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Papers by george bader

Sid Symposium Digest of Technical Papers, 1998

Thin Solid Films, 2008

Electrochromic properties of porous nanostructured thin films of tungsten trioxide were investiga... more Electrochromic properties of porous nanostructured thin films of tungsten trioxide were investigated. Films were fabricated at normal and high vapor incidence angles with the technique of glancing angle deposition in a thermal evaporation chamber. A dry lithiation method was subsequently used to intercalate films with lithium atoms. Coloration in both visible and near-infrared regions was observed with lithium insertion. We report on the morphology, porosity, and optical properties of as-deposited and lithiated films, and discuss the role of substrate tilt in comparing the coloration efficiency of these films.

Journal of Non-crystalline Solids, 2002

Nanocrystalline titania ®lms were prepared by a complexing agent-assisted sol±gel method and conv... more Nanocrystalline titania ®lms were prepared by a complexing agent-assisted sol±gel method and converted to titanium nitride by a thermal nitridation process. The eect of acetylacetone (AcAc), diethanolamine (DEA) and acid catalysts (HCl and HNO 3 ) on the structure and morphology of the heat-treated titania ®lms and on their nitridation products was examined by FTIR spectroscopy, X-ray diraction (XRD) and atomic force microscopy (AFM). The carbothermal reduction of titania during the nitridation process with the formation of carboxynitrides has been considered. The results showed that the oxide to nitride transition strongly depends on the complexing agent used to prepare the titania ®lms. The XRD results indicated the dependence of the lattice parameter of the nitridation product on the complexing agent or acid catalyst: AcAc and DEA lead to TiN x with a lattice parameter a close to the theoretical value, while with HCl the lattice parameter was found sensibly lower showing the presence of an oxynitride. These results are accounted for by the eect of complexing agents and acid catalysts on the size of both TiO 2 and TiN grains and the dierent reactivity of the anatase and rutile phases. The possibility of tailoring the composition and morphology of TiN ®lms by using complexing agents is envisaged. Ó

Thin Solid Films, 1998

Tungsten trioxide films formed of aggregates in the nanometric range have been deposited by therm... more Tungsten trioxide films formed of aggregates in the nanometric range have been deposited by thermal evaporation and condensation method. From the atomic force microscopy study, the aggregate dimensions were found to be in the range between 350 nm and 450 nm. The optical, structural and electrochromic performance of these films under lithium intercalation is studied in detail and their properties are compared to those of continuous films of tungsten trioxide. The films show a slightly elevated diffuse reflectance in the lower wavelength range and a very high transmission in the solar and visible wavelengths. Under lithium intercalation, the films exhibit a very good degree of electrochromic optical modulation in both these spectral ranges and hence, are very suitable for electrochromic device application. The high degree of change between the clear state and the colored state render such nanocrystalline films more efficient in their electrochromic performance than the conventional continuous films. q 1998 Published by Elsevier Science S.A. All rights reserved.

Solid State Ionics, 1993

A study of the lithiation behavior of some transition metal oxides has been carried out. Using a ... more A study of the lithiation behavior of some transition metal oxides has been carried out. Using a dry method of lithiation changes in optical and electrical properties of WOs, Vz05 and Nbz05 films prepared under different conditions are studied. The optimum results and techniques are used for the fabrication of an all-solid electrochromic (EC) system based on the utilization of high coloration efficiency WOs as the base electrochromic layer and the low coloration efficiency VxO, as the counter electrode. LiBO* has been used as the ion conducting layer. Such system has been operated over several hundred optical switching cycles without any degradation so far. All results indicate the suitability of the system for "smart" window application.

Applied Optics, 1995

We propose a method that uses reflection and transmission photoellipsometry to analyze samples co... more We propose a method that uses reflection and transmission photoellipsometry to analyze samples consisting of thin films combined with semitransparent thick layers or substrates in the form of multilayer structures. Athick film or substrate is defined as a layer for which no interference effects can be observed for a given wavelength resolution, and contributions from multiple reflections in the substrate are taken into account in the theoretical treatment. An automatic reflection-transmission spectroscopic ellipsometer was built to test the theory, and satisfactory results have been obtained. Examples corresponding to a strongly absorbing film deposited on a glass substrate and a highly transmitting film also deposited on glass are shown. In both cases a good fit between theory and experiment is found. The photoellipsometric method presented is particularly suited to the analysis of actual samples of energy-efficient coatings for windows.