Belmont SURFS

Synthesis of Vanadium Dioxide Thin Films using Sol-Gels

Vanadium dioxide (VO2) thin films have promising applications in smart window technology for energy conservation and optical switches due to its semiconducting-to-metal phase transition at near room temperature. These films are usually fabricated using either a vapor deposition method or through chemical synthesis using one of several sol-gel methods. The latter has received much attention because of its scalability and low cost. Generally, sol-gel synthesis of VO2 consists of creating a precursor solution containing a vanadium oxide compound in a solvent, coating a substrate with the solution, drying the solution to form a VOx-thin film, and annealing the film to achieve the desired VO2 structure and stoichiometry. Our research has focused on fabricating cost-effective VO2-thin films using two different precursor solutions common to the literature. First, vanadium(V) pentoxide (V2O5) was dissolved in distilled water, oxalic acid, and polyvinyl alcohol at 80oC and aged for 24 hours. In the second solution, vanadium(IV)-oxy acetylacetonate (VO(acac)2) was dissolved in methanol and aged for one week. Each precursor was synthesized, spin-coated, dried, and annealed based on methods described in the literature, with spin-coating, drying, and annealing tested with a range of values and conditions. Each film was characterized using VIS-NIR transmission spectroscopy at room temperature and at ~100oC with the goal of determining if VO2 was present in the annealed films and which methodology gives the highest quality film.