Ion implantation: nanoporous germanium

The formation of thin surface amorphous layers of nanoporous Ge with various morphology during low-energy high-dose implantation by metal ions of different masses ⁶³Cu⁺, ¹⁰⁸Ag⁺ and ²⁰⁹Bi⁺ of monocrystalline c-Ge substrates were experimentally demonstrated by high-resolution scanning electron microscopy. Analysis of the crystallographic structure of all nanoporous germanium layers obtained was carried out by reflected backscattering electron diffraction. It was shown that at low irradiation energies, in the case of ⁶³Cu⁺ and ¹⁰⁸Ag⁺, needle-shaped nanoformations were created on the c-Ge surface, constituting a nanoporous Ge layer, while when using ²⁰⁹Bi⁺, the implanted layer consists of densely packed nanowires. At high energies, the morphology of thin surface layers of nanoporous germanium changes with an increase in the mass of the implanted ions from three-dimensional network to spongy with separate discharged interlacing nanowires. General possible mechanisms of pore formation in Ge during low-energy high-dose ion implantation, such as cluster-vacancy, local thermal microexplosion, and point heating accompanied by melting, are discussed.