Single-crystalline Ag2Te nanorods prepared by room temperature sputtering of GeTe

We report a facile, single-crystalline Ag2Te nanorod formation based on electrochemical diffusion of Ag. The nanorods were grown non-epitaxially by sputtering deposition of GeTe on Ag2Te nanoparticles at room temperature. For the nanorod growth, the source of the Ag supply is not deposition but the diffusion of Ag from the nanoparticles. The growth of the single-crystalline Ag2Te nanorods required GeTe deposition onto Ag2Te nanoparticles, in contrast to the growth of amorphous Ag2Te nanorods caused by Te deposition onto Ag nanoparticles and the growth of other nanostructures caused by GeTe deposition on Ag nanoparticles. The GeTe deposition onto the Ag2Te nanoparticles of an amount equivalent to a 100-nm-thick film produced nanorods of a length ranging from 3 to 5 μm and a diameter ranging from 100 to 400 nm. We propose a model for the nanorod growth based on solid-state electrochemical reaction between GeTe and movable Ag ions, inducing nanoscale phase separation and precipitation of amorphous Ge. We suggest that the nanorod structure with a crystalline Ag2Te core and an amorphous Ge shell is useful for thermoelectric applications.