Atomic and electronic structure of styrene on Ge(100)

Coverage-dependent adsorption structures of styrene on a Ge(100) surface were investigated using density functional theory (DFT) calculations. The most favorable configuration at room temperature is that the two styrene molecules are bound to two Ge dimers with paired end-bridged (PEB) configuration via the reaction of the vinyl CC double bond. The phenyl rings of the two styrene molecules are trans relative to the Ge dimer rows. Due to the bulky and electronic nature of the phenyl ring, its spatial orientation relative to the Ge surface affects the thermodynamic stability of each configuration. The buckling properties of surface Ge dimers also affect their interaction with the phenyl ring. Simulated STM images of this PEB configuration for empty states explain well the adsorption features observed in the experiment, as well as for filled states. Detailed electronic structures were also investigated through the PDOS analysis.