We investigate the role of the dopant in silicon on the dynamics of a single adsorbed molecule. We demonstrate that the dynamics of a single bistable molecule, a biphenyl molecule, adsorbed on a $\mathrm{Si}\left(100\right)\text{−}(2\times 1)$ surface is markedly dependent on the silicon type of doping ($p$ or $n$) even though the electronic excitation and relaxation processes are unchanged. Both strongly and weakly chemisorbed individual biphenyl molecules are shown to interact differently with $p$- or $n$-doped Si(100) surfaces, thus inducing different stabilities of the adsorption configurations and different molecular dynamics. These effects rely on electrostatic interactions between distributed charges inside the molecule and charged surface states. The described phenomenon, which is a priori general, should be applicable to most of the molecules adsorbed on doped semiconductors having surface states in their band gap. This result is anticipated to have important applications in molecular electronic for positioning individual molecules with precision.

• Received 10 September 2007

DOI:https://doi.org/10.1103/PhysRevB.77.125316