Ion Implantation and Synthesis of Materials - Studium

10.3 Ion Beam-Induced Enhanced Crystallization 137Regrowth rate (A/min) °120100806040010001011101111110010100111101001200010 20 30 40 50 60 70 80 90(degrees)Fig. 10.9. Regrowth rate versus orientation of the Si substrate for implanted amorphous Siannealed at 550°C (Csepregi et al. 1978)The regrowth rate is also strongly dependent on the orientation of the Si substrate(Csepregi et al. 1978). Figure 10.9 shows regrowth velocities on single-crystalsubstrates at different orientations. Samples with the 〈111〉 direction perpendicularto the surface have the slowest growth rate, while 〈100〉 samples have the fastest.This orientation dependence has been explained (Spaepen and Turnbull 1982) bycrystallization proceeding along ledges on the densely packed {111} interfacialplanes. The growth velocity is maximized when the crystallographic planescontaining the ledges are perpendicular to the surface. It decreases when theledges are inclined to the surface.10.3 Ion Beam-Induced Enhanced CrystallizationStudies on ion beam-induced epitaxial crystallization are performed by heating apre-existing amorphous layer (α-layer) that is interfaced to a single-crystalsubstrate at a fixed temperature and by irradiating it with ion beams at low currentdensities in order to avoid further heating. Here we follow the description given byRimini (1995). The ion energies are chosen such that the projected range of theirradiating ions is well beyond the original c–α interface. This allows one todiscriminate between damage clustering, which is typically produced at the end ofthe ion’s range, and effects due to the interaction of point defects created by theion with an α-layer. Under such conditions a large enhancement in the crysta-llization kinetics is observed. It is possible to regrow the crystalline phase at