Adsorption Geometry of Anthracene and 4-Bromobiphenyl on TiO2(110) Surfaces

Abstract

Adsorption of anthracene and 4-bromobiphenyl on a TiO2 rutile(110) surface has been studied under ultrahigh vacuum conditions with scanning tunneling microscopy (STM) and thermal programmed desorption (TPD). Multilayer and single-layer desorption peaks were observed at 270 and 360 K for anthracene and at 260 and 360 K for bromobiphenyl, respectively. STM images taken at room temperature show that both molecules form periodic patterns on the TiO2 surface with individual molecules aligned along the 5-coordinated Ti atom row of the substrate. Individual molecules of the organic adsorbates are mobile on the surface in the [001] direction parallel to the atomic rows. The observed lateral alignment of the molecules suggests attractive interactions in the case of anthracene and repulsive in the case of bromobiphenyl.