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  • 1
    Digitale Medien
    Digitale Medien
    Effects of high-temperature annealing on the dielectric function of Ta2O5 films observed by spectroscopic ellipsometry (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 3012-3014 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Postdeposition annealing of high-k dielectric Ta2O5 films to eliminate contaminations can adversely cause the films to crystallize, which can be detrimental to their complementary metal–oxide–semiconductor device performances. In this letter, we will show that spectroscopic ellipsometry can be used to quickly and nondestructively detect such crystallization by identifying the two relatively sharp absorption peaks at 4.7 and 5.2 eV in the complex dielectric function of the films. Such peaks are absent in amorphous Ta2O5 films. In general, these sharp structures in the dielectric function are expected from the presence of long-range order in materials, which produces singularities in their interband density of states. Using this approach, we will show that Ta2O5 films become crystalline when annealed at or above 750 °C and remain amorphous below 700 °C. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1324730
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  • 2
    Digitale Medien
    Digitale Medien
    Spectroscopic ellipsometry characterization of high-k dielectric HfO2 thin films and the high-temperature annealing effects on their optical properties (2002)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 80 (2002), S. 1249-1251 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The optical properties of a set of high-k dielectric HfO2 films annealed at various high temperatures were determined by spectroscopic ellipsometry. The results show that the characteristics of the dielectric functions of these films are strongly affected by high temperature annealing. For a sample annealed at 600 °C, the film becomes polycrystalline, and its dielectric function displays a distinctive peak at 5.9 eV. On the other hand, the film remains amorphous without the 5.9 eV feature after 500 °C annealing. To model the dielectric functions, the Tauc–Lorentz dispersion was successfully adopted for these amorphous and polycrystalline films. The absorption edge was observed to shift to a higher energy at a high temperature annealing. Defects in the films were shown to relate to the appearance of a band tail above the absorption edge, and they appear to diminish with high temperature annealing. © 2002 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1448384
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  • 3
    Digitale Medien
    Digitale Medien
    The Northeast Water polynya, Greenland Sea (1994)
    Springer
    Polar biology 14 (1994), S. 491-503 
    Details
    ISSN: 1432-2056
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract During a pilot study in June 1991 meso-and macrozooplankton investigations were carried out in the region of the Northeast Water (NEW), a polynya located off Northeast Greenland at about 80°N. The mesozooplankton collected by bongo net was dominated by the large herbivorous copepods Calanus glacialis, C. hyperboreus and C. finmarchicus. At most stations the Calanus populations consisted of overwintering stages, except for an ice-free site in the northwestern corner of the study area, where young copepodids of C. hyperboreus and C. glacialis occurred. Young C. finmarchicus were only found at stations influenced by Atlantic water masses, whereas C. glacialis was the prevailing species on the East Greenland shelf. Egg production of this species was variable, but spawning activity appeared to be related to ambient chlorophyll a concentrations. Carbon requirements of herbivorous Zooplankton were estimated from egg production rates of C. glacialis. Due to low mesoplankton biomass, a mean of only 10% (ranging from 〈1% to 53%) of the phytoplankton carbon were grazed. Macrozooplankton was collected at three stations by a Rectangular Midwater Trawl (RMT 1+8). Major components were chaetognaths, hyperiid amphipods and large copepods. Macroplankton biomass was extremely low (1–3 mg AFDW m−3), about one order of magnitude less than that of the mesoplankton. Based on these limited data we hypothesize that macroplankton plays only a minor role as food for higher trophic levels and as predators controlling mesoplankton in the NEW polynya. These findings seem todisprove the concept of a rich pelagic community in the polynya amongst “a desert of ice”. They do, however, fit well with the notion of strong pelago-benthic coupling of primary production supporting a rich benthos within the polynya area.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00239054
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  • 4
    Digitale Medien
    Digitale Medien
    Assessment of renal artery stenosis by phase-contrast magnetic resonance angiography (1993)
    Springer
    European radiology 3 (1993), S. 493-498 
    Details
    ISSN: 1432-1084
    Schlagwort(e): Renal artery obstruction ; Magnetic resonance ; Blood flow velocity ; Hypertension, renal
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Three-dimensional (3D) phase-contrast magnetic resonance angiography (MRA) and velocity-encoded cine magnetic resonance (VEC-MR) imaging were performed in 23 subjects to assess the severity of renal artery stenosis. MRA was used for detection of stenosis, demonstrating a sensitivity of 100% and a specificity of 80%; the severity of stenosis was overestimated in 33%. VEC-MR was used to quantify the renal flow oattern and was successful in 11 subjects. Mean blood flow of normal renal arteries (420 +- 107 ml/min) was significantly higher (P 〈 0.01) than mean blood flow of stenotic arteries (131 +- 46ml/min). The flow profile displayed both systolic and diastolic peaks in 75% of the normal arteries, while the flow in stenotic arteries showed only a single systolic peak in all cases. The systolic peak in stenotic arteries occurred significantly later (32 +- 3% of the period of one cardiac cycle) than in normal subjects (21 +- 7%) (P 〈 0.05). Phase-contrast MR is likely to gain considerable importance in the noninvasive aetection and quantification of renal artery stenosis.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00169596
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  • 5
    Digitale Medien
    Digitale Medien
    Reactivity and magnetism of Fe/InAs(100) interfaces (2002)
    Springer
    The European physical journal 28 (2002), S. 305-313 
    Details
    ISSN: 1434-6036
    Schlagwort(e): PACS. 61.10.Ht X-ray absorption spectroscopy: EXAFS, NEXAFS, XANES, etc. – 68.35.Fx Diffusion; interface formation – 75.70.Ak Magnetic properties of monolayers and thin films – 82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract: Interface reaction and magnetism of epitaxially-grown Fe on InAs(100) are studied by core-level photoemission (As 3d and In 4d) and Fe 2p X-ray magnetic circular dichroism using synchrotron radiation. The reactivity of Fe/InAs(100) is relatively low compared to that of other interfaces involving deposition of 3d metals on III-V semiconductors. As a consequence, we observe a magnetic signal at Fe L2, 3 edges for the lowest thicknesses studied (1 ML). The atomic magnetic moment reaches a value close to that of the bulk α-Fe (2.2 μ B) for Fe coverages exceeding 5 ML. A ferromagnetic compound with approximate stoichiometry of FeAs is formed at the interface. The orbital magnetism represents between 12 and 20% of the total momentum, due to 3d density of states depletion and to crystal-field modification of the electronic levels. These properties make the Fe/InAs(100) interface very promising for spin-tunneling devices.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1140/epjb/e2002-00234-6
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  • 6
    Digitale Medien
    Digitale Medien
    On a class of hybrid methods for smooth constrained optimization (1992)
    Springer
    Journal of optimization theory and applications 73 (1992), S. 465-499 
    Details
    ISSN: 1573-2878
    Schlagwort(e): Nonlinear programming algorithms ; locally superlinearly convergent methods ; globally convergent methods ; hybrid techniques
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Abstract With reference to smooth nonlinearly constrained optimization problems, we consider combinations of locally superlinearly convergent methods with globally convergent ones. The aim of this paper is threefold: to give a survey on well-known as well as possible unknown hybrid optimization methods, based on a special construction principle; to present a general convergence result for the class of hybrid algorithms; and to derive further methods for this class with new convergence properties.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00940052
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  • 7
    Digitale Medien
    Digitale Medien
    Surface roughening during depth profiling by Secondary Ion Mass Spectrometry (SIMS) in GaAlAs and GaAs (1991)
    Springer
    Fresenius' Zeitschrift für analytische Chemie 341 (1991), S. 31-34 
    Details
    ISSN: 1618-2650
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary During bombardment of Ga1−xAlxAs and GaAs with oxygen we found an abrupt transition to higher sputter rates, change of the useful yield and significant increase of surface roughness at a well defined depth, which is essentially deeper than the penetration depth of the primary ions. Using oxygen and cesium as primary ions ‘varying’ energy and angle of incidence, residual gas pressure and matrix composition their effects on the phenomena were investigated. Although some remarkable properties of the sample modification process could be found, no theoretical description can be given up to now.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00322102
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  • 8
    Digitale Medien
    Digitale Medien
    Polarisation effects in electron transfer reactions with laser excited Na(3P) at medium energies (1994)
    Springer
    The European physical journal 30 (1994), S. 211-215 
    Details
    ISSN: 1434-6079
    Schlagwort(e): 34.70
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We report new experimental data for the investigation of the role of electronic orbital alignment and orientation in charge transfer processes, in the medium energy range where the collision velocityv c and the velocity of the active electronv e are of the same order of magnitude. The results obtained for the H 2 + -Na(3p) and He+-Na(3p) collisions are discussed in comparison with the experimental and theoretical findings obtained for the H+-Na(3p) system. Recent time-of-flight measurements for charge transfer in Li+-Na(3s and 3p) collisions are also presented.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01426075
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  • 9
    Digitale Medien
    Digitale Medien
    Collision spectroscopy with aligned and oriented atoms (1991)
    Springer
    The European physical journal 18 (1991), S. 231-234 
    Details
    ISSN: 1434-6079
    Schlagwort(e): 34.00 ; 34.70 ; 32.80
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Neutralisation processes in 0.15–1.5 keV collisions of H− with Na atoms in the 3s ground state or in the excited 3p state have been investigated by means of time-of-flight analysis of the neutral H atoms produced. The H− - Na(3p) system, investigated here for the first time, is particularly interesting since the entrance channel is embedded in the [H - Na(3s)] +e − continuum, enabling Penning detachment to occur. The measured relative neutralisation cross section ratios σ(3p)/σ(3s) decrease from 3 to 1.6 with increasing energy. Based on earlier published results for σ(3s), σ(3p) total cross sections exceeding 100 Å2 are estimated.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01437076
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  • 10
    Digitale Medien
    Digitale Medien
    Synthese von 2-aminosubstituierten 4,5-Dihydro-1,3-thiazolenHerrn Professor Dr. E. Hoyer zum 60. Geburtstag gewidmet (1991)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 333 (1991), S. 407-412 
    Details
    ISSN: 0021-8383
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Synthesis of 2-Amino-Substituted 4,5-Dihydro-1,3-thiazoles.The reaction of 2-substituted 4-methallylthiosemicarbazides 1 with carbonyl compounds catalyzed by weak acids gives thiosemicarbazones 2 and 1,2,4-triazolidine-3-thiones 3. By contrast under strong acidic conditions the reaction occurs by electrophilic cyclisation with participation of the methallyl and thiono groups, and 4,5-dihydro-1,3-thiazoles 5 are formed after neutralisation. The electrophilic cyclisation of N-methallyl substituted thioureas 6 and 1,4-disubstituted thiosemicarbazides 7 is also described.
    Zusätzliches Material: 4 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/prac.19913330305
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