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Träfflista för sökning "WFRF:(Grishin Alexander M.) "

Sökning: WFRF:(Grishin Alexander M.)

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1.
  • Belotelov, V. I., et al. (författare)
  • Magnetophotonic intensity effects in hybrid metal-dielectric structures
  • 2014
  • Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 89:4, s. 045118-
  • Tidskriftsartikel (refereegranskat)abstract
    • The magneto-optical properties of a hybrid metal-dielectric structure consisting of a one-dimensional gold grating on top of a magnetic waveguide layer are studied experimentally and theoretically. It is demonstrated that a magnetic field applied in the longitudinal configuration (in the plane of the magnetic film and perpendicular to the slits in the gold grating) to the metal-dielectric structure modifies the field distribution of the optical modes and thus changes the mode excitation conditions. In the optical far field, this manifests in the alteration of the optical transmittance or reflectance when the structure becomes magnetized. This magneto-optical effect is shown to represent a novel class of effects related to the magnetic-field-induced modification of the Bloch modes of the periodic hybrid structure. That is why we define this effect as "longitudinal magnetophotonic intensity effect" (LMPIE). The LMPIE has two contributions, odd and even in magnetization. While the even LMPIE is maximal for the light polarized perpendicular to the grating slits (TM) and minimal for the orthogonal polarization (TE), the odd LMPIE takes maximum values at some intermediate polarization and vanishes for pure TM and TE polarizations. Two principal modes of the magnetic layer - TM and TE - acquire in the longitudinal magnetic field additional field components and thus turn into quasi-TM and quasi-TE modes, respectively. The largest LMPIE is observed for excitation of the antisymmetrical quasi-TE mode by TM-polarized light. The value of the LMPIE measured for the plasmonic structure with a magnetic film of Bi2Dy1Fe4Ga1O12 composition is about 1% for the even effect and 2% for the odd one. However, the plasmonic structure with a magnetic film with a higher concentration of bismuth (Bi2.97Er0.03Fe4Al0.5Ga0.5O12) gives significantly larger LMPIE: even LMPIE reaches 24% and odd LMPIE is 9%. Enhancement of the magneto-optical figure of merit (defined as the ratio of the specific Faraday angle of a magnetic film to its absorption coefficient) of the magnetic films potentially causes the even LMPIE to exceed 100% as is predicted by calculations. Thus, the nanostructured material described here may be considered as an ultrafast magnetophotonic light valve.
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2.
  • Belotelov, V. I., et al. (författare)
  • Plasmon-mediated magneto-optical transparency
  • 2013
  • Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 4, s. 2128-
  • Tidskriftsartikel (refereegranskat)abstract
    • Magnetic field control of light is among the most intriguing methods for modulation of light intensity and polarization on sub-nanosecond timescales. The implementation in nanostructured hybrid materials provides a remarkable increase of magneto-optical effects. However, so far only the enhancement of already known effects has been demonstrated in such materials. Here we postulate a novel magneto-optical phenomenon that originates solely from suitably designed nanostructured metal-dielectric material, the so-called magneto-plasmonic crystal. In this material, an incident light excites coupled plasmonic oscillations and a waveguide mode. An in-plane magnetic field allows excitation of an orthogonally polarized waveguide mode that modifies optical spectrum of the magneto-plasmonic crystal and increases its transparency. The experimentally achieved light intensity modulation reaches 24%. As the effect can potentially exceed 100%, it may have great importance for applied nanophotonics. Further, the effect allows manipulating and exciting waveguide modes by a magnetic field and light of proper polarization.
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3.
  • Takahashi, M., et al. (författare)
  • Oxygen annealing effect of photoelectron spectra in SrBi2Ta2O9 film
  • 2002
  • Ingår i: Japanese Journal of Applied Physics. - 0021-4922 .- 1347-4065. ; 41:11B, s. 6797-6802
  • Tidskriftsartikel (refereegranskat)abstract
    • Photoelectron spectra have been studied to clarify O-2-annealing effects on the band diagram of the metal-SrBi2Ta2O9 (SBT) junction and ionization energy of SBT films deposited by the pulsed laser, deposition (PLD) method. Photoemission spectra obtained by ultraviolet light irradiation have a threshold of 5.90 eV for the as-deposited SBT film and 5.56 eV for the O-2-annealed one. This shift of the threshold indicates that the annealing treatment has increased the Fermi level by 0.34 eV. On the assumption of a 4.2 eV band gap and 3.5 eV electron affinity for the SBT, as-deposited SBT has been estimated to give a 0.60 eV lower barrier height for holes than that for electrons, which is possibly because of, insufficiently oxidized (Bi2O2)(2+) layers as indicated by X-ray photoelectron spectroscopy (XPS). After annealing in O-2, however, barrier height energies for holes and electrons become closer to each other. These results agree with our previous studies which have reported that the O-2-annealing suppressed the leakage current through SBT and improved the retention characteristics of the metal-ferroelectric-insulator-semiconductor structure.
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4.
  • Timopheev, A. A., et al. (författare)
  • The influence of intergranular interaction on the magnetization of the ensemble of oriented Stoner-Wohlfarth nanoparticles
  • 2009
  • Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 105:8
  • Tidskriftsartikel (refereegranskat)abstract
    • The influence of interparticle interaction on the processes of magnetization reversal is considered for an ensemble of oriented Stoner-Wohlfarth nanoparticles. This is done through a solution of a kinetic equation describing the relaxation of the total magnetization to its equilibrium value in an effective mean field which includes a term proportional to the instantaneous value of the magnetization. It is shown that the interparticle interaction influences the temperature dependence of a coercive field. Under certain conditions, the presence of the interparticle interaction can lead to the formation of the so-called superferromagnetic state with the correlated directions of the magnetic moments of the particles. If the system is unable to come to the equilibrium during the time interval necessary to perform measurements, some measured quantities become dependent on the measurement time. It is shown that the blocking temperature T-b and the temperature dependence of coercive field at T < T-b are strongly dependent on a measurement time. At T>T-b, however, the coercivity, if exists, does not depend on the measurement time. The data of magnetostatic measurements, carried out on the (CoFeB)(x)-(SiO2)(1-x) nanogranular films with the concentration of ferromagnetic particles slightly lower than a percolation threshold, are in compliance with the results of the calculations.
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5.
  • Popov, V., et al. (författare)
  • Morphology of PZT-PMN films grown from airflow
  • 2003
  • Ingår i: Integrated Ferroelectrics. - : Informa UK Limited. - 1058-4587 .- 1607-8489. ; 54, s. 575-584
  • Tidskriftsartikel (refereegranskat)abstract
    • Lead zirconate titanate-lead magnesium niobate (PZT-PMN) films with thicknesses in the range 5 to 200 mum were fabricated by deposition from airflow at room temperature. Precursor powders of PZT and PMN were mixed in a ball mill and entrained in an airflow generated by a commercial jet-mill ( Micron-Master 02-506 ). Films were grown at a rate of 1 mum/minute onto the Ni and tungsten carbide substrates exposed to the air-powder mixture. Unfired, poled PZT-PMN films provided an audio acoustic response and form translucent 20-30 mum thick layers. Full density of the air-flow deposited materials has been achieved at temperatures 450degreesC lower than that typical for ball milled bulk PZT-PMN ceramics. After sintering for 2 hours at 850degreesC PZT-PMN ceramics with relative density of 99.5%, epsilon similar to 2170, tan delta similar to 0.009 @1 kHz and acceptable piezoelectric properties was obtained. Films sintered 2 hours at 1000degreesC showed remnant polarization P-r = 26 muC/cm(2) , P-s = 36 muC/cm(2) @95 kV/cm, and 50 Hz ac electric breakdown field as high as 120-170 kV/cm. Unusual grain morphology governs improved sinterability and enhanced properties of ferroelectric ceramics. Optical and AFM micrographs revealed needle-like grains preferentially oriented parallel to the air-powder stream. As-deposited films were found to be very non-uniform across the thickness: glass-like and with tensile strain on the contact surface. This strain is released and film microcrystalline structure becomes uniform in annealed film.
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6.
  • Abadei, S., et al. (författare)
  • DC field dependent properties of Na0.5K0.5NbO3/SiO2/Si structures at millimeter-wave frequencies
  • 2001
  • Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 78:13, s. 1900-1902
  • Tidskriftsartikel (refereegranskat)abstract
    • Dielectric properties of laser-ablated 0.5-mum-thick c-axis epitaxial Na0.5K0.5NbO3 films on high-resistivity (7.7 Omega cm) silicon SiO2/Si substrate are studied experimentally at frequencies up to 40 GHz. For measurements, planar 0.5-mum-thick gold electrodes (interdigital and straight slot) are photolithography defined on the top surface of Na0.5K0.5NbO3 films. The slot width between the electrodes is 2 or 4 mum. 13% capacitance change at 40 V dc bias and Q factor more than 15 are observed at 40 GHz, which makes the structure useful for applications in electrically tunable millimeter-wave devices.
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7.
  • Blomqvist, Mats, et al. (författare)
  • High-performance epitaxial Na0.5K0.5NbO3 thin films by magnetron sputtering
  • 2002
  • Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 81:2, s. 337-339
  • Tidskriftsartikel (refereegranskat)abstract
    • Epitaxial Na0.5K0.5NbO3 (NKN) thin films have been grown on LaAlO3 substrates by rf magnetron sputtering of a stoichiometric, high-density, ceramic target. X-ray diffraction analysis showed c-axis oriented cube-on-cube growth. Micrometer size interdigital capacitor (IDC) structures were defined on the surface of the NKN film using photolithography. The electrical characterization at 1 MHz showed dissipation factor tan delta of 0.010, tunability 16.5% at 200 kV/cm and dielectric permittivity epsilon(r)=470. The frequency dispersion of epsilon(r) between 1 kHz and 1 MHz was 8.5% and the IDCs showed very good insulating properties with leakage current density on the order of 30 nA/cm(2) at 400 kV/cm. The polarization loop exhibits weak ferroelectric hysteresis with maximum polarization 23.5 muC/cm(2) at 600 kV/cm. These results are promising for tunable microwave devices based on rf sputtered NKN thin films.
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8.
  • Cho, C. R., et al. (författare)
  • Ferroelectric Na0.5K0.5NbO3 thin films by pulsed laser deposition
  • 2000
  • Ingår i: Integrated Ferroelectrics. - : Informa UK Limited. - 1058-4587 .- 1607-8489. ; 31:1-4, s. 35-45
  • Tidskriftsartikel (refereegranskat)abstract
    • Highly c-axis oriented single phase Na0.5K0.5NbO3 (NKN) thin films have been deposited onto polycrystalline Pt80Ir20 substrates and SiO2/Si(001) wafers using pulsed laser ablation of stoichiometric ceramic target. Strong self-assembling of NKN films along the [001] direction has been observed. Properties of NKN/Pt thin film structures have been successfully tailored by oxygen pressure control from the ferroelectric state, characterized by the remnant polarization of 12 muC/cm(2), dielectric constant epsilon similar to 520 and tan delta - 0.024 @ 100 kHz, to superparaelectric state with tan delta as low as 0.003 and epsilon = 210 with very small 1.7% dispersion in the frequency domain 0.4-100 kHz and less than 10% Variation in the temperature range 77-415 K. NKN films grown onto SiO2/Si(001) substrates show quadrupled super-lattice structure along c-axis, loss tan delta less than 0.01, and epsilon similar to 110 @ 1 MHz. C-V measure ments for Au/NKN(270nm)/SiO2/Si MFIS-diode structure yield memory window of 3.26 V at the programmable voltage of 8 V.
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9.
  • Cho, Coong-Rae, et al. (författare)
  • Na0.5K0.5NbO3/SiO2/Si Thin Film Varactor
  • 2000
  • Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 76, s. 1761-
  • Tidskriftsartikel (refereegranskat)abstract
    • Perfectly c-axis oriented micrometer thickNa 0.5 K 0.5 NbO 3 (NKN) films have been prepared on a thermally grown ultrathinSiO 2 template layer onto a Si(001) wafer by the pulsed laser deposition technique. A x-ray diffraction θ–2θ scan reveals multiple-cell structuring of single phase NKN film along the polar axis, while filmsgrown onto amorphous ceramic (Corning) glass show a mixture of slightly c-axis oriented NKN and pyrochlore phases. This implies a small amount ofSiO 2 crystallites distributed in an amorphous matrix inherit Si(001) orientation and promotes highly oriented NKN film growth. NKN filmdielectric permittivityε ′ was found to vary from 114.0 to 107.2 in the frequency range 1 kHz–1 MHz, while the resistivity was on the order of2.6×10 10  Ω cm @ 20 kV/cm. The planar interdigital variable reactance device (varactor) based on theNKN/SiO 2 /Si thin film structure possesses a dissipation factor of 0.8% at 1 MHz and zero bias, electrical tunability of 3.1%, and nA order leakage current at 20 V bias at room temperature.
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10.
  • Cho, C. R., et al. (författare)
  • Na0.5K0.5NbO3 thin films for MFIS_FET type non-volatile memory applications
  • 2002
  • Ingår i: Integrated Ferroelectrics. - 1058-4587 .- 1607-8489. ; 49, s. 21-30
  • Tidskriftsartikel (refereegranskat)abstract
    • Na0.5K0.5NbO3(NKN) thin films have been prepared on Pt80Ir20, SiO2/Si, and Ta2O5/Si substrates for ferroelectric non-volatile memory applications. Ferroelectric hysteresis loops for Au/NKN/Pt80Ir20 vertical capacitor yielded remnant polarization of 12 muC/cm(2) and coercive field similar to20 kV/cm. Significant flat-band voltage V-FB shifts with buffer layer thickness in Au/NKN/SiO2/Si structures have been attributed to the intermixing between Na and K alkali ions and SiO2 layer. On the other hand, Au/NKN/Ta2O5/Si structure exhibited wide memory window without significant V-FB deviations, low leakage currents, and rather long retention time at zero bias.
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11.
  • Cho, Choong-Rae, et al. (författare)
  • Na0.5K0.5NbO3 thin films for voltage controlled acoustoelectric device applications
  • 2002
  • Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 80:17, s. 3171-3173
  • Tidskriftsartikel (refereegranskat)abstract
    • Perovskite Na0.5K0.5NbO3 (NKN) thin films have been prepared on Y+36degrees cut single crystal quartz substrates using the pulsed laser ablation technique. X-ray diffraction theta-2theta and omega-scan data demonstrate almost perfectly c-axis oriented film textures with narrow mosaic broadening. Radio frequency dielectric spectroscopy showed that the films possess relatively high dielectric permittivities, low dielectric losses, and low frequency dispersions. Capacitance-voltage (C-V) measurements for a 2 mum slot NKN/quartz interdigital capacitor yield 23.1% tunability by applying 40 V bias at 1 MHz, while C-V hysteresis indicates polarization reversal. The considerable voltage tunability with superior crystallinity in piezoelectric NKN films on quartz substrates suggests their potential use for novel voltage tunable acoustoelectric devices.
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12.
  • Grishin, Alexander M., et al. (författare)
  • Gadolinia nanofibers as a multimodal bioimaging and potential radiation therapy agent
  • 2015
  • Ingår i: AIP Advances. - : AIP Publishing. - 2158-3226. ; 5:5
  • Tidskriftsartikel (refereegranskat)abstract
    • Continuous bead-free C-type cubic gadolinium oxide (Gd2O3) nanofibers 20-30 mu m long and 40-100 nm in diameter were sintered by sol-gel calcination assisted electrospinning technique. Dipole-dipole interaction of neighboring Gd3+ ions in nanofibers with large length-to-diameter aspect ratio results in some kind of superparamagnetic behavior: fibers are magnetized twice stronger than Gd2O3 powder. Being compared with commercial Gd-DTPA/Magnevist (R), Gd2O3 diethyleneglycol-coated (Gd2O3-DEG) fibers show high 1/T-1 and 1/T-2 proton relaxivities. Intense room temperature photoluminescence, high NMR relaxivity and high neutron scattering cross-section of Gd-157 nucleus promise to integrate Gd2O3 fibers for multimodal bioimaging and neutron capture therapy.
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13.
  • Grishin, Alexander M., et al. (författare)
  • Ultra-hard amorphous AlMgB14 films RF sputtered onto curved substrates
  • 2017
  • Ingår i: Materials Research Express. - : Institute of Physics (IOP). - 2053-1591. ; 4:3
  • Tidskriftsartikel (refereegranskat)abstract
    • Recently, hard AlMgB14 (BAM) coatings were deposited for the first time by RF magnetron sputtering using a single stoichiometric ceramic target. High target sputtering power and sufficiently short target-to-substrate distance were found to be critical processing conditions. They enabled fabrication of stoichiometric in-depth compositionally homogeneous films with the peak values of nanohardness 88 GPa and Young's modulus 517 GPa at the penetration depth of 26 nm and, respectively, 35 GPa and 275 GPa at 200 nm depth in 2 mu m thick film (Grishin et al 2014 JETP Lett. 100 680). The narrow range of sufficiently short target-to-substrate distance makes impossible to coat non flat specimens. To achieve ultimate BAM films' characteristics onto curved surfaces we developed two-step sputtering process. The first thin layer is deposited as a template at low RF power that facilitates a layered Frank van der Merwe mode growth of smooth film occurs. The next layer is grown at high RF target sputtering power. The affinity of subsequent flow of sputtered atoms to already evenly condensed template fosters the development of smooth film surface. As an example, we made BAM coating onto hemispherical 5 mm in diameter ball made from a hard tool steel and used as a head of a special gauge. Very smooth (6.6 nm RMS surface roughness) and hard AlMgB14 films fabricated onto commercial ball-shaped items enhance hardness of tool steel specimens by a factor of four.
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14.
  • Grishin, Michael A., et al. (författare)
  • High performance films of binary system SrTiO3-PbZr0.52Ti0.48O3 on sapphire
  • 2001
  • Ingår i: Integrated Ferroelectrics. - : Informa UK Limited. - 1058-4587 .- 1607-8489. ; 39:1-4, s. 351-358
  • Tidskriftsartikel (refereegranskat)abstract
    • Continuous series of solid solutions x.SrTiO3-(1-x).PbZr0.52Ti0.48O3 (SPZT) have been grown by pulsed laser deposition technique onto La0.7Sr0.3CoO3/Al2O3(01 (1) under bar2) single crystal. Films properties have been characterized in Au/SPZT/La0.7Sr0.3CoO3(LSCO)/Al2O3 vertical capacitive cell. X-ray diffraction shows SPZT/LSCO bilayer grows in strict epitaxial relationship with sapphire substrate: (001) SPZT parallel to (001) LSCO parallel to (01 (1) under bar2) Al2O3; [010] SPZT parallel to [010] LSCO parallel to [421] Al2O3. LSCO layer was found to be tensile strained, while SPZT film experiences tetragonal distortions c/a -1 approximate to 0.86% which are much lower than 2.73% in pure PZT ceramics. Curie temperature in SPZT film has been tailored continuously in the explored temperature range 77 K to 400 K by controlling SrTiO3:PZT ratio. Processing parameters have been optimized to get the highest tunability factor K = epsilon'(0) - epsilon'(V)/epsilon'(0) x 1/tandelta . SrTiO3:PZT=83:17 film exhibits superior properties: at I kHz maximum dielectric perinittivity and minimum loss tandelta were found to be 870 and 0.005, respectively; while K-factor exceeds value of 60 in the temperature range 280 to 350 degreesC reaching the maximum value of 64 at 325 degreesC. SPZT films can withstand prolonged pre-breakdown electric field and has resistivity as high as 3.5 10(12) Omega cm at 186 kV/cm.
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15.
  • Hollmark, M., et al. (författare)
  • Processing and properties of soft magnetic Fe40Co40P14B6 amorphous alloy
  • 2001
  • Ingår i: IEEE transactions on magnetics. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9464 .- 1941-0069. ; 37:4, s. 2278-2280
  • Tidskriftsartikel (refereegranskat)abstract
    • The Fe40Co40P14B6 metallic alloy has been prepared in a glassy state by a melt-spinning process. The 15-25 mum thick as-quenched, ribbons have superior soft magnetic properties compared with those of well-known Fe40Ni40P14B6 glass: the saturation magnetization is about 1.45 T, coercive field 4.0 A/m @ 0.1 Hz, incremental magnetic permeability mu (max) similar to 90 000 @ 60 Hz and Curie temperature above 700 K. The crystallization temperature, determined by differential scanning calorimeter, is approximately 60 K higher than that for FeNi-based alloy, indicating the enhanced thermal stability of FeCo-glass.
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16.
  • Johnsson, P., et al. (författare)
  • Transport anisotropy in hetero-amorphous (CoFeB)-SiO2 thin films
  • 2003
  • Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 93:10, s. 8101-8103
  • Tidskriftsartikel (refereegranskat)abstract
    • We here present resisitivity and magnetoresistance measurements of two granular (CoFeB)-SiO2 amorphous thin films, with a different amount of metallic content. The films were deposited onto substrates sitting on a rotating cylinder. This induces anisotropy in the film plane, which is higher for the sample with less metallic content. This film exhibits typical isotropic giant magnetoresistance (GMR), while the film with higher-metallic content has less anisotropic resistivity, and shows a mixture of GMR and anisotropic magnetoresistance (AMR). The AMR appears at fields below 500 Oe. We believe that this has not been observed before in amorphous samples.
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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)
  • Comparative characteristics of Na0.5K0.5NbO 3 films on Pt by pulsed laser deposition and magnetron sputtering
  • 2003
  • Ingår i: Integrated Ferroelectrics. - : Informa UK Limited. - 1058-4587 .- 1607-8489. ; 55, s. 769-779
  • Tidskriftsartikel (refereegranskat)abstract
    • Ferroelectric Na0.5K0.5NbO3 (NKN) thin films were grown on the Pt80Ir20 polycrystalline substrates by pulsed laser deposition (PLD) and radio frequency-magnetron sputtering (RF) technique using the same stoichiometric Na0.5K 0.5NbO3 ceramic target. X-ray diffraction proved both PLD- and RF-made Na0.5K0.5NbOj/Pt80Ir20 films are single phase and have preferential c-axis orientation. Temperature dependence of dielectric permittivity reveals the presence of two phase transitions around 210 and 410°C. Capacitance vs. applied voltage C-V @ 100 kHz, I-V, and P-E hysteresis characteristics recorded for the vertical capacitive structures yielded loss tan δ = 0.026 and 0.016, tunability about 44.5 and 30% @ 100 kV/cm, Ohmic resistivity 6.7 × 1012 Ω·cm and 0.2 × 1012 Ω·cm, remnant polarization 11.7 and 9.7 μC/cm2, coercive field 28.0 and 94.6 kV/cm for PLD- and RF-films, respectively. Piezoelectric test carried out in hydrostatic conditions showed piezoelectric coefficient dH = 21 for PLD-NKN and 15 pC/N for RF-NKN film.
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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)
  • Thin PZT film pressure microsensor
  • 2001
  • Ingår i: Materials Research Society Symposium Proceedings. - 0272-9172 .- 1946-4274. ; 666, s. F8121-F8126
  • Tidskriftsartikel (refereegranskat)abstract
    • We report on a ferroelectric film pressure sensor fabricated on the top of 4 mm long and 1.4 mm in diameter Pt80Ir20 (PtIr) rod-shaped tip. It consists of a PZT(0.5 μm)/LSMO(0.1 μm) film heterostructure, deposited by pulsed laser ablation of stoichiometric ceramic targets PbZr0.52Ti0.48O3 and La0.67Sr0.33MnO3, and a circular, ∅ = 1.2 mm, Au electrode on the top of the PZT film. The Au/PZT/LSMO/PtIr thin-film capacitor demonstrates good ferroelectric properties: dielectric constant of 762 and loss tanδ =0.008 @ 5 kHz, induced polarization as high as 32 μC/cm2 at electric field of 250 kV/cm. Piezoelectric test, performed in a hydrostatic pressure chamber, exhibits the piezoelectric constant to be as high as 67 pC/N. This is 20% higher than 56 pC/N shown by a polarized bulk PZT sensor fabricated from the ceramics used as the target in the pulsed laser deposition process. Such an increase of the piezoelectric constant we attribute to the preferential (001) orientation of the PZT film grown on the PtIr bulk substrate. The resolution of the thin PZT film pressure microsensor was found to be about 1 mbar.
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21.
  • Koh, J. H., et al. (författare)
  • Dielectric properties and Schottky barriers in silver tantalate-niobate thin film capacitors
  • 2001
  • Ingår i: Integrated Ferroelectrics. - 1058-4587 .- 1607-8489. ; 39:1-4, s. 1361-1368
  • Tidskriftsartikel (refereegranskat)abstract
    • Submicron thick ferroelectric Ag(Ta,Nb)O-3 films have been pulsed laser deposited on the bulk Pt80Ir20 polycrystalline substrates. They are ferroelectric at temperatures below 125 K with the remnant polarization of 0.4 muC/cm(2) @ 77K and paraelectric at higher temperatures with tandelta @ 100 kHz as low as 0.015. Extensive I-V characterization has been performed in a wide temperature range 77 K to 350 K for vertical Me/Ag(Ta,Nb)O-3/Pt80Ir20 capacitive cells, where the metals Me = Pd, Au, Cr, and Al have been used as a top electrode. The electronic transport in thin Me/Ag(Ta,Nb)O-3/Pt80Ir20 capacitors follows the Schottky emission mechanism with the barrier height for the Pd, Au, Cr, and Al of 0.85, 0.8, 0.74, and 0.69 eV, respectively.
  •  
22.
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23.
  • Koo, S. M., et al. (författare)
  • Ferroelectric Pb(Zr,Ti)O-3/Al2O3/4H-SiC diode structures
  • 2002
  • Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 81:5, s. 895-897
  • Tidskriftsartikel (refereegranskat)abstract
    • Pb(Zr,Ti)O-3 (PZT) films (450 nm thick) were grown on 4H-silicon carbide (SiC) substrates by a pulsed-laser deposition technique. X-ray diffraction confirms single PZT phase without a preferred orientation. Stable capacitance-voltage (C-V) loops with low conductance (<0.1 mS/cm(2), tan deltasimilar to0.0007 at 400 kHz) and memory window as wide as 10 V were obtained when 5-nm-thick Al2O3 was used as a high band gap (E(g)similar to9 eV) barrier buffer layer between PZT (E(g)similar to3.5 eV) and SiC (E(g)similar to3.2 eV). High-frequency (400 kHz) C-V characteristics revealed clear accumulation, and depletion behavior. Although the charge injection from SiC is the dominant mechanism for C-V hysteresis in PZT/Al2O3/SiC, negligible sweep rate dependence and negligible applied bias dependence were observed compared to that of PZT/SiC. By using room-temperature photoilluminated C-V measurements, the interface states as well as the charge trapping in the PZT/Al2O3 stacks have been calculated.
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24.
  • Koo, S. M., et al. (författare)
  • Ferroelectric Pb(Zr0.52Ti0.48)/SiC field-effect transistor
  • 2003
  • Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 83:19, s. 3975-3977
  • Tidskriftsartikel (refereegranskat)abstract
    • Nonvolatile operation of ferroelectric gate field-effect transistors in silicon carbide (SiC) is demonstrated. Depletion mode transistors have been realized by forming a Pb(Zr0.52Ti0.48)O-3/Al2O3 gate stack on n-type epitaxial channel layer and p-type substrate of 4H-SiC. A memory window, as wide as 5 V, has been observed in the drain current and the ferroelectric gate voltage transfer characteristics. The transistor showed memory effect from room temperature up to 200 degreesC, whereas stable transistor operation was observed up to 300 degreesC. The retention of remnant polarization was preserved after 2x10(4) s at 150 degreesC with no bias on the gate.
  •  
25.
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26.
  • Koo, S. M., et al. (författare)
  • Processing and properties of ferroelectric Pb(Zr,Ti)O-3/silicon carbide field-effect transistor
  • 2003
  • Ingår i: Integrated Ferroelectrics. - : Informa UK Limited. - 1058-4587 .- 1607-8489. ; 57, s. 1221-1231
  • Tidskriftsartikel (refereegranskat)abstract
    • Metal-ferroelectric-(insulator)-semiconductor MF(I)S structures have been fabricated and the properties of pulsed laser-deposited PZT/Al-2 O-3 gate stacks have been studied on n - and p -type 4H-SiC. Among several polytypes of SiC, 4H-SiC is considered as the most attractive one because of its wider bandgap (E-g congruent to 3.2 eV) as well as higher and more isotropic bulk mobility than other polytypes. Single PZT phase without a preferred orientation was confirmed by x-ray diffraction. The interface trap densities N-IT , fixed oxide charges Q(F) , and trapped oxide charges Q HY have been estimated by C-V curves with and without photo-illuminated measurements at room temperature. It is found that the charge injection from SiC is the dominant mechanism for C-V hysteresis. Importantly, with PZT/Al-2 O-3 gate stacks, superior C-V characteristics with negligible sweep rate dependence and negligible time dependence under the applied bias were obtained compared to PZT directly deposited on SiC. The MFIS structures exhibited very stable capacitance-voltage C-V loops with low conductance (<0.1 mS/cm(2) , tan delta similar to 0.0007 at 400 kHz) and memory window as wide as 10 V, when 5 nm-thick Al2O3 was used as a high bandgap (E-g similar to 9 eV) barrier buffer layer between PZT (E-g similar to 3.5 eV) and SiC (E-g similar to 3.2 eV). The structures have shown excellent electrical properties promising for the gate stacks as the SiC field-effect transistors (FETs). Depletion mode transistors were prepared by forming a Pb(Zr-0.52 Ti-0.48 )O-3 /Al-2 O-3 gate stack on 4H-SiC. Based on this structure, ferroelectric Pb(Zr,Ti)O-3 (PZT) thin films have been integrated on 4H-silicon carbide (SiC) in a SiC field-effect transistor process. Nonvolatile operation of ferroelectric-gate field-effect transistors in silicon carbide (SiC) is demonstrated.
  •  
27.
  • Koo, S. -M, et al. (författare)
  • Towards ferroelectric field effect transistors in 4H-silicon carbide
  • 2002
  • Ingår i: Materials Research Society Symposium - Proceedings. - Boston, MA. ; , s. 371-379
  • Konferensbidrag (refereegranskat)abstract
    • We report on the integration of ferroelectric Pb(Zr,Ti)O3 (PZT) thin films on 4H-silicon carbide and their electrical properties. The structures of metal-ferroelectric-(insulator)-semiconductor MF(I)S and metal-ferroelectric-metal-insulator-semiconductor MFMIS have been fabricated and characterized. The MFMIS structures of Au/PZT/Pt/Ti/SiO2/SiC have shown fully saturated P-E hysteresis loops with remnant polarization Pr = 14.2 ÎŒC/cm2 and coercive field Ec = 58.9 kV/cm. The MFIS structures exhibited stable capacitance-voltage C-V loops with low conductance (<0.1 mS/cm2, tan ÎŽ ∌ 0.0007 at 12 V, 400 kHz) and memory window as wide as 10 V, when a 5 nm-thick Al2O3 was used as a high bandgap (Eg ∌ 9 eV) barrier buffer layer between PZT (Eg ∌ 3.5 eV) and SiC (Eg ∌ 3.2 eV). Both structures on n- and p- SiC have shown electrical properties promising for the application to the gate stacks for the SiC field-effect transistors (FETs) and the design and process issues on different types of the metal-ferroelectric-silicon carbide field-effect transistors (FETs) have also been proposed.
  •  
28.
  • Losin, C., et al. (författare)
  • Torsional dependence of second-harmonic amplitude of giant magnetoimpedance in FeCoSiB amorphous wire
  • 2002
  • Ingår i: IEEE transactions on magnetics. - 0018-9464 .- 1941-0069. ; 38:5, s. 3087-3089
  • Tidskriftsartikel (refereegranskat)abstract
    • The effect of torsional stresses in the magnetoimpedance response of a (Co0.94Fe0.06)(72.5)Si12.5B15 amorphous wire is analyzed. In particular, the occurrence of a second-harmonic contribution of the magnetoimpedance voltage is analyzed and compared with the first-harmonic amplitude (impedance). The evolution of both harmonic components are correlated to the estimated permeability contributions obtained through the analysis of the estimated rotational hysteresis loops. The highest torsional dependence of the second-harmonic contribution can be used in the development of new magnetoelastic sensors.
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29.
  • Lyfar, D. L., et al. (författare)
  • Microwave absorption in a thin La0.7Sr0.3MnO3 film : Manifestation of colossal magnetoresistance
  • 2004
  • Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 69:10
  • Tidskriftsartikel (refereegranskat)abstract
    • Microwave (MW) absorption by a thin La0.7Sr0.3MnO3 film on a SrTiO3 substrate is investigated at a 9.1 GHz as a function of a dc magnetic field. Features of this absorption, namely, the jump in the absorption derivative, have been detected as the applied field passes through its zero value. Hysteretic behavior of the jumps is also observed. The results are discussed based on the model in which MW losses, additional to the ferromagnetic resonance, arise due to attenuation of MW currents induced in the sample by both variable magnetic induction and MW electrical field near the substrate surface with high dielectric permittivity. We show that zero-field anomalies in MW absorption are directly coupled with manganite magnetoresistive properties.
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30.
  • 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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31.
  • Medvedev, Y. V., et al. (författare)
  • The diagnostics of thermal kinetic coefficients for the optimization of film bolometer properties
  • 2002
  • Ingår i: Technical physics. - : Pleiades Publishing Ltd. - 1063-7842 .- 1090-6525. ; 47:1, s. 114-120
  • Tidskriftsartikel (refereegranskat)abstract
    • A pulsed microwave technique for the fast and accurate diagnostics of a complete set of thermal kinetic coefficients in single-layer film structures is developed. The technique is tested on La-0.7(Pb0.7Sr0.3)(0.3)MnO3 films on LaAlO3 and SrTiO3 substrates-the structures featuring a temperature resistance coefficient of 5-7%, which is the highest for manganite-containing materials at room temperature. The results of numerical simulation show that the performance of the uncooled bolometers can be improved by optimizing the thermal conductivity of the substrate and matching the thermal resistances of the film-substrate and substrate-thermostat interfaces.
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32.
  • Nikolaenko, Y. M., et al. (författare)
  • Fast bolometric response of bulk La0.7Sr0.3MnO3 electroceramic structures
  • 2000
  • Ingår i: Acta Physica Polonica. A. - 0587-4246 .- 1898-794X. ; 97:6, s. 991-995
  • Tidskriftsartikel (refereegranskat)abstract
    • We report on the performance of a microwave electroceramic bolometer of hybrid La0.7Sr0.3MnO3/Al2O3 (0.2 x 2 x 4 mm(3)) structure. The estimated thermal resistance of the bulk ceramic manganite film-single crystal sapphire interface is about 500 K/W at room temperature. This resistance is the main thermal barrier in the heat sink system and has been found to be slightly dependent on temperature, When compared with the high-ire superconducting bolometers, the La0.7Sr0.3MnO3 microwave electroceramic bolometer works in a more wide temperature range, from 77 K to 330 K, excluding the narrow temperature interval at the metal-insulator phase transition (T = 230 K). The microwave electroceramic bolometer sensitivity and the time constant at room temperature have been found to be 0.1 V/W and 100 ms, respectively. To improve the bolometer performance the point contact has been fabricated by a break junction technique. The optimization of a microwave electroceramic bolometer design brought to a considerable improvement of basic bolometer characteristics. The microwave sensitivity was about 0.3 V/W and the time constant was less than 100 ns.
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33.
  • Schuisky, M., et al. (författare)
  • Ferroelectric Bi4Ti3O12 thin films on Pt-coated silicon by halide chemical vapor deposition
  • 2000
  • Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 88:5, s. 2819-2824
  • Tidskriftsartikel (refereegranskat)abstract
    • A halide chemical vapor deposition technique has been developed to grow highly c-axis oriented submicron Bi4Ti3O12 films onto Pt(200 nm)/Ti(20 nm)/SiO2(1200 nm)/Si(100) substrates. BiI3, TiI4, and oxygen were used as precursors. The total gas pressure was found to be the critical processing parameter to grow films with good crystalline and dielectric properties. The 300 nm thick Bi4Ti3O12 films fabricated at 700 degrees C and total gas pressure of 3.8 Torr exhibit the best dielectric performance: dielectric constant around 200 and loss tan delta similar to 0.018 at 100 kHz, remnant polarization of 5.3 mu C/cm(2), induced polarization of 14.9 mu C/cm(2) at 560 kV/cm, coercive field of 150 kV/cm, electrical tunability of 51% at 350 kV/cm, resistivity of 2x10(9) Omega cm, and leakage current as low as 3x10(-5) A/cm(2) at 100 kV/cm. The effect of weak reduction of the remnant polarization and coercive field has been observed in the temperature range from 300 to 77 K and ascribed to the in-plane orientation of the polar a axis in fabricated Bi4Ti3O12 films.
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34.
  • Vieitez, M. O., et al. (författare)
  • Electro-optic properties of heteroepitaxial Pb(Zr,Ti)O-3/La0.5Sr0.5CoO3 film structures
  • 2003
  • Ingår i: Integrated Ferroelectrics. - 1058-4587 .- 1607-8489. ; 54, s. 607-618
  • Tidskriftsartikel (refereegranskat)abstract
    • Vertical ferroelectric Pb(Zr,Ti)O-3 (PZT) 1 mum thick film capacitor was fabricated by pulsed laser deposition technique (PLD) onto conducting La-0.5 Sr-0.5 CoO3 (LSCO) 100 nm thick bottom electrode on both side polished YAlO 3 + 1% Nd2O3 (Nd:YAlO3) single crystal substrate to operate as a Pockels cell optical modulator. On top of the PZT film, semitransparent 30 nm thick Au electrode was deposited by thermal evaporation. Intensity of the chopped 670 nm polarized laser radiation transmitted through the Au/PZT/LSCO/Nd:YAlO3 cell was measured at various temperatures and bias voltage applied. Applying 20 V (200 kV/cm) across the capacitive cell, modulation of the transmitted light as high as 3% was achieved while the voltage tunability measured at 1 kHz from C - V characteristics was about 70%. Thermo-optical measurements performed for PZT/Nd:YAlO3 sample in the range up to 400degreesC showed the phenomenon of critical opalescence in the vicinity of Curie temperature at 208degreesC. Optical transmission through the PZT film biased with electric field was studied in the range 400 to 1000 nm. Film thickness, refraction index and absorption coefficient have been determined from the interference pattern observed in the PZT transmission spectrum. A simple model yields the dispersion relation for the electro-optic coefficient.
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35.
  • Yuzvyuk, M. H., et al. (författare)
  • Processing of ultra-hard coatings based on AlMgB14 films
  • 2016
  • Ingår i: 18th International Conference PhysicA.SPb26–29 October 2015, Saint Petersburg, Russian Federation. - : Institute of Physics Publishing (IOPP).
  • Konferensbidrag (refereegranskat)abstract
    • First time AlMgB14 films were prepared in Ames Lab by pulsed laser deposition technique. In this work, RF magnetron sputtering from a single stoichiometric target was employed to fabricate hard AlMgB14 coatings on Si wafer and industrial items. Measurements of nanohardness and elastic Young's modulus were performed to determine reliable strength characteristics of samples. Smooth 3 μm thick AlMgB14 films with the RMS surface roughness to be less than 1 nm exhibit hardness of 34 GPa and modulus of elasticity of 230 GPa at 20 mN peak load.
  •  
36.
  • Östling, Mikael, et al. (författare)
  • Ferroelectric thin films on silicon carbide for next-generation nonvolatile memory and sensor devices
  • 2004
  • Ingår i: Thin Solid Films. - : Elsevier BV. - 0040-6090 .- 1879-2731. ; 469-70, s. 444-449
  • Tidskriftsartikel (refereegranskat)abstract
    • Silicon carbide semiconductor technology has emerged as a very good candidate to replace traditional Si devices in special applications such as low loss power switching and high temperature electronics. Ferroelectric thin films exhibit interesting properties for use in semiconductor technology due to the spontaneous polarization which can be switched by an externally applied electric field, and thus are attractive for nonvolatile memory and sensor applications. In this work, the successful realization of ferroelectric thin films in SiC devices is described. The first experimental prototype devices are presented and discussed: A novel integration technique of junction metal-oxide-semiconductor field effect transistors (JMOSFETs) and nonvolatile FETs (NVFETs) on a single 4H-SiC substrate is presented. A constant current control device is based on the SiC JMOSFET. The drain current is effectively controlled and kept constant by a buried junction gate. A new high temperature SiC NVFET with a similar temperature stable current drive is also demonstrated. The nonvolatile memory device, based on the ferroelectric gate stack, was shown to operate up to 300 C with memory effect retained up to 200degreesC.
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37.
  • Abadei, S., et al. (författare)
  • Low-frequency and microwave performances of laser-ablated epitaxial Na0.5K0.5NbO3 films on high-resistivity SiO2/Si substrates
  • 2002
  • Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 91:4, s. 2267-2276
  • Tidskriftsartikel (refereegranskat)abstract
    • The dielectric properties of laser-ablated 0.5-mum-thick c-axis epitaxial Na0.5K0.5NbO3 (NKN) films on high-resistivity (>7.7 kOmega cm) silicon SiO2/Si substrates are studied experimentally in the temperature interval of 30-320 K and at frequencies of 1.0 MHz-40 GHz. The films are grown by laser ablation from a stoichiometric target. For the measurements, planar 0.5-mum-thick gold electrodes (interdigital and straight slot) are photolithography defined on the top surface of NKN films. The slot width between the electrodes is 2.0 or 4.0 mum. At low frequencies (f<1.0 GHz), the structure performance is that of a typical metal-dielectric-semiconductor type, where two of this type of capacitor are connected back to back. At these frequencies, the large change in the capacitance (more than 10 times at 1.0 MHz), due to the applied dc field, is mainly due to the changes in depletion layer thickness at the surface of silicon. The associated losses are also large, tan delta>1. At microwave frequencies (f>10 GHz), the voltage dependence of the capacitance is given by the NKN film. More than a 13% capacitance change at 40 V dc bias and a Q factor of more than 15 are observed at 40 GHz, which make the structure useful for applications in electrically tunable millimeter-wave devices.
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38.
  • Achanta, S., et al. (författare)
  • On the mechanical and tribological behavior of Al3Mg2 complex metallic alloys as bulk material and as coating
  • 2010
  • Ingår i: Intermetallics (Barking). - : Elsevier BV. - 0966-9795 .- 1879-0216. ; 18:11, s. 2096-2104
  • Tidskriftsartikel (refereegranskat)abstract
    • New materials with tunable physical, mechanical, chemical, and thermal properties are attractive for many applications and stand as prospective substitutes for the existing engineering materials. In that respect, complex metallic alloys (CMA) have recently demonstrated promising traits where a myriad of physical, mechanical, chemical properties can be obtained by altering the structure. CMA's have a large crystal size with thousands of atoms per unit cell. In this work, some mechanical properties and tribological behavior of Al3Mg2 based CMA are discussed. The surface characterization, deformation mode, mechanical and tribological properties of bulk and thin film Al3Mg2 materials are investigated, and compared with existing engineering materials. The results revealed a contrasting tribological behavior of Al3Mg2 when used as either bulk material or as coating. Al3Mg2 coatings act as a low friction solid lubricant under certain conditions, with a coefficient of friction comparable to that of diamond-like carbon coatings. It is suggested that the quasi-crystalline nature of Al3Mg2-coatings renders the surface stiff and that the characteristics of the wear debris generated are responsible for the low friction behavior.
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39.
  • Adachi, N., et al. (författare)
  • Epitaxial Bi3Fe5O12(001) films grown by pulsed laser deposition and reactive ion beam sputtering techniques
  • 2000
  • Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 88:5, s. 2734-2739
  • Tidskriftsartikel (refereegranskat)abstract
    • We report on processing and comparative characterization of epitaxial Bi3Fe5O12 (BIG) films grown onto Gd-3(ScGa)(5)O-12[GSGG,(001)] single crystal using pulsed laser deposition (PLD) and reactive ion beam sputtering (RIBS) techniques. A very high deposition rate of about 0.8 mu m/h has been achieved in the PLD process. Comprehensive x-ray diffraction analyses reveal epitaxial quality both of the films: they are single phase, exclusively (001) oriented, the full width at half maximum of the rocking curve of (004) Bragg reflection is 0.06 deg for PLD and 0.05 deg for RIBS film, strongly in-plane textured with cube-on-cube film-to-substrate epitaxial relationship. Saturation magnetization 4 pi M-s and Faraday rotation at 635 nm were found to be 1400 Gs and -7.8 deg/mu m in PLD-BIG, and 1200 Gs and -6.9 deg/mu m in RIBS-BIG. Ferromagnetic resonance (FMR) measurements performed at 9.25 GHz yielded the gyromagnetic ratio gamma=1.797x10(7) l/s Oe, 1.826x10(7) l/s Oe; the constants of uniaxial magnetic anisotropy were K-u(*)=-8.66x10(4) erg/cm(3), -8.60x10(4) erg/cm(3); the cubic magnetic anisotropy K-1=-2.7x10(3) erg/cm(3),-3.8x10(3) erg/cm(3); and the FMR linewidth Delta H=25 and 34 Oe for PLD and RIBS films correspondingly. High Faraday rotation, low microwave loss, and low coercive field less than or equal to 40 Oe of BIG/GSGG(001) films promise their use in integrated magneto-optic applications.
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40.
  • Artemov, A. N., et al. (författare)
  • Large effect of thermal processes on the susceptibility of YBCO film with transport current
  • 2004
  • Ingår i: Physica. C, Superconductivity. - : Elsevier BV. - 0921-4534 .- 1873-2143. ; 403:3, s. 157-162
  • Tidskriftsartikel (refereegranskat)abstract
    • The response of YBCO film with transport current to the weak alternating magnetic field was studied. The hysteresis of the temperature dependences of the response measured under cooling and heating was revealed. The qualitative explanation of this phenomenon is proposed. It is based on the fact that under certain conditions the superconductor with transport current has two steady states. It is found that the hysteresis arises only if transport current exceeds some finite value I-0.
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41.
  • 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.
  •  
42.
  • Blomqvist, Mats, 1974- (författare)
  • Electro-Optical Na0.5K0.5NbO3 Films
  • 2005
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • 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.
  •  
43.
  • 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.
  •  
44.
  • Blomqvist, Mats, et al. (författare)
  • Optical waveguiding in magnetron-sputtered Na0.5K0.5NbO3 thin films on sapphire substrates
  • 2003
  • Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 82:3, s. 439-441
  • Tidskriftsartikel (refereegranskat)abstract
    • 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.
  •  
45.
  • Blomqvist, Mats, et al. (författare)
  • Rf-magnetron sputtered ferroelectric (Na,K)NbO3 films
  • 2002
  • Ingår i: Proceedings of the 13th IEEE International Symposium on Applications of Ferroelectronics. - 0780374142 ; , s. 195-198
  • Konferensbidrag (refereegranskat)abstract
    • 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.
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46.
  • Blomqvist, Mats, et al. (författare)
  • Rf sputtered Na0.5K0.5NbO3 films on oxide substrates as optical waveguiding material
  • 2003
  • Ingår i: Integrated Ferroelectrics. - : Informa UK Limited. - 1058-4587 .- 1607-8489. ; 54, s. 631-640
  • Tidskriftsartikel (refereegranskat)abstract
    • Highly crystalline Na0.5K0.5NbO3 (NKN) thin films of 1-2 mum thickness were deposited by rf-magnetron sputtering of a stoichiometric, ceramic target on single crystal LaAlO3 (001) and Al2O3 (01 (1) under bar2) substrates. X-ray diffraction measurements revealed epitaxial quality of NKN/LaAlO3 film structures, whereas NKN films on sapphire substrates were found to be preferentially c -axis oriented. A prism-coupling technique was used to characterize optical and waveguiding properties. A bright-line spectrum at lambda = 632.8 nm, revealed sharp peaks, corresponding to transverse magnetic (TM) and electric (TE) waveguide propagation modes in NKN/LaAlO3 and NKN/Al2O3 thin films. Using a least mean square fit the refractive index for the films and film thickness were calculated. The extraordinary and ordinary refractive indices were determined to n(e) = 2.207 +/- 0.002 and n(o) = 2.261 +/- 0.002, and n(e) = 2.216 +/- 0.002 and n(o) = 2.247 +/- 0.002 at lambda = 632.8 nm for 2.0 mum thick NKN films on LaAlO3 and Al2O3 , respectively. This corresponds to a birefringence Deltan = n(e) - n(o) = -0.054 +/- 0.003 and Deltan = -0.031 +/- 0.003 in the films, where the larger Deltan for the NKN/LaAlO3 structure can be explained by the superior crystalline quality compared to NKN/Al2O3 . Atomic force microscopy images of the film surfaces revealed rms roughnesses of 2.5 nm and 8.0 nm for 1.0-mum thick NKN/LaAlO3 and NKN/Al2O3 films, respectively. We believe surface scattering is one of the main sources of waveguide losses in the thin films.
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47.
  • 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.
  •  
48.
  • Brunahl, J., et al. (författare)
  • Non-destructive pulsed technique to characterize functional properties of micromachined bulk PZT
  • 2001
  • Ingår i: Ferroelectrics (Print). - 0015-0193 .- 1563-5112. ; 263:1-4, s. 1487-1492
  • Tidskriftsartikel (refereegranskat)abstract
    • In this report, a non-destructive pulsed technique is presented to characterize all relevant properties of machined bulk PZT material. The proposed method is based on recording of the transient current as response on the short voltage pulse applied to the ferroelectric acoustic element. This new promising experimental technique makes it possible to measure mechanical and electrical properties fast, reliably and reproducibly. Among other results we can obtain electromechanical coupling coefficient, dielectric loss factor tan 8, mechanical quality factor Q, dielectric constant, capacitance, resonant frequency and Curie temperature T-c. The temperature dependence of above mentioned parameters can be studied as well very easily.
  •  
49.
  • Brunahl, J., et al. (författare)
  • Piezoelectric shear mode drop-on-demand inkjet actuator
  • 2002
  • Ingår i: Sensors and Actuators A-Physical. - 0924-4247 .- 1873-3069. ; 101:3, s. 371-382
  • Tidskriftsartikel (refereegranskat)abstract
    • We report on comprehensive characterization of piezoelectric shear mode inkjet actuators micromachined into bulk Pb(Zr0.53Ti0.47)O-3 (PZT) ceramics. The paper starts with an overview of different drop-on-demand inkjet systems, whereas the main attention is then turned on particular Xaar-type piezoelectric shear mode inkjet printheads. They are an example of complex microelectromechanical system (MEMS) and comprise a ferroelectric array of 128 active ink channels (75 mum wide and 360 mum deep). Detailed information about fabrication process and principles of operation are given. Since each actuating wall of 128 channels is a piezoelectric capacitor metallized from both sides to be animated by electric pulse, electrical properties of channel walls (CWs) are easy to test and serve as a fingerprint of actuator performance in the virgin state as well as after high voltage/elevated temperature heavy duties. We present several techniques to control manufacturing process and fatigue effects. So, continuous wave and pulsed spectroscopy and hysteresis P-E loop tracing showed that compared to a virgin PZT ceramics state, dielectric permittivity (epsilon') was reduced three times, the loss factor (tan delta) increased from initial 4.8 to 6.6%, remnant polarization decreased by 43%, coercive field increased by 38%, whereas Curie temperature increased from 508 to 560 K after 90,000 cycles of ferroelectric hysteresis P-E loop tracing at 50 Hz at electric field of 88.5 kV/cm. Heat treatment also results in PZT ceramics degradation: appreciable reduction of the coupling coefficient (k(15)) and the degradation of inkjet performance were revealed by optical stroboscope technique: 8.7 and 14% reduction of drop velocity and volume in electrically fatigued actuator, 2.5% reduction of drop velocity and unchanged drop volume in temperature-treated actuators.
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50.
  • Cho, C. R., et al. (författare)
  • Background oxygen effects on pulsed laser deposited Na0.5K0.5NbO3 films : From superparaelectric state to ferroelectricity
  • 2000
  • Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 87:9, s. 4439-4448
  • Tidskriftsartikel (refereegranskat)abstract
    • Ambient oxygen pressure in a pulsed laser deposition process has been observed to have a critical influence on the compositional, crystalline, and electrical properties of Na0.5K0.5NbO3 (NKN) thin films grown onto polycrystalline Pt80Ir20 and SiO2 (native oxide)/Si(111) substrates. Films prepared at high oxygen pressure (similar to 400 mTorr) were found to be single phase and highly c-axis oriented. X-ray diffraction theta-2 theta scans and rocking curve data show a strong effect of NKN film self-assembling along the [001] direction regardless of the substrate texture. The high dielectric permittivity of 550, low dissipation factor of less than 3%, and high remanent polarization of 12 mu C/cm(2) indicate the high ferroelectric quality of the fabricated film. The role of the high-energy component of the erosion products has been proven to be crucial to film performance. On the other hand, films grown at low oxygen pressure (similar to 10 mTorr) have been found to be mixed phases of ferroelectric NKN and paraelectric potassium niobates. These films have shown superparaelectric behavior: 5% tunability at an electric field of 100 kV/cm, losses as low as 0.3%, and excellent stability to temperature and frequency changes.
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