One-dimensional ordered structure of C2H4 on a Si(001) surface

A one-dimensional (1-D) ordered structure of ethylene (C2H4) molecules on a Si(001) surface has been investigated by using coaxial impact collision ion scattering spectroscopy (CAICISS) and computer simulations. In a previous paper, the di-σ on-top site of the Si(001)-(2X1) surface was exposed at room temperature (RT) to 100L (1L = 10-6 Torr·sec)of C2H4 molecules, which were intially absorbed on that surface. With increasing number of C2H4 molecules, a structural change of C2H4/Si(001)-(2X1) surface was observed by using the low-energy electron diffraction (LEED). When the Si(001)-(2X1) surface at RT to 200L of C2H4 molecules, the C2H4 molecules occupied the di-σ on-top site on the Si(001)-(2X1) surface. With the help of a computer simulation, the C - C and Si - C bond lengths were found to be 1.61 ± 0.05 A and 1.81 ± 0.05 A respectively. The C2H4 molecules were also found to be adsorbed on the Si(001) surface on in tandem along the direction of Si dimer-rows. This result provides evidence supporting the mechanism of 1-D nano-structure formation based on the C2H4 molecules on Si(001) surface.