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  • Electronic Resource  (140)
  • 2000-2004  (55)
  • 1990-1994  (84)
  • 1960-1964  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Nuclear spin dependence of polarization enhancement by multi-tilted foils studied by short-lived beta-emitters8B and12B (1993)
    Springer
    Hyperfine interactions 80 (1993), S. 1281-1286 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract In order to study the basic mechanism of polarization enhancement realized by the multitilted foil technique, nuclear polarization of short-lived beta-emitter8B(T1/2=769 ms,I π=2+) was induced. Utilizing up to ten tilted foils, the polarization enhancement was measured as a function of the foil numbers. The observed enhancement for8B was combined with the previous results for12B(I π=1+,T 1/2=20 ms) which has the same atomic configurations but different nuclear spin. Analyzing these results in the framework of the classical vector model, the essential features of the enhancement depending on the nuclear spin was disclosed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00567492
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  • 2
    Electronic Resource
    Electronic Resource
    Epitaxial τ (Mn,Ni)Al/(Al,Ga)As heterostructures: Magnetic and magneto-optic properties : 37th Annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 6121-6123 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ferromagnetic perpendicularly magnetized epitaxial thin films of τ (Mn,Ni)Al have been successfully grown on AlAs/GaAs heterostructures by molecular beam epitaxy. We have investigated the polar Kerr rotation and magnetization of τ MnAl and (Mn,Ni)Al as a function of Mn and Ni concentration. The largest polar Kerr rotation and remnant magnetization were obtained for Mn0.5Al0.5 thin films with values of 0.16° and 224 emu/cm3, respectively. We observed that the Kerr rotation and magnetization remained constant with Ni additions up to about 12 at. % and subsequently decreased with further Ni additions. We discuss these results and one possible method of enhancing the Kerr rotation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352721
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  • 3
    Electronic Resource
    Electronic Resource
    A molecular beam study of alkali promotion of NO sticking on Si(100): Local promotion in a single collision regime (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 97 (1992), S. 3781-3793 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Alkali–metal (K and Cs) promotion for sticking of nitrogen oxide molecule (NO) on Si(100) has been studied using a molecular beam method combined with an Auger electron spectroscopy (AES) and a laser ionization spectroscopy [resonance enhanced multiphoton ionization (REMPI)]. The observed sticking probability S shows a good correlation with alkali coverage, indicating that the alkali promotion is local in nature. The decay of S as a function of NO dose as observed with AES shows an anticorrelation with the evolution of the direct-inelastic scattering intensity as obtained with REMPI. This fact is understood as follows: since the direct-inelastic scattering occurs mostly in a single collision process with the surface, local alkali promotion is realized in a single collision of the incident NO molecule with the alkali–metal adsorbates. The decay of S as a function of NO dose is then analyzed with a reaction cross section. The evaluated reaction cross sections are close to the area of the 2×1 unit cell, and thus the estimated reaction radii are almost equal to but somewhat larger than the covalent radius of a K atom, with a increasing trend with alkali coverage. The alkali promotion is explained in terms of local electron charge transfer from the nonionized alkali adatoms to the affinity level of NO molecules based on the adatom density of state around EF.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.462959
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  • 4
    Electronic Resource
    Electronic Resource
    Tunneling magnetoresistance of a GaMnAs-based double barrier ferromagnetic tunnel junction (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 4673-4675 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Introduction of a ferromagnetic quantum well in a ferromagnetic tunnel junction is shown to greatly enhance the tunneling magnetoresistance (TMR) effect, due to spin filtering as well as energy filtering. We have theoretically analyzed resonant transmission probability of a magnetic double barrier heterostructure consisting of III–V based ferromagnetic semiconductor GaMnAs, and nonmagnetic semiconductor AlAs. Experimentally, we have observed very large TMR effect of such a system grown by low-temperature molecular-beam epitaxy, and have shown that some of the measured tunneling features are attributed to spin-dependent resonant tunneling. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.373126
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  • 5
    Electronic Resource
    Electronic Resource
    Negative ion production in a large semicylindrical ion source : Proceeding of the fourth International Conference on Ion Sources (1992)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 2699-2701 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A large semicylindrical negative ion source, whose dimensions are 34 cm in diameter and 104 cm in length, has been developed. By optimizing a chamber depth and a filter strength, a H− current of 650 mA (7.7 mA/cm2) was obtained at an arc condition of 1.3 Pa, 70 V, and 1200 A. In order to increase the H− current and to reduce an operating pressure, a small amount of Cs was injected. As a result, the H− current was increased from 550 mA (6.5 mA/cm2) to 850 mA (10 mA/cm2) under an arc power of 70 V×800 A. The most significant feature of the cesium effect was the reduction of the operating pressure. With maintaining the sufficient current of 670 mA (8 mA/cm2), the operating pressure could be lowered to 0.03 Pa. At this pressure, the highest gas efficiency of 20% was achieved.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1142827
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  • 6
    Electronic Resource
    Electronic Resource
    Long pulse operation of a cesium-seeded multicusp H− ion source : Proceeding of the fourth International Conference on Ion Sources (1992)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 2708-2710 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: It is demonstrated that a cesium-seeded volume H− ion source can be operated very stably for long pulse durations of up to 24 h. The source consists of a 20 cm cylindrical multicusp plasma generator and a 9 cm × 10 cm multiaperture extractor. By seeding a small amount of cesium, the source has produced 50 keV, 0.5 A, 1000 s H− ion beams with a current density of 14 mA/cm2. The cesium effect lasted for more than 24 h once 100 mg cesium was seeded before operation. Power flow measurement revealed that the heat loading of the ion source was low enough to operate the source in the dc mode.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1142830
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  • 7
    Electronic Resource
    Electronic Resource
    Interferometric measurements of the diameters of a single-crystal silicon sphere (1992)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 5320-5325 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A new interferometer has been developed for the accurate determination of the density of a silicon crystal, in which a single-crystal silicon sphere of nearly perfect geometry is placed in a Fabry–Perot etalon of accurately known plate distance, and the diameters are obtained by measuring the two gaps between the etalon and the adjacent surface of the sphere. A new method is used to measure the sum of the length of the two gaps by scanning the etalon against the sphere. Two wavelengths, 633 nm from a frequency-stabilized He–Ne laser and 441 nm from a free-running He–Cd laser, are used to determine the order of interference by applying the method of exact fractions. The diameter of about 94 mm has been measured with a resolution of 0.5 nm. Diameter measurements from uniformly distributed directions have shown that the mean diameter has been determined with a standard deviation of 8.6 nm, corresponding to 0.28 ppm in the volume determination. The total uncertainty of the volume is estimated to be 0.34 ppm. Effects of a thin oxide layer and impurities on the bulk density are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143447
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  • 8
    Electronic Resource
    Electronic Resource
    Anisotropic tunneling magnetoresistance in GaMnAs/AlAs/GaMnAs ferromagnetic semiconductor tunnel junctions (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 6745-6747 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have observed very large tunneling magnetoresistance (TMR) in Ga1−xMnxAs/AlAs/Ga1−xMnxAs ferromagnetic semiconductor tunnel junctions. A TMR ratio as high as 75% was obtained in a junction with a thin (1.5 nm) AlAs tunnel barrier when the magnetic field was applied along the [100] axis in the film plane. The TMR ratio decreased when the applied magnetic field direction was along the [11¯0] and [110]. This anisotropic TMR was found to be explained by the single-domain theory assuming cubic magnetic anisotropy with the easy axis of 〈100〉, which is induced by the zincblende-type Ga1−xMnxAs crystal structure. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1357832
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  • 9
    Electronic Resource
    Electronic Resource
    Magnetotransport properties of MnAs/GaAs/MnAs ferromagnet/semiconductor trilayer heterostructures (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 6695-6697 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have succeeded in growing MnAs/GaAs/MnAs ferromagnet/semiconductor trilayer heterostructures on GaAs(111)B substrates by molecular-beam epitaxy. Double-step features were observed in magnetization characteristics due to the difference in coercive force between the top and bottom MnAs layers. Magnetoresistance (MR) curves in current-in-plane geometry showed the spin-valve effect, which was caused by the change of the magnetic alignment of the two ferromagnetic MnAs layers from parallel to antiparallel orientation. Temperature dependence of the MR was also investigated. We infer that the positive temperature coefficient of the MR by the spin-valve effect suggests the heat (carrier) induced interlayer exchange coupling. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.372811
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  • 10
    Electronic Resource
    Electronic Resource
    Origin of transconductance oscillations in silicon-on-insulator metal–oxide–semiconductor field-effect transistors with an ultrathin 6-nm-thick active Si layer (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 5360-5364 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Transconductance oscillations were observed for silicon-on-insulator metal–oxide–semiconductor field-effect transistors with 50 nm channel length and 6 nm Si-layer thickness in the temperature range of 39–50 K. By investigating the temperature dependence of the oscillations it was found that the oscillations were caused by two reasons. One reason is the roughness at the Si/insulator interface responsible for the low-gate-voltage oscillations. The roughness results in different thicknesses of the Si layer along the channel, causing different quantized energy levels, which act as barriers for carriers moving in the channel. The other reason is the tunneling through the potential barrier at the p/n junctions between the contacts and the channel, which is responsible for the high-gate-voltage oscillations. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1459606
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