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  • 1
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    Operation of an ungated diamond field-emission array cathode in a L-band radiofrequency electron source (2014)
    American Institute of Physics (AIP)
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    Publikationsdatum: 2014-07-01
    Beschreibung: We report on the operation of a field-emitter-array cathode in a conventional L-band radio-frequency electron source. The cathode consisted of an array of ∼10 6 diamond tips on pyramids. Maximum current on the order of 15 mA was reached and the cathode did not show appreciable signs of fatigue after weeks of operation. The measured Fowler-Nordheim characteristics, transverse beam density, and current stability are discussed.
    Print ISSN: 0003-6951
    Digitale ISSN: 1077-3118
    Thema: Physik
    Publiziert von American Institute of Physics (AIP)
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  • 2
    Digitale Medien
    Digitale Medien
    Vibrational deactivation of N2(v=1) by inelastic collisions with He〈sup LOCATION="PRE"〉3 and He〈sup LOCATION="PRE"〉4: An experimental and a theoretical study (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 107 (1997), S. 2329-2339 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: A new N2–He intermolecular potential with vibrational coordinate dependence is presented. Rate constants for the vibrational deactivation of N2(v=1) by He in the gas phase have been calculated over the temperature range 5–300 K. Accurate values of the rate constants for this process are known down to 100 K. We have now extended these measurements down to 70 K for the deactivation of14N2(v=1) by 4He and down to 50 K for the deactivation of15N2(v=1) by 3He. Agreement between the theoretically calculated and the experimentally determined rate constants is excellent with the calculated values reproducing the experimental measurements within their error bars. An investigation of the low impact energy regime is also presented. While this focuses on collision energies of less than 20 cm−1 and yields rate constants which are in a temperature region inaccessible to our experimental method, it gives further insights into the influence of the attractive well on vibrational energy transfer processes. © 1997 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.475125
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  • 3
    Digitale Medien
    Digitale Medien
    A new He–CO interaction energy surface with vibrational coordinate dependence. II. The vibrational deactivation of CO(v=1) by inelastic collisions with 3He and 4He (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 107 (1997), S. 9929-9934 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: Vibrational relaxation cross-sections and rate constants have been calculated for the deactivation of CO(v=1) by 3He and 4He on a new intermolecular potential with vibrational coordinate dependence [T. G. A. Heijmen, R. Moszynski, P. E. S. Wormer and Ad van der Avoird, J. Chem. Phys. 107, 9921 (1997)]. The new surface is found to resolve the qualitative discrepancy between theory and experiment which existed in earlier theoretical calculations. The low impact energy regime has also been investigated focussing in particular on impact energies of less than 15 cm−1 above the vibrational (v=1) threshold. Resonance structure has been found to occur and a comparison is made with an earlier investigation of the low temperature region. © 1997 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.475295
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  • 4
    Digitale Medien
    Digitale Medien
    Reactively sputtered Ti-Si-N films I. Physical properties (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 656-663 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Films of Ti-Si-N were synthesized by reactively sputtering TiSi2, Ti5Si3, or Ti3Si targets in an Ar/N2 gas mixture. They were characterized in terms of their composition by MeV 4He backscattering spectrometry, their atomic density by thickness measurements combined with backscattering data, their microstructure by x-ray diffraction and high-resolution transmission electron microscopy, and their electrical resistivity by four-point-probe measurements. All films have a metal–to–silicon ratio close to that of their respective targets. The as-deposited films are either entirely amorphous or contain inclusions of TiN-like nanometer-sized grains when the overall atomic composition of the films approaches the TiN phase in the ternary Ti-Si-N diagram. A correlation between the resistivity of the as-deposited films and their position in the ternary phase diagram is evident, indicating that at the atomic scale, the spatial arrangement of atoms in the amorphous phase and their bonding character can approximate those of the equilibrium phases. A mixture of nanocrystalline TiN and amorphous Si-N is proposed for some titanium- and nitrogen-rich films. The atomic density of some films exceeds 1023 at./cm3. The resistivity of the films increases with the Si and the N content. A thermal treatment in vacuum at 700 °C for 1 h decreases the resistivity of the Ti-rich films deposited from the Ti5Si3 or the Ti3Si target, but increases that of the Si-rich films deposited from the TiSi2 target when the nitrogen content exceeds about 30 at. %. The effectiveness of these films as diffusion barriers between Si and Al or Cu is reported in Part II. © 1997 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.364133
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  • 5
    Digitale Medien
    Digitale Medien
    Reactively sputtered Ti-Si-N films. II. Diffusion barriers for Al and Cu metallizations on Si (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 664-671 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Ti-Si-N films synthesized by reactively sputtering a TiSi2, a Ti5Si3, or a Ti3Si target in Ar/N2 gas mixture were tested as diffusion barriers between planar (100) Si substrates and shallow n+p Si diodes, and Al or Cu overlayers. The stability of the Ti-Si-N barriers generally improves with increasing nitrogen concentration in the films, with the drawback of an increase in the film's resistivity. Ti34Si23N43 sputtered from the Ti5Si3 target is the most effective diffusion barrier among all the Ti-Si-N films studied. It works as an excellent barrier between Si and Cu. A film about 100 nm thick, with a resistivity of around 700 μΩ cm, maintains the stability of Si n+p shallow junction diodes with a 400 nm Cu overlayer up to 850 °C for 30 min vacuum annealing. When it is used between Al and Si, the highest temperature of stability achievable with a 100-nm-thick film is 550 °C. A thermal treatment at 600 °C causes a severe intermixing of the layers. The microstructure, atomic density, and electrical resistivity of these films are described in an accompanying Part I. © 1997 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.364206
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  • 6
    Digitale Medien
    Digitale Medien
    Amorphous (Mo, Ta, or W)–Si–N diffusion barriers for Al metallizations (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 1109-1115 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: M–Si–N and M–Si (M=Mo, Ta, or W) thin films, reactively sputtered from M5Si3 and WSi2 targets, are examined as diffusion barriers for aluminum metallizations of silicon. Methods of analysis include electrical tests of shallow-junction diodes, 4He++ backscattering spectrometry, x-ray diffraction, transmission electron microscopy, scanning electron microscopy, and secondary-ion-mass spectrometry. At the proper compositions, the M–Si–N films prevent Al overlayers from electrically degrading shallow-junction diodes after 10 min anneals above the melting point of aluminum. Secondary-ion-mass spectrometry indicates virtually no diffusivity of Al into the M–Si–N films during a 700 °C/10 h treatment. The stability can be partially attributed to a self-sealing 3-nm-thick AlN layer that grows at the M–Si–N/Al interface, as seen by transmission electron microscopy. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.360909
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  • 7
    Digitale Medien
    Digitale Medien
    Vibrational energy transfer between the isotopomers of carbon monoxide at low temperatures (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 108 (1998), S. 485-491 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: Rate constants have been measured for vibration to vibration energy transfer from 12C16O(v=1) to the first vibrationally excited state of both 13C16O (Δν¯=47 cm−1) and 13C18O (Δν¯=100 cm−1) using the infrared laser fluorescence technique over the temperature range 50 to 270 K in the gas phase and in liquid neon, deuterium and argon solutions. Fluorescence from 12C16O(v=1) was filtered out, and the time-dependence of the fluorescence intensity from the other isotopomer used to determine the rate constants for energy transfer. The results for the two isotopomeric systems are markedly different. For that with the smaller energy mismatch, 12C16O–13C16O, the rate constants increase with decrease in temperature from 270 to 80 K. This is shown to be consistent with near-resonant energy transfer mediated by transition dipole-transition dipole couplings. Below 80 K, the temperature dependence of the rate constants flattens. For the 12C16O–13C18O system, the rate constants decrease with decrease in temperature from 270 to 100 K, below which they increase with further decrease in temperature. The temperature dependence in the range 270 to 100 K is shown to be consistent with energy transfer mediated by a combination of by long range and short range forces. Below 100 K, the temperature dependence of the rate constants is governed by attractive forces which influence the collision pair during their encounter. The rate constants are compared with previous studies of near-resonant vibrational energy transfer in other systems at low temperatures. © 1998 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.475411
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  • 8
    Digitale Medien
    Digitale Medien
    The vibrational deactivation of CO(v=1) by inelastic collisions with H2 and D2 (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 106 (1997), S. 4931-4944 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: Calculations of the relaxation rate constants, kCO–H2, for the vibrational deactivation of CO(v=1) by pH2 and oH2 are reported in the temperature range 30 K〈T〈300 K. The CO rotation is treated using the infinite-order sudden (IOS) approximation, while the rotation of H2 is included using the coupled states (CS) approximation. A near-resonant energy transfer process, in which the H2 molecule is rotationally excited from J=2 to J=6 on relaxation of CO(v=1), is found to account for the experimental observation that kCO–pH2/kCO–oH2〉1 for this system at temperatures above 80 K. Evidence is presented to suggest that below this temperature, which represents the current lower limit of existing experimental data for the CO(v=1)-pH2 system, thermal depopulation of the J=2 rotational state in pH2 reduces the importance of the near-resonant energy transfer process in the determination of kCO–pH2. For T(very-much-less-than)80 K the ratio kCO–pH2/kCO–oH2〈1 is predicted on the basis of these calculations. At impact energies less than 60 cm−1, the relaxation cross sections increase at a rate which is insufficient to account for the observed upturn in the experimentally determined deactivation rate constants for the CO–nH2 system below 60 K. Rate constants for the deactivation of CO(v=1) by oD2 and pD2 have also been calculated and compared with experimental data. © 1997 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.473542
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  • 9
    Digitale Medien
    Digitale Medien
    Vibrational energy transfer between isotopes of CO and isotopes of CO2 in the gas phase and in liquid Kr solution (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 1192-1198 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: Rate constants are presented for (VV) energy transfer between CO(ν=1) and CO2(0001) in the gas phase down to 115 K and in liquid Kr solution at 118 and 130 K. Four isotopically substituted systems were investigated for which the energy mismatches varied between 104 and 306 cm−1. The gas and liquid phase data show several systematic effects with changing energy mismatch. In particular it was found that the ratio of the liquid and gas phase rate constants at the same temperature, kL/kG, increased with decreasing energy mismatch. This is not predicted by current theories of liquid phase energy transfer and is in contrast to previous work using liquid Kr as the solvent. © 1995 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.468906
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  • 10
    Digitale Medien
    Digitale Medien
    Vibrational relaxation of CO (v=1) by inelastic collisions with 3He and 4He (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 103 (1995), S. 2528-2537 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: Calculations of the vibrational relaxation rate constants of the CO–3He and CO–4He systems are extended to lower temperatures than in any previous calculation and a comparison made with new experimental results in the temperature range 35–295 K for CO–3He and previously published results in the range 35–2300 K for CO–4He. Both the coupled states (CS) and infinite-order sudden (IOS) approximations are used, with the self-consistent-field configuration interaction CO–He interaction potential of Diercksen and co-workers. The CS approximation is found to give a similar level of agreement with experiment for the two isotopic species, while the performance of the IOS approximation is system dependent. The discrepancy between experimental and theoretical IOS rate constants is quite different for collisions involving 3He and 4He, so that it is not profitable to compare IOS results directly with experiment for these two systems at temperatures below 300 K. The differences between the measured and the CS calculated rate constants for both the CO–4He and CO–3He systems are thought to be due predominantly to inaccuracies in the interaction potential. Relaxation rate constants for CO target molecules in collision with HD, D2 and H2 are compared with results involving 3He, 4He, and "2He,'' revealing some systematic trends depending only on mass. However, for all hydrogen species there are marked upturns in the rate constants at low temperatures relative to those for helium atoms, while the rate constants for HD are greater than those for 3He throughout the temperature range. Calculations at small initial kinetic energies for the CO–He systems reveal an unexpected increase in relaxation cross section with reduction in kinetic energy. This implies that at very low temperatures the CO–He rate constants will show an upturn with decreasing temperature. The fact that this effect is smaller than that for the CO-hydrogen systems and occurs at lower temperatures is consistent with the shallower CO–He attractive well compared with that for CO–H2. © 1995 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.469674
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