Adsorption structures of thiophene on Si(1 0 0)-(2 × 1) studied by scanning tunneling microscopy and density functional theory

The adsorption states of thiophene on the Si(1 0 0)-(2 × 1) surfaces have been investigated using scanning tunneling microscopy (STM) and density functional theory (DFT). Comparison of bias dependent images of STM with DFT results indicate that room temperature adsorption at low coverages leads to four types of configurations; 2,3-dihydrothiophene-like and 2,5-dihydrothiophene-like species as di-σ bonded structures, twisted bridge-like and tight-bridge tetrahydrothiophene-like species as tetra-σ bonded structures. Conversion from the di-σ structures to the tetra-σ ones occurs at room temperature. The population ratios of the configurations observed with and without STM scans confirm that this conversion takes place thermally.