Lithography guided horizontal growth of silicon nanowires for the fabrication of ultrasensitive piezoresistive strain gauges

We present a fabrication process to obtain ultrasensitive piezoresistive strain gauges that exploit the exceptional mechanical and piezoresistive properties of silicon nanowires grown via the vapour-liquid-solid mechanism. The process allows the implementation of nanowire-based strain gauges in micro and nanoelectromechanical systems, which is demonstrated here for piezoresistive cantilever sensors. The main feature of this process is that it allows the location of a nanowire array only at one side of the neutral axis of the mechanically active area of the device. This is a crucial requirement to achieve that only tensile or compressive stresses occur in the array, so that a detectable change in resistance is produced. Atomic force microscopy characterization of the sensitivity of the obtained devices validates the fabrication process. (C) 2009 Elsevier B.V. All rights reserved.