Kinetics of dissociative water adsorption on stepped Si(001), on Si(115), Si(113), Si(5,5,12) and Si(112)

We present photoelectron spectroscopic and low energy electron diffraction measurements of water adsorption on flat Si samples of the orientations (001), (115), (113), (5,5,12) and (112) as well as on curved samples covering continuously the ranges (001)-(117) and (113)-(5,5,12)-(112). On all orientations, water adsorption is dissociative (OH and H) and non-destructive. On Si(001) the sticking coefficient S and the saturation coverage Theta(sat) are largest. On Si(001) and for small miscuts in the [110]-azimuth, S is constant nearly up to saturation which proves that the kinetics involves a weakly bound mobile precursor state. For (001)-vicinals with high miscut angles (9-13 degrees), the step structure breaks down, the precursor mobility is affected and the adsorption kinetics changed. On (115), (113), (5,5,12) and (112), the values of S and Theta(sat) are smaller which indicates that not all sites are able to dissociate and bind water. For (113) the shape of the adsorption curves Theta versus exposure shows the existence of two adsorption processes, one with mobile precursor kinetics and one with Langmuir-like kinetics. On (5,5,12), two processes with mobile precursor kinetics are observed which are ascribed to adsorption on different surface regions within the large surface unit cell. From the corresponding values of S and Theta(sat), data for structure models are deduced. (C) 1997 Elsevier Science B.V.

Kinetics and transport model for the chemical vapor epitaxy of GexSi1-x

A numerical model that combines mass transport and surface kinetics was applied, for the first time, to the chemical vapor epitaxy of GexSi1-x. The temperature, velocity and concentration fields were calculated from the conservation equations for energy, momentum and species coupled with the boundary conditions on the growth surface which were determined by surface kinetics. The deposition rates of Si and Ge were assumed to be limited, respectively, by surface kinetics and mass transport. A theoretical relation between the initial conditions and the Ge composition in the solid was established. The calculated growth rate as well as the Ge composition in the solid and its dependence on growth temperature agree well with experimental data.