Showing papers by "Claes-Göran Granqvist published in 2015"
TL;DR: In this article, the authors analyzed low-frequency resistance fluctuations in commercial Taguchi gas sensors and the recently developed tungsten trioxide (WO3) gas-sensing layers, exhibiting a photo catalytic effect.
Abstract: Purpose – This paper aims to present the methods of improving selectivity and sensitivity of resistance gas sensors. Design/methodology/approach – This paper compares various methods of improving gas sensing by temperature modulation, UV irradiation or fluctuation-enhanced sensing. The authors analyze low-frequency resistance fluctuations in commercial Taguchi gas sensors and the recently developed tungsten trioxide (WO3) gas-sensing layers, exhibiting a photo-catalytic effect. Findings – The efficiency of using low-frequency fluctuations to improve gas detection selectivity and sensitivity was confirmed by numerous experimental studies in commercial and prototype gas sensors. Research limitations/implications – A more advanced measurement setup is required to record noise data but it will reduce the number of gas sensors necessary for identifying the investigated gas mixtures. Practical implications – Fluctuation-enhanced sensing can reduce the energy consumption of gas detection systems and assures bett...
70 citations
TL;DR: Time-of-flight elastic recoil detection analysis (ToF-ERDA) documented pronounced Li(+) trapping associated with the degradation of the EC properties and, importantly, thatLi(+) detrapping, caused by a weak constant current drawn through the film for some time, could recover the original EC performance.
Abstract: Ion trapping under charge insertion–extraction is well-known to degrade the electrochemical performance of oxides. Galvanostatic treatment was recently shown capable to rejuvenate the oxide, but the detailed mechanism remained uncertain. Here we report on amorphous electrochromic (EC) WO3 thin films prepared by sputtering and electrochemically cycled in a lithium-containing electrolyte under conditions leading to severe loss of charge exchange capacity and optical modulation span. Time-of-flight elastic recoil detection analysis (ToF-ERDA) documented pronounced Li+ trapping associated with the degradation of the EC properties and, importantly, that Li+ detrapping, caused by a weak constant current drawn through the film for some time, could recover the original EC performance. Thus, ToF-ERDA provided direct and unambiguous evidence for Li+ detrapping.
69 citations
TL;DR: In this article, the effectiveness of determining gas concentrations by using a prototype WO3 resistive gas sensor together with fluctuation enhanced sensing was analyzed by using fluctuation-enhanced sensing.
Abstract: This paper analyses the effectiveness of determining gas concentrations by using a prototype WO3 resistive gas sensor together with fluctuation enhanced sensing. We have earlier demonstrated that t ...
56 citations
TL;DR: In this article, thin films of LixWO3-z with 0 <= x <= 0.27 and 0 <= z >= 0.6 were prepared by sputter deposition followed by electrochemical lithiation.
Abstract: Thin films of LixWO3-z with 0 <= x <= 0.27 and 0 <= z <= 0.27 were prepared by sputter deposition followed by electrochemical lithiation. Kramers-Kronig-consistent complex dielectric fu ...
55 citations
TL;DR: It is reported that the incorporation of a modest amount of iridium into NiO films leads to remarkable durability, exceeding 10000 cycles in a lithium-conducting electrolyte, along with significantly improved optical modulation during extended cycling.
Abstract: Anodically colored nickel oxide (NiO) thin films :are of much interest as counter electrodes in tungsten oxide based electrochromic devices such as "smart windows" for energy-efficient buildings. H ...
50 citations
TL;DR: In this article, the authors derived refractive indices and extinction coefficients, as well as scattering and absorption coefficients, of the particle-containing active layer of suspended particle devices (SPDs) to predict direct, total and diffuse components of transmittance and reflectance along with color appearance and haze.
45 citations
TL;DR: In this article, the authors argued that the Kirchhoff-law-Johnson-noise (KLJN) secure key exchange system could experience a se se (e.g.
Abstract: A recent paper by Gunn-Allison-Abbott (GAA) [L. J. Gunn et al., Scientific Reports 4 (2014) 6461] argued that the Kirchhoff-law-Johnson-noise (KLJN) secure key exchange system could experience a se ...
40 citations
TL;DR: In this article, a cotton cloth impregnated with commercial titanium dioxide nanoparticles is used as a photocatalytic filter to clean air contaminated with a model pollutant, while a fan forces air through the filter while it is irradiated by UV diodes.
Abstract: We present a demonstration of online monitoring of gas-phase photocatalytic reactions. A cotton cloth impregnated with commercial titanium dioxide nanoparticles is used as a photocatalytic filter to clean air contaminated with a model pollutant. A fan forces air through the filter while it is irradiated by UV diodes. The concentration of the air pollutant is measured online by an inexpensive, commercially available semiconductor air quality sensor. The structural parts of the reactor were 3D printed in polylactide bioplastic. We provide all schematics, 3D printed model parts, hardware, firmware, and computer code of the reactor and control units. The device can be used for interactive learning of both gas phase photocatalysis and gas sensing, as well as in student laboratory classes for measuring air pollutants and their photodegradation. The experimental setup can also form the basis for a project work for chemical engineering university students, and it can be employed as a building block for development of other gas phase chemical reaction demonstrations.
31 citations
TL;DR: In this article, thermochromic thin films of VO2 were produced by reactive DC magnetron sputtering and characterized by atomic force microscopy, scanning electron microscopy and x-ray diffraction, spectrophotometry, and resistance measurements.
Abstract: Thermochromic thin films of VO2 were produced by reactive DC magnetron sputtering and were characterized by atomic force microscopy, scanning electron microscopy, x-ray diffraction, spectrophotometry, and resistance measurements. Depositions took place onto substrates of glass with and without layers of electrically conducting ITO (i.e., In2O3:Sn) and nonconducting SnO2. The substrate conditions were of large importance; thus, VO2 could be prepared on ITO within a significantly wider process window of oxygen partial pressure than for the other substrates and could yield highly granular deposits. VO2 films on ITO typically showed some lattice compression. Our results are valuable for the preparation and implementation of thermochromic glazings, which are of importance for energy efficient buildings.
27 citations
24 Jul 2015
25 citations
TL;DR: In this article, an almost-one-time-pad-based communication protocol with an unconditionally secure physical key of finite length is proposed, where the physical key is not used for data encryption but is employed in order to generate and share a new software-based key without any known-plain-text component.
Abstract: Unconditionally secure physical key distribution schemes are very slow, and it is practically impossible to use a one-time-pad based cipher to guarantee unconditional security for the encryption of data because using the key bits more than once gives out statistical information, for example via the known-plain-text-attack or by utilizing known components of the protocol and language statistics. Here, we outline a protocol that reduces this speed problem and allows almost-one-time-pad based communication with an unconditionally secure physical key of finite length. The physical, unconditionally secure key is not used for data encryption but is employed in order to generate and share a new software-based key without any known-plain-text component. The software-only-based key distribution is then changed from computationally secure to unconditionally secure, because the communicated key-exchange data (algorithm parameters, one-way functions of random numbers, etc.) are encrypted in an unconditionally secure way with a one-time-pad. For practical applications, this combined physical/software key distribution based communication looks favorable compared to the software-only and physical-only key distribution based communication whenever the speed of the physical key distribution is much lower than that of the software-based key distribution. A mathematical security proof of this new scheme remains an open problem.
Abstract: We demonstrate a quantitative relation between exposed crystal surfaces and photocatalytic activity of nanocrystalline anatase TiO2. Thin films with controlled amount of 〈001〉 preferential orientation were prepared by reactive DC magnetron sputtering in Ar/O2 atmosphere with the partial O2 pressure as control parameter. The samples were characterized with X-ray diffraction, transmission electron microscopy and atomic force microscopy, from which the degree of preferential 〈001〉 orientation and exposed facets were determined by an extension of the March–Dollase model. Photocatalytic degradation of methylene blue dye shows that the photocatalytic reaction rate increases approximately with the square of the fraction of 〈001〉 oriented surfaces, with about eight times higher rate on the {001} surfaces, than on {101}, thus quantifying the effect of crystal facet abundancy on the photocatalytic activity of anatase TiO2.
TL;DR: In this article, the percolating semiconducting and metallic-like properties of lattice lattice percolation with switching disorder are discussed. But the authors do not consider the effect of random defect generation and healing in steady state.
Abstract: Thermochromic VO2 films were prepared by reactive DC magnetron sputtering onto heated sapphire substrates and were used to make 100-nm-thick samples that were 10 μm wide and 100 μm long. The resistance of these samples changed by a factor ∼2000 in the 50 Tc. These exponents can be reconciled with the Pennetta–Trefan–Reggiani theory [Pennetta et al., Phys. Rev. Lett. 85, 5238 (2000)] for lattice percolation with switching disorder ensuing from random defect generation and healing in steady state. Our work hence highlights the dynamic features of the percolating semiconducting and metallic-like regio...
TL;DR: A mathematical scheme introduced in advanced nanotechnology is relevant for the analysis of this mechanism in the simplest case, the integrate-and-fire model with white noise in the charging ion current.
Abstract: Even a single neuron may be able to produce significant lognormal features in its firing statistics due to noise in the charging ion current. A mathematical scheme introduced in advanced nanotechnology is relevant for the analysis of this mechanism in the simplest case, the integrate-and-fire model with white noise in the charging ion current.
02 Jun 2015
TL;DR: In this article, it was shown that an error-free Turing computer works in the zero-entropy limit, which proves Landauer's derivation incorrect, and that bit erasure is typically not needed or used for the functioning of computers or engines.
Abstract: We briefly address Landauer's Principle and some related issues in thermal demons. We show that an error-free Turing computer works in the zero-entropy limit, which proves Landauer's derivation incorrect. To have a physical logic gate, memory or information-engine, a few essential components necessary for the operation of these devices are often neglected, such as various aspects of control, damping and the fluctuation-dissipation theorem. We also point out that bit erasure is typically not needed or used for the functioning of computers or engines (except for secure erasure).
Posted Content•
TL;DR: In this article, the authors address the question of low-frequency signals in a short cable, which are often considered as waves in engineering calculations, but exact calculations can be carried out via linear network theory.
Abstract: We address the question of low-frequency signals in a short cable, which are often considered as waves in engineering calculations. Such an assumption violates several laws of physics, but exact calculations can be carried out via linear network theory.
TL;DR: In this paper, it was shown that neural spikes in the brain form stochastic sequences, i.e., belong to the class of pulse noises, which is a counterintuitive feature because extracting information such as the commonly supposed neural information of mean spike frequency requires long times for reasonably low error probability.
Abstract: Neural spikes in the brain form stochastic sequences, i.e., belong to the class of pulse noises. This stochasticity is a counterintuitive feature because extracting information—such as the commonly supposed neural information of mean spike frequency—requires long times for reasonably low error probability. The mystery could be solved by noise-based logic, wherein randomness has an important function and allows large speed enhancements for special-purpose tasks, and the same mechanism is at work for the brain logic version of this concept.
TL;DR: In this paper, an asymmetric random telegraph wave-based instantaneous noise-base logic scheme was used to represent the problem of drawing numbers from a hat, and two identical hats with the first 2^N integer numbers were considered.
Abstract: We utilize the asymmetric random telegraph wave-based instantaneous noise-base logic scheme to represent the problem of drawing numbers from a hat, and we consider two identical hats with the first 2^N integer numbers. In the first problem, Alice secretly draws an arbitrary number from one of the hats, and Bob must find out which hat is missing a number. In the second problem, Alice removes a known number from one of the hats and another known number from the other hat, and Bob must identify these hats. We show that, when the preparation of the hats with the numbers is accounted for, the noise-based logic scheme always provides an exponential speed-up and/or it requires exponentially smaller computational complexity than deterministic alternatives. Both the stochasticity and the ability to superpose numbers are essential components of the exponential improvement.
Journal Article•
TL;DR: Optical Absorption and Small-Polaron Hopping in Oxygen Deficient and Lithium Intercalated Amorphous Tungsten Oxide Films.
Abstract: Optical Absorption and Small-Polaron Hopping in Oxygen Deficient and Lithium Intercalated Amorphous Tungsten Oxide Films
01 Nov 2015
TL;DR: In this paper, nanocrystalline nickel-oxide-based thin films were prepared by advanced reactive gas deposition, and the response of these films to formaldehyde was studied by fluctuation-enhanced sensing.
Abstract: Nanocrystalline nickel-oxide-based thin films were prepared by advanced reactive gas deposition, and the response of these films to formaldehyde was studied by fluctuation-enhanced sensing. Morphological and structural analyses showed porous deposits of nickel oxide particles with face-centered cubic structure. Resistance fluctuations were measured upon exposure to ethanol, formaldehyde and methane at 200 °C. Power density spectra were used to quantify the response. The response to formaldehyde was higher than to ethanol at 200 °C, and no significant response was observed for methane thus demonstrating some gas-species selectivity.
Posted Content•
TL;DR: It is shown that an error-free Turing computer works in the zero-entropy limit, which proves Landauer's derivation incorrect, and points out that bit erasure is typically not needed or used for the functioning of computers or engines (except for secure erasure).
Abstract: We briefly address Landauer’s Principle and some related issues in thermal demons. We show that an error-free Turing computer works in the zero-entropy limit, which proves Landauer’s derivation incorrect. To have a physical logic gate, memory or information-engine, a few essential components necessary for the operation of these devices are often neglected, such as various aspects of control, damping and the fluctuation–dissipation theorem. We also point out that bit erasure is typically not needed or used for the functioning of computers or engines (except for secure erasure).
Proceedings Article•
01 Jan 2015TL;DR: In this paper, the authors address the question of low-frequency signals in a short cable, which are often considered as waves in engineering calculations, and show that such an assumption violates several laws of physics, but exact ca
Abstract: We address the question of low-frequency signals in a short cable, which are often considered as waves in engineering calculations. Such an assumption violates several laws of physics, but exact ca ...
16 Jul 2015
TL;DR: In this article, the authors proposed a method to construct a durable smart window for many years of service life using a thin film of thin films of electrochromic materials. But, their method is not suitable for high temperature and humidity.
Abstract: Most electrochromic devices, such as “smart windows” for energy efficient glazings, must be durable enough for many years of service life. Typical constructions use films based on thin films of W o ...
Posted Content•
TL;DR: In this article, the authors introduce information-theoretic erasure based on Shannon's binary channel formula, which is a natural energy-dissipation-free way in which information is lost in double-potential-well memories.
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.
TL;DR: 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.
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.
Posted Content•
TL;DR: In this paper, the authors show that the claim of zero-point noise directly contradicts the Fermi-Dirac distribution, which defines the thermodynamics of electrons according to quantum-statistical physics.
Abstract: The Callen-Welton formula (fluctuation-dissipation theorem) of voltage and current noise of a resistance are the sum of Nyquist's classical Johnson noise equations and a (quantum) zero-point term with power density spectrum proportional to frequency and independent of temperature. At zero temperature, the classical Nyquist term vanishes however the zero-point term produces non-zero noise voltage and current. We show that the claim of zero-point noise directly contradicts to the Fermi-Dirac distribution, which defines the thermodynamics of electrons according to quantum-statistical physics. As a consequence, the Johnson noise must be zero at zero temperature, which is in accordance with Nyquist's original formula. Further investigation shows that the Callen-Welton derivation has conceptual errors such as neglecting phonon scattering, disregarding the Pauli principle during calculating the transition probabilities and using bosonic (linear oscillator) energies leading to the zero-point noise artifact. Following Kleen's proposal, the possible origin of the heterodyne (Koch - van Harlingen - Clark) experimental results are also discussed in terms of Heffner theory of quantum noise of frequency/phase-sensitive linear amplifiers. Experiments that failed to see the zero-point noise term are also mentioned.