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  • 1
    Electronic Resource
    Electronic Resource
    Collision-induced dissociation of Fe+n (n=2–10) with Xe: Ionic and neutral iron binding energies (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 5466-5485 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Cross sections for collision-induced dissociation (CID) of Fe+n with Xe, 2≤n≤10, are presented. Experiments were performed on a newly constructed guided ion beam mass spectrometer, the design and capabilities of which are described in detail. The single mechanism for dissociation of iron cluster ions is sequential loss of iron atoms with increasing collision energies. There is no evidence for fission to molecular neutral products. The cross section threshold energy dependences are analyzed to give the bond dissociation energies (BDEs), D0(Fe+n−1–Fe). Data analysis employs an empirical model that incorporates RRKM theory to account for inefficient dissociation on the time scale of the experiment. Results show that Fe+6 has the strongest BDE, D0(Fe+5–Fe) =3.44±0.18 eV, while Fe+3 is the most weakly bound, D0(Fe+2–Fe) =1.64±0.15 eV. Neutral cluster BDEs are derived from ionic binding energies and known ionization potentials. Branching ratios and other cross section features are also discussed with respect to cluster size.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456452
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  • 2
    Electronic Resource
    Electronic Resource
    Reactions of fourth-period metal ions (Ca+−Zn+) with O2: Metal-oxide ion bond energies (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 2676-2691 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Reactions of Ca+, Zn+ and all first-row atomic transition metal ions with O2 are studied using guided ion beam techniques. While reactions of the ground states of Sc+, Ti+, and V+ are exothermic, the remaining metal ions react with O2 in endothermic processes. Analyses of these endothermic reactions provide new determinations of the M+–O bond energies for these eight elements. Source conditions are varied such that the contributions of excited states of the metal ions can be explicitly considered for Mn+, Co+, Ni+, and Cu+. Results (in eV) at 0 K are D0(Ca+–O)= 3.57±0.05, D0(Cr+–O)=3.72±0.12, D0(Mn+–O)=2.95±0.13, D0(Fe+–O)=3.53±0.06 (reported previously), D0(Co+–O)=3.32±0.06, D0(Ni+–O) =2.74±0.07, D0(Cu+–O)=1.62±0.15, and D0(Zn+–O)=1.65±0.12. These values along with literature data for neutral metal oxide bond energies and ionization energies are critically evaluated. Periodic trends in the ionic metal oxide bond energies are compared with those of the neutral metal oxides and those of other related molecules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458906
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  • 3
    Electronic Resource
    Electronic Resource
    Oxidation reactions at variably sized transition metal centers: Fe+n and Nb+n +O2 (n=1–3) (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 6148-6163 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Cross sections for the reactions of Fe+n and Nb+n (n=1–3) with O2 are measured as a function of kinetic energy over a range of 0 to 〉10 eV. In all systems, analysis yields insight into the kinetics and thermochemistry of the oxidation processes. Nb+n reaction with O2 exothermically near the Langevin–Gioumousis–Stevenson close-collision limit, driven by formation of strong NbO+ and NbO bonds. Fe+n are less reactive, although oxidation becomes progressively more facile as the size of the reactant increases from Fe+ to Fe+3. In contrast to the Nb+n systems, Fe+n (n=2,3) react at elevated energies by simple cluster fragmentation processes. Quantitative limits are established for ionic and neutral cluster oxide bond dissociation energies. Cross sections for formation of MnO+ from reaction of M+n (Fe+3, Nb+2, and Nb+3) are observed to have both an exothermic and an endothermic feature. Since there is only one chemical pathway to form this product, it is suggested that there are activation barriers to formation of favorable reaction intermediates. A similar suggestion is required to explain product branching ratios involving metal dioxides which run counter to thermodynamic predictions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457434
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  • 4
    Electronic Resource
    Electronic Resource
    Collision-induced dissociation processes of Nb+4 and Fe+4: Fission vs evaporation (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 610-611 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Collision-induced dissociation (CID) of Nb+4 and Fe+4 with Xe has been studied over an energy range of 0–20 eV with a new instrument designed to study cold cluster ions. The energy dependences of the cross sections are presented. It is found that the lowest energy pathway for Nb+4 CID is fragmentation into molecular ions, or fission. Analysis of this process yields D0(Nb+2–Nb2)=4.3±0.3 eV. Fe+4, on the other hand, fragments only by sequential loss of Fe. Analysis of the lowest energy process gives D0(Fe+3–Fe)=1.8±0.2 eV. No evidence for molecular Fen fragments is observed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455455
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  • 5
    Electronic Resource
    Electronic Resource
    Homoepitaxial growth and hydrogen incorporation on the chemical vapor deposited (111) diamond (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 1306-1310 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A systematic study of the effect of growth conditions (temperature, microwave power, and pressure) on the hydrogen incorporation and growth rate of (111) homoepitaxial diamond synthesized by microwave plasma assisted chemical vapor deposition is carried out by secondary ion mass spectrometry. Significant quantities of hydrogen incorporation in the (111) homoepitaxial diamond are detected for the growth conditions employed. Hydrogen concentration and growth rate are found to increase with an increase in the substrate temperatures. The increase of microwave power decreases the hydrogen incorporation and increases the growth rate. The effect of pressure rise is similar to that of microwave power. However, the effect of pressure rise over 50 Torr on hydrogen incorporation and growth rate is small. The decrease of hydrogen incorporation can be explained by the suppression of defects in the growing film by atomic hydrogen in the gas phase. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370886
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  • 6
    Electronic Resource
    Electronic Resource
    Direct kinetic studies of SiH3+SiH3, H, CCl4, SiD4, Si2H6, and C3H6 by tunable infrared diode laser spectroscopy (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 4914-4926 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Gas phase reactions of silyl radical, SiH3, are investigated at room temperature using tunable diode laser flash kinetic spectroscopy. Photolytic generation of silyl at 193 and 248 nm is demonstrated using several different precursor systems. The silyl recombination reaction, SiH3+SiH3→Si2H6, is studied by quantitative measurement of SiH3 and attendant product densities. Analysis yields a refinement of the rate constant, krc=(7.9±2.9)×10−11 cm3 molecule−1 s−1. By modeling silyl densities following photolysis of HCl in SiH4, bimolecular rate constants for H+SiH3 and H+SiH4 are determined to be (2±1)×10−11 and (2.5±0.5)×10−13 cm3 molecule−1 s−1, respectively. Reactions of SiH3 with SiD4, Si2H6, CCl4, and C3H6 (propylene) are studied under pseudo-first-order conditions. Derived upper limits to the rate constants show these reactions to be slow at room temperature. The data demonstrate the reactivity of silyl with open-shell (radical) species and the general inertness of silyl toward closed shell molecules. Under typical chemical vapor deposition conditions, SiH3 is, therefore, a kinetically long-lived species in the gas phase and consequently a potentially important film forming species under plasma and photochemical deposition conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461707
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  • 7
    Electronic Resource
    Electronic Resource
    The subgrid-scale estimation model in the physical space representation (1999)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 11 (1999), S. 2330-2342 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The subgrid-scale estimation procedure for large eddy simulations developed previously in the spectral (Fourier) representation is extended to the physical space representation. The procedure provides an estimate of the unfiltered velocity field appearing in the definition of the subgridscale stress tensor and consists of two steps. In the deconvolution step an approximate inversion of the filtering operation is performed. Subsequently, the nonlinear step is used to generate a range of subgrid scales on a mesh two times smaller than the mesh employed for a discretization of the resolved quantities. The modeling procedure is evaluated by comparing results of large eddy simulations of turbulent channel flow with the corresponding results of direct numerical simulations, experiments, and other large eddy simulations. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.870095
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  • 8
    Electronic Resource
    Electronic Resource
    The subgrid-scale estimation model on nonuniform grids (1999)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 11 (1999), S. 3786-3792 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The subgrid-scale estimation procedure developed previously using one-dimensional top hat filters on uniform grids is generalized to nonuniform grids. The method is evaluated in large eddy simulations of turbulent channel flow performed on a grid which is non-uniform in the wall-normal direction. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.870239
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  • 9
    Electronic Resource
    Electronic Resource
    Evolution of quasi-breakdown in thin gate oxides (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 5302-5306 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The mechanism for quasi-breakdown (QB) in thin gate oxides was studied using bipolar current stress and unipolar constant current stress. Continual bipolar current stressing on the gate oxide shows two distinct stages of QB—recoverable and unrecoverable QB. During the recoverable QB stage, the gate leakage current recovers to the stress-induced leakage current level upon application of a proper reverse bias. In contrast, no electrical recovery is observed within the unrecoverable QB stage. This stage is characterized by a higher gate leakage current than that of the recoverable QB stage and a very stable gate voltage during stressing. Carrier separation measurements further demonstrate that two different modes of conduction can occur during the recoverable QB stage. In the early stage, Fowler–Nordheim electron tunneling dominates the conduction mechanism although a small hole current is observed. With prolonged electrical stress, the hole direct tunneling current becomes dominant. Based on the aforementioned observations and the monitoring of the generation of oxide traps using the direct-current current–voltage technique, a QB model of positive hole trapping at the anode is proposed. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1464648
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  • 10
    Electronic Resource
    Electronic Resource
    Effects of hydrogen and rf power on the structural and electrical properties of rf sputtered hydrogenated amorphous silicon carbide films (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 1611-1616 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effects of the rf power (100 to 600 W) and the hydrogen partial pressure (PH=0.15 to 0.6 Pa.) on the deposition rate and the structural and electrical properties of rf sputtered hydrogenated amorphous silicon carbide (a-Si1−xCx:H) films were investigated. The films were deposited in an argon plus hydrogen ambient. The deposition rate increased with increasing rf power, but decreased with increasing PH. The refractive index increases from 1.85–3.6 as the rf power increases from 100–600 W and from 2.8 to 3.5 as PH increases from 0.15–0.6 Pa. The optical gap increases from 1.5 to 2.15 eV as PH increases from 0.15–0.6 Pa, but decreases from 2.8–1.38 eV as the rf power increases from 100–600 W. The Si–C bond gave the most prominent absorption peak in the infrared spectra, and increased with increasing rf power but not affected by changes in PH. The Si–H bonds increases from 3.06×1021 to 1.64×1022 cm−3 as PH was increased from 0.15–0.6 Pa. The optical gap increases from 1.5–2.15 eV and the conductivity reduces from 7.3×10−9 to 1.9×10−11 Ω−1 cm−1 accordingly. No C–Hn stretching mode was detected in all the films and this was attributed to the low carbon content of the films. We conclude that rf sputtering technique is not effective in varying the carbon content in a-Si1−xCx:H films. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362959
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