Binding structures of propylene glycol stereoisomers on the Si(001)-21 surface: A combined scanning tunneling microscopy and theoretical study

The binding configuration of propylene glycol stereoisomer molecules adsorbed on the Si(001)-21 surface was investigated using a combination of scanning tunneling microscopy (STM) and density functional theory calculations. Propylene glycol was found to adsorb dissociatively via two hydroxyl groups exclusively as a bridge between the ends of two adjacent dimers along the dimer row. The chirality was preserved during bonding to Si atoms and was identifiable with STM imaging. The large number of propylene glycol conformers in the gas phase was reduced to a single configuration adsorbed on the surface at low molecular coverage.