Electronic and structural properties of ‘smart windows’ and liquids using in-situ X-ray absorption spectroscopy

• Published in: Journal of alloys and compounds Vol. 362; no. 1; pp. 124 - 132
• Main Authors: Nachimuthu, P., Matsuo, S., Farangis, B., Lindle, D.W., Wakita, H., Perera, R.C.C.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Lausanne Elsevier B.V 01-01-2004; Elsevier
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Electron states; Electronic states; Electronic structure of disordered solids; Energy storage materials; Exact sciences and technology; Extended X-ray absorption fine structure (EXAFS); Interactions of particles and radiation with matter; Near-edge X-ray absorption fine structure (NEXAFS); Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Other interactions of matter with particles and radiation; Physics; Synchrotron radiation; Thin films; Thin films; Extended X-ray absorption fine structure (EXAFS); Electronic states; Near-edge X-ray absorption fine structure (NEXAFS); Energy storage materials; Synchrotron radiation; Coordination number; Inorganic compounds; X ray fluorescence; Amorphous alloy; Experimental study; EXAFS; Electronic structure; Aqueous solutions; X-ray absorption spectra; Optical switching; Amorphous state structure
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/S0925-8388(03)00572-3

A new experimental set-up to measure in-situ X-ray absorption spectra under ambient conditions in the 400–2000-eV photon-energy region using both transmission and total-fluorescence-yield detection techniques has been developed, and its utility has been demonstrated by studying optically switchable and amorphous metal thin films (Mg–TM, where TM=Ti, Mn, Co and Ni) in the solid state, as well as Al
3+ and Br
− ions in aqueous solution. The structural and electronic properties of the freshly co-sputtered Mg–TM thin films in metallic and hydride states were investigated by X-ray diffraction and Mg K- and TM L-edge X-ray absorption spectra. The optical switching of Mg–TM thin films from a mirror-like metallic state to an optically transparent state by exposure to 4% H
2 in He is demonstrated by optical transmission and reflectivity in the 350–2500-nm region. The corresponding edge shifts in the Mg K- and TM L-edge X-ray absorption spectra indicate the presence of hydrogen as near neighbors, and its influence on the chemical states of metal thin films is demonstrated using Mg–Ni thin films as a representative example. Aluminum K-edge X-ray absorption spectra in the near-edge region were investigated to study the coordination of Al in crystalline and 0.1 M aqueous solutions of NaAlO
2, Al(NO
3)
3 and Al
2(SO
4)
3. Aluminum in NaAlO
2 occupies both tetrahedral and octahedral sites unlike Al in Al(NO
3)
3 and Al
2(SO
4)
3, where it retains its six-fold coordination irrespective of hydration. Bromine L-edge X-ray absorption spectra for crystalline and 0.1 M aqueous solutions of NaBr, KBr and KBrO
3 were carried out to study the ligand-field splittings of core excitations which depend on inter-atomic distances, dissociation in aqueous solution, and the resulting hydration.