He and O ion implantation induced defects in Si crystal studied using slow positron annihilation spectroscopy

摘要

Open volume defect profiles have been obtained in He, O and (He + O) ion implanted silicon crystal 1 0 0 using slow positron beam measurements. The p-type Si samples have been implanted with He (30 keV), O (120 keV) and both the ions [He (30 keV) + O(120 key)] with the dose of 1 x 10(15) and 1 x 10(17) ions/cm(2). The average range of these ions in Si is estimated similar to 280 nm. The depth dependent defect profiles have also been studied after isochronal annealing (100-900 degrees C) of the ion implanted Si crystals. On annealing at temperatures ( 500 degrees 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 degrees C. In the case of O and (He + O) 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 x 10(15) ions/cm(2)) and annealed at 700 and 900 degrees C. In case of O implanted (1 x 10(17)ions/cm(2)) and co-implanted samples (1 x 10(15)ions/cm(2) and 1 x 10(17)ions/cm(2)) annealed at 700 and 900 degrees C, formation of oxygen decorated cavities is proposed.