Optical and electrical properties of vanadium oxide films deposited from alkoxides

Vanadium oxide thin films are formed via the hydrolysis and condensation of vanadium alkoxides. Sol-gel chemistry provides a chemical control over con densation reactions and different materials are actually obtained depending on experimental conditions. The hydrolysis of vanadium alkoxide in the pre sence of an excess of water leads to ribbon-like particles of hydrated oxid e V2O5.nH2O. Coatings with a preferred orientation are then deposited from these gels. They exhibit improved electrochemical properties as reversible cathodes for lithium batteries. Amorphous ore-polymers are formed via the p artial hydrolysis of vanadium alkoxides. They allow the deposition of optic ally transparent thin films that could be used in electrochromic display de vices. Moreover, alkoxide derived films can be easily reduced into vanadium dioxide. These VO2 thin films exhibit thermochromic properties. They exhib it the well known metal-insulating transition around 70 degrees C. The tran sition temperature can be modified by doping with other metal cations.