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  • 1
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Ni-Ti Shape Memory Alloy thin films are suitable materials for microelectromechanicaldevices. During the deposition of Ni-Ti thin films on Si substrates, there exist interfacial diffusionand chemical interactions at the interface due to the high temperature processing necessary tocrystallize the film. For the present study, Ni-Ti thin films were prepared by magnetron cosputteringfrom Ni-Ti and Ti targets in a specially designed chamber mounted on the 6-circlegoniometer of the ROssendorf BeamLine (ROBL-CRG) at ESRF, Grenoble (France). The objectiveof this study has been to investigate the interfacial structure resulting from depositions (at atemperature of ≈ 470°C) on different substrates: naturally oxidized Si(100), Si(111) and poly-Sisubstrates. A detailed High-Resolution TEM analysis of the interfacial structure has beenperformed. When Ni-Ti is deposited on Si(100) substrate, a considerable diffusion of Ni into thesubstrate takes place, resulting in the growth of semi-octaeder A-NiSi2 silicide. In the case of Ni-Tideposited on Si(111), there appears an uniform thickness plate, due to the alignment betweensubstrate orientation and the [111]-growth front. For Ni-Ti deposited on poly-Si, the diffusion isinhomogeneous. Preferential diffusion is found along the columnar grains of poly-Si, which arefavourably aligned for Ni diffusion. These results show that for the Ni-Ti/Si system, the morphologyof the diffusion interface is strongly dependent on the type of substrates
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  • 2
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 157-162 (May 1994), p. 275-286 
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 3
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 308-311 (May 1999), p. 25-30 
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 4
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 5
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The Cu/W functionally graded material (FGM) was produced by vibration of Wagglomerates in order to obtain the W skeleton with a gradient in porosity, which after pressureless sintering was infiltrated with molten Cu. Certain sintering mechanisms are suggested for these complex W structures. The segregation of two different sizes of W agglomerates was controlled by vibration time. Different vibration duration resulted in different types of microstructure: skeleton type microstructure after shorter vibration time and graded type microstructure after extended vibration times. The final Cu-infiltrated FGMs were characterized microstructurally and theirelectrical resistivity (r) was measured using the 4-probe technique. The values of r were in between those for pure W and Cu, depending strongly on the vibration times of the initial W agglomerates, and exhibiting particular r vs. T (K) behavior
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  • 6
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Deep gettering layers have been formed in Si wafers by MeV implantation of Si+ and P+ ions, followed by annealing. Samples have been subsequently contaminated with Cu. Secondary ion mass spectrometry analysis reveals for P implants gettering of Cu atoms in regions significantly deeper than the projected ion range RP and formation of a separate Cu gettering band there. We call this phenomenon the "trans-RP effect." The results obtained indicate the presence of an appreciable amount of defects in the region beyond RP. Their gettering ability is much higher than that of the implanted gettering layer at RP. The size of these deep defects is below the resolution limit of transmission electron microscopy. We suggest that they are interstitials and/or small interstitial clusters. An explanation of the mechanism responsible for their migration from RP into the trans-RP region and their clustering is proposed. © 1999 American Institute of Physics.
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  • 7
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The formation of helium induced cavities in silicon is studied as a function of implant energy (10 and 40 keV) and dose (1×1015, 1×1016, and 5×1016 cm−2). Specimens are analyzed after annealing (800 °C, 10 min) by transmission electron microscopy (TEM) and elastic recoil detection (ERD). Cavity nucleation and growth phenomena are discussed in terms of three different regimes depending on the implanted He content. For the low (1×1015 cm−2) and high (5×1016 cm−2) doses our results are consistent with the information in the literature. However, at the medium dose (1×1016 cm−2), contrary to the gas release calculations which predict the formation of empty cavities, ERD analysis shows that a measurable fraction of the implanted He is still present in the annealed samples. In this case TEM analyses reveal that the cavities are surrounded by a strong strain field contrast and dislocation loops are generated. The results obtained are discussed on the basis of an alternative nucleation and growth behavior that allows the formation of bubbles in an overpressurized state irrespective of the competition with the gas release process. © 1997 American Institute of Physics.
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  • 8
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Low-resistivity (〈0.1 Ω cm), p-type SiC layers of about 500 nm width and targeted acceptor concentrations of 1.5×1020 cm−3 and 5.0×1020 cm−3 were produced by the combination of high-dose (1.0 and 3.3×1016 cm−2), multienergy (50–450 keV) Al+ ion implantation of 6H-SiC at −130 °C, ion-beam-induced crystallization with 500 keV, 5×1015 Si+ cm−2 at 500 °C and subsequent furnace annealing at 1500 °C for 10 min. The implanted SiC layers have a nanocrystalline structure consisting of randomly oriented grains of mainly 3C-SiC. The electrical properties of the doped, nanocrystalline layers were investigated by sheet resistance and Hall measurements in dependence on temperature and compared with results from single-crystalline reference samples. In comparison with the standard doping process, the hole concentration at 50 °C is enhanced by more than one order of magnitude from 9.0×1017 cm−3 to 1.6×1019 cm−3 in the case of 1.5×1020 Al cm−3 and from 6.1×1018 cm−3 to 8.0×1019 cm−3 in the case of 5.0×1020 Al cm−3, respectively. It can be speculated that the loss of active Al acceptors by precipitation is reduced in the nanocrystalline layers and, therefore, the critical concentration for the formation of an impurity band can be achieved. © 2002 American Institute of Physics.
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  • 9
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Investigations on the application of chemical and optical methods (infrared and Raman spectrum) on vinyl acetate monomer and polymer in the solid state and in solution are made. The polymerization of a sample of vinyl acetate, progressing slowly under the influence of daylight, is followed spectroscopically through 11/2 years. Two spectra, belonging to the monomer and polymer and differing mainly by the disappearance of vinyl group frequencies and appearance of the chain frequencies of long chain paraffins, are obtained. A tentative assignment of the individual frequencies is given. The presence of a weak C=C frequency in the spectrum of vinyl acetate polymer indicates a small residue of double bonds in the polymer. In order to clear the problem of the origin of these double bonds and especially to see if they are caused by included monomer, the high polymer vinyl acetates are purified by repeatedly dissolving and fractionating them. Once more they are studied spectroscopically. In spite of the disappearance of the C=O frequency of the monomer, the weak C=C double bond frequency is indicated in the polymer spectrum. Therefore it is not caused by included monomer. This frequency does not alter its position, and it may be concluded that terminal double bonds are involved. Variation of the polymerization conditions of vinyl acetate (polymerization under pressure, with ultraviolet irradiation, with catalysts and in solution) always yields identical spectra. In spite of using various amounts of catalyst, no binding of catalyst fragments to the molecule can be observed. Photographs of polyvinyl acetate and polystyrene in solvents reproduce the unaltered spectrum of the polymer and solvent, respectively, and do not furnish any criteria for the presence of intermolecular forces in these solutions. On the other hand, in acrylic and polyacrylic acid, from which Raman and infrared spectra are taken, intermolecular forces (that is, hydrogen bonds) can be shown to exist. Anhydrous acrylic and polyacrylic acids, as well as their aqueous solutions, are investigated and the structures following water addition are discussed. The results show that an association of the carboxyls can be observed with the polymeric acid. This is analogous to the association of low molecular carboxylic acids. The low solubility of anhydrous polyacrylic acid and its behavior at the softening point correspond to the properties of a slightly crosslinked polymer, and are explained from spectroscopic data. Titrations show that polyacrylic acid contains no double bonds after dialysis. Hydrogen bonds in polyacrylic acid esters, discussed in the literature, cannot be confirmed. The α-methyl group present in methacrylates is held responsible for the difference of softening points between acrylic and methacrylic compounds.
    Notes: Es werden Untersuchungen über Anwendung von chemischen und optischen Methoden (Infrarot- und Raman-Spektrum) an monomerem und polymerem Vinylacetat im festen Zustand und in der Lösung durchgeführt. Die unter dem Einfluss des Tageslichtes langsam fortschreitende Polymerisation einer Vinylacetat-Probe wird über 11/2 Jahr lang spektroskopisch verfolgt. Es ergeben sich zwei Spektren, das des Monomeren und das des Polymeren, die sich in der Hauptsache dadurch unterscheiden, dass die Frequenzen der Vinylgruppe verschwinden und die Kettenfrequenzen der langkettigen Paraffine in Erscheinung treten. Eine versuchsweise Zuordnung der einzelnen Frequenzen wird mitgeteilt. Das Vorhandensein einer schwachen C=C-Frequenz im Spektrum des polymeren Vinylacetats zeigt an, dass in diesem noch ein geringer Rest an Doppelbindungen vorhanden ist. Um die Frage nach der Herkunft derselben zu klären, insbesondere um festzustellen, ob sie von eingeschlossenem Monomeren herrühren, werden hochpolymere Vinylacetate durch wiederholtes Lösen und fraktioniertes Fällen gereinigt und erneut spektroskopiert. Trotz Verschwindens der C=O-Frequenz des Monomeren ist jedoch die C=C-Doppelbindungsfrequenz im Spektrum des Polymeren noch schwach angedeutet, so dass die Möglichkeit besteht, dass sie nicht von eingeschlossenem Monomeren herrührt. Dass diese Frequenz ihre Lage nicht lässt darauf schliessen, dass es sich um endständige Doppelbindungen handelt. Vielfache Variation der Bedingungen bei der Polymerisation des Vinylacetats (Polymerisation im Block unter Druck, im UV-Licht, mit Katalysatoren und in Lösung) ergibt, dass stets identische Spektren entstehen, so dass das Aufbauprinzip dieses Polymeren stets das gleiche sem muss. Trotz Einsatz wechselnder Mengen an Katalysator kann von einem Einbau desselben in das Molekül im Spektrum nichts bemerkt werden. Die Aufnahmen von Polyvinylacetat und Polystyrol in Lösungsmitteln, die das Spektrum des Polymeren bzw. des Lösungsmittels unverändert wiedergeben, lassen keinen Anhaltspunkt für das Vorhandensein von zwischenmolekularen Kräften in diesen Lösungen erkennen. Im Gegensatz hierzu sind in der Acryl- und Polyacrylsäure, von der Raman- und Infrarot-Spektren aufgenommen werden, zwischenmolekulare Kräfte in Form von Wasserstoffbrücken nachweisbar. Für die Untersuchungen werden sowohl wasserfreie Acrylsäure und Polyacrylsäure als auch deren wässrige Lösungen herangezogen und die bei Zusatz von Wasser entstehenden Strukturen diskutiert. Die Ergebnisse zeigen, dass auch bei der polymeren Säure eine Assoziation der Carboxyle zu beobachten ist, die der von niedermolekularen Carbonsäuren weitgehend analog zu sein scheint. Die Schwerlöslichkeit der wasserfreien Polyacrylsäure ebenso wie ihr Verhalten am Erweichungspunkt, das dem eines schwach vernetzten Polymeren entspricht, werden aus den spektroskopischen Daten erklärt. Titrationen ergeben, dass Polyacrylsäure nach der Dialyse keine Doppelbindungen mehr enthält. Die in der Literatur diskutierten Wasserstoffbrücken in den Polyacrylsäureestern können nicht bestätigt werden. Für die Differenz der Erweichungspunkte zwischen Acryl- und Methacrylverbindungen wird die bei den Methacrylaten vorhandene α-ständige Methylgruppe verantwortlich gemacht.
    Additional Material: 20 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
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