T. Lindström

Towards the smart window : progress in electrochromics

Electrochromic devices have the ability to produce reversible and persistent changes of their optical properties. The phenomenon is associated with joint ion and electron transport into/out of an electrochromic thin film, in most cases being a transition metal oxide. This paper outlines the various applications of such devices in smart windows suitable for energy-conscious architecture, in variable-reflectance mirrors, and in display devices. Critical materials issues and design concepts are discussed. The paper also covers two specific research topics: computed electronic structure of crystalline WO3 incorporating ionic species, showing how reflectance modulation emerges from a first-principles calculation; and Li+ dynamics in heavily disordered Ti oxide, illustrating how diffusion constants derived from impedance spectroscopy can be reconciled with the Anderson—Stuart model.

A fuzzy design of the willingness to invest in Sweden

Abstract This paper uses a non-linear fuzzy logic procedure to empirically investigate the links between the real interest rate and aggregate investments in Sweden from 1950 to 1990. The economic environment is characterized by multivalued logic and an indicator for the economy-wide investment climate is derived strictly from the interest rate. It turns out that the fuzzy logic approach may reveal some empirical regularities that are not recognized by conventional linear regressions.

Surface smoothing and roughening in sputtered SnO2 films

Abstract In this paper we study the scaling of the surface roughness in regimes of smoothing and roughening. Transparent SnO2 films are sputtered onto rough glass substrates, and films in the thickness range 15–1200 nm are produced. Surface images are obtained by atomic force microscopy. Specifically we are able to determine the effect on the roughness exponent upon a transition from smoothing to roughening regimes, and it is found that the surface width scales differently in the two regions. To our knowledge this has not been seen before, and we are not aware of a theoretical explanation of this. For thinner films smoothing effects reduces the surface roughness as compared to the substrate, and the correlation length decreases. On the other hand, for thicker films the surface width increases with thickness again. For the thinner films the roughness exponent is in the range 0.5–0.7, and for the thicker films it is approximately 0.9–1. The growth exponent is found to be approximately 0.3.

International round-robin experiment to test the International Organization for Standardization total-scattering draft standard

An international round-robin experiment has been conducted among laboratories in different countries to test the measurement and the data-analysis procedures in the International Organization for Standardization draft standard ISO/DIS 13696 for measuring total scattering from low-scatter laser optics. Ten laboratories measured total backscattering from high-reflectance mirrors, 50% beam splitters, and antireflection-coated windows. Results were sent to the Laser Zentrum Hannover, which acted as coordinator and analyzed all the backscattering data. The results showed that the procedure in the draft standard was useful for measuring and reporting backscattering for low-scatter optics. Problems encountered in the round-robin experiment included the accumulation of particles on the surfaces, particularly on the high-reflectance mirrors.

Total integrated scattering from transparent substrates in the infrared region: validity of scalar theory

Integrated light scattering, from thin, transparent silicon wafers with different front and backside surface roughness is investigated. The measurements are made at near normal incidence in the IR ...

Electrochromic control of thin film light scattering

Total and diffuse reflectance spectra were measured on Al surfaces covered with electrochromic W oxide films in colored and bleached states. Vector perturbation theory was used for analyzing the spectra. The diffuse reflectance appeared to originate from correlated (uncorrelated) interface roughness when the W oxide film was fully colored (bleached). Assuming partially correlated interfaces led to agreement between experimental and calculated spectra. The use of an electrochromic film appears a promising method to control the relative contributions of the interfaces to the resulting scattering.

High performing micromachined retroreflector

This paper reports on the realization of a type of micromachined retroreflecting sheeting material. The geometry presented has high reflection efficiency even at large incident angles, and it can be manufactured through polymer replication techniques. The paper consists of two parts: A theoretical section outlining the design parameters and their impact on the optical performance, and secondly, an experimental part comprising both manufacturing and optical evaluation for a candidate retroreflecting sheet material in traffic control devices. Experimental data show that the retroreflecting properties are promising. The retroreflector consists of a front layer of densely packed spherical microlenses, a back surface of densely packed spherical micromirrors, and a transparent spacer layer. The thickness of the spacer layer determines in part the optical characteristics of the retroreflector.

Adsorption and Electrodeposition on SnO2 and WO 3 Electrodes in 1 M LiClO4 PC In Situ Light Scattering and In Situ Atomic Force Microscopy Studies

A novel spectroscopic in situ light scattering technique was used with in situ atomic force microscopy (AFM) to study electrode surfaces subjected to adsorption and electrodeposition. Tin dioxide and tungsten trioxide were used as electrodes in a 1 M LiClO 4 /propylene carbonate electrolyte. Both in situ methods showed the same increase in surface roughness immediately after the electrode was immersed in the electrolyte. The onset potential for electrodeposition could be determined; its specific value depended on the film composition as well as on the composition and purity of the electrolyte. A potential step technique revealed a progressive growth of the first electrodeposited layer. The growth mode after fully developed electrodeposition was characterized by a preferential growth of large crystals, evident from light scattering as well as AFM. Our experimental techniques make it possible to determine whether electrodeposition or electrochromism, due to electrochemical insertion of ionic species, dominates the observed modulation of the optical properties. The deposited layer was investigated using infrared spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. Although the composition of this layer cannot be stated conclusively, it most likely contains lithium alkyl carbonate species.

Theoretical Analysis of Chronoamperometric Electrochemical Ion Intercalation

We propose that the intercalation of ions from a liquid electrolyte into a solid material can be analyzed in terms of a model [J. Appl. Phys., 55, 3341 (1984)] developed for the release of alkali ions from interface traps in a metal-oxide silicon structur

Surface roughness in sputtered SnO2 films studied by atomic force microscopy and spectroscopic light scattering

In this paper we study the growth of surface roughness during sputtering of transparent SnO2 films onto rough glass substrates. Films in the thickness range 50–1200 nm were produced, and the optical characterization was made with a spectroscopic total integrating scattering instrument in the wavelength range 0.35<λ<1.0 μm. Optical constants for the different SnO2 films were determined. The observed spectral behavior of the diffuse reflectance (transmittance), as compared to the total reflectance (transmittance), could be explained by first-order vector perturbation theory in conjunction with a surface growth model incorporating both smoothing and roughening effects. Good agreement between calculated and measured reflectance and transmittance spectra was found, only by assuming partially correlated interface roughness. The scattering calculations rely on atomic force microscope measurements of the glass substrate and the front surfaces of the films, and a model of the cross correlation that describes the p...