Pa by increasing the SiCl4 flow at a fixed H2 carrier flow. The C2H4 flow was also increased accordingly to afford a C/Si of 1 in the input gas phase. It can be seen in Figure (a) that GRtop increases with increasing pSi but also seems to saturate, again indicating that the temperature of 950 °C is at the transition between kinetics limited and mass transport limited growth regimes. While the GRtop gradually approaches saturation with increasing pSi, the GRbottom continues to rise and exceeds that of the top after pSi is increased beyond 20 Pa. This saturation of growth rate at the top with increasing precursor partial pressure at a constant temperature has been observed in the deposition of metallic Cu from Cu(hfac)tmvs and of HfB2 from Hf(BH4)4 and could be described by a first-order Langmuir isotherm :