Synthesis of Thin Film Vanadium Oxide (VO2)

Description of the Invention

This project involves refining a synthesis of thin films of solid state Vanadium Oxide (VO2) using sol-gel methods. By precisely controlling the processing conditions, (baking temperature, ambient gas in the oven, baking time, solvent etc.), VO2 films can be synthesized that are highly resistant to oxidation. Current published methods produce sol-gel precursor solutions that readily oxidize in air and lead to the formation of other, less-desirable, vanadium oxide phases. This synthesis produces sol-gel precursor solutions that are resistant to oxidation for months instead of hours.

Background

Thermochromic materials reversibly change their crystalline structure from semiconductor-to-metal as a function of temperature. Among these thermochromic materials, vanadium oxide (VO2) has received the most attention because of its large reversible change in optical properties at relatively low temperatures (≈ 70°C). During its semiconductor-to-metal phase transition, the change in the optical properties of VO2 is marked by an increased reflectivity; furthermore, its electrical and magnetic properties also change. Because of this unusual behaviour, thin films of vanadium dioxide have wide-ranging potential as electrochromic devices such as electrical or optical switches, as optical storage media, as optical limiters to protect against high intensity laser damage, and as a means to passively control the amount of solar thermal loading for windows (“smart windows”).

Potential Uses

• Optical/Temperature switches
• Optical medial storage
• Laser protection as Optical limiters
• Solar energy control as “Smart Windows”

Future work will include:

• Doping agents to reduce the transition temperature
• Application methods
• Mechanical properties i.e. hardness, adhesion
• Control of morphology: by varying the processing conditions, the morphology of the resultant VO2 films can be controlled to produce of nano-belts, nano-ribbons or nano-wires.