Chemical Uniformity in Ferroelectric K_xNa_1−xNbO₃ Thin Films

Abstract

Potassium sodium niobate (KNN) has long been considered a viable candidate for replacing lead‐based materials in piezo‐ and ferroelectric devices. The introduction of KNN on an industrial scale is highly awaited; however, processing challenges still remain to be solved. The main obstacle is lack of reproducible growth of uniform boules or thin films at temperatures that facilitate monolithic device integration. Herein, atomic layer deposition (ALD) of KNN thin films, exhibiting high chemical uniformity over large areas, is reported. The cation composition can be controlled at a 1% level, enabling fine‐tuning of the film stoichiometry across the morphotropic phase boundaries of the KNbO3–NaNbO3 solid solution. The films are obtained as highly oriented on Pt (111)||Si (100)‐substrates after annealing at temperatures as low as 550 °C. They exhibit converse piezoelectric effects with magnitudes in accordance with literature. It is believed that the successful development of the described ALD process represents a major step toward achieving lead‐free piezo‐ and ferroelectrics on an industrial scale.

Nanoscale Li, Na, and K ion-conducting polyphosphazenes by atomic layer deposition

“…This could be possible through super cycles of processes for the alkali oxides/oxynitrides/ nitrides/phosphates. Sønsteby et al 46,47 have demonstrated a mixed KNbO 3 -NaNbO 3 using KO t Bu and NaO t Bu as precursors. It was found that the K : Na ratio was tunable to 1% by substituting in NaO t Bu for KO t Bu in the KNbO 3 process.…”

Influence of 120 MeV Au Ion Irradiation on Phase Transition, Surface, and Optical Properties of Lead‐Free (K,Na)NbO3 Films

“…The material possesses distinct properties in the form of films as compared to their bulk form owing to the altered lattice strain, structural defects, surface area, etc. [26][27][28] Several advanced synthesis techniques, such as RF magnetron sputtering, [29] pulsed laser deposition, [11] chemical vapor deposition, [30] atomic layer deposition, [31] etc., have been used to fabricate the KNN thin films. However, RF magnetron sputtering has been widely used over other deposition techniques because of its high-quality films, uniformity, dense, and large-area deposition.…”

Avoiding water reservoir effects in ALD of functional complex alkali oxides by using O3 as the oxygen source

“…16 ALD processes for Na-and K-containing compounds were reported in 2014, and have since been expanded to include KNN and KTN, among others. [17][18][19][20][21] The large majority of these processes utilize alkali metal tert-butoxides (e.g. NaO t Bu or KO t Bu, (Fig.…”