Thermal and ion-induced reactions of 1,1-difluoroethylene (1,1-C2H2F2 or iso-DFE) on Si(111)7x7 and vitreous SiO2 surfaces have been investigated by vibrational electron energy loss spectroscopy and thermal desorption spectrometry. Like ethylene, iso-DFE predominantly chemisorbs via a [2 + 2] cycloaddition mechanism onto the 7x7 surface as a di-sigma-bonded difluoroethane-1,2-diyl adstructure, which undergoes H abstraction and defluorination, producing hydrocarbon fragments and SiFx (x = 1-3) upon annealing to > 700 K. Ion irradiation of Si(111)7x7 in iso-DFE at 50 eV impact energy appears to substantially enhance the production of hydrocarbon fragments and SiFx, leading to stronger SiF4 desorption products over an extended temperature range (400-900 K). The observed SiC and SiFx produced on the 7 x 7 surface by ion irradiation in iso-DFE are found to be similar to those obtained by ion irradiation in the fluoromethane homologues, CF4 and CH2F2. The production of higher relative concentrations for the larger SiFx and C-2-containing fragments is evidently favored on the 7x7 surface. On a vitreous SiO2 Surface, ion irradiation in iso-DFE, unlike that in CF4 and CH2F2, appears to produce less SiFx than that on the 7x7 surface, which indicates that surface 0 does not interact strongly with the C2-containing fragments. The presence or absence of a C=C bond and the relative F-to-C ratio of the sputtering gas could therefore produce important effects on the resulting surface products obtained by low-energy ion irradiation.