Divacancies in proton irradiated silicon: Comparison of annealing mechanisms studied with infrared spectroscopy and positron annihilation

Defects produced in 8 MeV proton irradiated silicon were studied using Fourier transform infrared spectroscopy (FTIR) and positron annihilation measurements (PAS). Isothermal annealing of the divacancy absorption band monitored using FTIR, has been compared with PAS on similar samples. The two methods agree perfectly during isothermal annealing at 150 °C, but at 250 °C the 1.8 μm absorption band disappears after annealing for 60 min, whereas positron lifetime and trapping rate remain constant, and annealing to 500 °C is required to remove the divacancy response. Since divacancies are not mobile at 150 °C their annealing can be ascribed to recombination with mobile interstitials. The discrepancy observed during annealing at 250 °C is suggested to be a consequence of some sort of divacancy agglomeration.