Silicon single crystals were irradiated at room temperature (RT) with single and dual low-velocity (i.e., 900 keV I) and high-velocity (i.e., 27 MeV Fe or 36 MeV W) ion beams in order to study synergistic effects between nuclear and electronic energy losses in semiconductors. The damage created by irradiation was quantified by using Rutherford backscattering spectrometry in the channeling mode and Raman spectroscopy, and it was visualized using transmission electron microscopy. Whereas single low-velocity ion irradiation leads to amorphization of the surface layer of Si crystals, the use of a dual low- and high-velocity ion beam prevents this phase transformation. However, a remaining disorder exists, the level of which depends on the ratio of the high- to low-velocity ion fluxes. The higher the ratio (1.6 in the present case), the lower the disorder level, with a 30% integrated disorder instead of 100% upon single low-energy irradiation. These results provide evidence that ionization-induced disorder annealing can occur at RT in Si.