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  • 1
    Electronic Resource
    Electronic Resource
    Ion kinetic-energy distributions and Balmer-alpha (Hα) excitation in Ar-H2 radio-frequency discharges (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 746-757 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Excited neutrals and fast ions produced in a 13.56 MHz radio-frequency discharge in a 90% argon −10% hydrogen gas mixture were investigated, respectively, by spatially and temporally resolved optical emission spectroscopy, and by mass-resolved measurements of ion kinetic energy distributions at the grounded electrode. The electrical characteristics of the discharge were also measured and comparisons are made with results obtained for discharges in pure H2 under comparable conditions. Measurements of Balmer-alpha (Hα) emission show Doppler-broadened emission that is due to the excitation of fast atomic hydrogen neutrals formed from ion neutralization processes in the discharge. Temporally and spatially resolved emission profiles of the Hα radiation from the Ar-H2 mixture are presented for the "slow'' component produced predominately by electron-impact dissociative excitation of H2, and for the "fast'' component corresponding to energies much greater than can be derived from dissociative excitation. For the Ar-H2 mixture, the fast component is significantly enhanced relative to the slow component. The measured kinetic-energy distributions and fluxes of predominant ions in the Ar-H2 mixture, such as H3+, H2+, H+, and ArH+, suggest mechanisms for the formation of fast hydrogen atoms. The interpretation of results indicate that H+ and/or H3+, neutralized and backscattered by collision with the powered electrode, are the likely sources of fast hydrogen atoms that produce Doppler-shifted Hα emission in the discharge. There is also evidence at the highest pressures and voltages of "runaway'' H+ ions formed near the powered electrode, and detected with kinetics energies exceeding 100 eV at the grounded electrode. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360333
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  • 2
    Electronic Resource
    Electronic Resource
    Laser desorption time-of-flight mass spectrometry of low-molecular-weight polymers (1986)
    s.l. : American Chemical Society
    Macromolecules 19 (1986), S. 2996-3001 
    Details
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ma00166a021
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  • 3
    Electronic Resource
    Electronic Resource
    Ion fluxes and energies in inductively coupled radio-frequency discharges containing CHF3 (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 5612-5617 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Measurements of ion energy distributions, relative ion intensities, and absolute total ion current densities were made at the grounded electrode of an inductively coupled Gaseous Electronics Conference (GEC) radio-frequency reference cell for discharges generated in CHF3 and its mixtures with argon. In general, the dominant ion species detected were not due to direct ionization of the CHF3 feed gas. Results are presented for plasmas generated with and without a confining quartz annulus that has recently been used to extend the operating parameter range of inductively coupled GEC cells for certain etching gases. Compared to similar plasmas generated without the annulus, the presence of the ring increases the ion flux density by approximately a factor of 2, and increases the mean ion energies. The presence of the ring does not significantly affect the measured relative ion intensities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1319968
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  • 4
    Electronic Resource
    Electronic Resource
    The Gaseous Electronics Conference radio-frequency reference cell: A defined parallel-plate radio-frequency system for experimental and theoretical studies of plasma-processing discharges (1994)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 140-154 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A "reference cell'' for generating radio-frequency (rf) glow discharges in gases at a frequency of 13.56 MHz is described. The reference cell provides an experimental platform for comparing plasma measurements carried out in a common reactor geometry by different experimental groups, thereby enhancing the transfer of knowledge and insight gained in rf discharge studies. The results of performing ostensibly identical measurements on six of these cells in five different laboratories are analyzed and discussed. Measurements were made of plasma voltage and current characteristics for discharges in pure argon at specified values of applied voltages, gas pressures, and gas flow rates. Data are presented on relevant electrical quantities derived from Fourier analysis of the voltage and current wave forms. Amplitudes, phase shifts, self-bias voltages, and power dissipation were measured. Each of the cells was characterized in terms of its measured internal reactive components. Comparing results from different cells provides an indication of the degree of precision needed to define the electrical configuration and operating parameters in order to achieve identical performance at various laboratories. The results show, for example, that the external circuit, including the reactive components of the rf power source, can significantly influence the discharge. Results obtained in reference cells with identical rf power sources demonstrate that considerable progress has been made in developing a phenomenological understanding of the conditions needed to obtain reproducible discharge conditions in independent reference cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1144770
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  • 5
    Electronic Resource
    Electronic Resource
    Ion energy distributions in inductively coupled radio-frequency discharges in argon, nitrogen, oxygen, chlorine, and their mixtures (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 6358-6365 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report ion energy distributions, relative ion intensities, and absolute total ion current densities at the grounded electrode of an inductively coupled Gaseous Electronics Conference radio-frequency reference cell for discharges generated in pure argon, nitrogen, oxygen, and chlorine, and in mixtures of argon with N2, O2, and Cl2. Measured current densities are significantly greater for pure argon and for mixtures containing argon than for pure N2, O2, and Cl2. For all three molecular gases, the ratio of molecular ions to the fragment ions decreases when argon is added to the molecular gas discharges. A possible destruction mechanism for the molecular ions involving metastable argon is discussed. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370138
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  • 6
    Electronic Resource
    Electronic Resource
    Kinetic-energy distributions of ions sampled from argon plasmas in a parallel-plate, radio-frequency reference cell (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 115-125 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Kinetic-energy distributions are presented for ions sampled from 13.56-MHz discharges in argon in a capacitively-coupled, parallel-plate, Gaseous Electronics Conference (GEC) radio-frequency reference cell. The cell was modified to allow sampling of ions through an orifice in the grounded electrode. Kinetic-energy distributions are presented for Ar+, Ar++, Ar+2, ArH+, and several trace ions for plasma pressures ranging from 1.3 Pa, where ion-atom collisions in the plasma sheath are not important, to 33.3 Pa, where collisions are important. Applied peak-to-peak radio-frequency (rf) voltages of 50, 100, and 200 V were used, and the current and voltage waveforms at the powered electrode were measured. Dependences of the ion fluxes, mean energies, and kinetic-energy distributions on gas pressure and applied rf voltage are interpreted in terms of possible ion-collision processes. The results agree with previously measured kinetic-energy distributions of ions sampled from the side of the plasma through a grounded probe for similar discharge conditions, verifying that ion kinetics are characteristic of the plasma sheath independent of where it is formed [J. K. Olthoff, R. J. Van Brunt, and S. B. Radovanov, J. Appl. Phys. 72, 4566 (1992)].
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355898
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  • 7
    Electronic Resource
    Electronic Resource
    Effect of electrode material on measured ion energy distributions in radio-frequency discharges (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 473-475 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Evidence is presented for a significant influence of electrode surface material and condition on the measurement of the kinetic energies of ions sampled from discharges through an orifice in the electrode. Significant differences in ion energy shifts and/or discrimination of low-energy ions are found using aluminum and stainless-steel electrodes in a radio-frequency (rf) discharge cell. It is argued that the observed differences in energy shifts may be attributable in part to differences in charging of oxide layers on the electrode surface around the sampling orifice. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.114540
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  • 8
    Electronic Resource
    Electronic Resource
    Ion kinetic-energy distributions in argon rf glow discharges (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 4566-4574 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Kinetic-energy distributions have been measured for different mass-selected ions sampled from 13.56 MHz rf glow discharges in argon inside a "GEC rf reference cell.'' The electrode geometry of this cell produces an asymmetric discharge and the cell is operated in a pressure regime where ion-molecule collisions in the sheath region of the discharge are significant. Ions are sampled from the side of the plasma perpendicular to the interelectrode axis using an electrostatic energy analyzer coupled to a quadrupole mass spectrometer. Kinetic-energy distributions for Ar+, Ar2+, Ar++, and ArH+ are presented as functions of applied rf voltage, gas pressure, and distance of the mass spectrometer entrance aperture from the edge of the electrodes. The distributions obtained for the sampling orifice placed close enough to the electrodes to allow formation of a sheath in front of the orifice exhibit features similar to those observed previously when sampling ions through the grounded electrode of a parallel-plate reactor. The Ar+ and Ar++ distributions exhibit secondary maxima predicted to result from the formation of low-energy (thermal) ions in the sheath region, such as by charge-exchange and high-energy electron collisions. Kinetic-energy distributions for Ar2+ and ArH+ exhibit no secondary maxima and are peaked at high energies indicative of the sheath potential, and consistent with a formation mechanism involving relatively low-energy collisions in the bulk plasma (glow region).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352110
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  • 9
    Electronic Resource
    Electronic Resource
    Anion states of η4-polyene iron tricarbonyl complexes (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 87 (1987), S. 7001-7006 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Attachment energies of low energy electrons to Fe(CO)5 and to η4 complexes of 1,3-butadiene, 1,3-cyclohexadiene, cyclooctatetraene, and cyclobutadiene with Fe(CO3) have been determined by electron transmission spectroscopy. The spectrum of Fe(CO)5 is similar to that of Cr(CO)6, showing an anion resonance near threshold assigned to predominantly Fe3d orbitals and two resonances between 1 and 3 eV assigned to predominantly COπ* orbitals.The diene complexes show threshold features similar to Fe(CO)5, COπ* resonances around 2 eV, and one or more diene π* resonances. The resonances from the lowest π* orbitals of butadiene, cyclohexadiene, and cyclooctatetraene are little different in the free dienes and the complexes, but higher π* orbitals are substantially destabilized in the complexes, consistent with qualitative symmetry arguments. In the cyclobutadiene complex the π@B|3 orbital of cyclobutadiene is strongly destabilized by interaction with the Fe3d, giving a resonant feature at 1.2 eV. Dissociative attachment of electrons by the iron tricarbonyl complexes has been observed mass spectrometrically. The phenomenon is observed for electrons of energy less than 2 eV and results primarily in the loss of CO. For the cyclobutadiene complex, however, the attachment of 0 eV electrons results in a complex chemical process leading to the ejection of C2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.453397
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  • 10
    Electronic Resource
    Electronic Resource
    Collisional electron detachment and decomposition cross sections for SF−6, SF−5, and F− on SF6 and rare gas targets (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 2254-2260 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Absolute total cross sections for collisional electron detachment and collision-induced dissociation (CID) have been measured for binary collisions of SF−6 and SF−5 with rare gas and SF6 targets for laboratory collision energies ranging from about 10 up to 500 eV. The cross sections for electron detachment of SF−6 are found to be surprisingly small, especially for the SF6 target, for relative collision energies below several tens of electron volts. Specifically, detachment onsets are found to occur at around 30 and 90 eV for the rare gas and SF6 targets, respectively. The CID channel which leads to F− as a product is observed to dominate detachment for relative collision energies below 100 eV. The results for the SF−5 projectile are remarkably similar to those exhibited for SF−6. The role of long-lived excited states in the reactant SF6 ion beam is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457033
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