Modeling the Adsorption of Phosphine on the Si(100)-2x1 Surface with Ab Initio Theory Calculations

Michael Mysinger, Stanford University

The adsorption of phosphine on the Si(100)-2x1 surface is a difficult system to model due to the non-local character of the electron transfer arising from the formation of the Si-P dative bond. We first model this non-local effect with a couple of clusters, Si9H12 and Si21H20, which model the surface along the dimer row; and with a third cluster, Si23H24, which models dimers separated by the surface trench. We characterize some of errors involved in the cluster calculations, associated with cluster constraints, the basis set size, and the level of theory. We compare the fully relaxed cluster with an over-constrained cluster to estimate upper and lower bounds of the potential energy surface. We compare the effects of a very large basis set with the split basis set we used for the majority of our computations. Finally, we calculate the errors in the level of theory by comparing the Becke3LYP DFT method we used with the QCISD(T) method. We find that with this non-local chemistry, cluster size is important while constraint effects are not usually important. The errors due to the basis set and the level of theory are small for large clusters.

Abstract Author(s): Michael Mysinger