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  • 1.
    Anderson, Henrik
    et al.
    Uppsala University.
    Wingqvist, Gunilla
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Weissbach, Thomas
    Attana AB.
    Wallinder, Daniel
    Attana AB.
    Katardjiev, Ilia
    Uppsala University.
    Ingemarsson, Bjorn
    Attana AB.
    Systematic investigation of biomolecular interactions using combined frequency and motional resistance measurements2011In: SENSORS AND ACTUATORS B-CHEMICAL, ISSN 0925-4005, Vol. 153, no 1, p. 135-144Article in journal (Refereed)
    Abstract [en]

    The resonance frequency of acoustic biosensors is today used as a label-free technique for detecting mass changes on sensor surfaces. In combination with an appropriate continuous flow system it has earlier been used for affinity and kinetic rate determination. Here, we assess the potential of a modified acoustic biosensor, monitoring also the real-time dissipation through the resistance of the sensor, to obtain additional kinetic information related to the structure and conformation of the molecules on the surface. Actual interaction studies. including an attempt to determine avidity, are presented along with thorough verification of the experimental setup utilizing true viscous load exposure together with protein and DNA immobilizations. True viscous loads show a linear relationship between resistance and frequency as expected. However, in the interaction studies between antibodies and proteins, as well as in the immobilization of DNA and proteins, higher surface concentrations of interacting molecules led to a decrease (i.e. deviation from the linear trend) in the differential resistance to frequency ratio. This is interpreted as increased surface rigidity at higher surface concentrations of immobilized molecules. Consequently, studies that aim at obtaining biological binding information, such as avidity, from real-time resistance and dissipation data should be conducted at low surface concentrations. In addition, the differential resistance to frequency relationship was found to be highly dependent on the rigidity of the preceding layer(s) of immobilized molecules. This dependence can be utilized to obtain a higher signal-to-noise ratio for resistance measurement by using low surface densities of immobilized interaction partners.

  • 2.
    Höglund, Carina
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Alling, Björn
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics . Linköping University, The Institute of Technology.
    Bareño, Javier
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Czigány, Zsolt
    Research Institute for Technical Physics and Materials Science, Hungarian Academy of Sciences, P.O. Box 49, H-1525 Budapest, Hungary.
    Persson, Per O. Å.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Wingqvist, Gunilla
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Zukauskaite, Agne
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Wurtzite-structure Sc1-xAlxN solid solution films grown by reactive magnetron sputter epitaxy: structural characterization and first-principles calculations2010In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 107, no 12, p. 123515-Article in journal (Refereed)
    Abstract [en]

    AlN(0001) was alloyed with ScN with molar fractions up to ~22%, while retaining a singlecrystal wurtzite (w-) structure and with lattice parameters matching calculated values. Material synthesis was realized by magnetron sputter epitaxy of thin films starting from optimal conditions for the formation of w-AlN onto lattice-matched w-AlN seed layers on Al2O3(0001) and MgO(111) substrates. Films with ScN contents between 23% and ~50% exhibit phase separation into nanocrystalline ScN and AlN, while ScN-rich growth conditions yield a transformation to rocksalt-structure Sc1-xAlxN(111) films. The experimental results are analyzed with ion beam analysis, X-ray diffraction, and transmission electron microscopy, together with ab-initio calculations of mixing enthalpies and lattice parameters of solid solutions in wurtzite, rocksalt, and layered hexagonal phases.

  • 3.
    Kerdsongpanya, Sit
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Van Nong, Ngo
    Technical University of Denmark.
    Pryds, Nini
    Technical University of Denmark.
    Zukauskaite, Agne
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Jensen, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Lu, Jun
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Wingqvist, Gunilla
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Eklund, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Anomalously high thermoelectric power factor in epitaxial ScN thin films2011In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 99, no 23, p. 232113-Article in journal (Refereed)
    Abstract [en]

    Thermoelectric properties of ScN thin films grown by reactive magnetron sputtering on Al2O3(0001) wafers are reported. X-ray diffraction and elastic recoil detection analyses show that the composition of the films is close to stoichiometry with trace amounts (similar to 1 at. % in total) of C, O, and F. We found that the ScN thin-film exhibits a rather low electrical resistivity of similar to 2.94 mu Omega m, while its Seebeck coefficient is approximately similar to-86 mu V/K at 800 K, yielding a power factor of similar to 2.5 x 10(-3) W/mK(2). This value is anomalously high for common transition-metal nitrides.

  • 4.
    Nakagomia, Shinji
    et al.
    Ishinomaki Senshu University.
    Wingqvist, Gunilla
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Åbom, Elisabeth
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Helmersson, Ulf
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics.
    Lloyd-Spets, Anita
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics.
    Hydrogen sensing by NKN thin film with high dielectric constant and ferroelectric property2005In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 108, p. 490-495Article in journal (Refereed)
    Abstract [en]

    Hydrogen sensing properties of sodium potassium niobate NaxKyNbOz (NKN) thin films were studied. The NKN thin films were prepared by reactive rf magnetron sputtering. NKN is a ferroelectric material with high dielectric constant. The polarization increases in hydrogen ambient and decreases in oxygen ambient. The conductivity of the NKN film in hydrogen ambient is higher than in oxygen ambient, and these changes are reversible. The threshold voltage of the current-voltage (I-V) characteristics depends on the hydrogen concentration, and a large response of 3.3V was obtained.

  • 5.
    Tasnadi, Ferenc
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Alling, Björn
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Höglund, Carina
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Wingqvist, Gunilla
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Abrikosov, Igor
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Origin of the Anomalous Piezoelectric Response in Wurtzite ScxAl1-xN Alloys2010In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 104, no 13, p. 137601-Article in journal (Refereed)
    Abstract [en]

    The origin of the anomalous, 400% increase of the piezoelectric coefficient in ScxAl1-xN alloys is revealed. Quantum mechanical calculations show that the effect is intrinsic. It comes from a strong change in the response of the internal atomic coordinates to strain and pronounced softening of C-33 elastic constant. The underlying mechanism is the flattening of the energy landscape due to a competition between the parent wurtzite and the so far experimentally unknown hexagonal phases of the alloy. Our observation provides a route for the design of materials with high piezoelectric response.

  • 6.
    Wingqvist, Gunilla
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    AlN-based sputter-deposited shear mode thin film bulk acoustic resonator (FBAR) for biosensor applications - A review2010In: SURFACE and COATINGS TECHNOLOGY, ISSN 0257-8972, Vol. 205, no 5, p. 1279-1286Article in journal (Refereed)
    Abstract [en]

    A new type of biosensor device is here presented which is fabricated using the same processes used for the fabrication of integrated electrical circuits to enable tighter integration and further sensor/biosensor miniaturization. The device is a so-called thin film bulk acoustic resonator (FBAR) operating in shear mode. Here specifically AlN-based shear mode FBAR is addressed but also an overview of the shear mode FBAR development in general is presented. Developments are reported of a low temperature reactive sputtering process for growing wurtzite-AlN thin films with a close to homogenous c-axis inclination over a 4 substrate wafer. This process enabled fabrication of shear mode FBAR sensors. The sensor operation is described along with how the design parameters influence its performance. Specifically, sensitivity amplification utilizing low acoustic impedance layers in the FBAR structure is demonstrated and explained. The resolution of the AlN shear mode FBAR sensor is demonstrated to already be comparable with the conventional quartz crystal microbalance (QCM) sensor, suggesting that shear mode FBAR may be a competitive and low cost alternative to QCM.

  • 7.
    Wingqvist, Gunilla
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Thin-film electro-acoustic sensors based on AlN and its alloys: possibilities and limitations2012In: Microsystem Technologies: Micro- and Nanosystems Information Storage and Processing Systems, ISSN 0946-7076, E-ISSN 1432-1858, Vol. 18, no 7-8, p. 1213-1223Article in journal (Refereed)
    Abstract [en]

    Sputter deposited aluminum nitride (AlN) thin films have played a central role for the successful development of the thin film electro-acoustic technology. The development has been primarily driven by one device-the thin film bulk acoustic resonator, with its primary use for high frequency filter applications for the telecom industry. Recently, increased piezoelectric properties in AlN through the alloying with scandium nitride have been identified both experimentally and theoretically. This opens up new possibilities for the thin film electro-acoustic technology. Here expectations and discussions are presented on acoustic FBAR sensor performance when based on AlN as well as on such AlN alloys to identify possible benefits and limitations. Inhere, the distinction is made between direct and in-direct (acoustic) use of the piezoelectric effect for sensor applications. These two approaches are described and compared in view of their advantages and possibilities. Especially, the indirect (or acoustic) use is identified as interesting for its versatility and good exploitation of the thin film technology to obtain highly sensitive sensor transducers. It is pointed out that the indirect approach can well be obtained internally in the piezoelectric material structure. Original calculations are presented to support the discussion.

  • 8.
    Wingqvist, Gunilla
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Tasnadi, Ferenc
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics . Linköping University, The Institute of Technology.
    Zukauskaite, Agne
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Increased electromechanical coupling in w-ScxAl1-xN2010In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 97, no 11, p. 112902-Article in journal (Refereed)
    Abstract [en]

    AlN is challenged as the material choice in important thin film electroacoustic devices for modern wireless communication applications. We present the promise of superior electromechanical coupling (kt2), in w−ScxAl1−xN by studying its dielectric properties. w−ScxAl1−xN (0≤x≤0.3) thin films grown by dual reactive magnetron sputtering exhibited low dielectric losses along with minor increased dielectric constant (ε). Ellipsometry measurements of the high frequency ε showed good agreement with density function perturbation calculations. Our data show that kt2 will improve from 7% to 10% by alloying AlN with up to 20 mol % ScN.

     

  • 9.
    Žukauskaitė, Agnė
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Wingqvist, Gunilla
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Pališaitis, Justinas
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Jensen, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Persson, Per O. Å.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Matloub, Ramin
    Ceramics Laboratory, Ecole Polytechnique Fédérale de Lausanne EPFL, Lausanne, SwitzerlandNational Laboratory, Oak Ridge, TN 37831, United States.
    Muralt, Paul
    Ceramics Laboratory, Ecole Polytechnique Fédérale de Lausanne EPFL, Lausanne, Switzerland.
    Kim, Yunseok
    Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831, United States.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Microstructure and Dielectric Properties of Piezoelectric Magnetron Sputtered w-ScxAl1-xN thin films2012In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 111, no 9, p. 093527-Article in journal (Refereed)
    Abstract [en]

    Piezoelectric wurtzite ScxAl1-xN (x=0, 0.1, 0.2, 0.3) thin films were epitaxially grown by reactive magnetron co-sputtering from elemental Sc and Al targets. Al2O3(0001) wafers with TiN(111) seed and electrode layers were used as substrates. X-ray diffraction shows that an increase in the Sc content results in the degradation of the crystalline quality. Samples grown at 400 °C possess true dielectric behavior with quite low dielectric losses and the leakage current is negligible. For ScAlN samples grown at 800 °C, the crystal structure is poor and leakage current is high. Transmission electron microscopy with energy dispersive x-ray spectroscopy mapping shows a mass separation into ScN-rich and AlN-rich domains for x≥0.2 when substrate temperature is increased from 400 to 800 °C. The piezoelectric response of epitaxial ScxAl1-xN films measured by piezoresponse force microscopy and double beam interferometry shows up to 180% increase by the addition of Sc up to x=0.2 independent of substrate temperature, in good agreement with previous theoretical predictions based on density-functional theory.

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