Influences of ion-beam irradiation on solid-phase-crystallization of a-Si on SiO2 were studied in the temperature range between 200 and 700 degreesC. Significant enhancement of crystal nucleation was observed under ion irradiation (25 keV, 1 x 10(16) Ar+ cm(-2)). As a result, nucleation at a temperature lower than that of the softening of soda-lime glass (450 degreesC) becomes possible. In addition, nuclei growth along the [111] and [110] directions was detected using X-ray diffraction methods. These are a big advantage for the fabrication of high-quality and low-cost thin-film transistors on glass substrates.