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Optical waveguiding in magnetron-sputtered Na0.5K0.5NbO3 thin films on sapphire substrates
KTH, Tidigare Institutioner                               , Mikroelektronik och informationsteknik, IMIT.
KTH, Tidigare Institutioner                               , Mikroelektronik och informationsteknik, IMIT.ORCID-id: 0000-0001-8774-9302
KTH, Tidigare Institutioner                               , Mikroelektronik och informationsteknik, IMIT.
Inst. of Thin Films and Interfaces, Section: Ion Technology, Forschungszentrum Jülich.
Vise andre og tillknytning
2003 (engelsk)Inngår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 82, nr 3, s. 439-441Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Preferentially oriented perovskite-structured Na0.5K0.5NbO3 (NKN) thin films have been deposited on hexagonal Al2O3(01 (1) under bar2) substrates using rf magnetron sputtering of a stoichiometric, high-density, ceramic target. Structural and film surface properties were measured using x-ray diffraction and atomic force microscopy, respectively. Optical and waveguiding properties were characterized using a prism-coupling technique. We observed sharp and distinguishable TM and TE propagation modes and measured the refractive index of NKN thin films of different thicknesses. The ordinary and extraordinary refractive indices were calculated to be n(o)=2.247+/-0.002 and n(e)=2.216+/-0.002 for a 2.0-mum-thick film at 632.8 nm. This implies a birefringence Deltan=n(e)-n(o)=-0.031+/-0.002 in the film. These first results show the potential use of rf-sputtered NKN films as an electro-optical active material.

sted, utgiver, år, opplag, sider
2003. Vol. 82, nr 3, s. 439-441
Emneord [en]
electrooptic characterization
HSV kategori
Identifikatorer
URN: urn:nbn:se:kth:diva-22184DOI: 10.1063/1.1539295ISI: 000180449100043OAI: oai:DiVA.org:kth-22184DiVA, id: diva2:340882
Merknad
QC 20100525Tilgjengelig fra: 2010-08-10 Laget: 2010-08-10 Sist oppdatert: 2017-12-12bibliografisk kontrollert
Inngår i avhandling
1. Electro-Optical Na0.5K0.5NbO3 Films
Åpne denne publikasjonen i ny fane eller vindu >>Electro-Optical Na0.5K0.5NbO3 Films
2005 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
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.

sted, utgiver, år, opplag, sider
Stockholm: KTH, 2005. s. xii, 91
Serie
Trita-FYS, ISSN 0280-316X ; 5299
Emneord
Functional materials, ferroelectrics, sodium potassium niobates, thin films, rf-magnetron sputtering, waveguiding, refractive index, prism-coupling, electro-optic effects, dielectric tunability, Funktionella material
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-193 (URN)91-7178-007-6 (ISBN)
Disputas
2005-05-20, D1, KTH, Lindstedtsvägen 17, 2tr, Stockholm, 10:00
Opponent
Veileder
Merknad
QC 20100928Tilgjengelig fra: 2005-05-12 Laget: 2005-05-12 Sist oppdatert: 2010-09-28bibliografisk kontrollert

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