Ta nanotubes grown by glancing angle deposition

Regular arrays of vertical 200-nm-diameter hollow Ta tubes were grown by glancing angle deposition (GLAD) onto Cr nanoring patterns that were fabricated by positive-resist e-beam lithography followed by nondirectional Cr deposition and a lift-off process. During GLAD, nanorods nucleate around the edges of the patterned rings, broaden, and merge to form tubes with 50-nm-thick walls. The nanotubes remain open during continued growth, with a slight (13%) decrease in the effective inner diameter for an increasing tube height from 200 to 600 nm. These results demonstrate that complex patterned two-dimensional shapes can be extended into the third dimension using the GLAD process. (C) 2008 American Vacuum Society.