Preamorphous damage in p-type Si implanted with MeV Si ions and annealed at elevated temperature is characterized using deep level transient spectroscopy (DLTS) and transmission electron microscopy (TEM). P-type Si was implanted with 4 MeV Si at doses from 1×1013 to 1×1014 cm-2 and annealed at 800 °C for 15 min. For doses below this critical dose, a sharp peak is observed in the DLTS spectrum, corresponding to the signature of point defects. Above the critical dose, a broad DLTS peak is obtained, indicating the presence of extended defects. This behavior is found to be consistent with TEM analyses where extended defects are only observed for doses above the critical dose. This suggests a critical dose at which point defects from implantation act as nucleating sites for extended defect formation. © 1998 American Institute of Physics.