EXAFS and IR Analysis of Electrochromic NiO_x/NiO_xH_y Thin Films

Jana Padežnik Gomilšek,¹ Romana Cerc Korošec,² Peter Bukovec² and Alojz Kodre^3,4 

¹ Faculty for Mechanical Engineering, Smetanova 17, SI-2000 Maribor, Slovenia
² Faculty of Chemistry and Chemical Technology, Aškerčeva 5, SI-1000 Ljubljana, Slovenia
³ Faculty of Mathematics and Physics, Jadranska 19, SI-1000 Ljubljana, Slovenia
⁴ Jožef Stefan Institute, Jamova 39, SI-1000 Ljubljana, Slovenia
* Corresponding author: E-mail: jana.padeznik@uni-mb.si

Abstract
Electrochromic (EC) thin films of NiO_x and NiO_xH_y are prepared by sol-gel method from nickel chloride precursor and deposited onto a suitable substrate by dip-coating technique. The development of the structure with thermal treatment is investigated by EXAFS and IR spectroscopy in two series of films, with high and low concentration of chloride as counter ions. In the former, the predominant structure before thermal treatment is nickel hydroxide. The baking induces condensation, yet with no trace of NiO. In the latter group, colloidal particles are indicated, on which acetate groups are adsorbed or coordinated. At the maximum EC-response the formation of NiO grains is established by EXAFS and IR.

Keywords: Electrochromism, thin films, nickel oxide, nickel hydroxide, EXAFS