Chemical reaction of benzoic acid with Ge(100): Effect of a phenyl substituent

The adsorption of benzoic acid onto Ge (100) was investigated using scanning tunneling microscopy (STM) and density functional theory (DFT) calculations. At room temperature, the on-top bidentate structure of benzoate molecules on Ge(100) was the most favorable. After annealing at 420 K, nearly all of the adsorption structures changed into on-top structures. The preference for the on-top structure could be explained in terms of the thermodynamic stability and kinetic considerations. Simulated STM images of the stable configuration could explain the experimentally observed images. The surface ordering of the adsorbed benzoic acid molecules was characterized through an appropriate application of hot surface dosing and annealing of the Ge surface at different coverages. Surface ordering along the dimer row direction was observed at a lower coverage. At saturation coverage, ordered lines with several adsorbed benzoic acid molecules formed along both the dimer row and the dimer direction and were stabilized through π-π stacking interactions.