Resistance noise at the metal-insulator transition in thermochromic VO2 films
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2015 AIP Publishing LLC. Thermochromic VO 2 films were prepared by reactive DC magnetron sputtering onto heated sapphire substrates and were used to make 100-nm-thick samples that were 10 m wide and 100 m long. The resistance of these samples changed by a factor 2000 in the 50 < T s < 70 C range of temperature T s around the "critical" temperature T c between a low-temperature semiconducting phase and a high-temperature metallic-like phase of VO 2 . Power density spectra S(f) were extracted for resistance noise around T c and demonstrated unambiguous 1/f behavior. Data on S(10 Hz)/R s2 scaled as R sx , where R s is sample resistance; the noise exponent x was -2.6 for T s < T c and +2.6 for T s > T c . These exponents can be reconciled with the Pennetta-Trefn-Reggiani theory [Pennetta et al., Phys. Rev. Lett. 85, 5238 (2000)] for lattice percolation with switching disorder ensuing from random defect generation and healing in steady state. Our work hence highlights the dynamic features of the percolating semiconducting and metallic-like regions around T c in thermochromic VO 2 films.
