The Ferroelectric Properties of (Na_0.5K_0.5)NbO₃Thin Films Fabricated by rf-Magnetron Sputtering

Abstract

Fatigue-free Na 0.5 K 0.5 NbO 3 (NKN) thin films were grown on Pt/Ti/SiO 2 /Si substrates by the radio frequency magnetron sputtering method. The addition of enriched Na 2 CO 3 and K 2 CO 3 into the NKN ceramic target was necessary in order to compensate for a deficiency in the Na and K concentrations in the film. The remnant polarization (2P r) and the coercive field (2E c) of the NKN films annealed at 600°C were 32.2 μ C/cm 2 and 90 kV/cm at an applied field of 200 kV/cm, respectively. A leakage current density was obtained around 7.3×10−8 A/cm 2 at 150 kV/cm. The film showed fatigue-free characteristics under a ± 5 V bipolar square pulse of 1 MHz for up to 1.0×10 10 cycles. The NKN film prepared by radio frequency magnetron sputtering is an attractive alternative for applications involving nonvolatile ferroelectric random access memory (FRAM) devices. Keywords: (Na,K)NbO3 thin filmferroelectricityFRAM Acknowledgments This work was supported by the University of Ulsan Research Fund of 2005. Paper originally presented at IMF-11, Iguassu Falls, Brazil, September 5–9, 2005