Ion Implantation and Synthesis of Materials - Studium

7.9 Damage Distribution from SRIM 897.9 Damage Distribution from SRIMInformation about irradiation damage can also be obtained from the Monte Carlosimulations in SRIM. In these simulations the ion track of the implanted ion andall the resulting recoils and atomic displacements are displayed, as shown inFig. 7.6, for a 40 keV Sb ion in Si. Figure 7.6 shows the path of the Sb ion andmajor Si recoils (dashed line) and Si displacements. As can be seen, thedisplacement population extends well beyond the Sb ion track. Each implanted Sbion produces over 1,000 Si displacements.With continued ion implantation, a dense structure of displaced atoms isformed. Figure 7.7 shows the atomic density of displaced Si atoms as a function ofdepth, normalized to the ion dose, which will be formed per incident Sb ion. Thisdata represents the averaging of 5,000 ion histories. Note that the unit of length forthe Y axis is angstroms, and the number of displaced Si atoms is give in units ofnumber per unit volume per ion dose, (Si atoms cm −3 )/(Sb ions cm −2 ). This datacan be used to determine the fraction of displaced atoms at a given depth for agiven ion dose. For example, the peak value of the displacement curve, whichoccurs at approximately 180 Å, has a value of 40 × 10 8 displaced Siatoms ion −1 cm −1 . For an Sb ion dose of 1 × 10 13 ions cm −2 , this corresponds to4 × 10 22 displaced Si atoms cm −3 . Dividing this value by the atomic density of Si(5 × 10 22 cm −3 ) gives the fraction of displaced Si atoms as 0.80.For comparison, Fig. 7.8 shows the range distribution of implanted Sb ions inSi. This data also represents the averaging of 5,000 ion histories. The range profileshows a peak concentration at about 285 Å, approximately 100 Å deeper than thedamage peak.0100 200 300 400Target Depth (Angstrom)500Fig. 7.6. Ion track for 40 keV Sb in Si showing Si recoils and Si displacements (MonteCarlo SRIM simulation)