Piezoelectric properties of (K,Na)NbO3 films deposited by RF magnetron sputtering

High-piezoelectricity lead-free films of (K,Na)NbO3 (KNN) were successfully deposited on Pt/MgO and Pt/Ti/SiO2/Si substrates by RF magnetron sputtering. The KNN film was epitaxially grown on Pt/MgO with a high < 001 > orientation in the pseudo-cubic perovskite structure. The KNN film on Pt/Ti/SiO2/Si was polycrystalline with a preferential < 001 > orientation in the pseudo-cubic perovskite structure. The piezoelectric properties of the KNN films were determined from the tip displacement of KNN/Pt/MgO or KNN/Pt/Ti/SiO2/Si unimorph cantilevers. The transverse piezoelectric coefficients e(31)* (d(31)/s(11)(E)) of the KNN films on Pt/MgO and Pt/Ti/SiO2/Si were calculated to be -3.6 and -5.5 C/m(2), respectively, which are amongst the highest values for KNN films ever reported. (c) 2008 The Japan Society of Applied Physics.