Claes-Göran Granqvist

Bio: Claes-Göran Granqvist is an academic researcher from Uppsala University. The author has contributed to research in topics: Electrochromism & Thin film. The author has an hindex of 73, co-authored 535 publications receiving 31523 citations. Previous affiliations of Claes-Göran Granqvist include Chalmers University of Technology & Texas A&M University.

On the security of the Kirchhoff-law-Johnson-noise (KLJN) communicator

Abstract: A simple and general proof is given for the information theoretic (unconditional) security of the Kirchhoff-law-Johnson-noise (KLJN) key exchange system under practical conditions. The unconditional security for ideal circumstances, which is based on the Second Law of Thermodynamics, is found to prevail even under slightly non-ideal conditions. This security level is guaranteed by the continuity of functions describing classical physical linear, as well as stable non-linear, systems. Even without privacy amplification, Eve's probability for successful bit-guessing is found to converge towards 0.5 - i.e., the perfect security level - when ideal conditions are approached.

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.

Lithium intercalation in sputter deposited antimony-doped tin oxide thin films : Evidence from electrochemical and optical measurements

Abstract: Transparent conducting oxides are used as transparent electrical contacts in a variety of applications, including in electrochromic smart windows. In the present work, we performed a study of transparent conducting antimony-doped tin oxide (ATO) thin films by chronopotentiometry in a Li+-containing electrolyte. The open circuit potential vs. Li was used to investigate ATO band lineups, such as those of the Fermi level and the ionization potential, as well as the dependence of these lineups on the preparation conditions for ATO. Evidence was found for Li+ intercalation when a current pulse was set in a way so as to drive ions from the electrolyte into the ATO lattice. Galvanostatic intermittent titration was then applied to determine the lithium diffusion coefficient within the ATO lattice. The electrochemical density of states of the conducting oxide was studied by means of the transient voltage recorded during the chronopotentiometry experiments. These measurements were possible because, as Li+ intercalation took place, charge compensating electrons filled the lowest part of the conduction band in ATO. Furthermore, the charge insertion modified the optical properties of ATO according to the Drude model.

Switchable Glazing Technology: Electrochromic Fenestration for Energy-Efficient Buildings

Abstract: Switchable electrochromic glazings employ multilayer devices with a basic resemblance to thin-film electrical batteries and color/bleach upon electrical charging/discharging. The transmittance of visible light and solar energy can be varied reversibly and persistently between widely separated extrema, which makes it possible to regulate solar energy inflow for energy savings as well as visible light level for comfort reasons. This chapter outlines the basics of electrochromic glazing technology and its implementation in buildings. Device designs and component materials are discussed in some detail. Several practical electrochromic glazing designs are introduced with focus on a foil-type construction applicable as a lamination material between glass panes. Electrochromic glazing has been discussed for many years and has many unfulfilled promises; it is argued here that today’s developments are likely to change this situation so that electrochromic glazing will be able to take its proper place as an important energy savings and comfort enhancing technology for near-zero-energy building refurbishment as well as for new buildings.

Graphene photonics and optoelectronics

Abstract: The richness of optical and electronic properties of graphene attracts enormous interest. Graphene has high mobility and optical transparency, in addition to flexibility, robustness and environmental stability. So far, the main focus has been on fundamental physics and electronic devices. However, we believe its true potential lies in photonics and optoelectronics, where the combination of its unique optical and electronic properties can be fully exploited, even in the absence of a bandgap, and the linear dispersion of the Dirac electrons enables ultrawideband tunability. The rise of graphene in photonics and optoelectronics is shown by several recent results, ranging from solar cells and light-emitting devices to touch screens, photodetectors and ultrafast lasers. Here we review the state-of-the-art in this emerging field.