Resistance noise at the metal-insulator transition in thermochromic VO2 films

TL;DR

This study investigates resistance noise in thermochromic VO2 films near the metal-insulator transition, revealing 1/f noise behavior and exponents consistent with percolation theory, shedding light on the dynamic phase coexistence.

Contribution

It provides experimental evidence of resistance noise characteristics and their relation to percolation models in VO2 films during the phase transition.

Findings

Resistance changes by a factor of 2000 around Tc.

Resistance noise exhibits 1/f behavior.

Noise exponents match percolation theory predictions.

Abstract

Thermochromic VO2 films were prepared by reactive DC magnetron sputtering onto heated sapphire substrates and were used to make 100-nm-thick samples that were 10 {\mu}m wide and 100 micron long. The resistance of these samples changed by a factor of about 2000 in the 50 < Ts < 70 C range of temperature Ts around the "critical" temperature Tc between a low-temperature semiconducting phase and a high-temperature metallic-like phase of VO2. Power density spectra S(f) were extracted for resistance noise around Tc and demonstrated unambiguous 1/f behavior. Data on S(10Hz)/Rs^2 scaled as Rs^x, where Rs is sample resistance; the noise exponent x was -2.6 for Ts < Tc and +2.6 for Ts > Tc. These exponents can be reconciled with the Pennetta-Trefan-Reggiani theory [C. Pennetta, G. Trefanan, and L. Reggiani, 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 Tc in thermochromic VO2 films.