Formation of pores in thin germanium films under implantation by Ge$^{+}$ ions

The results of a study of the morphology of the nanostructured by ion implantation germanium films are presented. The film samples were grown using the magnetron sputtering method in an ultrahigh vacuum and then were irradiated with Ge$^{+}$ ions of 40 keV energy in the fluence range of (1.8–8) $\times$ 10$^{16}$ ion/cm$^2$. Using the scanning electron microscopy it was found that in the implanted germanium volume the vacancy complexes with a diameter of 50–150 nm gradually form and come to the surface upon reaching a certain implantation fluence, forming a developed relief of the irradiated films.