Interaction of CH₃ and H with amorphous hydrocarbon surfaces: estimation of reaction cross sections using Bayesian probability theory

The interaction of CH₃ and H with amorphous hydrocarbon surfaces plays a central role during plasma deposition of such films. Recently, this interaction has been explored in particle beam experiments. A rate equation model has been proposed which explains the experimental observations on the basis of elementary surface reactions. This model includes several parameters which have the meaning of either a reaction cross section or a rate constant. The predictive power of the model and its applicability to more complex hydrocarbon deposition processes hinges on a reliable determination of the model parameters. In this paper, we develop a Bayesian analysis of the data. The result of this analysis are estimation distributions for each parameter rather than single numbers. We use this in-depth information to draw valuable conclusions about the ability of the model to describe the surface reactions. We find strong indications for a dependence of the reaction cross sections on the particles' angle of incidence.