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1.
In this work, a fluid model has been applied to study HBr/Ar capacitively coupled plasma discharges that are being used for anisotropic etching process. Based on time average reaction rates, the model identify the most dominant species in HBr/Ar plasma. Our simulation results show that the neutral species like H and Br, which are the key precursors in chemical etching, have bell shape distribution while ions like HBr+, Br+ and Ar+ which plays a dominant role in the physical etching, have double humped distribution and shows peaks near electrodes. The effect of HBr/Ar mixing ratios on densities of dominant species are analyzed. The addition of Ar to HBr plasma decreases H, Br and HBr+ densities slightly while increases Br+ and Ar+ densities. It was found that the dilution of HBr by Ar results in an increase in electron density and electron temperature, which results in more ionization and dissociation. The densities and hence the fluxes of the neutrals and positive ions for etching and subsequently chemical etching versus physical etching in HBr/Ar plasmas discharge can be controlled by tuning Ar concentration in the discharge and the desire etching can be achieved. 相似文献
2.
A. J. Yencha M. -W. Ruf H. Hotop 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1991,21(2):113-130
An electron spectrometric study has been performed on HBr using metastable helium and neon atoms as well as helium resonance photons. High resolution electron spectra were obtained for a mixed He(21 S, 23 S) beam, a pure He(23 S) beam, a mixed Ne(3s 3 P 2,3 P 0) beam, and for HeI VUV light. From the comparison of vibrational populations of HBr+ (X, v′) and HBr+ (A, v′), formed by either He* and Ne* Penning ionization (PI) or HeI photoionization, we conclude that HBr+ (X) formation by PI exhibits only little perturbation of HBr potentials, whereas HBr+ (A) formation by PI exhibits substantial bond stretching of HBr due to metastable atom attack preferably from the H end. For He(21 S) + HBr theX- andA-state vibrational peak shapes are substantially broader than for the He(23 S) + HBr case pointing to an additional, charge exchanged interaction (He+ + HBr?) in the entrance channel of the former system which is also responsible for a broad feature found at lower electron energies in the He(21 S, 23 S) induced PI electron spectra. For the first time, we have detected the low energy electrons in both the He(21 S) + HBr and He(23 S) + HBr spectra, associated with the major mechanism for the formation of Br+ ions: energy transfer to repulsive HBr** Rydberg states, dissociating to H(1s) and autoionizing Br** atoms. The HBr+ (X)2 II 3/2:2 II 1/2 fine structure branching ratios vary significantly with the ionizing agent in a similar way as for the isoelectronic, atomic target case krypton. 相似文献
3.
A. E. Belikov M. A. Smith 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2008,82(5):789-800
The mechanisms and kinetics of low-temperature ion-molecular reactions between the Br+, HBr+, and DBr+ions and the HBr, DBr, H2, and D2 molecules were studied. The HBr+ (i,v +) and DBr+(i,v +) ions were prepared in separate spin-orbit (i) and vibrational (v +) states by resonance multiphoton ionization in a free flow of halogen halides (HBr and/or DBr) with hydrogen, deuterium, or inert gases (Ar, He). The effectiveness of various reaction channels, including the exchange of charges, H and D atoms, and H+andD+ ions, was studied. The quantitative data on the kinetics of these reactions were obtained for separate quantum states of the ions. The resonance ionization of one of the two ion isotopomers H79Br+(D79Br+) or H81Br+(D81Br+) was used to study and compare the effectiveness of various ion-molecular reaction channels. 相似文献
4.
《Chemical physics》1987,115(1):109-117
An extended electron modulation spectroscopy method is described which allows the accurate determination of photoionisation cross sections of transient species relative to those of precursor compounds. In this paper cross section at 584 Å for atomic and molecular bromine transitions from neutral ground to lowest ionic states have been measured relative to that of the HBr+ (X2Π1/2,3/2)←HBr(X1Σ+) ionisation. Using the cross section of this HBr transition as an absolute standard and with relative cross-section data for ionisations leading to the accessible excited ionic states of Br+ and Br+2, absolute total angle-integrated cross sections for the valence shell ionisation process in Br+ and Br+2 are presented. 相似文献
5.
Previously reported shock tube studies of the dissociation of HBr in the temperature range of 2100–4200°K have been extended to lower temperatures (1450–2300°K) in pure HBr. The course of reaction was followed by monitoring the radiative recombination emission in the visible spectrum from Br atoms. The results imply that, in the lower range of temperatures, the activation energy of dissociation, E in the expression AT?2e?E/RT, can be approximated by the HBr bond energy (88 kcal/mole). It was also found that, in this temperature range, the rate of HBr dissociation is sensitive to the Br2 dissociation rate and the HBr + Br exchange rate. When these rates were adjusted to bring computed reaction profiles into agreement with experimental ones, it was found that the higher-temperature data could also be fitted reasonably well with an HBr dissociation activation energy of 88 kcal/mole, contrary to the conclusions of our previous work, which favored an activation energy of 50 kcal/mole. The “best value” for k1Ar, the rate coefficient for HBr dissociation in the presence of Ar as chaperone, appears to be 1021.78 ± 0.3 T?2 10?88/θ cc/mole sec, where θ = 2.3 RT/1000; that for k1HBr, is 1022.66T?210?88/θ. A detailed review is given of the rate coefficients for the other pertinent reactions in the H2–Br2 system, viz., Br2 dissociation and reactions of HBr with H and Br. 相似文献
6.
The relative importance of the rearrangement ions [M ? Br ? CO]+, [M ? Br2 ? CO]+ and [M ? HBr2 ? CO]+ in the mass spectra of the title compounds is compared with the amounts of α-methoxyketone formed on reduction of these compounds with a Zn/Cu couple in methanol. It is suggested that the quantitative correlation found reflects the electron releasing powers of the substituents on the α carbons. 相似文献
7.
Formation of Organosilicon Compounds. 66. (H2Si? CH2)2 and Si-substituted Derivatives (H2Si? CH2)2 1 is formed in the reaction of (Cl2Si? CH2)2 with LiAlH4. In 1 , the halogenation of the SiH bond is so much preferred compared to the ring cleavage reaction, that 1 reacts with Cl2 or Br2 to form successively all compounds form 1-monochlor-1,3-disilacyclobutane to (X2Si? CH2)2 (X = Cl, Br). The stability of the 1,3-disilacyclobutane skeleton towards HBr or Br2 increases as the electronegativity of the Si-substituents increases. Thus, (Cl2Si? CH2)2 is cleaved neither by HBr nor by Br2, whereas e. g. [H(C6H5)Si? CH2]2 reacts to [Br(C6H5)Si? CH2]2 with Br2, but yields meH(C6H5)Si? CH2? SiBr(C6H5)H (me = CH3) with HBr. In [me(C6H5)Si? CH2]2, the four-membered ring is cleaved by Br2 as well as by HBr. The 1H-, 29Si- and 13C-n.m.r. data are reported. 相似文献
8.
9.
Phosphonium Salts with Hydrogen Dihalide Anions HCl2?, HBr2?, HI2?, or HBrCl? Phosphonium hydrogen dihalides [R3PR′][XHY] (X = Y = Cl, Br, I; X = Br, Y = Cl) resp. [R3PH]HBr2 are obtained as extremely hydrolyzable crystals by reaction of phosphonium halides or tertiary phosphanes with hydrogen halide. According to IR spectroscopic results the solid compounds mostly contain anions [XHX]? with symmetric hydrogen bonds. In solution 1H NMR measurements show a slight (X = Cl, Br) or considerable (X = I) dissociation according to HX2? ? X? + HX. On heating the solid compounds decompose with formation of hydrogen halide and [R3PR′]X or [R3PH]X. In this process the hydrogen bromidechlorides [R3PR′][BrHCl] exclusively eliminate HCl. NMR studies (1H und 31P) with solutions containing [R3PH]HBr2 (R = phenyl, 1-naphtyl) or HBr and Ph3P in varying molar ratios show that a fast proton exchange between the competing Lewis bases R3P and Br? exists. 相似文献
10.
Absolute dipole oscillator strengths (cross section) have been obtained for valence shell photoabsorption (7–100eV) and a variety of partial photoionization (11–40 eV) processes in gaseous HBr. Partial dipole oscillator strengths are reported for the formation of the X2Π, A2Σ+ and B2Σ electronic state of HBr+ as well as the respective photoelectron branching ratios. The photoelectron binding energy spectra show clear evidence of many-body effects in photoionization to the B2Σ state of HBr+ with the ionization oscillator strength divided over many bands as predicted by many-body Green's function calculations. Partial dipole oscillator strengths are also reported for molecular ion formation as well as for all dissociative ionization processes. The measurements have been made by the dipole (e,e) (e,2e) and (e,e + ion) methods, which respectively provide quantitative measurements of photoabsorption, photoelectron spectroscopy and photoionization mass spectrometry at continuously tuneable energies. The measurements of dipole oscillator strengths for production of electronic states of HBr+ are combined with those for molecular and dissociative photoionization. These, considered together with the ionization and appearance potentials, provide a quantitative dipole breakdown picture for the ionic photofragmentation pathways of HBr in the energy region up to 40 eV. 相似文献
11.
Ab initio MO calculations were applied to the evaluation of repulsion energies in highly charged HBr ions. Net charges of H and Br atoms were obtained from the Mulliken atomic population, and repulsion energies were estimated by a simplified model based on the Coulomb repulsion. The repulsion energy of HBr8+ was calculated to be 71.5 eV. 相似文献
12.
Reactions of CF3Br with H atoms and OH radicals have been studied at room temperature at 1–2 torr pressures in a discharge flow reactor coupled to an EPR spectrometer. The rate constant of the reaction H + CF3Br → CF3 + HBr (1) was found to be k1 = (3.27 ± 0.34) × 10?14 cm3/molec·sec. For the reaction of OH with CF3Br (8) an upper limit of 1 × 10?15 cm3/molec·sec was determined for k8. When H atoms were in excess compared to NO2, used to produce OH radicals, a noticeable reactivity of OH was observed as a result of the reaction OH + HBr → H2O + Br, HBr being produced from reaction (1). 相似文献
13.
Hydrogen bromide is known to inhibit the bromination of aromatic substrates (ArH), either by fixing up bromine as HBr3 or ArH as ArH · HBr. However, there is catalysis by HBr in the bromination of mesitylene in acetic acid. The bromination of o-xylene in acetic acid in the dark is found to be autocatalytic, and the reaction is overall third order, first order in o-xylene with the orders in Br2 and HBr depending on the concentrations. A composite rate expression involving Br2 and HBr as electrophiles has been proposed and verified using iodine bromide as a catalyst where the orders are one in each of the reactants, irrespective of the concentrations used. 相似文献
14.
The mechanism of reaction Cl2+2HBr=2HCl+Br2 has been carefully investigated with density functional theory (DFT) at B3LYP/6-311G** level. A series of three-centred and four-centred transition states have been obtained. The activation energy (138.96 and 147.24 kJ/mol, respectively) of two bimolecular elementary reactions Cl2+HBr→HCl+BrCl and BrCl+HBr→HCl+Br2 is smaller than the dissociation energy of Cl2, HBr and BrCl, indicating that it is favorable for the title reaction occurring in the bimolecular form. The reaction has been applied to the chemical engineering process of recycling Br2 from HBr. Gaseous Cl2 directly reacts with HBr gas, which produces gaseous mixtures containing Br2, and liquid Br2 and HCl are obtained by cooling the mixtures and further separated by absorption with CCl4. The recovery percentage of Br2 is more than 96%, and the Cl2 remaining in liquid Br2 is less than 3.0%. The paper provides a good example of solving the difficult problem in chemical engineering with basic theory. 相似文献
15.
Junmyung Lee Alexander Efremov Byung Jun Lee Kwang-Ho Kwon 《Plasma Chemistry and Plasma Processing》2016,36(6):1571-1588
The comparative study of etching characteristics and mechanisms for TiO2 thin films in CF4 + Ar, Cl2 + Ar and HBr + Ar inductively coupled plasmas was carried out. The etching rates for TiO2, Si and photoresist were measured as functions of gas mixing ratios at fixed gas pressure (10 mTorr), input power (800 W) and bias power (300 W). It was found that the maximum TiO2 etching rate of ~130 nm/min correspond to pure CF4 plasma while an increase in Ar fraction in a feed gas results in the monotonic non-linear decrease in the TiO2 etching rates in all three gas mixtures. Plasma diagnostics by Langmuir probes and 0-dimensional (global) plasma modeling supplied the data on the densities of plasma actives specie as well as on particle and energy fluxes to the etched surface. It was concluded that, under the given set of experimental conditions, the TiO2 etching kinetics in all gas systems correspond to the ion-assisted chemical reaction with a domination of the chemical etching pathway. It was found also that the differences in the absolute TiO2 etching rates correlate with the energy thresholds for TiO2 + F, Cl or Br reaction, and the reaction probabilities for F, Cl and Br atoms exhibit the different changes with the ion energy flux according to the volatility of corresponding etching products. 相似文献
16.
J. Respondek H. Schwarz F. Van Gaever C. C. Van de Sande 《Journal of mass spectrometry : JMS》1978,13(11):618-628
By means of chemical ionization 1,3-dioxolanylium as well as 1,3-dioxanylium ions are formed in proton catalysed SNi assisted heterolysis in the gas phase. The effects of both constitution and configuration are discussed and compared with the results of analogous reactions in the condensed phase. It is shown that the unimolecular decompositions of [MH]+ ions containing two vicinal substituents, e.g. Br or OAc, are not governed by the proton affinity of the departing neutrals HBr or HOAc, respectively. The findings partially contradict the results on HX loss (X: substituent) from protonated monosubstituted compounds. 相似文献
17.
Photo dissociation dynamics of diatomic molecular ion HBr+ interacting with ultra fast laser pulses of different envelop function has been presented both in zero and non zero temperature environment. The calculations pertain primarily to the ground electronic state of the molecular ion HBr+. The used potential of HBr+ is calibrated with the help of the ab initio theoretical calculation at the CCSD/6-311++G(3df, 2pd) level and then fitted with appropriate Morse parameters. The numerical bound states vibrational eigenvalues obtained by the time independent Fourier Grid Hamiltonian method have been compared with analytical values of the fitted Morse potential. The effect of temperature, pulse envelops function, and light intensity on the dissociation process has been explored. 相似文献
18.
The kinetics of the reactions OH + Br2 → HOBr + Br (1) and OD + Br2 → DOBr + Br (3) have been studied in the temperature range 230–360 K and at total pressure of 1 Torr of helium using the discharge‐flow mass spectrometric method. The following Arrhenius expressions were obtained either from the kinetics of product formation (HOBr, DOBr) in excess of Br2 over OH and OD or from the kinetics of Br2 consumption in excess of OH and OD: k1 = (1.8 ± 0.3) × 10−11 exp [(235 ± 50)/T] and k3 = (1.9 ± 0.2) × 10−11 exp [(220 ± 25)/T] cm3 molecule−1 s−1. For the reaction channels of the title reactions: OH + Br2 → BrO + HBr and OD + Br2 → BrO + DBr, the upper limits of the branching ratios were found to be 0.03 and 0.02 at T = 320 K, respectively. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 698–704, 1999 相似文献
19.
Sergey A. Adonin Mikhail A. Bondarenko Alexander S. Novikov Pavel A. Abramov Pavel E. Plyusnin Maxim N. Sokolov Vladimir P. Fedin 《无机化学与普通化学杂志》2019,645(18-19):1141-1145
Reactions of [SbIIIBr6]3– with Br2 in HBr in the presence of N‐substituted quinolinium or isoquinolinium cations result in new complexes of hexabromidoantimonates of SbV and their polybromide adducts: (N‐MeQuin)2{[SbBr6](Br3)} ( 1 ), (N‐MeIsoquin)2{[SbBr6](Br3)} ( 2 ), and (N‐EtQuin)[SbBr6] ( 3 ). Thermal stability was studied; estimated energies of supramolecular Br ··· Br interactions were calculated. 相似文献
20.
MNDO/PM3 Study of the Reaction Mechanism between Methane and Complexes Generated in Br2·AlBr3 System
A. L. Chistyakov I. V. Stankevich N. P. Gambaryan I. S. Akhrem 《Russian Journal of Organic Chemistry》2001,37(12):1675-1682
Potential energy surface (PES) of systems AlBr5 and AlBr5 + CH4
+ were investigated by MNDO/PM3 method. All the five donor-acceptor complexes Br2·AlBr3 with no barrier add to methane providing multiple adducts with various localization of interactions and with different conformations. However further transformations occur only with adducts of two complexes Br2·AlBr3 possessing considerable ionic character. On the reaction path resulting in CH3Br and HBr as intermediates function bromonium type complexes CH3BrH+·AlBr4
- and the intermediates on the path leading to CH2Br2 and H2 are the complexes with 3c-2e bond of H2 quasi-molecule with the C atom of bromomethyl cation H2C(H-H)Br+·AlBr4
-. Potential barriers on both reaction paths are about 30 kcal mol-1, and the transition states (TS) are analogous to the classical 3c-2e TS (Olah scheme) with an electrophile attack on a CH bond and to the recently suggested TS with an electrophile attack on an unshared electron pair of the carbon atom in the nonclassical methane H2C(H-H) respectively. 相似文献