First-principles study of the adsorption and reaction of cyclopentene on Ge(001)

The adsorption and reaction of cyclopentene on the Ge(001) surface is investigated by first-principles density-functional calculations within the generalized gradient approximation. Surprisingly, a recent cluster calculation for adsorbed cyclopentene on Ge(001) obtained an adsorption energy of 2.10 eV, which is larger than the same cluster result (1.65 eV) on Si(001). However, our calculated adsorption energy for 0.5(1)-monolayer cyclopentene on Ge(001) is 0.79(0.51) eV, comparable with an observed activation energy of 0.7 eV for desorption. In addition we find that the energy barriers for the adsorption of cyclopentene on Ge(001) and Si(001) not only depend on cyclopentene coverage but also quantitatively differ from each other. Based on the calculated energy profile for the reaction we discuss the experimental observations of the difference between cyclopentene sticking on the Ge(001) and Si(001) surfaces.