Silylenes deposition

The correlation of deposition rate with disilane concentration and the zero-barrier of the reaction of silane with silylene to disilane lead to the conclusion that the latter reaction is the dominant subsequent pathway following the silane fragmentation. Disilane shows two characteristic relaxation times, the slower being identical with the relaxation time of silane. In conclusion, the formation of... 

Both silane and silylene (SiH2) react heterogeneously at the channel-wall surface to form a silicon deposit and release hydrogen back to the gas flow. The rates of these reactions... 

The flux summary within the boxes in Fig. 17.2 shows the mass flux (g/cm2-s) of both the silane and silylene to the surface, resulting in deposition of silicon and release of volatile hydrogen. At low temperature, the film growth is primarily from silane, although it is quite low. By Ts = 925 K, there is sufficient silane decomposition that the surface fluxes of the two species are becoming comparable. At Ts = 1300 K, the silylene flux is dominant, carrying most of the silicon to the surface. 

When a solution of bis[2,4,6-triethylphenyl]silylene-2,4,6-tri-/-butylphenylphosphane in tetrahydrofuran was stirred in the presence of tellurium for 48 h, tellurium formed a bridge between the P and the Si atoms. The cyclic P —Te —Si compound could be flash-chromatographed on alumina with pentane, but decomposed in air within ten minutes with deposition of a blackish, metallic material4. 

IR ectra of the inadiation of the stable silylene 1 in an argon/CCU matrix (100 1). a Spectnun of silylene 1 after co deposition and annealing to 35 K (0.5 h). b After irradiation with 313 nm-light (3.5 h). c After longer irradiation with 313 nm-light (31 h). IR bands of the new reactive species ate marked with X. 

Gas-phase photolysis of silacyclopent-3-ene results m clean extrusion of silylene, yielding buta-1,3-diene, which undergoes secondaiy photolysis.It is suggested that this process is suitable for the chemical vapocr deposition of Si/ C/H films. The influence of an external magnetic field on the yields of the photodecomposition products of the 7,7-dimethyl-7-silanorbomadiene derivative (75) has been investigated in laser-pulse photolysis experiments. These experiments reveal the intermediacy of paramagnetic species (biradicals and dimethylsilylene). 

Although the deposition rate using N2O is lower than that with O2, high quality silicon-rich films are readily prepared via the reaction of silylene (SiH2) with N2O, Eq. 

Kushner MJ. On the balance between silylene and silyl radicals in rf glow discharges in silane the effect on deposition of a-Si H. J Appl Phys. 1987 62 2803-10. 

Linear polysilylenes, which are bonded to a silica surface, can be prepared by photolysis coupled with chemical vapor deposition (photoCVD) of small cychc oligosilanes (Scheme 6). For example, Obata and coworkers have shown that octapropylcyclo-tetra-silane (21) can be vaporized under vacuum at 210°CP Photolysis of the vapor at 254 nm presumably gives the transient species, [Pr2Si ] (22), which can be deposited on a pretreated quartz surface (24—>25) to form a poly-silylene film (26). The presence of polysUylene on the quartz surface is confirmed... 

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