Abstract
The growth of polycrystalline silicon layers on 
and 
substrates can be hampered in the early stages of growth by the presence of different species adsorbed on the surface. In this article nucleation experiments with silicon on 
and 
are described in the 
system at temperatures between 600° and 900°C. In this temperature regime (and without
addition) the saturation nucleus density of silicon clusters on 
substrates shows a decrease in density with decreasing temperature, whereas on 
substrates the opposite occurs. Experiments with nitrogen as a carrier gas, however, give almost the same saturation nucleus densities of silicon clusters on 
and 
substrates. Additions of 
to the 
system produce a decrease in the nucleus saturation density on 
and 
substrates, and the density also decreases with decreasing temperatures below 900°C. It is further shown that selective growth of silicon on partly coated silicon substrates becomes more difficult at lower growth temperatures. Adsorption of different surface species (H, Cl, 
, and 
) on 
and 
substrates is discussed and it is concluded that a strong adsorption of atomic hydrogen, notably on 
surfaces, may explain the difference in nucleus densities on 
and 
substrates at temperatures below 900°C.