Adsorption of pentacene on a silicon surface

A computational description of the chemical bonding interactions of a pentacene molecule on a Si(1 0 0)-(2 × 1) surface is carried out using a combination of tight-binding and Gaussian 98 ab initio approaches. These computations identify the molecular configurations responsible for the adsorption sites parallel and perpendicular to the dimer row observed in STM studies to be a nearly flat, relatively strain-free “tetra dimer”. The calculations confirm experimental evidence for strong monolayer adsorption dictated by the nature of the underlying reconstructed dimer row: The binding energies of the most stable perpendicular and parallel adsorption sites are 5.02 and 4.42 eV, respectively. The results are consistent with STM studies of sub-monolayer coverage of pentacene on silicon showing that the number of perpendicular adsorbed structures slightly exceeds those for parallel-adsorbed structures.