Positron annihilation studies of defects in 3C-SiC hot-implanted with nitrogen and aluminum ions

Monoenergetic positron beams were used to study defects introduced in cubic silicon carbide (3C-SiC) by implantation of 200 keV-N-2(+) and Al+ at temperatures from room temperature (RT) to 1200 degrees C at doses of 10(13) and 10(15)/cm(2). It is found from Doppler broadening spectra of annihilation gamma-rays obtained by varying the incident positron energy that hot-implantation gives rise to clustering of vacancies, whereas it suppresses amorphization and diminishes the thickness of damaged layers. The average size of such clusters increases with increasing implantation dose and temperature. Vacancy clustering by hot-implantation can be interpreted by the combination of vacancies during implantation. Vacancy type defects in the low-dose (10(13)/cm(2)) implanted samples are found to be removed by annealing at 1400 degrees C, whereas large vacancy clusters still remain after 1400 degrees C annealing in the high-dose (10(15)/cm(2)) implanted samples. It is also derived from the depth profile of positron diffusion length that positron scattering centers are produced after annealing at 1400 degrees C in all implanted samples.