Structural study of 1,4-cyclohexadiene adsorption on Si(0 0 1) surface by low energy photoelectron diffraction

The structural properties of the subsaturation coverage of 1,4-cyclohexadiene (C6H8) on single domain Si(0 0 1)-2 × 1 surface have been investigated by using photoelectron diffraction (PD) at the C1s core level and at the photon energy of 330 eV. The high resolution core level study allows to determine the presence of a shifted replica of +0.9 eV in kinetic energy. The structural properties of adsorbed molecules are discussed at the light of ab initio multiple scattering calculations on several adsorption models with about the same least total energy. This quantitative experimental determination timely follows the many qualitative assessments present in literature for this important prototypical case of functional Si substrate and aims to fill the gaps between several experiments reported.