Orientation control of KNbO₃ thin films deposited by laser ablation on MgO (100) using SrTiO₃ transition layers

Abstract

Epitaxial thin films of KNbO₃ were deposited on MgO (100) single crystal substrates using pulsed laser ablation, with a SrTiO₃ transition layer in between. Their stoichiometry was controlled by repeated cycles of alternate pulsing of KNbO₃ and KNO₃ targets. The SrTiO₃ transition layers were used to control the orientation of the KNbO₃ film. Using two different deposition temperatures, SrTiO₃ films were grown with two different growth planes, namely, (110) and (100). For (100) oriented SrTiO₃ films, the orientation relationship between various layers was (110) or (001) KNbO₃ // (100) SrTiO₃ // (100) MgO. For (110) oriented SrTiO₃ films, the orientation relationships were (020) or (200) KNbO₃ // (110) SrTiO₃ // (100) MgO. Measurement of the capacitance of the KNbO₃ frlms during heating revealed a transition from the orthorhombic to tetragonal phase near 235±2 °C and tetragonal to cubic phase near 430±2 °C.