Physical Properties of (Na1-xKx)NbO3 Thin Film Grown at Low Temperature Using Two-Dimensional Ca2Nb3O10 Nanosheet Seed Layer

A monolayer Ca2Nb3O10 (CNO) nanosheet was deposited on a Pt/Ti/SiO2/Si substrate using the Langmuir-Blodgett method. This monolayer CNO nanosheet with a (001) surface termination was used as a seed layer to reduce the growth temperature of the crystalline (Na1-xKx)NbO3 (NKN) film. The crystalline NKN film was preferentially grown along the [001] direction at 400 degrees C. The ferroelectric and piezoelectric properties of this NKN film were influenced by the postannealing atmosphere due to the variations in the amounts of oxygen vacancies in the NKN film. The crystalline NKN film annealed at 300 degrees C under 50 Torr O-2 atmosphere showed promising ferroelectric and piezoelectric properties epsilon(r) of 303 and tan delta of 2.0% at 100 kHz, P-s of 15.3 mu C/cm(2), P-r of 11.7 mu C/cm(2), and E-c of 78 kV/cm, and d(33) of 139 pm/V. This NKN film showed the lowest leakage current, which can be explained by the Schottky emission mechanism. The Schottky barrier heights of the Pt/NKN and NKN/CNO/Pt interfaces were calculated to be 0.97 and 0.28 eV, respectively. The results of this work suggest a new method to grow crystalline thin films at low temperatures by using metal-oxide nanosheets as the seed layer.