Dissociative adsorption of Si2H6 on the Si(001) surface

We present results of nb initio calculations, based on pseudopotentials and the density functional theory, for the dissociative adsorption of Si2H6 on the Si(001) surface. Various models are considered, containing H and the radicals SiH3 and SiH2. Models based on the SiH2 radical were considered with three adsorption sites: (i) an on-dimer position, (ii) an intrarow position between two neighboring Si dimers in the same dimer row, and (iii) an inter-row position between adjacent Si dimer rows. The intrarow and bridge geometries are considered with and without the saturation of the Si dangling bonds with hydrogen. For the 2 x 1 surface reconstruction, the on-dimer geometry is energetically more favorable than the inter-row geometry. For the 2 x 2 reconstruction, without hydrogen passivation of the Si dangling bonds, the on-dimer and intrarow geometries leave the system fully passivated. With hydrogen passivation of the Si dangling bonds, the on-dimer geometry is more favorable than the intrarow geometry.