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  • 1.
    Blomqvist, Mats
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Khartsev, Sergiy
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Materialfysik, MF.
    Grishin, Alexander M.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Electro-optic effect in ferroelectric Na0.5K0.5NbO3 thin films on oxide substrates2006Ingår i: Integrated Ferroelectrics, ISSN 1058-4587, E-ISSN 1607-8489, Vol. 80, nr 1, s. 97-106Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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.

  • 2.
    Blomqvist, Mats
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Khartsev, Sergiy
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Materialfysik, MF.
    Grishin, Alexander M.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Visible and IR light waveguiding in ferroelectric Na0.5K0.5NbO3 thin films2005Ingår i: Integrated Ferroelectrics, ISSN 1058-4587, E-ISSN 1607-8489, Vol. 69, s. 277-286Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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.

  • 3.
    Blomqvist, Mats
    et al.
    KTH, Tidigare Institutioner                               , Mikroelektronik och informationsteknik, IMIT.
    Khartsev, Sergiy
    KTH, Tidigare Institutioner                               , Mikroelektronik och informationsteknik, IMIT.
    Grishin, Alexander M.
    KTH, Tidigare Institutioner                               , Mikroelektronik och informationsteknik, IMIT.
    Petraru, Adrian
    Institute of Thin Films and Interfaces, Section: Ion Technology, Forschungzentrum Jülich.
    Rf sputtered Na0.5K0.5NbO3 films on oxide substrates as optical waveguiding material2003Ingår i: Integrated Ferroelectrics, ISSN 1058-4587, E-ISSN 1607-8489, Vol. 54, s. 631-640Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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.

  • 4. Cho, C. R.
    et al.
    Grishin, Alexander M.
    KTH, Tidigare Institutioner                               , Mikroelektronik och informationsteknik, IMIT.
    Thickness dependent performance of Na0.5K0.5NbO3/sapphire thin film varactors2001Ingår i: Integrated Ferroelectrics, ISSN 1058-4587, E-ISSN 1607-8489, Vol. 39, nr 1-4, s. 1353-1360Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Perfect c-axis oriented Na0.5K0.5NbO3 (NKN) films have been pulsed laser deposited on Al2O3(01 (1) under bar2) single crystals (r-cut sapphire) for voltage tunable microwave device applications. Thickness dependence of dielectric performance of the NKN/sapphire interdigital capacitors (IDCs) has been studied. 40 V bias tunability and dielectric loss tandelta of 4 burr slot IDCs have been found to be 24.6 % and 2.86 % for 1.2 mum thick NKN film, and 6.1 % and 0.83 % for 0.14 mum thick NKN film, respectively. Low leakage currents and high breakdown voltages are observed in these structures.

  • 5. Cho, C. R.
    et al.
    Grishin, Alexander M.
    KTH, Tidigare Institutioner                               , Mikroelektronik och informationsteknik, IMIT.
    Moon, B. M.
    Ferroelectric Na0.5K0.5NbO3 thin films by pulsed laser deposition2000Ingår i: Integrated Ferroelectrics, ISSN 1058-4587, E-ISSN 1607-8489, Vol. 31, nr 1-4, s. 35-45Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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.

  • 6. Cho, C. R.
    et al.
    Park, S. H.
    Moon, B. M.
    Sundqvist, J.
    Harsta, A.
    Grishin, Alexander M.
    KTH, Tidigare Institutioner                               , Mikroelektronik och informationsteknik, IMIT.
    Na0.5K0.5NbO3 thin films for MFIS_FET type non-volatile memory applications2002Ingår i: Integrated Ferroelectrics, ISSN 1058-4587, E-ISSN 1607-8489, Vol. 49, s. 21-30Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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.

  • 7.
    Grishin, Alexander M.
    et al.
    KTH, Tidigare Institutioner                               , Mikroelektronik och informationsteknik, IMIT.
    Khartsev, Sergiy
    KTH, Tidigare Institutioner                               , Mikroelektronik och informationsteknik, IMIT.
    Kim, Joo-Hyung
    KTH, Tidigare Institutioner                               , Mikroelektronik och informationsteknik, IMIT.
    Lu, J.
    Epitaxial colossal magnetoresistive/ferroelectric heterostructures on Si2004Ingår i: Integrated Ferroelectrics, ISSN 1058-4587, E-ISSN 1607-8489, Vol. 67, s. 69-76Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We report on processing and properties of La-0.67(SrCa)(0.33)MnO3 (LSCMO) films grown by pulsed laser deposition technique on Si(001) substrates buffered with Bi4Ti3O12/CeO2/YSZ heteroepitaxial layers. X-ray diffraction shows cube-on-cube growth of epitaxial Bi4Ti3O12/CeO2/YSZ/Si heterostructure whereas the LSCMO layer grows in the diagonal-on-side manner onto the Bi4Ti3O12 (BTO) template. High resolution TEM images demonstrate sharp interfaces between the buffer layers and LSCMO film as well as rare misfit dislocations on the CeO2/YSZ interface. LSCMO film processing conditions have been optimized to get maximum temperature coefficient of resistivity TCR = 4.4% K-1 and colossal magnetoresistance (CMR) Deltarho/rho similar to 2.9% kOe(-1) @ 294 K. Almost ultimate CMR performance at room temperature has been achieved due to successive improvement of c-axis orientation of layers: full widths at half-maximum (FWHM) = 0.65, 0.58, 0.65, 1.13 and 0.18 degrees in LSCMO/BTO/CeO2/YSZ/Si stack, respectively. Characterization of electrical noise in CMR film yields Noise Equivalent Temperature Difference (NETD) as low as 1.2 muK/rootHz @ 30 Hz and 294 K.

  • 8.
    Grishin, Michael A.
    et al.
    KTH, Tidigare Institutioner                               , Mikroelektronik och informationsteknik, IMIT.
    Grishin, Alexander M.
    KTH, Tidigare Institutioner                               , Mikroelektronik och informationsteknik, IMIT.
    Khartsev, Sergiy
    KTH, Tidigare Institutioner                               , Mikroelektronik och informationsteknik, IMIT.
    Karlsson, Ulf O.
    KTH, Tidigare Institutioner                               , Mikroelektronik och informationsteknik, IMIT.
    High performance films of binary system SrTiO3-PbZr0.52Ti0.48O3 on sapphire2001Ingår i: Integrated Ferroelectrics, ISSN 1058-4587, E-ISSN 1607-8489, Vol. 39, nr 1-4, s. 351-358Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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.

  • 9.
    Khartsev, Sergiy
    et al.
    KTH, Tidigare Institutioner                               , Mikroelektronik och informationsteknik, IMIT.
    Grishin, Alexander M.
    KTH, Tidigare Institutioner                               , Mikroelektronik och informationsteknik, IMIT.
    Andreasson, J.
    Koh, J. H.
    Song, J. S.
    Comparative characteristics of Na0.5K0.5NbO3 films on Pt by pulsed laser deposition and magnetron sputtering2003Ingår i: Integrated Ferroelectrics, ISSN 1058-4587, E-ISSN 1607-8489, Vol. 55, s. 769-779Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Ferroelectric Na0.5K0.5 NbO3 (NKN) thin films were grown on the Pt 80 Ir 20 polycrystalline substrates by pulsed laser deposition (PLD) and radio frequency-magnetron sputtering (RF) technique using the same stoichiometric Na0.5K0.5NbO3 ceramic target. X-ray diffraction proved both PLD- and RF-made Na0.5K0.5 NbO3/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 410degreesC. Capacitance vs. applied voltage C-V @ 100 kHz, I-V , and P-E hysteresis characteristics recorded for the vertical capacitive structures yielded loss tandelta = 0.026 and 0.016, tunability about 44.5 and 30% @ 100 kV/cm, Ohmic resistivity 6.7 x 10(12) Omega.cm and 0.2 x 10(12) Omega.cm, remnant polarization 11.7 and 9.7 muC/cm(2) , 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 d H = 21 for PLD-NKN and 15 pC/N for RF-NKN film.

  • 10.
    Khartsev, Sergiy
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Grishin, Michael A.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Grishin, Alexander M.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Karlsson, Ulf O.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Heteroepitaxial Na0.5K0.5NbO3/La0.5Sr0.5CoO3 electro-optical cell2006Ingår i: Integrated Ferroelectrics, ISSN 1058-4587, E-ISSN 1607-8489, Vol. 80, s. 133-143Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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.

  • 11.
    Kim, Jang-Yong
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Grishin, Alexander M.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    AgTa0.5Nb0.5O3 thin film coplanar waveguide microwave capacitors2005Ingår i: Integrated Ferroelectrics, ISSN 1058-4587, E-ISSN 1607-8489, Vol. 77, s. 13-20Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    400 nm thick AgTa0.5Nb0.5O3 (ATN) films have been prepared by pulsed laser depositiontechnique on LaAlO3 (001) and sapphire (Al2O3-0112, r -cut) single crystal substrates.Comprehensive X-ray diffraction analysis showed epitaxial quality of ATN/LaAlO3films and preferentially (001) orientation of ATN/Al2O3 films. Voltage tunable microwavecapacitors were fabricated by lift-off technique on the surface of ferroelectricfilms. Microwave on-wafer tests were performed in the range from 1 to 40 GHz. Frequencydispersion is about 4.3%, voltage tunability is 4.7% @ 20 GHz and 200 kV/cm,loss tangent ∼0.068 @ 20 GHz, K-factor=tunability/tanδ is ranged from 124% @10 GHz to 35% @ 40 GHz.

  • 12.
    Kim, Jang-Yong
    et al.
    KTH, Tidigare Institutioner                               , Mikroelektronik och informationsteknik, IMIT.
    Grishin, Alexander M.
    KTH, Tidigare Institutioner                               , Mikroelektronik och informationsteknik, IMIT.
    Na0.5K0.5NbO3 film microwave varactors2004Ingår i: Integrated Ferroelectrics, ISSN 1058-4587, E-ISSN 1607-8489, Vol. 66, s. 291-300Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Na0.5K0.5NbO3 (NKN) and Pb(Zr 0.53Ti0.47)O3 (PZT) films have been grown by rf-magnetron sputtering and pulsed laser deposition techniques, correspondingly, on sapphire (Al2O3-0112, r-cut), quartz (Y + 36°-cut) and YAlO3 + 1%Nd(Nd:YAlO3-001) single crystal substrates with Interdigital Capacitor (IDC) of Coplanar Waveguide (CPW) structure. Photolithography and metal lift-off technique was used for processing of the tunable microwave capacitor. Microwave network analyzer with G-S-G Picoprobe and probe station performed microsvave measurement with external DC bias. NKN film interdigital capacitors on Nd:YAlO3 show superior performance in the microwave range from 1 to 40 GHz. Within this range, the voltage tunability (40 V, 200 kV/cm) was about 29%, loss tangent ∼0.13, K-factor from 152% @10 GHz to 46% @40 GHz, voltage independent Cp was about 230 fF, tan δp changes from 0.14 @ 10 GHz to 0.36 @40 GHz, real and imaginary part of interconnect impedance increases with frequency from 0.13 Ω@ 10 GHz to 0.50 Ω @40 GHz and from 1.9 Ω@10 GHz to 5.9 Ω @40 GHz respectively.

  • 13.
    Kim, Joo-Hyung
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Grishin, Alexander M.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik.
    Microfabrication of epitaxial La1-x(Sr,Ca)(x)MnO3 IR bolometer on Si2006Ingår i: Integrated Ferroelectrics, ISSN 1058-4587, E-ISSN 1607-8489, Vol. 80, s. 47-54Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Self supported free standing heteroepitaxial La1-x(Sr,Ca)(x)MnO3 (LSCMO) membranes grown on Bi4Ti3O12(BTO)/CeO2/YSZ buffered Si substrates have been microfabricated by Ar ion beam etching (IBE) and SF6/C4F8 inductively Coupled plasma (ICP) etching technique. The electrical property of free standing membrane was compared to as-grown sample by four point measurement. These results demonstrate feasibility to use heteroepitaxial oxide film structures with conventional photoresist patterning as thermally isolated membranes for infrared microbolometers.

  • 14. Koh, J. H.
    et al.
    Grishin, Alexander M.
    KTH, Tidigare Institutioner                               , Mikroelektronik och informationsteknik, IMIT.
    Electrically tunable Ag(Ta,Nb)O-3 thin film structures on oxide substrates2001Ingår i: Integrated Ferroelectrics, ISSN 1058-4587, E-ISSN 1607-8489, Vol. 39, nr 1-4, s. 1281-1288Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We report on design, fabrication, and comparative test of three different types of voltage-variable interdigital capacitors made on ferroelectric Ag(Ta,Nb)O-3 films deposited on MgO and Al2O3 substrates. X-ray diffraction patterns show that ATN films pulsed laser deposited on MgO(001) and Al2O3(01 (1) under bar2) single crystals have preferential (00l) and (0kk) orientation. Capacitance and loss tangent in interdigital capacitors were measured as the functions of frequency and applied dc voltage bias, Loss tangent was as low as 0.0025 and 0.0034 and K-factor (tunability/tandelta) was around 26.2 and 20.0 for MgO and Al2O3, respectively, @ +/- 40 V (maximum electric field 200 kV/cm), 300 K, and I MHz. Both of polarization and steady leakage currents were observed in the current-time domain measurements. 0.1 pF interdigital capacitors have pA leakage current level @ +/- 40 V.

  • 15. Koh, J. H.
    et al.
    Moon, B. M.
    Grishin, Alexander M.
    KTH, Tidigare Institutioner                               , Mikroelektronik och informationsteknik, IMIT.
    Dielectric properties and Schottky barriers in silver tantalate-niobate thin film capacitors2001Ingår i: Integrated Ferroelectrics, ISSN 1058-4587, E-ISSN 1607-8489, Vol. 39, nr 1-4, s. 1361-1368Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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.

  • 16. Koo, S. M.
    et al.
    Khartsev, Sergiy
    KTH, Tidigare Institutioner                               , Mikroelektronik och informationsteknik, IMIT.
    Zetterling, Carl-Mikael
    KTH, Tidigare Institutioner                               , Mikroelektronik och informationsteknik, IMIT.
    Grishin, Alexander M.
    KTH, Tidigare Institutioner                               , Mikroelektronik och informationsteknik, IMIT.
    Östling, Mikael
    KTH, Tidigare Institutioner                               , Mikroelektronik och informationsteknik, IMIT.
    Processing and properties of ferroelectric Pb(Zr,Ti)O-3/silicon carbide field-effect transistor2003Ingår i: Integrated Ferroelectrics, ISSN 1058-4587, E-ISSN 1607-8489, Vol. 57, s. 1221-1231Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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.

  • 17. Liang, Yujie
    et al.
    Liu, Zhifu
    Cheng, Yao
    Zhao, Zhe
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Seeded growth of WO3 film on FTO substrate with tunable structures for stable electrochromic performance2016Ingår i: Integrated Ferroelectrics, ISSN 1058-4587, E-ISSN 1607-8489, Vol. 173, nr 1, s. 109-116Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this work, tungsten trioxide (WO3) film was prepared on FTO-coated glass substrates using a facile hydrothermal method. Detailed studies revealed that a variety of WO3 nanostructures-including nanosheets, nanoflakes, nanocuboids and 3D nanowire flowers could be obtained by tuning the composition of the precursor solution, where the additive ((NH4)(2)C2O4 and CO(NH2)(2)-(NH4)(2)C2O4)) content and solvent composition played important roles in controlling the shape and size of the WO3. These nanostructure films exhibited good electrochromic performance. The transmittance spectra showed that WO3 film displayed 50% and 70% in the range of visible light at the colored and bleached states (S2) and a potential of +/- 1.0V. There is no significant degradation of the electrochromic properties after 1000 continuous coloration/bleaching cycles, making it attractive for practical applications.

  • 18. Lisauskas, A.
    et al.
    Khartsev, Sergiy
    KTH, Tidigare Institutioner                               , Mikroelektronik och informationsteknik, IMIT.
    Grishin, Alexander M.
    KTH, Tidigare Institutioner                               , Mikroelektronik och informationsteknik, IMIT.
    Impedance fluctuations in epitaxial PZT films2001Ingår i: Integrated Ferroelectrics, ISSN 1058-4587, E-ISSN 1607-8489, Vol. 38, nr 04-jan, s. 647-656Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We report on measurements of impedance of Au/PZT/La0.67Sr0.33MnO3/Pt80Ir20 thin film capacitors performed in the time domain. Ferroelectric PZT films pulsed laser deposited on bulk polycrystalline Pt80Ir20 substrates demonstrate good ferroelectric properties: dielectric permittivity epsilon' = 880 and loss tandelta = 0.039 at 1 kHz, remnant polarization as high as 20 muC/cm(2), induced polarization of 40 muC/cm(3) at 380 kV/cm, and coercive field of 52.5 kV/cm. Resistivity of PZT film at coercive field was found to be 3.10(12) Omega.cm. Instantaneous C-V and I-V characteristics have been recorded to study the relaxation of polarization. Transient current exhibits non-Debye type relaxation, which has been nicely fitted to Curie-von Schweindler law j = j(leak) + j(o) (t/1sec)(-n) with an exponent nsimilar to0.8 while the power law C proportional to f(-0.1) has been found in frequency dispersion of the capacitance. Impedance fluctuation spectrum in the true leakage and resistance degradation regimes was found to follow 1/f(1.5) dependence. Close to breakdown field voltage fluctuations in ferroelectric capacitor increase, become non-steady randomly spike-shaped.

  • 19. Muduli, P. K.
    et al.
    Pogoryelov, Ye.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Materialfysik, MF.
    Zhou, Y.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Materialfysik, MF.
    Mancoff, Fred
    Åkerman, Johan
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Materialfysik, MF.
    Spin Torque Oscillators and RF Currents-Modulation, Locking, and Ringing2011Ingår i: Integrated Ferroelectrics, ISSN 1058-4587, E-ISSN 1607-8489, Vol. 125, s. 147-154Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We study the interaction between a nano-contact spin torque oscillator (STO) and injected radio-frequency and microwave currents. Modulation of the STO signal is observed over a wide frequency range from 100 MHz to 3.2 GHz. The modulation side-bands agree well with macrospin simulations. When the injected microwave frequency approaches that of the STO, we observe injection locking, frequency pulling/pushing, and intermodulation peaks. While the intermodulation peaks are reasonably well reproduced by macrospin simulations, they do not follow the Adler's model. We argue that this discrepancy is due to intrinsic ringing effects stemming from the internal dynamics of the STO.

  • 20. Popov, V.
    et al.
    Emmoth, Birger
    KTH, Tidigare Institutioner                               , Mikroelektronik och informationsteknik, IMIT.
    Grishin, Alexander M.
    KTH, Tidigare Institutioner                               , Mikroelektronik och informationsteknik, IMIT.
    Stytsenko, E.
    Ryan, M. J.
    Daglish, M.
    Morphology of PZT-PMN films grown from airflow2003Ingår i: Integrated Ferroelectrics, ISSN 1058-4587, E-ISSN 1607-8489, Vol. 54, s. 575-584Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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.

  • 21. Vieitez, M. O.
    et al.
    Khartsev, Sergiy
    KTH, Tidigare Institutioner                               , Mikroelektronik och informationsteknik, IMIT.
    Johnsson, P.
    Grishin, Alexander M.
    KTH, Tidigare Institutioner                               , Mikroelektronik och informationsteknik, IMIT.
    Electro-optic properties of heteroepitaxial Pb(Zr,Ti)O-3/La0.5Sr0.5CoO3 film structures2003Ingår i: Integrated Ferroelectrics, ISSN 1058-4587, E-ISSN 1607-8489, Vol. 54, s. 607-618Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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.

  • 22. Wang, Lichao
    et al.
    Ha, Minh Ngoc
    Liu, Zhifu
    Zhao, Zhe
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Mesoporous WO3 modified by Mo for enhancing reduction of CO2 to solar fuels under visible light and thermal conditions2016Ingår i: Integrated Ferroelectrics, ISSN 1058-4587, E-ISSN 1607-8489, Vol. 172, nr 1, s. 97-108Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Mesoporous WO3 (m-WO3) was synthesized by a hydrothermal method using mesoporous silica KIT-6 as a hard template and silicotungstic acid as a precursor. The m-WO3 modified by molybdenum (Mo) nanoparticles could be used as a stable catalyst for photo-thermal inducing CO2 reducting reactions for solar fuels. Under visible light irradiation (lambda > 420 nm) and 250-, the catalytic activity of m-Mo/WO3 for the CH4 and CH3 OHevolution was found to be higher than that of m-WO3 and commercial WO3. The amount of evolved CH3OH from m-Mo/WO3 has reached 13.80 mu molg(-1) in 1 2 h, which is ca. 10 times as high as that of c-WO3 (1.36 mu molg(-1)) and 6.5 times as high as that of m-WO3 (2.12 mu molg(-1)), making it attractive for practical applications.

  • 23.
    Zhang, Zhigang
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Kondenserade materiens teori.
    Grishini, Alex M.
    KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Kondenserade materiens teori.
    Characterization of piezoelectric shear mode inkjet actuator2005Ingår i: Integrated Ferroelectrics, ISSN 1058-4587, E-ISSN 1607-8489, Vol. 69, s. 401-+Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Impedance analysis was used to characterize the properties of Piezoelectric Shear Mode Inkjet Actuators. Ceramic actuators poled parallel to the channel walls exhibit good performance. Applying high voltage the actuators can be depolarized at high temperature or even re-poled perpendicular to the channel walls. This limits the drive pulse and the bias voltage below the coercive voltage. The leakage current also has been studied with various conditions. For the ferroelectric ceramic materials, the Schottky barrier also can be measured at definite voltage and temperature ranges, the corresponding Barrier for the Al/PZT contact is 0.98 eV. A pronounced low-temperature dielectric relaxation process was observed between 100-150 K; the relaxation rate fellows the Arrhenius law, the fitted activation energy is 0.194 eV. The resonance frequency increases as decreasing the temperature because of increasing for the stiffness coefficient at low temperature.

  • 24.
    Zhang, Zhigang
    et al.
    KTH, Tidigare Institutioner, Mikroelektronik och informationsteknik, IMIT.
    Khartsev, Sergiy
    KTH, Tidigare Institutioner, Mikroelektronik och informationsteknik, IMIT.
    Grishin, Alexander M.
    KTH, Tidigare Institutioner, Mikroelektronik och informationsteknik, IMIT.
    Ferroelectric properties of Na0.5K0.5NbO3 films at low temperatures2004Ingår i: Integrated Ferroelectrics, ISSN 1058-4587, E-ISSN 1607-8489, Vol. 67, s. 59-68Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The temperature dependence of polarization and dielectric behaviour of Na0.5K0.5NbO3 thin films were studied from 25 K to room temperature. NKN films were deposited on Pt80Ir20 substrates by RF-magnetron sputtering. The freezing of domain walls with decreasing temperature makes domain walls switching difficult and suppresses the domain walls vibration. Both saturation remanent polarization and coercive field increased with decreasing the temperature. A pronounced low-temperature dielectric relaxation process was observed below 100 K; the relaxation rate fellows the Arrhenius law. Low temperature dielectric behaviour has been studied for the NKN films at various frequencies and bias electrical fields. Constant phase element model is introduced and can interpret the dielectric behaviour well. Dielectric constant, ac conductivity, loss tangent and universal law dielectric equation can be easily deduced from our model. The measured loss tangent and fitted result at various temperature and bias electrical fields agreed very well for our NKN films.

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