Chiral adsorption of styrene on Ge(100)

Abstract

The adsorption structure and thermal desorption of styrene on Ge(100) has been investigated using scanning tunnelling microscopy (STM) and temperature programmed desorption (TPD). Styrene adsorbs in two different adsorption geometries: on the top of a single Ge-Ge dimer (OT) and in a paired end-bridge between two neighboring Ge dimers within the same dimer row (PEB). According to the arrangement of phenyl ring in the PEB configuration, the PEB configurations are divided into cis-PEB and trans-PEB configurations in which the latter is more stable. In low temperature TPD spectra, the desorption peaks of the OT configuration and the PEB configurations are observed at 320 K and 365 K respectively. In addition, we find chiral adsorbates on the Ge(100) surface. For the OT configuration, there are two (S) and (R) chiral products, and we can distinguish enantiomeric (R R), (S S) trans-PEB configuration. The OT configuration converts into a thermodynamically more stable PEB configuration through tip-induced diffusion. Both the OT configuration and the PEB configuration desorb at -2.60 V of sample bias, and the interconversion between the PEB configurations is observed.