Fabrication and characterization of freestanding Si/Cr micro- and nanospirals

We report on the scrolling of two-layer Si/Cr hybrid films on Si(001) wafers to form rolled-up micro-and nanostructures. Mesa stripes with width ranging from 3.0 mu m to 60 nm have been used to fabricate the spirals. Decreasing the width gradually changes the scrolling direction of the Si/Cr stripe from the (100) direction to the longitudinal axis of the stripe. Moreover, the diameter of the Si/Cr rings decreases significantly with decreasing stripe width, which can be explained by edge effects at the side walls of the bilayer film. Based on this effect, freestanding Si/Cr spiral nanobelts can be fabricated. The flexibility of such spirals has been probed with a nano-manipulator showing their excellent shape-memory properties. (c) 2006 Elsevier B.V. All rights reserved.