14067-07-3Relevant articles and documents
Ionization probability of Si+ ion emission from clean Si under Ar+ bombardment
Low,Huan,Wee,Tan
, p. 9427 - 9433 (1997)
The secondary-ion intensity of sputtered Si has been measured as a function of the emission energy using a previously calibrated mass analyser. From the Sigmund-Thompson energy distribution for neutrals, the ionization probability R+ for Si+ ions is inferred. It is found that the behaviour of R+ at high emission energies is consistent with neutralization via the electron tunnelling mechanism (resonant electrons tunnelling from the substrate to the outgoing ions). The possibility of electronic excitations induced by the collision cascade in Sroubek's model is also considered.
Selected ion flow drift tube studies of the reactions of Si+(2P) with HCI, H2O, H2S, and NH3: Reactions which produce atomic hydrogen
Glosik, J.,Zakouril, P.,Lindinger, W.
, p. 6490 - 6497 (1995)
The reaction rate coefficients, k, for the reactions of ground-state Si+(2P) with HCl, H2O, H2S, and NH3, have been measured as a function of reactant ion/reactant neutral center-of-mass kinetic energy, KECM, in a selected ion flow drift tube (SIFDT) apparatus, operated with helium at a temperature 298+/-2 K.The values k of the studied reactions have very pronounced, negative energy dependencies; the rate coefficients decrease by about 1 order of magnitude as KECM increase from near thermal values to ca. 2 eV.The results are interpreted in terms of a simple model assuming the reactions to proceed via the formation of long-lived complexes.These intermediate complexes decompose back to reactants or forward to products, the unimolecular decomposition rate coefficients for these reactions being k1 and k2, respectively.It is found that a power law of the form k-1/k2=const(KECM)m closely describes each reaction.
Ion-enhanced etching of Si(100) with molecular chlorine: Neutral and ionic product yields as a function of ion kinetic energy and molecular chlorine flux
Materer,Goodman, Rory S.,Leone, Stephen R.
, p. 3261 - 3266 (2007/10/03)
Time-of-flight mass spectrometry (TOFMS) is used to measure neutral and ionic silicon etch products evolved during argon ion-enhanced etching of room temperature Si(100) with molecular chlorine. The yields of these neutral and ionic etch products are examined as a function of ion energy, ion flux, and molecular chlorine flux. For the neutral products, an Ar+ ion energy range of 275-975 eV is used, while the ionic product measurements are continued down to 60 eY The atomic Si, SiCl, and SiCl2 neutral etch products are measured without complications due to fragmentation by using 118-nm laser single-photon TOFMS. Atomic Si and SiCl are the major observed etch products. The ionic Si+ and SiCl+ etch products are also measured using TOFMS; however, the SiQ2+ species is not observed. The similarities between neutral and ionic Si and SiCl etch products as a function of various parameters suggest a model based on direct collisional desorption. For the observed neutral SiCl2 product, the absence of SiCl2+ suggests a different mechanism than that for Si and SiCl. For SiCl2, formation models based on thermal heating or reaction and desorption of neutral species at chemically active surface sites, which are ruled out for Si and SiCl, should be considered.
Photoionisation Mass-spectrometric Study of Fragmentation of SiBr4 and GeBr4 in the Range 400-1220 Angstroem
Creasey, Jeremy C.,Lambert, Ian R.,Tuckett, Richard P.,Codling, Keith,Frasinski, Leszek J.,et al.
, p. 3717 - 3724 (2007/10/02)
The non-radiative decay channels of the valence electronic states of SiBr4+ and GeBr4+ have been studied in the range 1220-400 Angstroem (10-31 eV) by photoionisation mass spectrometry.Ion-yield curves for the parent ions and for MBr3+, MBr2+, MBr+, M+ and Br+ (M = Si, Ge) have been obtained, as well as the relative photoionisation branching rations.The appearance thresholds for SiBr3+ and GeBr3+ occur at 11.31 and 10.97 eV, respectively.They lie within the Franck-Condon region of the ground state of SiBr4+ and GeBr4+, and are at the thermodynamic thresholds for SiBr3+ + Br and GeBr3+ + Br.The smaller fragment ions have appearance thresholds which relate to energies for excited electronic states of SiBr4+ and GeBr4+, and not to the lower-lying thermodynamic energy of the fragment ion.The results are discussed with reference to our earlier work on radiative decay from excited states of SiBr4+ and GeBr4+ (J.Chem.Soc.Faraday Trans., 1990, 86, 2021).We have obtained a new value for the ionisation potential of SiBr3 of 7.6 +/- 0.4 eV, and we suggest that the previously accepted value for SiBr2 (12 +/- 1 eV) is ca. 3.5 eV too high.
Reactions of Ar+, Ne+, and He+ with SiF4 from thermal energy to 50 eV c.m.
Weber, M. E.,Armentrout, P. B.
, p. 2213 - 2224 (2007/10/02)
Guided ion-beam techniques are used to measure the cross sections for reaction of SiF4 with Ar+, Ne+, and He+ from thermal to 50 eV.Charge transfer followed by loss of F atoms are the sole processes observed.All SiFx+
Energetics and dynamics in the reaction of Si+ with SiF4. Thermochemistry of SiFx and SiF+x (x=1, 2, 3)
Weber, M. E.,Armentrout, P. B.
, p. 6898 - 6910 (2007/10/02)
The title reaction is studied using guided ion beam mass spectrometry.Absolute reaction cross sections are measured as a function of kinetic energy from thermal to 40 eV, and three endothermic product channels are observed.The dominant SiF+ + SiF3 channel is only slightly endothermic, while the SiF3+ + SiF and SiF2+ + SiF2+ channels have much higher thresholds.The SiF3+ cross section magnitude is about half that of SiF+, while the SiF2+ cross section is an order of magnitude smaller than that of SiF+.A second feature which appears in the SiF2+ cross section is due to dissociation of SiF3+ .There is evidence that SiF+ and SiF3+ are produced via a direct mechanism.Competition between these two channels is interpreted in terms of molecular orbital correlations and qualitative potential energy surfaces.One surface is found to correlate only with the SiF3+ + SiF channel, while another correlates diabatically with this channel and adiabatically with the SiF+ + SiF3 channel.Competition on this latter surface has an energy dependence which is consistent with the Landau-Zener model.Reaction thresholds are analyzed to yield 298 K heats of formation for SiFx and SiFx+ species.From an evaluation of these and literature values, we recommend the following values:.
Electron-impact ionization cross sections of the SiF3 free radical
Hayes, Todd R.,Shul, Randy J.,Baiocchi, Frank A.,Wetzel, Robert C.,Freund, Robert S.
, p. 4035 - 4041 (2007/10/02)
Absolute cross sections for electron-impact ionization of the SiF3 free radical from threshold to 200 eV are presented for formation of the parent SiF3 ion and the fragment SiF2 , SiF+, and Si+ ions.A 3 keV beam of SiF3 is prepared by near-resonant charge transfer of SiF3 with 1,3,5-trimethylbenzene.The beam contains only ground electronic state neutral radicals, but with as much as 1.5 eV of vibrational energy.The absolute cross section for formation of the parent ion at 70 eV is 0.67 +/- 0.09 Angstroem2.At 70 eV the formation of SiFi2+ is the major process, having a cross section 2.51 +/- 0.02 times larger than that of the parent ion, while the SiF+ fragment has a cross section 1.47 +/- 0.08 times larger than the parent.Threshold measurements show that ion pair dissociation processes make a significant contribution to the formation of positively charged fragment ions.
Electron impact ionization cross sections of SiF2
Shul, Randy J.,Hayes, Todd R.,Wetzel, Robert C.,Baiocchi, Frank A.,Freund, Robert S.
, p. 4042 - 4047 (2007/10/02)
Absolute cross sections are measured for electron impact ionization and dissociative ionization of SiF2 from threshold to 200 eV.A fast (3 keV) neutral beam of SiFz is formed by charge transfer neutralization of SiF2+ with Xe; it is primarily in the ground electronic state with about 10percent in the metastable first excited electronic state (3B1).The absolute cross section for ionization of the ground state by 70 eV electrons to the parent SiF2+ is 1.38 +/- 0.18 Angstroem2.Formation of SiF+ is the major process with a cross section at 70 eV of 2.32 +/- 0.30 Angstroem2.The cross section at 70 eV for formation of the Si fragment ion is 0.48 +/- 0.08 Angstroem2.Ion pair production contributes a significant fraction of the positively charged fragment ions.
