Silanes, sticking coefficients

The top panel of Fig. 17.2 (Ts = 800 K) reveals that there is very little decomposition of the silane in the gas phase, which is a result of the relatively low temperature. As a result the net growth rates should be expected to be quite low, since the silane sticking coefficient is so low. At a surface temperature of Ts = 1300 K, however, the decomposition of silane to silylene in the gas-phase boundary layer is nearly complete. The relatively high silylene concentrations should lead to high growth-rates. The peak in the silylene profile at about 1.5 mm above the surface results from the competition between production by the homogeneous decomposition reaction and consumption at the surface by heterogeneous reaction. 

The surface reactions are based on sticking coefficients. Silylene (S1H2), which is very reactive, has a sticking coefficient of unity. The silane, which is much less reactive, has an activated sticking coefficient, given as... 

The silane-containing feed gases have high sticking coefficients (they are also characterized by insignificant rates of surface diffusion), which provide high deposition rates on one... 

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