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  • 1.
    Abadei, S.
    et al.
    Department of Microelectronics, Chalmers University of Technology, 412 96 Göteborg, Sweden.
    Gevorgian, S.
    Department of Microelectronics, Chalmers University of Technology, 412 96 Göteborg, Sweden, Core Unit Research Center, Ericsson Microwave Systems, SE-431 84, Mölnda, Sweden.
    Kugler, Veronika Mozhdeh
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Helmersson, Ulf
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics .
    Andreasson, J.
    Department of Materials and Manufacturing Engineering, Luleå University of Technology, 971 87, Luleå, Sweden.
    Microwave properties of tunable capacitors basee on magnetron sputtered ferroelectric Na0.5K0.5NbO3 film on low and high resistivity silicon substrates2001In: Integrated Ferroelectrics, ISSN 1058-4587, E-ISSN 1607-8489, Vol. 39, no 1-4, p. 359-366Conference paper (Other academic)
    Abstract [en]

    In this work, small signal DC voltage dependent dielectric permittivity, loss tangent, and tuneability of magnetron sputtered epitaxial Na0.5K0.5NO3 films are studied experimentally. (100)-oriented Na0.5K0.5NbO3 films are deposited onto SiO2-buffered CMOS grade low resistivity (p = 10-20 cm) and high resistivity (p = 15-45 kcm) silicon substrates. Planar capacitors with 2 or 4 m gaps between electrodes have been fabricated on top of ferroelectric films. These devices have been characterized in the frequency range 1.0 MHz to 50 GHz at temperatures 30 - 300K. Na0.5K0.5NbO3/SiO2/Si structures on high resistivity silicon substrate exhibit C-V performances typical for Metal-Insulator- Semiconductor (MIS) capacitors. At low frequencies, f 1.0 GHz, the large tuneability and large losses are associated with the MIS structure, while at higher microwave frequencies the tuneability is mainly associated with the ferroelectric, film. At 1.0 MHz and room temperature, the tuneability of Na0.5K0.5NbO3/SiO2/Si structures more than 90%, reducing to 10-15 % at 50 GHz. The losses decrease with increasing the DC bias and frequency. A Q-factor more than 15 at 50 GHz is observed. The dielectric permittivity of the Na0.5K0.5NbO3 film is in the range 50-150 at frequencies 0.045-50 GHz. On low resistivity substrate the performance of Na0.5K0.5NbO3 films is completely screened by the high losses in silicon, and the tuneability is negligible. © 2001 Taylor and Francis.

  • 2.
    Konofaos, N.
    et al.
    Department of Physics, University of Ioannina, P.O. Box 1186, 451 10 Ioannina, Greece.
    Evangelou, E.K.
    Department of Physics, University of Ioannina, P.O. Box 1186, 451 10 Ioannina, Greece.
    Wang, Z.
    Kugler, Veronika Mozhdeh
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Helmersson, Ulf
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics .
    Electrical characterisation of SrTiO3/Si interfaces2002In: Journal of Non-Crystalline Solids, ISSN 0022-3093, E-ISSN 1873-4812, Vol. 303, no 1, p. 185-189Article in journal (Refereed)
    Abstract [en]

    Deposition of SrTiO3 (STO) thin films by ultra-high vacuum rf magnetron sputtering was performed in order to produce high-quality STO/p-Si (1 0 0) interfaces and STO insulator layers with high dielectric constants. The deposition temperatures were in the range from room temperature to 550 °C. Capacitance-voltage (C-V) and conductance-frequency measurements showed that the dielectric constant of the films ranges from 55 to 120. C-V measurements on Al/STO/p-Si structures clearly revealed the creation of metal-insulator-semiconductor diodes. The interface state densities (Dit) at the STO/p-Si interfaces were obtained from admittance spectroscopy measurements. The samples deposited at lower temperatures revealed values of Dit between 2 × 1011 and 3.5 × 1012 eV-1 cm-2 while the higher temperature deposited samples had a higher Dit ranging between 1 × 1011 and 1 × 1013 eV-1 cm-2. The above results were also well correlated to X-ray diffraction measurements, Rutherford backscattering spectroscopy, and spectroscopic ellipsometry. © 2002 Elsevier Science Ltd. All rights reserved.

  • 3.
    Kugler, Veronika Mozhdeh
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Structure and properties of rf magnetron sputtered (Na,K)NbOx thin films2002Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Thin films of ferroelectric materials have attracted great interest for various applications, including non-volatile memory, infrared sensors, optical switches, and ultrasonic transducers. The perovskite sodium-potassium niobate is a material that has been known due to its ferroelectric and piezoelectric properties. Depending on growth conditions, thin films of (Na,K)NbOx (NKN) show high piezoelectric and dielectric constants, low losses (tan 8), and tunable properties, which makes them suitable for applications such as phase shifters, tunable filters and resonators, and electronic circuits. The aims of this work were to obtain a better understanding of the relation between process conditions, microstructure, and physical properties of NKN films and to optimize their electrical-, and mechanical properties. The results have contributed to understand the effects of deposition parameters, such as partial pressure of gases, argon and oxygen, and growth temperature on chemical composition and properties of the films.

  • 4.
    Kugler, Veronika Mozhdeh
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Söderlind, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Music, Denis
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Helmersson, Ulf
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, The Institute of Technology.
    Andreasson, J.
    Department of Materials Engineering, Luleå University of Technology, Luleå, Sweden.
    Lindback, T.
    Department of Materials Engineering, Luleå University of Technology, Luleå, Sweden.
    Low temperature growth and characterization of (Na,K)NbOx thin films2003In: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 254, no 3-4, p. 400-404Article in journal (Refereed)
    Abstract [en]

    Thin (Na,K)NbOx perovskite films (NKN) have been deposited on SiO2/Si(0 0 1) substrates at low temperatures, from 350°C to 550°C, by RF magnetron sputtering. The effects of substrate temperature on microstructure, electrical-, and mechanical properties of the NKN films have been studied. X-ray diffraction analysis revealed that films deposited at temperatures in the range of 450–550°C were crystalline, growing as a single phase, with a preferred orientation of (0 0 1). Films deposited at 350°C, were shown to be amorphous. The growth temperature had a strong influence on the electrical properties of the NKN films and the relative dielectric constants of the obtained films were in between 38 and 78. Variations of the mechanical properties of the NKN films were observed for different substrate temperatures: The elastic moduli and the hardness values ranged from 205±26 to 93±29 GPa, and from 12±2 to around 2 GPa, for films deposited at 550°C and 450°C, respectively.

  • 5.
    Kugler, Veronika Mozhdeh
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Söderlind, Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Music, Denis
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Helmersson, Ulf
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics.
    Andreasson, J.
    Department of Materials Engineering, Luleå University of Technology, Luleå, Sweden.
    Lindback, T.
    Department of Materials Engineering, Luleå University of Technology, Luleå, Sweden.
    Microstructure/dielectric property relationship of low temperature synthesised (Na,K)NbOx thin films2004In: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 262, no 1-4, p. 322-326Article in journal (Refereed)
    Abstract [en]

    Thin films of (Na,K)NbOx (NKN) were grown by reactive RF magnetron sputtering on polycrystalline Pt80Ir20 substrates, at relatively low growth temperatures between 300°C and 450°C. The results show that the electrical performance and the microstructure of the films are a strong function of the substrate temperature. X-ray diffraction of films grown up to 400°C revealed the formation of only one crystalline NKN-phase with a preferred (0 0 2)-orientation. However, a mixed orientation together with a secondary, paraelectric potassium niobate phase, were observed for NKN films deposited at 450°C. The differences in the microstructure explains the variations in the dielectric constants and losses: The single phase NKN films displayed a dielectric constant and a dielectric loss of 506 and 0.011, respectively, while the films with mixed phases exhibited values of 475 and 0.022, respectively. The possibility of fabricating NKN films with relatively high dielectric properties at low growth temperatures, as demonstrated here, is of high technological importance.

  • 6.
    Music, Denis
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Kugler, Veronika Mozhdeh
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Czigany, Zolt
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Flink, Axel
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Werner, Oskar
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Schneider, J.M.
    Materials Chemistry, RWTH Aachen.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Helmersson, Ulf
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Role of carbon in boron suboxide thin films2003In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, ISSN 0734-2101, E-ISSN 1520-8559, Vol. 21, no 4, p. 1355-1358Article in journal (Refereed)
    Abstract [en]

    X-ray amorphous BO0.02 thin films with the C content from 0 to 0.6 at. % were grown by reactive dual magnetron sputtering in an UHV system. It was shown that the elastic and dielectric properties of the as-deposited films are affected by the amount of the incorporated C and the film density.

  • 7.
    Music, Denis
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Schneider, Jochen
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Kugler, Veronika Mozhdeh
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Nakao, S.
    National Industrial Research Institute of Nagoya, Nagoya 462-8510, Japan.
    Jin, P.
    National Industrial Research Institute of Nagoya, Nagoya 462-8510, Japan.
    Östblom, Mattias
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Hultman, Lars
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Helmersson, Ulf
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics .
    Synthesis and mechanical properties of boron suboxide thin films2002In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, ISSN 0734-2101, E-ISSN 1520-8559, Vol. 20, no 2, p. 335-337Article in journal (Refereed)
    Abstract [en]

    The synthesis and mechanical properties of boron suboxide thin films deposited on silicon and graphite substrates was discussed. The deposition was performed using reactive magnetron sputtering technique, and amorphous films were obtained. The affect of varying O2 partial pressure on film composition and microstructure was studied using spectroscopic techniques. It was found that variation of partial pressure from 0.02 to 0.21 resulted in a decrease in elastic modulus from 272 to 109 GPa.

  • 8. Wang, Z.
    et al.
    Kugler, Veronika Mozhdeh
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Helmersson, Ulf
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics .
    Evangelou, E.K.
    Applied Physics Laboratory, Department of Physics, University of Ioannina, 451 10 Ioannina, Greece.
    Konofaos, N.
    Applied Physics Laboratory, Department of Physics, University of Ioannina, 451 10 Ioannina, Greece.
    Nakao, S.
    National Institute of AIST Chubu, Nagoya 462-8510, Japan.
    Jin, P.
    National Institute of AIST Chubu, Nagoya 462-8510, Japan.
    Characteristics of SrTiO3 thin films deposited on Si by rf magnetron sputtering at various substrate temperatures2002In: Philosophical Magazine B, ISSN 1364-2812, E-ISSN 1463-6417, Vol. 82, no 8, p. 891-903Article in journal (Refereed)
    Abstract [en]

    SrTiO3 (STO) thin films were deposited on p-type Si(100) substrates by rf magnetron sputtering at various substrate temperatures, and their structural and electrical properties were investigated without post-deposition annealing. The thickness of the films was in the range from 300 to 500 nm while the deposition temperature was varied between room temperature and 550°C. Compositional and structural characterizations included X-ray diffraction, Rutherford back-scattering spectroscopy and variable-angle spectroscopic ellipsometry. Metal-insulator-semiconductor diodes with the configuration of Al/STO/p-Si/Al were fabricated and characterized by capacitance-voltage, current voltage and admittance spectroscopy measurements. Depending on the substrate temperatures, the dielectric constant of the films varied between 60 and 120 and the loss factor between 0.019 and 0.051 at 100 kHz. All films showed high charge storage capacity, varying between 1.9 and 3 µm cm-2. However, the films deposited at 200°C showed the lowest density of bulk trapped charges (150nC cm-2) and interface states ((1.2-6.1) × 1011 cm-2 eV-1), and are therefore considered to be the most suitable for device applications.

  • 9. Wang, Z.
    et al.
    Kugler, Veronika Mozhdeh
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Helmersson, Ulf
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics .
    Konofaos, N.
    Applied Physics Laboratory, Department of Physics, University of Ioannina, 451 10 Ioannina, Greece.
    Evangelou, E.K.
    Applied Physics Laboratory, Department of Physics, University of Ioannina, 451 10 Ioannina, Greece.
    Nakao, S.
    Natl. Inst. Adv. Indust. Sci. T., Nagoya 462-8510, Japan.
    Jin, P.
    Natl. Inst. Adv. Indust. Sci. T., Nagoya 462-8510, Japan.
    Electrical properties of SrTiO3 thin films on Si deposited by magnetron sputtering at low temperature2001In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 79, no 10, p. 1513-1515Article in journal (Refereed)
    Abstract [en]

    Deposition of SrTiO3 (STO) thin films by radio-frequency magnetron sputtering in an ultrahigh vacuum system at a low substrate temperature (~200°C) was performed in order to produce high-quality STO/p-Si (100) interfaces and STO insulator layers with dielectric constants of high magnitude. The STO films were identified as polycrystalline by x-ray diffraction, and were approximated with a layered structure according to the best fitting results of raw data from both Rutherford backscattering spectroscopy and variable angle spectroscopic ellipsometry. Room-temperature current-voltage and capacitance-voltage (C-V) measurements on Al/STO/p-Si diodes clearly revealed metal-insulator-semiconductor behavior, and the STO/p-Si interface state densities were of the order of 1011 eV-1 cm-2. The dielectric constant of the STO film was 65, and the dielectric loss factor varied between 0.05 and 0.55 for a frequency range of 1 kHz-10 MHz. For a 387 nm thick STO film, the dielectric breakdown field was 0.31 MV cm-1, and the charge storage capacity was 2.1 µC cm-2. These results indicate that STO films are suitable for applications as insulator layers in dynamic random access memories or as cladding layers in electroluminescent devices. © 2001 American Institute of Physics.

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