α -Amino Thiophene on Si(100)2 × 1: Adsorption and transition states investigated by van der Waals corrected DFT and CI-NEB

The adsorption of α-AminoTiophene on Si(100)2×1 was investigated by van der Waals corrected DFT and climbing image nudged-elastic band, in view of potential applications in silicon-based technologies. The overall scenario indicates that dissociative states are more favorable than the molecular ones, the one occurring through N-C bond breakage and Si-N and Si-C bond formation, having the largest adsorption energy (2.71eV). Furthermore, this configuration is also kinetically easily accessible, being connecting to one of the physisorbed states (Phys1) by a nearly barrierless transition. Also the molecular states are relatively easily kinetically accessible, with transition barriers from the corresponding physisorbed states in the 0.05-0.30eV range. At variance with this, the transitions to the dissociative state characterized by N-H bond breakage and Si-N and Si-H bond formation (N-H Diss) either from physisorbed or from molecular states are all significantly higher, i.e. in the 0.63-2.70eV range. Finally, the effects of the coverage on the adsorption energy were evaluated for the N-H Diss configuration and indicating a gain, whose extent depends both on the coverage and on the surface arrangement, i.e. whether cis or trans. The trend is different if the vdW forces are excluded.