The chemisorption of polyaromatic hydrocarbons on Si(1 0 0)H dangling bonds

The adsorption of polyacene molecules on a H-terminated Si(0 0 1)-2 × 1 surface where a few hydrogen atoms have been extracted is presented using the semi-empirical ASED+ method. To scale up the qualitative ASED+ method, the adsorption of benzene and pentacene on a clean silicon surface is first compared with DFT calculations together with their adsorption on a fully hydrogenated Si(1 0 0) surface. When a few hydrogen atoms have been selectively removed from the SiH(0 0 1) surface, ASED+ demonstrates a difficult chemisorption for the polyacenes series on one dangling bond and a large interaction on two dangling bonds compensating for the large molecule deformation required. The influence of the nearest H atoms when the molecule is adsorbed on two dangling bonds of a passivated Si(0 0 1) surface is very small. On a clean and on a partially hydrogenated surface, all the polyacenes need to overcome an energy barrier of 0.3–0.4 eV to reach a chemisorption state.