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  • 1
    Electronic Resource
    Electronic Resource
    Thermal effects in pulsed laser assisted scanning tunneling microscopy (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 2574-2580 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The thermal response of a tunneling tip after illumination of the apex with an ultrashort laser pulse of 1 ps duration is investigated. The finite element method is applied to calculate the resulting time-dependent temperature distribution and the thermal expansion taking into account the elastic properties of the tip material. The calculation reveals the three-dimensional movement of the tip apex. The expansion of the tip occurs within a few nanoseconds and after 10 μs the tip has almost reached its original length again. The bending of the tip due to the asymmetric illumination of the tip occurs on the same time scale and is of the same order of magnitude as the axial expansion. Under tunneling conditions the absolute magnitude of the expansion can lead to the formation of nanocontacts. This accounts for the laser induced nanostructuring of surfaces that has been reported in literature. The application of the thermal expansion as a fast switch for the tunneling current is proposed. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.372221
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  • 2
    Electronic Resource
    Electronic Resource
    Femtosecond laser assisted scanning tunneling microscopy (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 4851-4859 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The excitation of the tunneling junction of a scanning tunneling microscope using ultrashort laser pulses combined with detection of a tunneling current component which depends nonlinearly on the laser intensity allows, in principle, to simultaneously obtain ultimate spatial and temporal resolution. To achieve this goal, a laser system that produces ultrashort laser pulses is combined with an ultrahigh vacuum scanning tunneling microscope. The basic technical considerations are discussed and it is shown that atomic resolution can be achieved under pulsed laser excitation of the tunneling junction. The pulsed illumination gives rise to several contributions to the measured total current. Experimental evidence for signal contributions due to thermal expansion, transient surface potentials and multiphoton photoemission are presented. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1290706
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  • 3
    Electronic Resource
    Electronic Resource
    Instantaneous crystalline annihilation during normal grain growth in aluminum thin films (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 5331-5334 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The process of normal grain growth in unsupported thin aluminum film was studied in situ by heating the specimen during inspection in the transmission electron microscope. The growth mechanism was found to involve the instantaneous annihilation of a grain as a whole and its consumption by neighboring grains. This elementary process occurs in a time interval shorter than 0.04 s (the video camera time lag between two successive exposures), and it cannot be explained in terms of grain-boundary self-diffusion. Often the annihilation of a grain is followed by a cascade of similar events in its immediate neighborhood. It is possible that long-wave instabilities at the grain boundary grow through a critical stage in which the topological stability of the boundary is destroyed, yielding the spontaneous growth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.340398
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  • 4
    Electronic Resource
    Electronic Resource
    The role of the substrate in photoenhanced metalorganic chemical vapor deposition (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 296-298 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A GaAs laser diode has been used as the light source for the selective epitaxial growth of GaAs by photoenhanced metalorganic chemical vapor deposition (PE-MOCVD). The use of GaAs/InGaP layered structures as substrates for these experiments permitted to accurately control the availability of photoexcited carriers reaching the GaAs growth surface. The experimental results obtained rule out pure pyrolysis and photolysis as possible mechanisms responsible for the PE growth rate, and indicate that photoexcited carriers are directly involved in the PE process. The experimental data are consistent with a kinetic model that invokes surface recombination as the main physical mechanism for the PE growth rate effect. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.113523
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  • 5
    Electronic Resource
    Electronic Resource
    High temperature adduct formation of trimethylgallium and ammonia (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 55-57 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: High temperature gas phase reactions between trimethylgallium (TMG) and ammonia were studied by means of in situ mass spectroscopy in an isothermal flow tube reactor. The temperature, pressure, and reaction time were chosen to emulate the gas phase environment typical of the metal–organic vapor phase epitaxy (MOVPE) of GaN. The main gas phase species is [(CH 3)2Ga:NH2]x, where most probably x=3, resulting from the very fast adduct formation followed by elimination of methane. The further gas phase decomposition of this species proceeds through the stepwise elimination of methane. These studies indicate that little TMG exists within the growth ambient under most MOVPE growth conditions. The further gas phase reaction of [(CH3)2Ga:NH 2]x may be responsible for the strong dependence of the MOVPE GaN growth rate and uniformity commonly observed. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.118117
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  • 6
    Electronic Resource
    Electronic Resource
    Hot electron tunneling in femtosecond laser-assisted scanning tunneling microscopy (2002)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 81 (2002), S. 286-288 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The combination of scanning tunneling microscopy with femtosecond laser spectroscopy yields simultaneously ultimate spatial and temporal resolution. One possibility to realize this combination is the direct excitation of the tunnel junction in a pump–probe configuration and the detection of a tunnel current component that depends nonlinearly on the laser intensity. The laser-induced signal is expected to be very small, therefore a suitable sample material and a modulation technique is required. In measurements on a GaP(100) surface evidence for tunneling of hot electrons is obtained giving the possibility for local time-resolved tunneling spectroscopy. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1491280
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  • 7
    Electronic Resource
    Electronic Resource
    Silver nanoparticles on graphite studied by femtosecond time-resolved multiphoton photoemission (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 5428-5434 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Time-resolved multiphoton photoelectron spectroscopy is employed to study collective excitations and their decay dynamics in silver nanoparticles on highly oriented pyrolytic graphite. Resonant excitation of the surface plasmon in the silver nanoparticles with 400 nm femtosecond radiation allows to distinguish between photoemission from the nanoparticles and the substrate. This extends the method of time-resolved two-photon photoemission spectroscopy to inhomogeneous surfaces and permits to probe the dynamics of a confined electron gas. The multiphoton photoelectron spectra, the polarization dependence of the photoelectron yield and the time-resolved measurements reveal the double excitation of the surface plasmon and allow the identification of two different decay channels of the collective excitation. The multiply excited plasmon transfers its total excitation energy to a single photoelectron or decays into at least two single-particle excitations which share the total energy. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.481127
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  • 8
    Electronic Resource
    Electronic Resource
    Photoemission from multiply excited surface plasmons in Ag nanoparticles (2000)
    Springer
    Applied physics 71 (2000), S. 547-552 
    Details
    ISSN: 1432-0630
    Keywords: PACS: 78.47.+p; 73.20.Mf; 79.60.Jv; 79.60.-I; 81.05.Ys
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. Two-photon photoemission spectroscopy using femtosecond laser pulses is used to investigate the excitation and decay mechanisms of the surface plasmon resonance in Ag nanoparticles grown on graphite. The resonant excitation of this collective excitation leads to a two-orders-of-magnitude-enhanced two-photon photoemission yield from a graphite surface with Ag nanoparticles compared to the yield from pure graphite. From the shape of the photoemission spectra, the polarization dependence of the photoemission yield and the excitation probabilities for different excitation pathways we conclude that excitation with 400-nm femtosecond laser pulses leads to the coherent multiple excitation of the surface plasmon in the Ag nanoparticles. This multiply excited plasmon mode can decay via the coupling to a single-particle excitation leading to the emission of an electron if its final state is located in the continuum. The surface plasmon in metallic nanoparticles is a model system to investigate collective excitations in multiphoton processes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003390000712
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  • 9
    Electronic Resource
    Electronic Resource
    Time-resolved two-photon photoemission spectroscopy of HOPG and Ag nanoparticles on HOPG (1999)
    Springer
    Applied physics 68 (1999), S. 439-445 
    Details
    ISSN: 1432-0649
    Keywords: PACS: 78.47.+p; 79.60.Jv; 79.60.-i; 82.65.Jv
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003400050646
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  • 10
    Electronic Resource
    Electronic Resource
    Resolution limits of microscopy through scattering layers
    Amsterdam : Elsevier
    Optics Communications 110 (1994), S. 492-496 
    Details
    ISSN: 0030-4018
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0030-4018(94)90237-2
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