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

Abstract

The adsorption of [Formula: see text]-AminoTiophene on Si(100)2[Formula: see text][Formula: see text][Formula: see text]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 (2.71[Formula: see text]eV). 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 0.05–0.30[Formula: see text]eV 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 0.63–2.70[Formula: see text]eV 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.