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

Abstract

The adsorption and reaction of cyclopentene on the Ge͑001͒ surface is investigated by first-principles density-functional calculations within the generalized gradient approximation. Surprisingly, a recent cluster calculation for adsorbed cyclopentene on Ge͑001͒ obtained an adsorption energy of 2.10 eV, which is larger than the same cluster result ͑1.65 eV͒ on Si͑001͒. However, our calculated adsorption energy for 0.5͑1͒monolayer cyclopentene on Ge͑001͒ is 0.79͑0.51͒ 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 Ge͑001͒ and Si͑001͒ 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 Ge͑001͒ and Si͑001͒ surfaces.

Origin of nonlocal interactions in adsorption of polar molecules on Si(001)-2×1

“…Recent theoretical studies [10][11][12][13][14]16,34 have also suggested the importance of hydrogen bonding in H 2 O, NH 3 , and CH 3 NH 2 adsorption on Si͑001͒. A typical hydrogen bond ͑between a positively charged H atom and a small electronegative atom such as O and N͒ is about 0.2 eV in the gas phase.…”

“…Similarly, using DFT-slab calculations Cho and Kleinman 16 have predicted the alignment of dissociated CH 3 NH moieties by the N…H hydrogen-bonding interaction. However, recent DFT-slab calculation results reported by Wang and Hwang 10 have suggested that both molecular and dissociative CH 3 NH 2 adsorption structures at the saturation coverage prefer the zigzag arrangement due to adsorbate-adsorbate repulsion.…”

Adsorption of protected and unprotected amino-cyclopentene at the Si(100) surface modeled with a hybrid quantum mechanical cluster technique

“…The adsorption energy for this situation is −63.4 kcal mol −1 . A previous study, adsorbing not ACP but methylamine 18 at a concentration of 0.5 ML with DFT-GGA and a periodic slab, found an amine adsorption energy of −32.5 kcal mol −1 for the undissociated state, −47.0 kcal mol −1 for the H-dissociated state, and −60.2 kcal mol −1 for the C-dissociated state. We can see that the behavior of ACP when adsorbing through the amine group is basically similar to the one found for other amines.…”

“…This makes us predict that although the cyclopentenedissociated N-adsorbed ACP may have the highest adsorption energy, it must be very unlikely as it involves the breaking of a nitrogen-carbon bond which correlates to a very high energy transition state, while the H-dissociated form only involves a proton transfer between the amine and a silicon atom. 16,18 For other amines, the energy of the transition state involved in a C-dissociation was always above the energy of the free reagents by a prohibitive amount, hence, observing the conservative behavior of ACP, it is fair to assume that C-dissociation is nearly impossible. The three N-adsorbed structures are shown in Fig.…”

“…In order to compare to some extent our results with previous works, we have to rely on similarities between the adsorption of ACP, cyclopentene, [11][12][13][14] and amines [15][16][17][18] on the Si͑100͒ surface. ACP has got both a cyclopentene group and one amine; hence we expect to find comparable processes and energies when ACP connects only through one of them.…”