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 μm wide and 100 μm 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-Trefán-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.
author list (cited authors)
Topalian, Z., Li, S., Niklasson, G. A., Granqvist, C. G., & Kish, L. B.