Is the nucleation and coalescence behavior in the growth of a-Si:H films prepared by the CAT-CVD different?

Abstract

This paper reports the results of detailed experiments carried out to understand the growth of a-Si:H films deposited by thermocatalytic chemical vapor deposition (TCCVD) at different substrate temperatures (Ts). Kinetic ellipsometry data reveal that the growth kinetics drastically changes as Ts is increased from 110 to 450°C. Although nucleation occurs at all Ts, a major difference is observed in the coalescence behavior. At the lowest Ts, no trace of coalescence is reflected in the data. In the intermediate Ts region, incomplete or partial coalescence introduces the lobe/cusp pattern in the (left angle bracketvar epsilon1right-pointing angle bracket,left angle bracketvar epsilon2right-pointing angle bracket) curve, while above 350°C, complete coalescence leads to the presence of a loop in the (left angle bracketvar epsilon1right-pointing angle bracket,left angle bracketvar epsilon2right-pointing angle bracket) data. We attribute this change in the (left angle bracketvar epsilon1right-pointing angle bracket,left angle bracketvar epsilon2right-pointing angle bracket) trajectory to a systematic variation in the surface reactivity and hydrogen coverage with increasing Ts.