Investigation of the Temperature and Electrically Initiated Phase Transition in Vanadium Dioxide by Ellipsometry Methods

In this work, we have studied temperature- and electrically initiated phase transition in thin vanadium dioxide films by spectral and microellipsometry methods. It is shown that the resistance of the VO ₂ film changes dramatically by more than three orders of magnitude at a temperature of about 67 ^ C, which is associated with the semiconductor–metal phase transition. Using the developed numerical algorithm for solving the inverse ellipsometry problem, the spectral dependences of the refractive n () and absorption k () indices for the semiconductor and metallic phases of vanadium dioxide have been calculated from experimentally determined parameters and. It has been found that in the ultraviolet and visible regions of the spectrum, changes in n and k are insignificant upon heating, whereas in the near-infrared range, there is a sharp redistribution of the optical response associated with the phase transition in vanadium dioxide. It is shown that the greatest changes in refractive and absorption indices occur at a wavelength of 1100 nm and range from 2. 94 to 1. 57 and from 0. 91 to 1. 95, respectively. A reversible change in the parameters and was recorded by microellipsometry during the electrically initiated formation of a thin conductive filament in vanadium dioxide between two contact pads. The results obtained demonstrate that vanadium dioxide is promising for using it in tunable optical and optoelectronic devices in the near and middle infrared ranges.