Epitaxial growth of lead-free (K,Na)NbO3 (KNN) thin films on (001)SrRuO3/Pt/ZrO2/Si substrates was achieved by using RF magnetron sputtering. X-ray diffraction measurements revealed that lattice constants (a1 = 0.3987 nm, a2 = 0.3959 nm, a3 = 0.4011 nm) of epitaxial KNN thin films with a pseudo cubic system were close to KNN single crystals. Vertical piezoelectric force microscopy observation indicated that the spontaneous polarization Ps with a downward direction was dominant, and the epitaxial KNN thin films were naturally polarized. The epitaxial KNN thin films exhibited low relative dielectric constant (εr ∼ 267). In addition, piezoelectric coefficients |e31,f| showed a constant value of about 6.5 C m−2 with the increase in applied positive voltages. Relatively high converse |e31,f| values were obtained at low applied voltages due to an intrinsic piezoelectric effect. Therefore, the epitaxial KNN thin films might enable piezoelectric microelectromechanical systems driven at low applied voltages.
Crystal structure and piezoelectric properties of lead-free epitaxial (K,Na)NbO3 thin films grown on Si substrates
Note: This paper is part of the APL Special Collection on Piezoelectric Thin Films for MEMS.
Kiyotaka Tanaka, Yoshiyuki Kawata, Sang Hyo Kweon, Goon Tan, Takeshi Yoshimura, Isaku Kanno; Crystal structure and piezoelectric properties of lead-free epitaxial (K,Na)NbO3 thin films grown on Si substrates. Appl. Phys. Lett. 24 October 2022; 121 (17): 172901. https://doi.org/10.1063/5.0110135
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