New thermochromic bilayers for optical or electronic switching systems

Thin films of thermochromic vanadium dioxide (with phase transition at T-c = 68 degreesC) were covered by a cerium dioxide layer. Cerium dioxide was chosen for its chemical stability, infrared optical transparency and strong optical absorption in the ultraviolet range. The optical properties of these bilayers are comparable to optical properties of pure vanadium dioxide films. Vanadium dioxide was first deposited on a silica substrate by radio-frequency reactive sputtering. Later, a ceria thin film was deposited on the vanadium dioxide film by the same technique. The thin films were characterized by X-ray diffraction measurements, atomic force microscopy, scanning electron microscopy, transmission electron microscopy and ellipsometry techniques. Optical transmittance and optical switching efficiency were studied by Fourier transform infrared spectroscopy. (C) 2003 Elsevier B.V. All rights reserved.