| 1. |
- Blomqvist, Mats, et al.
(författare)
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Electro-optic effect in ferroelectric Na0.5K0.5NbO3 thin films on oxide substrates
- 2006
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Ingår i: Integrated Ferroelectrics. - : Informa UK Limited. - 1058-4587 .- 1607-8489. ; 80:1, s. 97-106
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Tidskriftsartikel (refereegranskat)abstract
- We have deposited Na0.5NbO3 (NKN) films oil single crystal Al2O3(1 (1) under bar 02) and SrTiO3(001) substrates using rf-magnetron sputtering of a stoichiometric, high-density ceramic target. Using x-ray diffraction it was confirmed that NKN grows preferentially c-axis oriented on sapphire substrate and epitaxially oil the perovskite SrTiO3(001) substrate. Electro-optical (EO) properties were measured in visible light through a transverse method. With an applied dc field up to 20 kV/cm, the effective linear EO response was determined to r(eff) = 28 pm/V for NKN/Al2O3 and r(eff) = I I pm/V for NKN/SrTiO3, where a superlinear dependence was observed.
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| 2. |
- Blomqvist, Mats, et al.
(författare)
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Visible and IR light waveguiding in ferroelectric Na0.5K0.5NbO3 thin films
- 2005
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Ingår i: Integrated Ferroelectrics. - : Informa UK Limited. - 1058-4587 .- 1607-8489. ; 69, s. 277-286
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Tidskriftsartikel (refereegranskat)abstract
- High-quality ferroelectric thin films are attractive materials for integrated optics applications including electro-optic waveguide modulators and frequency doubling secondharmonic generators. Several fefroelectric thin film materials, such as BaTiO3, KNbO3, LiNbO3, and (Pb,La)(ZrTi)O-3, have been investigated regarding their optical and waveguiding properties. Recently the first results on waveguiding in ferroelectric Na0.5K0.5NbO3 (NKN) thin films were presented. Perovskite NKN films have previously been investigated as electrically tunable material for low loss rf and microwave applications. Na0.5K0.5NbO3 thin films of thickness 0.5-1.0 mum have been deposited on Nd:YAlO3(001) and Al2O3(0112) substrates using rf-magnetron sputtering of a stoichiometric, high-density ceramic target. X-ray diffraction measurements confirmed films grown highly (00l) oriented on the perovskite Nd:YAlO3 substrate and preferentially c-axis oriented on the single crystal r-cut sapphire substrate. Optical and waveguiding properties were characterized using a Metricon 2010 prism-coupling apparatus with a rutile prism. Dark-line spectra were obtained at visible light (lambda = 632.8 nm) as well as at infrared optical communication wavelengths, lambda = 1319 nm and lambda = 1549 nm, in both transverse electric (TE) and transverse magnetic (TM) polarizations. Sharp dips corresponding to waveguide propagation modes in the thin film layers where observed for both substrates. The calculated refractive index values and corresponding birefringence (Deltan = n(TM) - n(TE) = n(e) - n(o)) as a function of wavelength has been compared. Generally a larger birefringence is observed for the NKN film on Nd:YAlO3, which is in agreement with the larger degree of preferential c-axis orientation measured by XRD.
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| 3. |
- Chen, Kai, et al.
(författare)
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Self-Assembled Core-Shell Polymer Dielectric Prepared by Solution Casting Process
- 2009
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Ingår i: Integrated Ferroelectrics. - : Taylor andamp; Francis: STM, Behavioural Science and Public Health Titles. - 1058-4587 .- 1607-8489. ; 113, s. 1-8
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Tidskriftsartikel (refereegranskat)abstract
- Giant permittivity at 1 MHz, which slightly changes with temperatures, is observed in a polymer composite. The dielectric spectroscopy demonstrates that the samples are electrically heterogeneous. The microstructure observation and the ingredient analysis evidence they self assemble the conducting cores surrounded by the insulating shells. The giant-dielectric phenomenon is therefore attributed to the percolation effect. The electrically heterogeneous microstructure with effective permittivity values about 10 000 can be fabricated by a simple solution casting process in air. The composite is an attractive option to the currently used printing dielectric and the future flexible electronics.
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| 4. |
- Khan, U., et al.
(författare)
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Ferroelectric thin-film based two-dimensional electromagnetic bandgap structures
- 2006
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Ingår i: Integrated Ferroelectrics. - : Informa UK Limited. - 1058-4587 .- 1607-8489. ; 86:1, s. 67-76
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Tidskriftsartikel (refereegranskat)abstract
- A two-dimensional electromagnetic bandgap structure has been developed using ferroelectric thin-films. Using lumped inductors and parallel plate capacitors a planar structure is developed which creates a bandgap in the 20-40 GHz range, as demonstrated by experimental results. The ferroelectric material Ba0.6Sr0.4TiO3 (BST) is used in the form of a thin-film between patterned layers of gold to form capacitors on a 500 m thick high-resistivity Si substrate. A meander line based design is used to form the two-dimensional surface which provides biasing pathways to the varactors. The concept is simulated and experimentally verified using a coplanar waveguide based device in which the EBG surface is used as the ground plane. Designs are also presented for the development of a biasing network to take advantage of the non-linear tunability of the BST dielectric constant in order to make the surface tunable. Experiments used both sputtered and PLD BST films with a maximum bandgap depth of 35 dB. Potential applications are in the area of frequency selective surfaces, and high-impedance ground planes.
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| 5. |
- Khartsev, Sergiy, et al.
(författare)
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Heteroepitaxial Na0.5K0.5NbO3/La0.5Sr0.5CoO3 electro-optical cell
- 2006
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Ingår i: Integrated Ferroelectrics. - : Informa UK Limited. - 1058-4587 .- 1607-8489. ; 80, s. 133-143
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Tidskriftsartikel (refereegranskat)abstract
- We report electro-optic performance of heteroepitaxial Na0.5K0.5NbO3(1.5 mu m)/La0.5Sr0.5CoO3 (0.5 mu m) (NKN/LSCO) films grown on Al2O3(01 (1) under bar2) single crystal (r-cut sapphire) by rf-magnetron sputtering (NKN) and pulsed laser deposition (LSCO) techniques. Vertical capacitive electro-optical cells were defined by a thermal evaporation of 2 x 8 mm(2) Au electrodes through the contact mask on top the NKN film. Processing parameters have been specially optimized to obtain electrosoftNKN films with a non-linear fatigue-free P-E characteristics: low remnant P-r = 7.7 mu C/cm(2) high induced polarization P = 23 mu C/cm(2) @ 400 km/cm , and the coercive field E-c = 70 kV/cm. Electro-optical characterization of NKN films has been performed using waveguide refractometry: a prism coupling of a light beam into the thin-film waveguide modes. Intensity of TM- and TE-polarized light of 655 nm laser diode reflected from the free surface of NKN film and Au-clad NKN/LSCO waveguide was recorded at zero and 15 V (100 kV/cm) bias electric field. Fitting reflectivity spectra to Fresnel formulas yields extraordinary and ordinary refractive indices n(c) = 2.232 and n(o) = 2.234 as well as electro-optic coefficient r(13) = 17.4 pm/V. Dispersion of the refraction index follows Sellmeier formula n(2) = 1+ 3.46/[1 + (244 nm/lambda)(2)] in the range from 400 nm to 850 nm.
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| 6. |
- Kim, Joo-Hyung, et al.
(författare)
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Microfabrication of epitaxial La1-x(Sr,Ca)(x)MnO3 IR bolometer on Si
- 2006
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Ingår i: Integrated Ferroelectrics. - : Informa UK Limited. - 1058-4587 .- 1607-8489. ; 80, s. 47-54
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Tidskriftsartikel (refereegranskat)abstract
- Self supported free standing heteroepitaxial La1-x(Sr,Ca)(x)MnO3 (LSCMO) membranes grown on Bi4Ti3O12(BTO)/CeO2/YSZ buffered Si substrates have been microfabricated by Ar ion beam etching (IBE) and SF6/C4F8 inductively Coupled plasma (ICP) etching technique. The electrical property of free standing membrane was compared to as-grown sample by four point measurement. These results demonstrate feasibility to use heteroepitaxial oxide film structures with conventional photoresist patterning as thermally isolated membranes for infrared microbolometers.
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| 7. |
- Kim, Jang-Yong, et al.
(författare)
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AgTa0.5Nb0.5O3 thin film coplanar waveguide microwave capacitors
- 2005
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Ingår i: Integrated Ferroelectrics. - : Informa UK Limited. - 1058-4587 .- 1607-8489. ; 77, s. 13-20
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Tidskriftsartikel (refereegranskat)abstract
- 400 nm thick AgTa0.5Nb0.5O3 (ATN) films have been prepared by pulsed laser depositiontechnique on LaAlO3 (001) and sapphire (Al2O3-0112, r -cut) single crystal substrates.Comprehensive X-ray diffraction analysis showed epitaxial quality of ATN/LaAlO3films and preferentially (001) orientation of ATN/Al2O3 films. Voltage tunable microwavecapacitors were fabricated by lift-off technique on the surface of ferroelectricfilms. Microwave on-wafer tests were performed in the range from 1 to 40 GHz. Frequencydispersion is about 4.3%, voltage tunability is 4.7% @ 20 GHz and 200 kV/cm,loss tangent ∼0.068 @ 20 GHz, K-factor=tunability/tanδ is ranged from 124% @10 GHz to 35% @ 40 GHz.
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| 8. |
- Qiu, X. Y., et al.
(författare)
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Phase separation enhanced interfacial reactions in complex high-k dielectric films
- 2006
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Ingår i: Integrated Ferroelectrics. - : Taylor andamp; Francis: STM, Behavioural Science and Public Health Titles. - 1058-4587 .- 1607-8489. ; 86:1, s. 13-19
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Tidskriftsartikel (refereegranskat)abstract
- Amorphous CaZrOx, ZrAlxSiyOz and HfAlOx complex high-k dielectric films are deposited by pulsed laser deposition, and their microstructural characteristics and interfacial reactions between deposited films and Si substrates during high temperature annealing processes are investigated by X-ray photoelectron spectroscopy and high-resolution transmission electron microscopy. An essential finding is that nano-scale phase separation appears to be a common phenomenon for these amorphous films. The nonstoichiometric ZrOx or HfOx clusters precipitating from the amorphous matrix either react with silicon on the interface to form silicate or silicide interfacial layer, or nucleate and grow into nanosized crystals embedded in the outer layer of the dielectric films, which degrades the electrical performances of films.
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| 9. |
- Zhang, Zhigang, et al.
(författare)
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Characterization of piezoelectric shear mode inkjet actuator
- 2005
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Ingår i: Integrated Ferroelectrics. - : Informa UK Limited. - 1058-4587 .- 1607-8489. ; 69, s. 401-
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Tidskriftsartikel (refereegranskat)abstract
- Impedance analysis was used to characterize the properties of Piezoelectric Shear Mode Inkjet Actuators. Ceramic actuators poled parallel to the channel walls exhibit good performance. Applying high voltage the actuators can be depolarized at high temperature or even re-poled perpendicular to the channel walls. This limits the drive pulse and the bias voltage below the coercive voltage. The leakage current also has been studied with various conditions. For the ferroelectric ceramic materials, the Schottky barrier also can be measured at definite voltage and temperature ranges, the corresponding Barrier for the Al/PZT contact is 0.98 eV. A pronounced low-temperature dielectric relaxation process was observed between 100-150 K; the relaxation rate fellows the Arrhenius law, the fitted activation energy is 0.194 eV. The resonance frequency increases as decreasing the temperature because of increasing for the stiffness coefficient at low temperature.
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