Low-temperature solution processing route for potassium sodium niobate (KNN) thin films

Abstract

A major challenge for integration of functional oxides, such as ferroelectrics, into microelectronics and flexible electronics is the reduction of their processing temperature, which needs to be lower than the degradation temperature of silicon and flexible plastic substrates. Aiming that, attention has been given to low-temperature processing of oxide films by chemical solution deposition (CSD). In the field of ferroelectrics, potassium sodium niobate ((K1−xNax)NbO3, KNN) has aroused a special interest due to its eco-friendliness, despite the high crystallization temperature. In this work, polycrystalline KNN thin films have been fabricated for the first time at a temperature as low as 400 °C using a modified CSD process, the Seeded Photosensitive Precursor Method (SPPM). Despite this low processing temperature, monophasic and stoichiometric films with appreciable values of remnant polarization, Pr ∼ 10.8 μC/cm2, and hysteretic piezoresponse are obtained. These results open a window to the direct integration of KNN films into the high-performance electronic devices.