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Rf-magnetron sputtered ferroelectric (Na,K)NbO3 films
KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.ORCID iD: 0000-0001-8774-9302
KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
2002 (English)In: Proceedings of the 13th IEEE International Symposium on Applications of Ferroelectronics / [ed] White, G.; Tsurumi, T., 2002, 195-198 p.Conference paper, Published paper (Refereed)
Abstract [en]

Sodium potassium niobate (Na,K)NbO3 (NKN) thin films were grown by rf-magnetron sputtering from stoichiometric Na0.5K0.5NbO3 target on LaAlO3 (LAO) single crystals and polycrystalline Pt80Ir20 (PtIr) substrates. NKN films on polycrystalline PtIr substrates were found to be preferentially (004 oriented while XRD measurements reveal epitaxial quality of NKN/LaAlO3 film structures. The ferroelectric state in NKN/PtIr films at room temperature is indicated by polarization loops with polarization as high as 33.4 muC/cm(2) at 700 kV/crn, remnant polarization of 9.9 muC/cm(2), and coercive field of 91 kV/cm. I-V characteristics of vertical Au/NKN/PtIr capacitive cells and planar Au/NKN/LAO interdigital capacitors (IDCs) showed very good insulating properties. For NKN IDC the leakage current density was in the order of 30 nA/cm(2) at 400 kV/cm. Rf dielectric spectroscopy demonstrates low loss, low frequency dispersion, and high voltage tunability both for vertical Au/NKN/PtIr and planar interdigital Au/NKN/LAO capacitors.

Place, publisher, year, edition, pages
2002. 195-198 p.
Keyword [en]
Capacitors, Coercive force, Crystal orientation, Epitaxial growth, Insulation, Magnetron sputtering, Polycrystalline materials, Stoichiometry, Remnant polarization
National Category
Other Materials Engineering
Identifiers
URN: urn:nbn:se:kth:diva-5097DOI: 10.1109/ISAF.2002.1195903ISI: 000183375500048ISBN: 0-7803-7414-2 (print)OAI: oai:DiVA.org:kth-5097DiVA: diva2:7859
Note
QC 20100928Available from: 2005-05-12 Created: 2005-05-12 Last updated: 2010-09-28Bibliographically approved
In thesis
1. Electro-Optical Na0.5K0.5NbO3 Films
Open this publication in new window or tab >>Electro-Optical Na0.5K0.5NbO3 Films
2005 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

Ferroelectric oxides are a group of advanced electronic materials with a wide variety of properties useful in applications such as memory devices, resonators and filters, infrared sensors, microelectromechanical systems, and optical waveguides and modulators.

Among the oxide perovskite-structured ferroelectric thin film materials, sodium potassium niobate or Na0.5K0.5NbO3 (NKN) has recently emerged as one of the most promising materials in radio frequency (rf) and microwave applications due to high dielectric tenability and low dielectric loss.

This thesis presents results on growth and structural, optical, and electrical characterization of NKN thin films. The films were deposited by rf-magnetron sputtering of a stoichiometric, high density, ceramic Na0.5K0.5NbO3 target onto single crystal LaAlO3 (LAO), Al2O3 (sapphire), SrTiO3, and Nd:YAlO3, and polycrystalline Pt80Ir20 substrates. By x-ray diffractometry, NKN films on c-axis oriented LaAlO3, SrTiO3 and Nd:YAlO3 substrates were found to grow epitaxially, whereas films on r-cut sapphire and polycrystalline Pt80Ir20 substrates were found to be preferentially (00l) oriented. The surface morphology was explored using atomic force microscopy.

Optical and waveguiding properties of the Na0.5K0.5NbO3/substrate heterostructures were characterized using prism-coupling technique. Sharp and distinguishable transverse magnetic and electric propagation modes were observed for NKN thicknesses up to 2.0 μm. The extraordinary and ordinary refractive indices were calculated together with the birefringence of the NKN material. The electro-optic effect in transverse geometry was measured in transmission, where the effective linear electro-optic response was determined to reff = 28 pm/V for NKN/Al2O3 with an applied dc field up to 18 kV/cm.

The ferroelectric state in NKN films on Pt80Ir20 at room temperature was indicated by a polarization loop with saturated polarization as high as 33.4 μC/cm2 at 700 kV/cm, remnant polarization of 10 μC/cm2, and coercive field of 90 kV/cm. Current-voltage characteristics of vertical Au/NKN/PtIr capacitive cells and planar Au/NKN/LAO interdigital capacitors (IDCs) showed very good insulating properties, with the leakage current density for an NKN IDC on the order of 30 nA/cm2 at 400 kV/cm. Rf dielectric spectroscopy demonstrated low loss, low frequency dispersion, and high voltage tunability. At 1 MHz, NKN/LAO showed a dissipation factor tan δ = 0.010 and a tunability of 16.5 % at 200 kV/cm. For the same structure the frequency dispersion was Δεr = 8.5 % between 1 kHz and 1 MHz.

Place, publisher, year, edition, pages
Stockholm: KTH, 2005. xii, 91 p.
Series
Trita-FYS, ISSN 0280-316X ; 5299
Keyword
Functional materials, ferroelectrics, sodium potassium niobates, thin films, rf-magnetron sputtering, waveguiding, refractive index, prism-coupling, electro-optic effects, dielectric tunability, Funktionella material
National Category
Other Materials Engineering
Identifiers
urn:nbn:se:kth:diva-193 (URN)91-7178-007-6 (ISBN)
Public defence
2005-05-20, D1, KTH, Lindstedtsvägen 17, 2tr, Stockholm, 10:00
Opponent
Supervisors
Note
QC 20100928Available from: 2005-05-12 Created: 2005-05-12 Last updated: 2010-09-28Bibliographically approved

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