Fabrication of Lead-Free Piezoelectric (K, Na)NbO3 Thin Film on Nickel-Based Electrodes

It is desirable to replace noble metals used as electrode materials for piezoelectric thin film with base metals. A nickel-based layer is proposed as a bottom electrode for potassium (K) sodium (Na) niobate (NbO
₃
) (KNN) piezoelectric thin film. Pure nickel is used as a bottom electrode under the KNN layer, and nickel silicide is used as an uncovered bottom electrode to gain access to the electrode placed under the KNN. The obtained results do not indicate the oxidation of the nickel-based bottom electrode after the deposition of KNN at 600 °C for 10 h in the presence of oxygen and/or after annealing the sample at 400 °C for an hour in air. The dielectric constant was determined to be 280 at 1 kHz. The remnant polarization was estimated to be 12.5 μC/cm
²
. The effective piezoelectric coefficient d
₃₃
was estimated to be 37 pm/V at 100 kV/cm. The effective coefficient d
₃₁
was evaluated by measuring the tip deflection of KNN unimorph cantilevers to be 17.2 pm/V. The relatively lower values of the piezoelectric properties of the fabricated KNN/Ni/Ti/SiO
₂
/Si can be attributed to the crystal orientation of the KNN layer, which was preferentially oriented in the (110) direction.