Vinyltrimethylsilane (vtms) serves as a ligand in the precursor molecule Cu-(I)(vtms)(hfac) used in copper chemical vapor deposition. Investigations of the interaction of vtms with the Si(111)-(7x7) surface utilizing scanning tunneling microscopy, Auger electron spectroscopy, and thermal desorption spectroscopy (TDS) are reported. The adsorption is found to be highly site sensitive with an initial sticking coefficient most probably in excess of 0.03. With the exception of hydrogen, TDS spectra do not display vtms or any other desorbing species. Heating of the vtms covered surface to approximate to 530 degrees C leads to the formation of three-dimensional clusters which remain stable in shape and size up to temperatures as high as 1100 degrees C. We believe the observed clusters consist of carbon and/or SiC. In addition. the observation of (5x5) reconstructed areas between the clusters suggests the deposition of silicon during the annealing process. This indicates that vtms undergoes thermal decomposition on a silicon surface. This is in significant contrast to the observed behavior on metal and insulating surfaces. Consequently we cannot expect contaminant-free interfaces between the Si(111) substrate and copper films grown from the Cu-(I)(vtms)(hfac) precursor.