OPTICAL PROPERTIES OF AMORPHOUS THIN FILMS OF SODIUM-TUNGSTEN OXIDE BRONZES

Abstract

The spectral dependences were measured of the optical density of amorphous thin films of sodium-tungsten oxide bronze of the tetragonal structure and the composition Na0,3WO3, condensed on glass substrates, thermostated at temperatures of 373, 473 and 573K, as well as annealed in air vacuum, and electrochromically colored. The optical density D, which is proportional, as is known, to the absorption coefficient, was chosen as the studied optical characteristic. Spectral measurements of films deposited on substrates in the temperature range of 373, 473 and 573K showed the same type of spectral characteristics, with a peak of the exciton absorption in the near ultraviolet. The band of minimum absorption lies in the wavelength range of 400÷460 nm, while that of the impurity absorption is a wide band in the region of 650÷1000 nm with a maximum in the range of 900÷1000 nm. This spectral characteristic determines the blue-blue color of a thin film in transmission. The study of the optical properties of thin films of sodium-tungsten bronzes is an urgent problem.

Keywords

• sodium tungsten bronze
• thin film
• monocrystal
• electrochromic effect
• optical density
• spectral characteristics