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.

Demons: Maxwell's demon, Szilard's engine and Landauer's erasure-dissipation

Abstract: This talk addressed the following questions in the public debate at HoTPI: (i) energy dissipation limits of switches, memories and control; (ii) whether reversible computers are possible, or does their concept violate thermodynamics; (iii) Szilard's engine, Maxwell's demon and Landauer's principle: corrections to their exposition in the literature; (iv) whether Landauer's erasure–dissipation principle is valid, if the same energy dissipation holds for writing information, or if it is invalid; and (v) whether (non-secure) erasure of memories, or the writing of the same amount of information, dissipates most heat.

Optical properties of cermet materials

Abstract: Cermet films can show a spectral selectivity which makes them well suited for efficient photothermal conversion of solar energy. Sufficieritly fine-grained materials can be theoretically understood from effective medium theories. Two formulations apply depending on the microstructure topology ; the Maxwell Garnett theory is valid for metallic particles embedded in an insulating host, whereas the Bruggeman theory holds for a random mixture of metallic and insulating particles. We discuss extensions to treat size dependent electron scattering, shape and orientation effects, and the role of local aggregation. The theories are applied to several types of cermets : discontinuous metal films, gas evaporated coatings, coevaporated and cosputtered layers, electrodeposited films, and electrolytically and integrally coloured anodic aluminium oxide coatings. Successes and failures of the theoretical models are discussed and remaining uncertainties are pointed out. One general conclusion is that effective medium theories are very useful for understanding the optical properties both qualitatively and quantitatively. Another general result is that lack of sufficiently accurate sample characterization is still hampering further progress for several types of technologically interesting cermets.

Quantitative relation between photocatalytic activity and degree of 〈001〉 orientation for anatase TiO2 thin films

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.

Progress in Electrochromics: Tungsten Oxide Revisited

Abstract: This paper reviews recent work on electrochromic W-oxide-based films and devices Computed data an presented for electronic structure and optical properties of crystalline WO3. Techniques for mak ...

Higher-order spectra in nanoparticle gas sensors

Abstract: It has previously been shown that resistance fluctuations in resistive sensors provide enhanced sensitivity and selectivity for gas detection. We report measurements and analysis of non-Gaussian components in nanoparticle Pdz(WO3)1-z film gas sensors, with z being 0.01 or 0.12, in different ambients. These components can be characterized by higher-order spectra. Contour plots are given of bispectra, and plots of integrated bispectra and trispectra. The phase of the integrated higher-order spectra is analyzed as well.

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.