Formation of porous germanium layers by silver-ion implantation

We propose a method for the formation of porous germanium ($P$-Ge) layers containing silver nanoparticles by means of high-dose implantation of low-energy Ag$^+$ ions into single-crystalline germanium ($c$-Ge). This is demonstrated by implantation of 30-keV Ag$^+$ ions into a polished $c$-Ge plate to a dose of 1.5 $\times$ 10$^{17}$ ion/cm$^2$ at an ion beam-current density of 5 $\mu$A/cm$^2$. Examination by high-resolution scanning electron microscopy (SEM), atomic-force microscopy (AFM), X-ray diffraction (XRD), energy-dispersive X-ray (EDX) microanalysis, and reflection high-energy electron diffraction (RHEED) showed that the implantation of silver ions into $c$-Ge surface led to the formation of a $P$-Ge layer with spongy structure comprising a network of interwoven nanofibers with an average diameter of $\sim$10–20 nm Ag nanoparticles on the ends of fibers. It is also established that the formation of pores during Ag$^+$ ion implantation is accompanied by effective sputtering of the Ge surface.