Electrochromic properties of Li_x Ni_y O films deposited by RF magnetron sputtering

Electrochromic properties of a series of Li_x Ni_y O films were studied to obtain the films that give a good reversible electrochromic reaction in a nonaqueous electrolyte solution. We paid attention to the lithium content in the films. The films were deposited by radio-frequency (rf) magnetron sputtering with Li_x Ni_y O targets under different conditions. The lithium contents were selected by using three different Li_x Ni_y O targets. NiO pellets were also used for cosputtering with the targets to finely adjust the lithium content in Li_x Ni_y O films. We found that a Li_x Ni _y O film gave a high electrochromic coloration efficiency when the lithium content in the film was adjusted to about 0.2. The X-ray diffraction (XRD) study showed that the crystalline Li₂ Ni8 O10 film yielded good electrochromic performance, and that the (102) XRD peak was dominant in the films.