Density Functional Theory Study Of The Near Edge X-ray Absorption Fine Structure And Infrared Spectroscopy Of Acetylene And Benzene On Group Iv Semiconductor Surfaces

摘要

The near edge X-ray absorption fine structure and infrared spectroscopy of acetylene and benzene adsorbed on C(100)-2 × 1, Si(100)-2 × 1 and Ge(100)-2 × 1 surfaces is studied with density functional theory calculations. Time dependent density functional theory calculations of the near edge X-ray absorption fine structure with a modified exchange-correlation functional agree well with experiment, and show that the spectral features arise from excitation to π~+, σ_(C-H)~+ and σ_(X-C)~+ orbitals, where X represents C, Si or Ge. The σ_(X-C)~+ excitation energies are dependent on the surface, and for acetylene, the location of the π band also varies with the surface. Calculations of the vibrational modes show the C-H stretching frequencies for carbon atoms bonded directly to the surface vary significantly between the three surfaces, while those for carbon atoms not bonded to the surface do not change significantly.