Waqar Moaz, Chai Jianwei, Wong Lai Mun, Lim Poh Chong, Chen Shuting, Liew Weng Heng, Wang Shijie, Chen Jingsheng, He Qian, Yao Kui, Wang John
Institute of Materials Research and Engineering (IMRE), A*STAR (Agency for Science, Technology and Research), Singapore 138634, Singapore.
Department of Materials Science and Engineering, National University of Singapore, Singapore 117574, Singapore.
Nano Lett. 2023 Dec 13;23(23):11026-11033. doi: 10.1021/acs.nanolett.3c03302. Epub 2023 Nov 27.
The demand for large electromechanical performance in lead-free polycrystalline piezoelectric thin films is driven by the need for compact, high-performance microelectromechanical systems (MEMS) based 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)NbO film integrated on silicon. This is achieved by inducing self-assembled Nb-rich planar faults with a nonstoichiometric composition. The film exhibits an effective piezoelectric coefficient of 565 pm V at 1 kHz, surpassing those of lead-based counterparts. Notably, lattice defect growth is substrate-independent, and the large electromechanical response is extended to even higher frequencies in a 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.
对基于紧凑、高性能微机电系统（MEMS）且在低电压下运行的器件的需求，推动了对无铅多晶压电薄膜大机电性能的需求。在此，我们通过利用晶格缺陷诱导的结构不均匀性，显著增强了多晶无铅氧化物薄膜中的机电响应。与在低频增强有限的失配外延薄膜中的先前观察结果不同，我们在集成于硅上的多晶（K，Na）NbO薄膜中实现了大的机电应变。这是通过引入具有非化学计量组成的自组装富Nb平面缺陷来实现的。该薄膜在1 kHz时表现出565 pm V的有效压电系数，超过了铅基同类材料。值得注意的是，晶格缺陷的生长与衬底无关，并且在多晶薄膜中，大的机电响应甚至扩展到了更高频率。独特的晶格缺陷形态和频率相关的弛豫行为带来了性能的提升，为多晶薄膜中显著的机电响应提供了一条新途径。
