Thermal Decomposition of Tin Tetrachloride Based on Cl- and Sn-Concentration Measurements

Abstract

The kinetics of the thermal decomposition of tin tetrachloride has been studied experimentally and theoretically. Ab initio MO calculations showed that SnCl 4 finally decomposed into Sn( 3 P) and four chlorine atoms through four subsequent Sn-Cl bond dissociation channels. Two sets of kinetic experiments were performed using a shock tube equipped with atomic resonance absorption spectroscopy (ARAS). Chlorine atoms were first measured over the temperature range of 1250-1700 K and the total density range of 1.7 × 10 18 to 8.9 × 10 18 molecules cm -3 . The rate coefficient for the initial reaction step, SnCl 4 (+M) f SnCl 3 ( 2 A 1 ) + Cl (+M) (eq 1a), was found to be in the falloff region fairly close to the low-pressure limit under the present conditions. The second-order rate coefficient based on the Cl-atom measurements was determined to be k 1a 2nd ) 10 -5.37(0.62 exp [-(285 ( 18) kJ mol -1 /RT] cm 3 molecule -1 s -1 (error limits at the 2 standard deviation level). The second group of experiments was carried out by detecting tin atoms over the temperature range of 2250-2950 K and at a total density of 3.2 × 10 18 molecules cm -3 . The second-order rate coefficients for the subsequent reaction steps: SnCl 2 ( 1 A 1 ) (+M) f SnCl( 2 Π) + Cl (+M) (eq 3a) and SnCl( 2 Π) (+M) f Sn( 3 P) + Cl (+M) (eq 4a) were obtained to be k 3a 2nd ) 10 -8. 36(0.86 exp[-(310 ( 42) kJ mol -1 /RT] cm 3 molecule -1 s -1 and k 4a 2nd ) 10 -9.50(0.78 exp [-(265 ( 40) kJ mol -1 /RT] cm 3 molecule -1 s -1 , respectively. The Rice-Ramsperger-Kassel-Marcus (RRKM) calculations including variational transition state theory were also applied for reactions 1a and 3a. Structural parameters and vibrational frequencies of the reactants and transition states required for the RRKM calculations were obtained from the ab initio MO calculations. Energy barriers of the reactions, E 0 's, which are the most sensitive parameters in the calculations, were adjusted until the RRKM rate coefficients matched the observed ones. These fittings yielded E 0,1a ) 326 kJ mol -1 for reaction 1a and E 0,3a ) 368 kJ mol -1 for reaction 3a, in good agreement with the Sn-Cl bond dissociation energies of SnCl 4 and SnCl 2 , demonstrating that the experimental data for k 1a and k 3a were theoretically reasonable and acceptable.

Direct Bandgap Group IV Epitaxy on Si for Laser Applications

“…9(a) and (b). At highest carrier injections of 2x10 19 cm -3 , an n-doping density of about 1.3x10 19 cm -3 leads to a gain >6000 cm -1 at 300 K (>4000 cm -1 at 350 K) for the 12.5 at.% sample and a gain of 6800 cm -1 at 300 K (4800 cm -1 at 350 K) for the 14 at.% sample. Gain starts to saturate for even higher doping and/or injection levels.…”

“…Since the bond strength of SnCl amounts to a value (3.3 eV 19 ) even slightly larger than for the Ge-Ge bond in the digermane, differences in thermal decomposition should not have a major influence. Temperature variation also strongly impacts the growth rate.…”

“…% sample) and 4700 cm -1 (14 at. % sample) are predicted at 300 K for a carrier injection of 2x10 19 cm -3 without any additional doping. They drop to ~2600 cm -1 and ~3000 cm -1 , respectively, for a (more likely) higher temperature of the active layer, T = 350 K. The -L valley spacing in both samples amounts to ~60 meV, resulting from the opposing effects of alloy composition and compressive strain, as discussed before.…”

The gas-phase chemistry of carbon chains in dark cloud chemical models

“…In the case of carbon atom reactions, experimental room temperature rate constants for the reactions of carbon atoms with a series of alkenes, alkynes, dienes and diynes (Haider & Husain 1992, Haider & Husain 1993a, Haider & Husain 1993b, Husain & Ioannou 1997, Husain & Kirsch 1971b, Husain & Kirsch 1971a, Clary et al 1994) up to C + 1-hexadecene and C + 1-dodecyne seem to indicate a correlation between the size of the molecule and the rate constant, with the rate constant increasing for larger molecules in contrast with the theoretical capture rate constants for the reactions of carbon atoms with alkenes which show little variation. Theoretical study shows that of the three triplet electronic states correlating with C( 3 P) + 1 C 2 H 2 reagents, only one presents no barrier (Takahashi & Yamashita 1996). Considering the fine structure of the carbon atom leads to an electronic degeneracy factor equal to (1+2exp(-23.6/T))/(1+3exp(-23.6/T)+5exp(-62.4/T)), in relatively good agreement with the experimentally determined temperature dependence between 10 and 300 K (Chastaing et al 1999.…”

Ab initio calculations on SnCl2 and Franck-Condon factor simulations of its ã-X̃ and B̃-X̃ absorption and single-vibronic-level emission spectra

“…Normally, chlorides and organotin compounds, such as tin dichloride, tin tetrachloride, tetramethyltin, and dimethyldichlorotin, are used as Sn precursors for the gas-phase synthesis. [11][12][13] SnCl 2 , either as a precursor or an intermediate in the oxidation reaction leading to SnO 2 in the CVD process, is present near the surface layer of the growing SnO 2 thin film. In order to achieve efficient process control of an industrial high yield/ high volume CVD reactor, in situ monitoring of gaseous species, including SnCl 2 , in the CVD reactor under different experimental conditions by a spectroscopic technique is often carried out.…”