Dissociation silane

The total dissociation cross sections of silane and disilane have been taken from Perrin et al. [201]. An uncertainty in the present knowledge of the silane chemistry is the branching ratio of the silane dissociation channels [192]. Here, the branching ratio is taken from Doyle et al. [197], who suggest using the branching ratio determined by Perkins et al. [202] for photolysis, viz., a branching of... 

The analysis of the neutral gas composition in a discharge yields useful information on the mechanisms and kinetics of silane dissociation. However, it should be borne in mind that with mass-spectrometric analysis one only detects the final products of a possibly long chain of reactions. 

This is consistent with D(i-C4H9-H) = 392 kJ mol-1, an increase of 11 kJ mol-1 over that earlier claimed60. The importance of this result is that it shows that there is nothing intrinsically wrong with the technique itself, but rather some of the earlier studies had systematic errors. There is thus no reason to doubt the general validity of the results derived for silane dissociation energies (care must always, however, be taken in every set of experimental measurements ). 

OA much more rapidly than C-H 4.4 ps compared to 230 ns. There is experimental evidence, described below, that silanes appear to be both better a donors andn acceptors in conparison with H2. Substituents at both M and at Si have large effects on the degree of activation toward OA and also on the reverse process, reductive elimination, i.e., silane dissociation. Silanes dissociate more slowly for conplexes with electron-rich M or more electronegative substituents at Si e.g., Cp(CO)2Re(HSiPh3) with elongated dgm undergoes silane elimination much more... 

A number of complexes have been prepared from the electron-rich ligand 3,5-di(tert-butyl)-l,2,4-triphospholyl these include manganese carbonyl complexes and the manganocene, which has been structurally characterised. A paper explaining the facile silane dissociation in transition metal T -silane complexes Cp(CO)2M[p -H(SiH3 Cl )] (M = Mn, Tc and Re n = 1-3) (see, for example, 28) makes interesting reading. ... 

The SiH radical is tlie dominant growtli precursor for tlie fonnation of tlie a-Si H films in a low-temperature silane plasma [32]. Silane molecules are dissociated by energetic plasma electrons ... 

The relative abundance of neutral SiH and H2 species have been measured as a function of power, pressure, flow rate, and dilution. For low power levels, eg, 5 W, up to 50% of the SiH gas is dissociated and the percentage increases to 80% for a power of 50 W. The decomposition of SiH gas proceeds more readily with lower flow rates. These observations, coupled with infrared (ir) measurements performed on the films, suggest that deposition under conditions in which the silane gas is not entirely decomposed leads to a majority of SiH units, whereas those deposited under conditions in which silane is strongly dissociated contain a majority of dihydride units leading to a deterioration of the semiconductor. Also, when the dwell time of SiH in the plasma region increases, the resultant film exhibits a pronounced peak at 2090 cm from the ir spectra corresponding to S1H2 inclusion. 

Table 1. Electron Impact Dissociative Processes Operative in Silane Plasma ...

Table 2. Reactions Within Plasma During Transport of Species Produced by Electron Impact Dissociation of Silane...

The effective absorption of radiation by a gas can be increased by the addition of a sensitizer. For example, when mercuty vapour is added to silane gas, the mercury vapour absorbs radiation to form an excited atom Hg which collides with a silane molecule to lead to partial dissociation... 

All of the atomic species which may be produced by photon decomposition are present in plasma as well as the ionized states. The number of possible reactions is therefore also increased. As an example, die plasma decomposition of silane, SiH4, leads to the formation of the species, SiH3, SiHa, H, SiH, SiH3+ and H2+. Recombination reactions may occur between the ionized states and electrons to produce dissociated molecules either direcdy, or tlrrough the intermediate formation of excited state molecules. 

Using CO-saturated hydrocarbon matrices, Pearsall and West" photolyzed sily-lene precursors at 77 K and monitored CO coordination to the silylenes by UV-vis spectroscopy (Scheme 13). Bis(trimethylsilyl)silanes 44a-c or SifiMcji were irradiated at 254 nm to create silylenes 45a-d, which reacted with CO, causing new peaks to ca. 290 and 350 nm, which were attributed to complex 46a-d, a resonance structure of silaketene 47a-d. Silylene adducts form fairly weak bonds, as seen by warming of the matrices. In the case of silylene adducts where one R = Mes, the CO dissociates and the corresponding disilene 48a-c peaks in the UV-vis spectra observed upon warming (R2 = Me most likely produced silane rings Si, Me6. etc.). 

Dissociation of the gases SiH4 and H2 by electron impact will create reactive species (radicals) and/or neutrals (Si2H6 and even higher-order silanes [195-198]). Atomic hydrogen is an important particle because it is formed in nearly all electron impact collisions, and the H-abstraction reaction [199, 200] of (di)silane is an important process, as is seen from sensitivity study. Dissociation of SiHa can create different SiH (with x = 0, 1,2, 3) radicals. Only silylene (SiH2) and... 

The relative pressure of disilane increases as a function of total pressure, due to the increased production of radicals, which is a result of increased dissociation of silane, as well as to the shorter gas volume reaction times and longer diffusion times to the walls, which result from increasing the pressure. 

Both model and experiment show the same tendency the dissociation of silane increases as a function of RF frequency. This can be explained following the arguments from Heintze and Zedlitz [236]. They found that the power dissipated by the ions in the sheaths decreases with increasing RF frequency. This is confirmed... 

The decrease of the silane partial pressure and the concomitant increase of the hydrogen partial pressure as a function of plasma power can be understood in terms of the increased electron density and electron energy. Both lead to a higher dissociation of silane and hydrogen. The silane radicals and atomic hydrogen thus... 

The partial pressure of disilane as a function of plasma power first increases due to the higher production of silane radicals. Above a certain power the increase in disilane dissociation is higher than the increase in disilane production hence the disilane partial pressure decreases again. Similar behavior has been obserbed by Kae-Nuneet al. [217]. 

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