摘要:

AbstractA review is presented on the contemporary modelling efforts describing the coupled electronic and heavy particle excited state kinetics in glow discharges in gas mixtures. The dramatic effects of the heterogeneous collisional interactions between the electronic/vibronic states of the gas mixture constituents on the dissociation, ionization, gas heating, discharge impedance and power loading are described and discussed. A template construct of a collisional model of molecular gas mixtures where the electron kinetics are obtained from the collisional Boltzmann transport equation, and the vibrational kinetics are governed by a system of vibrational master equations, is described in detail. Three test cases are discussed: (i) Ar − Cl2, (ii) N2− O2, and (iii) N2− H2. The generic guidelines that are derived from the analysis of the above mixtures are that: (a) There is a strong coupling between the dissociation and the ionization balances in gas mixtures. It is cautioned that for most conditions, even in pure molecular gases, neither channel can be studied independently of the other. (b) In molecular gas mixtures, the heterogeneous collisional interactions between the metastable excited electronic states play important roles in determining the discharge characteristics. (c) The calculations assuming constantE/Nand constant electron density in gas mixtures can lead to inconsistent and misleading conclusions on the throughput of these disch

ISSN:0863-1042    

DOI:10.1002/ctpp.2150350403

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractSeveral aspects of negative ions in low pressure discharges are treated. The elementary processes, in which negative ions are produced and destroyed, are summarized. The influence of negative ions on plasma operation is analyzed in terms of transport equations. It is shown that diffusion, electric field, power input, plasma stability and plasma boundary layer are strongly affected by the presence of negative ions. Finally, an overview is given of experimental techniques for the detection of negative ions. Some typical results in low pressure discharges are presented.

ISSN:0863-1042    

DOI:10.1002/ctpp.2150350404

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractA highly sensitive multi‐element optical absorption technique is used to measure the absolute column density of both CH3and CH radicals in a dc hollow cathode plasma‐assisted chemical vapor deposition (CVD) system with CH4and H2used as the input gases. The plasma gas temperature is determined at different spatial points using the H2emission spectrum near 460 nm. The spatial maps of the temperature and the radical densities provide information on the chemical processes taking place in the discharge. The CH3and CH radical density measurements made in the dc discharge system are compared with similar measurements made in a hot filament CVD system. The [H]/[H2] ratio is derived from the CH3and CH densities using an analysis based on partial thermodynamic equilibrium of the single carbon hydrocarbon abstraction reacti

ISSN:0863-1042    

DOI:10.1002/ctpp.2150350405

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractMeasurements of the total and selected partial cross sections for the electron impact ionization of cyclopentadienyltrimethylplatinium (C5H5)Pt(CH3)3[CpPtMe3], bismethylcyclopentadienylruthenium (CH3C5H4)2Ru [(MeCp)2Ru], and bismethylcyclopentadienylferrum (CH3C5H4)2Fe [(MeCp)2Fe] in the energy range from threshold up to 90 eV are presented. A double focussing mass spectrometer with an improved ion extraction system to avoid the discrimination of fragment ions with excess energy was used. The following values for the total single ionization cross sections σ at an impact energy of 70 eV and for the ionization energies (EI) were determined: σ = (13.7 ± 2.5) 10−16cm2,EI= 7.6 ± 0.5 eV [CpPtMe3], σ = (23.2 ± 4.2) × 10−16cm2,EI= 7.5 ± 0.5 eV [(MeCp)2Ru], σ = (20.2 ± 3.6) × 10−16cm2,EI= 8.1 ± 0.5 eV [(MeCp)2Fe]. The results are compared with known mass spectra of the Pt‐ and Fe‐compound. Schemes for the fragmentation and ion formation processes in the ion source are discussed. The fragment ion composition as a function of the ion source temperature was investigated. The production rate of pure metal ions is small. The measured total single ionization cross sections when compared with calculations using two additivity rules were found to be lower than

ISSN:0863-1042    

DOI:10.1002/ctpp.2150350406

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractPartial ionization cross sections for silane and disilane by electron impact have been measured for electron energies in the range of threshold to 1000 eV using a crossed beam geometry and employing a pulsed electron beam and a pulsed ion extraction technique. The cross sections were normalized by using the relative flow technique. For ease of use in various plasma modeling we have fitted the cross sections to an empirical formula.

ISSN:0863-1042    

DOI:10.1002/ctpp.2150350407

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractThe energy dependence of the partial cross sections of electron‐impact dissociation of SF6into the neutral radicals SF, SF2and SF3is measured from the threshold to 200 eV. This measurement is accomplished by appearance mass spectrometry in a dual electron beam device. The dissociation products SF4and SF5are below the detection limit of the present system. The threshold energies for neutral dissociation into SF3, SF2and SF are measured to be 16.0, 19.5 and 22.0 eV respectively. The surface loss probability of each radical and the electron‐impact nitrogen dissociation are examined to evaluate the relative dissociation cross section. However, the absolute cross section cannot be assigned for lack of the ionization cross sections for the SFxradic

ISSN:0863-1042    

DOI:10.1002/ctpp.2150350408

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractThe electron‐impact energy dependence of the dissociation cross sections of CF4and CHF3into the CFx(x = 1 − 3) free radicals was previously reported, in which the absolute values of the cross sections were tentatively estimated based on certain assumptions for the unknown ionization cross sections of the CF2and CF radicals. These assumptions are no longer needed, since a complete set of absolute parent and dissociative ionization cross sections of CFxradicals has been reported recently by Becker and co‐workers. Based on these data, the absolute cross sections for the electron‐impact neutral dissociation of CF4and CHF3into CF3, CF2and CF from the threshold up to 200–300 eV have now been accurately calibrated. Adjustments to the previously reported absolute cross sections of up to a factor of 16 were

ISSN:0863-1042    

DOI:10.1002/ctpp.2150350409

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractThe semi‐empirical Deutsch‐Märk (DM) formalism for the calculation of absolute cross sections for the single ionization of atoms has been extended to the calculation of cross sections for the double and triple ionization of ground state atoms. Detailed comparisons are made with available experimental data from threshold to 200 eV. In general, we find good agreement between the present calculations and the available experimental data. On that basis, we feel confident that the present formalism can be applied to predict double and triple ionization cross sections for those atoms, for which no experimental data are currently available, with an accuracy in the 30–50% range for impact energies where direct ionization processes dominate and where contributions from tightly bound inner shells can be neglected. This level of precision should be sufficient for modelling purposes and many other practical applic

ISSN:0863-1042    

DOI:10.1002/ctpp.2150350410

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractOberservation of enhanced electron attachment to ArF‐excimer‐laser irradiated methane is reported. Preliminary evidence is presented that laser‐excited superexcited states of CH4(or other excited states to which these convert) are responsible for the observed enhanced electron attachment, and, that predominantly H−ions are produced via this process. The possible significance of this process for plasma processing discharges using CH4and its mixtures is in

ISSN:0863-1042    

DOI:10.1002/ctpp.2150350411

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractWe report the first case where it is possible to clearly identify and quantitatively characterize the dominant physical processes contributing to production of the optogalvanic effect (OGE) signal in a discharge plasma. This work concentrates on the simplest case where only two states are involved in the optical transition. The theoretical model with only four parameters is in excellent agreement with the experimentally obtained time‐resolved OGE waveforms. The collisional ionization rate in the upper state is twice as fast as that in the lower state although the two states are only separated by 1.94 eV. We conclude that the optogalvanic effect of the neon 640.22 nm transition is due primarily to the electron collisional ionization of the neon atoms. An alternative interpretation for the lengthening of the final state lifetime is also included (see Appendix

ISSN:0863-1042    

DOI:10.1002/ctpp.2150350412

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY