided by our co-workers. HXeOXeH forms in a cryogenic xenon matrix from neutral O and H atoms in a two-step diffusion-controlled process involving HXeO as an intermediate [reactions (1) and (2)]. This formation mechanism is unique in that a rare-gas hydride is formed from another rare-gas hydride. H + Xe + O → HXeO (1) HXeO + Xe + H → HXeOXeH (2) Similarly to other rare-gas hydrides, HXeOXeH has a strongly IR-active H-Xe stretching vibration, allowing its spectral detection at 1379.3 cm-1. HXeOXeH is a very high-energy metastable species, yet thermally more stable than many other rare-gas hydrides. The calculated bending barrier of 0.57 eV, is not enough to explain the observed stability, and HXeOXeH might be affected by additional stabilization from the solid xenon environment. Chemical bonding between xenon and environmentally abundant species like water is of particular importance due to the “missing-xenon” problem. The relatively high thermal stability of HXeOXeH compared to other oxygen containing rare-gas compounds is relevant in this respect. Our work also raises the possibility of polymeric (–Xe–O)n networks, similarly to the computationally studied (XeCC)n polymers.

Electrical transport in Bi doped n-type amorphous semiconductors (GeSe3.5)100-xBix at high pressure

Electrical transport in Bi doped amorphous semiconductors (GeSe3.5)100-xBix (x=0,4,10) is studied in a Bridgman anvil system up to a pressure of 90 kbar and down to 77 K. A pressure induced continuous transition from an amorphous semiconductor to a metal-like solid is observed in GeSe3.5. The addition of Bi disturbs significantly the behaviour of resistivity with pressure. The results are discussed in the light of molecular cluster model for GeySe1-y proposed by Phillips.