Raising the metal-insulator transition temperature of VO2 thin films by surface adsorption of organic polar molecules

We report a molecular adsorption effect on the first-order metal-insulator transition of vanadium dioxide (VO2) thin films. The phase transition temperature is shifted higher by the adsorption of particular polar and rigid tripodal molecules on the film surfaces. The shift becomes larger with increasing dipole moment magnitude, which ranges from 0 to 20D. The orientation of polar molecules aligned on the surface is most likely responsible for the higher shift of the transition temperature. Coating the surfaces with polar molecules, as demonstrated in this work, might provide a unique way of controlling the phase transition of materials. (C) 2015 The Japan Society of Applied Physics