Structural and electrical study of highly (100)-oriented KNN films fabricated by a sol-gel non-alkoxide process

Fabricating of highly-oriented pure-phase potassium sodium niobate (KNN) films on traditional Si substrates by low-cost manageable sol-gel technique (especially with non-alcohol niobium salt Nb 2 O 5 as niobium source) is still a work of great challenge. Here, KNN films were prepared on Pt/Ti/SiO 2 /Si and LNO/Si substrates via a sol-gel non-alkoxide process. And a comprehensive set of experimental investigations to the role of the bottom electrode, annealing atmosphere and the number of coating layers on the microstructures and electrical properties involution of spin-coated KNN films were made. The crystal structures, preferential orientation and morphology of KNN films are strongly affected by the annealing atmosphere, as well as the bottom electrode material. KNN films annealed in air show an obviously better crystal structure and denser surface than that annealed in oxygen, and KNN film spin-coated on LNO bottom electrode and annealed in air exhibits a dominant ( h 00) orientation with a high preferred degree of 93.6%. In addition, it also can be found that the increasing number of coating layers of KNN films also results in better crystalline structures (higher oriented degree, larger grains, narrower FWHM) and electrical performance. KNN film with 18 layers shows the largest dielectric constant of 868 and the lowest loss tangent of 2.8%.