Showing papers by "Claes-Göran Granqvist published in 2016"

Ion Trapping and Detrapping in Amorphous Tungsten Oxide Thin Films Observed by Real-Time Electro-Optical Monitoring

Abstract: Several technologies for energy saving and storage rely on ion exchange between electrodes and electrolytes. In amorphous electrode materials, a detailed knowledge of Li-ion intercalation is hamper ...

Electrochromics and thermochromics : towards a new paradigm for energy efficient buildings

Abstract: Modern buildings normally have large windows and glass facades, known jointly as glazings, for achieving good day-lighting and indoors-outdoors contact. However, glazings are challenging for the bu ...

Fluctuation enhanced gas sensing with WO3-based nanoparticle gas sensors modulated by UV light at selected wavelengths

Abstract: The sensitivity and selectivity of WO 3 -based gas sensors can be enhanced by UV-irradiation-induced modulation, especially if different wavelengths are employed. We used fluctuation-enhanced gas sensing, based on measurements of resistance fluctuations in the gas sensor, to study the effects of such modulation on the noise intensity for ambient atmospheres of synthetic air without and with additions of small amounts of ethanol, methane and formaldehyde. Our data confirmed that the method is energy efficient and can be applied to improve gas detection sensitivity and selectivity. The results are strongly dependent on the gaseous species, and a single UV-modulated WO 3 -based gas sensor discriminate between different gases.

Thermochromic Oxide-Based Thin Films and Nanoparticle Composites for Energy-Efficient Glazings

Abstract: Today’s advances in materials science and technology can lead to better buildings with improved energy efficiency and indoor conditions. Particular attention should be directed towards windows and glass facades—jointly known as “glazings”—since current practices often lead to huge energy expenditures related to excessive inflow or outflow of energy which need to be balanced by energy-intensive cooling or heating. This review article outlines recent progress in thermochromics, i.e., it deals with materials whose optical properties are strongly dependent on temperature. In particular, we discuss oxide-based thin surface coatings (thin films) and nanoparticle composites which can be deposited onto glass and are able to regulate the throughput of solar energy while the luminous (visible) properties remain more or less unaltered. Another implementation embodies lamination materials incorporating thermochromic (TC) nanoparticles. The thin films and nanocomposites are based on vanadium dioxide (VO2), which is able to change its properties within a narrow temperature range in the vicinity of room temperature and either reflects or absorbs infrared light at elevated temperatures, whereas the reflectance or absorptance is much smaller at lower temperatures. The review outlines the state of the art for these thin films and nanocomposites with particular attention to recent developments that have taken place in laboratories worldwide. Specifically, we first set the scene by discussing environmental challenges and their relationship with TC glazings. Then enters VO2 and we present its key properties in thin-film form and as nanoparticles. The next part of the article gives perspectives on the manufacturing of these films and particles. We point out that the properties of pure VO2 may not be fully adequate for buildings and we elaborate how additives, antireflection layers, nanostructuring and protective over-coatings can be employed to yield improved performance and durability that make TC glazings of considerable interest for building-related applications. Finally, we briefly describe recent developments towards TC light scattering and draw some final conclusions.

Electrochromics for energy efficient buildings: Towards long-term durability and materials rejuvenation

Abstract: Electrochromic devices such as "smart windows" for energy efficient windows must be durable enough for many years of practical use. Typical devices employ films based on W oxide and Ni oxide, and t ...

Electrochromic Iridium-Containing Nickel Oxide Films with Excellent Electrochemical Cycling Performance

Abstract: Electrochromic Ni oxide thin films attract much interest because of their large potential for applications as optically active layers in energy-saving and comfort enhancing smart windows in buildin ...

UV-Light-Induced Fluctuation Enhanced Sensing by WO 3 -Based Gas Sensors

Abstract: WO3-based gas sensors were investigated under UV-light irradiation and at different working temperatures with the object of achieving superior sensitivity and selectivity. Resistance fluctuations in the WO3 layer were studied together with dc resistance measurements. The data were taken in synthetic air, ethanol, nitrogen dioxide, and mixtures of these gases. We conclude that UV irradiation can easily be applied to enhance the gas sensing properties of a WO3 layer.

Comments On "A New Transient Attack On The Kish Key Distribution System"

Abstract: A recent IEEE Access Paper by Gunn, Allison and Abbott (GAA) proposed a new transient attack against the Kirchhoff-law-Johnson-noise (KLJN) secure key exchange system. The attack is valid, but it i ...

Comments On "A New Transient Attack On The Kish Key Distribution System"

Abstract: A recent IEEE Access Paper by Gunn, Allison and Abbott (GAA) proposed a new transient attack against the Kirchhoff-law-Johnson-noise (KLJN) secure key exchange system. The attack is valid, but it is easy to build a defense for the KLJN system. Here we note that GAA's paper contains several invalid statements regarding security measures and the continuity of functions in classical physics. These deficiencies are clarified in our present paper, wherein we also emphasize that a new version of the KLJN system is immune against all existing attacks, including the one by GAA.

Optical absorption and small-polaron hopping in oxygen deficient and lithium-ion-intercalated amorphous titanium oxide films

Abstract: Optical absorption in oxygen-deficient and Li+-ion inserted titanium oxide films was studied in the framework of small-polaron hopping. Non-stoichiometric TiOy films with 1.68 <= y <= 2.00 we ...

Thermochromics for Energy Efficient Buildings: Thin Surface Coatings and Nanoparticle Composites

Abstract: This chapter outlines the state of the art of the thermochromic glazings that are able to provide energy efficiency by letting in more solar energy at a low temperature than at a high temperature, thereby leading to diminished need for space cooling. Thermochromic technology employs VO2-based materials as thin coatings or nanoparticle composites. For coatings, suitable switching between conditions with high and low solar energy throughput at low and high temperature, respectively, can be achieved by replacing some of the vanadium atoms by tungsten, and luminous transmittance can be enhanced by the addition of some magnesium. Antireflection (AR) coatings can give further improvements. By going to nanoparticle composites with VO2 dispersed in a transparent host, it is possible to combine high luminous transmittance with large modulation of solar energy transmittance. This modulation ensues from plasmonic absorption in metallic-like VO2 nanoparticles. Thermochromic glazings are not yet (2015) available as products, but the rapid development during recent years has led to performance limits that appear very interesting for practical applications. Energy modeling of buildings with thermochromic glazings points at very substantial savings. A further development may be to integrate thermochromic nanoparticles in laminated electrochromic devices.

Rejuvenation of degraded electrochromic MoO3 thin films made by DC magnetron sputtering: Preliminary results

Abstract: Molybdenum oxide thin films were deposited by reactive DC magnetron sputtering and were subjected to voltammetric cycling in an electrolyte comprised of lithium perchlorate in propylene carbonate. The films were heavily degraded during 20 voltammetric cycles in an extended voltage range. The films were subsequently rejuvenated by use of potentiostatic treatments under different voltages during 20 hours. Optical changes were recorded during the electrochemical degradation and ensuing rejuvenation.

Zero and negative energy dissipation at information-theoretic erasure

Abstract: We introduce information-theoretic erasure based on Shannon's binary channel formula. It is pointed out that this type of erasure is a natural energy-dissipation-free way in which information is lost in double-potential-well memories, and it may be the reason why the brain can forget things effortlessly. We also demonstrate a new non-volatile, charge-based memory scheme wherein the erasure can be associated with even negative energy dissipation; this implies that the memory's environment is cooled during information erasure and contradicts Landauer's principle of erasure dissipation. On the other hand, writing new information into the memory always requires positive energy dissipation in our schemes. Finally, we show a simple system where even a classical erasure process yields negative energy dissipation of arbitrarily large energy.

Zero Thermal Noise in Resistors at Zero Temperature

Abstract: The bandwidth of transistors in logic devices approaches the quantum limit, where Johnson noise 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.

Sputter-Deposited Indium-Tin Oxide Thin Films for Acetaldehyde Gas Sensing

Abstract: Reactive dual-target DC magnetron sputtering was used to prepare In-Sn oxide thin films with a wide range of compositions. The films were subjected to annealing post-treatment at 400 degrees C or 5 ...

Electrochromism in sputter deposited W1-y MoyO3 thin films

Abstract: Electrochromic (EC) properties of tungsten-molybdenum oxide (W1-y MoyO3) thin films were investigated The films were deposited on indium tin oxide covered glass by reactive DC sputtering from tungsten and molybdenum targets Elemental compositions of the W1-y MoyO3 films were determined by Rutherford back scattering Voltammetric cycling was performed in an electrolyte of 1 M LiClO4 in propylene carbonate An increase in molybdenum content in the EC films caused both a shift towards higher energies and a lowering of the maximum of the optical absorption band, as compared with WO3 EC films Durability under electrochemical cycling was diminished for W1-y MoyO3 EC films

Response to Comment on `Zero and negative energy dissipation at information-theoretic erasure'

Abstract: We prove that statistical information-theoretic quantities, such as information entropy, cannot generally be interrelated with the lower limit of energy dissipation during information erasure. We also point out that, in deterministic and error-free computers, the information entropy of memories does not change during erasure because its value is always zero. On the other hand, for information-theoretic erasure--i.e., "thermalization"/randomization of the memory--the originally zero information entropy (with deterministic data in the memory) changes after erasure to its maximum value, 1 bit/memory bit, while the energy dissipation is still positive, even at parameters for which the thermodynamic entropy within the memory cell does not change. Information entropy does not convert to thermodynamic entropy and to the related energy dissipation; they are quantities of different physical nature. Possible specific observations (if any) indicating convertibility are at most fortuitous and due to the disregard of additional processes that are present.

Thermochromic light scattering from particulate VO2 layers

Abstract: Particulate layers of thermochromic (TC) VO2 were made by reactive DC magnetron sputtering of vanadium onto In2O3:Sn-coated glass. The deposits were characterized by scanning electron microscopy, atomic force microscopy, and X-ray diffraction. Specular and diffuse optical transmittance and reflectance were recorded in the 300–2500-nm wavelength range and displayed pronounced TC effects. These properties could be reconciled with a semi-quantitative model based on Lorentz–Mie theory applied to the distribution of particle sizes and accounting for particle shapes by the Grenfell–Warren approach with equal-volume-to-area spheres.

Plasmonic thin films for application in improved chromogenic windows

Abstract: Nanocomposites consisting of noble metal nanoparticles in a transparent matrix exhibit plasmonic absorption in the visible wavelength range, and conducting oxide nanoparticles display a localized plasma absorption in the near infrared The optical properties of nanocomposites are commonly modelled by effective medium theories, which describe the effective dielectric function of the composite using as input the dielectric functions of the constituents and their respective volume fractions Plasmonic effects can be exploited in the design of energy-efficient windows in order to obtain improved performance Electrochromic coatings that switch in the near infrared make use of the modulation of the plasma absorption of oxide nanoparticles due to charge density modulation induced by an external voltage Plasmonic thermochromic switching in the near infrared has the potential to be significantly larger than in the case of a thin film Very thin noble metal films are an interesting alternative to conducting oxides as transparent contacts to electrochromic devices However, in this latter case plasmonic effects are to be avoided rather than exploited

Thermochromic vanadium-dioxide-based thin films and nanoparticles: Survey of some buildings-related advances

Abstract: Today’s architecture uses large glazings (windows and glass facades) to obtain good indoors–outdoors contact and day-lighting. However glazings offer challenges and often lead to excessive solar en ...

Sputter deposited W1–x–yNixTiyO3 thin films: Electrochromic properties and durability

Abstract: Previous research demonstrated that a small amount of nickel enhances the coloration efficiency of tungsten-nickel oxide electrochromic (EC) thin films with respect to that of pure tungsten oxide (WO3) films Furthermore the incorporation of titanium gives an improvement in the durability of tungsten-titanium oxide EC thin films In this work we investigated the EC performance of tungsten-nickel-titanium oxide (W1–x–yNixTiyO3) EC thin films with emphasis on durability The films were deposited on indium tin oxide covered glass by reactive dc sputtering from tungsten, tungsten-titanium alloy and nickel targets Cyclic voltammetry was performed using 1 M LiClO4 in propylene carbonate as electrolyte The voltage window was chosen to induce fast degradation of the samples within 80 cycles Elemental compositions were obtained by Rutherford Backscattering Spectroscopy