Non-Gaussian resistance noise behavior across the metal-insulator transition in VO₂ thin films

Vanadium dioxide (VO₂) thin films exhibit a sharp metal-insulator transition (MIT) at a critical temperature ~ 330 K. The significance of a Peierls-type instability or a Mott-Hubbard-type transition near T_c has been a topic of discussion for many years. We present results from a resistance noise spectroscopy study of VO₂ thin films that show that the power spectral density (PSD) of the fluctuations near T_c show a marked deviation from the metallic and insulating phases. The PSD increases by orders of magnitude and deviates from a typical 1/f behavior near T_c. The probability density function (PDF) of the fluctuation is non-Gaussian in nature in thin films near T_c whereas the fluctuations are Gaussian at all temperatures in single crystal nanobeams. Our results suggest that the transition likely occurs as a single domain phenomenon in nanobeams whereas the nucleation and propagation of multiple domains of opposite phase are significant near T_c in thin films. The influence of the coexistence of phases on electrical transport will be discussed based on our analysis of the 1/f behavior, PSD, PDF and the second spectrum of noise.