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  • 1
    Electronic Resource
    Electronic Resource
    Stretch dynamics of flexible dendritic polymers in solution (2001)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 114 (2001), S. 2430-2441 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We study the stretch dynamics of flexible dendritic polymers (dendrimers and stars) under external forces. We work in the framework of the bead-spring model with hydrodynamic interactions (HI) and take spacers of different length into account. The applied fields may, e.g., be of mechanical or electrical origin. We study the motion of a specific monomer, the time evolution of the stretch (the mean distance of the monomer on which the force acts from the center of mass of the polymer) and also the elastic moduli. We analyze how these dynamic properties depend on the underlying topology, i.e., on the number of generations for dendrimers and the length and number of branches for stars. As a special point we assess in how far the HI method utilized here (the Kirkwood–Riseman scheme) is stable for dendritic structures. Characteristic for the topology is the intermediate dynamics (between short and long times). It turns out that, different from stars, for dendrimers the stretch dynamics is for intermediate times close to logarithmic; hence the crossover in behavior at intermediate times is characteristic of the polymer's topology. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1334660
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  • 2
    Electronic Resource
    Electronic Resource
    Plasma enhanced metalorganic chemical vapor deposition of amorphous aluminum nitride (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 5825-5831 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Plasma enhanced deposition of amorphous aluminum nitride (AlN) using trimethylaluminum, hydrogen, and nitrogen was performed in a capacitively coupled plasma system. Temperature was varied from 350 to 550 °C, and pressure dependence of the film structure was investigated. Films were characterized by Fourier transform infrared, Rutherford backscattering (RBS), ellipsometry, and x-ray diffraction (XRD). The films are amorphous in nature, as indicated by XRD. Variations in the refractive index were observed in ellipsometric measurements, which is explained by the incorporation of carbon in the films, and confirmed by RBS. Capacitance–voltage, conductance–voltage (G–V), and current–voltage measurements were performed to reveal bulk and interface electrical properties. The electrical properties showed marked dependence on processing conditions of the AlN films. Clear peaks as observed in the G–V characteristics indicated that the losses are predominantly due to interface states. The interface state density ranged between 1010 and 1011 eV−1 cm−2. Annealing in hydrogen resulted in lowering of interface state density values. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1413484
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  • 3
    Electronic Resource
    Electronic Resource
    Electrical properties of fluorinated amorphous carbon films (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 4417-4421 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have studied the capacitance–voltage (C–V), conductance–voltage (G–V), and current–voltage characteristics of fluorinated amorphous carbon (a-C:Fx) films using metal/a-C:Fx/Si and metal/a-C:Fx/metal structures, respectively. Samples annealed in a vacuum were also studied. The C–V curves of the as-deposited sample are stretched about the voltage axis. Interface state density of 4.1×1011 cm−2 eV−1 at the midgap was calculated. Annealing the sample deposited on Si in a vacuum caused more frequency dispersion in the C–V and G–V curves, probably due to the diffusion of carbon into silicon. The bulk density of states for samples deposited on metal, measured by space-charge-limited current technique, decreased from 4×1018 eV−1 cm−3 for the as-deposited sample, to 7×1017 eV−1 cm−3 for the annealed sample. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1353804
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  • 4
    Electronic Resource
    Electronic Resource
    Pulse stretching due to partial temporal overlap of two modes in a TEA CO2 laser (2000)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 71 (2000), S. 579-580 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Pulse duration as long as 14 μs has been obtained from a single longitudinal mode TEA CO2 laser. Such stretching occurred under conditions for which oscillation on a higher order transverse mode followed that on the TEM00 mode with partial temporal overlap between the two. Control of the intracavity aperture size in conjunction with cavity length tuning helped realize such an oscillation condition. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1150246
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  • 5
    Electronic Resource
    Electronic Resource
    Versatile cavity for optically pumped molecular lasers (2001)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 72 (2001), S. 1343-1345 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We describe here an optically pumped molecular laser cavity configuration which allows near total transmission of pump radiation into the cavity maintaining, at the same time, a high Q value at the lasing wavelength. This also has built into it the capability of elimination of unabsorbed pump radiation, isolation of pump cavity, and suppression of self-focusing effect. The efficient performance of this versatile cavity has been demonstrated in the pulsed operation of a NH3 laser pumped by a transversely excited atmospheric CO2 laser. The low lasing threshold observed here suggests that this cavity can also be employed for the continuous operation of such lasers. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1338488
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  • 6
    Electronic Resource
    Electronic Resource
    Diode-less operation of a resonantly charged repetitive high voltage pulser circuit (2001)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 72 (2001), S. 2505-2507 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We report here that the unique geometry of the rotating dielectric spark gap allows the diode-less operation of a command resonant charging pulser network. An average power of about 3.5 kW with a peak value of 75 MW was switched at a repetition rate of 600 Hz into a dummy load resembling a typical TEA CO2 laser. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1357226
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  • 7
    Electronic Resource
    Electronic Resource
    Electronic linear energy transfer dependent molecular structural growth in polyethylene terephthalate (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 4922-4927 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thin films (13 μm) of polyethelene terephthalate (PET) are irradiated by different swift metallic heavy ions (180 MeV Ag14+ and 200 MeV Au15+) with the projectile linear energy transfer (LET) (∼10–14 keV/nm), respectively. LET dependence on the molecular structural changes in PFT irradiated at different ion fluences has been studied by the Fourier transform infrared spectroscopy. The study has revealed that beyond a critical LET entirely different pathways of amorphization beginning with partial recrystallization at lower ion fluence impact occurs in PET, contrary to the earlier established results. At considerably higher LET (∼14 keV/nm), the most characteristic crystalline stretching and bending vibration bands such as at 850 cm−1 (CH2 rocking), 972 cm−1 (C(Double Bond)O stretching), 1341 and 1471 cm−1 (CH2 bending) in PET have shown a significant rise in the respective infrared absorbance intensities upon lower ion fluence (∼1011 ions/cm2) impact. The absence of previously reported unsaturations such as alkynes at both the LET beam used are also observed. Interestingly, the aromatic system also appears to be unstable and participating in the modification process, particularly at the higher LET (∼14 KeV/nm). Possible interpretations are discussed. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1462424
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  • 8
    Electronic Resource
    Electronic Resource
    Electrical properties of amorphous silicon carbide films (2002)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 80 (2002), S. 3439-3441 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The interfacial properties of silicon carbide films on silicon substrate, using capacitance–voltage (C–V) and conductance–voltage techniques have been studied. The C–V characteristics observed largely depended on processing conditions. An interface state density of 2.38×1010 eV−1 cm−2 at the midgap was calculated for this sample. When CF4 was added to the precursors, the C–V curves were observed to have a "ledge" at the end of the accumulation region, indicative of the presence of additional localized defect states that respond to the applied ac signal. An interface state density of 2.11×1011 eV−1 cm−2 at the midgap was observed for this sample. However fluorination in plasma caused the etching of the weak bond, and hence a reduction in the fixed charge density and hysteresis. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1476389
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  • 9
    Electronic Resource
    Electronic Resource
    Recrystallization in polyvinylidene fluoride upon low fluence swift heavy ion impact (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 78 (2001), S. 4136-4138 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thin films (9 μm) of polyvinylidene fluoride (PVDF) are irradiated by swift heavy ions (180 MeV Ag14+) in the fluence range 1×1010–1×1012ions/cm2 with an electronic linear energy transfer LET∼11 keV/nm. In sharp contrast to the previous results, the most characteristic crystalline asymmetric and symmetric "CH2" doublets (located at 3025 and 2985 cm−1), have shown remarkable increase in their respective Fourier transform infrared (FTIR) absorbance intensities upon low fluence ion impact (1010 ions/cm2). This increase in absorbance is in consonance with the simultaneous decrease of the transmission intensities of other crystalline bending vibration bands located at 532 (CF2 bending), 614, 796, and 975 cm−1 (all due to CH2 bending) at the similar ion fluence. It appears most probable from the results that, being a polar polymer, the molecular dipoles in PVDF forming a hydrogen bond network get realigned upon irradiation into a highly ordered state of chain molecules in the crystalline regions and create volume elements as crystallites. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1376664
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  • 10
    Electronic Resource
    Electronic Resource
    Blue cooperative upconversion in Yb3+-doped multicomponent sol-gel-processed silica glass for three-dimensional display (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 76 (2000), S. 1978-1980 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We propose using blue cooperative upconversion of ytterbium (Yb3+) ions produced by a one-color one-beam pumping scheme for a three-dimensional fluorescence display. The results are presented using a diode laser as a pump source emitting at 973 nm, and the sample used was a multicomponent sol-gel-processed silica glass (1 mol. % of Yb3+). The maximum absolute blue power emitted was ∼1 μW for an excitation power of ∼900 mW. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.126228
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