Electrochromic properties of NiO xH y thin films

Abstract

NiO x H y films were prepared by DC magnetron sputtering in H 2/O 2 atmosphere. NiO x H y coatings with transparency and high electrochromic efficiency were obtained by changing H 2 content. A 60 nm thick NiO x H y film with transmittance of 0.57 (as-deposited state), 0.78 (bleached state) and 0.24 (coloured state) at wavelength of 550 nm was deposited in an atmosphere of H 2(60%)+O 2(40%). Analysis of infrared spectra (6000∼2400 cm −1) showed that the absorption peaks for bleached and colored states are associated with free ‘OH’ and OH stretching vibrations, respectively. XPS Ni2p core level spectra of colored NiO x H y film exhibited a peak at 856.2±0.2 eV which is attributed to Ni 3+. Ni2p core level spectra of the bleached and as-deposited films exhibited two peaks at 856.4±0.2 and 854.6±0.2 eV which are attributed to Ni 3+ and Ni 2+.