Infrared spectroscopy studies of iodoethane on Si(100)-2X1: Adsorption andthermal decomposition leading to adsorbate ordering

The adsorption and chemical transformation of iodoethane were studied on a Si(100)-2x1 surface using multiple-internal reflection Fourier-transform in frared spectroscopy (MIR-FTIR). The C-H and Si-H stretch vibrations served as fingerprints of all surface transformations. Although ethyl groups are s table on the Si(100)-2x1 surface at room temperature, thermal annealing stu dies suggest the reaction-limited formation of ethylene, a major hydrocarbo n reaction product, accompanied by the loss of hydrogen, which is left on t he surface until the temperature of recombinative H-2 desorption is reached . Variable temperature studies indicate that ethyl groups are the only hydr ocarbon entities on a surface up until the hydrogen elimination temperature . The positions of Si-H stretching bands suggest that a mixture of surface sites is formed at temperatures between 300 K and 600 K. However, the major ity of surface hydrogen forms SiH-SiI surface species as the surface temper ature reaches 700 K. (C) 2001 American Institute of Physics.