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  • 1
    Electronic Resource
    Electronic Resource
    Field-effect induced electron channels in a Si/Si0.7Ge0.3 heterostructure (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 3917-3919 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Size effects in field-effect induced wires imposed upon a high-mobility Si/Si0.7Ge0.3 heterostructure were studied by magnetotransport. Spatial separation of the electron channels was accomplished by means of a periodically modulated Schottky gate. The magnetoresistance parallel to the wires shows a well-pronounced peak at magnetic fields 〈0.3 T at a gate bias ≤0 V. This maximum results from diffuse boundary scattering and proves the existence of spatially separated electron channels. From its position wire widths varying from 0.14 to 0.28 μm can be estimated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357401
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  • 2
    Electronic Resource
    Electronic Resource
    Fabrication of lateral npn- and pnp-structures on Si/SiGe by focused laser beam writing and their application as photodetectors (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 6455-6460 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Local doping with focused laser beam writing was used to fabricate lateral npn- and pnp-structures on modulation-doped Si/SiGe heterostructures. The electrical and optical properties of the achieved lateral potential modulation were analyzed for local B-doping on n-type Si/SiGe and P- and Sb-doping on p-type SiGe/Si. Focused laser beam written doped lines show a strongly nonohmic IV characteristic indicating the formation of a local insulating barrier in the two-dimensional carrier system. Such lateral structures can be used as photosensitive devices with responsivities up to 106 A/W combined with a spatial resolution on the μm scale. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.364428
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  • 3
    Electronic Resource
    Electronic Resource
    One-dimensional transport of electrons in Si/Si0.7Ge0.3 heterostructures (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 833-835 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetotransport of high-mobility electrons in quasi-one-dimensional quantum wires in Si/Si0.7Ge0.3 heterostructures is studied. Arrays of shallow and deep etched wires with a period of 480 nm are defined by laser holography and patterned by reactive ion etching. Typical features of transport in narrow electron channels, such as oscillations due to the depopulation of quasi-one-dimensional subbands and an anomalous resistance maximum at low magnetic fields are observed. The narrowest channels have an effective width of ≈70 nm and a sublevel spacing of 1 meV. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.113437
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  • 4
    Electronic Resource
    Electronic Resource
    In-plane-gate transistors fabricated from Si/SiGe heterostructures by focused ion beam implantation (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 1579-1581 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: One-dimensional in-plane-gate (IPG) transistors in the Si/Ge system are fabricated and characterized by focused ion implantation of Ga+ ions on lines into high-mobility two-dimensional electron gases confined in Si/SiGe heterostructures. Transistor operation is demonstrated up to temperatures of T=77 K. The depletion length of the FIB written lines and the saturation drift velocity of the electrons in the Si layer under tensile strain can be estimated from series of samples with different geometric widths of the channel. The IPG transistors presented here are the first based on Si, pushing this elegant transistor concept towards the important Si technology. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.114945
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  • 5
    Electronic Resource
    Electronic Resource
    Fabrication of n- and p-channel in-plane-gate transistors from Si/SiGe/Ge heterostructures by focused laser beam writing (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 3025-3027 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Focused laser beam writing is applied for thermally activated diffusion of dopants into strained Si/Ge modulation-doped heterostructures. Lateral p- and n-type potential barriers of sub-μm width are achieved by local diffusion of boron and antimony into n- and p-type heterostructures, respectively. The potential modulation is determined from the temperature dependence of the thermionic current over the barrier. These npn and pnp structures can be used to fabricate in-plane-gate transistors which show transistor action up to room temperature. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.115565
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  • 6
    Electronic Resource
    Electronic Resource
    Dynamic cracking resistance of ChSN 15313 steel (1984)
    Springer
    Strength of materials 16 (1984), S. 108-114 
    Details
    ISSN: 1573-9325
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Conclusions 1. The method of stereofractographic examination of the stretched zone on two fracture halves was used to determine the values of 2h for ChSN 15313 steel in the temperature range 73–253°K in dynamic loading. 2. A correlation was found in the given temperature range between the height of the stretched zone and crack opening displacement predicted by the mathematical models. The coefficient of linear correlation between 2h and K2 Qd/Eσ0.2d is equal to 0.9. 3. The stretched zone does not form at temperatures below 153°K. 4. The correlation between JId and δc in dynamic loading was verified by means of experiments. The derived equation makes it possible to determine the dynamic fracture toughness KJd on the basis of the values of KQd, the dynamic yield stress, and the height of the stretched zone 2h, characterizing the plastic crack opening displacement, in the conditions of elastoplastic loading. 5. The results indicate that the quantitative stereofractographic method can be used successfully for evaluating the fracture resistance of the materials, especially in the impact loading conditions in which the determination of crack opening displacement by other methods is difficult.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01530197
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  • 7
    Electronic Resource
    Electronic Resource
    Bose-Einstein transition in a dilute interacting gas (2001)
    Springer
    The European physical journal 24 (2001), S. 107-124 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 05.30.Jp Boson systems – 05.30.-d Quantum statistical mechanics – 03.75.Fi Phase coherent atomic ensembles; quantum condensation phenomena
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: We study the effects of repulsive interactions on the critical density for the Bose-Einstein transition in a homogeneous dilute gas of bosons. First, we point out that the simple mean field approximation produces no change in the critical density, or critical temperature, and discuss the inadequacies of various contradictory results in the literature. Then, both within the frameworks of Ursell operators and of Green's functions, we derive self-consistent equations that include correlations in the system and predict the change of the critical density. We argue that the dominant contribution to this change can be obtained within classical field theory and show that the lowest order correction introduced by interactions is linear in the scattering length, a, with a positive coefficient. Finally, we calculate this coefficient within various approximations, and compare with various recent numerical estimates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100510170028
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  • 8
    Electronic Resource
    Electronic Resource
    Bose-Einstein condensation in interacting gases (1999)
    Springer
    The European physical journal 10 (1999), S. 739-760 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 05.30.Jp Boson systems - 05.30.-d Quantum statistical mechanics - 03.75.Fi Phase coherent atomic ensembles; quantum condensation phenomena
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: We study the occurrence of a Bose-Einstein transition in a dilute gas with repulsive interactions, starting from temperatures above the transition temperature. The formalism, based on the use of Ursell operators, allows us to evaluate the one-particle density operator with more flexibility than in mean-field theories, since it does not necessarily coincide with that of an ideal gas with adjustable parameters (chemical potential, etc.). In a first step, a simple approximation is used (Ursell-Dyson approximation), which allow us to recover results which are similar to those of the usual mean-field theories. In a second step, a more precise treatment of the correlations and velocity dependence of the populations in the system is elaborated. This introduces new physical effects, such as a change of the velocity profile just above the transition: the proportion of atoms with low velocities is higher than in an ideal gas. A consequence of this distortion is an increase of the critical temperature (at constant density) of the Bose gas, in agreement with those of recent path integral Monte-Carlo calculations for hard spheres.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100510050905
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  • 9
    Electronic Resource
    Electronic Resource
    Ursell operators in statistical physics of dense systems: the role of high order operators and of exchange cycles (2002)
    Springer
    The European physical journal 25 (2002), S. 463-478 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 05.30.-d Quantum statistical mechanics – 05.20.Jj Statistical mechanics of classical fluids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: The purpose of this article is to discuss cluster expansions in dense quantum systems, as well as their interconnection with exchange cycles. We show in general how the Ursell operators of order l≥ 3 contribute to an exponential which corresponds to a mean-field energy involving the second operator U2, instead of the potential itself as usual - in other words, the mean-field correction is expressed in terms of a modification of a local Boltzmann equilibrium. In a first part, we consider classical statistical mechanics and recall the relation between the reducible part of the classical cluster integrals and the mean-field; we introduce an alternative method to obtain the linear density contribution to the mean-field, which is based on the notion of tree-diagrams and provides a preview of the subsequent quantum calculations. We then proceed to study quantum particles with Boltzmann statistics (distinguishable particles) and show that each Ursell operator Un with n≥ 3 contains a “tree-reducible part”, which groups naturally with U2 through a linear chain of binary interactions; this part contributes to the associated mean-field experienced by particles in the fluid. The irreducible part, on the other hand, corresponds to the effects associated with three (or more) particles interacting all together at the same time. We then show that the same algebra holds in the case of Fermi or Bose particles, and discuss physically the role of the exchange cycles, combined with interactions. Bose condensed systems are not considered at this stage. The similarities and differences between Boltzmann and quantum statistics are illustrated by this approach, in contrast with field theoretical or Green's functions methods, which do not allow a separate study of the role of quantum statistics and dynamics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjb/e20020052
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  • 10
    Electronic Resource
    Electronic Resource
    On slip-induced cleavage crack nucleation in iron and low-carbon steel (1970)
    Springer
    Czechoslovak journal of physics 20 (1970), S. 498-500 
    Details
    ISSN: 1572-9486
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01698410
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