INVESTIGATION OF THE TEMPERATURE- AND ELECTRICALLY-INDUCED PHASE TRANSITION IN VANADIUM DIOXIDE BY ELLIPSOMETRY METHODS
K.E. Kapoguzov1,2, V.B. Kalinina1,2, I.A. Azarov1,2, A.E. Gayduk1, V.N. Kichay3, L.V. Yakovkina3, S.V. Mutilin1
1Rzhanov Institute of Semiconductor Physics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, Russia
2Novosibirsk State University, Novosibirsk, Russia
3Nikolaev Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences, Novosibirsk, Russia
Keywords: vanadium dioxide, semiconductor-metal phase transition, ellipsometry, numerical analysis methods, electro-optical switching
Abstract
In this work, we study the temperature- and electrically-induced phase transition in thin vanadium dioxide films by spectral and microellipsometry methods. It is shown that the resistance of the vanadium dioxide 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(λ) and absorption k(λ) indices for the semiconductor and metallic phases of vanadium dioxide are calculated from experimentally determined parameters Ψ and Δ. In the ultraviolet and visible regions of the spectrum, the changes in n and k are found to be 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 the 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 Ψ and Δ is detected by microellipsometry during the electrically initiated formation of a thin conductive filament in vanadium dioxide between two contact pads. The results obtained demonstrate the promise of vanadium dioxide for use in tunable optical and optoelectronic devices in the near and middle infrared ranges.
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