Density of displacement cascades for cluster ions: An algorithm of calculation and the influence on damage formation in ZnO and GaN

A method of statistical calculation of parameters of averaged individual collision cascades formed by cluster ions composed of a small number of atoms is suggested. The results of calculations are compared with experimental data on the accumulation of structural damage in ZnO and GaN irradiated with PFn ions (n = 0, 2, 4) with the specific energy of 1.3 keV/amu at room temperature. It is shown that, for ZnO, the density of the displacement cascade does not affect the concentration of stable postimplantation defects in the region of the bulk peak, but significantly affects this concentration in the near-surface region. For GaN, as the displacement-cascade density increases, both an increase in the concentration of stable defects in the region of the bulk maximum of the defect concentration and an increase in the thickness of the surface's amorphous layer are observed.