Monosilanes pyrolysis

Stokland74 found that SiD4 decomposed more slowly than SiH4. There seemed to be a systematic increase in the ratio of the rate coefficients, kD/kH (for the second stage of the pyrolysis), from about 0.54 at 648 °K to ca. 0.7 at 764 °K. The experimental conditions used by all investigators of monosilane pyrolysis, and their results, are summarized in Table 3. 

Fig. 10. Product-time curves for the initial stages of pyrolysis of 77 torr monosilane at 430 °C. (3 min = 20 % decomposition.) (From Purnell and Walsh67.)...

Their pressure records at the beginning of the reaction show that no induction period similar to that observed during the pyrolysis of monosilane occurs. This suggests that the overall reaction... 

The possibilities of synthesis are limited by the general properties of the Si-Si bond to a small number of reaction types. Disilane derivatives were usually synthesized by a Wurtz-like reaction of monosilane halide derivatives with alkali or alkaline-earth elements. Some pyrolysis reactions that have yielded disilane derivatives are also known. Often, new disilane derivatives were prepared from common derivatives by an exchange of substituents. Some rearrangements have been observed in recent years. 

Test samples were fabricated by Si and Ge monohydrides pyrolysis in the gas mixture at the total pressure of 35-40 Pa with monogerman to monosilane volume ratio of 0.001-0.002. Temperature of the process was not higher than 680°C. P-doped silicon wafers (100) were used as substrates. Before the pyrolysis process we have oxidized the surface of some silicon wafers in dry oxygen in order to form thin silicon dioxide layer. In addition dysprosium and yttrium oxides were also formed on the wafer surface for other samples by the process of their deposition and following oxidation. 

Polycarbosilanes are usually synthesized by the thermal decomposition of monosilanes or disilanes and by ring-opening polymerization of disilacyclobu-tanes. Fritz et al. sythesized polycarbosilanes (PC-TMS) by heat condensation of tetramethylsilane at 700°C, circulating unreacted silane repeatedly in a continuous pyrolysis furnace [12]. 

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