Abstract. One dimensional nanostructures, like nanowires and nanotubes, are increasingly being researched for the development of next generation devices like logic gates, transistors, and solar cells. In particular, semiconducting nanowires with a nonsymmetric wurtzitic crystal structure, such as zinc oxide (ZnO) and gallium nitride (GaN), have drawn immense research interests due to their electromechanical coupling. The designing of the future nanowire-based devices requires component-level characterization of individual nanowires. In this paper, we present a unique experimental set-up to characterize the mechanical and electromechanical behaviour of individual nanowires. Using this set-up and complementary atomistic simulations, mechanical properties of ZnO nanowires and electromechanical properties of GaN nanowires were investigated. In ZnO nanowires, elastic modulus was found to depend on nanowire diameter decreasing from 190 GPa to 140 GPa as the wire diameter increased from 5 nm to 80 nm. Inconsistent failure mechanisms were observed in ZnO nanowires. Experiments revealed a brittle fracture, whereas simulations using a pairwise potential predicted a phase transformation prior to failure. This inconsistency is addressed in detail from an experimental as well as computational perspective. Lastly, in addition to mechanical properties, preliminary results on the electromechanical properties of gallium nitride nanowires are also reported. Initial investigations reveal that the piezoresistive and piezoelectric behaviour of nanowires is different from bulk gallium nitride.
In situ testing of nanostructuresSemiconducting nanowires (NWs) are potential building blocks for future electronic devices like logic circuits, transistors, and solar cells. NWs made of materials like zinc oxide (ZnO) and gallium nitride (GaN) are interesting for the research community due to their piezoelectric behaviour, offered by the non-symmetric wurtzite crystal structure. For example, ZnO NWs has been conceptually shown to generate electrical output when mechanically deformed [1][2][3]. To optimize the potential performance of piezoelectric NW-based devices, characterization of individual NWs at the component level is crucial. In this paper, a microelectromechanical system (MEMS)-based a e-mail : espinosa@northwestern.edu, b Currently an associate professor in the