Adsorption of ethylene on the Ge(100)-2 x 1 surface: Coverage and time-dependent behavior

Studies of the adsorption and thermal chemistry of ethylene on the Ge(100)- 2X1 surface have been performed. The results of multiple internal reflectio n Fourier transform infrared (MIR-FTIR) spectroscopy and temperature progra mmed desorption (TPD) show that ethylene chemisorbs molecularly on the Ge(1 00)-(2X1) surface at room temperature. Infrared spectroscopy gives evidence for only one adsorbate configuration on this surface at room temperature, consistent with a structure in which ethylene bridges across a germanium di mer. However, TPD measurements show two molecular desorption features at al most all coverages, indicating that at least two adsorption states can be f ormed. Further shifts in one of the peaks with both coverage and time, para lleled by changes in the vibrational spectrum, suggest the presence of attr active intermolecular interactions or cooperative effects. The complex time - and coverage dependence of ethylene adsorption on Ge(100)-2X1 is analyzed using a two-state kinetic model. (C) 1999 American Institute of Physics. [ S0021-9606(99)70321-1].