Waqar, M., Chai, J., Wong, L. M., Lim, P. C., Chen, S., Liew, W. H., Wang, S., Chen, J., He, Q., Yao, K., & Wang, J. (2023). Large Electromechanical Response in a Polycrystalline Alkali-Deficient (K,Na)NbO3 Thin Film on Silicon. Nano Letters, 23(23), 11026–11033. https://doi.org/10.1021/acs.nanolett.3c03302
Abstract:
The demand for large electromechanical performance in lead-free polycrystalline piezoelectric thin films is driven by the need for compact, high-performance micro-electromechanical systems (MEMS) devices operating at low voltages. Here we significantly enhance the electromechanical response in a polycrystalline lead-free oxide thin film by utilizing lattice-defect-induced structural inhomogeneities. Unlike prior observations in mismatched epitaxial films with limited low-frequency enhancements, we achieve large electromechanical strain in a polycrystalline (K,Na)NbO3 film integrated on silicon. This is achieved by inducing self-assembled Nb-rich planar faults with a non-stoichiometric composition. The film exhibits an effective piezoelectric coefficient of 565 pm V-1 at 1 kHz, surpassing lead-based counterparts. Notably, lattice defect growth is substrate-independent, and the large electromechanical response is extended to even higher frequencies in polycrystalline film. Improved properties arise from unique lattice defect morphology and frequency-dependent relaxation behavior, offering a new route to remarkable electromechanical response in polycrystalline thin films.
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Funding Info:
This research / project is supported by the Agency for Science, Technology and Research - RIE2020 AME Individual Research Grant (IRG)
Grant Reference no. : A20E5c0086
This research / project is supported by the Agency for Science, Technology and Research - AME Programmatic Fund
Grant Reference no. : A20G9b0135