Comparative study of the metal insulator transition of a VO2 film with simultaneous infrared thermography and electric measurements

Metal–insulator transition (MIT) of a polycrystalline VO2 film was studied with simultaneous electric resistance and infrared thermographic measurements. The apparent temperatures (Tapp,s) determined from infrared thermography show an obvious thermal hysteresis over the MIT that could match with the electric resistance very well. The dynamic change in the emissivity (ε) over the MIT was obtained from the Tapp,s hysteresis. The MIT parameters, including the critical phase transition temperature, thermal hysteresis width, and transition sharpness, could be obtained from the ε thermal hysteresis, which are in good accordance with those obtained from the electric resistance hysteresis. The temperature coefficient of ε (TCE) was defined, and the TCE change over the MIT was also obtained from ε thermal hysteresis. Based on the effective medium approximation, the fraction of the metallic phase during the MIT was estimated from the ε thermal hysteresis; this is also consistent with that calculated from the electric resistance hysteresis. Our results showed that the infrared thermographic measurement could be a simple and reliable method to study the MIT of VO2 materials.