Experimental studies of complex crater formation under cluster implantation of solids

The results of a systematic study of surface defect formation after energetic Ar_n⁺ (n = 12, 22, 32, 54) and Xe_n⁺ (n = 4, 16) cluster ion implantation into silicon and sapphire are presented. Implantation energies vary from 3 to 18 keV/ion. Two cases of comparative studies are carried out: the same cluster species are implanted into two different substrates, i.e. Ar_n⁺ cluster ions into silicon and sapphire and two different cluster species Ar_n⁺ and Xe_n⁺ are implanted into the same kind of substrate (silicon). Atomic force, scanning electron and transmission electron microscopies (AFM, SEM and TEM) are used to study the implanted samples. The analysis reveals the formation of two types of surface erosion defects: simple and complex (with centrally positioned hillock) craters. It is found that the ratio of simple to complex crater formation as well as the hillock dimensions depend strongly on the cluster species, size and impact energy as well as on the type of substrate material. Qualitative models describing the two comparative cases of cluster implantation, the case of different cluster species and the case of different substrate materials, are proposed.