Silver Nanoparticles in Porous Germanium

Recent experiments on fabrication of nanoporous Si and Ge layers with Ag nanoparticles by low-energy high-dose ionimplantation are discussed. Ag+-ion implantation of single-crystal c-Si and c-Ge at low-energy (E = 30 keV) highdoses (D = 1.25·1015 - 1.5·1017 ion/cm2) and current density (J = 2-15 μA/cm2) was carried out for this purpose. Thechanges of Si and Ge surface morphology after ion implantation were studied by scanning electron and atom-forcemicroscopy. The near surface area of samples was also analyzed by diffraction of the backscattered electrons and energydispersive X-ray microanalysis. Amorphization of near-surface layer was observed at the lowest implantation dosesof c-Si. Ag nanoparticles were synthesized and uniformly distributed over the near Si surface when the threshold doseof 3.1·1015 ion/cm2 exceeded. At a dose of more than 1017 ion/cm2, the formation of a surface nanoporous PSi structurewas detected. Ag nanoparticle size distribution function became bimodal and the largest particles were localized alongSi-pore walls. In the case of Ge substrates, as a result of the implantation on the c-Ge surface, a porous amorphousPGe layer of a spongy structure was formed consisting of a network of intersecting Ge nanowires with an averagediameter of ~ 10-20 nm. At the ends of the nanowires, the synthesis of Ag nanoparticles was observed. It was found thatthe formation of pores during Ag+-ion implantation was accompanied by efficient spattering of the Si and Ge surface.Thus, ion implantation is suggested to be used for the formation of nanoporous semiconductor thin layers for industry,which could be easily combined with the crystalline matrix for various applications.