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  • 151.
    Johansson, Malin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Kristiansen, Paw T.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Duda, Laurent
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Niklasson, Gunnar
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Österlund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Band gap states in nanocrystalline WO3 thin films studied by softx-ray spectroscopy and opticalspectrophotometry2016In: Journal of Physics: Condensed Matter, ISSN 1361-648X, Vol. 28, article id 475802Article in journal (Refereed)
    Abstract [en]

    Nanocrystalline tungsten trioxide (WO3) thin films prepared by DC magnetron sputteringhave been studied using soft x-ray spectroscopy and optical spectrophotometry. Resonantinelastic x-ray scattering (RIXS) measurements reveal band gap states in sub-stoichiometric γ-WO3−x with x = 0.001–0.005. The energy positions of these states are in good agreementwith recently reported density functional calculations. The results were compared with opticalabsorption measurements in the near infrared spectral region. An optical absorption peak at 0.74 eV is assigned to intervalence transfer of polarons between W sites. A less prominentpeak at energies between 0.96 and 1.16 eV is assigned to electron excitation of oxygenvacancies. The latter results are supported by RIXS measurements, where an energy loss inthis energy range was observed, and this suggests that electron transfer processes involvingtransitions from oxygen vacancy states can be observed in RIXS. Our results have implicationsfor the interpretation of optical properties of WO3, and the optical transitions close to the bandgap, which are important in photocatalytic and photoelectrochemical applications.

  • 152. Johansson, Malin
    et al.
    Niklasson, Gunnar
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Österlund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Determination of structures and properties of WO3 thin films deposited by DC magnetron sputtering2009Conference paper (Refereed)
  • 153.
    Johnson, William B.
    et al.
    W. L. Gore & Associates.
    Worrell, Wayne L.
    University of Pennsylvania.
    Niklasson, Gunnar A
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Malmgren, Sara
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Strömme, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Sundaram, S K
    Alfred University.
    Solid-State Devices: Impedance Response of Electrochromic Materials and Devices2018In: IMPEDANCE SPECTROSCOPY: Theory, Experiment, and Applications / [ed] Evgenij Barsoukov and J. Ross Macdonald, Hoboken,: John Wiley & Sons, 2018, 3rd, p. 247-291Chapter in book (Refereed)
  • 154.
    Jonsson, A K
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials. Fasta tillståndets fysik.
    Larsson, A-L
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials. Fasta tillståndets fysik.
    Niklasson, G A
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials. Fasta tillståndets fysik.
    Strömme, M
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials. Nanoteknologi och funktionella material.
    H+ Conduction Parameters in Solid-State Electrochromic Devices Obtained by the Isothermal2005In: J. Electrochem. Soc., Vol. 152, p. A377-A379Article in journal (Refereed)
  • 155.
    Jonsson, AnnaKarin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science.
    Frenning, Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science.
    Nilsson, M
    Strømme Mattsson, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science.
    Niklasson, Gunnar A
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science.
    Dielectric study of thin films of Ta2O5 and ZrO22001In: IEEE transactions on dielectrics and electrical insulation, ISSN 1070-9878, E-ISSN 1558-4135, Vol. 8, no 4, p. 648-651Article in journal (Refereed)
    Abstract [en]

    Electronic conduction in sputtered Ta2O5 and ZrO2 thin films have been studied using impedance spectroscopy, isothermal transient ionic current, and current-voltage measurements. The dielectric properties of Ta2O5 were shown to be sensitively dependent on deposition parameters with two different frequency responses: a flat loss behavior with very low DC conductivity, or a relaxation peak together with a somewhat higher DC conductivity. ZrO2 has different dielectric properties when fresh, i.e. newly deposited, or aged. A fresh sample arbitrarily can show two different behaviors, consisting of a DC conductivity with a relaxation peak superimposed on it. The DC conductivity shows either of two different values. The aged sample has a lower permittivity and DC conductivity, and the relaxation peak is found at much lower frequencies. Fresh samples of ZrO2 also show switching behavior

  • 156.
    Jonsson, Jacob
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Materials Science.
    Karlsson, Linus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Materials Science.
    Nostell, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Materials Science.
    Niklasson, Gunnar
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Materials Science.
    Smith, Geoffrey
    Angle-dependent light scattering in materials with controlled diffuse solar optical properties2004In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 84, no 1-4, p. 427-439Article in journal (Refereed)
    Abstract [en]

    Light scattering plays a prominent role in a wide range of energy-efficient materials and solar applications. Some examples are materials for daylighting, diffusely reflecting sunscreens, foils for radiative cooling and nanocrystalline solar cells. Measurements of the angular profile of light scattering are very useful for obtaining a detailed characterization of the light scattering mechanisms. We review recent theoretical results on the forward and backward light scattering profiles. Forward scattering is of major importance for novel pigmented polymeric daylighting materials. Measurements of scattering profiles are in good agreement with Mie theory. Backscattering profiles from highly diffusely reflecting paints containing titanium oxide-based pigments have also been measured. It seems that scattering from the paint surface dominates at low pigment volume fractions. Results for paints with high pigment volume fractions are interpreted in terms of coherent backscattering effects from the pigment particles.

  • 157.
    Kaden, Heike
    et al.
    Karlsruhe Institute of Technology.
    Königer, F
    Karlsruhe Institute of Technology.
    Schuhmann, R
    Karlsruhe Institute of Technology.
    Niklasson, Gunnar A
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Emmerich, Katja
    Karlsruhe Institute of Technology.
    Detection of moisture differences of a swellable and a non-swellable clay in the low and mid frequency range2011In: 6th Conference on Innovative Moisture Measurement in Research and Practise, Karlsruhe, Oct. 2011, 2011, p. 10pp-Conference paper (Refereed)
    Abstract [en]

    The sensitivity of dielectric spectroscopy to display changes in moisture content was studied for one swellable (bentonite) and one non-swellable clay (illite) in the low (1.0E-04…1.0E+06 Hz) and mid (2.0E+08…1.1E+09 Hz) frequency range. Therefore, both air dry materials were stored until equilibration at 11% and 93% relative humidity (r.h.) and their volumetric water content (Wvol) was measured with static and dynamic heating as well as with dielectric spectroscopy. Transformation of complex permittivity to Wvol was accomplished using the calibration functions after Topp and Roth. Moisture distinction could be displayed for both materials in the lower frequency range, whereas the changes in water content could only be described for the illite within the mid frequency range. Estimation of volumetric water content by transformation of real relative permittivity with Topp-function, resulted in underestimation of Wvol, especially for samples stored at high relative humidity (93% r.h.). Determination of Wvol with the calibration function after Roth was successful for illite at 11% r.h., but failed at higher relative humidity and for the bentonite in both hydration states. Additionally, complex dielectric data were clearly influenced by other processes beside bound water polarization.

  • 158.
    Kaden, Heike
    et al.
    Karlsruhe Institute of Technology.
    Königer, Franz
    Karlsruhe Institute of Technology.
    Strömme, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Niklasson, Gunnar A.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Emmerich, Katja
    Karlsruhe Institute of Technology.
    Low-frequency dielectric properties of three bentonites at different adsorbed water states2013In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 411, p. 16-26Article in journal (Refereed)
    Abstract [en]

    Three bentonites of varying smectite content were investigated by dielectric spectroscopy in the frequency range 10(-4) to 10(6)Hz after storage at well-defined humidities. The identification of relaxation processes from complex permittivity measurements was difficult, since conductivity effects were superimposed on the underlying relaxations. Relaxation peaks revealed by the dissipation factor indicated the occurrence of interfacial processes between 10(2) and 10(6) Hz. The intensity of the polarization of the electrochemical double-layer at the clay-water interface was promoted by increasing water content and was shifted to higher frequencies the higher the water content in the bentonites. Below ∼1Hz, electrode polarization (EP) was shown to be a participating process with capacitance values ranging from 0.6(*)10(-3) to 7.3(*)10(-3)F due to the accumulated charges. An equivalent circuit model was introduced that successfully described the low-frequency dielectric behavior of bentonites at low moisture levels. An included series R-CPE connection was used to describe the double-layer relaxation. At water contents up to 17%, the bulk resistivity was mainly influenced by smectite content and cation exchange capacity, whereas at water contents of ⩾19%, interlayer occupation and hydration state became more important.

  • 159.
    Kaden, Heike
    et al.
    Karlsruhe Institute of Technology.
    Niklasson, Gunnar A.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Königer, F
    Karlsruhe Institute of Technology.
    Schuhmann, R
    Karlsruhe Institute of Technology.
    Emmerich, K
    Karlsruhe Institute of Technology.
    Dielectric spectroscopy of swellable clays at low moisture levels2012In: BDS 2012. Broadband Dielectric Spectroscopy and its Applications, Leipzig, September 3-7, 2012., 2012, p. 142-Conference paper (Refereed)
  • 160.
    Karlsson, Stefan
    et al.
    RISE Research Institutes of Sweden.
    Österlund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, Claes Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Järn, M
    RISE.
    Eriksson, J
    RISE.
    Welinder, J
    RISE.
    Försth, M
    RISE.
    Ludvigsson, Mikael
    RISE.
    "Transparent intelligence" for sustainable development2018In: Abstracts: 15th Internatinal Conference on the Physics of Non-Crystalline Solids och 14th European Society of Glass Conference (PNCS-ESG 2018), Saint Malo, Frankrike, 2018, p. 208-Conference paper (Refereed)
    Abstract [en]

    Transparent materials are essential in everyone’s life. They enable daylight to reach the interior of buildings, thereby contributing to both our physical and mental well-being; they are the primary component for communication via optical fibers and a key component in electronic devices such as protective cover and/or dielectric material; and they enable clean energy production through solar panels or algae reactors by acting as protective and light transmitting barriers. Adding functions to transparent materials in an intelligent way creates further opportunities to use and enhance the beneficial impacts of transparency. The concept Transparent Intelligence covers transparent materials and products with integral intelligent functions – passive, active or interactive. By using Transparent Intelligence it is possible to embrace many of the societal challenges that we are facing today. The concept can be divided into five broad industrial sectors: Built Environment, Information and Communication Technologies (ICT), Solar Energy, Mobility, and Materials. A perspective on how Transparent Intelligence can improve the sustainable development of our world will be presented, using examples of electrochromic windows for energy-efficient buildings, photocatalytic coatings for improved indoor air quality, transparent conductive coatings for antennas, bandpass filters for mobile phone indoor coverage, UV down-converting components for efficient solar energy, hygienic surfaces for infection mitigation on electronic devices, printed electronics for sustainable glass packaging, and IR-reflecting coatings for fire safety.

  • 161.
    Kish, L. B.
    et al.
    Texas A&M Univ, Dept Elect & Comp Engn, College Stn, TX USA.
    Ferry, D. K.
    Arizona State Univ, Sch Elect Comp & Energy Engn, Tempe, AZ USA.
    Niklasson, G. A.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Smulko, J. M.
    Gdansk Univ Technol, Fac Elect Telecommun Informat, Dept Metrol & Optoelect, Gdansk, Poland.
    Granqvist, Claes Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Facts and myths about zero-point thermal noise, and information entropy versus thermal entropy2017In: 2017 INTERNATIONAL CONFERENCE ON NOISE AND FLUCTUATIONS (ICNF), IEEE, 2017Conference paper (Refereed)
    Abstract [en]

    In this talk, we are briefly surveying our recent results [1-3] about two very popular yet often misunderstood concepts in physical informatics: (i) The existence of Johnson noise at near to absolute zero temperature has been debated many times yet it is generally accepted [1]. We point out the fundamental problems [2] with the particular approach the related quantum theories [4] of Fluctuation-Dissipation Theorem are using. Then we prove that the existence of zero-point noise would allow the construction of a perpetual motion machine [1]. Finally, we cite early works pointing out that the observed “zeropoint” noise in experiments [7] with phase-sensitive linear amplifiers is an amplifier-noise [5,6] due to the uncertainty principle, and it does not exist in the resistor in an objective way, independently from the measurement [1,2]. Thus a correct derivation of the Fluctuation-Dissipation Theorem must include [1] the type of experimental setup used for the measurement. (ii) The general opinion is that information entropy and thermal entropy are interchangeable. This belief triggered Brillouin's negentropy principle of information [8], and Landauer's claimed principle [9] about energy dissipation during information erasure that has been debated on many occasions [10-19]. Here we show the newest and perhaps the simplest arguments [3] proving that the two types of entropies are apples and oranges and are not interchangeable.

  • 162.
    Kish, Laszlo B
    et al.
    Department of Electrical and Computer Engineering, Texas A&M University, College Station, Texas.
    Granqvist, Claes-Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Khatri, Sunil P
    Department of Electrical and Computer Engineering, Texas A&M University, College Station, Texas.
    Niklasson, Gunnar A.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Peper, Ferdinand
    CiNet, NICT, Osaka University, Osaka, Japan.
    Information, Noise, and Energy Dissipation:: Laws, Limits, and Applications2017In: Molecular Architectonics: Advances in Atom and Single Molecule Machines / [ed] T. Ogawa, Springer, 2017, p. 27-44Chapter in book (Refereed)
    Abstract [en]

    This chapter addresses various subjects, including some open questions related to energy dissipation, information, and noise, that are relevant for nano- and molecular electronics. The object is to give a brief and coherent presentation of the results of a number of recent studies of ours

  • 163.
    Kish, Laszlo B.
    et al.
    Department of Electrical Engineering, Texas A&M University, Texas USA.
    Niklasson, Gunnar A.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, Claes Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Zero Thermal Noise in Resistors at Zero Temperature2016In: Fluctuation and Noise Letters, ISSN 0219-4775, E-ISSN 1793-6780, Vol. 15, no 3, article id 1640001Article in journal (Refereed)
    Abstract [en]

    The bandwidth of transistors in logic devices approaches the quantum limit, where Johnsonnoise and associated error rates are supposed to be strongly enhanced. However, the related theory — asserting a temperature-independent quantum zero-point (ZP) contribution to Johnson noise, which dominates the quantum regime — is controversial and resolution of the controversy is essential to determine the real error rate and fundamental energy dissipation limits of logic gates in the quantum limit. The Callen–Welton formula (fluctuation–dissipation theorem) of voltage and current noise for a resistance is the sum of Nyquist’s classical Johnson noise equation and a quantum ZP term with a power density spectrum proportional to frequency and independent of temperature. The classical Johnson–Nyquist formula vanishes at the approach of zero temperature, but the quantum ZP term still predicts non-zero noise voltage and current. Here, we show that this noise cannot be reconciled with the Fermi–Dirac distribution, which defines the thermodynamics of electrons according to quantum-statistical physics. Consequently,Johnson noise must be nil at zero temperature, and non-zero noise found for certain experimental arrangements may be a measurement artifact, such as the one mentioned in Kleen’s uncertainty relation argument.

  • 164.
    Kish, Laszlo B.
    et al.
    Texas A&M Univ, Dept Elect & Comp Engn, TAMUS 3128, College Stn, TX 77843 USA..
    Niklasson, Gunnar A.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, Claes-Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Zero-point term and quantum effects in the Johnson noise of resistors: a critical appraisal2016In: Journal of Statistical Mechanics: Theory and Experiment, ISSN 1742-5468, E-ISSN 1742-5468, article id 054006Article in journal (Refereed)
    Abstract [en]

    There is a longstanding debate about the zero-point term in the Johnson noise voltage of a resistor. This term originates from a quantum-theoretical treatment of the fluctuation-dissipation theorem (FDT). Is the zero-point term really there, or is it only an experimental artifact, due to the uncertainty principle, for phase-sensitive amplifiers? Could it be removed by renormalization of theories? We discuss some historical measurement schemes that do not lead to the effect predicted by the FDT, and we analyse new features that emerge when the consequences of the zero-point term are measured via the mean energy and force in a capacitor shunting the resistor. If these measurements verify the existence of a zero-point term in the noise, then two types of perpetual motion machines can be constructed. Further investigation with the same approach shows that, in the quantum limit, the Johnson-Nyquist formula is also invalid under general conditions even though it is valid for a resistor-antenna system. Therefore we conclude that in a satisfactory quantum theory of the Johnson noise, the FDT must, as a minimum, include also the measurement system used to evaluate the observed quantities. Issues concerning the zero-point term may also have implications for phenomena in advanced nanotechnology.

  • 165.
    Kish, Laszlo B
    et al.
    Department of Electrical and Computer Engineering, Texas A&M University, College Station,.
    Niklasson, Gunnar A.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, Claes-Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Ferry, D K
    School of Electrical, Computer and Energy Engineering, Arizona State University, Tempe.
    Smulko, Janusz M
    Department of Metrology and Optoelectronics, Faculty of Electronics, Telecommunications, Informatics, Gdansk University of Technology.
    Facts and myths about zero-point thermal noise, and information entropy versus thermal entropy2017In: 2017 International Conference on Noise and Fluctuations, IEEE, 2017Conference paper (Refereed)
    Abstract [en]

    In this talk, we are briefly surveying our recent results [1-3] about two very popular yet often misunderstood concepts in physical informatics: (i) The existence of Johnson noise at near to absolute zero temperature has been debated many times yet it is generally accepted [1]. We point out the fundamental problems [2] with the particular approach the related quantum theories [4] of Fluctuation-Dissipation Theorem are using. Then we prove that the existence of zero-point noise would allow the construction of a perpetual motion machine [1]. Finally, we cite early works pointing out that the observed "zeropoint" noise in experiments [7] with phase-sensitive linear amplifiers is an amplifier-noise [5,6] due to the uncertainty principle, and it does not exist in the resistor in an objective way, independently from the measurement [1,2]. Thus a correct derivation of the Fluctuation-Dissipation Theorem must include[1] the type of experimental setup used for the measurement. (ii) The general opinion is that information entropy and thermal entropy are interchangeable. This belief triggered Brillouin's negentropy principle of information [8], and Landauer's claimed principle [9] about energy dissipation during information erasure that has been debated on many occasions [10-19]. Here we show the newest and perhaps the simplest arguments [3] proving that the two types of entropies are apples and oranges and are not interchangeable.

  • 166. Kish, LB
    et al.
    Niklasson, G A
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, Claes Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Ferry, DK
    Smulko, JM
    Facts and myths about zero-point thermal noise, and information entropy versus thermal entropy2017In: IEEE Digital Library, 2017Conference paper (Refereed)
  • 167.
    Laaksonen, Katri
    et al.
    Aalto University.
    Li, Shu-Yi
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Puisto, S. R.
    MatOx Oy.
    Rostedt, N. K. J.
    MatOx Oy.
    Ala-Nissila, T.
    Aalto University.
    Granqvist, Claes-Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Nieminen, R. M.
    Aalto University.
    Niklasson, Gunnar A.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Nanoparticles of TiO2 and VO2 in dielectric media: Conditions for low optical scattering, and comparison between effective medium and four-flux theories2014In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 130, no SI, p. 132-137Article in journal (Refereed)
    Abstract [en]

    Spectral transmittance and reflectance in the 300 to 2500 nm solar-optical wavelength range were calculated for nanoparticles of titanium dioxide and vanadium dioxide with radii between 5 and 100 nm embedded in transparent dielectric media. Both of the materials are of large importance in green nanotechnologies: thus TiO2 is a photocatalyst that can be applied as a porous film or a nanoparticle composite on indoor or outdoor surfaces for environmental remediation, and VO2 is a thermochromic material with applications to energy-efficient fenestration. The optical properties, including scattering, of the nanoparticle composites were computed from the Maxwell–Garnett effective-medium theory as well as from a four-flux radiative transfer model. Predictions from these theories approach one another in the limit of small particles and in the absence of optical interference. Effects of light scattering can be modeled only by the four-flux theory, though. We found that nanoparticle radii should be less than ~20 nm in order to avoid pronounced light scattering.

  • 168.
    Lansåker, P. C.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Johansson, M.
    Granqvist, C.-G.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Österlund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Temperature Dependent Coalescence in Au Films and Nanopartickles: Applications to Smart Windows and Photocatalysis2011Conference paper (Refereed)
  • 169.
    Lansåker, Pia
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Backholm, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, Claes-Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    TiO2/Au/TiO2 Multilayer Thin Films: Novel Metal-Based Transparent Conductors for Electrochromic Devises2009In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 518, no 4, p. 1225-1229Article in journal (Refereed)
    Abstract [en]

    Transparent conductors based on Au films, with thicknesses in the 2.6<d<9.8 nm range, were made by DC magnetron sputtering onto glass. The films went from an "island" structure at low thicknesses to a uniform structure at d>8 nm, as seen from electron microscopy, electrical resistance, and spectrophotometric transmittance and reflectance. Optical data for uniform films were given a consistent interpretation within the Drude model. Optimized TiO2/Au/TiO2 films, with a luminous transmittance of 80%, were found to have good electrochemical durability and may be useful for applications in electrochromic devices.

  • 170.
    Lansåker, Pia C.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Gunnarsson, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Roos, Arne
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar A.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, Claes-Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Au-Based Transparent Conductors for Window Applications: Effect of Substrate Material2010In: Advances in Science and Technology, ISSN 1662-0356, Vol. 75, p. 25-30Article in journal (Refereed)
    Abstract [en]

    Thin films of Au were made by sputter deposition onto glass substrates with and without transparent and electrically conducting layers of SnO2:In. The Au films were up to ~11 nm in thickness and covered the range for thin film growth from discrete islands, via large scale coalescence and formation of a meandering conducting network, to the formation of a more or less “holey” film. Scanning electron microscopy and atomic force microscopy showed that the SnO2:In films were considerably rougher than the glass itself. This roughness influenced the Au film formation so that large scale coalescence set in at a somewhat larger thickness for films on SnO2:In than on glass. Measurements of spectral optical transmittance and electrical resistance could be reconciled with impeded Au film formation on the SnO2:In layer, leading to pronounced “plateaus” in the near infrared optical properties for Au films on SnO2:In and an accompanying change from such two-layer films having a lower resistance than the single gold film at thicknesses below large scale coalescence to the opposite behavior for larger film thicknesses.

  • 171.
    Lansåker, Pia C
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Gunnarsson, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Roos, Arne
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, Claes-Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Au thin films deposited on SnO2:In and glass: Substrate effects on the optical and electrical properties2011In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 519, no 6, p. 1930-1933Article in journal (Refereed)
    Abstract [en]

    We report on a detailed study on the optical and electrical properties of Au films made by sputter deposition onto glass substrates with and without transparent and electrically conducting layers of SnO2:In. The Au films had thicknesses up to 10.7 nm and hence spanned the range for thin film growth from discrete islands, via large scale coalescence and formation of a meandering conducting network, to the formation of a more or less "holey" film. Scanning electron microscopy and atomic force microscopy demonstrated that the SnO2:In films were considerably rougher than the glass itself, and this roughness influenced the Au film formation so that large scale coalescence set in at a somewhat larger thickness for films on SnO2:In than on glass. Measurements of spectral optical transmittance and reflectance and of electrical resistance gave a fully consistent picture that could be reconciled with impeded Au film formation on the SnO2:In layer; this led to pronounced "plateaus" in the near infrared optical spectra for Au films on SnO2:In and a concomitant change from such two-layer films having a lower resistance than the single gold film at thicknesses below large scale coalescence to the opposite behavior for larger film thicknesses. Our work highlights the importance of the substrate roughness for transparent conductors comprising coinage metal films backed by wide band gap transparent conducting oxides.

  • 172.
    Lansåker, Pia C
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Hallén, Anders
    Royal Institute of Technology, Stockholm.
    Niklasson, Gunnar A
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, Claes-Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Characterization of gold nanoparticle films: Rutherford backscatteringspectroscopy, scanning electron microscopy with image analysis, and atomic forcemicroscopy2014In: AIP Advances, ISSN 2158-3226, E-ISSN 2158-3226, Vol. 4, no 10, p. 107101-Article in journal (Refereed)
    Abstract [en]

    Gold nanoparticle films are of interest in several branches of science and technology,and accurate sample characterization is needed but technically demanding. We preparedsuch films by DC magnetron sputtering and recorded their mass thicknessby Rutherford backscattering spectroscopy. The geometric thickness dg—from thesubstrate to the tops of the nanoparticles—was obtained by scanning electron microscopy(SEM) combined with image analysis as well as by atomic force microscopy(AFM). The various techniques yielded an internally consistent characterization ofthe films. In particular, very similar results for dg were obtained by SEM with imageanalysis and by AFM.

  • 173.
    Lansåker, Pia C
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar A
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, Claes-Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Thin gold films on SnO2:In: Temperature-dependent effects on the optical properties2012In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 520, no 9, p. 3688-3691Article in journal (Refereed)
    Abstract [en]

    Gold films with thicknesses of 5 +/- 0.5 nm were sputter deposited onto SnO2:In-coated glass kept at different temperatures up to 140 degrees C, and similar films, deposited onto substrates at 25 degrees C, were annealing post treated at the same temperatures. Nanostructures and optical properties were recorded by scanning electron microscopy and spectrophotometry in the 0.3 to 2.5 mu m wavelength range, respectively. Annealing had a minor influence on the optical transmittance despite significant changes in the scale of the nanostructure, whereas deposition onto substrates heated to 140 degrees C yielded granular films with strong plasmon absorption of luminous radiation. These results are of considerable interest for optical devices with gold films prepared at elevated temperature or operating at such temperature.

  • 174.
    Lansåker, Pia C.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Petersson, P.
    Uppsala University, Disciplinary Domain of Science and Technology, För teknisk-naturvetenskapliga fakulteten gemensamma enheter, Tandem Laboratory.
    Niklasson, Gunnar A.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, Claes-Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Thin sputter deposited gold films on In2O3:Sn, SnO2:In, TiO2 and glass: Optical, electrical and structural effects2013In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 117, no SI, p. 462-470Article in journal (Refereed)
    Abstract [en]

    Thin gold films are promising transparent conductors with many actual and potential uses in "green" technologies, transparent electronics, etc. These applications require different substrate materials, and hence it is important to understand the role of the substrate on Au thin film growth. Such effects have been studied in this work wherein Au films ranging from island structures, via large scale coalescence into meandering metal networks, to thin homogenous layers were deposited by DC magnetron sputtering onto glass substrates and In2O3:Sn (ITO), SnO2:In and TiO2 base layers backed by glass. Optical, electrical and structural properties were recorded for films deposited onto unheated substrates. We found distinct and characteristic differences in Au growth on the various backings. Thus ITO and SnO2:In base layers yielded gold films with island features remaining to larger thicknesses than for deposition directly onto glass, and the sheet resistance was lower for gold deposition onto SnO2:In and ITO only when the gold films were less than similar to 5 nm in thickness. Our results highlight the complexity of substrates' influence on thin film formation. 

  • 175.
    Lansåker, Pia
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Cindemir, Umut
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Österlund, Lars
    Niklasson, Gunnar A.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, Claes-Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Indium Tin Oxide Thin Films for Formaldehyde and Acetaldehyde Sensing2014In: Micronano System Workshop, Uppsala, Sweden, 15-16 May, 2014Conference paper (Refereed)
  • 176.
    Lansåker, Pia
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Gunnarsson, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Roos, Arne
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, C.-G.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Au-based transparent conductors for windows applications: Effect of substrate material2010In: International Journal of Advances in Science and Technology, ISSN 2229-5216, Vol. 75, p. 25-30Article in journal (Refereed)
  • 177.
    Lansåker, Pia
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Ribbing, Carl-Gustaf
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar A.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, Claes-Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Temperature effect on gold nanoparticle growth and plasmonic properties.2013In: Optics and Photonics in Sweden, Uppsala Oct. 22-23, 2013: Poster abstracts, PhotonicSweden , 2013, p. 1 p-Conference paper (Other academic)
    Abstract [en]

    The plasmonic properties of gold nanoparticles (NPs) have very promising prospects to enhance theefficiency in several branches of science and technology, such as in environmental, energy, biomedicaland information technology. The plasmonic properties are strongly related to the shape, size anddistribution of the NPs and to their surrounding media. Therefore, suitable techniques for optimizedNP manufacturing, as well as improved understanding of the optical characteristics of the NPs, arenecessary for progress.In this work, gold was deposited on heated substrates using DC magnetron sputtering, which is amethod with great reproducibility and suitability for large area coatings. The method is also simple touse and gives NPs at considerably lower temperatures than other heat treating manufacturingtechniques. The depositions were performed at three different substrate temperatures, and a series ofgold NP samples were manufactured at each temperature. The localized surface plasmon resonance ofthe NPs was investigated by optical measurements, and the results were related to the shape, size anddistribution of the NPs, as observed from scanning electron microscopy and image analysis. Basic physics regarding plasmonics and metal NP growth processes are also presented.The optical results show effects of particle-particle interaction, aspect ratio and size of the NPs,which are in full agreement with results on NP structure and distribution.

  • 178.
    Lansåker, Pia
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Tuncer, Enis
    3M Austin Center, EEBG/CRML, Austin, Texas, USA.
    Valyukh, Irina
    Dept. Physics, Chemistry and Biology, Linköping University.
    Arwin, Hans
    Dept. Physics, Chemistry and Biology, Linköping University.
    Granqvist, Claes-Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar A.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Spectral Density Analysis of Thin Gold Films: Thickness and Structure Dependence of the Optical Properties2013In: PIERS 2013 Stockholm: Progress in Electromagnetics Research Symposium Proceedings,, Cambridge, MA: The Electromagnetics Academy , 2013, p. 443-447Conference paper (Refereed)
    Abstract [en]

    Abstract| In this paper we study the feasibility of representing the optical properties ofultrathin gold films by effective medium theories. Gold films with mass thicknesses in the range of 1.4 to 9.2 nm were deposited by DC magnetron sputtering onto non-heated glass substrates.Optical measurements in the range 0.25 to 2 μm were carried out by spectroscopic ellipsometry, and the effective complex dielectric function of each film was determined. The gold films were modelled as a mixture of gold and air, and a general effective medium description using the spectral density function (SDF) was used to describe their optical properties. Numerical inversion of the experimental dielectric function gave a broad and rather featureless SDF, with a few superimposed peaks, both for island structures and percolating films. The broad background is qualitatively similar to predictions of the Bruggeman model [14].

  • 179.
    Larsson, A.-L
    et al.
    Fasta tillståndets fysik/ ÅSTC.
    Niklasson, G A
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics. Fasta tillståndets fysik.
    Infrared absorption of Li-intercalated tungsten oxide2003In: IME-4 (International Meeting on Electrochromism)Article in journal (Refereed)
  • 180.
    Larsson, Anna-Lena
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Solis, Jose
    Instituto Peruano de Energía Nuclear.
    Niklasson, Gunnar A.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Infrared absorption in Li-intercalated tungsten oxide2007In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 91, no 13, p. 1248-1252Article in journal (Refereed)
    Abstract [en]

    Thin films of amorphous and polycrystalline tungsten oxide were produced by reactive dc magnetron sputtering and nanocrystalline films were deposited by advanced gas evaporation. The films were submitted to electrochemical intercalation of Li ions before infrared reflectance measurements were carried out. For crystalline films, the reflectance in the wavelength region 10–30 μm increases upon intercalation, indicating an increasing free-electron contribution. On the other hand, all the films display an increased absorption at wavelengths less than 10 μm when intercalated. The thermal emittance could be varied from about 0.5 to 0.7–0.75 by intercalation in films with thicknesses in excess of 1 μm. Both absorption and interference contribute to the emittance contrast.

  • 181.
    Lebrun, Delphine
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar A.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Österlund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Fabrication of photonic opal structures on different support materials by convective evaporation2014In: INERA Workshop: Transition Metal Oxides as Functional Layers in Smart windows and Water Splitting Devices / Parallel session of the 18th International School on Condensed Matter Physics, Institute of Physics Publishing (IOPP), 2014, p. 012007-Conference paper (Refereed)
    Abstract [en]

    Photonic polystyrene (PS) opals with face-centered cubic structure werefabricated by convective evaporation. The influences of substrate and its physicalproperties, as well as deposition conditions were investigated. It is shown that thesurface roughness must be less than about 30% of the bead diameter to form wellorderedopals, rendering substrates such as glass, ITO and quartz superior to thickKapton, ordinary tape, thermal release semiconductor tape, plastic and hydrophilicplastic HHNW W (Kemafoil). Periodic stripe-like structures were found to formperpendicular to the growth direction defined by the receding meniscus of the solutionfront when the PS concentration is lower than 1.0 w/v%. Finally, we present theprinciples and results of using soft sacrificial layer deposited on quartz substrates tofabricate free standing inverse opal structures.1.

  • 182.
    Lebrun, Delphine
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Österlund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar A.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Metal Oxides photonic band gap inverse opals2014In: Workshop on Magnetoplasmonics 2014, Uppsala (Sweden)., 2014Conference paper (Other academic)
    Abstract [en]

    Poster on metal oxide inverse opal fabrication and gold nanoparticles impregnations for the Workshop on Magnetoplasmonics 2014, Uppsala (Sweden).

  • 183.
    Li, Shuyi
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Bayrak Pehlivan, Ilknur
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar A.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, Claes-Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Progress in Electrochromics and Thermochromics: Two New Applications Involving ITO Nanoparticles.2012In: Society of Vacuum Coaters 55th Annual Technical Conference Proceedings, Albuquerque, USA: Soiety of Vacuum Coaters , 2012, p. 41-46Conference paper (Refereed)
  • 184.
    Li, Shuyi
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Mlyuka, Nuru R
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics. University of Dar es Salaam.
    Primetzhofer, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Hallén, Anders
    Royal Institute of Technology (KTH).
    Possnert, Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Niklasson, Gunnar A
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, Claes G
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Bandgap widening in thermochromic Mg-doped VO2 thin films: Quantitative data based on optical absorption2013In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 103, no 16, p. 161907-Article in journal (Refereed)
    Abstract [en]

    Thermochromic Mg-doped VO2 films were deposited by reactive direct current magnetronsputtering onto heated glass and carbon substrates. Elemental compositions were inferred fromRutherford backscattering. Optical bandgaps were obtained from spectral transmittance and reflectance measurements—from both the film side and the back side of the samples—and ensuing determination of absorption coefficients. The bandgap of Mg-doped films was found to increase by 3.9 ± 0.5 eV per unit of atom ratio Mg/(Mg + V) for 0 < Mg/(Mg + V) < 0.21. The presence of ∼0.45 at. % Si enhanced the bandgap even more.

  • 185.
    Li, Shuyi
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Namura, Kyoko
    Kyoto University - Katsura.
    Suzuki, Motofumi
    Kyoto University - Katsura.
    Niklasson, Gunnar A.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, Claes-Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Thermochromic VO2 nanorods made by sputter deposition: Growth conditions and optical modeling2013In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 114, no 3, p. 033516-Article in journal (Refereed)
    Abstract [en]

    Reactive dc magnetron sputtering onto glass-based substrates yielded deposits of thermochromic VO2 with well-developed nanorods and nanowires. Their formation was promoted by high substrate temperature (above similar to 500 degrees C), sufficient film thickness, proper inlet of the reactive gas, dispersed gold "seeds," and pronounced substrate roughness. Rutherford back scattering ascertained mass thicknesses, scanning electron microscopy depicted the nanostructures, and glancing incidence X-ray diffraction proved that single-phase VO2 was normally formed. Spectrophotometric measurements of total and diffuse transmittance and reflectance on VO2 thin films, at room temperature and similar to 100 degrees C, allowed us to determine complex dielectric functions below and above the "critical" temperature for thermochromic switching (similar to 68 degrees C). These data were then used in computations based on the Bruggeman effective medium theory applied to randomly oriented prolate spheroidal structural units to derive the optical properties of the deposits. Experimental and computed data on spectral absorptance were found to be in good qualitative agreement.

  • 186.
    Li, Shuyi
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar A
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, Claes-Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    A thermochromic low-emittance coating: Calculations for nanocomposites of In2O3:Sn and VO22011In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 99, no 13, p. 131907-Article in journal (Refereed)
    Abstract [en]

    Calculations based on the Bruggeman effective medium theory were applied to thin films comprising a heavily doped wide band gap semiconductor (specifically In(2)O(3):Sn (ITO)) and VO(2). Films with similar to 20 vol. % of VO(2) can combine a 10% thermochromic modulation of the solar energy throughput with a luminous transmittance of 50%-60% and low thermal emittance. The maximum thermochromic modulation is similar to 13% and occurs at similar to 35 vol. % VO(2). Coatings of ITO-VO(2) are of interest for energy efficient fenestration.

  • 187.
    Li, Shuyi
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar A.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, Claes-Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Nanothermochromics: Calculations for VO2 nanoparticles in dielectric hosts show much improved luminous transmittance and solar energy transmittance modulation2010In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 108, no 6, p. 063525-Article in journal (Refereed)
    Abstract [en]

    VO2-based films are thermochromic and show infrared reflectance above a "critical" temperature in the vicinity of room temperature. Implementations on energy efficient windows have been discussed for decades but have been severely curtailed since the luminous absorptance is undesirably large and the solar energy transmittance modulation is too small. Here we show by calculations based on effective medium theory that dilute composites with VO2 nanoparticles embedded in hosts with properties mimicking glass or polymer can yield significantly decreased luminous absorption jointly with much enhanced transmittance modulation of solar energy. These results demonstrate that VO2-based nanothermochromics opens new avenues toward energy efficient fenestration.

  • 188.
    Li, Shuyi
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar A
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, Claes-Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Nanothermochromics with VO2-based core-shell structures: Calculated luminous and solar optical properties2011In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 109, no 11, p. 113515-Article in journal (Refereed)
    Abstract [en]

    Composites including VO2-based thermochromic nanoparticles are able to combine high luminous transmittance T-lum with a significant modulation of the solar energy transmittance Delta T-sol at a "critical" temperature in the vicinity of room temperature. Thus nanothermochromics is of much interest for energy efficient fenestration and offers advantages over thermochromic VO2-based thin films. This paper presents calculations based on effective medium theory applied to dilute suspensions of core-shell nanoparticles and demonstrates that, in particular, moderately thin-walled hollow spherical VO2 nanoshells can give significantly higher values of Delta T-sol than solid nanoparticles at the expense of a somewhat lowered T-lum. This paper is a sequel to a recent publication [S.-Y. Li, G. A. Niklasson, and C. G. Granqvist, J. Appl. Phys. 108, 063525 (2010)].

  • 189.
    Li, Shu-Yi
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar A.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, Claes-Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Performance Limits of Thermochromic Undoped and Mg-Doped VO2 Films and Nanoparticles for Energy Efficient Window Applications2014In: European Materials Research Society (E-MRS) Spring Meeting, Lille, France, 26-30 May: Symposium L: Chromogenic Materials and Devices, 2014Conference paper (Refereed)
  • 190.
    Li, Shuyi
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar A
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, Claes-Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Plasmon-induced near-infrared electrochromism based on transparent conducting nanoparticles: Approximate performance limits2012In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 101, no 7, p. 071903-Article in journal (Refereed)
    Abstract [en]

    Electrochromism can be induced in electrochemically post-treated nanoparticles of wide band gap transparent conductors. We model this recently observed phenomenon by effective medium theory applied to nanoparticles of In2O3:Sn, which are represented as a free-electron plasma with tin ions screened according to the random phase approximation corrected for electron exchange. This semi-quantitative theory is used to derive approximate performance limits showing that high luminous transmittance (e.g., 60%) can be combined with efficient absorption of solar energy and concomitant low solar transmittance (similar to 34%), thereby documenting that plasmonic electrochromism is of interest for energy efficient fenestration.

  • 191.
    Li, Shuyi
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar A.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, Claes-Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Thermochromic fenestration with VO2-based materials: Three challenges and how they can be met2012In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 520, no 10, p. 3823-3828Article in journal (Refereed)
    Abstract [en]

    Thermochromic VO2-based films have higher infrared transmittance below a "critical" temperature tau(c) than above this temperature and can be used for regulating the solar energy transmittance T-sol in energy efficient windows. Pure VO2 is not practical, though, since (i) the modulation of T-sol is too small at tau(c), (ii) the luminous transmittance is too low, and (iii) tau(c) is too high. This paper discusses how these three challenges can be met. Specifically, using VO2-based nanoparticle composites rather than films makes it possible to significantly alleviate (i) and (ii), Mg doping of VO2 can give further improvements of (ii), and W doping (and to some extent also Mg doping) is important for (iii) and can bring tau(c) to a comfort temperature. The paper hence delineates a path towards practically useful thermochromic fenestration. 

  • 192.
    Li, Shu-Yi
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar A
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, Claes-Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Thermochromic undoped and Mg-doped VO2 thin films and nanoparticles: Optical properties and performance limits for energy efficient windows2014In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 115, no 5, p. 053513/1-/10Article in journal (Refereed)
    Abstract [en]

    Undoped and Mg-doped thermochromic VO2 films with atom ratios z equivalent to Mg/(Mg + V) of 0 <= z < 0.21 were deposited by reactive DC magnetron sputtering onto heated glass and carbon substrates. Elemental compositions were found by Rutherford backscattering spectrometry. Optical constants were determined from transmittance and reflectance measurements and were used for modeling the optical properties of thin films and dilute nanoparticle composite layers below and above the critical temperature for thermochromic switching between a low-temperature infrared transparent state and a high-temperature infrared reflecting or absorbing state. Mg-doped films showed superior luminous transmittance T-lum and solar transmittance modulation Delta T-sol compared to undoped VO2 films, and both of these parameters could be further enhanced by anti-reflection. VO2-containing nanocomposites had much larger values of T-lum and Delta T-sol than VO2-based films. Mg-doping was found to erode the properties of the nanocomposites. Approximate performance limits are given on T-lum and Delta T-sol for thermochromic VO2 films, with and without Mg doping and antireflection coating, and also for VO2-containing dilute nanocomposites.

  • 193.
    Li, Shuyi
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar A.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, Claes-Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Thermochromics and nanothermochromics: New options for energy efficient fenestration.2011In: Society of Vacuum Coaters 54th Annual Technical Conference Proceedings, Soc. of Vacuum Coaters, Albuquerque, USA., Albuquerque, USA: Society of Vacuum Coaters , 2011, p. 29-34Conference paper (Refereed)
  • 194.
    Li, Shuyi
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar A.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, Claes-Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Thermochromism of VO2 nanoparticles: Calculated optical properties and applications to energy efficient windows.2012In: Materials Research Society Symposium Proceedings, vol. 1315, 2012, p. 101-106Conference paper (Refereed)
  • 195.
    Li, Shuyi
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar A.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, Claes-Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Thermochromism of VO2 Nanoparticles: Calculated Optical. Properties and Applications to Energy Efficient Windows2010Conference paper (Refereed)
  • 196. Li, S.-Y.
    et al.
    Niklasson, Gunnar
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, C.-G.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    VO2-Based Thermochromics and Nanothermochromics for Energy Efficient Applications2011Conference paper (Refereed)
  • 197.
    Lu, J
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics. MSL.
    Hultåker, A
    Niklasson, G A
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics. Fasta tillståndets fysik.
    Granqvist, C G
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics. Fasta tillståndets fysik.
    Olsson, E
    Microstructure of Sputter Deposited Tin Doped Indium Oxide Films with Silver Additive2005In: Thin Solid Films, Vol. 479, p. 107-112Article in journal (Refereed)
  • 198. Lykissa, Iliana
    et al.
    Li, Shuyi
    Ramzan, Muhammad
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Applied Materials Physics, Department of Materials and Engineering, Royal Institute of Technology (KTH), SE-100 44 Stockholm, Sweden.
    Granqvist, Claes-Goran
    Niklasson, Gunnar A.
    Electronic density of states of amorphous vanadium pentoxide films: Electrochemical measurements and density functional theory calculationsManuscript (preprint) (Other academic)
  • 199.
    Lykissa, Iliana
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Li, Shu-Yi
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Ramzan, Muhammad
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Chakraborty, Sudip
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Granqvist, Claes Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar A.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Electronic density-of-states of amorphous vanadium pentoxide films: Electrochemical data and density functional theory calculations2014In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 115, no 18, p. 183701/1-/5Article in journal (Refereed)
    Abstract [en]

    Thin films of V2O5 were prepared by sputter deposition onto transparent and electrically conducting substrates and were found to be X-ray amorphous. Their electrochemical density of states was determined by chronopotentiometry and displayed a pronounced low-energy peak followed by an almost featureless contribution at higher energies. These results were compared with density functional theory calculations for amorphous V2O5. Significant similarities were found between measured data and computations; specifically, the experimental low-energy peak corresponds to a split-off part of the conduction band apparent in the computations. Furthermore, the calculations approximately reproduce the experimental band gap observed in optical measurements.

  • 200. Mageto, M. J.
    et al.
    Maghanga, C. M.
    Mwamburi, M.
    Jafri, Hassan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, C.-G.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Transparent and Conducting TiO2:Nb Thin Films Prepared by Spray Pyrolysis Technique2013Conference paper (Refereed)
1234567 151 - 200 of 378
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