A KrF (248 nm) pulsed laser was used to melt 90-, 190-, and 440-nm thick amorphous silicon layers produced by Si ion implantation into (100) crystalline Si substrates. Time-resolved reflectivity measurements at two different probe wavelengths (633 nm and 1. 15 mu m) and post-irradiation TEM measurements were used to study the formation of an undercooled liquid Si phase and the subsequent solidification processes. Measurements with the infrared probe beam reveal a buried, propagating liquid layer at low laser energy densities. This liquid layer is generated in part by the release of latent heat associated with nucleation and growth process.