ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • Springer  (7)
  • American Institute of Physics (AIP)  (5)
  • 1
    Electronic Resource
    Electronic Resource
    Anisotropic electrical conduction in GaAs/In0.2Ga0.8As/Al0.3Ga0.7As strained heterostructures beyond the critical layer thickness (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 2941-2946 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The anisotropic conduction of GaAs/In0.2Ga0.8As/Al0.3Ga0.7As inverted high-electron-mobility transistor (HEMT) structures has been investigated. The heterostructures were grown by molecular-beam epitaxy on (100) GaAs substrates. The thickness of the pseudomorphic layer was increased stepwise (150–300 A(ring)) beyond the critical layer thickness as determined by the appearance of misfit dislocations. These mixed 60° dislocations surrounded by depletion regions were observed as straight dark lines in cathodoluminescence. The measured resistance Rs was higher in the [01¯1] direction than in the perpendicular [011] direction. At T=30 K the conduction ratio of these two directions exceeded 105 in the 300-A(ring)-thick layer. The magnitude and anisotropy of Rs was correlated with the anisotropic dislocation patterns resulting from the preferential generation of the α dislocations (parallel) [011] as compared to the orthogonal β dislocations (parallel) [01¯1]. In both directions Rs depended exponentially on the number of dark lines perpendicular to the probing current. Simultaneously, the functional form of the temperature-dependent Rs(T) strongly varied with layer thickness. The thin, still elastically strained layers showed the usual behavior of HEMT structures. For the thicker layers a completely different temperature dependence was gradually developing, eventually leading to an exponential increase of Rs with inverse temperature between 300 and 100 K. Below this range Rs(1/T) changed more slowly and leveled off at 30 K. All these features are convincingly explained by a model assuming that the electrons can surmount the insulating depletion barriers in the conducting channel by a thermally induced tunneling mechanism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351497
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Nonresonant electron and hole tunneling times in GaAs/Al0.35Ga0.65As asymmetric double quantum wells (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 56 (1990), S. 355-357 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Nonresonant carrier tunneling is investigated by time-resolved and time-averaged optical methods for a series of samples with various barrier thicknesses. The electron tunneling times decrease exponentially with the decrease of barrier thickness from 8 to 3 nm, and the trend is well described by a semiclassical model. Additional efficient hole tunneling is observed in the 3 nm barrier sample, and the time constant is of the order of 50 ps.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.102783
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Highly anisotropic electron mobilities of GaAs/In0.2Ga0.8As/Al0.3Ga0.7As inverted high electron mobility transistor structures (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 59 (1991), S. 2736-2738 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Anisotropic electron mobilities for GaAs/In0.2Ga0.8As/Al0.3Ga0.7As inverted high electron mobility transistor structures were observed using Hall effect measurements. If the In0.2Ga0.8As quantum-well thickness is below the critical layer thickness, a higher electron mobility in the 〈01–1〉 direction is observed in comparison to the 〈011〉 direction. Exceeding the critical layer thickness of the In0.2Ga0.8As quantum well results in a change in the behavior of the anisotropy, and a highly anisotropic electron mobility with a higher electron mobility in the 〈011〉 direction, in comparison to the 〈01–1〉 direction, is observed. With increasing In0.2Ga0.8As quantum-well width, the anisotropy increases. An increase of the anisotropy was also observed if the Hall-effect measurements were carried out at lower temperatures. The anisotropy in the electron mobility can be correlated to the occurrence of a highly asymmetric-dislocation density. The asymmetry in the dislocation density was observed using wavelength-selective catholuminescence measurements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.105900
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Green upconversion continuous wave Er3+:LiYF4 laser at room temperature (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 383-384 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report room-temperature upconversion pumped continuous wave laser emission of 1% Er3+:LiYF4 at 551 nm excited by a Ti:sapphire laser at 810 nm. Output powers of up to 40 mW with output coupling of 6.6% have been obtained by using nearly concentric resonator design.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.112335
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Principle differences between the transport properties of normal AlGaAs/InGaAs/GaAs and inverted GaAs/InGaAs/AlGaAs modulation doped heterostructures (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 60 (1992), S. 469-471 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The electrical properties of Al0.3Ga0.7As/InxGa1−xAs modulation doped heterostructures grown on GaAs substrates were studied. We found for the normal and inverted heterostructures principal differences of the transport properties. For an InAs mole fraction of 0.2 the inverted modulation doped heterostructures show a stronger decrease in the electron mobility of the two-dimensional electron gas if the critical layer thickness of the In0.2Ga0.8As layer is exceeded, in comparison to the normal heterostructures. This behavior can be explained by the relaxation process of the In0.2Ga0.8As layer. For InxGa1−xAs heterostructures with x(approximately-greater-than)0.3 the growth mode changes from two-dimensional to three-dimensional growth, which leads to interface roughness, degrading the transport properties of the normal heterostructure. Thus for high InAs mole fractions the inverted heterostructures show better transport properties in comparison to the normal heterostructures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.106637
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Thermal behaviour of carbohydrates studied by heat flow calorimetry (1983)
    Springer
    Journal of thermal analysis and calorimetry 28 (1983), S. 95-108 
    Details
    ISSN: 1572-8943
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Die Technik der Wärmeleitungs-Kalorimetrie wurde zur Untersuchung des thermischen Verhaltens von verschiedenen Kohlenhydraten zwischen 20°C und 270°C eingesetzt. Die Muster wurden in dicht verschlossenen Kapseln erhitzt. Der Temperaturbereich, in welchem exotherme Reaktionen infolge thermischer Zersetzung abliefen, änderte sich stark in Abhängigkeit vom untersuchten Kohlenhydrattyp. Reaktionsenthalpien von 44 Zuckern und Polysacchariden wurden ermittelt. Endotherme Phänomene, wie das Schmelzen oder das Verdampfen von Kristallwasser wurden auch beobachtet. Schmelztemperaturen und Schmelzenthalpien von 34 Zuckern und Zuckeralkoholen sind tabelliert. Kalorimetrische Daten der Kristallisation amorpher Saccharose, Cellobiose und Lactose werden diskutiert.
    Abstract: Резюме Метод калориметрии т еплового потока был использован для изуч ения термического поведения различных углеводов между 20 и 270°C. О бразцы анализировались наг ревом в закрытых ячейках. Вс ледствии термическо го разложения, интервал температур эксотерм ических реакций изменялся в ш ироких пределах в зав исимости от типа исследуемого углевода. Приведены э нтальпии реакций для 44 сахаров и полисахаридов. Наблю дались такие эндотермическ ие явления, как плавле ние или испарение кристалли зационной воды. Приведены температу ры плавления и энталь пии для 34 сахаров и многоатомн ых спиртов. Представлены калори метрические кривые, п оказывающие кристаллизацию амор фной сахарозы, целлобиозы и лактозы.
    Notes: Abstract The technique of heat flow calorimetry was used to study the thermal behaviour of different carbohydrates between 20°C and 270°C. The samples were analyzed by heating in sealed cells. The temperature range in which exothermic reactions, due to thermal decomposition, occurred varied widely depending on the type of carbohydrate investigated. Reaction enthalpies of 44 sugars and polysaccharides are given. Endothermic phenomena, such as fusion or vaporization of crystallized water, were also observed: fusion temperatures and enthalpies of 34 sugars and sugar alcohols are listed. Calorimetric curves showing crystallization of amorphous sucrose, cellobiose and lactose are also presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02105282
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Neutron scattering studies of Bi2Sr2Ca0.5Ho0.5Cu2O8+x (1991)
    Springer
    The European physical journal 85 (1991), S. 35-41 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Neutron scattering has been employed to study the crystalline electric field (CEF) interaction at the Ho3+ site in Bi2Sr2Ca0.5Ho0.5Cu2O8+x. The observed energy spectra exhibit a large number of broad but well-resolved CEF transitions between 1.2 and 73 meV, so that we have been able to unambiguously determine all nine CEF parameters required for the average orthorhombic symmetry. The unusually large line widths of the CEF transitions are shown to be related to the modulated structure. The CEF potential is essentially governed by the charge distribution of the CuO2 planes which turns out to be very similar as in HoBa2Cu3O7-x.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01387785
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Materials and device properties of pseudomorphic In x Ga1−x As/Al0.3Ga0.7As/GaAs high electron mobility transistors (0〈x〈0.5) (1991)
    Springer
    Applied physics 53 (1991), S. 109-113 
    Details
    ISSN: 1432-0630
    Keywords: 6855 ; 7280E ; 7340L
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Modulation doped Al0.3Ga0.7As/In x Ga1−x As/GaAs high electron mobility transistor structures for device application have been grown using molecular beam epitaxy. Initially the critical layer thickness for InAs mole fractions up to 0.5 was investigated. For InAs mole fractions up to 0.35 good agreement with theoretical considerations was observed. For higher InAs mole fractions disagreement occurred due to a strong decrease of the critical layer thickness. The carrier concentration for Al0.3Ga0.7As/In x Ga1−x As/GaAs high electron mobility transistor structures with a constant In x Ga1−x As quantum well width was investigated as a function of InAs mole fraction. If the In x Ga1−x As quantum well width is grown at the critical layer thickness the maximum carrier concentration is obtained for an InAs mole fraction of 0.37. A considerable higher carrier concentration in comparison to single-sided δ-doped structures was obtained for the structures with δ-doping on both sides of the In x Ga1−x As quantum well. Al0.3Ga0.7As/In x Ga1−x As/GaAs high electron mobility transistor structures with InAs mole fractions in the range 0–0.35 were fabricated for device application. For the presented field effect transistors best device performance was obtained for InAs mole fractions in the range 0.25–0.3. For the field effect transistors with an InAs mole fraction of 0.25 and a gate length of 0.15 μm a f T of 115 GHz was measured.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00323868
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    The physiological and nutritional importance of dietary fibre (1991)
    Springer
    Cellular and molecular life sciences 47 (1991), S. 181-186 
    Details
    ISSN: 1420-9071
    Keywords: Dietary fibre ; nutrition ; review ; health ; cholesterol ; minerals ; fermentation ; gastrointestinal tract ; cancer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Fibrous material is an integral part of the daily diet, and it exerts direct physiological effects throughout the gastrointestinal tract, in addition to affecting metabolic activities more indirectly. The interplay of these effects is responsible for the presumed desirable influence of fibre on weight regulation, carbohydrate and lipid metabolism, and on colon function. Numerous mechanisms of action have been identified which are related to the type and the physicochemical nature of the fibre. This review concentrates mainly on the serum cholesterol-lowering effect of dietary fibre, its colonic fermentation, and finally on some possible adverse effects that one should be aware of when consuming high amounts of dietary fibre.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01945423
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    facet.materialart.
    Unknown
    The physiological and nutritional importance of dietary fibre (1991)
    Springer
    Details
    Publication Date: 1991-02-01
    Print ISSN: 0014-4754
    Topics: Biology , Medicine
    Published by Springer
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...