Electronic Properties and Fragmentation Dynamics of Organic Species Deposited on Silicon Surfaces

This contribution summarizes recent progress in the computational treatment of organic species deposited on silicon surfaces, with emphasis on the Si(100) surface. Representative theoretical studies of various organic species in contact with Si surfaces are surveyed, involving unsaturated hydrocarbons, amines, phosphines, and alcohols as adsorbates. The connection of the presented computational results to spectroscopic measurement is outlined in each individual case. The strengths and the limitations of a finite cluster model for simulating the Si substrate are discussed. Further, a comprehensive investigation of one specific system is presented, namely 1-propanol adsorbed on Si(001) -(2× 1). It is shown by density functional theory within periodic boundary conditions that 1-propanol in contact with Si(001) -(2× 1) initially occupies a metastable physisorbed state which turns into a stable chemisorbed ground state by dissociative hydrogen transfer. This fragmentation effect is confirmed by

ab initio

molecular dynamics at room temperature. The adsorbed organic layer induces further surface reconstruction. For the first time, the band structure of the 1-propanole/Si(001) film is determined. The tendency of the energy gap as a function of 1-propanole coverage indicates that the surface becomes increasingly insulating as the areal density of the organic adsorbate is enhanced