Fabrication of Ge nanoneedles by ion-irradiation method

The Ge surfaces irradiated by Ar⁺ ions at 600eV 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 60-80nm in diameter and 100-300nm 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.