The chemisorption of polyaromatic hydrocarbons on Si(100)H dangling bonds

The adsorption of polyacene molecules on a H-terminated Si(001)-2 x 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(100) surface. When a few hydrogen atoms have been selectively removed from the SiH(001) 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(001) 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. (c) 2008 Elsevier B.V. All rights reserved.