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  • 1
    Electronic Resource
    Electronic Resource
    Preparation and characterization of highly oriented, photoconducting WS2 thin films (1996)
    Springer
    Applied physics 62 (1996), S. 543-546 
    Details
    ISSN: 1432-0630
    Keywords: PACS: 72.40; 73.60; 81.15; 81.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract.  A novel combination of methods is shown to produce semiconducting WS2 thin films with properties close to those of a single crystal. The first step requires the deposition of a very thin Ni layer on a quartz substrate. On top of it an amorphous, sulphur rich, (WS 3+x ) thin film is deposited by reactive rf sputtering. The final annealing step in an argon atmosphere yields 200 nm thick WS2 films. X-ray diffraction shows that the films crystallize in the 2H-WS2 phase and are perfectly oriented with the (002) basal planes parallel to the substrate. Residual W18O49 needles and β-NiS grains are detected by transmission electron microscopy. The dc conductivity and its activation energy have values typical of bulk crystals. The optical absorption spectrum measured at Room Temperature (RT) shows excitonic peaks at the same energies as in a single crystal. RT photoconductivity measured as a function of wavelength is shown to result from interband transitions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01571690
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  • 2
    Electronic Resource
    Electronic Resource
    Preparation and characterization of highly oriented, photoconducting WS2 thin films (1996)
    Springer
    Applied physics 62 (1996), S. 543-546 
    Details
    ISSN: 1432-0630
    Keywords: 72.40 ; 73.60 ; 81.15 ; 81.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract A novel combination of methods is shown to produce semiconducting WS2 thin films with properties close to those of a single crystal. The first step requires the deposition of a very thin Ni layer on a quartz substrate. On top of it an amorphous, sulphur rich, (WS3 +x ) thin film is deposited by reactive rf sputtering. The final annealing step in an argon atmosphere yields 200 nm thick WS2 films. X-ray diffraction shows that the films crystallize in the 2H-WS2 phase and are perfectly oriented with the (002) basal planes parallel to the substrate. Residual W18O49 needles andβ-NiS grains are detected by transmission electron microscopy. The dc conductivity and its activation energy have values typical of bulk crystals. The optical absorption spectrum measured at Room Temperature (RT) shows excitonic peaks at the same energies as in a single crystal. RT photoconductivity measured as a function of wavelength is shown to result from interband transitions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01571690
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Raman scattering from PbTiO3 thin films prepared on silicon substrates by radio frequency sputtering and thermal treatment (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 394-399 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Raman scattering has been carried out on PbTiO3 thin films prepared on platinum-coated (100) silicon by radio-frequency (rf)-magnetron sputtering without substrate heating and a post-deposition thermal treatment. The Raman spectra obtained from the thin film are characteristic of powder Raman spectra: In comparison with the single crystal spectra, the intensity of the background is relatively high at low frequencies and the Raman lines are broad. The lattice phonon modes corresponding to the observed lines are identified by comparison with the data on single crystals and powder. The Raman frequencies for the thin film remarkably shift to low frequencies compared with single-crystal data. It is shown that the phenomenon of the frequency shifts is similar with the hydrostatic pressure effect on single crystals of PbTiO3. The result indicates that the thin films are composed of grains that are stressed depending on the grain size by neighboring grains of different orientations when they are split up into ferroelectric domains at the paraelectric-to-ferroelectric transition. This stress effect is significant even for a grain size of ∼0.5 μm. It is found that the lowest frequency E transverse optical (TO) mode in the thin film shows softening with increasing temperature as was reported in previous studies on single crystals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353862
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  • 4
    Electronic Resource
    Electronic Resource
    Electrical and optical properties of TiO2 anatase thin films (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 2042-2047 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Electrical and optical spectroscopic studies of TiO2 anatase thin films deposited by sputtering show that the metastable phase anatase differs in electronic properties from the well-known, stable phase rutile. Resistivity and Hall-effect measurements reveal an insulator–metal transition in a donor band in anatase thin films with high donor concentrations. Such a transition is not observed in rutile thin films with similar donor concentrations. This indicates a larger effective Bohr radius of donor electrons in anatase than in rutile, which in turn suggests a smaller electron effective mass in anatase. The smaller effective mass in anatase is consistent with the high mobility, bandlike conduction observed in anatase crystals. It is also responsible for the very shallow donor energies in anatase. Luminescence of self-trapped excitons is observed in anatase thin films, which implies a strong lattice relaxation and a small exciton bandwidth in anatase. Optical absorption and photoconductivity spectra show that anatase thin films have a wider optical absorption gap than rutile thin films.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356306
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  • 5
    Electronic Resource
    Electronic Resource
    Raman scattering study of lead zirconate titanate thin films prepared on silicon substrates by radio frequency magnetron sputtering (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 6625-6631 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Raman scattering is used to characterize thin films of PbTi1−xZrxO3. The films have been prepared on platinum-coated (100) silicon by radio-frequency (rf)-magnetron sputtering without substrate heating followed by a post-deposition annealing at 600–650 °C. As the concentration of Zr is increased, the Raman peaks broaden and their intensities decrease more rapidly compared with bulk ceramic or powder samples, while the background intensity increases. The observations show that the crystal structure of the films is locally deformed and significantly disordered. With increasing x, the soft E(TO) mode shifts to lower frequencies. An additional Raman peak appears besides the phonon peaks expected in a perfect crystal. The soft mode strongly couples with the extra mode, similarly with the case of ceramic samples. The results are related to features of the thin films such as a frustrated phase transition, i.e., smaller differences between the lattice parameters a and c in comparison with powder data, and an electrical behavior showing a diffuse ferroelectric-to-paraelectric transition with a broad peak.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355103
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  • 6
    Electronic Resource
    Electronic Resource
    Trophic relationships: integrating meiofauna into a realistic benthic food web (2000)
    Oxford, UK : Blackwell Science Ltd
    Freshwater biology 44 (2000), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 〈list style="custom"〉1This paper summarises the most important contributions on trophic relationships of lotic meiofauna. In contrast to marine research, the few quantitative studies of the freshwater meiobenthos have shown that these invertebrates not only take up particulate/fine organic matter, but also dissolved organic substances attached to organic particles. In lotic ecosystems, further estimates of grazing rate and bacterial/algal ingestion rate are needed, particularly in situ measurements.2The effects of macroinvertebrate predators upon meiofauna are still under debate. Depending on the type of experiments (laboratory vs. field) it seems that macrofauna may or may not affect meiofauna. Field samples and analyses of gut contents of larval tanypod chironomids have shown that the impact upon meiofauna was low and larvae were nonselective predators. Predation amounted to 2.2% of the combined prey density and prey consumption averaged 1.3 individuals per predator individual per year.3Adding taxonomic resolution by including the meiofaunal component within lotic food webs distinctly increases the number of total species and, as a consequence, changes food web statistics. Webs that included meiofauna revealed that these metazoans contributed substantially to the percentage of intermediate species (species with predators and prey). The resolution of dietary analyses of major consumers of macro- and meiobenthos showed that many stream invertebrates feed on meiofauna.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2427.2000.00594.x
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  • 7
    Electronic Resource
    Electronic Resource
    Atomic scale study of local TiSi2/Si epitaxies (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 1820-1825 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The TiSi2/Si system is investigated using high-resolution transmission electron microscopy (HRTEM) and electron diffraction in both cross-section and flat-on modes. The results show that the large crystallographic differences between both crystals and the complexity of the reaction path are not obstacles to the formation of flat and well-defined interfaces. (1¯01) TiSi2 proves to be a preferential plane for epitaxial growth on Si (111). In this case, the terminal TiSi2 plane at the interface is composed of single atomic species. It is proposed that the reasons leading to such an epitaxy are related to the small discrepancy of atomic densities and interplanar spacings characteristic of these planes. Observation of local epitaxial relationships are reported and investigated using a lattice matching model. It turns out that they minimize the two-dimensional misfit at the interface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.345609
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  • 8
    Electronic Resource
    Electronic Resource
    Oxidation resistance of protective coatings studied by spectroscopic ellipsometry (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 76 (2000), S. 3194-3196 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Spectroscopic ellipsometry is applied to determine the oxidation resistance of TiN and CrN coatings. This technique proves to provide accurate measurements of the oxide layer thickness in a convenient, fast, and nondestructive manner. The magnetron-sputtered thin films were heated in air in the temperature range between 673 and 925 K. The verification with scanning electron microscopy and x-ray reflectometry shows an excellent agreement between these complementary techniques. The rate constant k of the oxidation is directly related to the film morphology in TiN thin films. While understoichiometric films with a dense fine-grained structure exhibit a moderate k of 4 nm2/s at 773 K, overstoichiometric films with a pronounced columnar structure oxidized over seven times faster. The nonstoichiometry in TiNy and CrNy leads to a reduced activation energy for oxidation compared to stoichiometric compounds. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.126626
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  • 9
    Electronic Resource
    Electronic Resource
    NewK-band superheterodyne electron spin resonance spectrometer (1966)
    Springer
    Zeitschrift für angewandte Mathematik und Physik 17 (1966), S. 404-416 
    Details
    ISSN: 1420-9039
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Physics
    Notes: Zusammenfassung Ein neuartiges Elektronenspinresonanz-Spektrometer für 24 GHz wird beschrieben. Das Instrument benützt als wesentliches Merkmal einen auf den Mikrowellenoszillator phasenstabilisierten Lokaloszillator. Hierbei kann der erstere mittels eines Peter-Strandberg-Phasenstabilisators entweder auf den Holraumresonator für ESR-Experimente oder auf die Harmonischen eines Kristalloszillators stabilisiert werden. Für die Mikrowellenbrücke wird eine Zirkulator-slidescrew tuner-Kombination verwendet, mit welcher leicht eine Isolation von 70 db erreichbar ist. Das Mischersignal von Lokal- und Hauptoszillator wird als Referenz für den Zwischenfrequenz-Phasenstabilisator verwendet. Die damit erzielte Kohärenz zwischen Referenz und Signal erlaubt eine weitgehende Elimination des Lokaloszillatorrauschens und der durch den Hohlraumoszillator verursachten nichtlinearen Amplituden- und Phasenverzerrungen. Die Wahl der Phase des Elektronenresonanz-Signals wird im Gegensatz zu bekannten Verfahren mittels Verzögerungsleitungen im Zwischenfrequenzkanal vorgenommen. Dadurch können Absorptions- und Dispersionssignal willkürlich gewählt werden, und die üblichen Schwierigkeiten der Phasenwahl im Mikrowellensystem fallen weg. Die bisher übliche Theorie der Empfindlichkeit des Instruments wird in einigen wichtigen Punkten eingehender dargestellt und speziell die Effekte der nichtlinearen Phasen-und Amplitudenverzerrungen durch den Hohlraumresonator auf das Verhältnis von Signal nahmen praktisch eliminiert werden können. Die dadurch mit dem Instrument bei sehr niedriger Mikrowellenleistung erzielbare hohe Empfindlichkeit von 2·1010 spins bei Zimmertemperatur wird an einem Beispiel demonstriert.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01594533
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  • 10
    Electronic Resource
    Electronic Resource
    Habitat preferences as patch selection of larval and emerging chironomids (Diptera) in a gravel brook (1992)
    Springer
    Aquatic ecology 26 (1992), S. 419-429 
    Details
    ISSN: 1573-5125
    Keywords: running waters ; population dynamics ; chironomids ; distribution ; patches
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Four common species of larval and emerging chironomids were investigated during 1981 and between 1984/1985 in an alpine gravel brook. The emergence patterns ofN. dubius, O. rivulorum andH. ornaticollis were significantly affected by fluctuations of the water level, while rises in water temperature tended to trigger the peaks in emergence of the same species and ofO. frigidus. N. dubius exhibited its main emergence activity over areas of bed sediment which had a lower mean water velocity or were discontinuously flooded. On the other hand, the imagines ofO. frigidus, O. rivulorum andH. ornaticollis reached peak densities in zones of the main current channel in the Seebach. The larvae of these species inhabited horizontally and vertically different areas of bed sediment depending on the developmental stage. Early instars ofN. dubius andH. ornaticollis preferred zones near the banks and reached their maximum densities in sediment depths of 10 to 20 cm and 20 to 30 cm, respectively. In contrast, the larvae ofO. frigidus andO. rivulorum reached their highest densities in the first 10 cm of the sediments with significant preferences for the zones of stronger water flow.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02255271
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