Speaker: Merve Uslu
Title: Optical and Electrical Properties of Vanadium Oxide based Nanostructures for Thermochromic Smart Materials
Date/Time: February 28, 2018 / 12:40-13:30
Place: FENS G015
Abstract: In recent years. one of the studies that have attracted the interest of researchers is examining the electrical and optical properties of transition metal oxide surface coating. Optical materials with controllable phase change have a wide field of application in technology. Energy efficient electronic devices, smart windows, sensors are some of these application areas.
Vanadium dioxide has attracted widespread interest since the metal-insulator transition (MIT) in 1959s . As is known, VO2 has an insulator monoclinic crystal structure at the low temperature and the energy band gap value is 0.7 eV. The transition temperature of VO2 is 68°C . VO2 thin film shows the characteristic of metallic tetragonal crystal structure at the higher temperature than 68°C. Therefore, VO2 thin film transmits radiation in the infrared spectrum at low temperature, dielectric conditions. When the VO2 thin film is heated up to the 68°C transition temperature, it transmits the light in the visible spectrum and reflects the light in the infrared spectrum. Thus, depending on the temperature, this change in optical properties results in a natural filter with light control.
In this study, VO2 nanostructured film was deposited by e-beam evaporation which is one of the physical vapor deposition (PVD) techniques. The obtained vanadium oxide films were heat treated in Ar gas atmospheres and 700°C temperature conditions. By this method, it is aimed to obtain VO2 nanostructure film with +4 value. The surface morphology, crystal structure and optical properties of the deposited films were analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD) and as a function of ellipsometer techniques respectively. The thermochromic properties of VO2 film samples were investigated by doing temperature dependent reflection measurements with a specially designed temperature control unit.
Contact: Bekir Bediz