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

This paper reports the results of detailed experiments carried out to under stand the growth of a-Si:H films deposited by thermocatalytic chemical vapo r deposition (TCCVD) at different substrate temperatures (T-s). Kinetic ell ipsometry data reveal that the growth kinetics drastically changes as T-s i s increased from 110 to 450 degreesC. Although nucleation occurs at all T-s , a major difference is observed in the coalescence behavior. At the lowest T-s, no trace of coalescence is reflected in the data. In the intermediate T-s region, incomplete or partial coalescence introduces the lobe/cusp pat tern in the ((epsilon (1)),(epsilon (2))) curve, while above 350 degreesC, complete coalescence leads to the presence of a loop in the ((epsilon (1)), (epsilon (2))) data. We attribute this change in the ((epsilon (1)),(epsil on (2))) trajectory to a systematic variation in the surface reactivity and hydrogen coverage with increasing T-s. (C) 2001 Elsevier Science B.V. All rights reserved.