Seminarium Fizyki Ciała Stałego

The miniaturization of devices is a rapidly developing field of science and engineering. Particularly, piezoelectric materials are promising for applications such as mechanical energy harvesting systems and self-powered sensors, as they enable reversible conversion between mechanical and electrical energy1. Zinc oxide (ZnO) nanowires are especially attractive due to their high piezoelectric coefficient2, non-toxicity, chemical stability, biocompatibility and cost-effective production. The piezoelectric properties of a single ZnO nanowire mounted on both sides were investigated using a dual transmission electron microscopy (TEM) approach under bias: quantitative mapping of the bending and twisting was performed on a FEI Titan Cubed 80-300 (at Institute of Physics PAS) while off-axis electron holography experiments were carried out on a I2TEM microscope and analysed with qHolo software (at CEMES-CNRS)3. Transfer and electrical contacting of nanowires onto biasing chips were performed using a focused ion beam. The inverse piezoelectric effect, namely length extension due to an external electric field, was examined using a non-conventional 4D-STEM methodology. Based on analyses of the zero-order Laue zone position in diffraction patterns, bending maps were calculated in 3D direct space. Due to current flow, the thermal expansion component was found to be significant, as predicted by Finite Element Method simulations carried out in COMSOL Multiphysics. Considering both thermal expansion and inverse piezoelectric effect as origin of bending, we concluded that local piezoelectric effect may occur. Off-axis electron holography, a powerful technique for probing electrostatic potentials and charge distributions4, was used to investigate the electric response of the nanowire under applied voltage. The measured electron phase ramp in the vicinity of the bent nanowire indicated increasing charge accumulation with increasing bias. Moreover, experimental results confirmed the dual nature of the deformation cause: arising from both the thermal effects and inverse piezoelectric. 1 N. Buatip et al. ACS Appl. Nano Mater, 7, 15798−15807 (2024)2 V. Consonni et al. Nano Energy, 83, 105789 (2021)3 C. Gatel et al. qHolo v1.2 a plug-in for Digital Micrograph (Gatan Inc.), (2024). https://www.hremresearch.com/qholo.4 L. Zhang, et al. Advanced Materials, 37, 2413691(2025)Acknowledgments: National Science Center (NCN) OPUS No. 2019/35/B/ST5/03434