Microstructure of the nitrogen pair in crystalline silicon studied by ion channeling

The structure of the nitrogen pair in crystalline silicon has been studied by the channeling technique and by infrared absorption spectroscopy. Silicon crystals have been implanted with ${}_{}{}^{15}{}_{}{}^{}\mathrm{N}$ at room temperature and have subsequently been annealed at 725 °C to form pairs. The channeling measurements have been carried out at 136 K using the nuclear reaction ${}_{}{}^{15}{}_{}{}^{}\mathrm{N}$(p,α${)}^{12}$C to probe the ${}_{}{}^{15}{}_{}{}^{}\mathrm{N}$ atoms, and the angular distribution of the α particle yield has been measured around all major crystal axes and planes. The major part of the implanted nitrogen atoms (70%) is found to occupy a unique type of site which is displaced by 1.1 Å from a perfect lattice site along a 〈100〉 direction. The population of this type of site has the same annealing properties as the local vibrational modes associated with the nitrogen pair in silicon. The experimental findings are consistent with a recently suggested model of the nitrogen pair.