Cycloaddition chemistry on germanium(001) surfaces: the adsorption and reaction of cyclopentene and cyclohexene

The adsorption and reaction of two cyclic unsaturated hydrocarbons, cyclopentene and cyclohexene, with the Ge(001) surface has been investigated. The subsequent surface interactions were followed by a variety of surface-sensitive techniques. Bonding configurations were determined by photoelectron spectroscopy, infrared spectroscopy and scanning tunneling microscopy. The strength of surface interactions was also monitored by temperature-programmed desorption. Cyclopentene and cyclohexene react with surface germanium-dimer bonds to yield reaction products that are consistent with a [2+2] cycloaddition reaction. This reaction generates rows of the surface complex oriented along the dimer-bond direction of the Ge(001) surface, which is easily observed by scanning tunneling microscopy.