Piezoresistivity and structural twin defects of anisotropic ZnO nanocrystals: An in situ electromechanical push-to-pull study and site specific FIB preparation for TEM.Friday (09.06.2017) 11:00 - 11:20 Förde II Part of:
Quasi 1D ZnO structures are very important candidates for piezotronic, piezoresistive and energy harvesting applications. However, for most of them a detailed understanding about the electromechanical response of these nanowires interconnected with a precise knowledge about its crystal structure, defects and interfaces is inevitable. Here, the piezoresistive properties of ultralong Q1D ZnO nano- and microwires as function of true strain is studied in detail via in situ electromechanical measurements inside SEM on specially selected ZnO nanowires integrated into a MEMS fabricated electrical push-to-pull (E-PTP) device. The electromechanical change in two individual ZnO nanowires is characterized by a decrease in resistivity under pure tensile strain of 4.25% and 4.34% is calculated to be in the order of 14.2% and 13.9% with reproducible Gauge factors of -3.26 and -3.32, respectively. The piezoresistive behavior is further elucidated by applying a rectangular potential under constant strain.
Additionally, with the pursuit of defect characterization in the TEM we present a route for site specific specimen preparation of Q1D ZnO nanocrystals using the geometric shadow FIB method  with help of a carbon gas injection system. Thin cross-sections of ZnO nanospikes show twin boundaries of type [2-1-10]/(01-13) and [2-1-10]/(01-11) as structural features. This preparation technique is applicable for all anisotropic and fragile nanostructures and offers new possibilities for detailed TEM experiments.