Dual-Chirality Helical Nanobelts: Linear-to-Rotary Motion Converters for Three-Dimensional Microscopy

A linear-to-rotary motion converter is demonstrated using 3-D SiGe/Si dual-chirality helical nanobelts (DCHNBs). Analytical and experimental investigation shows that the motion conversion has excellent linearity for small deflections. The conversion ratios of displacement and load for a SiGe/Si DCHNB (an 8-nm-thick Si_0.6Ge_0.4 and a 10-nm-thick Si layer) are found to be 171.3deg/mum and 2.110 times 10^-6 Nmiddotm/N, respectively. The stiffness (0.033 N/m) is much smaller than that of bottom-up synthesized helical nanostructures, which is promising for high-resolution force measurement in nanoelectromechanical systems. To perform torque measurement, two atomic force microscope cantilevers are used for simultaneous characterization of axial and radial properties of the same nanostructure. An application related to 3-D imaging is shown in a scanning electron microscope. The ultracompact size makes it possible for DCHNBs to serve as rotary stages for creating 3-D scanning probe microscopes or microgoniometers.