Untersuchung gasochrom schaltender Wolframoxide
| Autor: | Weis, Hansjörg |
|---|---|
| Přispěvatelé: | Wuttig, Matthias |
| Jazyk: | němčina |
| Rok vydání: | 2002 |
| Předmět: |
optical properties
schaltbar elektrochrom XRD analysis tungsten dc-magnetron sputtering XRR Wolframoxide Magnetronsputtern Physik WOx WO3 adaptive glazing ddc:530 Wolframoxid switchable Oxid Adaptive Verglasung index of refraction Röntgenreflektometrie electrochromic Schalten dielectric function Wolfram DC-Magnetron Sputtern Dünne Schicht gasochrom gaschromic Intelligente Fenster switch Optik Gasochrome Schicht smart windows gaschrom thin films Optic electrochrom oxide schaltfähig Palladium Wasserstoff Optische Eigenschaft Hydrogen |
| Zdroj: | Aachen : Publikationsserver der RWTH Aachen University XIV, 237 S. : Ill., graph. Darst. (2002). = Aachen, Techn. Hochsch., Diss., 2002 |
| Popis: | Analysis of gasochromic switching tungsten oxide layers This thesis describes the properties of reactively dc-magnetron sputtered tungsten oxide (WOx) films. The films are gasochromically switched with diluted hydrogen (H2) in argon or nitrogen, with a very thin surface film of palladium (Pd) as catalyst. The bleaching process happens in oxygen containing atmosphere similar to the reduction and oxidation process known from electrochromic switching. By switching the WOx films, its optical properties change from a transparent state, between the infrared (IR) and ultraviolett (UV), to an absorbing state, in the near infrared. The results portend a big application potential, for a few hundreds nanometer thin functional layer, for energy regulation purposes in 'smart windows' or 'adaptive glazings”. The observed absorption state is ascribed to the creation of small polarons. The main goal of the thesis was to gain a better understanding for the correlations between sputter-deposition parameters and the resulting layer- and switching properties. A new model succeeded in describing the lateral, inhomogeneous switching of the samples. The dependence of the switching behaviour from system parameters like thicknesses of the WOx- or Pd-layers or the hydrogen partial pressure was analyzed in more detail and compared with models from literature dealing with kinetics and thermodynamics. To characterize the coatings, X-ray reflectometry (XRR), optical spectroscopy and in-situ time resolved spectroscopy were mainly used. The determination of relevant physical properties like density, thickness and roughness or the dielectric function (DF) ( index of refraction and absorption index), was achieved by analysis of the measurements with suitable simulation programs. Refinement of existing algorithms was necessary to reveal some minute but significant details. By increase of deposition pressure there was thermalization of high energy incident particles on the growing film. This resulted in more porous and less dense films, which showed a faster switching behaviour. Moreover, the laterally inhomogeneous switching behaviour of the samples could be correlated with the target erosion profile. Its shape determined where fast or thermalized particles impinged on the substrate, causing a more or less dense film growth. The link between density and index of refraction was done via the Lorentz-Lorenz-relation. The application of prevailing models of kinetics in literature enabled time dependent simulation of the measured coloration centers concentration. Identification of the matching simulation led to a classification of the layers into those of fast or slow diffusion according to models from the literature. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|