Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms | 2019
He and O ion implantation induced defects in Si crystal studied using slow positron annihilation spectroscopy
Abstract Open volume defect profiles have been obtained in He, O and (He\u202f+\u202fO) ion implanted silicon crystal 〈1\u202f0\u202f0〉 using slow positron beam measurements. The p-type Si samples have been implanted with He (30\u202fkeV), O (120\u202fkeV) and both the ions [He (30\u202fkeV)\u202f+\u202fO(120\u202fkeV)] with the dose of 1\u202f×\u202f1015 and 1\u202f×\u202f1017\u202fions/cm2. The average range of these ions in Si is estimated ∼280\u202fnm. The depth dependent defect profiles have also been studied after isochronal annealing (100–900\u202f°C) of the ion implanted Si crystals. On annealing at temperatures (>500\u202f°C), an increase (decrease) in S-parameter was observed in the He (O) ion implanted samples. The variations observed in the S-E profiles indicate that large size open volume defects are created in He irradiated Si followed by annealing at 700\u202f°C. In the case of O and (He\u202f+\u202fO) implanted samples, variations in S-E and W-E profiles indicate the formation of oxygen-vacancy clusters, a buried silicon oxide layer or oxygen decorated cavities. The S-E (W-E) profiles have been fitted using a program ‘Variable Energy Positron fit’ to evaluate the characteristic S- and W- parameter values of different regions. It is observed through S-W correlation plots that He ions as well as vacancy defects diffuse out of the silicon crystal at higher annealing temperatures. Oxygen-vacancy cluster defects are identified in O implanted (1\u202f×\u202f1015\u202fions/cm2) and annealed at 700 and 900\u202f°C. In case of O implanted (1\u202f×\u202f1017\u202fions/cm2) and co-implanted samples (1\u202f×\u202f1015\u202fions/cm2 and 1\u202f×\u202f1017\u202fions/cm2) annealed at 700 and 900\u202f°C, formation of oxygen decorated cavities is proposed.