Ultra flexible SiGe/Si/Cr nanosprings

The electrical and mechanical properties of Si/SiGe rolled-up nanosprings have been investigated. Micromanipulation has been employed to investigate the mechanical properties. For nanosprings under investigation, a linear dependence between applied force and extention is found until the spring is extended to 91% of its original length, moreover, the springs could be reproducibly extended to more than 180% of their original length. An extremely small spring constant of 0.003 N/m has been determined, which is an order of magnitude smaller than that of the most flexible available atomic force microscope (AFM) cantilever (∼10^-2 N/m). Thus, it is expected that these springs can be used as ultra-sensitive force sensors. A simple estimation assuming an imaging resolution of approximately 1 nm is adopted for displacement measurement and reveals that using a nanospring fabricated from a 300 nm wide mesa as a visual-based force sensor, a resolution of 3 pN/nm can be provided. The conductivity of nanospirals was analysed and current densities up to 530 kA/cm² were measured. Structures with metallic wires on top of the mesa structures were successfully employed to activate mechanical movements of the structure.