Mechanisms of growth of nanocrystalline silicon deposited by hot-wire chemical vapor deposition

We have studied the growth of silicon thin films by hot-wire chemical vapor deposition under different conditions of filament temperature (T_f) and hydrogen dilution ratio (R). We found that these two parameters have a similar effect on the properties of the deposited films and show how they interact to control the growth dynamics. For relatively low values of T_f and/or R, the films are amorphous. An increase in the value of these parameters results in the appearance of a new phase, characterized by heavily faulted (220)-oriented columnar grains; for even higher values, a randomly oriented nanocrystalline phase appears. In general, there is more than one phase present in the film, and the microstructure varies as we go from the bottom to the top of the film. Although T_f and R have similar effects on the physical properties, they affect the deposition rate in a different way.