Fabrication of Ge nanoneedles by ion-irradiation method

The Ge surfaces irradiated by Ar+ ions at 600 eV with simultaneous Ni supply at room temperature were characterized by various kind of densely distributed nanostructures, such as tiny cones, nanorods with a bottlenecked and nanoneedles, depending on the Ni supply rate during Ar+ ion irradiation. As the Ni supply rate decreased, the width of nanostructure formed on the cone tip became thin, and finally slender Ge nanoneedles of 60–80 nm in diameter and 100–300 nm in length were realized. Because the simultaneously supplied Ni fulfills the prerequisite for the so-called “seed” which enhances the surface texturing, size of clustered Ni atoms during of Ar+ ion irradiation might affect the size of nanostructures formed after the prolonged sputtering.