New method of porous Ge layer fabrication: structure and optical properties

Porous germanium films were produced by selective removal of the GeO$_2$ matrix from the GeO$_2\langle$Ge–NCs$\rangle$ heterolayer in deionized water or HF. On the basis of Raman and infrared spectroscopy data it was supposed that a stable skeletal framework from agglomerated Ge nanoparticles (amorphous or crystalline) was formed after the selective etching of GeO$_2\langle$Ge–NCs$\rangle$ heterolayers. The kinetics of air oxidation of amorphous porous Ge layers was investigated by scanning ellipsometry. Spectral ellipsometry allowed estimating the porosity of amorphous and crystalline porous Ge layers, which was $\sim$70 and $\sim$80%, respectively.