Disorder production and amorphisation in ion implanted silicon

Measurements of the depth profiles of disorder and the depth integrated disorder produced in Si at 40 K or 300 K by low energy (15 keV-60 keV) ions of a range of masses from the light (N+ and P+), intermediate (Ar+ and As+) to heavy (In+, Sb+, As+ 2, Bi and Sb+ 2) were made using Rutherford scattering-dechannelling techniques. Studies of both the ‘surface peak’ disorder and the dechannelling minimum indicate a gradual change in the process of disorder production from one of point defect generation for light projectiles to direct impact amorphisation for heavy projectiles. In the lower mass ion cases it is concluded that amorphisation is produced by overlap of more lightly disordered regions and it is shown how all the data can be encompassed within a generalized model of amorphousness production which occurs when local defect densities lie in the range 2–18%.