Effect of the density of collision cascades on ion implantation damage in ZnO

We study structural disorder in ZnO bombarded at room temperature with 1.3 keV∕amu atomic P and cluster PFn (n=2 and 4) ions. Rutherford backscattering/channeling spectrometry results show that the density of collision cascades has a negligible effect on the damage buildup in the crystal bulk in the dose range resulting in ∼1.5−15 displacements per atom. Hence, the amount of stable post-implantation disorder in the bulk can be predicted based on ballistic calculations. In contrast, the cascade density affects radiation damage in the near-surface region. An intermediate defect peak between the expected surface and bulk peaks of disorder forms for ion irradiation conditions with dense cascades.