1.5 MeV Kr+ irradiation of polycrystalline Ge

This paper reports 1.5 MeV Kr+ irradiation of polycrystalline Ge at room temperature, and subsequent annealing carried out with in situ TEM observations. After a Kr+ dose of 1.2 x 1014 ions/cm2, Ge in the electron transparent region was completely amorphized. Continuous irradiation of the amorphized Ge resulted in a high density of small cavities. These cavities, first observed after 7 x 1014 ions/cm2 with an average diameter of ∼3 nm, grew into large (∼50 nm) irregular-shaped holes, transforming the irradiated Ge into a sponge-like material after 8.5 x 1015 ions/cm2. The crystallization temperature and the morphology of the crystallized Ge after annealing were found to be dependent on the Kr+ dose. The sponge-like structure was retained after crystallization at ∼600 degrees C