Internal friction study of ion-implantation induced defects in silicon

Using a sensitive silicon paddle oscillator technique, we measured the internal friction of single-crystalline silicon substrate implanted with As+, Si+, B+, and H+ ions with a dose of ∼1019  m−2. A distinct internal friction peak at about 48 K is observed in all cases. The overall internal friction from 0.4 K to room temperature is also similar for the different species of ions used. The peak shifts to lower temperature at a reduced resonance frequency, characteristic of a thermally activated relaxation. The insensitivity of the peak to the ion species indicates that it is caused by a vacancy-type defect. Isochronal annealing study shows that the peak anneals away at a temperature between 200 and 300 ° C, and that is consistent with divacancy defects. By plasma etching the substrate layer by layer, we have identified that the defects are concentrated at a damaged crystalline layer right underneath the top amorphized layer in the Si+ implanted sample. The exact mechanism that caused the relaxation peak is still not clear, although our quantitative analysis points to an electronic origin.