Horizontal Si nanowire arrays as building blocks for nanoelectromechanical systems

San Paulo, Alvaro1; Arellano, Noel2; Plaza, Jose A.1; He, Rongrui2; Carraro, Carlo2; Maboudian, Roya2; Howe, Roger T.2; Bokor, Jeffrey2; Yang,, Peidong2 1Spain; 2United States

Well-ordered and size-controlled nanowire arrays are interesting structures not only because they can allow the implementation of novel nanoelectronic and nanoelectromechanical systems that exploit the unique properties of individual nanowires, but also because arrays by themselves can show basic properties different from that of bulk macroscopic materials. Semiconductor nanowire growth based on the vapor-liquid-solid (VLS) mechanism is one of the most promising bottom-up fabrication alternatives explored so far for nanowire-based applications, as it provides self-assembled growth of a large number of single crystal nanowires with high structural quality and precise control over many of their properties. When grown horizontally between the sidewalls of Si prefabricated microtrenches, Si nanowires bridge the opposing sidewalls forming mechanically stable and electrically continuous double clamped nanobeams. In this contribution, we present the fabrication and characterization of mechanical structures composed of horizontally suspended, well-oriented and size-controlled Si nanowire arrays. These structures are made of double clamped nanowires assembled in multiple arrays consecutively linked by transversal microspacers. These unique beam-like mechanical structures are used to investigate the mechanical behaviour of the arrays by atomic force microscopy and finite element simulations. Experimental evidence and theoretical description of important differences in the mechanical elasticity of the mechanical structures composed of nanowire arrays with respect to equivalent bulk material structures are provided. It is found that multiple nanowire arrays consecutively linked behave like a set of linear springs connected in series instead of an elastic beam as it could have been predicted by analogy with a microcantilever beam. The agreement between the experimental results and finite element simulations of the fabricated structures validates our conclusions. Our results demonstrate the feasibility of integrating nanowire arrays in a new generation of nanoelectronic and nanoelectromechanical systems, such as surrounding gate horizontal nanowire array FETs, ultrasensitive piezoresistive transducers or high surface-to-volume ratio microcantilever sensor platforms.

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