CROSS-SECTIONAL OBSERVATIONS BY HRTEM OF THE STRUCTURE OF NICKEL OXIDE ELECTROCHROMIC THIN FILMS IN THE AS-DEPOSITED STATE AND THE BLEACHED STATE

Abstract

To investigate the microstructure of nickel oxide electrochromic thin films prepared by reactive DC magnetron sputtering, cross-sectional observations of sputtered nickel oxide films have been performed using a high resolution electron microscope. High resolution images were observed for as-deposited and bleached samples. These images show that the surface morphology of these samples is quite different. The bleached sample consists of needle-like microcrystallites, while the as-deposited sample consists of columnar crystals and has a smooth surface. Diffraction patterns indicate that crystallized NiO is the dominant structure in both samples. The fact that no trace of Ni(OH) 2 was observed implies that the boundary and the surface of NiO microcrystallites play important roles in the electrochromic reaction. © 1997 Elsevier Science Ltd