Hydrocarbon molecules deposited onto monolayer steps on Si (100): a study of absorption and conductance

In this study the interactions of small hydrocarbon molecules with monolayer SA steps onto Si(1 0 0) are considered. The study deals with both the adsorption and the transport properties of the deposited system and the flat, dimerized surface is used as a reference. The calculations are based on a semi-empirical Hamiltonian, which is applied to the evaluation of the total energy and of the conductance, and this last quantity is obtained from the scattering theory. It has been found that, though the step is a weaker sink than the flat surface, adsorption is possible and all the molecules are bonded to the step. The functional relationship between the binding energy and the type of the adsorbed molecule is reminiscent of the intrinsic binding energy of the molecule itself and is therefore similar for the flat surface and for the step. Resonances of the transmission function are observed whose primary dependence is on the coupling between the device region and the contacts.