An anisotropy associated with the diffusion of styrene on the hydrogen-terminated (100)-2x1 silicon surface was attributed largely to surface reconstruction. The anisotropy was determined by using a novel scanning tunneling microscopy technique and by using a combination of dispersion-corrected density functional theory with Monte Carlo simulations. The scanning tunneling microscope tip was used to create a box of clean silicon surrounded by H-Si. Styrene molecules diffused from the H-Si surface to the clean surface, where they stuck with unit probability. Reduction of the box dimensions following the room-temperature diffusion of styrene was measured using scanning tunneling microscopy, and reflected the diffusion anisotropy without influence from the scanning tunneling microscope tip. Density functional theory calculations were used to compute the dispersion binding of styrene on H-Si as well as the barrier heights associated with diffusion. These data were used to provide input for Monte Carlo diffusion simulations. Experiment and theory predicted results that were in excellent agreement: giving anisotropies of 1.1 and 1.06, respectively.

Experimental and Theoretical Exploration of the Anisotropy of Styrene Diffusion on Hydrogen Terminated Si(100)-2x1. S.Sinha, G.A.Dilabio, R.A.Wolkow: Journal of Physical Chemistry C, 2010, 114[16], 7364-71