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  • 1
    Electronic Resource
    Electronic Resource
    Nanometer surface gratings on Si(100) characterized by x-ray scattering under grazing incidence and atomic force microscopy (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 1212-1216 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: During rapid melting and resolidification of As-implanted Si(100) by pulsed laser irradiation a periodic lateral grating has been created on the Si surface. Structure and perfection of the grating is investigated by specular and diffuse x-ray scattering under grazing incidence and exit angles. Using synchrotron radiation we find sharp, off-specular diffraction rods perpendicular to the sample surface. Their lateral separation is given by the periodicity of the grating (522±1 nm), which is nearly the same as the light wavelength (530 nm) used in laser annealing the samples. Intensity measurements along the diffraction rods are used to determine the detailed structure of the surface grating by fitting the experimental results with model calculations. A sinusoidal shape is found with an average amplitude of 6±1 nm. This structure is confirmed by atomic force microscopy studies. The x-ray method presented will be a unique tool also applicable in the case of buried lateral nanostructures which are not accessible by surface-sensitive techniques, e.g., scanning probe methods. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363864
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  • 2
    Electronic Resource
    Electronic Resource
    Sharpened electron beam deposited tips for high resolution atomic force microscope lithography and imaging (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 3732-3734 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We employ the vibrating tip of an atomic force microscope as a lithographic tool to mechanically pattern a thin photoresist layer covering a GaAs–AlGaAs heterostructure. High aspect ratio electron beam deposited tips, additionally sharpened in an oxygen plasma, are used to minimize the dimensions of the fabricated quantum electronic devices. The fabrication parameters of the tips and the sharpening process are investigated. With these ultrasharp tips we are able to produce lines and holes with periods down to 9 nm in photoresist. In addition, the very sharp tips yield substantial improvements in the imaging mode. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.115365
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  • 3
    Electronic Resource
    Electronic Resource
    Coulomb blockade in quasimetallic silicon-on-insulator nanowires (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 75 (1999), S. 3704-3706 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Using highly doped silicon-on-insulator (SOI) films, we demonstrate metallic Coulomb blockade in silicon nanowires at temperatures up to almost 100 K. We propose a process that leads to island formation inside the wire due to a combination of structural roughness and segregation effects during thermal oxidation. Hence, no narrowing of the SOI wire is necessary to form tunneling contacts to the single-electron transistors. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.125435
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  • 4
    Electronic Resource
    Electronic Resource
    Josephson junctions defined by a nanoplough (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 2051-2053 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We define superconducting constrictions by ploughing a deposited Aluminum film with a scanning probe microscope. The microscope tip is modified by electron-beam deposition to form a nanoplough of diamond-like hardness which allows the definition of highly transparent Josephson junctions. Additionally, a dc superconducting quantum interference device is fabricated in order to verify the junction's behavior. The devices are easily integrated in mesoscopic devices as local radiation sources and can be used as tunable on-chip millimeter-wave sources. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.122364
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  • 5
    Electronic Resource
    Electronic Resource
    Direct patterning of surface quantum wells with an atomic force microscope (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 2684-2686 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We employ an atomic force microscope to directly pattern the electron system of InAs–AlSb surface quantum wells. Sharp and sturdy electron beam deposited tips are developed to withstand the comparatively high ((approximate)μN) forces in the direct patterning process. By direct patterning the InAs surface quantum well we modulate the electron system without any mask. We are therefore able to directly transfer the excellent lithographic resolution of atomic force microscopy to an electron system. The magnetoresistance of such fabricated antidot arrays is discussed. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.122553
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  • 6
    Electronic Resource
    Electronic Resource
    Fabrication of Ti/TiOx tunneling barriers by tapping mode atomic force microscopy induced local oxidation (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 71 (1997), S. 1733-1735 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We use an atomic force microscope operating in a dynamic modus, commonly called tapping mode, to completely oxidise through thin 5 nm titanium films using the very local electric field between the tip and the sample. Tapping mode local oxidation minimizes tip degradation and therefore enhances resolution and reliability. By working under a controllable environment and measuring the resistance in situ while oxidising we are able to fabricate well-defined isolating Ti–TiOx–Ti barriers as small as 15 nm. Their conductance shows an exponential dependence on the oxide width, thereby identifying tunneling as the dominant conduction mechanism. From the nonlinear current-voltage characteristic a tunneling barrier height of 178 meV is derived. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.120019
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  • 7
    Electronic Resource
    Electronic Resource
    Si/Ge films on laterally structured surfaces: An x-ray study of conformal roughness (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 191-193 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: X-ray diffraction measurements in the region of small incidence and exit angles on thin amorphous silicon/germanium films on laterally structured surfaces are performed. From fits of the data we obtain directly how the Fourier components of the substrates propagate through the evaporated films without being influenced by the intrinsic statistical roughness of the interfaces. The results show that a replication factor extracted from a given model can be quantitatively tested with our measurements. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.116456
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  • 8
    Electronic Resource
    Electronic Resource
    Nanolithography with an atomic force microscope for integrated fabrication of quantum electronic devices (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 1775-1777 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We describe a novel technique using an atomic force microscope (AFM) for integrated nanometer-scale lithography on various mask materials such as photoresist or gold covering a mesa-etched GaAs-AlGaAs heterostructure at ambient conditions. The generated patterns can be transferred to the two-dimensional electron gas by wet chemical etching or by ion beam irradiation. We succeed in fabricating hole arrays with a periodicity down to 35 nm and a hole diameter of only a few nanometers. In magnetoresistance studies on so-called antidot devices with 95 nm period at T=4.2 K we can clearly observe commensurability oscillations, demonstrating the successful pattern transfer to the electron system. With the AFM we can also pattern lines of varying width and depth into prefabricated devices. © 1994 American Institue of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.112914
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  • 9
    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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  • 10
    Electronic Resource
    Electronic Resource
    Differential Role for IL-2 and IL-15 in the Inhibition of Apoptosis in Short Term Activated Human Lymphocytes (1997)
    Oxford, UK : Blackwell Science Ltd
    Scandinavian journal of immunology 45 (1997), S. 0 
    Details
    ISSN: 1365-3083
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Interleukin (IL)-15 is a newly described cytokine with properties similar to IL-2. Even though it does not share sequence homology with IL-2, both cytokines bind to the same receptor with the noted exception of a cytokine specific α-chain. In this study the authors compared IL-2 and IL-15 to determine their ability to rescue short term activated lymphocytes (phytohaemagglutinin stimulation of peripheral blood mononuclear cells for 6 days, followed by expansion in medium containing IL-2 for 2 days) from apoptotic cell death. The authors found that both IL-2 and IL-15 can inhibit induction of apoptosis in this experimental model with similar time and dose kinetics. On mRNA or protein levels induction of pro- and anti-apoptotic gene products like fasL, bcl-2, or bax with minor effects on fas/Apo-1 or bcl-xL was observed under culture conditions with both IL-2 and IL-15. Next, it was found that phytohaemagglutinin (PHA) blasts were less responsive (in terms of cellular proliferation and prevention from apoptosis) to IL-2 if signals through the α-chain were blocked, with no effect on β-chain specific monoclonal antibodies (MoAb). By contrast, IL-15 was less effective in induction of cellular proliferation and prevention of apoptosis if IL-2R β-chain specific MoAb were added to cell cultures. Testing intracellular signalling induced by IL-2 or IL-15, the authors found identical changes in tyrosine phosphorylation patterns in PHA blasts cultured in medium or under IL-2 or IL-15 stimulation. By contrast, they found consistent differences if PHA stimulated peripheral blood mononuclear cells (PBMC) were expanded in medium containing IL-15 (instead of IL-2). These IL-15 expanded PHA blasts showed a significantly increased percentage of apoptosis after growth factor withdrawal. Furthermore, IL-2 was more efficient than IL-15 in rescuing IL-15 expanded PHA blasts from apoptosis. In IL-15 expanded PHA blasts expression of IL-2R α-chain was lower than that in IL-2 expanded PHA blasts. A model presenting a differential role for IL-2 and IL-15 in inhibition of apoptosis in vivo is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3083.1997.d01-443.x
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