Hydrocarbon Molecules Deposited onto Silicon Surfaces: A DFT Study of Adsorption and Conductance

The purpose of this study is a systematic description of the properties of small deposited clusters in dependence of the cluster geometry and composition and of the shape of the adsorbing surface. Therefore hydrocarbon molecules deposited onto the dimerized Si(100) surface and onto monolayer steps of this surface, are considered and the properties of these systems are determined using the Density Functional and scattering theories. It has been found that, though the step is a weaker sink than the flat surface, the molecules are bonded to the step and the adsorption geometries reproduce the ones of the flat surface. The transmission function depends on the type of molecule and of the substrate and on the transport channels available to the deposited system. However the contact potential has a paramount importance and deep resonances are produced by a proper tuning of this quantity.