Fabrication Of Ordered Microstuctured Vanadium Oxide And Research On Its Thermochromism

At room temperature, vanadium dioxide is an insulator material whichundergoes a I-M transition from monoclinic crystalline symmetry to a rutile metallicphase of tetragonal structure with a transition temperature Tc=68℃. The phasetransition is accompanied by abrupt changes in the dielectric constant with hightransparency at the insulator phase but high reflectivity at the metallic phase in thenear infrared wavelength.Vanadium dioxide is an subject of increasing interest in modern optics becauseof its applications in the optical switch, nanoscale structure, thin films and ultrafastdevices. This thesis focuses on the vanadium oxide thin films, the fabrication ofordered micro-structure and thermal induced phase transition.Sol-gel is introduced in preparation of vanadium oxide thin film. Bycomparing the Zeta potential value of two kinds of vanadium pentoxide sol, theauthor could choose the more stable one. Dip-coating and spin-coating are utilizedto form thin films. Then the samples are characterized by SEM, AFM, XRD, XPSand ellipsometry.Study the heat treatment process in order to obtain the vanadium dioxide thinfilm. In the experiment, the author found the optimal means among annealing in air,vacuum, nitrogen and hydrogen.We fabricate the polystyrene colloidal template by self-assembly. Viacomparing different growth conditions with different emulsion concentration, weselect the best preparation process. The template is infilled with vanadium pentoxideby electrochemical deposition. After removed PS spheres in the solution oftetrahydrofuran, the sample annealed in hydrogen and became vanadium dioxide.Measure the transmittance-temperature curve and the resistance-temperaturecurve, and verify the thermal induced phase transition of the sample. Femtosecondlaser white light transient grating experiment provides a new method to study theM-I transition dynamics.