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Sökning: WFRF:(Khartsev Sergiy) > (2005-2009)

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1.
  • Blomqvist, Mats, et al. (författare)
  • Electro-optic effect in ferroelectric Na0.5K0.5NbO3 thin films on oxide substrates
  • 2006
  • Ingår i: Integrated Ferroelectrics. - : Informa UK Limited. - 1058-4587 .- 1607-8489. ; 80:1, s. 97-106
  • 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)
  • Electrooptic ferroelectric Na0.5K0.5NbO3 films
  • 2005
  • Ingår i: IEEE Photonics Technology Letters. - : Institute of Electrical and Electronics Engineers (IEEE). - 1041-1135 .- 1941-0174. ; 17:8, s. 1638-1640
  • Tidskriftsartikel (refereegranskat)abstract
    • We report on waveguiding and electrooptic properties of epitaxial Na0.5K0.5NbO3 films grown by radio-frequency magnetron sputtering on Al2O3 (1102) single crystal substrates. High optical waveguiding performance has been demonstrated in infrared and visible light. The in-plane electrooptic effect has been recorded in transmission using a transverse geometry. At dc fields, the effective linear electrooptic coefficient was determined to 28 pm/V, which is promising for modulator applications.
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3.
  • Blomqvist, Mats, et al. (författare)
  • Visible and IR light waveguiding in ferroelectric Na0.5K0.5NbO3 thin films
  • 2005
  • Ingår i: Integrated Ferroelectrics. - : Informa UK Limited. - 1058-4587 .- 1607-8489. ; 69, s. 277-286
  • 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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4.
  • Bonetti, Stefano, et al. (författare)
  • Buried tantalate-niobate microwave varactors
  • 2007
  • Ingår i: 2006 15TH IEEE INTERNATIONAL SYMPOSIUM ON APPLICATIONS OF FERROELECTRICS. - 9781424413317 ; , s. 347-350
  • Konferensbidrag (refereegranskat)abstract
    • We present characteristics of microwave variable capacitors (varactors) buried in 2.5 mu m thick AgTa0.5Nb0.5O3 (ATN) film pulsed laser deposited on sapphire single crystal. 2 gm gap interdigital capacitors (IDC) were fabricated by photolithographic, dry etching and lift-off processes. For comparison, similar IDCs were also defined on top of ATN film. Capacitance and loss tangent have been determined using a modified de-embedding technique in the microwave range 25 MHz - 40 GHz. Buried structures show higher values of capacitance and tunability, keeping the same level of losses compared to standard topped devices and resulting in an increased K-factor = tunability/tan delta. Experimental results are explained within equivalent circuit model. Besides the increased performance, the new design avoids the need of a successive planarization step, which could be required in an integration process.
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5.
  • Emmoth, Birger, et al. (författare)
  • Fuel removal from bumper limiter tiles by using a pulsed excimer laser
  • 2005
  • Ingår i: Journal of Nuclear Materials. - : Elsevier BV. - 0022-3115 .- 1873-4820. ; 337-39:1-3, s. 639-643
  • Tidskriftsartikel (refereegranskat)abstract
    • Samples of a limiter tile from the TEXTOR tokamak were investigated by scanning electron microscopy and nuclear reaction analysis both before and after laser heating. SEM images showed spheres and thin flakes covering the surface which are the areas modified by plasma particles striking under grazing angles. Due to roughness of the surface there are shadowed regions between the 'flakes'. Laser pulses did not lead to expected common ablation of the surface. Features that looked like 'melting' of thin surface layers were rather observed. The initial deuterium content in the surface layer of tiles was of the order of 10(18) D atoms per cm(2). After the laser light impact the content decreased with 60-70%; by reducing the deposited power by a factor four, the deuterium content was decreased by 40-50%. We make the interpretation that we approach a threshold of the laser detritiation method in fusion devices.
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6.
  • Fors, R., et al. (författare)
  • Giant resistance switching in metal-insulator-manganite junctions : Evidence for Mott transition
  • 2005
  • Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 71:4
  • Tidskriftsartikel (refereegranskat)abstract
    • Heteroepitaxial CeO2(80 nm)/L0.67Ca0.33MnO3(400 nm) film structures have been pulsed laser deposited on LaAlO3(001) single crystals to fabricate two terminal resistance switching devices. Ag/CeO2/L0.67Ca0.33MnO3 junctions exhibit reproducible switching between a high resistance state (HRS) with insulating properties and a semiconducting or metallic low resistance state (LRS) with resistance ratios up to 10(5). Reversible electrical switching is a polar effect achievable both in continuous sweeping mode and in the pulse regime. Successive temperature crossover of electronic transport from the thermal activation of the deep levels (E-a=320 meV) at high temperatures to thermal activation of the shallow levels (E-a=40 meV) and finally at low temperatures to the regime of temperature independent resistance, usually associated with quantum tunneling, has been found for the insulating HRS. The temperature dependence of the LRS reveals a para-to-ferromagnetic phase transition in the L0.67Ca0.33MnO3 (LCMO) electrode at T-c=260 K and an anomaly at lower temperatures similar to200 K corresponding to the Curie temperature of the Mn4+ depleted part of the LCMO film. Current-voltage characteristics in the LRS are highly nonlinear, and show negative differential conductivity (NDC). We suggest that the reversible resistance switching ocurrs due to the electric field induced nucleation of filament-type conducting valence-shifted CeOx domains inside the insulating CeO2 matrix. The abrupt insulator-to-metal transition is the result of localization of 4f electronic states in Ce3+ ions and the subsequent appearance of hole conductivity in the oxygen p-bands. NDC at low temperatures is relied upon the interband scattering of CeOx carriers from a low energy, high mobility valley into a high energy valley with low mobility.
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7.
  • Fors, Rickard, et al. (författare)
  • Non-volatile giant resistance switching in metal-insulator-manganite junctions
  • 2005
  • Ingår i: Materials and Processes for Nonvolatile Memories. - WARRENDALE : MATERIALS RESEARCH SOCIETY. - 1558997784 ; , s. 379-384
  • Konferensbidrag (refereegranskat)abstract
    • Heteroepitaxial CeO2(80nm)/L0.67Ca0.33MnO3(400nm) film structures have been pulsed laser deposited on LaAlO3(001) single crystals to fabricate two terminal resistance switching devices. Ag/CeO2/L0.67Ca0.33MnO3 junctions exhibit reproducible switching between a high resistance state (FIRS) with insulating properties and a semiconducting or metallic low resistance state (LRS) with resistance ratios up to 10(5). Reversible electrical switching is a polar effect achievable both in continuous sweeping mode and in the pulse regime.
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8.
  • Grishin, Alexander, et al. (författare)
  • All-garnet magneto-optical photonic crystals
  • 2008
  • Ingår i: Journal of the Magnetics Society of Japan. - Japan. - 1882-2924. ; 32:2, s. 140-145
  • Tidskriftsartikel (refereegranskat)abstract
    • We survey the properties of all-garnet magneto-optical (MO) heteroepitaxial film structures grown by pulsed laser deposition and rf-magnetron sputtering. 1D MO-photonic crystals (MOPCs) were composed of /4 garnet layers alternating highly gyrotropic B13Fe5O12 (BIG) and MO-passive rare earth gallium garnets. As designed, MOPCs' spectra exhibit optical stop band with the transmittance central peak caused by light localization in /2 thick BIG cavity. The first all-garnet BIG/YIG MOPC showed 140% enhancement of the Faraday rotation (FR) compared to a single layer BIG film [APL 84, 1438 (2004)]. Further improvement of MO-performance has been achieved due to the replacement of optically dense YIG by transparent Gd- (GGG), Sm- and novel La-Ga-garnets [APL 86, 141108 (2005); 87, 122504 (2005); 90, 191113 (2007); JAP 101, 053906 (2007)]. At the resonance wavelengths 750 (980) nm, specific FR F=-20.5 (-7.3) deg/m and MO-quality factor Q = 2 |F| /absorption = 66 (43.6) deg represent the highest MOPC performance achieved so far. Respectively, this is 470 (810) % and 31 (190)% enhancement compared to a single layer BIG. MO-remanence (latching capability) has been engineered in the series of BIG:GGG(n:m) superlattices. Regular alternating of lattice mismatched garnet layers impedes the nucleation of misfit dislocations, preserves a long range coherent compressive strain through the whole multilayer thickness thus results in a strong uniaxial magnetic anisotropy. 2.5 m thick BIG:GGG(3:2) film at 678 nm shows FR=1.4 deg, transmittance 82%, 92% squareness of magnetization loop, saturation and coercive fields as low as 56 and 25 Oe, respectively. Nanostructured garnets were used to build MO-visualizer and current driven MO-display [APL 88, 242504 (2006)].
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9.
  • Grishin, Alexander M., et al. (författare)
  • 980 nm Bi3Fe5O12/Sm3Ga5O12 magneto-optical photonic crystal
  • 2007
  • Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 90:19
  • Tidskriftsartikel (refereegranskat)abstract
    • Heteroepitaxial all-garnet magneto-optical photonic crystal (MOPC) was fabricated to enhance Faraday rotation at 980 nm. MOPC was composed of alternating MO-active Bi3Fe5O12 and transparent Sm3Ga5O12 quarter-wavelength layers grown by rf-magnetron sputtering on Ca,Mg,Zr:Gd3Ga5O12(111) single crystal substrate. High MO performance at the resonance wavelength lambda=980 nm, specific Faraday rotation theta(F)=-7.3 degrees/mu m, absorption coefficient alpha=3350 cm(-1), and MO figure of merit Q=2 parallel to theta(F)parallel to/alpha=43.6 degrees demonstrates feasibility to use bismuth iron garnet MOPCs for application in pump laser diodes, optical amplifiers, modulators, and sensors.
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10.
  • Grishin, Alexander M., et al. (författare)
  • Highly luminescent garnets for magneto-optical photonic crystals
  • 2009
  • Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 95:10
  • Tidskriftsartikel (refereegranskat)abstract
    • We compare luminescent properties of several Er-doped garnets as building blocks in all-garnet heteroepitaxial magneto-optical photonic crystals. Pulsed laser deposited La3Ga5O12, Gd3Ga5O12, Y3Fe5O12, and rf-magnetron sputtered Bi3Fe5O12 were chosen to host Er3+ ions on dodecahedral lattice sites. Er substituents with the concentration of 0.5 at. % (0.1 garnet formula units) do not decrease giant Faraday rotation in Bi2.9Er0.1Fe5O12 garnet; meanwhile providing intense room temperature C-band photoluminescence (PL). Fe3+ ion works as a sensitizer for Er resulting in fivefold PL enhancement in iron garnets compared to gallium ones. PL lifetime in gallium garnets is in millisecond range reaching almost 6 ms in Gd2.9Er0.1Ga5O12. We conclude Er substitution in gallium and iron garnet layers used both as Bragg mirrors and microcavities promises magneto-optical photonic crystals to become an active lasing medium.
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11.
  • Grishin, Alexander M., et al. (författare)
  • Low field driven latching-type Bi3Fe5O12/Gd3Ga5O12 magneto-optical display
  • 2006
  • Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 88:24
  • Tidskriftsartikel (refereegranskat)abstract
    • Series of heteroepitaxial all-garnet magneto-optical (MO) Bi3Fe5O12n/Gd3Ga5O12m /BIG(n)/GGG(m), n= 1, 2, 3, 4, 5 and m=1 and 2 are the numbers of unit cells) nanostructured multilayers have been sintered by pulsed laser deposition technique. Processing parameters and structure of grown films have been optimized to obtain perpendicular magnetic anisotropy and square hysteresis loop with low coercive and saturation magnetic fields. Regular alternating of lattice mismatched BIG and GGG atomic layers inhibited nucleation of misfit dislocations; thus a long range coherent compressive strain was preserved through the whole thickness of BIG(n)/GGG(m) multilayer stack. 2.5 mu m thick BIG(3)/GGG(2) sample (1200 BIG and 800 GGG unit cells) at lambda= 678 nm shows MO Faraday rotation Phi(F)= +/- 1.4 degrees, transmittance of 82%, attenuation alpha=3400 dB/cm, squareness of magnetization loop (remnant-to-saturation magnetizations ratio) as high as 92%, and saturation and coercive fields as low as 56 and 25 Oe, respectively. MO remanence (latching capability) enables application of nanostructured garnet as a magnetic relief replicator/visualizer and as a material for low power consuming displays.
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12.
  • Grishin, Alexander M., et al. (författare)
  • Strong broad C-band room-temperature photoluminescence in amorphous Er2O3 film
  • 2006
  • Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 89:2
  • Tidskriftsartikel (refereegranskat)abstract
    • Photoluminescence with the bandwidth of 45 nm (1523-1568 nm at the level of 3 dB) was observed in amorphous Er2O3 films grown on quartz substrate by pulsed laser ablation of erbium oxide stoichiometric target. Optical transmission spectrum has been fitted to Swanepoel formula [J. Phys. E 16, 1214 (1983)] to determine dispersion of refractive index and to extract resonance absorption peaks at 980 and 1535 nm. The maximum gain coefficient as high as 800 dB/cm at 1535 nm was estimated using McCumber theory and experimental spectrum of the resonance absorption. For 5 mm long waveguide amplifier with erbium doping confinement factor of 0.1, the theory predicts the spectral gain of 18 dB with 1.2 dB peak-to-peak flatness in the bandwidth of 31 nm (1532-1563 nm) when 73% of Er3+ ions are excited from the ground state to the I-4(3/2) laser level. Strong broadband photoluminescence at room temperature and inherently flat spectral gain promise Er2O3 films for ultrashort high-gain optical waveguide amplifiers and integrated light circuits.
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13.
  • Jalali-Roudsar, Amir Abbas, et al. (författare)
  • Determination of magnetic anisotropy constants for magnetic garnet epitaxial films using ferromagnetic resonance
  • 2005
  • Ingår i: Journal of Magnetism and Magnetic Materials. - : Elsevier BV. - 0304-8853 .- 1873-4766. ; 288, s. 15-21
  • Tidskriftsartikel (refereegranskat)abstract
    • The constants of magnetocrystalline anisotropy K-l and uniaxial anisotropy K-u are determined precisely by using ferromagnetic resonance (FMR) and a fitting procedure oil a (1 1 1) yttrium iron garnet (YIG) film made by pulsed laser deposition (PLD) technique. By applying a magnetic field in the azimuthal orientation we introduce measurement in a geometry which yields the anisotropy constants with a high accuracy. The new technique is compared with the previous analysis employing characteristic plane measurements. The new geometry yields at least 15% better accuracy in determining constant K, than by the previous method with FMR.
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14.
  • Johansson, Petter, et al. (författare)
  • Comparison of Bi3Fe5O12 film giant Faraday rotators grown on (111) and (001) Gd3Ga5O12 single crystals
  • 2006
  • Ingår i: Thin Solid Films. - : Elsevier BV. - 0040-6090 .- 1879-2731. ; 515:2, s. 477-480
  • Tidskriftsartikel (refereegranskat)abstract
    • Bismuth iron garnet (Bi3Fe5O12, BIG) epitaxial thin films were grown on single crystal (Gd3Ga5O12, GGG) (111) and (001) substrates by rf-magnetron sputtering technique. Processing parameters have been optimized to obtain high deposition rate (2.74 mu m/h) and the surface rms roughness less than 10 nm. X-ray diffraction reveals films epitaxial quality: exclusive (111) or (00 1) orientation with narrow rocking curves and strong in-plane texture. Films possess low optical loss and magneto-optical Faraday rotation (FR) as high as 5 deg/mu m at 677 nm wavelength. Comparative analysis of films grown on (111) and (001) substrates clearly shows significant superiority of BIG/GGG(001) film. For this film, the coercive field similar to 100 Oe appears to be 2.5 times lower while the optical transmission to be 10% higher than that for BIG/GGG(111) film. Enhanced magneto-optical performance of BIG/GGG(001) films relies upon better accommodation of the film-to-substrate mismatch strain through the tetragonal BIG lattice distortions compared to the rhombohedral one in BIG/GGG(111) films.
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15.
  • Kawasaki, Hiroharu, et al. (författare)
  • TiO2/TiN/TiO2 heat mirrors by laser ablation of single TiN target
  • 2008
  • Ingår i: Journal of Physics, Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 100:1, s. 012038-
  • Tidskriftsartikel (refereegranskat)abstract
    • Titanium oxide (TiO2 ) and titanium nitride (TiN) multilayered films grown by pulsed laser deposition (PLD) technique have been tested as a heat mirror, which have a high transmittance in the visible region and a high reflectance in the infrared. Three layer TiO2 /TiN/TiO2 heat mirrors were grown on Corning glass substrates ablating single TiN target. Switching of TiO2 -to-TiN layers composition was achieved by changing gas atmosphere (oxygen-to-nitrogen). Grown TiO2 /TiN/TiO2 heat mirrors are highly transparent in visible (above 60% at 525nm), opaque in infrared (10% at 2600nm) and in the range from 400 nm to 2600 nm they possess almost the same properties as films prepared using two targets: TiO2 and TiN. XPS confirms similarity of chemical composition of multilayered TiO2 /TiN films prepared by single TiN and two TiO2 and TiN targets techniques. Furthermore, multifunctional self cleaning properties of TiO2 /TiN heat mirrors are expected through the precise control of the composition of the top TiO2 layer operating as a photocatalyst.
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16.
  • Khartsev, Sergiy, et al. (författare)
  • Bi3Fe5O12/Gd3Ga5O12 (m) magneto-optical photonic crystals
  • 2005
  • Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 87:12
  • Tidskriftsartikel (refereegranskat)abstract
    • A series of one-dimensional heteroepitaxial all-garnet magneto-optical photonic crystals has been synthesized and optically characterized. They are composed of alternating magneto-optically active Bi3Fe5O12 (BIG) and Gd3Ga5O12 (GGG) quarter-wave length layers pulsed laser deposited on to the GGG(001) substrate. Photonic crystals, as designed, exhibit stop band structure and the band gap with the transmittance central peak caused by the light localization in the half-wave length BIG cavity. Compared to previously reported [Bi3Fe5O12/Y3Fe5O12](m) photonic crystal [Appl. Phys. Lett. 84, 1438 (2004)], the replacement of optically dense Y3Fe5O12 garnet by transparent Gd3Ga5O12 enables significant enhancement of light rejection within the stop band. Photonic crystals spectra experience blue shift in oblique incidence geometry thus demonstrating feasibility to use this effect for tunable magneto-optical filters.
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17.
  • Khartsev, Sergiy, et al. (författare)
  • Characterization of heteroepitaxial Na0.5K0.5NbO3/La0.5Sr0.5CoO3 electro-optical cell
  • 2005
  • Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 86:6, s. 062901-1-062901-3
  • Tidskriftsartikel (refereegranskat)abstract
    • Heteroepitaxial Na0.5K0.5NbO3(1.5 mum)/La0.5Sr0.5CoO3(0.5 mum) (NKN/LSCO) films were grown on an Al2O3(0112) single crystal (r-cut sapphire) by rf-magnetron sputtering (NKN) and pulsed laser deposition (LSCO) techniques. Prism coupling waveguide refractometry has been employed to characterize vertical capacitive electro-optical cells with 2 X 8 mm(2) semitransparent Au top electrodes. Fitting reflectivity spectra to Fresnel formulas yields extraordinary and ordinary refractive indices n(e) = 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 the 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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18.
  • Khartsev, Sergiy, et al. (författare)
  • Heteroepitaxial Bi3Fe5O12/La3Ga5O12 films for magneto-optical photonic crystals
  • 2005
  • Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 86:14
  • Tidskriftsartikel (refereegranskat)abstract
    • Epitaxial La3Ga5O12 (LGG) garnet films and Bi3Fe5O12/La3Ga5O12 (BIG/LGG) heteroepitaxial film structures have been synthesized on the Gd3Ga5O12(GGG,111) single crystal. LGG films were grown by pulsed laser deposition technique whereas rf-magnetron sputtering was used to grow BIG films. LGG has a lattice constant 12.768 A that is bigger than that in GGG (12.384 A) and closer to that in BIG (12.626 A). We demonstrate feasibility of integration lanthanum gallium garnet with a giant Faraday rotator Bi3Fe5O12 in magneto-optical photonic crystals. Heteroepitaxial Bi3Fe5O12(1.9 mu m)/La3Ga5O12(300 nm)/GGG(111) structures show Faraday rotation as high as 5.74 deg/mu m compared to 5.46 deg/mu m in BIG/GGG at lambda=655 nm. Fitting LGG reflectivity spectra to Fresnel formulas yields LGG refractive index n(o)=1.981 compared to 1.963 in GGG at 655 nm. Dispersion of LGG refraction index follows Sellmeier formula n(o)(2)=1+2.77/[1-(143 nm/lambda)(2)] in the range from 400 nm to 1000 nm.
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19.
  • Khartsev, Sergiy, et al. (författare)
  • Heteroepitaxial Na0.5K0.5NbO3/La0.5Sr0.5CoO3 electro-optical cell
  • 2006
  • Ingår i: Integrated Ferroelectrics. - : Informa UK Limited. - 1058-4587 .- 1607-8489. ; 80, s. 133-143
  • 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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20.
  • Khartsev, Sergiy, et al. (författare)
  • High performance Bi3Fe5O12/Sm3Ga5O12 (m) magneto-optical photonic crystals
  • 2007
  • Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 101:5
  • Tidskriftsartikel (refereegranskat)abstract
    • We report the properties of one-dimensional heteroepitaxial all-garnet magneto-optical (MO) photonic crystals (MOPCs) composed of alternating MO-active Bi3Fe5O12 (BIG) and transparent Sm3Ga5O12 (SGG) quarter-wavelength layers grown by rf-magnetron sputtering on Ca,Mg,Zr:Gd3Ga5O12(111) and Gd3Sc2Ga3O12(001) crystals. MOPCs' spectra, as designed, exhibit a stop band structure and a band gap with the transmittance central peak at 750 nm caused by light localization in the half-wavelength BIG cavity. A series of MOPCs with different numbers of [BIG/SSG](m) reflectors (m=4, 5, and 6) has been fabricated to optimize the specific Faraday rotation theta(F) (deg/mu m) and MO-quality factor Q(deg)=2 parallel to theta(F)parallel to/absorption coefficient. A close BIG-to-SGG lattice match enabled significant improvement of [Bi3Fe5O12/Sm3Ga5O12](m) properties compared to previously reported [Bi3Fe5O12/Y3Fe5O12](m) [S. Kahl and A. M. Grishin, Appl. Phys. Lett. 84, 1438 (2004)] and [Bi3Fe5O12/Gd3Ga5O12](m) [S. I. Khartsev and A. M. Grishin, Alexander M.
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21.
  • Khartsev, Sergiy, et al. (författare)
  • Integration of colossal magnetoresistors with GaAs
  • 2005
  • Ingår i: Journal of Crystal Growth. - : Elsevier BV. - 0022-0248 .- 1873-5002. ; 284:02-jan, s. 1-5
  • Tidskriftsartikel (refereegranskat)abstract
    • Colossal magnetoresistive (CMR) La0.67Ca0.33MnO3 (LCMO) and La0.67Sr0.33MnO3 (LSMO) films have been grown by pulsed laser deposition technique on GaAs(001) substrates buffered with epitaxial MgO layer. X-ray diffraction revealed strong c-axis out-of-plane orientation and strong in-plane texture of CMR/MgO bilayers on GaAs single crystal. The maximum temperature coefficient of resistivity TCR = 9.0% K-1 at 223 K and 2.0% K-1 at 327 K. and the magnetoresistance Delta rho/rho similar to-7.95% kOe(-1) and -1.47% kOe(-1) have been achieved for LCMO/MgO/GaAs and LSMO/MgO/GaAs heteroepitaxial structures, respectively. Comparison with the test LCMO and LSMO films grown directly onto the bulk MgO(001) single cry tal demonstrates the identity of LSMO/MgO/GaAs and LSMO/MgO films properties whereas the LCMO films grown on MgO buffered GaAs show lower transition temperature T-c = 242 K compared to 253 K in LCMO/MgO.
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22.
  • Khartsev, Sergiy, et al. (författare)
  • New garnet films for magneto-optical photonic crystals
  • 2005
  • Ingår i: Magneto-Optical Materials For Photonics and Recording. - WARRENDALE : MATERIALS RESEARCH SOCIETY. - 1558997822 ; , s. 47-52
  • Konferensbidrag (refereegranskat)abstract
    • Epitaxial La3Ga5O12 (LGG) garnet films and Bi3Fe5O12/La3Ga5O12 (BIG/LGG) heteroepitaxial structures have been synthesized on Gd3Ga5O12(GGG,111) single crystal. LGG films were grown by Pulsed Laser Deposition (PLD) technique whereas rf-magnetron sputtering was used to grow BIG films. We demonstrate LGG is a promising material to be integrated with a giant Faraday rotator Bi3Fe5O12 in magneto-optical photonic crystals. LGG has a lattice constant 12.772 angstrom that is bigger than that in GGG (12.384 angstrom) and closer to that in BIG (12.626 angstrom). Heteroepitaxial Bi3Fe5O12(2 mu m)/La3Ga5O12(300nm) structures grown on the GGG(111) single crystal show the Faraday rotation as high as 5.74 deg/mu m compared to 5.46 deg/mu m in BIG/GGG at lambda = 655 nm. Fitting LGG reflectivity spectra to Fresnel formulas yields LGG refractive index n = 1.981 compared to 1.963 in GGG at 655 nm. Dispersion of LGG refraction index follows Sellmeier formula n(2) = 1 + 2.78/[1 - (138nm/lambda)(2)] in the range from 400 nm to 1000 nm.
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23.
  • Manuilov, Sergey A, et al. (författare)
  • Pulsed laser deposited Y3Fe5O12 films : Nature of magnetic anisotropy I
  • 2009
  • Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 106:12
  • Tidskriftsartikel (refereegranskat)abstract
    • Recently we sintered by pulsed laser deposition (PLD) technique the epitaxial Fe-deficient yttrium iron garnet (YIG) films with ferromagnetic resonance (FMR) linewidth as narrow as 0.9 Oe, the uniaxial anisotropy as high as H-u=-880 Oe, and demonstrated them feasible for magnetostatic waves band pass filter application [Manuilov , J. Appl. Phys. 105, 033917 (2009)]. Here we explore the origin of unusually high noncubic magnetic anisotropy. Using the angular resolved FMR spectroscopy we found that in addition to strong uniaxial anisotropy, cubic magnetic anisotropy experienced almost fivefold reduction compared to standard YIG grown by liquid phase epitaxy. Molecular field theory was employed to calculate saturation magnetization 4 pi M-s, cubic magnetocrystalline K-1, and uniaxial anisotropy K-u in garnets with Fe vacancies. The modeling utilizes crystal field parameters that we revealed from earlier published experimental data on diamagnetic ion substituted Y3Fe5O12 and Fe-substituted isomorphous diamagnetic garnets. Consistent single ion anisotropy crystal field theory perfectly fits experimentally observed high saturation magnetization, reduction in cubic, and appearance of strong uniaxial anisotropy in PLD-grown Fe-deficient YIG films. The redistribution of Fe vacancies between different magnetic sublattices was quantified and confirmed that in YIG(111) films ferric ions preferentially leave vacant octahedrally coordinated sites. Simulation of growth induced anisotropy proves the ordering of Fe3+ vacancies within octahedral sites. At equal number of available ferric ions and vacancies, the latter populate the octahedrons with distortion axis perpendicular to the film surface with the probability equal to 0.67. Deformation blockage of octahedral complexes with distortion axes directed along the film surface reduces this probability down to 0.14.
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24.
  • Manuilov, Sergey A., et al. (författare)
  • Pulsed Laser Deposited Y3Fe5O12 Films for Magnetostatic Wave Band Pass Filters
  • 2009
  • Ingår i: Solid State Phenomena. - 1012-0394 .- 1662-9779. ; 152-153, s. 377-380
  • Tidskriftsartikel (refereegranskat)abstract
    • Y3Fe5O12 (YIG) films were pulsed laser deposited onto the Gd3Ga5O12(111) substrates. Processing conditions were optimized to obtain films with a narrow ferromagnetic resonance (FMR) linewidth: 0.9 Oe in 1.22 mu m thick YIG at 9 GHz. Due to sharp film-to-substrate interface YIG films remain strained hence possess unusually high lattice mismatch induced uniaxial anisotropy H-u = - 880 Oe. We fabricated and tested magnetostatic surface wave (MSSW) band pass hybrid-type filters with YIG film lain on transducers alumina board. MSSW filter with antennas areal size of 2 mm(2) at 7.5 GHz shows insertion loss - 9 dB and a resonant 3 dB bandwidth as narrow as 12.5 MHz.
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25.
  • Manuilov, Sergey A., et al. (författare)
  • Submicron Y3Fe5O12 Film Magnetostatic Wave Band Pass Filters
  • 2009
  • Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 105:3
  • Tidskriftsartikel (refereegranskat)abstract
    • Thin Y3Fe5O12 (YIG) films were pulsed laser deposited onto Gd3Ga5O12 (111) and (001) substrates. Processing conditions were optimized to obtain compressively strained films with a ferromagnetic resonance linewidth at 9 GHz as narrow as 0.9 Oe and high uniaxial magnetic anisotropy H-u=-880 Oe. Several designs of magnetostatic surface wave (MSSW) bandpass filters were fabricated and tested: 0.45 and 0.22 mu m thick YIG films lain on transducers alumina board and with microstripe transducers defined directly onto YIG film, with effective antenna areal sizes of 2 and 0.4 mm(2). The MSSW filter with 2 mm(2) antenna shows, at 7.5 GHz, insertion loss -9 dB and a resonant -3 dB bandwidth as narrow as 12.5 MHz.
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26.
  • Markovich, V., et al. (författare)
  • Magnetic separation and inelastic tunneling in self-doped manganite films
  • 2009
  • Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 106:4
  • Tidskriftsartikel (refereegranskat)abstract
    • Magnetic and transport properties of 100 nm thick La0.9MnO3-delta self-doped manganite films have been investigated in the temperature range 5-300 K. The films exhibit a paramagnetic to ferromagnetic transition at T-C = 194 K. The temperature dependence of the resistivity shows a metal-insulator transition at 204 K and a strong resistivity increase below 160 K. The magnetoresistance was always negative and slightly bias dependent. Variations in resistivity with magnetic field and current are nonhysteretic, while the temperature dependence of the resistivity exhibits unusual inverse thermal hysteresis. The magnetic field independent inverse thermal hysteresis is strongly influenced by a thermal history of the sample. The data suggest that nonlinear low temperature transport is dominated by inelastic tunneling through intrinsic tunnel junctions formed by phase-separated ferromagnetic metallic domains and insulating anti ferromagnetic matrix.
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27.
  • Murzina, T. V., et al. (författare)
  • Nonlinear magneto-optical effects in all-garnet magnetophotonic crystals
  • 2009
  • Ingår i: Journal of Magnetism and Magnetic Materials. - : Elsevier BV. - 0304-8853 .- 1873-4766. ; 321:7, s. 836-839
  • Tidskriftsartikel (refereegranskat)abstract
    • Nonlinear magneto-optical properties of all-garnet magnetophotonic crystals composed of alternating layers of ferromagnetic Bi3Fe5O12 ( BIG) and Sm3Ga5O12 quarter-wavelength layers with a half-wavelength BIG microcavity mode are presented. The samples are grown by rf-magnetron sputtering on non-magnetic GGG substrate. Many-fold enhancement of the magnetization-induced effects in second-harmonic generation (SHG) as compared with linear magneto-optical effects are observed: the SHG magnetic contrast up to 50% and magnetization-induced rotation of the polarization plane of about 901 are measured at the resonance microcavity wavelengh of lambda = 779 nm. (C) 2008 Elsevier B. V. All rights reserved.
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28.
  • Pohl, A., et al. (författare)
  • Porous and dense perovskite films
  • 2008
  • Ingår i: NANOSTRUCTURED MATERIALS AND NANOTECHNOLOGY. ; , s. 153-163
  • Konferensbidrag (refereegranskat)abstract
    • La0.5Sr0.5CoO3 (LSCO) and La 0.67Ca0.33MnO3 (LCMO) films were prepared by sol-gel techniques and their structural and transport properties investigated. Films were spin-coated onto (001) LaAlO3 (LAO), (001) SrTiO 3 (STO), Pt/TiO2/SiO2/Si, and Al 2O3 substrates, and heated to 800C. The structural properties were investigated using X-ray diffraction, scanning and transmission electron microscopy (SEM and TEM). SEM studies showed that the films were crack-free and adhered well to the substrates. No preferential orientation of the perovskite films was observed on Si- or Pt/TiO2/SiO 2/Si-substrates, but films deposited on LAO and STO showed good alignment with the substrate. Transport measurements of epitaxial LCMO films show maximum temperature coefficient of resistivity (TCR) of 6.1% K-1 at 241 K and colossal magnetoresistance (CMR) of 32% at 246 K. The conductivity LSCO polycrystalline film was 1.7 mcm, while a epitaxial film had a conductivity of around 1.9 mcm.
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29.
  • Shkar, V. F., et al. (författare)
  • Structure and properties of deposited yttrium iron garnet films
  • 2005
  • Ingår i: Physics of the solid state. - : Pleiades Publishing Ltd. - 1063-7834 .- 1090-6460. ; 47:6, s. 1107-1110
  • Tidskriftsartikel (refereegranskat)abstract
    • Ferromagnetic resonance (FMR) and vibrating-sample magnetometer techniques were used to study the nature of the structural characteristics of yttrium iron garnet films deposited through either liquid phase epitaxy or laser evaporation on a (111)-oriented gallium gadolinium garnet substrate. It was proved that, based on the experimentally observed cubic magnetic anisotropy, deposited films should be considered to be single crystals. However, the absence of the FMR domain branch in a nonsaturated film and the shape of the magnetization curve indicate that a deposited film when demagnetized does not have a domain structure, as would be expected for a single-crystal film. According to the model proposed, a deposited film consists of close-packed single-crystal fragments with equal crystallographic orientation, the boundaries between which are in a partially atomically disordered state. As a result, such a film is both locally and macroscopically anisotropic, like a continuous single crystal. This film can split into domains only within a fragment (as is the case in a magnetic granular polycrystal); however, this does not happen, because the linear dimensions of a submicroscopic fragment are smaller than the equilibrium domain width.
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30.
  • Vanin, E. V., et al. (författare)
  • Broadband photoluminescence from pulsed laser deposited Er2O3 films
  • 2006
  • Ingår i: Journal of Luminescence. - : Elsevier BV. - 0022-2313 .- 1872-7883. ; 121:2, s. 256-258
  • Tidskriftsartikel (refereegranskat)abstract
    • Photoluminescence (PL) with the bandwidth of 45 nm (1523-1568 nm, at the level of 3 dB) was observed in amorphous Er2O3 films grown on to the quartz substrate by pulsed laser ablation of erbium oxide stoichiometric target. Optical transmission spectrum has been fitted to Swanepoel formula to determine the dispersion of refractive index and to extract resonance absorption peaks at 980 and 1535 nm. The maximum gain coefficient of 800 dB/cm at 1535 nm was estimated using McCumber theory and experimental spectrum of the resonance absorption. In 5.7mm-long waveguide amplifier a theory predicts the spectral gain of 20dB with 1.4dB peak-to-peak flatness in the bandwidth of 31 nm (1532-1563 nm) when 73% of Er3+ ions are excited from the ground state to the I-4(13/2) laser level. Strong broadband PL at room temperature and inherently flat spectral gain promise Er2O3 films for ultra-short high-gain optical waveguide amplifiers and integrated light circuits.
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