NKN Films Research Articles

(Na,K)NbO 3 Thin Films Using Metal-Organic Chemical Vapor Deposition

Ferroelectric (Na,K)NbO 3 (NKN) thin films have been synthesized using metalorganic chemical vapor deposition (MOCVD) technique for the first time. The films were deposited on various substrates in a horizontal hot-wall reactor using tetramethyl-heptanedionate (THD) precursors. Epitaxial films have been prepared on SrTiO 3 (001) substrates, while nearly perfect [001]-axis oriented polycrystalline thin films have been deposited on SiO 2 /Si, SiN x /Si, and sapphire substrates. Electron Spectroscopy for Chemical Analysis (ESCA) analysis indicated that Na, K, Nb, and O are the primary elements present in the film. Dielectric spectroscopy for NKN films on SiO 2 /Si substrates showed dielectric permittivity l ' about 140 and loss tan i less than 2 % in the frequency range from 1 kHz to 120 kHz.

(Na,K)NbO 3 Thin Films Using Metal-Organic Chemical Vapor Deposition

Ferroelectric (Na,K)NbO 3 (NKN) thin films have been synthesized using metalorganic chemical vapor deposition (MOCVD) technique for the first time. The films were deposited on various substrates in a horizontal hot-wall reactor using tetramethyl-heptanedionate (THD) precursors. Epitaxial films have been prepared on SrTiO 3 (001) substrates, while nearly perfect [001]-axis oriented polycrystalline thin films have been deposited on SiO 2 /Si, SiN x /Si, and sapphire substrates. Electron Spectroscopy for Chemical Analysis (ESCA) analysis indicated that Na, K, Nb, and O are the primary elements present in the film. Dielectric spectroscopy for NKN films on SiO 2 /Si substrates showed dielectric permittivity l ' about 140 and loss tan i less than 2 % in the frequency range from 1 kHz to 120 kHz.

RF-Magnetron Sputtered Au/(Na,K)NbO3/SiO2/Si MFIS-diode Structures

AbstractRecently we proposed ferroelectric sodium potassium niobate (Na0.5K0.5NbO3, NKN) thin films to be a candidate for applications in nonvolatile memories and electrically tunable devices [1-5]. In this paper we report on processing and characterization of metal-ferroelectric-insulatorsemiconductor (MFIS) diode structures based on RF-magnetron sputtered NKN films. 0.7 μm thick NKN films have been deposited at 650 °C on the thermally grown 47 nm thick SiO2 layer on Si(001) wafers. Stoichiometric Na0.5K0.5NbO3 ceramic target was sputtered in an O2-Ar atmosphere with a total pressure of 5 mTorr. Grown films were analyzed as deposited as well as after an oxygen annealing at 600 °C for 30 minutes. The NKN films exhibit a strong (001) preferential orientation, which was appreciably improved after the oxygen annealing. A leakage current density of 2.3 nA/cm2 at an electric field of 400 kV/cm, and a memory window of 7.2 V was measured for Au/NKN/SiO2(47nm)/Si(001) diode structures at the programmable voltage of 40 V. I-V measurements were performed in the time domain to distinguish between the relaxation of polarization, “true” leakage current, and the degradation of the resistance in ferroelectric NKN film.

Preparation of Na0.5K0.5NbO3/La0.6Sr0.2Mn1.2O3/LaAlO3 Thin Film Structures by Pulsed Laser Deposition

AbstractWe report on ferroelectric/giant magnetoresistive Na0.5K0.5NbO3/La0.6Sr0.2Mn1.2O3 (NKN/LSMO) heterostructures grown onto LaAlO3 (001) single crystal using KrF pulsed laser ablation of stoichiometric ceramic target. Main processing parameters have been optimized to obtain smooth LSMO template layer, avoid NKN-LSMO interdiffusion, preserve NKN stoichiometry against the lost of volatile potassium and sodium and achieve reasonable reliability of NKN film performance. X-ray diffraction θ- 2θ scans and rocking curves evidence for single-phase content and high c-axis orientation both in template LSMO and top NKN layers. Ferroelectric measurements yield remnant polarization Pr of 1.5 [C/cm2 and spontaneous polarization Ps of 7 μC/cm2 at electric field strength of 130 kV/cm. At room temperature, dielectric permittivity ε′ and dissipation factor tan δ have been found to vary from 595 to 555 and 0.046 to 0.029 respectively in the frequency range of 0.4 to 20 kHz. At 10 kHz dielectric permittivity linearly increases from 410 to 650 in the temperature range 77 K to 415 K while the dissipation factor below 320 K does not exceed 3%.