SPECTROSCOPIC LIGHT-SCATTERING FROM ELECTROCHROMIC TUNGSTEN-OXIDE-BASED FILMS

Films of W oxide and oxyfluoride were made by reactive sputtering, and electrochromic absorption modulation was obtained by subsequent elect rochemical Li intercalation. Total and diffuse transmittance and refle ctance were measured in the 0.4-1 mu m wavelength range using a newly developed instrument. The ratio between diffuse and total optical resp onse was <0.2% for the transmittance and <1% for the reflectance irres pective of the electrochromic absorption level. These magnitudes of th e scattering are acceptable for practical smart windows applications a nd lend credence to a description of electrochromism in terms of local ized absorption centers. Vector perturbation theory for light scatteri ng by a film with rough interfaces could be reconciled with the data, assuming uncorrelated roughness. (C) 1996 American Institute of Physic s.